Method isFileStaleOnDisk

src/mcp/tools.ts:1297–1330

* On-disk drift check for a single indexed file (issue #1474). The code * renderers slice CURRENT bytes at INDEXED line ranges; when the file * changed after its last index sync those ranges can point at a DIFFERENT * symbol's code — served under the requested name with `isError: false`.

(cg: CodeGraph, relPath: string, content?: string)

   * would needlessly push the agent back to Read.
   */
  private isFileStaleOnDisk(cg: CodeGraph, relPath: string, content?: string): boolean {
    let root: string;
    try {
      root = cg.getProjectRoot();
    } catch {
      return false;
    }
    const key = `${root}\0${relPath}`;
    const now = Date.now();
    const hit = this.driftCache.get(key);
    if (hit && now - hit.at < ToolHandler.DRIFT_TTL_MS) return hit.stale;
    let stale = false;
    try {
      const rec = cg.getFile(relPath);
      const absPath = rec ? validatePathWithinRoot(root, relPath) : null;
      if (rec && absPath && existsSync(absPath)) {
        const st = statSync(absPath);
        // Same freshness test as the sync fast path (extraction/index.ts):
        // equal size + equal floored mtime ⇒ unchanged, no read needed.
        if (st.size !== rec.size || Math.floor(st.mtimeMs) !== Math.floor(rec.modifiedAt)) {
          const data = content ?? readFileSync(absPath, 'utf-8');
          // Must stay byte-identical to extraction's `hashContent` (sha256 over
          // the utf-8 string) — the identical-rewrite test in
          // mcp-stale-slice.test.ts pins the parity. Inlined (not imported)
          // to keep the extraction module off the MCP startup path.
          stale = createHash('sha256').update(data).digest('hex') !== rec.contentHash;
        }
      }
    } catch {
      stale = false;
    }
    this.driftCache.set(key, { at: now, stale });
    return stale;
  }

  private withStalenessNotice(result: ToolResult, projectPath?: string): ToolResult {
    if (result.isError) return result;