Slack Socket Mode Support

[reaganmcf]

Problem Statement

For corporate internal slack applications, socket mode is a huge life saver to have. Corporate firewalls make it very very tough to get endpoints that are fully exposed to the public internet, preventing those of us who work in more security centric domains from using this SDK for our internal slack bot applications.

Proposed Solution

A new socketMode: boolean parameter added to the SlackAdapterConfig that would allow the underlying transport of the slack adapter to be socket mode instead of HTTP mode. This is thoroughly well documented in Slack’s bolt framework - so enough context for an agent to get it right might be easier than implementing from scratch.

Since the adapter interface is transport agnostic enough it seems - hopefully the code change wouldn’t be too bad.

Alternatives Considered

No response

Use Case

import { Chat } from “chat”
import { createSlackAdapter } from “@chat-adapter/slack”

const bot = new Chat({
  adapters: {
    slack: createSlackAdapter({
      socketMode: true,
      // …
    })
  },
  // …
})

Priority

Critical

Contribution

• I am willing to help implement this feature

Additional Context

No response

[seanmozeik]

Used bun to patch this into Chat SDK based on Slack Bolt. Feel free to apply the patch or open a PR

diff --git a/dist/index.d.ts b/dist/index.d.ts
index f859083f83d1ea2e9339416d3518e694f50130c1..de308409fd8d100cf736d4007b61d8d5abf2b896 100644
--- a/dist/index.d.ts
+++ b/dist/index.d.ts
@@ -76,10 +76,16 @@ interface SlackAdapterConfig {
      * If provided, bot tokens stored via setInstallation() will be encrypted at rest.
      */
     encryptionKey?: string;
+    /**
+     * App-level token (xapp-...) for Socket Mode.
+     * When provided, the adapter connects to Slack via WebSocket instead of HTTP webhooks.
+     * Falls back to SLACK_APP_TOKEN env var in zero-config mode.
+     */
+    appToken?: string;
     /** Logger instance for error reporting */
     logger: Logger;
-    /** Signing secret for webhook verification */
-    signingSecret: string;
+    /** Signing secret for webhook verification. Required in webhook mode; not used in Socket Mode. */
+    signingSecret?: string;
     /** Override bot username (optional) */
     userName?: string;
 }
@@ -144,6 +150,8 @@ declare class SlackAdapter implements Adapter<SlackThreadId, unknown> {
     readonly userName: string;
     private readonly client;
     private readonly signingSecret;
+    private readonly appToken;
+    private socketClient;
     private readonly defaultBotToken;
     private chat;
     private readonly logger;
@@ -169,6 +177,8 @@ declare class SlackAdapter implements Adapter<SlackThreadId, unknown> {
      */
     private withToken;
     initialize(chat: ChatInstance): Promise<void>;
+    /** Disconnect the Socket Mode client (no-op in webhook mode). */
+    shutdown(): Promise<void>;
     private installationKey;
     /**
      * Save a Slack workspace installation.
diff --git a/dist/index.js b/dist/index.js
index abb1c5bd1a35dbdb8820fbf3bbd182a4ab3bd277..9088981c8337079705da6e3e77cc0f402535c1a3 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -1,4 +1,5 @@
 // src/index.ts
+import { SocketModeClient } from "@slack/socket-mode";
 import { AsyncLocalStorage } from "async_hooks";
 import { createHmac, timingSafeEqual } from "crypto";
 import {
@@ -590,6 +591,8 @@ var SlackAdapter = class _SlackAdapter {
   userName;
   client;
   signingSecret;
+  appToken;
+  socketClient;
   defaultBotToken;
   chat = null;
   logger;
@@ -614,7 +617,8 @@ var SlackAdapter = class _SlackAdapter {
   }
   constructor(config) {
     this.client = new WebClient(config.botToken);
-    this.signingSecret = config.signingSecret;
+    this.signingSecret = config.signingSecret ?? "";
+    this.appToken = config.appToken;
     this.defaultBotToken = config.botToken;
     this.logger = config.logger;
     this.userName = config.userName || "bot";
@@ -668,10 +672,48 @@ var SlackAdapter = class _SlackAdapter {
