CLI TUI: /provider slash command to switch model_provider mid-session

What variant of Codex are you using?

CLI (TUI)

What feature would you like to see?

A /provider slash command in the CLI TUI that switches model_provider mid-session, with these properties:

• Lists all providers registered in the active config (whatever [model_providers.*] tables exist) plus the implicit OpenAI subscription backend
• Switching rebinds the next turn's model_provider, model, and env_key to the chosen profile's settings, without losing the existing conversation history
• Optionally accepts a profile name as argument (/provider minimax jumps directly; bare /provider opens a picker)
• The TUI's /model selector should also surface the new provider's models when invoked after a switch

Today the only way to switch provider is to exit the TUI and rerun codex --profile <name>, which loses the entire conversation history. cx fork --last -p <new> (mentioned in community docs) preserves history but still forces a new TUI session. The Codex Desktop UI gets a sidebar profile picker (recently requested in #39527) — the CLI TUI should have parity.

Additional information

Use case: I maintain a single-machine registry of ~17 named provider profiles (minimax, ZAI glm-5.3, xiaomi mimo-v2.5-pro, qwen-3.7-plus, volc ark-code-latest, 10-0..3 direct sglang, etc.). Mid-task I regularly want to ask a second model for a sanity check on a refactor — without losing the refactor's conversation history, and without opening a new terminal.

Today's workaround: I wrote a wrapper bin/cx-switch that runs codex fork --last -p <new> to fork the current session with a new provider. This preserves history but is a fork (new conversation ID, the original session stays paused in codex resume history). It works, but it's not in-TUI and breaks the "single running session" mental model.

What the schema already supports: The v2 app-server protocol (ThreadStartParams, ThreadForkParams, ThreadResumeParams) accepts modelProvider overrides when starting a new thread. The TurnStartParams schema accepts model, cwd, effort, etc. as per-turn overrides, but NOT modelProvider. Implementing /provider would require either:

1. A new setSessionProvider RPC (or extending TurnStartParams with modelProvider) on the app-server protocol, then binding it to a /provider slash command in the TUI frontend, or
2. A pure-TUI-side client that forks the current thread internally on /provider <name> and discards the old session pointer. This is the cheaper ship path.

Related issues:

• #4849 — "Make config.toml profiles selectable via CLI" (closed 2026-08-05 by maintainer with one-liner "Named configurations are selectable with --profile." — that's the wrapper workaround we already use; not in-TUI). The same issue proposed /provider as one of the UX options.
• #35728 — "show sessions from all providers in the sidebar and make model switching provider-aware" (open, Desktop-focused)
• #39527 — "Add a config profile selector to Codex Desktop" (open, Desktop-only)
• #38104 — "Support selecting a config profile for app-server and Desktop via environment variable" (open, CODEX_CONFIG_PROFILE env var; would help non-TUI launchers but not in-TUI)
• #22483 — "Disconnected when using custom provider and no ability to switch providers or profiles" (open, related but bug-shaped)

Why I'm filing this even though #4849 was closed: the maintainer's "use --profile" answer sidesteps the actual UX problem (history loss + new terminal) and the OP specifically called out "/provider" as the natural UX. The Discord/community thread linked from #4849 has multiple users (e.g. @tom-nash, 13 thumbs up on comment dated 2026-02-02) describing the same problem. The cluster of related open issues (#35728, #39527, #38104) shows this is a recurring ask across CLI / Desktop / app-server surfaces.

If a quick win is possible via a /provider slash command bound to a ThreadForkParams + modelProvider override call, that would close the most painful part of the gap without waiting for broader provider-aware session work.

Start by tracing the CLI TUI slash-command handling and the app-server ThreadForkParams and TurnStartParams paths mentioned in the issue. Compare the setSessionProvider and per-turn override options, then determine how /model should read the selected provider's models. Done means switching provider in one running TUI preserves conversation history and updates the next turn's provider, model, and env_key.