Copilot diff incorrect - shows old changes of mine as its own changes

Type: Bug

I don't know how exactly to reproduce this, as it's only popped up intermittently. But it's occurred a few times over a span of months.

This time, I gave Copilot (Claude Sonnet 5, local mode, no sandbox) a task, and once it finished, it showed me a diff of the changes it had made, like usual (the green/red highlighted diff with the "Keep/Undo" option for each change). But the diff included changes I (not Claude) had made in commits up to 2 months old.

This occurred was in chat about 3 months old which I had come back to for this new request. This fits with Claude's own hypothesis, which is that the baseline for the diff is an old snapshot from the last time I used this conversation, instead of the actual current state of the code. Unfortunately I don't recall the relevant timing for the other instances where I encountered this bug.

VS Code version: Code 1.136.1 (a44adf7f53e00964ab890f9f8758a334f1fc15bc, 2026-09-03T05:06:41Z)
OS version: Linux x64 7.0.0-30-generic snap
Modes:
Remote OS version: Linux x64 4.18.0-553.151.1.el8_10.x86_64

System Info

|Item|Value|
|---|---|
|CPUs|11th Gen Intel(R) Core(TM) i7-1185G7 @ 3.00GHz (8 x 912)|
|GPU Status|2d_canvas: disabled_software
GPU0: VENDOR= 0x0000, DEVICE=0x0000
Machine model name:
Machine model version:
direct_rendering_display_compositor: disabled_off_ok
gpu_compositing: disabled_software
multiple_raster_threads: disabled_off
opengl: disabled_off
rasterization: disabled_software
raw_draw: disabled_off_ok
skia_graphite: disabled_off
trees_in_viz: disabled_off
video_decode: disabled_software
video_encode: disabled_software
vulkan: disabled_off
webgl: disabled_off
webgpu: disabled_off
webgpu_on_vk_via_gl_interop: disabled_off
webnn: disabled_off|
|Load (avg)|1, 1, 1|
|Memory (System)|31.06GB (9.71GB free)|
|Process Argv|--no-sandbox --force-user-env --ozone-platform=x11|
|Screen Reader|no|
|VM|0%|
|DESKTOP_SESSION|ubuntu|
|XDG_CURRENT_DESKTOP|ubuntu:GNOME|
|XDG_SESSION_DESKTOP|ubuntu|
|XDG_SESSION_TYPE|wayland|

|Item|Value|
|---|---|
|Remote|SSH: dev|
|OS|Linux x64 4.18.0-553.151.1.el8_10.x86_64|
|CPUs|AMD EPYC 7313 16-Core Processor (64 x 3715)|
|Memory (System)|251.00GB (154.00GB free)|
|VM|0%|
Extensions (23)

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