         this.logger.warn("Could not fetch bot user ID", { error });
       }
     }
-    if (!this.defaultBotToken) {
+    if (this.appToken) {
+      this.socketClient = new SocketModeClient({ appToken: this.appToken });
+      this.socketClient.on("slack_event", (args) => {
+        void args.ack();
+        this.dispatchSocketEvent(args.body);
+      });
+      await this.socketClient.start();
+      this.logger.info("Slack adapter initialized in Socket Mode");
+    } else if (!this.defaultBotToken) {
       this.logger.info("Slack adapter initialized in multi-workspace mode");
     }
   }
+  async shutdown() {
+    if (this.socketClient) {
+      await this.socketClient.disconnect();
+      this.socketClient = void 0;
+    }
+  }
+  /**
+   * Dispatch a raw Socket Mode event body to the appropriate handler.
+   * The body shape matches the HTTP webhook JSON (same Slack Events API payload).
+   */
+  dispatchSocketEvent(body) {
+    if (typeof body !== "object" || body === null) return;
+    const payload = body;
+    switch (payload.type) {
+      case "event_callback":
+        this.processEventPayload(payload);
+        break;
+      case "slash_commands": {
+        const params = new URLSearchParams();
+        for (const [k, v] of Object.entries(payload)) {
+          if (typeof v === "string") params.set(k, v);
+        }
+        void this.handleSlashCommand(params);
+        break;
+      }
+      default:
+        // block_actions, view_submission, view_closed arrive as plain JSON in socket mode
+        this.dispatchInteractivePayload(payload);
+    }
+  }
   // ===========================================================================
   // Multi-workspace installation management
   // ===========================================================================
@@ -870,6 +912,9 @@ var SlackAdapter = class _SlackAdapter {
     }
   }
   async handleWebhook(request, options) {
+    if (this.appToken) {
+      return new Response("Socket Mode is active. This webhook endpoint is not used.", { status: 405 });
+    }
     const body = await request.text();
     this.logger.debug("Slack webhook raw body", { body });
     const timestamp = request.headers.get("x-slack-request-timestamp");
@@ -978,6 +1023,13 @@ var SlackAdapter = class _SlackAdapter {
     } catch {
       return new Response("Invalid payload JSON", { status: 400 });
     }
+    return this.dispatchInteractivePayload(payload, options);
+  }
+  /**
+   * Dispatch an already-parsed interactive payload. Used by both HTTP webhook
+   * and Socket Mode paths (which receive JSON directly, without URL-encoding).
+   */
+  dispatchInteractivePayload(payload, options) {
     switch (payload.type) {
       case "block_actions":
         this.handleBlockActions(payload, options);
@@ -2597,16 +2649,19 @@ var SlackAdapter = class _SlackAdapter {
   }
 };
 function createSlackAdapter(config) {
-  const signingSecret = config?.signingSecret ?? process.env.SLACK_SIGNING_SECRET;
-  if (!signingSecret) {
+  const appToken = config?.appToken ?? process.env.SLACK_APP_TOKEN;
+  const isSocketMode = !!appToken;
+  const signingSecret = config?.signingSecret ?? (isSocketMode ? void 0 : process.env.SLACK_SIGNING_SECRET);
+  if (!signingSecret && !isSocketMode) {
     throw new ValidationError(
       "slack",
-      "signingSecret is required. Set SLACK_SIGNING_SECRET or provide it in config."
+      "signingSecret is required in webhook mode. Set SLACK_SIGNING_SECRET, or provide appToken for Socket Mode."
     );
   }
   const zeroConfig = !config;
   const resolved = {
     signingSecret,
+    appToken,
     botToken: config?.botToken ?? (zeroConfig ? process.env.SLACK_BOT_TOKEN : void 0),
     clientId: config?.clientId ?? (zeroConfig ? process.env.SLACK_CLIENT_ID : void 0),
     clientSecret: config?.clientSecret ?? (zeroConfig ? process.env.SLACK_CLIENT_SECRET : void 0),

package.json

"patchedDependencies": {
      "@chat-adapter/slack@4.13.4": "patches/@chat-adapter%2Fslack@4.13.4.patch"
   }