What happened?

Summary:
During file editing (especially for .md or large source files), the agent frequently calls write_file to
overwrite the entire file with incorrect or truncated content, skipping the necessary read_file step.

Actual Behavior:
Instead of performing surgical edits, the agent "hallucinates" the current content of a file and writes a new
version over it. This often results in the loss of existing code, documentation, or formatting that wasn't part
of the specific change request.

What did you expect to happen?

Expected Behavior:
The agent should follow a strict "Read-Plan-Act" cycle:

1. Read: Must read the target file (or relevant sections) to understand the current state.
2. Plan: Propose the change based on actual content.
3. Act: Use granular replacement tools (like a string-replace tool) instead of full-file write_file whenever
   possible.

Suggested Improvement:

1. Introduce a more granular replace tool (similar to Gemini CLI's implementation) that requires matching an
   old_string to ensure the agent has actually read and understood the target area.
2. Add a guardrail in the system prompt: "Never overwrite a file without reading its current content first."

Client information

$ qwen /about
# paste output here

Login information

No response

Anything else we need to know?

No response