GPT-5.1-Codex-Max Agent Mode failing to edit files #286819
Description
Type: Bug
Description:
I am writing to report a functional issue with the GPT-5.1-Codex-Max model within GitHub Copilot. While other available models are correctly performing file edits and applying changes directly to the workspace, this specific model is failing to operate in Agent Mode.
Steps to Reproduce:
Select the GPT-5.1-Codex-Max model in the Copilot Chat interface.
Provide a prompt that requires file modification (e.g., "Refactor this function" or "Add a new property to this component").
Observe that the model provides only a text-based explanation or code blocks in the chat, but does not trigger the "Edit" or "Apply" functionality to modify the files in the editor.
Expected Behavior:
The model should act as an agent, automatically proposing edits or directly modifying the code files, similar to the behavior seen in other Copilot models (like GPT-4o or Claude 3.5 Sonnet).
Actual Behavior:
The model acts as a standard chatbot, providing code snippets without the ability to interact with the file system or apply changes to the workspace.
I would appreciate it if you could investigate if this is a known limitation of this specific model or a bug in the current integration.
Best regards,
Claudio Vasconcelos
VS Code version: Code 1.108.0 (94e8ae2, 2026-01-08T13:53:10.781Z)
OS version: Windows_NT x64 10.0.26200
Modes:
System Info
| Item | Value |
|---|---|
| CPUs | 11th Gen Intel(R) Core(TM) i5-1135G7 @ 2.40GHz (8 x 1382) |
| GPU Status | 2d_canvas: enabled direct_rendering_display_compositor: disabled_off_ok gpu_compositing: enabled multiple_raster_threads: enabled_on opengl: enabled_on rasterization: enabled raw_draw: disabled_off_ok skia_graphite: disabled_off trees_in_viz: disabled_off video_decode: enabled video_encode: enabled webgl: enabled webgl2: enabled webgpu: enabled webnn: disabled_off |
| Load (avg) | undefined |
| Memory (System) | 63.74GB (42.81GB free) |
| Process Argv | --crash-reporter-id a1cae51a-9d40-434d-935e-4f5ccb77c510 |
| Screen Reader | no |
| VM | 0% |
Extensions (16)
| Extension | Author (truncated) | Version |
|---|---|---|
| aws-toolkit-vscode | ama | 3.92.0 |
| copilot-chat | Git | 0.36.0 |
| vscode-github-actions | git | 0.29.1 |
| terraform | has | 2.37.6 |
| rainbow-csv | mec | 3.23.0 |
| git-graph | mhu | 1.30.0 |
| vscode-containers | ms- | 2.3.0 |
| vscode-dotnet-runtime | ms- | 3.0.0 |
| vscode-kubernetes-tools | ms- | 1.3.29 |
| debugpy | ms- | 2025.18.0 |
| python | ms- | 2026.0.0 |
| vscode-pylance | ms- | 2025.10.4 |
| vscode-python-envs | ms- | 1.16.0 |
| remote-containers | ms- | 0.437.0 |
| chatgpt | ope | 0.5.58 |
| vscode-yaml | red | 1.19.1 |
A/B Experiments
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