From 5007132759c49205e15850d5c355822541079550 Mon Sep 17 00:00:00 2001
From: Michael Arnaldi <michael.arnaldi@effectful.co>
Date: Tue, 7 Oct 2025 10:42:04 +0200
Subject: [PATCH 01/20] add comprehensive Queue/TxQueue API alignment plan

- Create unified Cause.Done completion type
- Remove Queue.done() operation, adopt failCause as primitive
- Fix TxQueue takeAll to return NonEmptyArray
- Add Queue.interrupt for graceful close and align clear semantics
- Add Queue.Enqueue interface for type-safe producer patterns
- Document all breaking changes with migration paths
- Include 4-phase implementation plan with validation checklist
---
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+# API Alignment Plan: Queue.ts vs TxQueue.ts
+
+**Goal:** Align the APIs of Queue.ts (Effect-based) and TxQueue.ts (STM-based) to ensure consistent naming, return types, functionality, and structure while respecting their fundamental differences.
+
+## Overview
+
+Queue.ts provides Effect-based asynchronous queues with backpressure strategies, while TxQueue.ts provides STM-based transactional queues. As TxQueue is the transactional counterpart of Queue, the APIs should mirror each other closely.
+
+**Key Differences to Preserve:**
+- **Queue.ts**: Effect-based, supports unsafe synchronous operations
+- **TxQueue.ts**: STM-based, all operations are atomic transactions (no unsafe variants needed)
+
+## Critical Issues Identified
+
+### 1. ❌ WRONG: Inconsistent Completion Semantics (HIGHEST PRIORITY)
+
+**Current State:**
+- Queue.ts uses local `Done` interface (lines 968-992)
+- TxQueue.ts uses `Cause.NoSuchElementError`
+- Both represent the same concept: graceful queue completion
+
+**Why This is Wrong:**
+- `NoSuchElementError` implies "element not found" (lookup failure)
+- Queue completion means "gracefully finished, no more items" (lifecycle event)
+- Different types for same semantic meaning = API confusion
+
+**Solution:**
+- Create unified `Cause.Done` error type in Cause.ts
+- Both queues use `Cause.Done` for completion semantics
+- Remove Queue's local `Done` interface
+- Migrate TxQueue from `Cause.NoSuchElementError` to `Cause.Done`
+
+### 2. ❌ WRONG: Queue's `done()` Operation (HIGH PRIORITY)
+
+**Current State:**
+```typescript
+// Queue.ts - Complex signature with Exit
+export const done = <A, E>(
+  self: Queue<A, E>, 
+  exit: Exit<Done extends E ? unknown : never, E>
+): Effect<boolean>
+```
+
+**Why This is Wrong:**
+- Complex conditional type signature
+- Takes `Exit` instead of `Cause` (less natural)
+- Not present in TxQueue (inconsistency)
+- `Cause` is the natural primitive, not `Exit`
+
+**TxQueue's Better Approach:**
+```typescript
+// TxQueue.ts - Clean signatures
+export const fail: <A, E>(self: TxEnqueue<A, E>, error: E) => Effect<boolean>
+export const failCause: <A, E>(self: TxEnqueue<A, E>, cause: Cause<E>) => Effect<boolean>
+export const end: <A, E>(self: TxEnqueue<A, E | Cause.Done>) => Effect<boolean>
+```
+
+**Solution:**
+- Remove `done()` and `doneUnsafe()` from Queue.ts
+- Make `failCause(cause: Cause<E>)` the primitive in both implementations
+- Build `fail` and `end` as convenience wrappers around `failCause`
+- Hierarchy: `failCause` → `fail`, `end`
+
+### 3. ❌ WRONG: TxQueue `takeAll` Type Lie (HIGH PRIORITY)
+
+**Current State:**
+```typescript
+// TxQueue.ts - Says "might be empty" but blocks until non-empty!
+export const takeAll = <A, E>(self: TxDequeue<A, E>): Effect<ReadonlyArray<A>, E>
+```
+
+**Implementation Reality:**
+```typescript
+// Blocks until at least 1 item available
+if (yield* isEmpty(self)) {
+  return yield* Effect.retryTransaction  // ← BLOCKS HERE
+}
+// Only proceeds when ≥1 item available
+```
+
+**Queue.ts Has it Correct:**
+```typescript
+export const takeAll = <A, E>(self: Dequeue<A, E>): Effect<NonEmptyArray<A>, E>
+```
+
+**Solution:**
+- Fix TxQueue `takeAll` signature to return `NonEmptyArray<A>`
+- Type now accurately reflects runtime behavior
+
+### 4. ❌ WRONG: Queue Missing `interrupt` Operation (HIGH PRIORITY)
+
+**Current State:**
+- Queue.ts has NO `interrupt` operation
+- Only has `shutdown` which clears AND interrupts immediately
+- No way to gracefully close (stop accepting, allow draining)
+
+**TxQueue.ts Has it:**
+```typescript
+export const interrupt = <A, E>(self: TxEnqueue<A, E>): Effect<boolean>
+  // Graceful close - stops accepting, allows draining existing items
+```
+
+**Solution:**
+- Add `interrupt` to Queue.ts
+- Refactor `shutdown` to compose `clear` + `interrupt`
+
+### 5. ❌ WRONG: Inconsistent `clear` Semantics (MEDIUM PRIORITY)
+
+**Current State:**
+```typescript
+// Queue.ts - Returns Array<A>, category "taking"
+export const clear = <A, E>(self: Dequeue<A, E>): Effect<Array<A>, E>
+
+// TxQueue.ts - Returns void, category "combinators"
+export const clear = <A, E>(self: TxEnqueue<A, E>): Effect<void>
+```
+
+**Solution:**
+- Align both to return `Array<A>` (observable operations)
+- Fix Queue's category from "taking" to "combinators"
+- Change TxQueue to return cleared items
+
+### 6. ❌ WRONG: Queue Missing `Enqueue` Interface (MEDIUM PRIORITY)
+
+**Current State:**
+```typescript
+// TxQueue.ts - THREE interfaces (correct structure)
+TxEnqueue<in A, in E>  // Write-only (contravariant)
+TxDequeue<out A, out E>  // Read-only (covariant)
+TxQueue<in out A, in out E>  // Full queue (invariant)
+
+// Queue.ts - TWO interfaces (incomplete)
+Dequeue<out A, out E>  // Read-only
+Queue<in out A, in out E>  // Full queue
+// MISSING: Enqueue<in A, in E>
+```
+
+**Solution:**
+- Add `Enqueue<in A, in E>` interface to Queue.ts
+- Update `Queue` to extend both `Enqueue` and `Dequeue`
+- Add `isEnqueue` guard and `asEnqueue` converter
+- Enables type-safe producer-consumer patterns
+
+### 7. ❌ WRONG: Return Type Inconsistencies (MEDIUM PRIORITY)
+
+**Issue 7a: `offerAll` returns different types**
+- Queue.ts: `Effect<Array<A>>` (remaining messages)
+- TxQueue.ts: `Effect<Chunk<A>>` (rejected items)
+- **Solution:** Both return `Array<A>`
+
+**Issue 7b: Signature patterns need unified `Cause.Done`**
+- All `E | Done` → `E | Cause.Done`
+- All `Exclude<E, Done>` → `Exclude<E, Cause.Done>`
+- All `E | Cause.NoSuchElementError` → `E | Cause.Done`
+
+## Implementation Plan
+
+### Phase 0: Unified Completion API (HIGHEST PRIORITY)
+
+#### Step 1: Create `Cause.Done` Error Type
+**File:** `packages/effect/src/Cause.ts` + `packages/effect/src/internal/core.ts`
+
+```typescript
+/**
+ * Type identifier for Done errors.
+ * @since 4.0.0
+ * @category symbols
+ */
+export const DoneTypeId: "~effect/Cause/Done" = "~effect/Cause/Done" as const
+
+/**
+ * Represents a graceful completion signal for queues and streams.
+ * 
+ * `Done` is used to signal that a queue or stream has completed normally
+ * and no more elements will be produced. This is distinct from an error
+ * or interruption - it represents successful completion.
+ *
+ * @example
+ * ```ts
+ * import { Cause, Effect } from "effect"
+ * import { Queue } from "effect"
+ *
+ * const program = Effect.gen(function*() {
+ *   const queue = yield* Queue.bounded<number, Cause.Done>(10)
+ *   
+ *   yield* Queue.offer(queue, 1)
+ *   yield* Queue.offer(queue, 2)
+ *   
+ *   // Signal completion
+ *   yield* Queue.end(queue)
+ *   
+ *   // Taking from ended queue fails with Done
+ *   const result = yield* Effect.flip(Queue.take(queue))
+ *   console.log(Cause.isDone(result)) // true
+ * })
+ * ```
+ *
+ * @since 4.0.0
+ * @category models
+ */
+export interface Done extends YieldableError {
+  readonly [DoneTypeId]: typeof DoneTypeId
+  readonly _tag: "Done"
+}
+
+/**
+ * Creates a `Done` error to signal graceful completion.
+ * @since 4.0.0
+ * @category constructors
+ */
+export const Done: new() => Done
+
+/**
+ * Tests if a value is a `Done` error.
+ * @since 4.0.0
+ * @category guards
+ */
+export const isDone: (u: unknown) => u is Done
+```
+
+#### Step 2: Remove Queue's `done()` Operations
+**File:** `packages/effect/src/Queue.ts`
+
+**DELETE:**
+- Line ~816: `done()` operation
+- Line ~850: `doneUnsafe()` operation
+
+**REFACTOR:**
+```typescript
+// Change fail and end to call failCause directly
+export const fail = <A, E>(self: Queue<A, E>, error: E): Effect<boolean> =>
+  failCause(self, Cause.fail(error))
+
+export const end = <A, E>(self: Queue<A, E | Cause.Done>): Effect<boolean> =>
+  failCause(self, Cause.fail(new Cause.Done()))
+```
+
+#### Step 3: Migrate Queue.ts Signatures to `Cause.Done`
+**File:** `packages/effect/src/Queue.ts`
+
+**Update locations:**
+- Line 750: `end` signature
+- Line 783: `endUnsafe` signature  
+- Line 968-992: **DELETE** local `Done` interface, `isDone`, `filterDone`
+- Line 1040: `collect` signature (both patterns)
+- Line 1244-1245: `await_` signature
+- Line 1434-1446: `into` signatures
+- Line 1476: `toPull` signature (both patterns)
+- Line 1499-1500: `toPullArray` signature
+
+**Search/Replace patterns:**
+```typescript
+E | Done                    →    E | Cause.Done
+Exclude<E, Done>            →    Exclude<E, Cause.Done>
+```
+
+**Add import:**
+```typescript
+import { Done } from "./Cause.ts"
+```
+
+#### Step 4: Migrate TxQueue.ts from `NoSuchElementError` to `Cause.Done`
+**File:** `packages/effect/src/stm/TxQueue.ts`
+
+**Update locations:**
+- Line 208-211: JSDoc example in `TxEnqueue` interface
+- Line 1273-1308: `end` function signature + implementation
+- Line 1287: Example type annotation
+- Line 1295-1300: JSDoc examples with `isNoSuchElementError`
+
+**Search/Replace patterns:**
+```typescript
+E | Cause.NoSuchElementError       →    E | Cause.Done
+Exclude<E, Cause.NoSuchElementError> →  Exclude<E, Cause.Done>
+Cause.NoSuchElementError           →    Cause.Done
+Cause.isNoSuchElementError         →    Cause.isDone
+new Cause.NoSuchElementError()     →    new Cause.Done()
+```
+
+#### Step 5: Add `interrupt` to Queue.ts
+**File:** `packages/effect/src/Queue.ts`
+
+```typescript
+/**
+ * Interrupts the queue, transitioning it to a closing state.
+ * Existing items can still be consumed, but no new items will be accepted.
+ *
+ * @example
+ * ```ts
+ * import { Effect } from "effect"
+ * import { Queue } from "effect"
+ *
+ * const program = Effect.gen(function*() {
+ *   const queue = yield* Queue.bounded<number>(10)
+ *   yield* Queue.offer(queue, 1)
+ *   yield* Queue.offer(queue, 2)
+ *
+ *   // Gracefully close - no more offers, but can drain
+ *   yield* Queue.interrupt(queue)
+ *
+ *   // Can still take existing items
+ *   const item = yield* Queue.take(queue)
+ *   console.log(item) // 1
+ * })
+ * ```
+ *
+ * @category completion
+ * @since 4.0.0
+ */
+export const interrupt = <A, E>(self: Queue<A, E>): Effect<boolean> =>
+  Effect.withFiber((fiber) => failCause(self, Cause.interrupt(fiber.id)))
+```
+
+#### Step 6: Fix `clear` Semantics
+**File:** `packages/effect/src/Queue.ts`
+
+```typescript
+// Change category annotation
+// @category combinators  (was: taking)
+export const clear = <A, E>(self: Dequeue<A, E>): Effect<Array<A>, E>
+```
+
+**File:** `packages/effect/src/stm/TxQueue.ts`
+
+```typescript
+// Change to return Array<A> instead of void
+export const clear = <A, E>(self: TxEnqueue<A, E>): Effect.Effect<Array<A>> =>
+  Effect.atomic(
+    Effect.gen(function*() {
+      const chunk = yield* TxChunk.get(self.items)
+      const items = Chunk.toArray(chunk)
+      yield* TxChunk.set(self.items, Chunk.empty())
+      return items
+    })
+  )
+```
+
+#### Step 7: Refactor `shutdown` Composition
+**File:** `packages/effect/src/Queue.ts`
+
+```typescript
+export const shutdown = <A, E>(self: Queue<A, E>): Effect<boolean> =>
+  Effect.gen(function*() {
+    yield* clear(self)        // Clear items first
+    return yield* interrupt(self)  // Then interrupt
+  })
+```
+
+### Phase 1: Interface Structure Alignment
+
+#### Step 1: Add `Enqueue` Interface to Queue.ts
+**File:** `packages/effect/src/Queue.ts`
+
+```typescript
+const EnqueueTypeId = "~effect/Queue/Enqueue"
+
+/**
+ * An `Enqueue` represents the write-only interface of a queue.
+ *
+ * @example
+ * ```ts
+ * import { Effect } from "effect"
+ * import { Queue } from "effect"
+ *
+ * const producer = (enqueue: Queue.Enqueue<number>) =>
+ *   Effect.gen(function*() {
+ *     yield* Queue.offer(enqueue, 1)
+ *     yield* Queue.offerAll(enqueue, [2, 3, 4])
+ *   })
+ * ```
+ *
+ * @since 4.0.0
+ * @category models
+ */
+export interface Enqueue<in A, in E = never> extends Inspectable {
+  readonly [EnqueueTypeId]: Enqueue.Variance<A, E>
+  readonly strategy: "suspend" | "dropping" | "sliding"
+  readonly scheduler: Scheduler
+  capacity: number
+  messages: MutableList.MutableList<any>
+  state: Queue.State<any, any>
+  scheduleRunning: boolean
+}
+
+export declare namespace Enqueue {
+  export interface Variance<A, E> {
+    _A: Types.Contravariant<A>
+    _E: Types.Contravariant<E>
+  }
+}
+
+/**
+ * Type guard to check if a value is an Enqueue.
+ * @since 4.0.0
+ * @category guards
+ */
+export const isEnqueue = <A = unknown, E = unknown>(
+  u: unknown
+): u is Enqueue<A, E> => hasProperty(u, EnqueueTypeId)
+
+/**
+ * Convert a Queue to an Enqueue, allowing only write operations.
+ * @since 4.0.0
+ * @category conversions
+ */
+export const asEnqueue: <A, E>(self: Queue<A, E>) => Enqueue<A, E> = identity
+```
+
+#### Step 2: Update Queue Interface
+**File:** `packages/effect/src/Queue.ts`
+
+```typescript
+// Change from:
+export interface Queue<in out A, in out E = never> extends Dequeue<A, E>
+
+// To:
+export interface Queue<in out A, in out E = never> 
+  extends Enqueue<A, E>, Dequeue<A, E>
+```
+
+#### Step 3: Update Proto
+```typescript
+const QueueProto = {
+  [TypeId]: variance,
+  [DequeueTypeId]: variance,
+  [EnqueueTypeId]: variance,  // ADD THIS
+  ...PipeInspectableProto,
+  // ...
+}
+```
+
+### Phase 2: Critical Return Type Fixes
+
+#### Step 1: Fix TxQueue `takeAll` Return Type
+**File:** `packages/effect/src/stm/TxQueue.ts`
+
+```typescript
+// Change from:
+export const takeAll = <A, E>(self: TxDequeue<A, E>): Effect.Effect<ReadonlyArray<A>, E>
+
+// To:
+export const takeAll = <A, E>(self: TxDequeue<A, E>): Effect.Effect<Arr.NonEmptyArray<A>, E>
+```
+
+#### Step 2: Align `offerAll` Return Type
+**File:** `packages/effect/src/stm/TxQueue.ts`
+
+```typescript
+// Change from:
+export const offerAll = <A, E>(
+  self: TxEnqueue<A, E>, 
+  values: Iterable<A>
+): Effect.Effect<Chunk.Chunk<A>>
+
+// To:
+export const offerAll = <A, E>(
+  self: TxEnqueue<A, E>, 
+  values: Iterable<A>
+): Effect.Effect<Array<A>>
+
+// Update implementation to return Array instead of Chunk
+```
+
+### Phase 3: Missing Operations
+
+#### Add to Queue.ts:
+- `poll` - non-blocking take (returns `Option<A>`)
+- `peek` - inspect without removing
+
+#### Add to TxQueue.ts:
+- `collect` - take all until done/error
+
+### Phase 4: Documentation & Validation
+
+1. Update all JSDoc examples to use `Cause.Done`
+2. Update test files for both modules
+3. Run validation:
+   - `pnpm lint --fix` on modified files
+   - `pnpm check` for type errors
+   - `pnpm docgen` for example compilation
+   - `pnpm test` for all tests
+
+## Breaking Changes Summary
+
+### Breaking Change #1: Unified Completion Type
+```typescript
+// Before
+Queue<number, Queue.Done>
+TxQueue<number, Cause.NoSuchElementError>
+
+// After (both identical)
+Queue<number, Cause.Done>
+TxQueue<number, Cause.Done>
+```
+
+**Migration:**
+```typescript
+// Queue users: Change imports
+import { Queue } from "effect"
+// Remove: import type { Done } from "effect/Queue"
+import { Cause } from "effect"
+
+// Type annotations
+const queue: Queue<number, Queue.Done>  // Before
+const queue: Queue<number, Cause.Done>  // After
+
+// TxQueue users: Similar change
+const queue: TxQueue<number, Cause.NoSuchElementError>  // Before
+const queue: TxQueue<number, Cause.Done>  // After
+```
+
+### Breaking Change #2: Remove `Queue.done()` Operation
+```typescript
+// Before
+yield* Queue.done(queue, Exit.fail(error))
+yield* Queue.done(queue, Exit.succeed(undefined))
+
+// After
+yield* Queue.failCause(queue, Cause.fail(error))
+yield* Queue.end(queue)  // For graceful completion
+```
+
+**Migration:**
+- Replace `Queue.done(queue, Exit.fail(e))` with `Queue.failCause(queue, Cause.fail(e))`
+- Replace `Queue.done(queue, Exit.succeed())` with `Queue.end(queue)`
+- No `doneUnsafe` equivalent - use `failCauseUnsafe` or `endUnsafe`
+
+### Breaking Change #3: `takeAll` Return Type
+```typescript
+// Before (TxQueue)
+const items: ReadonlyArray<number> = yield* TxQueue.takeAll(queue)
+if (items.length > 0) { ... }  // Unnecessary check!
+
+// After (TxQueue)
+const items: NonEmptyArray<number> = yield* TxQueue.takeAll(queue)
+// Guaranteed non-empty, no check needed!
+```
+
+### Breaking Change #4: `clear` Return Type
+```typescript
+// Before (TxQueue)
+yield* TxQueue.clear(queue)  // Returns void
+
+// After (TxQueue)
+const cleared = yield* TxQueue.clear(queue)  // Returns Array<A>
+console.log("Cleared items:", cleared)
+```
+
+### Breaking Change #5: Queue Interface Structure
+```typescript
+// Before
+Queue extends Dequeue  // Only two interfaces
+
+// After
+Queue extends Enqueue, Dequeue  // Three interfaces
+
+// New capabilities
+const enqueue: Queue.Enqueue<number> = queue  // Write-only
+const dequeue: Queue.Dequeue<number> = queue  // Read-only (existing)
+```
+
+**Note:** This is mostly non-breaking as existing code continues to work. Only affects advanced type-level programming.
+
+## Validation Checklist
+
+After implementation, verify:
+
+1. ✅ **No local Done types** - `grep "interface Done" Queue.ts` returns nothing
+2. ✅ **No NoSuchElementError in queues** - `grep "NoSuchElementError" Queue.ts TxQueue.ts` returns nothing
+3. ✅ **All Exclude patterns updated** - `grep "Exclude<E, Done>" Queue.ts` returns nothing without `Cause.`
+4. ✅ **Consistent imports** - Both files import `Done` from `./Cause.ts`
+5. ✅ **Tests pass** - `pnpm test Queue.test.ts TxQueue.test.ts`
+6. ✅ **Types check** - `pnpm check`
+7. ✅ **Examples compile** - `pnpm docgen`
+8. ✅ **Both return NonEmptyArray** - `takeAll` signatures match
+9. ✅ **Both return Array** - `offerAll` and `clear` signatures match
+10. ✅ **Both have interrupt** - Queue and TxQueue have graceful close
+11. ✅ **Both have Enqueue** - Three-interface structure matches
+
+## Success Criteria
+
+- ✅ `Cause.Done` exists and is used by both queues
+- ✅ Queue's local `Done` type removed
+- ✅ TxQueue uses `Cause.Done` (not `NoSuchElementError`)
+- ✅ Queue's `done()` operation removed
+- ✅ Both queues have `fail`, `failCause`, `end` as completion API
+- ✅ Both queues have `interrupt` for graceful close
+- ✅ `takeAll` returns `NonEmptyArray<A>` in both queues
+- ✅ `offerAll` returns `Array<A>` in both queues
+- ✅ `clear` returns `Array<A>` in both queues
+- ✅ Both queues have `Enqueue`, `Dequeue`, `Queue` interfaces
+- ✅ All signatures use consistent completion types
+- ✅ All tests pass
+- ✅ `pnpm docgen` succeeds
+- ✅ `pnpm check` succeeds
+
+## Rationale
+
+### Why `Cause.Done` Over `NoSuchElementError`?
+- **Semantic correctness**: Completion is not "not finding something"
+- **Consistency**: Same concept = same type
+- **Clarity**: `Done` clearly signals "finished normally"
+
+### Why Remove `Queue.done()`?
+- **Simpler API**: `failCause` is more natural than `done(Exit<...>)`
+- **Consistency**: TxQueue doesn't have it, shouldn't be different
+- **Power**: `Cause<E>` can represent ANY completion scenario
+- **Type safety**: Clearer signature without complex conditional types
+
+### Why `takeAll` Returns `NonEmptyArray`?
+- **Type honesty**: Implementation blocks until ≥1 item available
+- **User benefit**: No unnecessary empty checks
+- **Correctness**: Type reflects runtime behavior
+
+### Why Add `Enqueue` Interface?
+- **Type safety**: Restrict operations at type level
+- **Consistency**: Match TxQueue's structure
+- **Patterns**: Enable producer-consumer separation
+- **Variance**: Proper contravariant producer type
+
+### Why `clear` Returns `Array<A>`?
+- **Observability**: See what was cleared (useful for debugging)
+- **Consistency**: Both queues behave the same
+- **Less breaking**: Queue already has this signature

From 084809699d20da9639bf36de154948b6392080e2 Mon Sep 17 00:00:00 2001
From: Michael Arnaldi <michael.arnaldi@effectful.co>
Date: Tue, 7 Oct 2025 11:24:12 +0200
Subject: [PATCH 02/20] docs(PLAN): add detailed implementation steps with
 commit messages

---
 PLAN.md | 241 +++++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 202 insertions(+), 39 deletions(-)

diff --git a/PLAN.md b/PLAN.md
index e13b535ed..00bd30138 100644
--- a/PLAN.md
+++ b/PLAN.md
@@ -7,6 +7,7 @@
 Queue.ts provides Effect-based asynchronous queues with backpressure strategies, while TxQueue.ts provides STM-based transactional queues. As TxQueue is the transactional counterpart of Queue, the APIs should mirror each other closely.
 
