Diff editing not working with Qwen3 235B Instruct 2507 (self-hosted by vLLM)

[SandboChang]

App Version

3.25.20

API Provider

OpenAI Compatible

Model Used

Qwen3 235B Instruct 2507

Roo Code Task Links (Optional)

No response

🔁 Steps to Reproduce

1. Setup
   The Roocode is running on a VSCode client

Version: 1.103.1 (Universal)
Commit: 360a4e4fd251bfce169a4ddf857c7d25d1ad40da
Date: 2025-08-12T16:25:40.542Z
Electron: 37.2.3
ElectronBuildId: 12035395
Chromium: 138.0.7204.100
Node.js: 22.17.0
V8: 13.8.500258-electron.0
OS: Darwin arm64 24.6.0

And the hosting vLLM is on a ubuntu 24.04, version 0.10.1.
The exact LLM is
QuantTrio/Qwen3-235B-A22B-Instruct-2507-AWQ

2. Action
   With an existing piece of code, ask Roocode to perform a modification so it will try to do editing of the code.

3. Upon generating the new code, when Roocode tries to edit by diff, it will fail and said Edit Unsuccessful. Often with this message:

I need to escape the "=======" line in the SEARCH section. Let me try again with the proper escaping:

Then eventually it may try to do a complete rewrite, and this can work to replace the code.

💥 Outcome Summary

Expected:
When Roocode tried to update a small portion of the code, it can use the diff editing tool to change the target section efficiently.

But:
Roocode cannot do the diff edit most of the time (at least for the last couple of tests), and ended up having to rewrite the whole code.

For reference, using Kilocode I don't have the same problem (version:4.82.1)

📄 Relevant Logs or Errors (Optional)

[daniel-lxs]

Hey @SandboChang Are you trying to edit the same file with Roo Code and Kilo? I'm trying to figure out if we need to adjust our tool in some way

[SandboChang]

Hey @SandboChang Are you trying to edit the same file with Roo Code and Kilo? I'm trying to figure out if we need to adjust our tool in some way

Yes, I was trying with the same files and to and fro a couple times to see if it was an individual cases.

It was quite reproducible: RooCode at the moment might occasionally be able to edit the file, but more often than not it can’t. One time it also ran into a loop of reading the code. (Context windows was 128k and it wasn’t full). I would say something is off at the moment with at least the Qwen3 model I am trying. In the past (maybe a month or more ago, I remember I don’t have this issue with a similar if not the same Qwen3 model).

With Kilocode, it does occasionally fail to edit once but often the next time after adjusting the search parameters it will manage to do the diff edit. Never have I seen it running into a loop nor having to do a whole file update this evening with over 30 prompts.