silently corrupts any write-then-read workflow in the same session. Agent sees stale state and enters error-recovery loops. In the attached session transcript the agent burned 12 API calls and ~$0.03 fighting this cache, eventually working around it with terminal("cat hello.txt"). read_file(P) returns {"content": "File unchanged since last read...", "path": "P", "dedup": true} in 0.00s, serving the pre-write result (including a stale "File not found" error). write_file does not invalidate the read_file cache entry for the same path.

Additional Logs / Traceback (optional)

20:25:25 - run_agent - WARNING [20260420_202441_6227d1] - Tool read_file returned error (0.43s): {"content": "", "total_lines": 0, "file_size": 0, "truncated": false, "is_binary": false, "is_image": false, "error": "File not found: hello.txt"} 20:25:25 - root - DEBUG [20260420_202441_6227d1] - Tool result (146 chars): {"content": "", "total_lines": 0, "file_size": 0, "truncated": false, "is_binary": false, "is_image": false, "error": "File not found: hello.txt"} The dedup layer caches read_file results by (path, session) without listening for write_file / patch / terminal mutations on the same path, and without stat-checking mtime/size on serve. A second smaller issue: the cache treats error results (File not found) as cacheable, which is independently questionable — errors should generally bypass or short-TTL the cache. Don't cache error results at all, or cache them with a short TTL (e.g. 2 seconds) so transient File not found doesn't poison the session.

TL;DR

Invalidate the read_file dedup entry for a path whenever write_file, patch, or any mutating filesystem tool runs in the session to fix the cache corruption issue.

Guidance

• Identify the cache invalidation logic in the read_file and write_file functions to ensure that the cache is updated after a file is written.
• Consider implementing a cache key based on (path, mtime, size) to make the cache self-healing.
• Review the error handling in the cache to prevent caching error results or use a short TTL (e.g., 2 seconds) to avoid poisoning the session.
• Search for the string "File unchanged since last read" to locate the relevant code and apply the necessary fixes.

Example

No code snippet is provided as the issue does not contain sufficient information about the implementation details.

Notes

The proposed fix suggests multiple approaches to address the issue, including cache invalidation, self-healing cache, and error handling. The choice of approach depends on the specific requirements and constraints of the system.

Recommendation

Apply the workaround by invalidating the read_file dedup entry for a path whenever write_file, patch, or any mutating filesystem tool runs in the session, as this approach directly addresses the root cause of the issue.