Codex long-thread compaction 404s on `/backend-api/codex/responses/compactsvg` and traps conversation

Summary

On long-running Codex conversations, automatic context compaction can fail with a 404 against an unexpected compactsvg endpoint. Once the thread reaches the compaction threshold, subsequent prompts in that same conversation can repeatedly fail because compaction is retriggered.

This appears consistent with the broader remote-compaction regressions / client-server routing mismatches reported recently, but the endpoint here is notably /compactsvg rather than the more commonly reported /compact.

Error

Error running remote compact task: unexpected status 404 Not Found: {"detail":"Not Found"}, url: https://chatgpt.com/backend-api/codex/responses/compactsvg

Request ID:

2855dc17-890c-4271-878a-7f2d37cca515

CF Ray:

a37f8c187aa9efa9-EWR

Environment

• Codex Desktop being used through Conductor on macOS / Apple Silicon
• Long autonomous / multi-step Codex sessions are affected most often because they cross the automatic compaction threshold
• Failure appears during automatic context compaction, not while executing repository code

Observed behavior

1. Work normally in a Codex thread until it becomes long enough to require automatic compaction.
2. Codex attempts a remote compact task.
3. Request is sent to https://chatgpt.com/backend-api/codex/responses/compactsvg.
4. Server returns 404 Not Found.
5. The conversation can become effectively poisoned: another prompt retriggers compaction and fails again, while moving to a fresh conversation allows work to continue.

Expected behavior

Automatic compaction should use the currently supported compaction path / normal-turn infrastructure and allow the conversation to continue without user intervention.

Additional context

The compactsvg suffix seems especially suspicious. Public reports of this class of failure generally reference /backend-api/codex/responses/compact; I could not find another public report specifically referencing /compactsvg. This may indicate a stale or experimental route, a malformed endpoint selection, or a client/server feature-version mismatch.

Because the bug tends to appear only after substantial work has accumulated in a thread, it has a high recovery cost: users may be forced to abandon a conversation precisely when it contains the most context.

Would be useful to confirm whether compactsvg is a valid route in any current client configuration and, if not, identify which feature/config path can emit it.

The report names no source file or test; start by tracing the request path that produces /backend-api/codex/responses/compactsvg and checking the client configuration or feature path that selects it. Compare that path with the supported /compact route and confirm whether the endpoint is emitted by the client or reflects a server mismatch. Done means the source of the invalid route and the affected compaction behavior are identified.