fix: seal mattermost preview finalization

CHANGELOG.md

@@ -11,6 +11,7 @@ Docs: https://docs.openclaw.ai
 - Plugins/tasks: add a detached runtime registration contract so plugin executors can own detached task lifecycle and cancellation without reaching into core task internals. (#68915) Thanks @mbelinky.
 - Terminal/logging: optimize `sanitizeForLog()` by replacing the iterative control-character stripping loop with a single regex pass while preserving the existing ANSI-first sanitization behavior. (#67205) Thanks @bulutmuf.
 - QA/CI: make `openclaw qa suite` and `openclaw qa telegram` fail by default when scenarios fail, add `--allow-failures` for artifact-only runs, and tighten live-lane defaults for CI automation. (#69122) Thanks @joshavant.
+- Mattermost: stream thinking, tool activity, and partial reply text into a single draft preview post that finalizes in place when safe. (#47838) thanks @ninjaa.
 
 ### Fixes
 
@@ -256,7 +257,6 @@ Docs: https://docs.openclaw.ai
 
 - OpenAI Codex/models: add forward-compat support for `gpt-5.4-pro`, including Codex pricing/limits and list/status visibility before the upstream catalog catches up. (#66453) Thanks @jepson-liu.
 - Telegram/forum topics: surface human topic names in agent context, prompt metadata, and plugin hook metadata by learning names from Telegram forum service messages. (#65973) Thanks @ptahdunbar.
-- Mattermost: stream thinking, tool activity, and partial reply text into a single draft preview post that finalizes in place when safe. (#47838) thanks @ninjaa.
 
 ### Fixes
 

extensions/mattermost/src/mattermost/monitor.test.ts

@@ -66,6 +66,7 @@ function createDraftStreamMock(postId: string | undefined = "preview-post-1") {
     flush: vi.fn(async () => {}),
     postId: vi.fn(() => postId),
     clear: vi.fn(async () => {}),
+    stop: vi.fn(async () => {}),
   };
 }
 
@@ -315,6 +316,10 @@ describe("deliverMattermostReplyWithDraftPreview", () => {
       "preview-post-1",
       expect.objectContaining({ message: "Final answer" }),
     );
+    expect(draftStream.stop).toHaveBeenCalledTimes(1);
+    expect(draftStream.stop.mock.invocationCallOrder[0]).toBeLessThan(
+      updateMattermostPostSpy.mock.invocationCallOrder[0] ?? Number.POSITIVE_INFINITY,
+    );
     expect(deliverFinal).not.toHaveBeenCalled();
     expect(draftStream.clear).not.toHaveBeenCalled();
   });

extensions/mattermost/src/mattermost/monitor.ts

@@ -274,7 +274,10 @@ type MattermostDraftPreviewDeliverParams = {
   payload: ReplyPayload;
   info: { kind: "tool" | "block" | "final" };
   client: MattermostClient;
-  draftStream: Pick<ReturnType<typeof createMattermostDraftStream>, "flush" | "postId" | "clear">;
+  draftStream: Pick<
+    ReturnType<typeof createMattermostDraftStream>,
+    "flush" | "postId" | "clear" | "stop"
+  >;
   effectiveReplyToId?: string;
   resolvePreviewFinalText: (text?: string) => string | undefined;
   previewState: MattermostDraftPreviewState;
@@ -310,6 +313,9 @@ export async function deliverMattermostReplyWithDraftPreview(
       })
     ) {
       try {
+        // Seal the preview before the final edit so late draft events cannot
+        // patch over the finalized visible message.
+        await params.draftStream.stop();
         await updateMattermostPost(params.client, previewPostId, {
           message: previewFinalText,
         });