## Why Helper threads such as task title generation can request a model ID that is valid for the default OpenAI provider but unavailable from the active provider. With Amazon Bedrock, `gpt-5.4-mini` is rejected while the provider static catalog exposes Bedrock model IDs such as `openai.gpt-5.5` and `openai.gpt-5.4`. This causes repeated background 404s and can surface a misleading turn error even when the main turn succeeds. Clients need an explicit way to ask app-server to resolve an unavailable helper model to the active provider default. That fallback must remain limited to providers with an authoritative static catalog so custom or dynamically discovered model IDs are not rewritten based on an incomplete catalog. Fixes #28741. ## What changed - Add the experimental `allowProviderModelFallback` option to `thread/start`, defaulting to `false` to preserve existing behavior. - Thread the option through thread creation and model selection. - When enabled for a static model manager, preserve requested models present in the catalog and replace unavailable models with the provider default. - Continue preserving explicit model IDs for dynamic model managers without fetching a catalog solely to validate them. - Document the new `thread/start` behavior in the app-server API overview. ## Test Temporary test-client harness: ``` ThreadStartParams { model: Some("gpt-5.4-mini".to_string()), allow_provider_model_fallback: true, ..Default::default() } ``` Command: ``` CODEX_HOME=/tmp/codex-bedrock-thread-start-home \ CODEX_E2E_BEDROCK_THREAD_START_ONLY=1 \ ./target/debug/codex-app-server-test-client \ --codex-bin ./target/debug/codex \ -c 'model_provider="amazon-bedrock"' \ send-message-v2 --experimental-api ignored ``` Relevant output: ``` > "method": "thread/start", > "params": { > "model": "gpt-5.4-mini", > "modelProvider": null, > "allowProviderModelFallback": true, > ... > } < "result": { < "model": "openai.gpt-5.5", < "modelProvider": "amazon-bedrock", < ... < } ```
Codex CLI is a coding agent from OpenAI that runs locally on your computer.
If you want Codex in your code editor (VS Code, Cursor, Windsurf), install in your IDE.
If you want the desktop app experience, run
codex app or visit the Codex App page.
If you are looking for the cloud-based agent from OpenAI, Codex Web, go to chatgpt.com/codex.
Quickstart
Installing and running Codex CLI
Run the following on Mac or Linux to install Codex CLI:
curl -fsSL https://chatgpt.com/codex/install.sh | sh
Run the following on Windows to install Codex CLI:
powershell -ExecutionPolicy ByPass -c "irm https://chatgpt.com/codex/install.ps1 | iex"
Codex CLI can also be installed via the following package managers:
# Install using npm
npm install -g @openai/codex
# Install using Homebrew
brew install --cask codex
Then simply run codex to get started.
You can also go to the latest GitHub Release and download the appropriate binary for your platform.
Each GitHub Release contains many executables, but in practice, you likely want one of these:
- macOS
- Apple Silicon/arm64:
codex-aarch64-apple-darwin.tar.gz - x86_64 (older Mac hardware):
codex-x86_64-apple-darwin.tar.gz
- Apple Silicon/arm64:
- Linux
- x86_64:
codex-x86_64-unknown-linux-musl.tar.gz - arm64:
codex-aarch64-unknown-linux-musl.tar.gz
- x86_64:
Each archive contains a single entry with the platform baked into the name (e.g., codex-x86_64-unknown-linux-musl), so you likely want to rename it to codex after extracting it.
Using Codex with your ChatGPT plan
Run codex and select Sign in with ChatGPT. We recommend signing into your ChatGPT account to use Codex as part of your Plus, Pro, Business, Edu, or Enterprise plan. Learn more about what's included in your ChatGPT plan.
You can also use Codex with an API key, but this requires additional setup.
Docs
This repository is licensed under the Apache-2.0 License.