 **Key Differences to Preserve:**
+
 - **Queue.ts**: Effect-based, supports unsafe synchronous operations
 - **TxQueue.ts**: STM-based, all operations are atomic transactions (no unsafe variants needed)
 
@@ -15,16 +16,19 @@ Queue.ts provides Effect-based asynchronous queues with backpressure strategies,
 ### 1. ❌ WRONG: Inconsistent Completion Semantics (HIGHEST PRIORITY)
 
 **Current State:**
+
 - Queue.ts uses local `Done` interface (lines 968-992)
 - TxQueue.ts uses `Cause.NoSuchElementError`
 - Both represent the same concept: graceful queue completion
 
 **Why This is Wrong:**
+
 - `NoSuchElementError` implies "element not found" (lookup failure)
 - Queue completion means "gracefully finished, no more items" (lifecycle event)
 - Different types for same semantic meaning = API confusion
 
 **Solution:**
+
 - Create unified `Cause.Done` error type in Cause.ts
 - Both queues use `Cause.Done` for completion semantics
 - Remove Queue's local `Done` interface
@@ -33,21 +37,24 @@ Queue.ts provides Effect-based asynchronous queues with backpressure strategies,
 ### 2. ❌ WRONG: Queue's `done()` Operation (HIGH PRIORITY)
 
 **Current State:**
+
 ```typescript
 // Queue.ts - Complex signature with Exit
 export const done = <A, E>(
-  self: Queue<A, E>, 
+  self: Queue<A, E>,
   exit: Exit<Done extends E ? unknown : never, E>
 ): Effect<boolean>
 ```
 
 **Why This is Wrong:**
+
 - Complex conditional type signature
 - Takes `Exit` instead of `Cause` (less natural)
 - Not present in TxQueue (inconsistency)
 - `Cause` is the natural primitive, not `Exit`
 
 **TxQueue's Better Approach:**
+
 ```typescript
 // TxQueue.ts - Clean signatures
 export const fail: <A, E>(self: TxEnqueue<A, E>, error: E) => Effect<boolean>
@@ -56,6 +63,7 @@ export const end: <A, E>(self: TxEnqueue<A, E | Cause.Done>) => Effect<boolean>
 ```
 
 **Solution:**
+
 - Remove `done()` and `doneUnsafe()` from Queue.ts
 - Make `failCause(cause: Cause<E>)` the primitive in both implementations
 - Build `fail` and `end` as convenience wrappers around `failCause`
@@ -64,49 +72,57 @@ export const end: <A, E>(self: TxEnqueue<A, E | Cause.Done>) => Effect<boolean>
 ### 3. ❌ WRONG: TxQueue `takeAll` Type Lie (HIGH PRIORITY)
 
 **Current State:**
+
 ```typescript
 // TxQueue.ts - Says "might be empty" but blocks until non-empty!
 export const takeAll = <A, E>(self: TxDequeue<A, E>): Effect<ReadonlyArray<A>, E>
 ```
 
 **Implementation Reality:**
+
 ```typescript
 // Blocks until at least 1 item available
-if (yield* isEmpty(self)) {
-  return yield* Effect.retryTransaction  // ← BLOCKS HERE
+if (yield * isEmpty(self)) {
+  return yield * Effect.retryTransaction // ← BLOCKS HERE
 }
 // Only proceeds when ≥1 item available
 ```
 
 **Queue.ts Has it Correct:**
+
 ```typescript
 export const takeAll = <A, E>(self: Dequeue<A, E>): Effect<NonEmptyArray<A>, E>
 ```
 
 **Solution:**
+
 - Fix TxQueue `takeAll` signature to return `NonEmptyArray<A>`
 - Type now accurately reflects runtime behavior
 
 ### 4. ❌ WRONG: Queue Missing `interrupt` Operation (HIGH PRIORITY)
 
 **Current State:**
+
 - Queue.ts has NO `interrupt` operation
 - Only has `shutdown` which clears AND interrupts immediately
 - No way to gracefully close (stop accepting, allow draining)
 
 **TxQueue.ts Has it:**
+
 ```typescript
 export const interrupt = <A, E>(self: TxEnqueue<A, E>): Effect<boolean>
   // Graceful close - stops accepting, allows draining existing items
 ```
 
 **Solution:**
+
 - Add `interrupt` to Queue.ts
 - Refactor `shutdown` to compose `clear` + `interrupt`
 
 ### 5. ❌ WRONG: Inconsistent `clear` Semantics (MEDIUM PRIORITY)
 
 **Current State:**
+
 ```typescript
 // Queue.ts - Returns Array<A>, category "taking"
 export const clear = <A, E>(self: Dequeue<A, E>): Effect<Array<A>, E>
@@ -116,6 +132,7 @@ export const clear = <A, E>(self: TxEnqueue<A, E>): Effect<void>
 ```
 
 **Solution:**
+
 - Align both to return `Array<A>` (observable operations)
 - Fix Queue's category from "taking" to "combinators"
 - Change TxQueue to return cleared items
@@ -123,6 +140,7 @@ export const clear = <A, E>(self: TxEnqueue<A, E>): Effect<void>
 ### 6. ❌ WRONG: Queue Missing `Enqueue` Interface (MEDIUM PRIORITY)
 
 **Current State:**
+
 ```typescript
 // TxQueue.ts - THREE interfaces (correct structure)
 TxEnqueue<in A, in E>  // Write-only (contravariant)
@@ -136,6 +154,7 @@ Queue<in out A, in out E>  // Full queue
 ```
 
 **Solution:**
+
 - Add `Enqueue<in A, in E>` interface to Queue.ts
 - Update `Queue` to extend both `Enqueue` and `Dequeue`
 - Add `isEnqueue` guard and `asEnqueue` converter
@@ -144,23 +163,138 @@ Queue<in out A, in out E>  // Full queue
 ### 7. ❌ WRONG: Return Type Inconsistencies (MEDIUM PRIORITY)
 
 **Issue 7a: `offerAll` returns different types**
+
 - Queue.ts: `Effect<Array<A>>` (remaining messages)
 - TxQueue.ts: `Effect<Chunk<A>>` (rejected items)
 - **Solution:** Both return `Array<A>`
 
 **Issue 7b: Signature patterns need unified `Cause.Done`**
+
 - All `E | Done` → `E | Cause.Done`
 - All `Exclude<E, Done>` → `Exclude<E, Cause.Done>`
 - All `E | Cause.NoSuchElementError` → `E | Cause.Done`
 
+## Detailed Implementation Steps with Commits
+
+### Phase 0: Unified Completion API (HIGHEST PRIORITY)
+
+**Commit 0.1:** `feat(Cause): add Done error type for queue completion`
+
+- Add `Done` class extending `Pull.Halt<void>` to `packages/effect/src/internal/core.ts`
+- Export `Done`, `DoneTypeId`, `isDone` from `packages/effect/src/Cause.ts`
+- Validates: `pnpm lint --fix`, `pnpm tsc --noEmit`
+
+**Commit 0.2:** `refactor(Queue): migrate to use Cause.Done for completion`
+
+- Replace all `E | Done` with `E | Cause.Done` in Queue.ts
+- Replace all `Exclude<E, Done>` with `Exclude<E, Cause.Done>`
+- Update `end`, `endUnsafe`, `collect`, `await_`, `into`, `toPull`, `toPullArray` signatures
+- Deprecate local `Queue.Done`, re-export `Cause.Done` as `Queue.Done` for compatibility
+- Update JSDoc examples to use `Cause.Done`
+- Validates: `pnpm lint --fix`, `pnpm tsc --noEmit`, `pnpm test packages/effect/test/Queue.test.ts`
+
+**Commit 0.3:** `refactor(TxQueue): migrate from NoSuchElementError to Cause.Done`
+
+- Replace all `Cause.NoSuchElementError` with `Cause.Done`
+- Update `end()` signature and implementation
+- Update all JSDoc examples
+- Validates: `pnpm lint --fix`, `pnpm tsc --noEmit`, `pnpm test packages/effect/test/TxQueue.test.ts`
+
+**Commit 0.4:** `feat(Queue): add interrupt operation for graceful close`
+
+- Add `interrupt()` function to Queue.ts
+- Add JSDoc with examples
+- Validates: `pnpm lint --fix`, `pnpm tsc --noEmit`, `pnpm test packages/effect/test/Queue.test.ts`
+
+**Commit 0.5:** `refactor(Queue): fix clear semantics to return cleared items`
+
+- Change `clear()` category from "taking" to "combinators"
+- Validates: `pnpm lint --fix`, `pnpm tsc --noEmit`
+
+**Commit 0.6:** `refactor(TxQueue): change clear to return cleared items`
+
+- Update `clear()` to return `Array<A>` instead of `void`
+- Update implementation
+- Validates: `pnpm lint --fix`, `pnpm tsc --noEmit`, `pnpm test packages/effect/test/TxQueue.test.ts`
+
+**Commit 0.7:** `refactor(Queue): refactor shutdown to compose clear + interrupt`
+
+- Change `shutdown()` implementation to call `clear()` then `interrupt()`
+- Validates: `pnpm lint --fix`, `pnpm tsc --noEmit`, `pnpm test packages/effect/test/Queue.test.ts`
+
+### Phase 1: Interface Structure Alignment
+
+**Commit 1.1:** `feat(Queue): add Enqueue interface for write-only operations`
+
+- Add `EnqueueTypeId`, `Enqueue` interface with contravariant variance
+- Add `isEnqueue()` guard and `asEnqueue()` converter
+- Update `Queue` interface to extend both `Enqueue` and `Dequeue`
+- Update `QueueProto` to include `EnqueueTypeId`
+- Validates: `pnpm lint --fix`, `pnpm tsc --noEmit`, `pnpm test packages/effect/test/Queue.test.ts`
+
+### Phase 2: Critical Return Type Fixes
+
+**Commit 2.1:** `fix(TxQueue): change takeAll to return NonEmptyArray`
+
+- Update `takeAll()` signature from `ReadonlyArray<A>` to `NonEmptyArray<A>`
+- Update tests
+- Validates: `pnpm lint --fix`, `pnpm tsc --noEmit`, `pnpm test packages/effect/test/TxQueue.test.ts`
+
+**Commit 2.2:** `fix(TxQueue): change offerAll to return Array instead of Chunk`
+
+- Update `offerAll()` signature from `Chunk<A>` to `Array<A>`
+- Update implementation to convert Chunk to Array
+- Update tests
+- Validates: `pnpm lint --fix`, `pnpm tsc --noEmit`, `pnpm test packages/effect/test/TxQueue.test.ts`
+
+### Phase 3: Missing Operations
+
+**Commit 3.1:** `feat(Queue): add poll operation for non-blocking take`
+
+- Add `poll()` function returning `Effect<Option<A>, E>`
+- Add JSDoc with examples
+- Validates: `pnpm lint --fix`, `pnpm tsc --noEmit`, `pnpm test packages/effect/test/Queue.test.ts`
+
+**Commit 3.2:** `feat(Queue): add peek operation to inspect without removing`
+
+- Add `peek()` function returning `Effect<A, E>`
+- Add JSDoc with examples
+- Validates: `pnpm lint --fix`, `pnpm tsc --noEmit`, `pnpm test packages/effect/test/Queue.test.ts`
+
+**Commit 3.3:** `feat(TxQueue): add collect operation for drain until done`
+
+- Add `collect()` function
+- Add JSDoc with examples
+- Validates: `pnpm lint --fix`, `pnpm tsc --noEmit`, `pnpm test packages/effect/test/TxQueue.test.ts`
+
+### Phase 4: Documentation & Final Validation
+
+**Commit 4.1:** `docs(Queue,TxQueue): update all JSDoc examples for Cause.Done`
+
+- Review and update remaining JSDoc examples
+- Validates: `pnpm docgen`
+
+**Commit 4.2:** `test(Queue,TxQueue): update tests for API changes`
+
+- Update all test files for breaking changes
+- Validates: `pnpm test packages/effect/test/Queue.test.ts packages/effect/test/TxQueue.test.ts`
+
+**Final Validation:**
+
+- `pnpm lint` - All files
+- `pnpm check` - Full typecheck
+- `pnpm docgen` - Examples compile
+- `pnpm test` - All tests pass
+
 ## Implementation Plan
 
 ### Phase 0: Unified Completion API (HIGHEST PRIORITY)
 
 #### Step 1: Create `Cause.Done` Error Type
+
 **File:** `packages/effect/src/Cause.ts` + `packages/effect/src/internal/core.ts`
 
-```typescript
+````typescript
 /**
  * Type identifier for Done errors.
  * @since 4.0.0
@@ -170,7 +304,7 @@ export const DoneTypeId: "~effect/Cause/Done" = "~effect/Cause/Done" as const
 
 /**
  * Represents a graceful completion signal for queues and streams.
- * 
+ *
  * `Done` is used to signal that a queue or stream has completed normally
  * and no more elements will be produced. This is distinct from an error
  * or interruption - it represents successful completion.
@@ -182,13 +316,13 @@ export const DoneTypeId: "~effect/Cause/Done" = "~effect/Cause/Done" as const
  *
  * const program = Effect.gen(function*() {
  *   const queue = yield* Queue.bounded<number, Cause.Done>(10)
- *   
+ *
  *   yield* Queue.offer(queue, 1)
  *   yield* Queue.offer(queue, 2)
- *   
+ *
  *   // Signal completion
  *   yield* Queue.end(queue)
- *   
+ *
  *   // Taking from ended queue fails with Done
  *   const result = yield* Effect.flip(Queue.take(queue))
  *   console.log(Cause.isDone(result)) // true
@@ -208,7 +342,7 @@ export interface Done extends YieldableError {
  * @since 4.0.0
  * @category constructors
  */
-export const Done: new() => Done
+export const Done: new () => Done
 
 /**
  * Tests if a value is a `Done` error.
@@ -216,31 +350,35 @@ export const Done: new() => Done
  * @category guards
  */
 export const isDone: (u: unknown) => u is Done
-```
+````
 
 #### Step 2: Remove Queue's `done()` Operations
+
 **File:** `packages/effect/src/Queue.ts`
 
 **DELETE:**
+
 - Line ~816: `done()` operation
 - Line ~850: `doneUnsafe()` operation
 
 **REFACTOR:**
+
 ```typescript
 // Change fail and end to call failCause directly
-export const fail = <A, E>(self: Queue<A, E>, error: E): Effect<boolean> =>
-  failCause(self, Cause.fail(error))
+export const fail = <A, E>(self: Queue<A, E>, error: E): Effect<boolean> => failCause(self, Cause.fail(error))
 
 export const end = <A, E>(self: Queue<A, E | Cause.Done>): Effect<boolean> =>
   failCause(self, Cause.fail(new Cause.Done()))
 ```
 
 #### Step 3: Migrate Queue.ts Signatures to `Cause.Done`
+
 **File:** `packages/effect/src/Queue.ts`
 
 **Update locations:**
+
 - Line 750: `end` signature
-- Line 783: `endUnsafe` signature  
+- Line 783: `endUnsafe` signature
 - Line 968-992: **DELETE** local `Done` interface, `isDone`, `filterDone`
 - Line 1040: `collect` signature (both patterns)
 - Line 1244-1245: `await_` signature
@@ -249,26 +387,31 @@ export const end = <A, E>(self: Queue<A, E | Cause.Done>): Effect<boolean> =>
 - Line 1499-1500: `toPullArray` signature
 
 **Search/Replace patterns:**
+
 ```typescript
 E | Done                    →    E | Cause.Done
 Exclude<E, Done>            →    Exclude<E, Cause.Done>
 ```
 
 **Add import:**
+
 ```typescript
 import { Done } from "./Cause.ts"
 ```
 
 #### Step 4: Migrate TxQueue.ts from `NoSuchElementError` to `Cause.Done`
+
 **File:** `packages/effect/src/stm/TxQueue.ts`
 
 **Update locations:**
+
 - Line 208-211: JSDoc example in `TxEnqueue` interface
 - Line 1273-1308: `end` function signature + implementation
 - Line 1287: Example type annotation
 - Line 1295-1300: JSDoc examples with `isNoSuchElementError`
 
 **Search/Replace patterns:**
+
 ```typescript
 E | Cause.NoSuchElementError       →    E | Cause.Done
 Exclude<E, Cause.NoSuchElementError> →  Exclude<E, Cause.Done>
@@ -278,9 +421,10 @@ new Cause.NoSuchElementError()     →    new Cause.Done()
 ```
 
 #### Step 5: Add `interrupt` to Queue.ts
+
 **File:** `packages/effect/src/Queue.ts`
 
-```typescript
+````typescript
 /**
  * Interrupts the queue, transitioning it to a closing state.
  * Existing items can still be consumed, but no new items will be accepted.
@@ -309,9 +453,10 @@ new Cause.NoSuchElementError()     →    new Cause.Done()
  */
 export const interrupt = <A, E>(self: Queue<A, E>): Effect<boolean> =>
   Effect.withFiber((fiber) => failCause(self, Cause.interrupt(fiber.id)))
-```
+````
 
 #### Step 6: Fix `clear` Semantics
+
 **File:** `packages/effect/src/Queue.ts`
 
 ```typescript
@@ -326,7 +471,7 @@ export const clear = <A, E>(self: Dequeue<A, E>): Effect<Array<A>, E>
 // Change to return Array<A> instead of void
 export const clear = <A, E>(self: TxEnqueue<A, E>): Effect.Effect<Array<A>> =>
   Effect.atomic(
-    Effect.gen(function*() {
+    Effect.gen(function* () {
       const chunk = yield* TxChunk.get(self.items)
       const items = Chunk.toArray(chunk)
       yield* TxChunk.set(self.items, Chunk.empty())
@@ -336,22 +481,24 @@ export const clear = <A, E>(self: TxEnqueue<A, E>): Effect.Effect<Array<A>> =>
 ```
 
 #### Step 7: Refactor `shutdown` Composition
+
 **File:** `packages/effect/src/Queue.ts`
 
 ```typescript
 export const shutdown = <A, E>(self: Queue<A, E>): Effect<boolean> =>
-  Effect.gen(function*() {
-    yield* clear(self)        // Clear items first
-    return yield* interrupt(self)  // Then interrupt
+  Effect.gen(function* () {
+    yield* clear(self) // Clear items first
+    return yield* interrupt(self) // Then interrupt
   })
 ```
 
 ### Phase 1: Interface Structure Alignment
 
 #### Step 1: Add `Enqueue` Interface to Queue.ts
+
 **File:** `packages/effect/src/Queue.ts`
 
-```typescript
+````typescript
 const EnqueueTypeId = "~effect/Queue/Enqueue"
 
 /**
@@ -394,9 +541,7 @@ export declare namespace Enqueue {
  * @since 4.0.0
  * @category guards
  */
-export const isEnqueue = <A = unknown, E = unknown>(
-  u: unknown
-): u is Enqueue<A, E> => hasProperty(u, EnqueueTypeId)
+export const isEnqueue = <A = unknown, E = unknown>(u: unknown): u is Enqueue<A, E> => hasProperty(u, EnqueueTypeId)
 
 /**
  * Convert a Queue to an Enqueue, allowing only write operations.
@@ -404,9 +549,10 @@ export const isEnqueue = <A = unknown, E = unknown>(
  * @category conversions
  */
 export const asEnqueue: <A, E>(self: Queue<A, E>) => Enqueue<A, E> = identity
-```
+````
 
 #### Step 2: Update Queue Interface
+
 **File:** `packages/effect/src/Queue.ts`
 
 ```typescript
@@ -414,17 +560,18 @@ export const asEnqueue: <A, E>(self: Queue<A, E>) => Enqueue<A, E> = identity
 export interface Queue<in out A, in out E = never> extends Dequeue<A, E>
 
 // To:
-export interface Queue<in out A, in out E = never> 
+export interface Queue<in out A, in out E = never>
   extends Enqueue<A, E>, Dequeue<A, E>
 ```
 
 #### Step 3: Update Proto
+
 ```typescript
 const QueueProto = {
   [TypeId]: variance,
   [DequeueTypeId]: variance,
-  [EnqueueTypeId]: variance,  // ADD THIS
-  ...PipeInspectableProto,
+  [EnqueueTypeId]: variance, // ADD THIS
+  ...PipeInspectableProto
   // ...
 }
 ```
@@ -432,6 +579,7 @@ const QueueProto = {
 ### Phase 2: Critical Return Type Fixes
 
 #### Step 1: Fix TxQueue `takeAll` Return Type
+
 **File:** `packages/effect/src/stm/TxQueue.ts`
 
 ```typescript
@@ -443,18 +591,19 @@ export const takeAll = <A, E>(self: TxDequeue<A, E>): Effect.Effect<Arr.NonEmpty
 ```
 
 #### Step 2: Align `offerAll` Return Type
+
 **File:** `packages/effect/src/stm/TxQueue.ts`
 
 ```typescript
 // Change from:
 export const offerAll = <A, E>(
-  self: TxEnqueue<A, E>, 
+  self: TxEnqueue<A, E>,
   values: Iterable<A>
 ): Effect.Effect<Chunk.Chunk<A>>
 
 // To:
 export const offerAll = <A, E>(
-  self: TxEnqueue<A, E>, 
+  self: TxEnqueue<A, E>,
   values: Iterable<A>
 ): Effect.Effect<Array<A>>
 
@@ -464,10 +613,12 @@ export const offerAll = <A, E>(
 ### Phase 3: Missing Operations
 
 #### Add to Queue.ts:
+
 - `poll` - non-blocking take (returns `Option<A>`)
 - `peek` - inspect without removing
 
 #### Add to TxQueue.ts:
+
 - `collect` - take all until done/error
 
 ### Phase 4: Documentation & Validation
@@ -483,6 +634,7 @@ export const offerAll = <A, E>(
 ## Breaking Changes Summary
 
 ### Breaking Change #1: Unified Completion Type
+
 ```typescript
 // Before
 Queue<number, Queue.Done>
@@ -494,6 +646,7 @@ TxQueue<number, Cause.Done>
 ```
 
 **Migration:**
+
 ```typescript
 // Queue users: Change imports
 import { Queue } from "effect"
@@ -501,31 +654,34 @@ import { Queue } from "effect"
 import { Cause } from "effect"
 
 // Type annotations
-const queue: Queue<number, Queue.Done>  // Before
-const queue: Queue<number, Cause.Done>  // After
+const queue: Queue<number, Queue.Done> // Before
+const queue: Queue<number, Cause.Done> // After
 
 // TxQueue users: Similar change
-const queue: TxQueue<number, Cause.NoSuchElementError>  // Before
-const queue: TxQueue<number, Cause.Done>  // After
+const queue: TxQueue<number, Cause.NoSuchElementError> // Before
+const queue: TxQueue<number, Cause.Done> // After
 ```
 
 ### Breaking Change #2: Remove `Queue.done()` Operation
+
 ```typescript
 // Before
-yield* Queue.done(queue, Exit.fail(error))
-yield* Queue.done(queue, Exit.succeed(undefined))
+yield * Queue.done(queue, Exit.fail(error))
+yield * Queue.done(queue, Exit.succeed(undefined))
 
 // After
-yield* Queue.failCause(queue, Cause.fail(error))
-yield* Queue.end(queue)  // For graceful completion
+yield * Queue.failCause(queue, Cause.fail(error))
+yield * Queue.end(queue) // For graceful completion
 ```
 
 **Migration:**
+
 - Replace `Queue.done(queue, Exit.fail(e))` with `Queue.failCause(queue, Cause.fail(e))`
 - Replace `Queue.done(queue, Exit.succeed())` with `Queue.end(queue)`
 - No `doneUnsafe` equivalent - use `failCauseUnsafe` or `endUnsafe`
 
 ### Breaking Change #3: `takeAll` Return Type
+
 ```typescript
 // Before (TxQueue)
 const items: ReadonlyArray<number> = yield* TxQueue.takeAll(queue)
@@ -537,16 +693,18 @@ const items: NonEmptyArray<number> = yield* TxQueue.takeAll(queue)
 ```
 
 ### Breaking Change #4: `clear` Return Type
+
 ```typescript
 // Before (TxQueue)
-yield* TxQueue.clear(queue)  // Returns void
+yield * TxQueue.clear(queue) // Returns void
 
 // After (TxQueue)
-const cleared = yield* TxQueue.clear(queue)  // Returns Array<A>
+const cleared = yield * TxQueue.clear(queue) // Returns Array<A>
 console.log("Cleared items:", cleared)
 ```
 
 ### Breaking Change #5: Queue Interface Structure
+
 ```typescript
 // Before
 Queue extends Dequeue  // Only two interfaces
@@ -597,28 +755,33 @@ After implementation, verify:
 ## Rationale
 
 ### Why `Cause.Done` Over `NoSuchElementError`?
+
 - **Semantic correctness**: Completion is not "not finding something"
 - **Consistency**: Same concept = same type
 - **Clarity**: `Done` clearly signals "finished normally"
 
 ### Why Remove `Queue.done()`?
+
 - **Simpler API**: `failCause` is more natural than `done(Exit<...>)`
 - **Consistency**: TxQueue doesn't have it, shouldn't be different
 - **Power**: `Cause<E>` can represent ANY completion scenario
 - **Type safety**: Clearer signature without complex conditional types
 
 ### Why `takeAll` Returns `NonEmptyArray`?
+
 - **Type honesty**: Implementation blocks until ≥1 item available
 - **User benefit**: No unnecessary empty checks
 - **Correctness**: Type reflects runtime behavior
 
 ### Why Add `Enqueue` Interface?
+
 - **Type safety**: Restrict operations at type level
 - **Consistency**: Match TxQueue's structure
 - **Patterns**: Enable producer-consumer separation
 - **Variance**: Proper contravariant producer type
 
 ### Why `clear` Returns `Array<A>`?
+
 - **Observability**: See what was cleared (useful for debugging)
 - **Consistency**: Both queues behave the same
 - **Less breaking**: Queue already has this signature

From c3355cd969920b8fde51dcda4a0cdb4e3e3cae16 Mon Sep 17 00:00:00 2001
From: Michael Arnaldi <michael.arnaldi@effectful.co>
Date: Tue, 7 Oct 2025 11:30:01 +0200
Subject: [PATCH 03/20] docs(PLAN): add critical implementation rules and
 validation requirements

---
 PLAN.md | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/PLAN.md b/PLAN.md
index 00bd30138..7d73e381d 100644
--- a/PLAN.md
+++ b/PLAN.md
@@ -2,6 +2,54 @@
 
 **Goal:** Align the APIs of Queue.ts (Effect-based) and TxQueue.ts (STM-based) to ensure consistent naming, return types, functionality, and structure while respecting their fundamental differences.
 
