fix: delete+recreate status post, file polling fallback

- StatusBox: delete+recreate instead of PUT to keep post at thread bottom
  (Mattermost clears pin on PUT and doesn't bump edited posts)
- StatusBox: extends EventEmitter, emits 'post-replaced' events
- StatusWatcher: 500ms file polling fallback (fs.watch unreliable on
  Docker bind mounts / overlay fs)
- WatcherManager: handles post-replaced events to update activeBoxes
- SessionMonitor: forgetSession() for idle session re-detection

src/status-box.js

@@ -14,6 +14,7 @@
 
 const https = require('https');
 const http = require('http');
+const { EventEmitter } = require('events');
 const { CircuitBreaker } = require('./circuit-breaker');
 
 const DEFAULT_THROTTLE_MS = 500;
@@ -21,7 +22,7 @@ const DEFAULT_MAX_CHARS = 15000;
 const DEFAULT_MAX_RETRIES = 3;
 const DEFAULT_MAX_SOCKETS = 4;
 
-class StatusBox {
+class StatusBox extends EventEmitter {
   /**
    * @param {object} opts
    * @param {string} opts.baseUrl - Mattermost base URL
@@ -34,6 +35,7 @@ class StatusBox {
    * @param {CircuitBreaker} [opts.circuitBreaker]
    */
   constructor(opts) {
+    super();
     this.baseUrl = opts.baseUrl;
     this.token = opts.token;
     this.logger = opts.logger || null;
@@ -74,6 +76,10 @@ class StatusBox {
     // Throttle state per postId
     // Map<postId, { pending: string|null, timer: NodeJS.Timeout|null, lastFiredAt: number }>
     this._throttleState = new Map();
+
+    // Track post metadata for delete+recreate
+    // Map<postId, { channelId, rootId }>
+    this._postInfo = new Map();
   }
 
   /**
@@ -91,13 +97,8 @@ class StatusBox {
     if (this.logger) this.logger.debug({ postId: post.id, channelId }, 'Created status post');
     this.metrics.updatesSent++;
 
-    // Pin the status post so it's always visible
+    // Track post info for delete+recreate
-    try {
+    this._postInfo.set(post.id, { channelId, rootId: rootId || null });
-      await this._apiCall('POST', `/api/v4/posts/${post.id}/pin`, null);
-      if (this.logger) this.logger.debug({ postId: post.id }, 'Status post pinned');
-    } catch (pinErr) {
-      if (this.logger) this.logger.warn({ postId: post.id, err: pinErr }, 'Failed to pin status post');
-    }
 
     return post.id;
   }
@@ -162,12 +163,40 @@ class StatusBox {
     this.metrics.queueDepth = Math.max(0, this.metrics.queueDepth - 1);
 
     try {
+      // Delete + recreate to keep status post at the bottom of the thread
+      // Mattermost clears pin on PUT, and edited posts stay at their original position
+      const postInfo = this._postInfo.get(postId);
+      if (postInfo) {
+        try {
+          await this._httpRequest('DELETE', `/api/v4/posts/${postId}`, null);
+        } catch (_delErr) {
+          // If delete fails, fall back to PUT
+        }
+        const body = { channel_id: postInfo.channelId, message: this._truncate(text) };
+        if (postInfo.rootId) body.root_id = postInfo.rootId;
+        const newPost = await this._httpRequest('POST', '/api/v4/posts', body);
+        // Update tracking
+        this._postInfo.set(newPost.id, postInfo);
+        this._postInfo.delete(postId);
+        // Update throttle state key
+        const newState = this._throttleState.get(postId);
+        if (newState) {
+          this._throttleState.delete(postId);
+          this._throttleState.set(newPost.id, { pending: null, timer: null, lastFiredAt: Date.now(), resolvers: [] });
+        }
+        // Notify caller of new post ID
+        this.emit('post-replaced', postId, newPost.id);
+        this.metrics.updatesSent++;
+        resolvers.forEach(({ resolve }) => resolve());
+      } else {
+        // Fallback: regular PUT update
         await this._apiCallWithRetry('PUT', `/api/v4/posts/${postId}`, {
           id: postId,
           message: this._truncate(text),
         });
         this.metrics.updatesSent++;
         resolvers.forEach(({ resolve }) => resolve());
+      }
     } catch (err) {
       this.metrics.updatesFailed++;
       resolvers.forEach(({ reject }) => reject(err));

src/status-watcher.js

@@ -90,6 +90,28 @@ class StatusWatcher extends EventEmitter {
     if (initialState.lastOffset) {
       this._readFile(sessionKey, state);
     }
+
+    // Start file polling as fallback (fs.watch may not work on bind mounts in Docker)
+    this._startFilePoll(sessionKey, state);
+  }
+
+  /**
+   * Start polling a transcript file for changes (fallback for fs.watch).
+   * @private
+   */
+  _startFilePoll(sessionKey, state) {
+    var self = this;
+    var pollInterval = 500; // 500ms poll
+    state._filePollTimer = setInterval(function () {
+      try {
+        var stat = fs.statSync(state.transcriptFile);
+        if (stat.size > state.lastOffset) {
+          self._readFile(sessionKey, state);
+        }
+      } catch (_e) {
+        // File might not exist yet or was deleted
+      }
+    }, pollInterval);
   }
 
   /**
@@ -101,6 +123,7 @@ class StatusWatcher extends EventEmitter {
     if (!state) return;
 
     if (state.idleTimer) clearTimeout(state.idleTimer);
+    if (state._filePollTimer) clearInterval(state._filePollTimer);
     this.fileToSession.delete(state.transcriptFile);
     this.sessions.delete(sessionKey);
 
@@ -158,12 +181,16 @@ class StatusWatcher extends EventEmitter {
       this._watcher.close();
       this._watcher = null;
     }
-    // Clear all idle timers
+    // Clear all timers
     for (const [, state] of this.sessions) {
       if (state.idleTimer) {
         clearTimeout(state.idleTimer);
         state.idleTimer = null;
       }
+      if (state._filePollTimer) {
+        clearInterval(state._filePollTimer);
+        state._filePollTimer = null;
+      }
     }
     if (this.logger) this.logger.info('StatusWatcher stopped');
   }

src/watcher-manager.js

@@ -282,6 +282,18 @@ async function startDaemon() {
     logger.debug({ sessionKey }, 'Session removed from sessions.json');
   });
 
+  // ---- Post Replaced (delete+recreate) ----
+  sharedStatusBox.on('post-replaced', (oldPostId, newPostId) => {
+    // Update activeBoxes to point to new post ID
+    for (var entry of activeBoxes.entries()) {
+      if (entry[1].postId === oldPostId) {
+        entry[1].postId = newPostId;
+        logger.debug({ sessionKey: entry[0], oldPostId, newPostId }, 'Post replaced (delete+recreate)');
+        break;
+      }
+    }
+  });
+
   // ---- Session Update (from watcher) ----
   watcher.on('session-update', (sessionKey, state) => {
     const box = activeBoxes.get(sessionKey);