[Linux Desktop 26.930.61225] New-chat model selection reverts to GPT-5.5; switching after start works #51301

What version of the Codex App are you using?

Linux desktop package 26.930.61225; bundled codex-cli/app-server 0.160.1. Versions verified from installed package metadata and the bundled executable.

What platform is your computer?

Linux x86_64, local desktop environment.

What issue are you seeing?

After updating, the user reports that opening a new chat forces the model to GPT-5.5: choosing another model automatically switches the model picker back to GPT-5.5.

This concerns selection during new-chat initialization. Other models can run after the chat has started: subsequent switching to GPT-6.1-Sol worked in the inspected chat.

What steps can reproduce the bug?

User-reported reproduction:

1. Open the updated Linux desktop app.
2. Start a new local chat.
3. Select a model other than GPT-5.5.
4. Observe the picker automatically revert to GPT-5.5.
5. Repeat with other available models.

The user reports this consistently for new chats. Picker interactions have not been independently replayed by the investigator.

What is the expected behavior?

An explicitly selected available model should remain selected and be used for the first message. If unavailable, display an explanation rather than silently reverting.

Additional information

Read-only investigation confirmed this sequence, summarized without raw logs or identifiers:

1. A new local chat's initial turn used GPT-5.5.
2. After that turn had started and was interrupted, thread settings accepted GPT-6.1-Sol.
3. The next turn and subsequent ordinary Responses requests used GPT-6.1-Sol.

Thus there is evidence of GPT-5.5 at first-turn initialization and successful switching afterward. It does not independently establish the precise picker reversion sequence or root cause.

Potential areas to investigate are new-chat default/selection initialization, available-model filtering, and collaboration-mode settings synchronization. These are hypotheses, not confirmed causes.

Related:

• Model selection reverts to gpt-6-astra in every new remote chat #47710: new remote chats revert to gpt-6-astra on macOS. This report concerns local Linux chats and GPT-5.5.
• Model selection immediately reverts to default model after choosing a different one #10875: older general desktop picker-reversion report.

Submitted separately at the user's request to document the current Linux build and the first-turn versus post-start boundary. Maintainers can consolidate it into an existing tracker if appropriate.

No raw logs, session identifiers, account details, subscription information, local paths, configuration contents, or private prompts are included.