**Feature negotiation mismatch in 26.506.31421 — JS bundle requests features Rust app-server doesn't support, triggers extension host termination

What version of the IDE extension are you using?

openai.chatgpt-26.506.31421-linux-x64

What subscription do you have?

ChatGPT Plus

Which IDE are you using?

Codex VS code Extension for WSL

What platform is your computer?

Windows 11 host, WSL2 Ubuntu 22.04

What issue are you seeing?

Summary

In Codex VSCode extension v26.506.31421 on WSL2, the JS bundle calls experimentalFeature/enablement/set for features the bundled Rust codex app-server doesn't recognize, returning -32600 Invalid Request errors. Combined with respawn-loop behavior of the app-server, this causes the VSCode extension host to be terminated by the renderer, taking down concurrent extensions (Claude Code, etc.) — not just Codex.

Affected version

openai.chatgpt-26.506.31421-linux-x64 (current marketplace version as of 2026-05-09)

Environment

• Windows 11 host, WSL2 Ubuntu 22.04

• VSCode 1.105

• Coexisting extensions: anthropic.claude-code, kilocode.kilo-code, kegcode.keg-code

• Bubblewrap installed (separate prereq)

Symptoms

• Sign in button: no openExternal event, no browser opens

• Model picker: stuck on "Custom"

• Past chats: don't load

• Interacting with Codex panel terminates the extension host, killing concurrent extensions

Evidence (from Codex.log)

JS sends 14 features:

enable_request_compression, collaboration_modes, personality, request_rule, image_generation, image_detail_original, workspace_dependencies, guardian_approval, apply_patch_streaming_events, workspace_owner_usage_nudge, apps, plugins, tool_search, tool_call_mcp_elicitation

Rust supports 7:

apps, memories, plugins, remote_control, tool_search, tool_suggest, tool_call_mcp_elicitation

Each unrecognized feature → -32600 unsupported feature enablement error.

Reproducer

1. Fresh VSCode/WSL, no prior ~/.codex

1. Install 26.506.31421

1. Open workspace, click Codex panel

1. Tail ~/.vscode-server/data/logs/<latest>/exthost1/openai.chatgpt/Codex.log

1. Click "Sign in with ChatGPT" — observe nothing happens, no openExternal event logged

1. App-server respawns every ~30s–2min (multiple initialize id=1 log lines with ConnectionId(0))

1. Within minutes, extension host receives terminate from renderer, kills all extensions in the host

Suggested fixes

1. Add feature negotiation to the initialize response so JS only requests supported features

1. Make unknown features a WARN not a -32600 hard error

1. Pin JS bundle versions to specific compatible Rust binary versions

Workaround

Downgrade to 26.422.71525 (or any pre-26.506 version). Auth, sign-in, models, chat history all work.

What steps can reproduce the bug?

Reproducer

1. Fresh VSCode/WSL, no prior ~/.codex

1. Install 26.506.31421

1. Open workspace, click Codex panel

1. Tail ~/.vscode-server/data/logs/<latest>/exthost1/openai.chatgpt/Codex.log

1. Click "Sign in with ChatGPT" — observe nothing happens, no openExternal event logged

1. App-server respawns every ~30s–2min (multiple initialize id=1 log lines with ConnectionId(0))

1. Within minutes, extension host receives terminate from renderer, kills all extensions in the host

What is the expected behavior?

## Summary



In Codex VSCode extension v26.506.31421 on WSL2, the JS bundle calls `experimentalFeature/enablement/set` for features the bundled Rust `codex app-server` doesn't recognize, returning `-32600 Invalid Request` errors. Combined with respawn-loop behavior of the app-server, this causes the VSCode extension host to be terminated by the renderer, taking down concurrent extensions (Claude Code, etc.) — not just Codex.



## Affected version



`openai.chatgpt-26.506.31421-linux-x64` (current marketplace version as of 2026-05-09)



## Environment



- Windows 11 host, WSL2 Ubuntu 22.04

- VSCode 1.105

- Coexisting extensions: anthropic.claude-code, kilocode.kilo-code, kegcode.keg-code

- Bubblewrap installed (separate prereq)



## Symptoms



- Sign in button: no `openExternal` event, no browser opens

- Model picker: stuck on "Custom"

- Past chats: don't load

- Interacting with Codex panel terminates the extension host, killing concurrent extensions



## Evidence (from Codex.log)



JS sends 14 features:

`enable_request_compression, collaboration_modes, personality, request_rule, image_generation, image_detail_original, workspace_dependencies, guardian_approval, apply_patch_streaming_events, workspace_owner_usage_nudge, apps, plugins, tool_search, tool_call_mcp_elicitation`



Rust supports 7:

`apps, memories, plugins, remote_control, tool_search, tool_suggest, tool_call_mcp_elicitation`



Each unrecognized feature → `-32600 unsupported feature enablement` error.



## Reproducer



1. Fresh VSCode/WSL, no prior `~/.codex`

2. Install 26.506.31421

3. Open workspace, click Codex panel

4. Tail `~/.vscode-server/data/logs/<latest>/exthost1/openai.chatgpt/Codex.log`

5. Click "Sign in with ChatGPT" — observe nothing happens, no `openExternal` event logged

6. App-server respawns every ~30s–2min (multiple `initialize id=1` log lines with `ConnectionId(0)`)

7. Within minutes, extension host receives terminate from renderer, kills

Additional information

_No response_