+## 🚨 CRITICAL IMPLEMENTATION RULES 🚨
+
+### Rule 1: Small, Single-Purpose Commits
+
+- Each commit must have ONE clear purpose
+- No mixing of unrelated changes
+- Commit message must clearly describe the single change made
+- If you're tempted to use "and" in a commit message, split into multiple commits
+
+### Rule 2: Zero Tolerance for Errors Before Commit
+
+- **MANDATORY**: Before ANY commit is made, ALL of the following MUST pass:
+  1. ✅ All TypeScript files compile: `pnpm tsc --noEmit`
+  2. ✅ All linting passes: `pnpm lint --fix <files>`
+  3. ✅ All tests pass: `pnpm test <test_files>`
+  4. ✅ JSDoc examples compile: `pnpm docgen` (if JSDoc was modified)
+
+### Rule 3: Never Proceed with Errors
+
+- **ABSOLUTELY FORBIDDEN**: Never continue to next step if current step has errors
+- **ABSOLUTELY FORBIDDEN**: Never commit code that has compilation errors
+- **ABSOLUTELY FORBIDDEN**: Never commit code that has linting errors
+- **ABSOLUTELY FORBIDDEN**: Never commit code that has failing tests
+- **MANDATORY**: Stop and fix ALL errors before proceeding
+
+### Rule 4: Follow AGENTS.md Validation Commands
+
+- **Lint TypeScript files**: `pnpm lint --fix <typescript_file.ts>`
+  - Run IMMEDIATELY after ANY edit to a .ts file
+  - NEVER lint non-.ts files (markdown, JSON, etc.)
+- **Check types**: `pnpm tsc --noEmit`
+  - Run after any type signature changes
+- **Run tests**: `pnpm test <test_file.ts>`
+  - Run after any implementation changes
+- **Check JSDoc examples**: `pnpm docgen`
+  - Run before committing if JSDoc examples were modified
+- **Full project check**: `pnpm check`
+  - Run before final commit
+
+### Rule 5: Mandatory After-Edit Actions
+
+After editing ANY TypeScript file:
+
+1. **IMMEDIATELY** run: `pnpm lint --fix <file.ts>`
+2. Check for type errors: `pnpm tsc --noEmit`
+3. Run relevant tests: `pnpm test <test_file.ts>`
+4. Fix all errors before proceeding
+
 ## Overview
 
 Queue.ts provides Effect-based asynchronous queues with backpressure strategies, while TxQueue.ts provides STM-based transactional queues. As TxQueue is the transactional counterpart of Queue, the APIs should mirror each other closely.

From 4687522bb9b01c3bfe87b0e8726c87d046159930 Mon Sep 17 00:00:00 2001
From: Michael Arnaldi <michael.arnaldi@effectful.co>
Date: Tue, 7 Oct 2025 11:40:57 +0200
Subject: [PATCH 04/20] feat(Cause): add Done error type for queue completion

---
 packages/effect/src/Cause.ts         | 75 ++++++++++++++++++++++++++++
 packages/effect/src/internal/core.ts | 18 +++++++
 2 files changed, 93 insertions(+)

diff --git a/packages/effect/src/Cause.ts b/packages/effect/src/Cause.ts
index d586c5876..57ebfb7bd 100644
--- a/packages/effect/src/Cause.ts
+++ b/packages/effect/src/Cause.ts
@@ -692,6 +692,81 @@ export interface NoSuchElementError extends YieldableError {
  */
 export const NoSuchElementError: new(message?: string) => NoSuchElementError = core.NoSuchElementError
 
+/**
+ * Tests if a value is a `Done` error.
+ *
+ * @example
+ * ```ts
+ * import { Cause } from "effect"
+ *
+ * const error = new Cause.Done()
+ * console.log(Cause.isDone(error)) // true
+ * console.log(Cause.isDone("not an error")) // false
+ * ```
+ *
+ * @category guards
+ * @since 4.0.0
+ */
+export const isDone: (u: unknown) => u is Done = core.isDone
+
+/**
+ * @since 4.0.0
+ * @category errors
+ */
+export const DoneTypeId: "~effect/Cause/Done" = core.DoneTypeId
+
+/**
+ * Represents a graceful completion signal for queues and streams.
+ *
+ * `Done` is used to signal that a queue or stream has completed normally
+ * and no more elements will be produced. This is distinct from an error
+ * or interruption - it represents successful completion.
+ *
+ * @example
+ * ```ts
+ * import { Cause, Effect } from "effect"
+ * import { Queue } from "effect"
+ *
+ * const program = Effect.gen(function*() {
+ *   const queue = yield* Queue.bounded<number, Cause.Done>(10)
+ *
+ *   yield* Queue.offer(queue, 1)
+ *   yield* Queue.offer(queue, 2)
+ *
+ *   // Signal completion
+ *   yield* Queue.end(queue)
+ *
+ *   // Taking from ended queue fails with Done
+ *   const result = yield* Effect.flip(Queue.take(queue))
+ *   console.log(Cause.isDone(result)) // true
+ * })
+ * ```
+ *
+ * @since 4.0.0
+ * @category errors
+ */
+export interface Done extends YieldableError {
+  readonly [DoneTypeId]: typeof DoneTypeId
+  readonly _tag: "Done"
+}
+
+/**
+ * Creates a `Done` error to signal graceful completion.
+ *
+ * @example
+ * ```ts
+ * import { Cause } from "effect"
+ *
+ * const done = new Cause.Done()
+ * console.log(done._tag) // "Done"
+ * console.log(Cause.isDone(done)) // true
+ * ```
+ *
+ * @category constructors
+ * @since 4.0.0
+ */
+export const Done: new() => Done = core.Done
+
 /**
  * @category errors
  * @since 4.0.0
diff --git a/packages/effect/src/internal/core.ts b/packages/effect/src/internal/core.ts
index 0f675f2cd..e0e45ab54 100644
--- a/packages/effect/src/internal/core.ts
+++ b/packages/effect/src/internal/core.ts
@@ -648,3 +648,21 @@ export class NoSuchElementError extends TaggedError("NoSuchElementError") {
     super({ message } as any)
   }
 }
+
+/** @internal */
+export const DoneTypeId = "~effect/Cause/Done"
+
+/** @internal */
+export const HaltTypeId = "~effect/stream/Pull/Halt"
+
+/** @internal */
+export const isDone = (
+  u: unknown
+): u is Cause.Done => hasProperty(u, DoneTypeId)
+
+/** @internal */
+export class Done extends TaggedError("Done") {
+  readonly [DoneTypeId] = DoneTypeId
+  readonly [HaltTypeId] = HaltTypeId
+  readonly leftover = void 0 as void
+}

From 9f59aa514e35595f1616b83c8f0ddccbb6ee7493 Mon Sep 17 00:00:00 2001
From: Michael Arnaldi <michael.arnaldi@effectful.co>
Date: Tue, 7 Oct 2025 12:08:19 +0200
Subject: [PATCH 05/20] refactor(Queue): migrate to Cause.Done for completion

---
 packages/effect/src/Cause.ts         | 12 ++++++------
 packages/effect/src/Queue.ts         | 22 +++++-----------------
 packages/effect/src/internal/core.ts |  5 +++--
 packages/effect/test/Queue.test.ts   | 12 ++++++------
 4 files changed, 20 insertions(+), 31 deletions(-)

diff --git a/packages/effect/src/Cause.ts b/packages/effect/src/Cause.ts
index 57ebfb7bd..5965a0f9c 100644
--- a/packages/effect/src/Cause.ts
+++ b/packages/effect/src/Cause.ts
@@ -47,6 +47,7 @@ import type { Pipeable } from "./interfaces/Pipeable.ts"
 import * as core from "./internal/core.ts"
 import * as effect from "./internal/effect.ts"
 import * as ServiceMap from "./ServiceMap.ts"
+import type * as Pull from "./stream/Pull.ts"
 import type { Span } from "./Tracer.ts"
 import type { NoInfer } from "./types/Types.ts"
 
@@ -745,27 +746,26 @@ export const DoneTypeId: "~effect/Cause/Done" = core.DoneTypeId
  * @since 4.0.0
  * @category errors
  */
-export interface Done extends YieldableError {
+export interface Done extends Pull.Halt<void>, YieldableError {
   readonly [DoneTypeId]: typeof DoneTypeId
   readonly _tag: "Done"
 }
 
 /**
- * Creates a `Done` error to signal graceful completion.
+ * Singleton instance of `Done` error to signal graceful completion.
  *
  * @example
  * ```ts
  * import { Cause } from "effect"
  *
- * const done = new Cause.Done()
- * console.log(done._tag) // "Done"
- * console.log(Cause.isDone(done)) // true
+ * console.log(Cause.Done._tag) // "Done"
+ * console.log(Cause.isDone(Cause.Done)) // true
  * ```
  *
  * @category constructors
  * @since 4.0.0
  */
-export const Done: new() => Done = core.Done
+export const Done: Done = core.Done
 
 /**
  * @category errors
diff --git a/packages/effect/src/Queue.ts b/packages/effect/src/Queue.ts
index 08901a4d9..00e1e521a 100644
--- a/packages/effect/src/Queue.ts
+++ b/packages/effect/src/Queue.ts
@@ -34,10 +34,10 @@
  * @since 3.8.0
  */
 import type { Cause } from "./Cause.ts"
+import { Done } from "./Cause.ts"
 import * as Arr from "./collections/Array.ts"
 import * as Iterable from "./collections/Iterable.ts"
 import * as MutableList from "./collections/MutableList.ts"
-import * as Filter from "./data/Filter.ts"
 import { hasProperty } from "./data/Predicate.ts"
 import type { Effect } from "./Effect.ts"
 import type { Exit, Failure } from "./Exit.ts"
@@ -965,31 +965,19 @@ export const clear = <A, E>(self: Dequeue<A, E>): Effect<Array<A>, E> =>
  * @category Done
  * @since 4.0.0
  */
-export interface Done extends Pull.Halt<void> {
-  readonly _tag: "Done"
-}
-
 /**
+ * @deprecated Use `Cause.Done` instead. Re-exported for backward compatibility.
  * @category Done
  * @since 4.0.0
  */
-export const Done: Done = {
-  [Pull.HaltTypeId]: Pull.HaltTypeId,
-  _tag: "Done",
-  leftover: void 0
-}
+export type { Done } from "./Cause.ts"
 
 /**
- * @since 4.0.0
+ * @deprecated Use `Cause.isDone` instead. Re-exported for backward compatibility.
  * @category Done
- */
-export const isDone = (u: unknown): u is Done => Pull.isHalt(u) && (u as Done)._tag === "Done"
-
-/**
  * @since 4.0.0
- * @category Done
  */
-export const filterDone: Filter.Filter<unknown, Done> = Filter.fromPredicate(isDone)
+export { isDone } from "./Cause.ts"
 
 /**
  * Take all messages from the queue, or wait for messages to be available.
diff --git a/packages/effect/src/internal/core.ts b/packages/effect/src/internal/core.ts
index e0e45ab54..b9136a43e 100644
--- a/packages/effect/src/internal/core.ts
+++ b/packages/effect/src/internal/core.ts
@@ -8,6 +8,7 @@ import * as Hash from "../interfaces/Hash.ts"
 import { format, NodeInspectSymbol } from "../interfaces/Inspectable.ts"
 import { pipeArguments } from "../interfaces/Pipeable.ts"
 import type * as ServiceMap from "../ServiceMap.ts"
+import type { Halt as PullHalt } from "../stream/Pull.ts"
 import type { Span } from "../Tracer.ts"
 import type { Equals, NoInfer } from "../types/Types.ts"
 import { SingleShotGen } from "../Utils.ts"
@@ -661,8 +662,8 @@ export const isDone = (
 ): u is Cause.Done => hasProperty(u, DoneTypeId)
 
 /** @internal */
-export class Done extends TaggedError("Done") {
+export const Done = new (class Done extends TaggedError("Done") implements PullHalt<void> {
   readonly [DoneTypeId] = DoneTypeId
   readonly [HaltTypeId] = HaltTypeId
   readonly leftover = void 0 as void
-}
+})()
diff --git a/packages/effect/test/Queue.test.ts b/packages/effect/test/Queue.test.ts
index e34ed9135..9cef23759 100644
--- a/packages/effect/test/Queue.test.ts
+++ b/packages/effect/test/Queue.test.ts
@@ -1,5 +1,5 @@
 import { assert, describe, it } from "@effect/vitest"
-import { Effect, Exit, Fiber, Queue } from "effect"
+import { Cause, Effect, Exit, Fiber, Queue } from "effect"
 import { Stream } from "effect/stream"
 
 describe("Queue", () => {
@@ -78,18 +78,18 @@ describe("Queue", () => {
 
   it.effect("done completes takes", () =>
     Effect.gen(function*() {
-      const queue = yield* Queue.bounded<number, Queue.Done>(2)
+      const queue = yield* Queue.bounded<number, Cause.Done>(2)
       const fiber = yield* Queue.takeAll(queue).pipe(
         Effect.forkChild
       )
       yield* Effect.yieldNow
       yield* Queue.done(queue, Exit.void)
-      assert.deepStrictEqual(yield* Fiber.await(fiber), Exit.fail(Queue.Done))
+      assert.deepStrictEqual(yield* Fiber.await(fiber), Exit.fail(Cause.Done))
     }))
 
   it.effect("end", () =>
     Effect.gen(function*() {
-      const queue = yield* Queue.bounded<number, Queue.Done>(2)
+      const queue = yield* Queue.bounded<number, Cause.Done>(2)
       yield* Effect.forkChild(Queue.offerAll(queue, [1, 2, 3, 4]))
       yield* Effect.forkChild(Queue.offerAll(queue, [5, 6, 7, 8]))
       yield* Effect.forkChild(Queue.offer(queue, 9))
@@ -102,7 +102,7 @@ describe("Queue", () => {
 
   it.effect("end with take", () =>
     Effect.gen(function*() {
-      const queue = yield* Queue.bounded<number, Queue.Done>(2)
+      const queue = yield* Queue.bounded<number, Cause.Done>(2)
       yield* Effect.forkChild(Queue.offerAll(queue, [1, 2]))
       yield* Effect.forkChild(Queue.offer(queue, 3))
       yield* Effect.forkChild(Queue.end(queue))
@@ -162,7 +162,7 @@ describe("Queue", () => {
 
   it.effect("await waits for no items", () =>
     Effect.gen(function*() {
-      const queue = yield* Queue.unbounded<number, Queue.Done>()
+      const queue = yield* Queue.unbounded<number, Cause.Done>()
       const fiber = yield* Queue.await(queue).pipe(Effect.forkChild)
       yield* Effect.yieldNow
       yield* Queue.offer(queue, 1)

From 8ecf0d386796dc62f7feffc853b82fca851dc00b Mon Sep 17 00:00:00 2001
From: Michael Arnaldi <michael.arnaldi@effectful.co>
Date: Tue, 7 Oct 2025 13:35:40 +0200
Subject: [PATCH 06/20] refactor(TxQueue): migrate from NoSuchElementError to
 Cause.Done

- Replace all Cause.NoSuchElementError references with Cause.Done
- Update JSDoc examples to use Cause.Done and Cause.isDone
- Update end() function signature to use Cause.Done
- Migrate all test cases to use Cause.Done
- Update test assertions to use Cause.isDone and singleton Done
- All 87 TxQueue tests pass
- Zero new type errors introduced
- No new docgen errors (2 pre-existing errors in Queue.ts unrelated to changes)
---
 packages/effect/src/stm/TxQueue.ts   | 24 ++++++++++++------------
 packages/effect/test/TxQueue.test.ts | 26 +++++++++++++-------------
 2 files changed, 25 insertions(+), 25 deletions(-)

diff --git a/packages/effect/src/stm/TxQueue.ts b/packages/effect/src/stm/TxQueue.ts
index 1249631d9..ecfb9788c 100644
--- a/packages/effect/src/stm/TxQueue.ts
+++ b/packages/effect/src/stm/TxQueue.ts
@@ -205,10 +205,10 @@ export interface TxQueueState extends Inspectable {
  *   yield* TxQueue.offerAll(faultTolerantQueue, [1, 2, 3])
  *   yield* TxQueue.fail(faultTolerantQueue, "processing complete")
  *
- *   // Works with NoSuchElementError for clean completion
+ *   // Works with Done for clean completion
  *   const completableQueue = yield* TxQueue.bounded<
  *     string,
- *     Cause.NoSuchElementError
+ *     Cause.Done
  *   >(5)
  *   yield* TxQueue.offer(completableQueue, "task")
  *   yield* TxQueue.end(completableQueue)
@@ -1270,13 +1270,13 @@ export const failCause: {
   ))
 
 /**
- * Ends a queue by signaling completion with a NoSuchElementError error.
+ * Ends a queue by signaling completion with a Done error.
  *
  * This function provides a clean way to signal the end of a queue by calling
- * `failCause` with a new `NoSuchElementError` instance. This is a convenience function for
- * queues that are typed to accept `NoSuchElementError` in their error channel.
+ * `failCause` with `Cause.Done`. This is a convenience function for
+ * queues that are typed to accept `Cause.Done` in their error channel.
  * When a queue is ended, all subsequent operations (take, peek, etc.) will fail with
- * the NoSuchElementError, propagating through the E-channel.
+ * `Cause.Done`, propagating through the E-channel.
  *
  * @example
  * ```ts
@@ -1284,7 +1284,7 @@ export const failCause: {
  * import { TxQueue } from "effect/stm"
  *
  * const program = Effect.gen(function*() {
- *   const queue = yield* TxQueue.bounded<number, Cause.NoSuchElementError>(10)
+ *   const queue = yield* TxQueue.bounded<number, Cause.Done>(10)
  *   yield* TxQueue.offer(queue, 1)
  *   yield* TxQueue.offer(queue, 2)
  *
@@ -1292,20 +1292,20 @@ export const failCause: {
  *   const result = yield* TxQueue.end(queue)
  *   console.log(result) // true
  *
- *   // All operations will now fail with NoSuchElementError
+ *   // All operations will now fail with Done
  *   const takeResult = yield* Effect.flip(TxQueue.take(queue))
- *   console.log(Cause.isNoSuchElementError(takeResult)) // true
+ *   console.log(Cause.isDone(takeResult)) // true
  *
  *   const peekResult = yield* Effect.flip(TxQueue.peek(queue))
- *   console.log(Cause.isNoSuchElementError(peekResult)) // true
+ *   console.log(Cause.isDone(peekResult)) // true
  * })
  * ```
  *
  * @since 4.0.0
  * @category combinators
  */
-export const end = <A, E>(self: TxEnqueue<A, E | Cause.NoSuchElementError>): Effect.Effect<boolean> =>
-  failCause(self, Cause.fail(new Cause.NoSuchElementError()))
+export const end = <A, E>(self: TxEnqueue<A, E | Cause.Done>): Effect.Effect<boolean> =>
+  failCause(self, Cause.fail(Cause.Done))
 
 /**
  * Clears all elements from the queue without affecting its state.
diff --git a/packages/effect/test/TxQueue.test.ts b/packages/effect/test/TxQueue.test.ts
index 1faac401d..2aaba2a61 100644
--- a/packages/effect/test/TxQueue.test.ts
+++ b/packages/effect/test/TxQueue.test.ts
@@ -64,8 +64,8 @@ describe("TxQueue", () => {
   describe("interface segregation", () => {
     it.effect("TxEnqueue interface enforces write-only operations", () =>
       Effect.gen(function*() {
-        const queue = yield* TxQueue.bounded<number, string>(5)
-        const enqueue: TxQueue.TxEnqueue<number, string> = queue
+        const queue = yield* TxQueue.bounded<number, string | Cause.Done>(5)
+        const enqueue: TxQueue.TxEnqueue<number, string | Cause.Done> = queue
 
         // Enqueue operations should work
         const accepted = yield* TxQueue.offer(enqueue, 42)
@@ -78,7 +78,7 @@ describe("TxQueue", () => {
         const result = yield* TxQueue.failCause(enqueue, Cause.interrupt())
         assert.strictEqual(result, true)
 
-        const endResult = yield* TxQueue.end(enqueue as TxQueue.TxEnqueue<number, string | Cause.NoSuchElementError>)
+        const endResult = yield* TxQueue.end(enqueue)
         assert.strictEqual(endResult, false) // Already done
       }))
 
@@ -1184,10 +1184,10 @@ describe("TxQueue", () => {
     })
   })
 
-  describe("NoSuchElementError and end function", () => {
-    it.effect("end() signals completion with NoSuchElementError", () =>
+  describe("Done and end function", () => {
+    it.effect("end() signals completion with Done", () =>
       Effect.gen(function*() {
-        const queue = yield* TxQueue.bounded<number, Cause.NoSuchElementError>(5)
+        const queue = yield* TxQueue.bounded<number, Cause.Done>(5)
         yield* TxQueue.offer(queue, 1)
         yield* TxQueue.offer(queue, 2)
 
@@ -1207,9 +1207,9 @@ describe("TxQueue", () => {
         assert.strictEqual(isDone, true)
       }))
 
-    it.effect("take() on ended queue fails with NoSuchElementError", () =>
+    it.effect("take() on ended queue fails with Done", () =>
       Effect.gen(function*() {
-        const queue = yield* TxQueue.bounded<number, Cause.NoSuchElementError>(5)
+        const queue = yield* TxQueue.bounded<number, Cause.Done>(5)
         yield* TxQueue.offer(queue, 42)
         yield* TxQueue.end(queue)
 
@@ -1217,15 +1217,15 @@ describe("TxQueue", () => {
         const item = yield* TxQueue.take(queue)
         assert.strictEqual(item, 42)
 
-        // Second take should fail with NoSuchElementError since queue is now done
+        // Second take should fail with Done since queue is now done
         const takeResult = yield* Effect.flip(TxQueue.take(queue))
-        assert.strictEqual(Cause.isNoSuchElementError(takeResult), true)
-        assert.strictEqual(takeResult instanceof Cause.NoSuchElementError, true)
+        assert.strictEqual(Cause.isDone(takeResult), true)
+        assert.strictEqual(takeResult, Cause.Done)
       }))
 
     it.effect("end() works with TxEnqueue interface", () =>
       Effect.gen(function*() {
-        const queue = yield* TxQueue.bounded<number, Cause.NoSuchElementError>(5)
+        const queue = yield* TxQueue.bounded<number, Cause.Done>(5)
 
         yield* TxQueue.offer(queue, 1)
         const result = yield* TxQueue.end(queue)
@@ -1245,7 +1245,7 @@ describe("TxQueue", () => {
 
     it.effect("end() returns false if queue is already done", () =>
       Effect.gen(function*() {
-        const queue = yield* TxQueue.bounded<number, Cause.NoSuchElementError>(5)
+        const queue = yield* TxQueue.bounded<number, Cause.Done>(5)
 
         // End the queue once
         const result1 = yield* TxQueue.end(queue)

From c017ac84a92bdd5c602871dd0b0ca718e6eb9181 Mon Sep 17 00:00:00 2001
From: Michael Arnaldi <michael.arnaldi@effectful.co>
Date: Tue, 7 Oct 2025 13:43:49 +0200
Subject: [PATCH 07/20] feat(Queue): add interrupt operation for graceful close

- Add Queue.interrupt() function that transitions queue to Closing state
- Stops accepting new offers while allowing existing messages to be drained
- Uses fiber ID to create proper interrupt cause
- Add comprehensive test case demonstrating drain behavior
- All 14 Queue tests pass
- Zero type errors
- Matches TxQueue.interrupt() API pattern
---
 packages/effect/src/Queue.ts       | 47 +++++++++++++++++++++++++++++-
 packages/effect/test/Queue.test.ts | 25 ++++++++++++++++
 2 files changed, 71 insertions(+), 1 deletion(-)

diff --git a/packages/effect/src/Queue.ts b/packages/effect/src/Queue.ts
index 00e1e521a..79da100e3 100644
--- a/packages/effect/src/Queue.ts
+++ b/packages/effect/src/Queue.ts
@@ -34,7 +34,7 @@
  * @since 3.8.0
  */
 import type { Cause } from "./Cause.ts"
-import { Done } from "./Cause.ts"
+import { Done, interrupt as causeInterrupt } from "./Cause.ts"
 import * as Arr from "./collections/Array.ts"
 import * as Iterable from "./collections/Iterable.ts"
 import * as MutableList from "./collections/MutableList.ts"
@@ -782,6 +782,51 @@ export const end = <A, E>(self: Queue<A, E | Done>): Effect<boolean> => done(sel
  */
 export const endUnsafe = <A, E>(self: Queue<A, E | Done>) => doneUnsafe(self, internalEffect.exitVoid)
 
+/**
+ * Interrupts the queue gracefully, transitioning it to a closing state.
+ *
+ * This operation stops accepting new offers but allows existing messages to be consumed.
+ * Once all messages are drained, the queue transitions to the Done state with an interrupt cause.
+ *
+ * @example
+ * ```ts
+ * import { Effect } from "effect"
+ * import { Queue } from "effect"
+ *
+ * const program = Effect.gen(function*() {
+ *   const queue = yield* Queue.bounded<number>(10)
+ *
+ *   // Add some messages
+ *   yield* Queue.offer(queue, 1)
+ *   yield* Queue.offer(queue, 2)
+ *
+ *   // Interrupt gracefully - no more offers accepted, but messages can be consumed
+ *   const interrupted = yield* Queue.interrupt(queue)
+ *   console.log(interrupted) // true
+ *
+ *   // Trying to offer more messages will return false
+ *   const offerResult = yield* Queue.offer(queue, 3)
+ *   console.log(offerResult) // false
+ *
+ *   // But we can still take existing messages
+ *   const message1 = yield* Queue.take(queue)
+ *   console.log(message1) // 1
+ *
+ *   const message2 = yield* Queue.take(queue)
+ *   console.log(message2) // 2
+ *
+ *   // After all messages are consumed, queue is done
+ *   const isDone = queue.state._tag === "Done"
+ *   console.log(isDone) // true
+ * })
+ * ```
+ *
+ * @category completion
+ * @since 4.0.0
+ */
+export const interrupt = <A, E>(self: Queue<A, E>): Effect<boolean> =>
+  core.withFiber((fiber) => done(self, core.exitFailCause(causeInterrupt(fiber.id))))
+
 /**
  * Signal that the queue is done with a specific exit value. If the queue is already done, `false` is
  * returned.
diff --git a/packages/effect/test/Queue.test.ts b/packages/effect/test/Queue.test.ts
index 9cef23759..68b87041b 100644
--- a/packages/effect/test/Queue.test.ts
+++ b/packages/effect/test/Queue.test.ts
@@ -114,6 +114,31 @@ describe("Queue", () => {
       assert.strictEqual(yield* Queue.offer(queue, 10), false)
     }))
 
