[BUG] Context condensing fails with "Provider ended the request: Unknown Error: The provided request is not valid"

[weidaru]

Problem (one or two sentences)

Context condensing fails with "Provider ended the request: Unknown Error: The provided request is not valid"

Date/time: 2026-01-23T20:27:50.029Z
Extension version: 3.42.0
Provider: bedrock
Model: anthropic.claude-sonnet-4-5-20250929-v1:0

Provider ended the request: Unknown Error: The provided request is not valid

This only happens with 3.42.0. Old release 3.41.3 does not have this problem.

Context (who is affected and when)

Happens when context condensing triggers.

Reproduction steps

Happens when context condensing triggers.

Expected result

context condensing should succeed

Actual result

context condensing fails

Variations tried (optional)

No response

App Version

3.42.0

API Provider (optional)

Amazon Bedrock

Model Used (optional)

claude 4.5 sonnet

Roo Code Task Links (optional)

No response

Relevant logs or errors (optional)

[roomote]

I've analyzed this issue and identified the root cause.

Root Cause Analysis

The issue occurs in src/core/condense/index.ts in the summarizeConversation function. When context condensing is triggered and there are orphan tool_use blocks (tool calls that haven't received a response yet), the code creates consecutive user messages, which violates Bedrock's API requirement for strict user/assistant message alternation.

The problematic code flow (lines 191-196):

// injectSyntheticToolResults may append a user message with tool_results
const messagesWithToolResults = injectSyntheticToolResults(messagesToSummarize)

// finalRequestMessage is ALSO a user message (containing condense instructions)
const requestMessages = maybeRemoveImageBlocks([...messagesWithToolResults, finalRequestMessage], apiHandler).map(
    ({ role, content }) => ({ role, content }),
)

When injectSyntheticToolResults adds a synthetic user message (to respond to orphan tool_use blocks), and then finalRequestMessage (the condense instructions) is appended as another user message, this creates:

• user: [tool_result blocks]
• user: [condense instructions]

Bedrock rejects this with "The provided request is not valid" because it doesn't allow consecutive messages with the same role.

Proposed Implementation Plan

1. Modify the logic in summarizeConversation to merge the condense instructions into the last message if it's a synthetic tool_result user message, instead of adding a separate user message
2. Add a test case specifically for Bedrock with orphan tool_use blocks during condensation
3. Ensure the fix doesn't break other providers (Anthropic, OpenAI, etc.)

Specific changes to src/core/condense/index.ts:

// After line 193, check if synthetic tool_results were added and merge messages
const messagesWithToolResults = injectSyntheticToolResults(messagesToSummarize)

// If the last message is the synthetic user message with tool_results,
// merge the condense instructions into it instead of adding a new message
const lastMessage = messagesWithToolResults[messagesWithToolResults.length - 1]
const isSyntheticToolResultMessage = 
    lastMessage !== messagesToSummarize[messagesToSummarize.length - 1] &&
    lastMessage.role === 'user'

let finalMessages
if (isSyntheticToolResultMessage && Array.isArray(lastMessage.content)) {
    // Merge condense instructions into the synthetic tool_result message
    const mergedContent = [...lastMessage.content, { type: 'text', text: condenseInstructions }]
    finalMessages = [
        ...messagesWithToolResults.slice(0, -1),
        { ...lastMessage, content: mergedContent }
    ]
} else {
    // No synthetic message, add condense instructions as separate message
    finalMessages = [...messagesWithToolResults, finalRequestMessage]
}

const requestMessages = maybeRemoveImageBlocks(finalMessages, apiHandler).map(
    ({ role, content }) => ({ role, content }),
)

This approach:

• Fixes the consecutive user messages issue for Bedrock
• Maintains backward compatibility with other providers
• Is minimally invasive to the existing code structure

Please mention @roomote in a comment saying that you approve this plan, and I'll proceed with the implementation.