hermes - 💡(How to fix) Fix [Bug]: write_file silently fails + agent loops when model emits unescaped triple-quotes in JSON content [1 pull requests]

Bug Description

When a model tries to write Python code containing triple-double-quote docstrings (""") via the write_file tool, the tool call silently fails. No error is shown to the user, and the agent retries with the same broken JSON causing a stuck loop.

Root Cause

The failure is in _repair_tool_call_arguments() in agent/message_sanitization.py. When the model emits unescaped """ inside the "content" JSON string value:

{"path": "foo.py", "content": "def f():\n    """Docstring."""\n    pass"}

…the JSON is malformed (inner quotes terminate the string early). The repair function correctly identifies this as unrepairable and falls back to "{}". However, it also discards the path field — so _handle_write_file({}) fires a generic "path missing" error instead of the actionable "content missing" error (which suggests execute_code as an alternative). The model receives a confusing error, retries with the same broken JSON, and loops.

Steps to Reproduce

1. Ask a model to use write_file to create a .py file containing triple-double-quoted docstrings
2. The JSON argument string will be malformed by the unescaped """
3. Agent silently fails — no file written
4. Agent retries with identical malformed JSON → stuck loop

Expected Behavior

• The repair function should extract the path field even when content is unrecoverable
• The model should receive the "content missing" error (which suggests execute_code)
• The retry loop should be broken

Proposed Fix

In _repair_tool_call_arguments(), just before the final return "{}" fallback: add a write_file-specific recovery pass that uses a narrow regex to extract the "path" value from the malformed JSON string. File paths are always simple strings (no quoting issues), so a regex like "path"\s*:\s*"([^"]+)" reliably extracts them. Return {"path": "<extracted>"}, which triggers the existing "content missing" error path that already guides the model to use execute_code.

A PR with the fix (agent/message_sanitization.py only) is ready to submit.

Related

• #19096 - write_file silently produces zero-byte files when content arg is missing (symptom-level)
• #22696 - tool_use XML parser fails when closing tag appears inside JSON string (cousin problem, different code path)

Environment

• Hermes Agent v0.14.0 (2026.5.16)
• Any model that emits Python code with docstrings via write_file