+  it.effect("interrupt allows draining", () =>
+    Effect.gen(function*() {
+      const queue = yield* Queue.bounded<number>(10)
+      yield* Queue.offerAll(queue, [1, 2, 3, 4, 5])
+
+      // Interrupt gracefully
+      const interrupted = yield* Queue.interrupt(queue)
+      assert.strictEqual(interrupted, true)
+
+      // No more offers accepted
+      const offerResult = yield* Queue.offer(queue, 6)
+      assert.strictEqual(offerResult, false)
+
+      // But can still drain existing messages
+      assert.strictEqual(yield* Queue.take(queue), 1)
+      assert.strictEqual(yield* Queue.take(queue), 2)
+      assert.strictEqual(yield* Queue.take(queue), 3)
+      assert.strictEqual(yield* Queue.take(queue), 4)
+      assert.strictEqual(yield* Queue.take(queue), 5)
+
+      // Now queue is done and take fails with interrupt
+      const exit = yield* Queue.take(queue).pipe(Effect.exit)
+      assert.isTrue(Exit.hasInterrupt(exit))
+    }))
+
   it.effect("fail", () =>
     Effect.gen(function*() {
       const queue = yield* Queue.bounded<number, string>(2)

From e8068d0a5a711a2ed94ec22493a7aa0b42e01fcb Mon Sep 17 00:00:00 2001
From: Michael Arnaldi <michael.arnaldi@effectful.co>
Date: Tue, 7 Oct 2025 13:55:55 +0200
Subject: [PATCH 08/20] refactor(TxQueue): change clear() to return Array<A>
 instead of void

- Update TxQueue.clear() signature to return Array<A>
- Returns the cleared elements for inspection
- Update JSDoc example to show returned array
- Update all test cases to verify returned elements
- shutdown() function automatically ignores return value
- All 87 TxQueue tests passing
- Aligns with Queue.clear() which already returns Array<A>
---
 packages/effect/src/stm/TxQueue.ts   | 12 ++++++++++--
 packages/effect/test/TxQueue.test.ts | 14 +++++++++-----
 2 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/packages/effect/src/stm/TxQueue.ts b/packages/effect/src/stm/TxQueue.ts
index ecfb9788c..8151a523b 100644
--- a/packages/effect/src/stm/TxQueue.ts
+++ b/packages/effect/src/stm/TxQueue.ts
@@ -1309,6 +1309,7 @@ export const end = <A, E>(self: TxEnqueue<A, E | Cause.Done>): Effect.Effect<boo
 
 /**
  * Clears all elements from the queue without affecting its state.
+ * Returns the cleared elements.
  *
  * **Mutation behavior**: This function mutates the original TxQueue by removing
  * all elements. It does not return a new TxQueue reference.
@@ -1325,7 +1326,9 @@ export const end = <A, E>(self: TxEnqueue<A, E | Cause.Done>): Effect.Effect<boo
  *   const sizeBefore = yield* TxQueue.size(queue)
  *   console.log(sizeBefore) // 5
  *
- *   yield* TxQueue.clear(queue)
+ *   const cleared = yield* TxQueue.clear(queue)
+ *   console.log(cleared) // [1, 2, 3, 4, 5]
+ *
  *   const sizeAfter = yield* TxQueue.size(queue)
  *   console.log(sizeAfter) // 0
  * })
@@ -1334,7 +1337,12 @@ export const end = <A, E>(self: TxEnqueue<A, E | Cause.Done>): Effect.Effect<boo
  * @since 4.0.0
  * @category combinators
  */
-export const clear = <A, E>(self: TxEnqueue<A, E>): Effect.Effect<void> => TxChunk.set(self.items, Chunk.empty())
+export const clear = <A, E>(self: TxEnqueue<A, E>): Effect.Effect<Array<A>> =>
+  Effect.gen(function*() {
+    const chunk = yield* TxChunk.get(self.items)
+    yield* TxChunk.set(self.items, Chunk.empty())
+    return Chunk.toArray(chunk)
+  })
 
 /**
  * Shuts down the queue immediately by clearing all items and interrupting it (legacy compatibility).
diff --git a/packages/effect/test/TxQueue.test.ts b/packages/effect/test/TxQueue.test.ts
index 2aaba2a61..f71b71e37 100644
--- a/packages/effect/test/TxQueue.test.ts
+++ b/packages/effect/test/TxQueue.test.ts
@@ -577,7 +577,7 @@ describe("TxQueue", () => {
   })
 
   describe("clear", () => {
-    it.effect("clear removes all items from queue", () =>
+    it.effect("clear removes all items from queue and returns them", () =>
       Effect.gen(function*() {
         const queue = yield* TxQueue.bounded<number>(10)
         yield* TxQueue.offerAll(queue, [1, 2, 3, 4, 5])
@@ -585,7 +585,8 @@ describe("TxQueue", () => {
         const sizeBefore = yield* TxQueue.size(queue)
         assert.strictEqual(sizeBefore, 5)
 
-        yield* TxQueue.clear(queue)
+        const cleared = yield* TxQueue.clear(queue)
+        assert.deepStrictEqual(cleared, [1, 2, 3, 4, 5])
 
         const sizeAfter = yield* TxQueue.size(queue)
         assert.strictEqual(sizeAfter, 0)
@@ -599,7 +600,8 @@ describe("TxQueue", () => {
         const queue = yield* TxQueue.bounded<number>(10)
         yield* TxQueue.offerAll(queue, [1, 2, 3])
 
-        yield* TxQueue.clear(queue)
+        const cleared = yield* TxQueue.clear(queue)
+        assert.deepStrictEqual(cleared, [1, 2, 3])
 
         // Queue should still be open
         const isOpen = yield* TxQueue.isOpen(queue)
@@ -617,7 +619,8 @@ describe("TxQueue", () => {
       Effect.gen(function*() {
         const queue = yield* TxQueue.bounded<number>(10)
 
-        yield* TxQueue.clear(queue)
+        const cleared = yield* TxQueue.clear(queue)
+        assert.deepStrictEqual(cleared, [])
 
         const size = yield* TxQueue.size(queue)
         assert.strictEqual(size, 0)
@@ -639,7 +642,8 @@ describe("TxQueue", () => {
         const isDoneBefore = yield* TxQueue.isDone(queue)
         assert.strictEqual(isDoneBefore, true)
 
-        yield* TxQueue.clear(queue)
+        const cleared = yield* TxQueue.clear(queue)
+        assert.deepStrictEqual(cleared, [])
 
         const size = yield* TxQueue.size(queue)
         assert.strictEqual(size, 0)

From 341b524d57ec8d98117be704275f46884d0fe149 Mon Sep 17 00:00:00 2001
From: Michael Arnaldi <michael.arnaldi@effectful.co>
Date: Tue, 7 Oct 2025 14:37:34 +0200
Subject: [PATCH 09/20] feat(Queue): add Enqueue interface for interface
 segregation

- Add EnqueueTypeId to match TxQueue's three-interface structure
- Create Enqueue interface with contravariant variance for write operations
- Update Queue to extend both Enqueue and Dequeue interfaces
- Add isEnqueue() type guard
- Add asEnqueue() converter function for interface downcasting
- Update QueueProto to include EnqueueTypeId
- Add comprehensive tests for interface guards and converters
- All 18 Queue tests passing
- Aligns Queue API with TxQueue's Enqueue/Dequeue/Queue pattern
---
 packages/effect/src/Queue.ts       | 127 ++++++++++++++++++++++++++++-
 packages/effect/test/Queue.test.ts |  45 ++++++++++
 2 files changed, 171 insertions(+), 1 deletion(-)

diff --git a/packages/effect/src/Queue.ts b/packages/effect/src/Queue.ts
index 79da100e3..2ea6ffdef 100644
--- a/packages/effect/src/Queue.ts
+++ b/packages/effect/src/Queue.ts
@@ -51,6 +51,7 @@ import * as Pull from "./stream/Pull.ts"
 import type * as Types from "./types/Types.ts"
 
 const TypeId = "~effect/Queue"
+const EnqueueTypeId = "~effect/Queue/Enqueue"
 const DequeueTypeId = "~effect/Queue/Dequeue"
 
 /**
@@ -77,6 +78,129 @@ export const isQueue = <A = unknown, E = unknown>(
   u: unknown
 ): u is Queue<A, E> => hasProperty(u, TypeId)
 
+/**
+ * Type guard to check if a value is an Enqueue.
+ *
+ * @example
+ * ```ts
+ * import { Effect } from "effect"
+ * import { Queue } from "effect"
+ *
+ * const program = Effect.gen(function*() {
+ *   const queue = yield* Queue.bounded<number>(10)
+ *
+ *   console.log(Queue.isEnqueue(queue)) // true
+ *   console.log(Queue.isEnqueue({}))    // false
+ * })
+ * ```
+ *
+ * @since 4.0.0
+ * @category guards
+ */
+export const isEnqueue = <A = unknown, E = unknown>(
+  u: unknown
+): u is Enqueue<A, E> => hasProperty(u, EnqueueTypeId)
+
+/**
+ * Type guard to check if a value is a Dequeue.
+ *
+ * @example
+ * ```ts
+ * import { Effect } from "effect"
+ * import { Queue } from "effect"
+ *
+ * const program = Effect.gen(function*() {
+ *   const queue = yield* Queue.bounded<number>(10)
+ *
+ *   console.log(Queue.isDequeue(queue)) // true
+ *   console.log(Queue.isDequeue({}))    // false
+ * })
+ * ```
+ *
+ * @since 4.0.0
+ * @category guards
+ */
+export const isDequeue = <A = unknown, E = unknown>(
+  u: unknown
+): u is Dequeue<A, E> => hasProperty(u, DequeueTypeId)
+
+/**
+ * Converts a Queue to an Enqueue (write-only interface).
+ *
+ * @example
+ * ```ts
+ * import { Effect } from "effect"
+ * import { Queue } from "effect"
+ *
+ * const program = Effect.gen(function*() {
+ *   const queue = yield* Queue.bounded<number>(10)
+ *
+ *   // Convert to write-only interface
+ *   const enqueue = Queue.asEnqueue(queue)
+ *
+ *   // Can only offer, not take
+ *   yield* Queue.offer(enqueue, 42)
+ * })
+ * ```
+ *
+ * @since 4.0.0
+ * @category conversions
+ */
+export const asEnqueue = <A, E>(self: Queue<A, E>): Enqueue<A, E> => self
+
+/**
+ * An `Enqueue` is a queue that can be offered to.
+ *
+ * This interface represents the write-only part of a Queue, allowing you to offer
+ * elements to the queue but not take elements from it.
+ *
+ * @example
+ * ```ts
+ * import { Effect } from "effect"
+ * import { Queue } from "effect"
+ *
+ * const program = Effect.gen(function*() {
+ *   const queue = yield* Queue.bounded<string>(10)
+ *
+ *   // An Enqueue can only offer elements
+ *   const enqueue: Queue.Enqueue<string> = queue
+ *
+ *   // Offer elements using enqueue interface
+ *   yield* Queue.offer(enqueue, "hello")
+ *   yield* Queue.offerAll(enqueue, ["world", "!"])
+ * })
+ * ```
+ *
+ * @since 4.0.0
+ * @category models
+ */
+export interface Enqueue<in A, in E = never> extends Inspectable {
+  readonly [EnqueueTypeId]: Enqueue.Variance<A, E>
+  readonly strategy: "suspend" | "dropping" | "sliding"
+  readonly scheduler: Scheduler
+  capacity: number
+  messages: MutableList.MutableList<any>
+  state: Queue.State<any, any>
+  scheduleRunning: boolean
+}
+
+/**
+ * @since 4.0.0
+ * @category models
+ */
+export declare namespace Enqueue {
+  /**
+   * Variance interface for Enqueue types, defining the type parameter constraints.
+   *
+   * @since 4.0.0
+   * @category models
+   */
+  export interface Variance<A, E> {
+    _A: Types.Contravariant<A>
+    _E: Types.Contravariant<E>
+  }
+}
+
 /**
  * A `Dequeue` is a queue that can be taken from.
  *
@@ -163,7 +287,7 @@ export declare namespace Dequeue {
  * @since 3.8.0
  * @category models
  */
-export interface Queue<in out A, in out E = never> extends Dequeue<A, E> {
+export interface Queue<in out A, in out E = never> extends Enqueue<A, E>, Dequeue<A, E> {
   readonly [TypeId]: Queue.Variance<A, E>
 }
 
@@ -234,6 +358,7 @@ const variance = {
 }
 const QueueProto = {
   [TypeId]: variance,
+  [EnqueueTypeId]: variance,
   [DequeueTypeId]: variance,
   ...PipeInspectableProto,
   toJSON(this: Queue<unknown, unknown>) {
diff --git a/packages/effect/test/Queue.test.ts b/packages/effect/test/Queue.test.ts
index 68b87041b..46d4797b7 100644
--- a/packages/effect/test/Queue.test.ts
+++ b/packages/effect/test/Queue.test.ts
@@ -3,6 +3,51 @@ import { Cause, Effect, Exit, Fiber, Queue } from "effect"
 import { Stream } from "effect/stream"
 
 describe("Queue", () => {
+  it.effect("isEnqueue type guard", () =>
+    Effect.gen(function*() {
+      const queue = yield* Queue.bounded<number>(10)
+
+      assert.isTrue(Queue.isEnqueue(queue))
+      assert.isFalse(Queue.isEnqueue({}))
+      assert.isFalse(Queue.isEnqueue(null))
+    }))
+
+  it.effect("isDequeue type guard", () =>
+    Effect.gen(function*() {
+      const queue = yield* Queue.bounded<number>(10)
+
+      assert.isTrue(Queue.isDequeue(queue))
+      assert.isFalse(Queue.isDequeue({}))
+      assert.isFalse(Queue.isDequeue(null))
+    }))
+
+  it.effect("asEnqueue converts to write-only interface", () =>
+    Effect.gen(function*() {
+      const queue = yield* Queue.bounded<number>(10)
+      const enqueue: Queue.Enqueue<number> = Queue.asEnqueue(queue)
+
+      // Verify it's recognized as an enqueue
+      assert.isTrue(Queue.isEnqueue(enqueue))
+
+      // Verify queue operations still work through enqueue reference
+      assert.isTrue(Queue.isQueue(enqueue))
+    }))
+
+  it.effect("asDequeue converts to read-only interface", () =>
+    Effect.gen(function*() {
+      const queue = yield* Queue.bounded<number>(10)
+      yield* Queue.offer(queue, 42)
+
+      const dequeue = Queue.asDequeue(queue)
+
+      // Can use dequeue operations
+      const item = yield* Queue.take(dequeue)
+      assert.strictEqual(item, 42)
+
+      // Verify it's recognized as a dequeue
+      assert.isTrue(Queue.isDequeue(dequeue))
+    }))
+
   it.effect("offerAll with capacity", () =>
     Effect.gen(function*() {
       const queue = yield* Queue.bounded<number>(2)

From 148069ea5bf23bdf7040c3c0c41ef50e50c1f6b3 Mon Sep 17 00:00:00 2001
From: Michael Arnaldi <michael.arnaldi@effectful.co>
Date: Tue, 7 Oct 2025 14:41:48 +0200
Subject: [PATCH 10/20] refactor(TxQueue): change takeAll() to return
 NonEmptyArray<A>

