FAQ

Thread vs turn

A Thread is conversation state.
A Turn is one model execution inside that thread.
Multi-turn chat means multiple turns on the same Thread.

`run()` vs `stream()`

Turn.run() is the easiest path. It consumes events until completion and returns TurnResult.
Turn.stream() yields raw notifications (Notification) so you can react event-by-event.

Choose run() for most apps. Choose stream() for progress UIs, custom timeout logic, or custom parsing.

Sync vs async clients

Codex is the minimal sync SDK and best default.
AsyncAppServerClient wraps the sync transport with asyncio.to_thread(...) for async-friendly call sites.

If your app is not already async, stay with Codex.

`thread(...)` vs `thread_resume(...)`

codex.thread(thread_id) only binds a local helper to an existing thread ID.
codex.thread_resume(thread_id, ...) performs a thread/resume RPC and can apply overrides (model, instructions, sandbox, etc.).

Use thread(...) for simple continuation. Use thread_resume(...) when you need explicit resume semantics or override fields.

Why does constructor fail?

Codex() is eager: it starts transport and calls initialize in __init__.

Common causes:

published runtime package (codex-cli-bin) is not installed
local codex_bin override points to a missing file
local auth/session is missing
incompatible/old app-server

Maintainers stage releases by building the core SDK once, the bundled SDK metapackage once, and the runtime once per platform with the same pinned runtime version. Publish codex-cli-bin as platform wheels only; do not publish an sdist. Published Python package versions should match the rust-v... release tag:

cd sdk/python
python scripts/update_sdk_artifacts.py generate-types
python scripts/update_sdk_artifacts.py \
  stage-sdk-core \
  /tmp/codex-python-release/codex-app-server-sdk-core \
  --sdk-version 1.2.3
python scripts/update_sdk_artifacts.py \
  stage-sdk \
  /tmp/codex-python-release/codex-app-server-sdk \
  --sdk-version 1.2.3 \
  --runtime-version 1.2.3
python scripts/update_sdk_artifacts.py \
  stage-runtime \
  /tmp/codex-python-release/codex-cli-bin \
  /path/to/codex \
  --runtime-version 1.2.3

Why does a turn "hang"?

A turn is complete only when turn/completed arrives for that turn ID.

run() waits for this automatically.
With stream(), make sure you keep consuming notifications until completion.

How do I retry safely?

Use retry_on_overload(...) for transient overload failures (ServerBusyError).

Do not blindly retry all errors. For InvalidParamsError or MethodNotFoundError, fix inputs/version compatibility instead.

Common pitfalls

Starting a new thread for every prompt when you wanted continuity.
Forgetting to close() (or not using with Codex() as codex:).
Ignoring TurnResult.status and TurnResult.error.
Mixing SDK input classes with raw dicts incorrectly in minimal API paths.

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FAQ