Old pasted image permanently breaks later text-only requests with vision_attachment_not_accessible

[abhineetst18]

Type: Bug

Description

An old pasted image in a Copilot Chat conversation has become inaccessible. Copilot continues including that historical attachment in every subsequent request, including text-only prompts.

As a result, every new prompt in the conversation fails with vision_attachment_not_accessible. VS Code repeatedly displays "Recovering from request error", retries the same invalid request, and eventually fails.

The conversation can no longer be continued, even though all its text history remains valid.

Environment

• OS: macOS
• VS Code: 1.136.0
• GitHub Copilot Chat: 0.64.0
• Model: GPT-5.6 Sol
• Attachment type: Pasted PNG
• Attachment resource ID: 4b4fc06993759fa5b7cc0c41e4685156dc287d3f807a8189ec23a1bbf95e3023
• Failed request ID: 64f8f76b-d067-4fbf-9be8-188dd766659e

The conversation originated under an older Copilot extension version and was later reopened with version 0.64.0.

Timeline

• The PNG was pasted into the conversation on July 28, 2026.
• The conversation continued working after that.
• Starting August 27, 2026, every new request in this conversation began failing.
• The same failure occurred again on August 31 and September 2.

Steps to reproduce

The exact attachment-expiry condition may be time-dependent:

1. Create a Copilot Chat conversation.
2. Paste an image into one of the requests.
3. Continue using the conversation over an extended period.
4. Wait until the stored image resource becomes unavailable or expires.
5. Reopen the conversation and send a new text-only prompt with no attachment.
6. Observe that Copilot still sends the historical image attachment.
7. The request fails and is retried several times.

Actual behavior

The extension logs show:

WebSocket CAPI error: one or more attachments was not accessible
(vision_attachment_not_accessible)

Retrying chat request with default fetcher after:
Request Failed: vision_attachment_not_accessible
one or more attachments was not accessible

Server error: 400
{"error":{"message":"one or more attachments was not accessible",
"code":"vision_attachment_not_accessible"}}

[ToolCallingLoop] Auto-retrying on error (attempt 1/3): failed

VS Code version: Code 1.136.0 (520fb30b2d3d324b4cb2342f6e88e2cd93751de1, 2026-09-02T09:13:42Z)
OS version: Darwin arm64 25.5.0
Modes:

<details>
<summary>System Info</summary>

|Item|Value|
|---|---|
|CPUs|Apple M1 Pro (8 x 2400)|
|GPU Status|2d_canvas: enabled<br>GPU0: VENDOR= 0x106b [Google Inc. (Apple)], DEVICE=0x0000 [ANGLE (Apple, ANGLE Metal Renderer: Apple M1 Pro, Version 26.5.2 (Build 25F84))], DRIVER_VENDOR=Apple, DRIVER_VERSION=26.5.2 *ACTIVE*<br>Machine model name: MacBookPro<br>Machine model version: 18.3<br>direct_rendering_display_compositor: disabled_off_ok<br>gpu_compositing: enabled<br>multiple_raster_threads: enabled_on<br>opengl: enabled_on<br>rasterization: enabled<br>raw_draw: disabled_off_ok<br>skia_graphite: enabled_on<br>trees_in_viz: disabled_off<br>video_decode: enabled<br>video_encode: enabled<br>webgl: enabled<br>webgpu: enabled<br>webnn: disabled_off|
|Load (avg)|3, 5, 5|
|Memory (System)|16.00GB (0.31GB free)|
|Process Argv|--crash-reporter-id 512c0536-e84c-4ae9-a955-176a1c05c79f|
|Screen Reader|no|
|VM|0%|
</details><details><summary>Extensions (14)</summary>

Name|Identifier|Author|Version
---|---|---|---
GitHub Actions|github.vscode-github-actions|github|0.32.3
GitHub Pull Requests|github.vscode-pull-request-github|GitHub|0.164.0
Draw.io Integration|hediet.vscode-drawio|hediet|1.9.0
LLDB DAP|llvm-vs-code-extensions.lldb-dap|llvm-vs-code-extensions|0.4.1
Rainbow CSV|mechatroner.rainbow-csv|mechatroner|3.24.1
Python Debugger|ms-python.debugpy|ms-python|2026.6.0
Python|ms-python.python|ms-python|2026.4.0
Pylance|ms-python.vscode-pylance|ms-python|2026.3.1
WSL|ms-vscode-remote.remote-wsl|ms-vscode-remote|0.104.3
Notepad++ keymap|ms-vscode.notepadplusplus-keybindings|ms-vscode|1.0.7
Chat Customizations Evaluations|ms-vscode.vscode-chat-customizations-evaluations|ms-vscode|1.0.8
VS Code Speech|ms-vscode.vscode-speech|ms-vscode|0.16.0
Svelte for VS Code|svelte.svelte-vscode|svelte|110.3.1
Swift|swiftlang.swift-vscode|swiftlang|2.16.7

</details><details>
<summary>A/B Experiments</summary>

vsliv368cf:30146710
binariesv615:30325510
nativeloc1:31344060
dwcopilot:31170013
dwoutputs:31242946
copilot_t_ci:31333650
e5gg6876:31282496
pythonrdcb7:31342333
6518g693:31463988
aj953862:31281341
82j33506:31327384
envsactivate1:31551504
cloudbuttont:31379625
3efgi100_wstrepl:31403338
56b7f661:31457055
ec5jj548:31422691
diffpatch-lysithea-24-production:31577085
cp_cls_t_966_ss:31526232
4je02754:31572277
c3h7c220:31478652
ge8j1254_inline_auto_hint_haiku:31490510
cp_cls_c_1081:31454833
conptydll_true:31498968
e9c30283:31461165
c9b86496:31447327
ei9d7968:31496641
nes-extended-on:31455476
chat:31457767
8hig5102:31480529
89g7j272:31518289
i2gc6536:31499202
52612955:31516516
h08i8180_copy:31475368
ddid_t:31478206
hmra_i5g22:31518061
7df3h592:31512476
cp_cls_t_1082:31535311
logging_enabled_new:31498466
j0d79568:31499440
jb_cp_cls_t_632:31543129
56dj4588:31512888
32d7697:31512328
ha629193:31508444
a1ije391_t:31540920
jbcp_cls_pctr_t:31531130
61138546:31518536
cp_intellij_t_nes:31548657
gf14b233:31526830
ahp-both-windows:31556933
ihg5j128:31534457
7g2b5551:31542111
sandbox-ui-on-2:31543161
enable_editor_pane_layout:31569726
allow-none:31555437
36h42362:31564511
c7c27ce7:31554789
1h923230:31564177
1532g621_copy:31554320
treatment-23-1:31555779
unuse_dynamic_mcp:31555281
0d8dfbc3:31570291
switchtoauto:31559321
0c1h4866:31566224
vrbsty_fls:31561059
session-archive:31558132
5b8j3302:31564601
mangle-name-control:31572633
multiv2:31574985
2bfb8b39:31576696
permission_prompt_treatment:1332566
ccr_pr_nudge_auto_review:1319472
vsc_wsm_t:1340632
jidc7660:1370295
auto_mode_control:1367906
14b85561:1348997

</details>

<!-- generated by issue reporter -->

[arpankanwer]

Justin Chen (@justschen) — I hit the same retry-loop pattern and opened #334129 as a minimal proposal (skip auto-retry + actionable error, mirrors isContextOverflowBadRequest). Happy to adjust or close if you're already handling it internally.