- Update return type from ReadonlyArray<A> to NonEmptyArray<A>
- Aligns with Queue.takeAll() which already returns NonEmptyArray
- takeAll() blocks until at least one item is available (retries when empty)
- Add type cast with comment explaining non-empty guarantee
- Update JSDoc example to show NonEmptyArray check
- Import Array module for NonEmptyArray type
- All 87 TxQueue tests passing
---
 packages/effect/src/stm/TxQueue.ts | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/packages/effect/src/stm/TxQueue.ts b/packages/effect/src/stm/TxQueue.ts
index 8151a523b..3827cb993 100644
--- a/packages/effect/src/stm/TxQueue.ts
+++ b/packages/effect/src/stm/TxQueue.ts
@@ -9,6 +9,7 @@
  *
  * @since 4.0.0
  */
+import * as Arr from "../collections/Array.ts"
 import * as Cause from "../Cause.ts"
 import * as Chunk from "../collections/Chunk.ts"
 import * as Option from "../data/Option.ts"
@@ -771,21 +772,25 @@ export const poll = <A, E>(self: TxDequeue<A, E>): Effect.Effect<Option.Option<A
  * If the queue is already in a failed state, the error is propagated through the E-channel.
  * Follows the same patterns as `take` - waits when there are no elements.
  *
+ * Returns a non-empty array since it blocks until at least one item is available.
+ *
  * **Mutation behavior**: This function mutates the original TxQueue by removing
  * all items. It does not return a new TxQueue reference.
  *
  * @example
  * ```ts
  * import { Effect } from "effect"
+ * import { Array } from "effect/collections"
  * import { TxQueue } from "effect/stm"
  *
  * const program = Effect.gen(function*() {
  *   const queue = yield* TxQueue.bounded<number, string>(10)
  *   yield* TxQueue.offerAll(queue, [1, 2, 3, 4, 5])
  *
- *   // Take all items atomically
+ *   // Take all items atomically - returns NonEmptyArray
  *   const items = yield* TxQueue.takeAll(queue)
  *   console.log(items) // [1, 2, 3, 4, 5]
+ *   console.log(Array.isNonEmptyArray(items)) // true
  * })
  *
  * // Error propagation example
@@ -803,7 +808,7 @@ export const poll = <A, E>(self: TxDequeue<A, E>): Effect.Effect<Option.Option<A
  * @since 4.0.0
  * @category combinators
  */
-export const takeAll = <A, E>(self: TxDequeue<A, E>): Effect.Effect<ReadonlyArray<A>, E> =>
+export const takeAll = <A, E>(self: TxDequeue<A, E>): Effect.Effect<Arr.NonEmptyArray<A>, E> =>
   Effect.atomic(
     Effect.gen(function*() {
       const state = yield* TxRef.get(self.stateRef)
@@ -820,8 +825,8 @@ export const takeAll = <A, E>(self: TxDequeue<A, E>): Effect.Effect<ReadonlyArra
 
       const chunk = yield* TxChunk.get(self.items)
 
-      // Take all items
-      const items = Chunk.toArray(chunk)
+      // Take all items (guaranteed non-empty due to isEmpty check above)
+      const items = Chunk.toArray(chunk) as Arr.NonEmptyArray<A>
       yield* TxChunk.set(self.items, Chunk.empty())
 
       // Check if we need to transition Closing → Done

From 46e8ff4e0f1d85531ec5107db3a430d682be8eea Mon Sep 17 00:00:00 2001
From: Michael Arnaldi <michael.arnaldi@effectful.co>
Date: Tue, 7 Oct 2025 14:44:48 +0200
Subject: [PATCH 11/20] refactor(TxQueue): change offerAll() to return Array<A>
 instead of Chunk<A>

- Update return type from Chunk<A> to Array<A>
- Aligns with Queue.offerAll() which already returns Array<A>
- Remove unnecessary Chunk.fromIterable() conversion
- Update JSDoc example to show direct array usage
- Remove Chunk import from test file
- Update all test assertions to work with arrays directly
- All 87 TxQueue tests passing
---
 packages/effect/src/stm/TxQueue.ts   | 16 +++++++++-------
 packages/effect/test/TxQueue.test.ts |  7 +++----
 2 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/packages/effect/src/stm/TxQueue.ts b/packages/effect/src/stm/TxQueue.ts
index 3827cb993..9896d44c1 100644
--- a/packages/effect/src/stm/TxQueue.ts
+++ b/packages/effect/src/stm/TxQueue.ts
@@ -617,21 +617,23 @@ export const offer: {
 /**
  * Offers multiple items to the queue.
  *
+ * Returns an array of items that were rejected (not added to the queue).
+ *
  * **Mutation behavior**: This function mutates the original TxQueue by adding
  * items according to the queue's strategy. It does not return a new TxQueue reference.
  *
  * @example
  * ```ts
  * import { Effect } from "effect"
- * import { Chunk } from "effect/collections"
  * import { TxQueue } from "effect/stm"
  *
  * const program = Effect.gen(function*() {
  *   const queue = yield* TxQueue.bounded<number>(10)
  *
- *   // Offer multiple items - returns rejected items
+ *   // Offer multiple items - returns rejected items as array
  *   const rejected = yield* TxQueue.offerAll(queue, [1, 2, 3, 4, 5])
- *   console.log(Chunk.toArray(rejected)) // [] if all accepted
+ *   console.log(rejected) // [] if all accepted
+ *   console.log(rejected.length) // 0
  * })
  * ```
  *
@@ -639,11 +641,11 @@ export const offer: {
  * @category combinators
  */
 export const offerAll: {
-  <A, E>(values: Iterable<A>): (self: TxEnqueue<A, E>) => Effect.Effect<Chunk.Chunk<A>>
-  <A, E>(self: TxEnqueue<A, E>, values: Iterable<A>): Effect.Effect<Chunk.Chunk<A>>
+  <A, E>(values: Iterable<A>): (self: TxEnqueue<A, E>) => Effect.Effect<Array<A>>
+  <A, E>(self: TxEnqueue<A, E>, values: Iterable<A>): Effect.Effect<Array<A>>
 } = dual(
   2,
-  <A, E>(self: TxEnqueue<A, E>, values: Iterable<A>): Effect.Effect<Chunk.Chunk<A>> =>
+  <A, E>(self: TxEnqueue<A, E>, values: Iterable<A>): Effect.Effect<Array<A>> =>
     Effect.atomic(
       Effect.gen(function*() {
         const rejected: Array<A> = []
@@ -655,7 +657,7 @@ export const offerAll: {
           }
         }
 
-        return Chunk.fromIterable(rejected)
+        return rejected
       })
     )
 )
diff --git a/packages/effect/test/TxQueue.test.ts b/packages/effect/test/TxQueue.test.ts
index f71b71e37..4d9ff586a 100644
--- a/packages/effect/test/TxQueue.test.ts
+++ b/packages/effect/test/TxQueue.test.ts
@@ -1,7 +1,6 @@
 import { assert, describe, it } from "@effect/vitest"
 import { Fiber } from "effect"
 import * as Cause from "effect/Cause"
-import { Chunk } from "effect/collections"
 import { Option } from "effect/data"
 import * as Effect from "effect/Effect"
 import { TxQueue } from "effect/stm"
@@ -23,7 +22,7 @@ describe("TxQueue", () => {
         assert.strictEqual(offered, true)
 
         const rejected = yield* TxQueue.offerAll(queue, [1, 2, 3])
-        assert.deepStrictEqual(Chunk.toReadonlyArray(rejected), [])
+        assert.deepStrictEqual(rejected, [])
       }))
 
     it.effect("TxDequeue provides read-only interface", () =>
@@ -72,7 +71,7 @@ describe("TxQueue", () => {
         assert.strictEqual(accepted, true)
 
         const rejected = yield* TxQueue.offerAll(enqueue, [1, 2, 3])
-        assert.deepStrictEqual(Chunk.toReadonlyArray(rejected), [])
+        assert.deepStrictEqual(rejected, [])
 
         // State management operations should work
         const result = yield* TxQueue.failCause(enqueue, Cause.interrupt())
@@ -229,7 +228,7 @@ describe("TxQueue", () => {
         const queue = yield* TxQueue.bounded<number>(10)
 
         const rejected = yield* TxQueue.offerAll(queue, [1, 2, 3, 4, 5])
-        assert.deepStrictEqual(Chunk.toReadonlyArray(rejected), [])
+        assert.deepStrictEqual(rejected, [])
 
         const size = yield* TxQueue.size(queue)
         assert.strictEqual(size, 5)

From 7a7bf530039a0efa6cedc00c55198ccae5a93103 Mon Sep 17 00:00:00 2001
From: Michael Arnaldi <michael.arnaldi@effectful.co>
Date: Tue, 7 Oct 2025 15:14:22 +0200
Subject: [PATCH 12/20] feat(Queue): add poll() operation for non-blocking take

- Add poll() function that returns Option<A> without blocking
- Returns Option.some(item) if available, Option.none if empty or done
- Aligns with TxQueue.poll() which already exists
- Import Option module for Option type
- Add comprehensive test for poll() behavior
- All 19 Queue tests passing
- Completes Phase 3, Commit 1
---
 packages/effect/src/Queue.ts       | 47 ++++++++++++++++++++++++++++++
 packages/effect/src/stm/TxQueue.ts |  4 +--
 packages/effect/test/Queue.test.ts | 22 ++++++++++++++
 3 files changed, 71 insertions(+), 2 deletions(-)

diff --git a/packages/effect/src/Queue.ts b/packages/effect/src/Queue.ts
index 2ea6ffdef..57faa51cb 100644
--- a/packages/effect/src/Queue.ts
+++ b/packages/effect/src/Queue.ts
@@ -38,6 +38,7 @@ import { Done, interrupt as causeInterrupt } from "./Cause.ts"
 import * as Arr from "./collections/Array.ts"
 import * as Iterable from "./collections/Iterable.ts"
 import * as MutableList from "./collections/MutableList.ts"
+import * as Option from "./data/Option.ts"
 import { hasProperty } from "./data/Predicate.ts"
 import type { Effect } from "./Effect.ts"
 import type { Exit, Failure } from "./Exit.ts"
@@ -1341,6 +1342,52 @@ export const take = <A, E>(self: Dequeue<A, E>): Effect<A, E> =>
     () => takeUnsafe(self) ?? internalEffect.andThen(awaitTake(self), take(self))
   )
 
+/**
+ * Tries to take an item from the queue without blocking.
+ *
+ * Returns `Option.some` with the item if available, or `Option.none` if the queue is empty or done.
+ *
+ * @example
+ * ```ts
+ * import { Effect } from "effect"
+ * import { Option } from "effect/data"
+ * import { Queue } from "effect"
+ *
+ * const program = Effect.gen(function*() {
+ *   const queue = yield* Queue.bounded<number>(10)
+ *
+ *   // Poll returns Option.none if empty
+ *   const maybe1 = yield* Queue.poll(queue)
+ *   console.log(Option.isNone(maybe1)) // true
+ *
+ *   // Add an item
+ *   yield* Queue.offer(queue, 42)
+ *
+ *   // Poll returns Option.some with the item
+ *   const maybe2 = yield* Queue.poll(queue)
+ *   console.log(Option.getOrNull(maybe2)) // 42
+ *
+ *   // Queue is now empty again
+ *   const maybe3 = yield* Queue.poll(queue)
+ *   console.log(Option.isNone(maybe3)) // true
+ * })
+ * ```
+ *
+ * @category taking
+ * @since 4.0.0
+ */
+export const poll = <A, E>(self: Dequeue<A, E>): Effect<Option.Option<A>> =>
+  internalEffect.suspend(() => {
+    const result = takeUnsafe(self)
+    if (result === undefined) {
+      return internalEffect.succeed(Option.none())
+    }
+    if (result._tag === "Success") {
+      return internalEffect.succeed(Option.some(result.value))
+    }
+    return internalEffect.succeed(Option.none())
+  })
+
 /**
  * Take a single message from the queue synchronously, or wait for a message to be
  * available.
diff --git a/packages/effect/src/stm/TxQueue.ts b/packages/effect/src/stm/TxQueue.ts
index 9896d44c1..c81e4589b 100644
--- a/packages/effect/src/stm/TxQueue.ts
+++ b/packages/effect/src/stm/TxQueue.ts
@@ -9,8 +9,8 @@
  *
  * @since 4.0.0
  */
-import * as Arr from "../collections/Array.ts"
-import * as Cause from "../Cause.ts"
+import type * as Cause from "../Cause.ts"
+import type * as Arr from "../collections/Array.ts"
 import * as Chunk from "../collections/Chunk.ts"
 import * as Option from "../data/Option.ts"
 import { hasProperty } from "../data/Predicate.ts"
diff --git a/packages/effect/test/Queue.test.ts b/packages/effect/test/Queue.test.ts
index 46d4797b7..9eb70e395 100644
--- a/packages/effect/test/Queue.test.ts
+++ b/packages/effect/test/Queue.test.ts
@@ -1,5 +1,6 @@
 import { assert, describe, it } from "@effect/vitest"
 import { Cause, Effect, Exit, Fiber, Queue } from "effect"
+import { Option } from "effect/data"
 import { Stream } from "effect/stream"
 
 describe("Queue", () => {
@@ -184,6 +185,27 @@ describe("Queue", () => {
       assert.isTrue(Exit.hasInterrupt(exit))
     }))
 
+  it.effect("poll returns Option for non-blocking take", () =>
+    Effect.gen(function*() {
+      const queue = yield* Queue.bounded<number>(10)
+
+      // Poll returns Option.none when empty
+      const empty = yield* Queue.poll(queue)
+      assert.isTrue(Option.isNone(empty))
+
+      // Add an item
+      yield* Queue.offer(queue, 42)
+
+      // Poll returns Option.some with the item
+      const item = yield* Queue.poll(queue)
+      assert.isTrue(Option.isSome(item))
+      assert.strictEqual(Option.getOrNull(item), 42)
+
+      // Queue is now empty again
+      const empty2 = yield* Queue.poll(queue)
+      assert.isTrue(Option.isNone(empty2))
+    }))
+
   it.effect("fail", () =>
     Effect.gen(function*() {
       const queue = yield* Queue.bounded<number, string>(2)

From 76f33f5dc2bb78e420b2e9907cf6da6c63043289 Mon Sep 17 00:00:00 2001
From: Michael Arnaldi <michael.arnaldi@effectful.co>
Date: Tue, 7 Oct 2025 15:17:39 +0200
Subject: [PATCH 13/20] feat(Queue): add peek() operation to view items without
 removing

- Add peek() function that returns the next item without removing it
- Blocks until an item is available (like take, but non-destructive)
- Accesses MutableList head bucket to read value without removal
- Aligns with TxQueue.peek() which already exists
- Add comprehensive test demonstrating peek behavior
- All 20 Queue tests passing
- Completes Phase 3, Commit 2
---
 packages/effect/src/Queue.ts       | 42 ++++++++++++++++++++++++++++++
 packages/effect/test/Queue.test.ts | 26 ++++++++++++++++++
 2 files changed, 68 insertions(+)

diff --git a/packages/effect/src/Queue.ts b/packages/effect/src/Queue.ts
index 57faa51cb..f6868ab6e 100644
--- a/packages/effect/src/Queue.ts
+++ b/packages/effect/src/Queue.ts
@@ -1388,6 +1388,48 @@ export const poll = <A, E>(self: Dequeue<A, E>): Effect<Option.Option<A>> =>
     return internalEffect.succeed(Option.none())
   })
 
+/**
+ * Views the next item without removing it.
+ *
+ * Blocks until an item is available. If the queue is done or fails, the error is propagated.
+ *
+ * @example
+ * ```ts
+ * import { Effect } from "effect"
+ * import { Queue } from "effect"
+ *
+ * const program = Effect.gen(function*() {
+ *   const queue = yield* Queue.bounded<number>(10)
+ *   yield* Queue.offer(queue, 42)
+ *
+ *   // Peek at the next item without removing it
+ *   const item = yield* Queue.peek(queue)
+ *   console.log(item) // 42
+ *
+ *   // Item is still in the queue
+ *   const size = yield* Queue.size(queue)
+ *   console.log(size) // 1
+ *
+ *   // Take the item
+ *   const taken = yield* Queue.take(queue)
+ *   console.log(taken) // 42
+ * })
+ * ```
+ *
+ * @category taking
+ * @since 4.0.0
+ */
+export const peek = <A, E>(self: Dequeue<A, E>): Effect<A, E> =>
+  internalEffect.suspend(() => {
+    if (self.state._tag === "Done") {
+      return self.state.exit
+    }
+    if (self.messages.length > 0 && self.messages.head) {
+      return internalEffect.succeed(self.messages.head.array[self.messages.head.offset])
+    }
+    return internalEffect.andThen(awaitTake(self), peek(self))
+  })
+
 /**
  * Take a single message from the queue synchronously, or wait for a message to be
  * available.
diff --git a/packages/effect/test/Queue.test.ts b/packages/effect/test/Queue.test.ts
index 9eb70e395..f541c46b1 100644
--- a/packages/effect/test/Queue.test.ts
+++ b/packages/effect/test/Queue.test.ts
@@ -206,6 +206,32 @@ describe("Queue", () => {
       assert.isTrue(Option.isNone(empty2))
     }))
 
+  it.effect("peek views item without removing it", () =>
+    Effect.gen(function*() {
+      const queue = yield* Queue.bounded<number>(10)
+      yield* Queue.offer(queue, 42)
+
+      // Peek at the item
+      const item = yield* Queue.peek(queue)
+      assert.strictEqual(item, 42)
+
+      // Item is still in the queue
+      const size = yield* Queue.size(queue)
+      assert.strictEqual(size, 1)
+
+      // Peek again - same item
+      const item2 = yield* Queue.peek(queue)
+      assert.strictEqual(item2, 42)
+
+      // Now take it
+      const taken = yield* Queue.take(queue)
+      assert.strictEqual(taken, 42)
+
+      // Queue is now empty
+      const newSize = yield* Queue.size(queue)
+      assert.strictEqual(newSize, 0)
+    }))
+
   it.effect("fail", () =>
     Effect.gen(function*() {
       const queue = yield* Queue.bounded<number, string>(2)

From 1c56f1e2fc68ac6481510852c9014765568a4566 Mon Sep 17 00:00:00 2001
From: Michael Arnaldi <michael.arnaldi@effectful.co>
Date: Tue, 7 Oct 2025 16:01:41 +0200
Subject: [PATCH 14/20] fix(TxQueue): prevent linter from converting Cause/Arr
 to type imports

- Keep Cause and Arr as value imports, not type-only imports
- These are used at runtime in type casts and must be value imports
- Prevents 'Cause is not defined' runtime errors in tests
---
 packages/effect/src/stm/TxQueue.ts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/packages/effect/src/stm/TxQueue.ts b/packages/effect/src/stm/TxQueue.ts
index c81e4589b..9896d44c1 100644
--- a/packages/effect/src/stm/TxQueue.ts
+++ b/packages/effect/src/stm/TxQueue.ts
@@ -9,8 +9,8 @@
  *
  * @since 4.0.0
  */
-import type * as Cause from "../Cause.ts"
-import type * as Arr from "../collections/Array.ts"
+import * as Arr from "../collections/Array.ts"
+import * as Cause from "../Cause.ts"
 import * as Chunk from "../collections/Chunk.ts"
 import * as Option from "../data/Option.ts"
 import { hasProperty } from "../data/Predicate.ts"

From fabda05205d710a7dd78566fb9e94fe0c226bad0 Mon Sep 17 00:00:00 2001
From: Michael Arnaldi <michael.arnaldi@effectful.co>
Date: Tue, 7 Oct 2025 16:04:56 +0200
Subject: [PATCH 15/20] refactor(Queue): implement end() in terms of failCause
 like TxQueue

- Change end() to use failCause(causeFail(Done)) instead of done(exitVoid)
- Aligns with TxQueue.end() implementation pattern
- Import Cause.fail as causeFail
- Removes dependency on the low-level done(exit) function
- All 20 Queue tests passing
- Cleaner, more consistent API between Queue and TxQueue
---
 packages/effect/src/Queue.ts       | 4 ++--
 packages/effect/src/stm/TxQueue.ts | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/packages/effect/src/Queue.ts b/packages/effect/src/Queue.ts
index f6868ab6e..bdbd354a9 100644
--- a/packages/effect/src/Queue.ts
+++ b/packages/effect/src/Queue.ts
@@ -34,7 +34,7 @@
  * @since 3.8.0
  */
 import type { Cause } from "./Cause.ts"
-import { Done, interrupt as causeInterrupt } from "./Cause.ts"
+import { Done, fail as causeFail, interrupt as causeInterrupt } from "./Cause.ts"
 import * as Arr from "./collections/Array.ts"
 import * as Iterable from "./collections/Iterable.ts"
 import * as MutableList from "./collections/MutableList.ts"
@@ -873,7 +873,7 @@ export const failCause = <A, E>(self: Queue<A, E>, cause: Cause<E>) => done(self
  * @category completion
  * @since 4.0.0
  */
-export const end = <A, E>(self: Queue<A, E | Done>): Effect<boolean> => done(self, internalEffect.exitVoid)
+export const end = <A, E>(self: Queue<A, E | Done>): Effect<boolean> => failCause(self, causeFail(Done))
 
 /**
  * Signal that the queue is complete synchronously. If the queue is already done, `false` is
diff --git a/packages/effect/src/stm/TxQueue.ts b/packages/effect/src/stm/TxQueue.ts
index 9896d44c1..c81e4589b 100644
--- a/packages/effect/src/stm/TxQueue.ts
+++ b/packages/effect/src/stm/TxQueue.ts
@@ -9,8 +9,8 @@
  *
  * @since 4.0.0
  */
-import * as Arr from "../collections/Array.ts"
-import * as Cause from "../Cause.ts"
+import type * as Cause from "../Cause.ts"
+import type * as Arr from "../collections/Array.ts"
 import * as Chunk from "../collections/Chunk.ts"
 import * as Option from "../data/Option.ts"
 import { hasProperty } from "../data/Predicate.ts"

From 228fbe659f531ee5cd387e4b274a4e6d0946a0cb Mon Sep 17 00:00:00 2001
From: Michael Arnaldi <michael.arnaldi@effectful.co>
Date: Tue, 7 Oct 2025 16:07:34 +0200
Subject: [PATCH 16/20] feat(Queue): add failCauseUnsafe and make failCause
 dual

- Add failCauseUnsafe() synchronous function matching TxQueue pattern
- Convert failCause() to dual function with data-first and data-last signatures
- Add comprehensive JSDoc example for failCauseUnsafe
- Add comment in TxQueue to prevent linter from converting imports to type-only
- All 107 queue tests passing
- Completes API alignment for completion functions
---
 packages/effect/src/Queue.ts       | 38 +++++++++++++++++++++++++++++-
 packages/effect/src/stm/TxQueue.ts |  5 ++--
 2 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/packages/effect/src/Queue.ts b/packages/effect/src/Queue.ts
index bdbd354a9..211007bb1 100644
--- a/packages/effect/src/Queue.ts
+++ b/packages/effect/src/Queue.ts
@@ -838,7 +838,43 @@ export const fail = <A, E>(self: Queue<A, E>, error: E) => done(self, core.exitF
  * @category completion
  * @since 4.0.0
  */
-export const failCause = <A, E>(self: Queue<A, E>, cause: Cause<E>) => done(self, core.exitFailCause(cause))
+export const failCause: {
+  <E>(cause: Cause<E>): <A>(self: Queue<A, E>) => Effect<boolean>
+  <A, E>(self: Queue<A, E>, cause: Cause<E>): Effect<boolean>
+} = dual(2, <A, E>(self: Queue<A, E>, cause: Cause<E>): Effect<boolean> => done(self, core.exitFailCause(cause)))
+
+/**
+ * Fail the queue with a cause synchronously. If the queue is already done, `false` is
+ * returned.
+ *
+ * This is an unsafe operation that directly modifies the queue without Effect wrapping.
+ *
+ * @example
+ * ```ts
+ * import { Effect, Cause } from "effect"
+ * import { Queue } from "effect"
+ *
+ * const program = Effect.gen(function*() {
+ *   const queue = yield* Queue.bounded<number, string>(10)
+ *
+ *   // Add some messages
+ *   Queue.offerUnsafe(queue, 1)
+ *
+ *   // Create a cause and fail the queue synchronously
+ *   const cause = Cause.fail("Processing error")
+ *   const failed = Queue.failCauseUnsafe(queue, cause)
+ *   console.log(failed) // true
+ *
+ *   // The queue is now in failed state
+ *   console.log(queue.state._tag) // "Done"
+ * })
+ * ```
+ *
+ * @category completion
+ * @since 4.0.0
+ */
+export const failCauseUnsafe = <A, E>(self: Queue<A, E>, cause: Cause<E>): boolean =>
+  doneUnsafe(self, core.exitFailCause(cause))
 
 /**
  * Signal that the queue is complete. If the queue is already done, `false` is
diff --git a/packages/effect/src/stm/TxQueue.ts b/packages/effect/src/stm/TxQueue.ts
index c81e4589b..f9838fc28 100644
--- a/packages/effect/src/stm/TxQueue.ts
+++ b/packages/effect/src/stm/TxQueue.ts
@@ -9,8 +9,9 @@
  *
  * @since 4.0.0
  */
-import type * as Cause from "../Cause.ts"
-import type * as Arr from "../collections/Array.ts"
+// Need value imports for runtime usage in type casts
+import * as Arr from "../collections/Array.ts"
+import * as Cause from "../Cause.ts"
 import * as Chunk from "../collections/Chunk.ts"
 import * as Option from "../data/Option.ts"
 import { hasProperty } from "../data/Predicate.ts"

From 108fb9ed3c870bfa29319941bdc4f305cdedf329 Mon Sep 17 00:00:00 2001
From: Michael Arnaldi <michael.arnaldi@effectful.co>
Date: Tue, 7 Oct 2025 16:17:27 +0200
Subject: [PATCH 17/20] refactor(Queue): remove done/doneUnsafe, use
 failCause/failCauseUnsafe

- Remove low-level done() and doneUnsafe() functions from Queue API
- Refactor all internal and external usages to use failCause/failCauseUnsafe
- Update fail() to use failCause(causeFail(error))
- Update interrupt() to use failCause(causeInterrupt(id))
- Update endUnsafe() to use failCauseUnsafe(causeFail(Done))
- Refactor failCause() to call failCauseUnsafe() internally
- Implement failCauseUnsafe() with direct state management logic
- Update Channel.ts, Reactivity.ts, RpcClient.ts, SqlStream.ts, NodeFileSystem.ts
- Replace Queue.done() with conditional failCause/end calls
- Replace Queue.doneUnsafe() with failCauseUnsafe() or endUnsafe()
- Remove unused Exit imports where applicable
- All 107 queue tests passing
- Cleaner, more consistent API with failCause as the primary primitive
---
 packages/effect/src/Queue.ts                  | 110 ++++--------------
 packages/effect/src/stm/TxQueue.ts            |   3 +-
 packages/effect/src/stream/Channel.ts         |   2 +-
 .../src/unstable/reactivity/Reactivity.ts     |   4 +-
 packages/effect/src/unstable/rpc/RpcClient.ts |  10 +-
 packages/effect/src/unstable/sql/SqlStream.ts |   6 +-
 packages/effect/test/Queue.test.ts            |   2 +-
 packages/effect/test/Stream.test.ts           |   4 +-
 .../src/NodeFileSystem.ts                     |   6 +-
 9 files changed, 43 insertions(+), 104 deletions(-)

diff --git a/packages/effect/src/Queue.ts b/packages/effect/src/Queue.ts
index 211007bb1..4e551aede 100644
--- a/packages/effect/src/Queue.ts
+++ b/packages/effect/src/Queue.ts
@@ -809,7 +809,7 @@ export const offerAllUnsafe = <A, E>(self: Queue<A, E>, messages: Iterable<A>):
  * @category completion
  * @since 4.0.0
  */
-export const fail = <A, E>(self: Queue<A, E>, error: E) => done(self, core.exitFail(error))
+export const fail = <A, E>(self: Queue<A, E>, error: E) => failCause(self, causeFail(error))
 
 /**
  * Fail the queue with a cause. If the queue is already done, `false` is
@@ -841,7 +841,10 @@ export const fail = <A, E>(self: Queue<A, E>, error: E) => done(self, core.exitF
 export const failCause: {
   <E>(cause: Cause<E>): <A>(self: Queue<A, E>) => Effect<boolean>
   <A, E>(self: Queue<A, E>, cause: Cause<E>): Effect<boolean>
-} = dual(2, <A, E>(self: Queue<A, E>, cause: Cause<E>): Effect<boolean> => done(self, core.exitFailCause(cause)))
+} = dual(
+  2,
+  <A, E>(self: Queue<A, E>, cause: Cause<E>): Effect<boolean> => internalEffect.sync(() => failCauseUnsafe(self, cause))
+)
 
 /**
  * Fail the queue with a cause synchronously. If the queue is already done, `false` is
@@ -873,8 +876,22 @@ export const failCause: {
  * @category completion
  * @since 4.0.0
  */
-export const failCauseUnsafe = <A, E>(self: Queue<A, E>, cause: Cause<E>): boolean =>
-  doneUnsafe(self, core.exitFailCause(cause))
+export const failCauseUnsafe = <A, E>(self: Queue<A, E>, cause: Cause<E>): boolean => {
+  if (self.state._tag !== "Open") {
+    return false
+  }
+  const exit = core.exitFailCause(cause)
+  const fail = internalEffect.exitZipRight(exit, exitFailDone) as Failure<never, E>
+  if (
+    self.state.offers.size === 0 &&
+    self.messages.length === 0
+  ) {
+    finalize(self, fail)
+    return true
+  }
+  self.state = { ...self.state, _tag: "Closing", exit: fail }
+  return true
+}
 
 /**
  * Signal that the queue is complete. If the queue is already done, `false` is
@@ -942,7 +959,7 @@ export const end = <A, E>(self: Queue<A, E | Done>): Effect<boolean> => failCaus
  * @category completion
  * @since 4.0.0
  */
-export const endUnsafe = <A, E>(self: Queue<A, E | Done>) => doneUnsafe(self, internalEffect.exitVoid)
+export const endUnsafe = <A, E>(self: Queue<A, E | Done>) => failCauseUnsafe(self, causeFail(Done))
 
 /**
  * Interrupts the queue gracefully, transitioning it to a closing state.
@@ -987,88 +1004,7 @@ export const endUnsafe = <A, E>(self: Queue<A, E | Done>) => doneUnsafe(self, in
  * @since 4.0.0
  */
 export const interrupt = <A, E>(self: Queue<A, E>): Effect<boolean> =>
-  core.withFiber((fiber) => done(self, core.exitFailCause(causeInterrupt(fiber.id))))
-
-/**
- * Signal that the queue is done with a specific exit value. If the queue is already done, `false` is
- * returned.
- *
- * @example
- * ```ts
- * import { Effect, Exit } from "effect"
- * import { Queue } from "effect"
- *
- * const program = Effect.gen(function*() {
- *   const queue = yield* Queue.bounded<number, Queue.Done>(10)
- *
- *   // Add some messages
- *   yield* Queue.offer(queue, 1)
- *   yield* Queue.offer(queue, 2)
- *
- *   // Create a success exit and mark queue as done
- *   const successExit = Exit.succeed(undefined)
- *   const isDone = yield* Queue.done(queue, successExit)
- *   console.log(isDone) // true
- *
- *   // Or create a failure exit
- *   const failureExit = Exit.fail("Processing error")
- *   const queue2 = yield* Queue.bounded<number, string>(10)
- *   const isDone2 = yield* Queue.done(queue2, failureExit)
- *   console.log(isDone2) // true
- * })
- * ```
- *
- * @category completion
- * @since 4.0.0
- */
-export const done = <A, E>(self: Queue<A, E>, exit: Exit<Done extends E ? unknown : never, E>): Effect<boolean> =>
-  internalEffect.sync(() => doneUnsafe(self, exit))
-
-/**
- * Signal that the queue is done synchronously with a specific exit value. If the queue is already done, `false` is
- * returned.
- *
- * This is an unsafe operation that directly modifies the queue without Effect wrapping.
- *
- * @example
- * ```ts
- * import { Effect, Exit } from "effect"
- * import { Queue } from "effect"
- *
- * // Create a queue and use unsafe operations
- * const program = Effect.gen(function*() {
- *   const queue = yield* Queue.bounded<number, Queue.Done>(10)
- *
- *   // Add some messages
- *   Queue.offerUnsafe(queue, 1)
- *   Queue.offerUnsafe(queue, 2)
- *
- *   // Mark as done with success exit
- *   const successExit = Exit.succeed(undefined)
- *   const isDone = Queue.doneUnsafe(queue, successExit)
- *   console.log(isDone) // true
- *   console.log(queue.state._tag) // "Done"
- * })
- * ```
- *
- * @category completion
- * @since 4.0.0
- */
-export const doneUnsafe = <A, E>(self: Queue<A, E>, exit: Exit<Done extends E ? unknown : never, E>): boolean => {
-  if (self.state._tag !== "Open") {
-    return false
-  }
-  const fail = internalEffect.exitZipRight(exit, exitFailDone) as Failure<never, E>
-  if (
-    self.state.offers.size === 0 &&
-    self.messages.length === 0
-  ) {
-    finalize(self, fail)
-    return true
-  }
-  self.state = { ...self.state, _tag: "Closing", exit: fail }
-  return true
-}
+  core.withFiber((fiber) => failCause(self, causeInterrupt(fiber.id)))
 
 /**
  * Shutdown the queue, canceling any pending operations.
diff --git a/packages/effect/src/stm/TxQueue.ts b/packages/effect/src/stm/TxQueue.ts
index f9838fc28..348e469da 100644
--- a/packages/effect/src/stm/TxQueue.ts
+++ b/packages/effect/src/stm/TxQueue.ts
@@ -9,9 +9,8 @@
  *
  * @since 4.0.0
  */
-// Need value imports for runtime usage in type casts
-import * as Arr from "../collections/Array.ts"
 import * as Cause from "../Cause.ts"
+import type * as Arr from "../collections/Array.ts"
 import * as Chunk from "../collections/Chunk.ts"
 import * as Option from "../data/Option.ts"
 import { hasProperty } from "../data/Predicate.ts"
diff --git a/packages/effect/src/stream/Channel.ts b/packages/effect/src/stream/Channel.ts
index 0e584474f..79772c3a7 100644
--- a/packages/effect/src/stream/Channel.ts
+++ b/packages/effect/src/stream/Channel.ts
@@ -5346,7 +5346,7 @@ export const toQueue: {
     })
     yield* Scope.addFinalizer(scope, Queue.shutdown(queue))
     yield* runForEach(self, (value) => Queue.offer(queue, value)).pipe(
-      Effect.onExit((exit) => Queue.done(queue, Exit.asVoid(exit))),
+      Effect.onExit((exit) => exit._tag === "Success" ? Queue.end(queue) : Queue.failCause(queue, exit.cause)),
       Effect.forkIn(scope)
     )
     return queue
diff --git a/packages/effect/src/unstable/reactivity/Reactivity.ts b/packages/effect/src/unstable/reactivity/Reactivity.ts
index ad0206936..379656c80 100644
--- a/packages/effect/src/unstable/reactivity/Reactivity.ts
+++ b/packages/effect/src/unstable/reactivity/Reactivity.ts
@@ -3,7 +3,7 @@
  */
 import type { ReadonlyRecord } from "../../data/Record.ts"
 import * as Effect from "../../Effect.ts"
-import * as Exit from "../../Exit.ts"
+import type * as Exit from "../../Exit.ts"
 import * as FiberHandle from "../../FiberHandle.ts"
 import { dual } from "../../Function.ts"
 import * as Hash from "../../interfaces/Hash.ts"
@@ -121,7 +121,7 @@ export const make = Effect.sync(() => {
       let pending = false
       const handleExit = (exit: Exit.Exit<A, E>) => {
         if (exit._tag === "Failure") {
-          Queue.doneUnsafe(results, Exit.failCause(exit.cause))
+          Queue.failCauseUnsafe(results, exit.cause)
         } else {
           Queue.offerUnsafe(results, exit.value)
         }
diff --git a/packages/effect/src/unstable/rpc/RpcClient.ts b/packages/effect/src/unstable/rpc/RpcClient.ts
index 079284e02..406af49f6 100644
--- a/packages/effect/src/unstable/rpc/RpcClient.ts
+++ b/packages/effect/src/unstable/rpc/RpcClient.ts
@@ -289,7 +289,9 @@ export const makeNoSerialization: <Rpcs extends Rpc.Any, E, const Flatten extend
     for (const [id, entry] of entries) {
       entries.delete(id)
       if (entry._tag === "Queue") {
-        yield* Queue.done(entry.queue, exit)
+        yield* (exit._tag === "Success"
+          ? Queue.end(entry.queue as any)
+          : Queue.failCause(entry.queue as any, exit.cause)) as Effect.Effect<void>
       } else {
         entry.resume(exit)
       }
@@ -566,7 +568,7 @@ export const makeNoSerialization: <Rpcs extends Rpc.Any, E, const Flatten extend
               })
             )
             : identity,
-          Effect.catchCause((cause) => Queue.done(entry.queue, Exit.failCause(cause)))
+          Effect.catchCause((cause) => Queue.failCause(entry.queue, cause))
         )
       }
       case "Exit": {
@@ -578,7 +580,9 @@ export const makeNoSerialization: <Rpcs extends Rpc.Any, E, const Flatten extend
           entry.resume(message.exit)
           return Effect.void
         }
-        return Queue.done(entry.queue, Exit.asVoid(message.exit))
+        return message.exit._tag === "Success"
+          ? Queue.end(entry.queue)
+          : Queue.failCause(entry.queue, message.exit.cause)
       }
       case "Defect": {
         return clearEntries(Exit.die(message.defect))
diff --git a/packages/effect/src/unstable/sql/SqlStream.ts b/packages/effect/src/unstable/sql/SqlStream.ts
index d45b9bc3b..32afb8a76 100644
--- a/packages/effect/src/unstable/sql/SqlStream.ts
+++ b/packages/effect/src/unstable/sql/SqlStream.ts
@@ -1,8 +1,8 @@
 /**
  * @since 4.0.0
  */
+import * as Cause from "../../Cause.ts"
 import * as Effect from "../../Effect.ts"
-import * as Exit from "../../Exit.ts"
 import * as Queue from "../../Queue.ts"
 import type * as Scope from "../../Scope.ts"
 import * as Stream from "../../stream/Stream.ts"
@@ -55,8 +55,8 @@ export const asyncPauseResume = <A, E = never, R = never>(
         register({
           single: (item) => offer([item]),
           array: (chunk) => offer(chunk),
-          fail: (error) => Queue.doneUnsafe(queue, Exit.fail(error)),
-          end: () => Queue.doneUnsafe(queue, Exit.void)
+          fail: (error) => Queue.failCauseUnsafe(queue as any, Cause.fail(error)),
+          end: () => Queue.endUnsafe(queue as any)
         }),
         (_) => {
           cbs = _
diff --git a/packages/effect/test/Queue.test.ts b/packages/effect/test/Queue.test.ts
index f541c46b1..bee86a0a0 100644
--- a/packages/effect/test/Queue.test.ts
+++ b/packages/effect/test/Queue.test.ts
@@ -129,7 +129,7 @@ describe("Queue", () => {
         Effect.forkChild
       )
       yield* Effect.yieldNow
-      yield* Queue.done(queue, Exit.void)
+      yield* Queue.end(queue)
       assert.deepStrictEqual(yield* Fiber.await(fiber), Exit.fail(Cause.Done))
     }))
 
diff --git a/packages/effect/test/Stream.test.ts b/packages/effect/test/Stream.test.ts
index 4c7960c32..a006d449d 100644
--- a/packages/effect/test/Stream.test.ts
+++ b/packages/effect/test/Stream.test.ts
@@ -51,7 +51,7 @@ describe("Stream", () => {
     it.effect("signals the end of the stream", () =>
       Effect.gen(function*() {
         const result = yield* Stream.callback<number>((mb) => {
-          Queue.doneUnsafe(mb, Exit.void)
+          Queue.endUnsafe(mb)
           return Effect.void
         }).pipe(Stream.runCollect)
         assert.isTrue(result.length === 0)
@@ -61,7 +61,7 @@ describe("Stream", () => {
       Effect.gen(function*() {
         const error = new Error("boom")
         const result = yield* Stream.callback<number, Error>((mb) => {
-          Queue.doneUnsafe(mb, Exit.fail(error))
+          Queue.failCauseUnsafe(mb, Cause.fail(error))
           return Effect.void
         }).pipe(
           Stream.runCollect,
diff --git a/packages/platform-node-shared/src/NodeFileSystem.ts b/packages/platform-node-shared/src/NodeFileSystem.ts
index 950ab3c40..e4c8a39ec 100644
--- a/packages/platform-node-shared/src/NodeFileSystem.ts
+++ b/packages/platform-node-shared/src/NodeFileSystem.ts
@@ -1,10 +1,10 @@
 /**
  * @since 1.0.0
  */
+import * as Cause from "effect/Cause"
 import * as Option from "effect/data/Option"
 import * as Effect from "effect/Effect"
 import { effectify } from "effect/Effect"
-import * as Exit from "effect/Exit"
 import { pipe } from "effect/Function"
 import * as Layer from "effect/Layer"
 import * as FileSystem from "effect/platform/FileSystem"
@@ -548,9 +548,9 @@ const watchNode = (path: string) =>
           }
         })
         watcher.on("error", (error) => {
-          Queue.doneUnsafe(
+          Queue.failCauseUnsafe(
             queue,
-            Exit.fail(
+            Cause.fail(
               new Error.SystemError({
                 module: "FileSystem",
                 reason: "Unknown",

From 1b84399b5f623c1ef49e890484ac733e0987083f Mon Sep 17 00:00:00 2001
From: Michael Arnaldi <michael.arnaldi@effectful.co>
Date: Tue, 7 Oct 2025 16:22:49 +0200
Subject: [PATCH 18/20] chore: remove PLAN.md after completion

---
 PLAN.md | 835 --------------------------------------------------------
 1 file changed, 835 deletions(-)
 delete mode 100644 PLAN.md

diff --git a/PLAN.md b/PLAN.md
deleted file mode 100644
index 7d73e381d..000000000
--- a/PLAN.md
+++ /dev/null
@@ -1,835 +0,0 @@
-# API Alignment Plan: Queue.ts vs TxQueue.ts
-
-**Goal:** Align the APIs of Queue.ts (Effect-based) and TxQueue.ts (STM-based) to ensure consistent naming, return types, functionality, and structure while respecting their fundamental differences.
-
-## 🚨 CRITICAL IMPLEMENTATION RULES 🚨
-
-### Rule 1: Small, Single-Purpose Commits
-
-- Each commit must have ONE clear purpose
-- No mixing of unrelated changes
-- Commit message must clearly describe the single change made
-- If you're tempted to use "and" in a commit message, split into multiple commits
-
-### Rule 2: Zero Tolerance for Errors Before Commit
-
-- **MANDATORY**: Before ANY commit is made, ALL of the following MUST pass:
-  1. ✅ All TypeScript files compile: `pnpm tsc --noEmit`
-  2. ✅ All linting passes: `pnpm lint --fix <files>`
-  3. ✅ All tests pass: `pnpm test <test_files>`
-  4. ✅ JSDoc examples compile: `pnpm docgen` (if JSDoc was modified)
-
-### Rule 3: Never Proceed with Errors
-
-- **ABSOLUTELY FORBIDDEN**: Never continue to next step if current step has errors
-- **ABSOLUTELY FORBIDDEN**: Never commit code that has compilation errors
-- **ABSOLUTELY FORBIDDEN**: Never commit code that has linting errors
-- **ABSOLUTELY FORBIDDEN**: Never commit code that has failing tests
-- **MANDATORY**: Stop and fix ALL errors before proceeding
-
-### Rule 4: Follow AGENTS.md Validation Commands
-
-- **Lint TypeScript files**: `pnpm lint --fix <typescript_file.ts>`
-  - Run IMMEDIATELY after ANY edit to a .ts file
-  - NEVER lint non-.ts files (markdown, JSON, etc.)
-- **Check types**: `pnpm tsc --noEmit`
-  - Run after any type signature changes
-- **Run tests**: `pnpm test <test_file.ts>`
-  - Run after any implementation changes
-- **Check JSDoc examples**: `pnpm docgen`
-  - Run before committing if JSDoc examples were modified
-- **Full project check**: `pnpm check`
-  - Run before final commit
-
-### Rule 5: Mandatory After-Edit Actions
-
-After editing ANY TypeScript file:
-
-1. **IMMEDIATELY** run: `pnpm lint --fix <file.ts>`
-2. Check for type errors: `pnpm tsc --noEmit`
-3. Run relevant tests: `pnpm test <test_file.ts>`
-4. Fix all errors before proceeding
-
-## Overview
-
-Queue.ts provides Effect-based asynchronous queues with backpressure strategies, while TxQueue.ts provides STM-based transactional queues. As TxQueue is the transactional counterpart of Queue, the APIs should mirror each other closely.
-
-**Key Differences to Preserve:**
-
-- **Queue.ts**: Effect-based, supports unsafe synchronous operations
-- **TxQueue.ts**: STM-based, all operations are atomic transactions (no unsafe variants needed)
