fix: cap slack edit fallback text

CHANGELOG.md

@@ -78,6 +78,7 @@ Docs: https://docs.openclaw.ai
 - Slack/commands: drop fallback command argument buttons whose encoded values exceed Slack's button-value limit, so one oversized plugin choice no longer makes Slack reject the whole menu. Thanks @slackapi.
 - Slack/messages: merge message-tool presentation and interactive blocks on Slack sends, so buttons and selects are no longer dropped when a structured message body is also present. Thanks @slackapi.
 - Slack/messages: cap Block Kit fallback text to Slack's send limit while preserving the rendered blocks, so long context fallbacks no longer make rich Slack messages fail with `msg_too_long`. Thanks @slackapi.
+- Slack/messages: cap Block Kit fallback text on message edits while preserving the rendered blocks, so long context fallbacks no longer make Slack reject `chat.update` calls with `msg_too_long`. Thanks @slackapi.
 - Channels/WhatsApp: require Baileys outbound message ids before marking auto-replies delivered, so transcript text and ack reactions no longer make failed group replies look sent. Fixes #49225. Thanks @TinyTb.
 - CLI/update: scope packaged Node compile caches by OpenClaw version and install metadata, so global installs no longer reuse stale compiled chunks after package updates. Thanks @pashpashpash.
 - Channels/Voice call: keep pre-auth webhook in-flight limiting active when socket remote address metadata is missing, so slow-body requests from stripped-IP proxy paths still share the fallback bucket. (#74453) Thanks @davidangularme.

extensions/slack/src/actions.blocks.test.ts

@@ -3,6 +3,7 @@ import { createSlackEditTestClient, installSlackBlockTestMocks } from "./blocks.
 
 installSlackBlockTestMocks();
 const { editSlackMessage } = await import("./actions.js");
+const SLACK_TEXT_LIMIT = 8000;
 
 describe("editSlackMessage blocks", () => {
   it("updates with valid blocks", async () => {
@@ -80,6 +81,35 @@ describe("editSlackMessage blocks", () => {
     );
   });
 
+  it("caps long block fallback text while preserving edit blocks", async () => {
+    const client = createSlackEditTestClient();
+    const longContextText = "a".repeat(3000);
+    const blocks = [
+      {
+        type: "context",
+        elements: [
+          { type: "mrkdwn", text: longContextText },
+          { type: "mrkdwn", text: longContextText },
+          { type: "mrkdwn", text: longContextText },
+        ],
+      },
+    ];
+
+    await editSlackMessage("C123", "171234.567", "", {
+      token: "xoxb-test",
+      client,
+      blocks,
+    });
+
+    expect(client.chat.update).toHaveBeenCalledWith(
+      expect.objectContaining({
+        text: expect.stringMatching(/…$/),
+        blocks,
+      }),
+    );
+    expect(client.chat.update.mock.calls[0]?.[0].text).toHaveLength(SLACK_TEXT_LIMIT);
+  });
+
   it("rejects empty blocks arrays", async () => {
     const client = createSlackEditTestClient();
 

extensions/slack/src/actions.ts

@@ -6,10 +6,12 @@ import { resolveSlackAccount } from "./accounts.js";
 import { buildSlackBlocksFallbackText } from "./blocks-fallback.js";
 import { validateSlackBlocksArray } from "./blocks-input.js";
 import { createSlackWebClient, getSlackWriteClient } from "./client.js";
+import { SLACK_TEXT_LIMIT } from "./limits.js";
 import { resolveSlackMedia } from "./monitor/media.js";
 import type { SlackMediaResult } from "./monitor/media.js";
 import { sendMessageSlack } from "./send.js";
 import { resolveSlackBotToken } from "./token.js";
+import { truncateSlackText } from "./truncate.js";
 
 export type SlackActionClientOpts = {
   cfg?: OpenClawConfig;
@@ -234,7 +236,9 @@ export async function editSlackMessage(
   await client.chat.update({
     channel: channelId,
     ts: messageId,
-    text: trimmedContent || (blocks ? buildSlackBlocksFallbackText(blocks) : " "),
+    text:
+      trimmedContent ||
+      (blocks ? truncateSlackText(buildSlackBlocksFallbackText(blocks), SLACK_TEXT_LIMIT) : " "),
     ...(blocks ? { blocks } : {}),
   });
 }