Update project files

src/features/secondBrainTrace.ts

@@ -584,7 +584,35 @@ interface FileScan {
     documentProject: string | undefined;
 }
 
+/**
+ * mtime-keyed scan cache. The previous implementation re-read (and re-classified)
+ * every brain file from disk on every chat message. We now reuse a parsed
+ * `FileScan` while the file's mtime is unchanged — re-reading only when the file
+ * actually changes. This mirrors the mtime-keyed caching style of
+ * `retrieval/brainIndex.ts` (whose `getBrainTokenIndex` caches tokens the same
+ * way) while keeping the scan output byte-identical, so scoring is unaffected.
+ */
+interface ScanCacheEntry {
+    mtimeMs: number;
+    size: number;
+    scan: FileScan;
+}
+const _scanCache = new Map<string, ScanCacheEntry>();
+
 function scanFile(file: string, brainRoot: string): FileScan {
+    let mtimeMs = 0;
+    let size = 0;
+    try {
+        const stat = fs.statSync(file);
+        mtimeMs = stat.mtimeMs;
+        size = stat.size;
+        const cached = _scanCache.get(file);
+        if (cached && cached.mtimeMs === mtimeMs && cached.size === size) {
+            return cached.scan;
+        }
+    } catch {
+        // stat failed — fall through and attempt a fresh read (which will also fail safely)
+    }
     const relative = path.relative(brainRoot, file);
     const title = path.basename(file, path.extname(file));
     let content = '';
@@ -598,7 +626,11 @@ function scanFile(file: string, brainRoot: string): FileScan {
     const lower = content.toLowerCase();
     const documentProject = inferDocumentProject(relative, lower);
     const titleWithPath = `${relative.replace(/[\\/]/g, ' ')} ${title}`;
-    return { file, relative, title, titleWithPath, content, lower, sourceType, knowledgeRole, documentProject };
+    const scan: FileScan = { file, relative, title, titleWithPath, content, lower, sourceType, knowledgeRole, documentProject };
+    if (mtimeMs > 0) {
+        _scanCache.set(file, { mtimeMs, size, scan });
+    }
+    return scan;
 }
 
 function scoreScan(scan: FileScan, terms: string[], intent: SecondBrainQueryIntent, targetProject?: string): SecondBrainTraceDocument {