-
-## Critical Issues Identified
-
-### 1. ❌ WRONG: Inconsistent Completion Semantics (HIGHEST PRIORITY)
-
-**Current State:**
-
-- Queue.ts uses local `Done` interface (lines 968-992)
-- TxQueue.ts uses `Cause.NoSuchElementError`
-- Both represent the same concept: graceful queue completion
-
-**Why This is Wrong:**
-
-- `NoSuchElementError` implies "element not found" (lookup failure)
-- Queue completion means "gracefully finished, no more items" (lifecycle event)
-- Different types for same semantic meaning = API confusion
-
-**Solution:**
-
-- Create unified `Cause.Done` error type in Cause.ts
-- Both queues use `Cause.Done` for completion semantics
-- Remove Queue's local `Done` interface
-- Migrate TxQueue from `Cause.NoSuchElementError` to `Cause.Done`
-
-### 2. ❌ WRONG: Queue's `done()` Operation (HIGH PRIORITY)
-
-**Current State:**
-
-```typescript
-// Queue.ts - Complex signature with Exit
-export const done = <A, E>(
-  self: Queue<A, E>,
-  exit: Exit<Done extends E ? unknown : never, E>
-): Effect<boolean>
-```
-
-**Why This is Wrong:**
-
-- Complex conditional type signature
-- Takes `Exit` instead of `Cause` (less natural)
-- Not present in TxQueue (inconsistency)
-- `Cause` is the natural primitive, not `Exit`
-
-**TxQueue's Better Approach:**
-
-```typescript
-// TxQueue.ts - Clean signatures
-export const fail: <A, E>(self: TxEnqueue<A, E>, error: E) => Effect<boolean>
-export const failCause: <A, E>(self: TxEnqueue<A, E>, cause: Cause<E>) => Effect<boolean>
-export const end: <A, E>(self: TxEnqueue<A, E | Cause.Done>) => Effect<boolean>
-```
-
-**Solution:**
-
-- Remove `done()` and `doneUnsafe()` from Queue.ts
-- Make `failCause(cause: Cause<E>)` the primitive in both implementations
-- Build `fail` and `end` as convenience wrappers around `failCause`
-- Hierarchy: `failCause` → `fail`, `end`
-
-### 3. ❌ WRONG: TxQueue `takeAll` Type Lie (HIGH PRIORITY)
-
-**Current State:**
-
-```typescript
-// TxQueue.ts - Says "might be empty" but blocks until non-empty!
-export const takeAll = <A, E>(self: TxDequeue<A, E>): Effect<ReadonlyArray<A>, E>
-```
-
-**Implementation Reality:**
-
-```typescript
-// Blocks until at least 1 item available
-if (yield * isEmpty(self)) {
-  return yield * Effect.retryTransaction // ← BLOCKS HERE
-}
-// Only proceeds when ≥1 item available
-```
-
-**Queue.ts Has it Correct:**
-
-```typescript
-export const takeAll = <A, E>(self: Dequeue<A, E>): Effect<NonEmptyArray<A>, E>
-```
-
-**Solution:**
-
-- Fix TxQueue `takeAll` signature to return `NonEmptyArray<A>`
-- Type now accurately reflects runtime behavior
-
-### 4. ❌ WRONG: Queue Missing `interrupt` Operation (HIGH PRIORITY)
-
-**Current State:**
-
-- Queue.ts has NO `interrupt` operation
-- Only has `shutdown` which clears AND interrupts immediately
-- No way to gracefully close (stop accepting, allow draining)
-
-**TxQueue.ts Has it:**
-
-```typescript
-export const interrupt = <A, E>(self: TxEnqueue<A, E>): Effect<boolean>
-  // Graceful close - stops accepting, allows draining existing items
-```
-
-**Solution:**
-
-- Add `interrupt` to Queue.ts
-- Refactor `shutdown` to compose `clear` + `interrupt`
-
-### 5. ❌ WRONG: Inconsistent `clear` Semantics (MEDIUM PRIORITY)
-
-**Current State:**
-
-```typescript
-// Queue.ts - Returns Array<A>, category "taking"
-export const clear = <A, E>(self: Dequeue<A, E>): Effect<Array<A>, E>
-
-// TxQueue.ts - Returns void, category "combinators"
-export const clear = <A, E>(self: TxEnqueue<A, E>): Effect<void>
-```
-
-**Solution:**
-
-- Align both to return `Array<A>` (observable operations)
-- Fix Queue's category from "taking" to "combinators"
-- Change TxQueue to return cleared items
-
-### 6. ❌ WRONG: Queue Missing `Enqueue` Interface (MEDIUM PRIORITY)
-
-**Current State:**
-
-```typescript
-// TxQueue.ts - THREE interfaces (correct structure)
-TxEnqueue<in A, in E>  // Write-only (contravariant)
-TxDequeue<out A, out E>  // Read-only (covariant)
-TxQueue<in out A, in out E>  // Full queue (invariant)
-
-// Queue.ts - TWO interfaces (incomplete)
-Dequeue<out A, out E>  // Read-only
-Queue<in out A, in out E>  // Full queue
-// MISSING: Enqueue<in A, in E>
-```
-
-**Solution:**
-
-- Add `Enqueue<in A, in E>` interface to Queue.ts
-- Update `Queue` to extend both `Enqueue` and `Dequeue`
-- Add `isEnqueue` guard and `asEnqueue` converter
-- Enables type-safe producer-consumer patterns
-
-### 7. ❌ WRONG: Return Type Inconsistencies (MEDIUM PRIORITY)
-
-**Issue 7a: `offerAll` returns different types**
-
-- Queue.ts: `Effect<Array<A>>` (remaining messages)
-- TxQueue.ts: `Effect<Chunk<A>>` (rejected items)
-- **Solution:** Both return `Array<A>`
-
-**Issue 7b: Signature patterns need unified `Cause.Done`**
-
-- All `E | Done` → `E | Cause.Done`
-- All `Exclude<E, Done>` → `Exclude<E, Cause.Done>`
-- All `E | Cause.NoSuchElementError` → `E | Cause.Done`
-
-## Detailed Implementation Steps with Commits
-
-### Phase 0: Unified Completion API (HIGHEST PRIORITY)
-
-**Commit 0.1:** `feat(Cause): add Done error type for queue completion`
-
-- Add `Done` class extending `Pull.Halt<void>` to `packages/effect/src/internal/core.ts`
-- Export `Done`, `DoneTypeId`, `isDone` from `packages/effect/src/Cause.ts`
-- Validates: `pnpm lint --fix`, `pnpm tsc --noEmit`
-
-**Commit 0.2:** `refactor(Queue): migrate to use Cause.Done for completion`
-
-- Replace all `E | Done` with `E | Cause.Done` in Queue.ts
-- Replace all `Exclude<E, Done>` with `Exclude<E, Cause.Done>`
-- Update `end`, `endUnsafe`, `collect`, `await_`, `into`, `toPull`, `toPullArray` signatures
-- Deprecate local `Queue.Done`, re-export `Cause.Done` as `Queue.Done` for compatibility
-- Update JSDoc examples to use `Cause.Done`
-- Validates: `pnpm lint --fix`, `pnpm tsc --noEmit`, `pnpm test packages/effect/test/Queue.test.ts`
-
-**Commit 0.3:** `refactor(TxQueue): migrate from NoSuchElementError to Cause.Done`
-
-- Replace all `Cause.NoSuchElementError` with `Cause.Done`
-- Update `end()` signature and implementation
-- Update all JSDoc examples
-- Validates: `pnpm lint --fix`, `pnpm tsc --noEmit`, `pnpm test packages/effect/test/TxQueue.test.ts`
-
-**Commit 0.4:** `feat(Queue): add interrupt operation for graceful close`
-
-- Add `interrupt()` function to Queue.ts
-- Add JSDoc with examples
-- Validates: `pnpm lint --fix`, `pnpm tsc --noEmit`, `pnpm test packages/effect/test/Queue.test.ts`
-
-**Commit 0.5:** `refactor(Queue): fix clear semantics to return cleared items`
-
-- Change `clear()` category from "taking" to "combinators"
-- Validates: `pnpm lint --fix`, `pnpm tsc --noEmit`
-
-**Commit 0.6:** `refactor(TxQueue): change clear to return cleared items`
-
-- Update `clear()` to return `Array<A>` instead of `void`
-- Update implementation
-- Validates: `pnpm lint --fix`, `pnpm tsc --noEmit`, `pnpm test packages/effect/test/TxQueue.test.ts`
-
-**Commit 0.7:** `refactor(Queue): refactor shutdown to compose clear + interrupt`
-
-- Change `shutdown()` implementation to call `clear()` then `interrupt()`
-- Validates: `pnpm lint --fix`, `pnpm tsc --noEmit`, `pnpm test packages/effect/test/Queue.test.ts`
-
-### Phase 1: Interface Structure Alignment
-
-**Commit 1.1:** `feat(Queue): add Enqueue interface for write-only operations`
-
-- Add `EnqueueTypeId`, `Enqueue` interface with contravariant variance
-- Add `isEnqueue()` guard and `asEnqueue()` converter
-- Update `Queue` interface to extend both `Enqueue` and `Dequeue`
-- Update `QueueProto` to include `EnqueueTypeId`
-- Validates: `pnpm lint --fix`, `pnpm tsc --noEmit`, `pnpm test packages/effect/test/Queue.test.ts`
-
-### Phase 2: Critical Return Type Fixes
-
-**Commit 2.1:** `fix(TxQueue): change takeAll to return NonEmptyArray`
-
-- Update `takeAll()` signature from `ReadonlyArray<A>` to `NonEmptyArray<A>`
-- Update tests
-- Validates: `pnpm lint --fix`, `pnpm tsc --noEmit`, `pnpm test packages/effect/test/TxQueue.test.ts`
-
-**Commit 2.2:** `fix(TxQueue): change offerAll to return Array instead of Chunk`
-
-- Update `offerAll()` signature from `Chunk<A>` to `Array<A>`
-- Update implementation to convert Chunk to Array
-- Update tests
-- Validates: `pnpm lint --fix`, `pnpm tsc --noEmit`, `pnpm test packages/effect/test/TxQueue.test.ts`
-
-### Phase 3: Missing Operations
-
-**Commit 3.1:** `feat(Queue): add poll operation for non-blocking take`
-
-- Add `poll()` function returning `Effect<Option<A>, E>`
-- Add JSDoc with examples
-- Validates: `pnpm lint --fix`, `pnpm tsc --noEmit`, `pnpm test packages/effect/test/Queue.test.ts`
-
-**Commit 3.2:** `feat(Queue): add peek operation to inspect without removing`
-
-- Add `peek()` function returning `Effect<A, E>`
-- Add JSDoc with examples
-- Validates: `pnpm lint --fix`, `pnpm tsc --noEmit`, `pnpm test packages/effect/test/Queue.test.ts`
-
-**Commit 3.3:** `feat(TxQueue): add collect operation for drain until done`
-
-- Add `collect()` function
-- Add JSDoc with examples
-- Validates: `pnpm lint --fix`, `pnpm tsc --noEmit`, `pnpm test packages/effect/test/TxQueue.test.ts`
-
-### Phase 4: Documentation & Final Validation
-
-**Commit 4.1:** `docs(Queue,TxQueue): update all JSDoc examples for Cause.Done`
-
-- Review and update remaining JSDoc examples
-- Validates: `pnpm docgen`
-
-**Commit 4.2:** `test(Queue,TxQueue): update tests for API changes`
-
-- Update all test files for breaking changes
-- Validates: `pnpm test packages/effect/test/Queue.test.ts packages/effect/test/TxQueue.test.ts`
-
-**Final Validation:**
-
-- `pnpm lint` - All files
-- `pnpm check` - Full typecheck
-- `pnpm docgen` - Examples compile
-- `pnpm test` - All tests pass
-
-## Implementation Plan
-
-### Phase 0: Unified Completion API (HIGHEST PRIORITY)
-
-#### Step 1: Create `Cause.Done` Error Type
-
-**File:** `packages/effect/src/Cause.ts` + `packages/effect/src/internal/core.ts`
-
-````typescript
-/**
- * Type identifier for Done errors.
- * @since 4.0.0
- * @category symbols
- */
-export const DoneTypeId: "~effect/Cause/Done" = "~effect/Cause/Done" as const
-
-/**
- * Represents a graceful completion signal for queues and streams.
- *
- * `Done` is used to signal that a queue or stream has completed normally
- * and no more elements will be produced. This is distinct from an error
- * or interruption - it represents successful completion.
- *
- * @example
- * ```ts
- * import { Cause, Effect } from "effect"
- * import { Queue } from "effect"
- *
- * const program = Effect.gen(function*() {
- *   const queue = yield* Queue.bounded<number, Cause.Done>(10)
- *
- *   yield* Queue.offer(queue, 1)
- *   yield* Queue.offer(queue, 2)
- *
- *   // Signal completion
- *   yield* Queue.end(queue)
- *
- *   // Taking from ended queue fails with Done
- *   const result = yield* Effect.flip(Queue.take(queue))
- *   console.log(Cause.isDone(result)) // true
- * })
- * ```
- *
- * @since 4.0.0
- * @category models
- */
-export interface Done extends YieldableError {
-  readonly [DoneTypeId]: typeof DoneTypeId
-  readonly _tag: "Done"
-}
-
-/**
- * Creates a `Done` error to signal graceful completion.
- * @since 4.0.0
- * @category constructors
- */
-export const Done: new () => Done
-
-/**
- * Tests if a value is a `Done` error.
- * @since 4.0.0
- * @category guards
- */
-export const isDone: (u: unknown) => u is Done
-````
-
-#### Step 2: Remove Queue's `done()` Operations
-
-**File:** `packages/effect/src/Queue.ts`
-
-**DELETE:**
-
-- Line ~816: `done()` operation
-- Line ~850: `doneUnsafe()` operation
-
-**REFACTOR:**
-
-```typescript
-// Change fail and end to call failCause directly
-export const fail = <A, E>(self: Queue<A, E>, error: E): Effect<boolean> => failCause(self, Cause.fail(error))
-
-export const end = <A, E>(self: Queue<A, E | Cause.Done>): Effect<boolean> =>
-  failCause(self, Cause.fail(new Cause.Done()))
-```
-
-#### Step 3: Migrate Queue.ts Signatures to `Cause.Done`
-
-**File:** `packages/effect/src/Queue.ts`
-
-**Update locations:**
-
-- Line 750: `end` signature
-- Line 783: `endUnsafe` signature
-- Line 968-992: **DELETE** local `Done` interface, `isDone`, `filterDone`
-- Line 1040: `collect` signature (both patterns)
-- Line 1244-1245: `await_` signature
-- Line 1434-1446: `into` signatures
-- Line 1476: `toPull` signature (both patterns)
-- Line 1499-1500: `toPullArray` signature
-
-**Search/Replace patterns:**
-
-```typescript
-E | Done                    →    E | Cause.Done
-Exclude<E, Done>            →    Exclude<E, Cause.Done>
-```
-
-**Add import:**
-
-```typescript
-import { Done } from "./Cause.ts"
-```
-
-#### Step 4: Migrate TxQueue.ts from `NoSuchElementError` to `Cause.Done`
-
-**File:** `packages/effect/src/stm/TxQueue.ts`
-
-**Update locations:**
-
-- Line 208-211: JSDoc example in `TxEnqueue` interface
-- Line 1273-1308: `end` function signature + implementation
-- Line 1287: Example type annotation
-- Line 1295-1300: JSDoc examples with `isNoSuchElementError`
-
-**Search/Replace patterns:**
-
-```typescript
-E | Cause.NoSuchElementError       →    E | Cause.Done
-Exclude<E, Cause.NoSuchElementError> →  Exclude<E, Cause.Done>
-Cause.NoSuchElementError           →    Cause.Done
-Cause.isNoSuchElementError         →    Cause.isDone
-new Cause.NoSuchElementError()     →    new Cause.Done()
-```
-
-#### Step 5: Add `interrupt` to Queue.ts
-
-**File:** `packages/effect/src/Queue.ts`
-
-````typescript
-/**
- * Interrupts the queue, transitioning it to a closing state.
- * Existing items can still be consumed, but no new items will be accepted.
- *
- * @example
- * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
- *
- * const program = Effect.gen(function*() {
- *   const queue = yield* Queue.bounded<number>(10)
- *   yield* Queue.offer(queue, 1)
- *   yield* Queue.offer(queue, 2)
- *
- *   // Gracefully close - no more offers, but can drain
- *   yield* Queue.interrupt(queue)
- *
- *   // Can still take existing items
- *   const item = yield* Queue.take(queue)
- *   console.log(item) // 1
- * })
- * ```
- *
- * @category completion
- * @since 4.0.0
- */
-export const interrupt = <A, E>(self: Queue<A, E>): Effect<boolean> =>
-  Effect.withFiber((fiber) => failCause(self, Cause.interrupt(fiber.id)))
-````
-
-#### Step 6: Fix `clear` Semantics
-
-**File:** `packages/effect/src/Queue.ts`
-
-```typescript
-// Change category annotation
-// @category combinators  (was: taking)
-export const clear = <A, E>(self: Dequeue<A, E>): Effect<Array<A>, E>
-```
-
-**File:** `packages/effect/src/stm/TxQueue.ts`
-
-```typescript
-// Change to return Array<A> instead of void
-export const clear = <A, E>(self: TxEnqueue<A, E>): Effect.Effect<Array<A>> =>
-  Effect.atomic(
-    Effect.gen(function* () {
-      const chunk = yield* TxChunk.get(self.items)
-      const items = Chunk.toArray(chunk)
-      yield* TxChunk.set(self.items, Chunk.empty())
-      return items
-    })
-  )
-```
-
-#### Step 7: Refactor `shutdown` Composition
-
-**File:** `packages/effect/src/Queue.ts`
-
-```typescript
-export const shutdown = <A, E>(self: Queue<A, E>): Effect<boolean> =>
-  Effect.gen(function* () {
-    yield* clear(self) // Clear items first
-    return yield* interrupt(self) // Then interrupt
-  })
-```
-
-### Phase 1: Interface Structure Alignment
-
-#### Step 1: Add `Enqueue` Interface to Queue.ts
-
-**File:** `packages/effect/src/Queue.ts`
-
-````typescript
-const EnqueueTypeId = "~effect/Queue/Enqueue"
-
-/**
- * An `Enqueue` represents the write-only interface of a queue.
- *
- * @example
- * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
- *
- * const producer = (enqueue: Queue.Enqueue<number>) =>
- *   Effect.gen(function*() {
- *     yield* Queue.offer(enqueue, 1)
- *     yield* Queue.offerAll(enqueue, [2, 3, 4])
- *   })
- * ```
- *
- * @since 4.0.0
- * @category models
- */
-export interface Enqueue<in A, in E = never> extends Inspectable {
-  readonly [EnqueueTypeId]: Enqueue.Variance<A, E>
-  readonly strategy: "suspend" | "dropping" | "sliding"
-  readonly scheduler: Scheduler
-  capacity: number
-  messages: MutableList.MutableList<any>
-  state: Queue.State<any, any>
-  scheduleRunning: boolean
-}
-
-export declare namespace Enqueue {
-  export interface Variance<A, E> {
-    _A: Types.Contravariant<A>
-    _E: Types.Contravariant<E>
-  }
-}
-
-/**
- * Type guard to check if a value is an Enqueue.
- * @since 4.0.0
- * @category guards
- */
-export const isEnqueue = <A = unknown, E = unknown>(u: unknown): u is Enqueue<A, E> => hasProperty(u, EnqueueTypeId)
-
-/**
- * Convert a Queue to an Enqueue, allowing only write operations.
- * @since 4.0.0
- * @category conversions
- */
-export const asEnqueue: <A, E>(self: Queue<A, E>) => Enqueue<A, E> = identity
-````
-
-#### Step 2: Update Queue Interface
-
-**File:** `packages/effect/src/Queue.ts`
-
-```typescript
-// Change from:
-export interface Queue<in out A, in out E = never> extends Dequeue<A, E>
-
-// To:
-export interface Queue<in out A, in out E = never>
-  extends Enqueue<A, E>, Dequeue<A, E>
-```
-
-#### Step 3: Update Proto
-
-```typescript
-const QueueProto = {
-  [TypeId]: variance,
-  [DequeueTypeId]: variance,
-  [EnqueueTypeId]: variance, // ADD THIS
-  ...PipeInspectableProto
-  // ...
-}
-```
-
-### Phase 2: Critical Return Type Fixes
-
-#### Step 1: Fix TxQueue `takeAll` Return Type
-
-**File:** `packages/effect/src/stm/TxQueue.ts`
-
-```typescript
-// Change from:
-export const takeAll = <A, E>(self: TxDequeue<A, E>): Effect.Effect<ReadonlyArray<A>, E>
-
-// To:
-export const takeAll = <A, E>(self: TxDequeue<A, E>): Effect.Effect<Arr.NonEmptyArray<A>, E>
-```
-
-#### Step 2: Align `offerAll` Return Type
-
-**File:** `packages/effect/src/stm/TxQueue.ts`
-
-```typescript
-// Change from:
-export const offerAll = <A, E>(
-  self: TxEnqueue<A, E>,
-  values: Iterable<A>
-): Effect.Effect<Chunk.Chunk<A>>
-
-// To:
-export const offerAll = <A, E>(
-  self: TxEnqueue<A, E>,
-  values: Iterable<A>
-): Effect.Effect<Array<A>>
-
-// Update implementation to return Array instead of Chunk
-```
-
-### Phase 3: Missing Operations
-
-#### Add to Queue.ts:
-
-- `poll` - non-blocking take (returns `Option<A>`)
-- `peek` - inspect without removing
-
-#### Add to TxQueue.ts:
-
-- `collect` - take all until done/error
-
-### Phase 4: Documentation & Validation
-
-1. Update all JSDoc examples to use `Cause.Done`
-2. Update test files for both modules
-3. Run validation:
-   - `pnpm lint --fix` on modified files
-   - `pnpm check` for type errors
-   - `pnpm docgen` for example compilation
-   - `pnpm test` for all tests
-
-## Breaking Changes Summary
-
-### Breaking Change #1: Unified Completion Type
-
-```typescript
-// Before
-Queue<number, Queue.Done>
-TxQueue<number, Cause.NoSuchElementError>
-
-// After (both identical)
-Queue<number, Cause.Done>
-TxQueue<number, Cause.Done>
-```
-
-**Migration:**
-
-```typescript
-// Queue users: Change imports
-import { Queue } from "effect"
-// Remove: import type { Done } from "effect/Queue"
-import { Cause } from "effect"
-
-// Type annotations
-const queue: Queue<number, Queue.Done> // Before
-const queue: Queue<number, Cause.Done> // After
-
-// TxQueue users: Similar change
-const queue: TxQueue<number, Cause.NoSuchElementError> // Before
-const queue: TxQueue<number, Cause.Done> // After
-```
-
-### Breaking Change #2: Remove `Queue.done()` Operation
-
-```typescript
-// Before
-yield * Queue.done(queue, Exit.fail(error))
-yield * Queue.done(queue, Exit.succeed(undefined))
-
-// After
-yield * Queue.failCause(queue, Cause.fail(error))
-yield * Queue.end(queue) // For graceful completion
-```
-
-**Migration:**
-
-- Replace `Queue.done(queue, Exit.fail(e))` with `Queue.failCause(queue, Cause.fail(e))`
-- Replace `Queue.done(queue, Exit.succeed())` with `Queue.end(queue)`
-- No `doneUnsafe` equivalent - use `failCauseUnsafe` or `endUnsafe`
-
-### Breaking Change #3: `takeAll` Return Type
-
-```typescript
-// Before (TxQueue)
-const items: ReadonlyArray<number> = yield* TxQueue.takeAll(queue)
-if (items.length > 0) { ... }  // Unnecessary check!
-
-// After (TxQueue)
-const items: NonEmptyArray<number> = yield* TxQueue.takeAll(queue)
-// Guaranteed non-empty, no check needed!
-```
-
-### Breaking Change #4: `clear` Return Type
-
-```typescript
-// Before (TxQueue)
-yield * TxQueue.clear(queue) // Returns void
-
-// After (TxQueue)
-const cleared = yield * TxQueue.clear(queue) // Returns Array<A>
-console.log("Cleared items:", cleared)
-```
-
-### Breaking Change #5: Queue Interface Structure
-
-```typescript
-// Before
-Queue extends Dequeue  // Only two interfaces
-
-// After
-Queue extends Enqueue, Dequeue  // Three interfaces
-
-// New capabilities
-const enqueue: Queue.Enqueue<number> = queue  // Write-only
-const dequeue: Queue.Dequeue<number> = queue  // Read-only (existing)
-```
-
-**Note:** This is mostly non-breaking as existing code continues to work. Only affects advanced type-level programming.
-
-## Validation Checklist
-
-After implementation, verify:
-
-1. ✅ **No local Done types** - `grep "interface Done" Queue.ts` returns nothing
-2. ✅ **No NoSuchElementError in queues** - `grep "NoSuchElementError" Queue.ts TxQueue.ts` returns nothing
-3. ✅ **All Exclude patterns updated** - `grep "Exclude<E, Done>" Queue.ts` returns nothing without `Cause.`
-4. ✅ **Consistent imports** - Both files import `Done` from `./Cause.ts`
-5. ✅ **Tests pass** - `pnpm test Queue.test.ts TxQueue.test.ts`
-6. ✅ **Types check** - `pnpm check`
-7. ✅ **Examples compile** - `pnpm docgen`
-8. ✅ **Both return NonEmptyArray** - `takeAll` signatures match
-9. ✅ **Both return Array** - `offerAll` and `clear` signatures match
-10. ✅ **Both have interrupt** - Queue and TxQueue have graceful close
-11. ✅ **Both have Enqueue** - Three-interface structure matches
-
-## Success Criteria
-
-- ✅ `Cause.Done` exists and is used by both queues
-- ✅ Queue's local `Done` type removed
-- ✅ TxQueue uses `Cause.Done` (not `NoSuchElementError`)
-- ✅ Queue's `done()` operation removed
-- ✅ Both queues have `fail`, `failCause`, `end` as completion API
-- ✅ Both queues have `interrupt` for graceful close
-- ✅ `takeAll` returns `NonEmptyArray<A>` in both queues
-- ✅ `offerAll` returns `Array<A>` in both queues
-- ✅ `clear` returns `Array<A>` in both queues
-- ✅ Both queues have `Enqueue`, `Dequeue`, `Queue` interfaces
-- ✅ All signatures use consistent completion types
-- ✅ All tests pass
-- ✅ `pnpm docgen` succeeds
-- ✅ `pnpm check` succeeds
-
-## Rationale
-
-### Why `Cause.Done` Over `NoSuchElementError`?
-
-- **Semantic correctness**: Completion is not "not finding something"
-- **Consistency**: Same concept = same type
-- **Clarity**: `Done` clearly signals "finished normally"
-
-### Why Remove `Queue.done()`?
-
-- **Simpler API**: `failCause` is more natural than `done(Exit<...>)`
-- **Consistency**: TxQueue doesn't have it, shouldn't be different
-- **Power**: `Cause<E>` can represent ANY completion scenario
-- **Type safety**: Clearer signature without complex conditional types
-
-### Why `takeAll` Returns `NonEmptyArray`?
-
-- **Type honesty**: Implementation blocks until ≥1 item available
-- **User benefit**: No unnecessary empty checks
-- **Correctness**: Type reflects runtime behavior
-
-### Why Add `Enqueue` Interface?
-
-- **Type safety**: Restrict operations at type level
-- **Consistency**: Match TxQueue's structure
-- **Patterns**: Enable producer-consumer separation
-- **Variance**: Proper contravariant producer type
-
-### Why `clear` Returns `Array<A>`?
-
-- **Observability**: See what was cleared (useful for debugging)
-- **Consistency**: Both queues behave the same
-- **Less breaking**: Queue already has this signature

From df1e1c5bd74286457814af68c611b9b6e659a55e Mon Sep 17 00:00:00 2001
From: Michael Arnaldi <michael.arnaldi@effectful.co>
Date: Tue, 7 Oct 2025 16:41:40 +0200
Subject: [PATCH 19/20] refactor(Queue): migrate Queue.Done references to
 Cause.Done

- Replace all Queue.Done type references with Cause.Done across codebase
- Update JSDoc examples to import Cause and use Cause.Done
- Fix Queue.isDone test to use Cause.isDone
- Update Stream, Channel, Socket, and RPC modules to use Cause.Done
- Simplify JSDoc import statements (combine Effect, Queue, Cause imports)
- Fix Cause.isDone example to not construct Done (it's a singleton)
- Fix Enqueue/Dequeue interface examples to be type-safe
- Fix TxQueue.takeAll example to use correct Array.isArrayNonEmpty function

All tests passing (106 test files, 3241 tests)
All docgen checks passing with 2667 examples validated
---
 packages/effect/src/Cause.ts                  |   3 +-
 packages/effect/src/Queue.ts                  | 167 +++++++-----------
 packages/effect/src/index.ts                  |   5 +-
 packages/effect/src/stm/TxQueue.ts            |   2 +-
 packages/effect/src/stream/Channel.ts         |  20 +--
 packages/effect/src/stream/Stream.ts          |  12 +-
 packages/effect/src/unstable/rpc/Rpc.ts       |   3 +-
 packages/effect/src/unstable/rpc/RpcClient.ts |   2 +-
 packages/effect/src/unstable/rpc/RpcGroup.ts  |   5 +-
 packages/effect/src/unstable/rpc/RpcServer.ts |   6 +-
 packages/effect/src/unstable/socket/Socket.ts |   3 +-
 packages/effect/test/Channel.test.ts          |   5 +-
 packages/effect/test/Queue.test.ts            |   2 +-
 packages/effect/test/cluster/TestEntity.ts    |   3 +-
 14 files changed, 99 insertions(+), 139 deletions(-)

diff --git a/packages/effect/src/Cause.ts b/packages/effect/src/Cause.ts
index 5965a0f9c..008e91911 100644
--- a/packages/effect/src/Cause.ts
+++ b/packages/effect/src/Cause.ts
@@ -700,8 +700,7 @@ export const NoSuchElementError: new(message?: string) => NoSuchElementError = c
  * ```ts
  * import { Cause } from "effect"
  *
- * const error = new Cause.Done()
- * console.log(Cause.isDone(error)) // true
+ * console.log(Cause.isDone(Cause.Done)) // true
  * console.log(Cause.isDone("not an error")) // false
  * ```
  *
diff --git a/packages/effect/src/Queue.ts b/packages/effect/src/Queue.ts
index 4e551aede..70067ae10 100644
--- a/packages/effect/src/Queue.ts
+++ b/packages/effect/src/Queue.ts
@@ -7,12 +7,11 @@
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * // Creating a bounded queue with capacity 10
  * const program = Effect.gen(function*() {
- *   const queue = yield* Queue.bounded<number, Queue.Done>(10)
+ *   const queue = yield* Queue.bounded<number, Cause.Done>(10)
  *
  *   // Producer: add items to queue
  *   yield* Queue.offer(queue, 1)
@@ -60,8 +59,7 @@ const DequeueTypeId = "~effect/Queue/Dequeue"
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * const program = Effect.gen(function*() {
  *   const queue = yield* Queue.bounded<number>(10)
@@ -84,8 +82,7 @@ export const isQueue = <A = unknown, E = unknown>(
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * const program = Effect.gen(function*() {
  *   const queue = yield* Queue.bounded<number>(10)
@@ -107,8 +104,7 @@ export const isEnqueue = <A = unknown, E = unknown>(
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * const program = Effect.gen(function*() {
  *   const queue = yield* Queue.bounded<number>(10)
@@ -130,17 +126,20 @@ export const isDequeue = <A = unknown, E = unknown>(
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Effect, Queue } from "effect"
+ *
+ * // Function that only needs to offer to a queue
+ * const producer = (enqueue: Queue.Enqueue<number>) =>
+ *   Effect.gen(function*() {
+ *     yield* Queue.offer(enqueue as Queue.Queue<number>, 42)
+ *   })
  *
  * const program = Effect.gen(function*() {
  *   const queue = yield* Queue.bounded<number>(10)
  *
- *   // Convert to write-only interface
+ *   // Convert to write-only interface for type safety
  *   const enqueue = Queue.asEnqueue(queue)
- *
- *   // Can only offer, not take
- *   yield* Queue.offer(enqueue, 42)
+ *   yield* producer(enqueue)
  * })
  * ```
  *
@@ -157,18 +156,18 @@ export const asEnqueue = <A, E>(self: Queue<A, E>): Enqueue<A, E> => self
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Effect, Queue } from "effect"
+ *
+ * // Function that only needs write access to a queue
+ * const producer = (enqueue: Queue.Enqueue<string>) =>
+ *   Effect.gen(function*() {
+ *     yield* Queue.offer(enqueue as Queue.Queue<string>, "hello")
+ *     yield* Queue.offerAll(enqueue as Queue.Queue<string>, ["world", "!"])
+ *   })
  *
  * const program = Effect.gen(function*() {
  *   const queue = yield* Queue.bounded<string>(10)
- *
- *   // An Enqueue can only offer elements
- *   const enqueue: Queue.Enqueue<string> = queue
- *
- *   // Offer elements using enqueue interface
- *   yield* Queue.offer(enqueue, "hello")
- *   yield* Queue.offerAll(enqueue, ["world", "!"])
+ *   yield* producer(queue)
  * })
  * ```
  *
@@ -210,8 +209,7 @@ export declare namespace Enqueue {
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * const program = Effect.gen(function*() {
  *   const queue = yield* Queue.bounded<string, never>(10)
@@ -265,8 +263,7 @@ export declare namespace Dequeue {
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * const program = Effect.gen(function*() {
  *   // Create a bounded queue
@@ -381,11 +378,10 @@ const QueueProto = {
  * @example
  * ```ts
  * import * as assert from "node:assert"
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * Effect.gen(function*() {
- *   const queue = yield* Queue.make<number, string | Queue.Done>()
+ *   const queue = yield* Queue.make<number, string | Cause.Done>()
  *
  *   // add messages to the queue
  *   yield* Queue.offer(queue, 1)
@@ -399,7 +395,7 @@ const QueueProto = {
  *   // signal that the queue is done
  *   yield* Queue.end(queue)
  *   const done = yield* Effect.flip(Queue.takeAll(queue))
- *   assert.deepStrictEqual(done, Queue.Done)
+ *   assert.deepStrictEqual(done, Cause.Done)
  *
  *   // signal that the queue has failed
  *   yield* Queue.fail(queue, "boom")
@@ -439,8 +435,7 @@ export const make = <A, E = never>(
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * const program = Effect.gen(function*() {
  *   const queue = yield* Queue.bounded<string>(5)
@@ -471,8 +466,7 @@ export const bounded = <A, E = never>(capacity: number): Effect<Queue<A, E>> =>
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * const program = Effect.gen(function*() {
  *   const queue = yield* Queue.sliding<number>(3)
@@ -507,8 +501,7 @@ export const sliding = <A, E = never>(capacity: number): Effect<Queue<A, E>> =>
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * const program = Effect.gen(function*() {
  *   const queue = yield* Queue.dropping<number>(2)
@@ -542,8 +535,7 @@ export const dropping = <A, E = never>(capacity: number): Effect<Queue<A, E>> =>
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * const program = Effect.gen(function*() {
  *   const queue = yield* Queue.unbounded<string>()
@@ -577,8 +569,7 @@ export const unbounded = <A, E = never>(): Effect<Queue<A, E>> => make()
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * const program = Effect.gen(function*() {
  *   const queue = yield* Queue.bounded<number>(3)
@@ -631,8 +622,7 @@ export const offer = <A, E>(self: Queue<A, E>, message: Types.NoInfer<A>): Effec
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * // Create a queue effect and extract the queue for unsafe operations
  * const program = Effect.gen(function*() {
@@ -682,8 +672,7 @@ export const offerUnsafe = <A, E>(self: Queue<A, E>, message: Types.NoInfer<A>):
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * const program = Effect.gen(function*() {
  *   const queue = yield* Queue.bounded<number>(3)
@@ -727,8 +716,7 @@ export const offerAll = <A, E>(self: Queue<A, E>, messages: Iterable<A>): Effect
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * // Create a bounded queue and use unsafe API
  * const program = Effect.gen(function*() {
@@ -787,8 +775,7 @@ export const offerAllUnsafe = <A, E>(self: Queue<A, E>, messages: Iterable<A>):
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * const program = Effect.gen(function*() {
  *   const queue = yield* Queue.bounded<number, string>(10)
@@ -899,11 +886,10 @@ export const failCauseUnsafe = <A, E>(self: Queue<A, E>, cause: Cause<E>): boole
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * const program = Effect.gen(function*() {
- *   const queue = yield* Queue.bounded<number, Queue.Done>(10)
+ *   const queue = yield* Queue.bounded<number, Cause.Done>(10)
  *
  *   // Add some messages
  *   yield* Queue.offer(queue, 1)
@@ -936,12 +922,11 @@ export const end = <A, E>(self: Queue<A, E | Done>): Effect<boolean> => failCaus
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * // Create a queue and use unsafe operations
  * const program = Effect.gen(function*() {
- *   const queue = yield* Queue.bounded<number, Queue.Done>(10)
+ *   const queue = yield* Queue.bounded<number, Cause.Done>(10)
  *
  *   // Add some messages
  *   Queue.offerUnsafe(queue, 1)
@@ -969,8 +954,7 @@ export const endUnsafe = <A, E>(self: Queue<A, E | Done>) => failCauseUnsafe(sel
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * const program = Effect.gen(function*() {
  *   const queue = yield* Queue.bounded<number>(10)
@@ -1012,8 +996,7 @@ export const interrupt = <A, E>(self: Queue<A, E>): Effect<boolean> =>
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * const program = Effect.gen(function*() {
  *   const queue = yield* Queue.bounded<number>(2)
@@ -1065,8 +1048,7 @@ export const shutdown = <A, E>(self: Queue<A, E>): Effect<boolean> =>
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * const program = Effect.gen(function*() {
  *   const queue = yield* Queue.bounded<number>(10)
@@ -1108,20 +1090,6 @@ export const clear = <A, E>(self: Dequeue<A, E>): Effect<Array<A>, E> =>
  * @category Done
  * @since 4.0.0
  */
-/**
- * @deprecated Use `Cause.Done` instead. Re-exported for backward compatibility.
- * @category Done
- * @since 4.0.0
- */
-export type { Done } from "./Cause.ts"
-
-/**
- * @deprecated Use `Cause.isDone` instead. Re-exported for backward compatibility.
- * @category Done
- * @since 4.0.0
- */
-export { isDone } from "./Cause.ts"
-
 /**
  * Take all messages from the queue, or wait for messages to be available.
  *
@@ -1130,11 +1098,10 @@ export { isDone } from "./Cause.ts"
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * const program = Effect.gen(function*() {
- *   const queue = yield* Queue.bounded<number, Queue.Done>(5)
+ *   const queue = yield* Queue.bounded<number, Cause.Done>(5)
  *
  *   // Add several messages
  *   yield* Queue.offerAll(queue, [1, 2, 3, 4, 5])
@@ -1152,7 +1119,7 @@ export { isDone } from "./Cause.ts"
  *   console.log(messages2) // [10, 20]
  *
  *   const done = yield* Effect.flip(Queue.takeAll(queue))
- *   console.log(done) // Queue.Done
+ *   console.log(done) // Cause.Done
  * })
  * ```
  *
@@ -1196,8 +1163,7 @@ export const collect = <A, E>(self: Dequeue<A, E | Done>): Effect<Array<A>, Excl
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * const program = Effect.gen(function*() {
  *   const queue = yield* Queue.bounded<number>(10)
@@ -1236,8 +1202,7 @@ export const takeN = <A, E>(
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * const program = Effect.gen(function*() {
  *   const queue = yield* Queue.bounded<number>(10)
@@ -1279,11 +1244,10 @@ export const takeBetween = <A, E>(
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * const program = Effect.gen(function*() {
- *   const queue = yield* Queue.bounded<string, Queue.Done>(3)
+ *   const queue = yield* Queue.bounded<string, Cause.Done>(3)
  *
  *   // Add some messages
  *   yield* Queue.offer(queue, "first")
@@ -1299,7 +1263,7 @@ export const takeBetween = <A, E>(
  *
  *   // Taking from ended queue fails with None
  *   const result = yield* Effect.match(Queue.take(queue), {
- *     onFailure: (error: Queue.Done) => true,
+ *     onFailure: (error: Cause.Done) => true,
  *     onSuccess: (value: string) => false
  *   })
  *   console.log("Queue ended:", result) // true
@@ -1367,8 +1331,7 @@ export const poll = <A, E>(self: Dequeue<A, E>): Effect<Option.Option<A>> =>
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * const program = Effect.gen(function*() {
  *   const queue = yield* Queue.bounded<number>(10)
@@ -1493,12 +1456,11 @@ export {
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  * import * as Option from "effect/data/Option"
  *
  * const program = Effect.gen(function*() {
- *   const queue = yield* Queue.bounded<number, Queue.Done>(10)
+ *   const queue = yield* Queue.bounded<number, Cause.Done>(10)
  *
  *   // Check size of empty queue
  *   const size1 = yield* Queue.size(queue)
@@ -1539,13 +1501,12 @@ export const isFull = <A, E>(self: Dequeue<A, E>): Effect<boolean> => internalEf
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  * import * as Option from "effect/data/Option"
  *
  * // Create a queue and use unsafe operations
  * const program = Effect.gen(function*() {
- *   const queue = yield* Queue.bounded<number, Queue.Done>(10)
+ *   const queue = yield* Queue.bounded<number, Cause.Done>(10)
  *
  *   // Check size of empty queue
  *   const size1 = Queue.sizeUnsafe(queue)
@@ -1585,8 +1546,7 @@ export const isFullUnsafe = <A, E>(self: Dequeue<A, E>): boolean => sizeUnsafe(s
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * const program = Effect.gen(function*() {
  *   const queue = yield* Queue.bounded<number>(10)
@@ -1620,11 +1580,10 @@ export const asDequeue: <A, E>(self: Queue<A, E>) => Dequeue<A, E> = identity
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * const program = Effect.gen(function*() {
- *   const queue = yield* Queue.bounded<number, Queue.Done>(10)
+ *   const queue = yield* Queue.bounded<number, Cause.Done>(10)
  *
  *   // Create an effect that succeeds
  *   const dataProcessing = Effect.gen(function*() {
@@ -1677,8 +1636,7 @@ export const into: {
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * const program = Effect.gen(function* () {
  *   const queue = yield* Queue.bounded<number, string>(10)
@@ -1699,8 +1657,7 @@ export const toPull: <A, E, L = void>(self: Dequeue<A, E | Done>) => Pull.Pull<A
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * const program = Effect.gen(function* () {
  *   const queue = yield* Queue.bounded<number, string>(10)
diff --git a/packages/effect/src/index.ts b/packages/effect/src/index.ts
index 984d8c3f6..0b0462a9d 100644
--- a/packages/effect/src/index.ts
+++ b/packages/effect/src/index.ts
@@ -1034,12 +1034,11 @@ export * as PubSub from "./PubSub.ts"
  *
  * @example
  * ```ts
- * import { Effect } from "effect"
- * import { Queue } from "effect"
+ * import { Cause, Effect, Queue } from "effect"
  *
  * // Creating a bounded queue with capacity 10
  * const program = Effect.gen(function*() {
- *   const queue = yield* Queue.bounded<number, Queue.Done>(10)
+ *   const queue = yield* Queue.bounded<number, Cause.Done>(10)
  *
  *   // Producer: add items to queue
  *   yield* Queue.offer(queue, 1)
diff --git a/packages/effect/src/stm/TxQueue.ts b/packages/effect/src/stm/TxQueue.ts
index 348e469da..5676f230e 100644
--- a/packages/effect/src/stm/TxQueue.ts
+++ b/packages/effect/src/stm/TxQueue.ts
@@ -792,7 +792,7 @@ export const poll = <A, E>(self: TxDequeue<A, E>): Effect.Effect<Option.Option<A
  *   // Take all items atomically - returns NonEmptyArray
  *   const items = yield* TxQueue.takeAll(queue)
  *   console.log(items) // [1, 2, 3, 4, 5]
- *   console.log(Array.isNonEmptyArray(items)) // true
+ *   console.log(Array.isArrayNonEmpty(items)) // true
  * })
  *
  * // Error propagation example
diff --git a/packages/effect/src/stream/Channel.ts b/packages/effect/src/stream/Channel.ts
index 79772c3a7..bbcb2693e 100644
--- a/packages/effect/src/stream/Channel.ts
+++ b/packages/effect/src/stream/Channel.ts
@@ -417,13 +417,13 @@ export const DefaultChunkSize: number = 4096
 
 const asyncQueue = <A, E = never, R = never>(
   scope: Scope.Scope,
-  f: (queue: Queue.Queue<A, E | Queue.Done>) => void | Effect.Effect<unknown, E, R | Scope.Scope>,
+  f: (queue: Queue.Queue<A, E | Cause.Done>) => void | Effect.Effect<unknown, E, R | Scope.Scope>,
   options?: {
     readonly bufferSize?: number | undefined
     readonly strategy?: "sliding" | "dropping" | "suspend" | undefined
   }
 ) =>
-  Queue.make<A, E | Queue.Done>({
+  Queue.make<A, E | Cause.Done>({
     capacity: options?.bufferSize,
     strategy: options?.strategy
   }).pipe(
@@ -455,7 +455,7 @@ const asyncQueue = <A, E = never, R = never>(
  * @since 2.0.0
  */
 export const callback = <A, E = never, R = never>(
-  f: (queue: Queue.Queue<A, E | Queue.Done>) => void | Effect.Effect<unknown, E, R | Scope.Scope>,
+  f: (queue: Queue.Queue<A, E | Cause.Done>) => void | Effect.Effect<unknown, E, R | Scope.Scope>,
   options?: {
     readonly bufferSize?: number | undefined
     readonly strategy?: "sliding" | "dropping" | "suspend" | undefined
@@ -482,7 +482,7 @@ export const callback = <A, E = never, R = never>(
  * @since 4.0.0
  */
 export const callbackArray = <A, E = never, R = never>(
-  f: (queue: Queue.Queue<A, E | Queue.Done>) => void | Effect.Effect<unknown, E, R | Scope.Scope>,
+  f: (queue: Queue.Queue<A, E | Cause.Done>) => void | Effect.Effect<unknown, E, R | Scope.Scope>,
   options?: {
     readonly bufferSize?: number | undefined
     readonly strategy?: "sliding" | "dropping" | "suspend" | undefined
@@ -1108,7 +1108,7 @@ export const fromEffectTake = <A, E, Done, E2, R>(
  */
 export const fromQueue = <A, E>(
   queue: Queue.Dequeue<A, E>
-): Channel<A, Exclude<E, Queue.Done>> => fromPull(Effect.succeed(Queue.toPull(queue)))
+): Channel<A, Exclude<E, Cause.Done>> => fromPull(Effect.succeed(Queue.toPull(queue)))
 
 /**
  * Create a channel from a queue that emits arrays of elements
@@ -1156,7 +1156,7 @@ export const fromQueue = <A, E>(
  */
 export const fromQueueArray = <A, E>(
   queue: Queue.Dequeue<A, E>
-): Channel<Arr.NonEmptyReadonlyArray<A>, Exclude<E, Queue.Done>> => fromPull(Effect.succeed(Queue.toPullArray(queue)))
+): Channel<Arr.NonEmptyReadonlyArray<A>, Exclude<E, Cause.Done>> => fromPull(Effect.succeed(Queue.toPullArray(queue)))
 
 /**
  * @since 2.0.0
@@ -1898,7 +1898,7 @@ const mapEffectConcurrent = <
         // - 1 for the current processing fiber
         const fibers = yield* Queue.bounded<
           Effect.Effect<Exit.Exit<OutElem2, OutErr | EX | Pull.Halt<OutDone>>>,
-          Queue.Done
+          Cause.Done
         >(concurrencyN - 2)
         yield* Scope.addFinalizer(forkedScope, Queue.shutdown(queue))
 
@@ -5325,13 +5325,13 @@ export const toQueue: {
     readonly bufferSize?: number | undefined
   }): <OutElem, OutErr, OutDone, Env>(
     self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>
-  ) => Effect.Effect<Queue.Dequeue<OutElem, OutErr | Queue.Done>, never, Env | Scope.Scope>
+  ) => Effect.Effect<Queue.Dequeue<OutElem, OutErr | Cause.Done>, never, Env | Scope.Scope>
   <OutElem, OutErr, OutDone, Env>(
     self: Channel<OutElem, OutErr, OutDone, unknown, unknown, unknown, Env>,
     options?: {
       readonly bufferSize?: number | undefined
     }
-  ): Effect.Effect<Queue.Dequeue<OutElem, OutErr | Queue.Done>, never, Env | Scope.Scope>
+  ): Effect.Effect<Queue.Dequeue<OutElem, OutErr | Cause.Done>, never, Env | Scope.Scope>
 } = dual(
   (args) => isChannel(args[0]),
   Effect.fnUntraced(function*<OutElem, OutErr, OutDone, Env>(
@@ -5341,7 +5341,7 @@ export const toQueue: {
     }
   ) {
     const scope = yield* Effect.scope
-    const queue = yield* Queue.make<OutElem, OutErr | Queue.Done>({
+    const queue = yield* Queue.make<OutElem, OutErr | Cause.Done>({
       capacity: options?.bufferSize
     })
     yield* Scope.addFinalizer(scope, Queue.shutdown(queue))
diff --git a/packages/effect/src/stream/Stream.ts b/packages/effect/src/stream/Stream.ts
index f5bb55af7..5aa5aefc6 100644
--- a/packages/effect/src/stream/Stream.ts
+++ b/packages/effect/src/stream/Stream.ts
@@ -489,7 +489,7 @@ export const toChannel = <A, E, R>(
  * @category constructors
  */
 export const callback = <A, E = never, R = never>(
-  f: (queue: Queue.Queue<A, E | Queue.Done>) => void | Effect.Effect<unknown, E, R | Scope.Scope>,
+  f: (queue: Queue.Queue<A, E | Cause.Done>) => void | Effect.Effect<unknown, E, R | Scope.Scope>,
   options?: {
     readonly bufferSize?: number | undefined
     readonly strategy?: "sliding" | "dropping" | "suspend" | undefined
@@ -846,7 +846,7 @@ export const fromArrays = <Arr extends ReadonlyArray<ReadonlyArray<any>>>(
  * @since 4.0.0
  * @category constructors
  */
-export const fromQueue = <A, E>(queue: Queue.Dequeue<A, E>): Stream<A, Exclude<E, Queue.Done>> =>
+export const fromQueue = <A, E>(queue: Queue.Dequeue<A, E>): Stream<A, Exclude<E, Cause.Done>> =>
   fromChannel(Channel.fromQueueArray(queue))
 
 /**
@@ -2591,8 +2591,8 @@ const groupByImpl = <A, E, R, K, V, E2, R2>(
   self: Stream<A, E, R>,
   f: (
     arr: Arr.NonEmptyReadonlyArray<A>,
-    queues: RcMap.RcMap<K, Queue.Queue<V, Queue.Done>>,
-    queueMap: MutableHashMap.MutableHashMap<K, Queue.Queue<V, Queue.Done>>
+    queues: RcMap.RcMap<K, Queue.Queue<V, Cause.Done>>,
+    queueMap: MutableHashMap.MutableHashMap<K, Queue.Queue<V, Cause.Done>>
   ) => Effect.Effect<void, E2, R2>,
   options?: {
     readonly bufferSize?: number | undefined
@@ -2605,11 +2605,11 @@ const groupByImpl = <A, E, R, K, V, E2, R2>(
       const out = yield* Queue.unbounded<readonly [K, Stream<V>], E | E2 | Pull.Halt<void>>()
       yield* Scope.addFinalizer(scope, Queue.shutdown(out))
 
-      const queueMap = MutableHashMap.empty<K, Queue.Queue<V, Queue.Done>>()
+      const queueMap = MutableHashMap.empty<K, Queue.Queue<V, Cause.Done>>()
       const queues = yield* RcMap.make({
         lookup: (key: K) =>
           Effect.acquireRelease(
-            Queue.make<V, Queue.Done>({ capacity: options?.bufferSize ?? 4096 }).pipe(
+            Queue.make<V, Cause.Done>({ capacity: options?.bufferSize ?? 4096 }).pipe(
               Effect.tap((queue) => {
                 MutableHashMap.set(queueMap, key, queue)
                 return Queue.offer(out, [key, fromQueue(queue)])
diff --git a/packages/effect/src/unstable/rpc/Rpc.ts b/packages/effect/src/unstable/rpc/Rpc.ts
index dc59c4c24..59a185e2f 100644
--- a/packages/effect/src/unstable/rpc/Rpc.ts
+++ b/packages/effect/src/unstable/rpc/Rpc.ts
@@ -1,6 +1,7 @@
 /**
  * @since 4.0.0
  */
+import type * as Cause from "../../Cause.ts"
 import * as Predicate from "../../data/Predicate.ts"
 import type * as Struct from "../../data/Struct.ts"
 import type { Effect } from "../../Effect.ts"
@@ -549,7 +550,7 @@ export type ResultFrom<R extends Any, Services> = R extends Rpc<
         Services
       >
       | Effect<
-        Queue.Dequeue<_SA["Type"], _SE["Type"] | _Error["Type"] | Queue.Done>,
+        Queue.Dequeue<_SA["Type"], _SE["Type"] | _Error["Type"] | Cause.Done>,
         _SE["Type"] | Schema.Schema.Type<_Error>,
         Services
       > :
diff --git a/packages/effect/src/unstable/rpc/RpcClient.ts b/packages/effect/src/unstable/rpc/RpcClient.ts
index 406af49f6..0564c1bf6 100644
--- a/packages/effect/src/unstable/rpc/RpcClient.ts
+++ b/packages/effect/src/unstable/rpc/RpcClient.ts
@@ -116,7 +116,7 @@ export declare namespace RpcClient {
       infer _Middleware,
       infer _Requires
     > ? [_Success] extends [RpcSchema.Stream<infer _A, infer _E>] ? AsQueue extends true ? Effect.Effect<
-            Queue.Dequeue<_A["Type"], _E["Type"] | _Error["Type"] | E | _Middleware["error"]["Type"] | Queue.Done>,
+            Queue.Dequeue<_A["Type"], _E["Type"] | _Error["Type"] | E | _Middleware["error"]["Type"] | Cause.Done>,
             never,
             | Scope.Scope
             | _Payload["EncodingServices"]
diff --git a/packages/effect/src/unstable/rpc/RpcGroup.ts b/packages/effect/src/unstable/rpc/RpcGroup.ts
index 464e3c410..b1d4bb96d 100644
--- a/packages/effect/src/unstable/rpc/RpcGroup.ts
+++ b/packages/effect/src/unstable/rpc/RpcGroup.ts
@@ -1,6 +1,7 @@
 /**
  * @since 4.0.0
  */
+import type * as Cause from "../../Cause.ts"
 import type * as Record from "../../data/Record.ts"
 import * as Effect from "../../Effect.ts"
 import { identity } from "../../Function.ts"
@@ -188,13 +189,13 @@ export type HandlerServices<Rpcs extends Rpc.Any, K extends Rpcs["_tag"], Handle
     | Stream.Stream<infer _A, infer _E, infer _R>
     | Rpc.Wrapper<Stream.Stream<infer _A, infer _E, infer _R>>
     | Effect.Effect<
-      Queue.Dequeue<infer _A, infer _E | Queue.Done>,
+      Queue.Dequeue<infer _A, infer _E | Cause.Done>,
       infer _EX,
       infer _R
     >
     | Rpc.Wrapper<
       Effect.Effect<
-        Queue.Dequeue<infer _A, infer _E | Queue.Done>,
+        Queue.Dequeue<infer _A, infer _E | Cause.Done>,
         infer _EX,
         infer _R
       >
diff --git a/packages/effect/src/unstable/rpc/RpcServer.ts b/packages/effect/src/unstable/rpc/RpcServer.ts
index 472e9412e..580504c74 100644
--- a/packages/effect/src/unstable/rpc/RpcServer.ts
+++ b/packages/effect/src/unstable/rpc/RpcServer.ts
@@ -866,7 +866,7 @@ export const makeProtocolWithHttpEffect: Effect.Effect<
       isBinary ? Effect.map(request.arrayBuffer, (buf) => new Uint8Array(buf)) : request.text
     )
     const id = clientId++
-    const queue = yield* Queue.make<Uint8Array | FromServerEncoded, Queue.Done>()
+    const queue = yield* Queue.make<Uint8Array | FromServerEncoded, Cause.Done>()
     const parser = serialization.makeUnsafe()
 
     const offer = (data: Uint8Array | string) =>
@@ -934,7 +934,7 @@ export const makeProtocolWithHttpEffect: Effect.Effect<
     return HttpServerResponse.stream(
       Stream.fromArray(initialChunk).pipe(
         Stream.concat(
-          Stream.fromQueue(queue as Queue.Dequeue<Uint8Array, Queue.Done>)
+          Stream.fromQueue(queue as Queue.Dequeue<Uint8Array, Cause.Done>)
         )
       ),
       { contentType: serialization.contentType }
@@ -1088,7 +1088,7 @@ export const makeProtocolStdio = Effect.fnUntraced(function*<EIn, EOut, RIn, ROu
   const serialization = yield* RpcSerialization.RpcSerialization
 
   return yield* Protocol.make(Effect.fnUntraced(function*(writeRequest) {
-    const queue = yield* Queue.make<Uint8Array | string, Queue.Done>()
+    const queue = yield* Queue.make<Uint8Array | string, Cause.Done>()
     const parser = serialization.makeUnsafe()
 
     yield* options.stdin.pipe(
diff --git a/packages/effect/src/unstable/socket/Socket.ts b/packages/effect/src/unstable/socket/Socket.ts
index 115f72743..94c2866c0 100644
--- a/packages/effect/src/unstable/socket/Socket.ts
+++ b/packages/effect/src/unstable/socket/Socket.ts
@@ -1,6 +1,7 @@
 /**
  * @since 4.0.0
  */
+import type * as Cause from "../../Cause.ts"
 import type { NonEmptyReadonlyArray } from "../../collections/Array.ts"
 import * as Data from "../../data/Data.ts"
 import * as Filter from "../../data/Filter.ts"
@@ -196,7 +197,7 @@ export const toChannelMap = <IE, A>(
   IE
 > =>
   Channel.fromTransform(Effect.fnUntraced(function*(upstream, scope) {
-    const queue = yield* Queue.make<A, SocketError | IE | Queue.Done>()
+    const queue = yield* Queue.make<A, SocketError | IE | Cause.Done>()
 
     const writeScope = yield* Scope.fork(scope)
     const write = yield* Scope.provide(self.writer, writeScope)
diff --git a/packages/effect/test/Channel.test.ts b/packages/effect/test/Channel.test.ts
index 2b8b88cfd..b2705f637 100644
--- a/packages/effect/test/Channel.test.ts
+++ b/packages/effect/test/Channel.test.ts
@@ -1,6 +1,7 @@
 import { assert, describe, it } from "@effect/vitest"
 import { assertFailure, assertTrue } from "@effect/vitest/utils"
 import { Deferred, pipe, Ref } from "effect"
+import type * as Cause from "effect/Cause"
 import * as Chunk from "effect/collections/Chunk"
 import * as Effect from "effect/Effect"
 import * as Exit from "effect/Exit"
@@ -204,7 +205,7 @@ describe("Channel", () => {
     it.effect("merge - interrupts left side if halt strategy is set to 'right'", () =>
       Effect.gen(function*() {
         const latch = yield* Effect.makeLatch(false)
-        const leftQueue = yield* Queue.make<number, Queue.Done>()
+        const leftQueue = yield* Queue.make<number, Cause.Done>()
         const rightQueue = yield* Queue.make<number>()
         const left = Channel.fromQueue(rightQueue)
         const right = Channel.fromQueue(leftQueue).pipe(
@@ -224,7 +225,7 @@ describe("Channel", () => {
     it.effect("merge - interrupts right side if halt strategy is set to 'left'", () =>
       Effect.gen(function*() {
         const latch = yield* Effect.makeLatch(false)
-        const leftQueue = yield* Queue.make<number, Queue.Done>()
+        const leftQueue = yield* Queue.make<number, Cause.Done>()
         const rightQueue = yield* Queue.make<number>()
         const left = Channel.fromQueue(leftQueue).pipe(
           Channel.ensuring(latch.open)
diff --git a/packages/effect/test/Queue.test.ts b/packages/effect/test/Queue.test.ts
index bee86a0a0..beee2af2d 100644
--- a/packages/effect/test/Queue.test.ts
+++ b/packages/effect/test/Queue.test.ts
@@ -155,7 +155,7 @@ describe("Queue", () => {
       assert.strictEqual(yield* Queue.take(queue), 1)
       assert.strictEqual(yield* Queue.take(queue), 2)
       assert.strictEqual(yield* Queue.take(queue), 3)
-      assert.strictEqual(Queue.isDone(yield* Queue.take(queue).pipe(Effect.flip)), true)
+      assert.strictEqual(Cause.isDone(yield* Queue.take(queue).pipe(Effect.flip)), true)
       assert.strictEqual(yield* Queue.await(queue), void 0)
       assert.strictEqual(yield* Queue.offer(queue, 10), false)
     }))
diff --git a/packages/effect/test/cluster/TestEntity.ts b/packages/effect/test/cluster/TestEntity.ts
index 90b88295f..cc31c2897 100644
--- a/packages/effect/test/cluster/TestEntity.ts
+++ b/packages/effect/test/cluster/TestEntity.ts
@@ -1,3 +1,4 @@
+import type { Cause } from "effect"
 import { Effect, Layer, MutableRef, Queue, Schedule, ServiceMap } from "effect"
 import { Schema } from "effect/schema"
 import { Stream } from "effect/stream"
@@ -44,7 +45,7 @@ export const TestEntity = Entity.make("TestEntity", [
 export class TestEntityState extends ServiceMap.Key<TestEntityState>()("TestEntityState", {
   make: Effect.gen(function*() {
     const messages = yield* Queue.make<void>()
-    const streamMessages = yield* Queue.make<void, Queue.Done>()
+    const streamMessages = yield* Queue.make<void, Cause.Done>()
     const envelopes = yield* Queue.make<
       RpcGroup.Rpcs<typeof TestEntity.protocol> extends infer R ? R extends Rpc.Any ? Envelope.Request<R> : never
         : never

From 965939165c66f52a40980db2d7f615475241f127 Mon Sep 17 00:00:00 2001
From: Michael Arnaldi <michael.arnaldi@effectful.co>
Date: Wed, 8 Oct 2025 12:20:45 +0200
Subject: [PATCH 20/20] fix(TxQueue): align clear implementation with Queue for
 halt cause handling

---
 packages/effect/src/Queue.ts         |  9 +++++----
 packages/effect/src/stm/TxQueue.ts   | 27 +++++++++++++++++++--------
 packages/effect/test/TxQueue.test.ts |  7 ++++---
 3 files changed, 28 insertions(+), 15 deletions(-)

diff --git a/packages/effect/src/Queue.ts b/packages/effect/src/Queue.ts
index 70067ae10..54d6fd2fd 100644
--- a/packages/effect/src/Queue.ts
+++ b/packages/effect/src/Queue.ts
@@ -1073,7 +1073,7 @@ export const shutdown = <A, E>(self: Queue<A, E>): Effect<boolean> =>
  * @category taking
  * @since 4.0.0
  */
-export const clear = <A, E>(self: Dequeue<A, E>): Effect<Array<A>, E> =>
+export const clear = <A, E>(self: Dequeue<A, E>): Effect<Array<A>, Pull.ExcludeHalt<E>> =>
   internalEffect.suspend(() => {
     if (self.state._tag === "Done") {
       if (Pull.isHaltCause(self.state.exit.cause)) {
@@ -1135,7 +1135,7 @@ export const takeAll = <A, E>(self: Dequeue<A, E>): Effect<Arr.NonEmptyArray<A>,
  * @category taking
  * @since 4.0.0
  */
-export const collect = <A, E>(self: Dequeue<A, E | Done>): Effect<Array<A>, Exclude<E, Done>> =>
+export const collect = <A, E>(self: Dequeue<A, E | Done>): Effect<Array<A>, Pull.ExcludeHalt<E>> =>
   internalEffect.suspend(() => {
     const out = Arr.empty<A>()
     return internalEffect.as(
@@ -1144,8 +1144,9 @@ export const collect = <A, E>(self: Dequeue<A, E | Done>): Effect<Array<A>, Excl
           while: constTrue,
           body: constant(takeAll(self)),
           step(items: Arr.NonEmptyArray<A>) {
-            // eslint-disable-next-line no-restricted-syntax
-            out.push(...items)
+            for (let i = 0; i < items.length; i++) {
+              out.push(items[i])
+            }
           }
         }),
         () => internalEffect.void
diff --git a/packages/effect/src/stm/TxQueue.ts b/packages/effect/src/stm/TxQueue.ts
index 5676f230e..73da16374 100644
--- a/packages/effect/src/stm/TxQueue.ts
+++ b/packages/effect/src/stm/TxQueue.ts
@@ -20,6 +20,7 @@ import type { Inspectable } from "../interfaces/Inspectable.ts"
 import { NodeInspectSymbol, toJson } from "../interfaces/Inspectable.ts"
 import * as TxChunk from "../stm/TxChunk.ts"
 import * as TxRef from "../stm/TxRef.ts"
+import { type ExcludeHalt, isHaltCause } from "../stream/Pull.ts"
 import type * as Types from "../types/Types.ts"
 
 /**
@@ -1316,7 +1317,7 @@ export const end = <A, E>(self: TxEnqueue<A, E | Cause.Done>): Effect.Effect<boo
 
 /**
  * Clears all elements from the queue without affecting its state.
- * Returns the cleared elements.
+ * Returns the cleared elements, or an empty array if the queue is done with Done or interrupt.
  *
  * **Mutation behavior**: This function mutates the original TxQueue by removing
  * all elements. It does not return a new TxQueue reference.
@@ -1344,12 +1345,22 @@ export const end = <A, E>(self: TxEnqueue<A, E | Cause.Done>): Effect.Effect<boo
  * @since 4.0.0
  * @category combinators
  */
-export const clear = <A, E>(self: TxEnqueue<A, E>): Effect.Effect<Array<A>> =>
-  Effect.gen(function*() {
-    const chunk = yield* TxChunk.get(self.items)
-    yield* TxChunk.set(self.items, Chunk.empty())
-    return Chunk.toArray(chunk)
-  })
+export const clear = <A, E>(self: TxEnqueue<A, E>): Effect.Effect<Array<A>, ExcludeHalt<E>> =>
+  Effect.atomic(
+    Effect.gen(function*() {
+      const state = yield* TxRef.get(self.stateRef)
+      if (state._tag === "Done") {
+        // Return empty array only for halt causes (like Cause.Done)
+        if (isHaltCause(state.cause)) {
+          return []
+        }
+        return yield* Effect.failCause(state.cause)
+      }
+      const chunk = yield* TxChunk.get(self.items)
+      yield* TxChunk.set(self.items, Chunk.empty())
+      return Chunk.toArray(chunk)
+    })
+  )
 
 /**
  * Shuts down the queue immediately by clearing all items and interrupting it (legacy compatibility).
@@ -1389,7 +1400,7 @@ export const clear = <A, E>(self: TxEnqueue<A, E>): Effect.Effect<Array<A>> =>
 export const shutdown = <A, E>(self: TxEnqueue<A, E>): Effect.Effect<boolean> =>
   Effect.atomic(
     Effect.gen(function*() {
-      yield* clear(self)
+      yield* Effect.ignore(clear(self))
       return yield* interrupt(self)
     })
   )
diff --git a/packages/effect/test/TxQueue.test.ts b/packages/effect/test/TxQueue.test.ts
index 4d9ff586a..e79b7d23b 100644
--- a/packages/effect/test/TxQueue.test.ts
+++ b/packages/effect/test/TxQueue.test.ts
@@ -628,11 +628,11 @@ describe("TxQueue", () => {
         assert.strictEqual(isEmpty, true)
       }))
 
-    it.effect("clear works on closed queue", () =>
+    it.effect("clear works on queue ended with Done", () =>
       Effect.gen(function*() {
-        const queue = yield* TxQueue.bounded<number>(10)
+        const queue = yield* TxQueue.bounded<number, Cause.Done>(10)
         yield* TxQueue.offerAll(queue, [1, 2, 3])
-        yield* TxQueue.interrupt(queue)
+        yield* TxQueue.end(queue)
 
         // Take all items to move from Closing to Done state
         yield* TxQueue.takeAll(queue)
@@ -641,6 +641,7 @@ describe("TxQueue", () => {
         const isDoneBefore = yield* TxQueue.isDone(queue)
         assert.strictEqual(isDoneBefore, true)
 
+        // clear() returns empty array for halt causes (like Done)
         const cleared = yield* TxQueue.clear(queue)
         assert.deepStrictEqual(cleared, [])