[codex] Accept string input for Python turns (#23162)

## Summary
- Allow thread.turn and turn.steer, including async variants, to accept
RunInput so plain strings work alongside typed input objects.
- Export RunInput and update the SDK artifact generator so regenerated
turn methods keep the same signature and normalization.
- Update docs, examples, notebook cells, and tests to use string
shorthand for text-only turns while keeping typed inputs for multimodal
input.

## Validation
- uv run --extra dev ruff format .
- uv run --extra dev ruff check --output-format=github .
- python3 -m py_compile sdk/python/src/openai_codex/__init__.py
sdk/python/src/openai_codex/api.py
sdk/python/src/openai_codex/_inputs.py
sdk/python/scripts/update_sdk_artifacts.py
sdk/python/tests/test_public_api_signatures.py
sdk/python/tests/test_app_server_streaming.py
sdk/python/tests/test_app_server_turn_controls.py
sdk/python/tests/test_real_app_server_integration.py
- python3 -c "import json;
json.load(open('sdk/python/notebooks/sdk_walkthrough.ipynb'))"
- sdk/python/.venv/bin/python -c "import inspect, openai_codex; from
openai_codex import Thread, AsyncThread, TurnHandle, AsyncTurnHandle,
RunInput; funcs=[Thread.run, Thread.turn, AsyncThread.run,
AsyncThread.turn, TurnHandle.steer, AsyncTurnHandle.steer]; assert
all(inspect.signature(fn).parameters['input'].annotation == 'RunInput'
for fn in funcs); assert RunInput is openai_codex.RunInput"

sdk/python/docs/api-reference.md

@@ -3,7 +3,7 @@
 Public surface of `openai_codex` for app-server v2.
 
 This SDK surface is experimental. Turn streams are routed by turn ID so one client can consume multiple active turns concurrently.
-Thread and turn starts expose `approval_mode`. `ApprovalMode.auto_review` is the default; use `ApprovalMode.deny_all` to deny escalated permissions.
+Thread starts default to `ApprovalMode.auto_review`; turn starts accept an optional `approval_mode` override.
 
 ## Package Entry
 
@@ -23,6 +23,7 @@ from openai_codex import (
     TurnResult,
     Input,
     InputItem,
+    RunInput,
     TextInput,
     ImageInput,
     LocalImageInput,
@@ -147,16 +148,16 @@ attempt. API-key login completes synchronously and does not return a handle.
 
 ### Thread
 
-- `run(input: str | Input, *, approval_mode=ApprovalMode.auto_review, cwd=None, effort=None, model=None, output_schema=None, personality=None, sandbox_policy=None, service_tier=None, summary=None) -> TurnResult`
-- `turn(input: Input, *, approval_mode=ApprovalMode.auto_review, cwd=None, effort=None, model=None, output_schema=None, personality=None, sandbox_policy=None, summary=None) -> TurnHandle`
+- `run(input: str | Input, *, approval_mode=None, cwd=None, effort=None, model=None, output_schema=None, personality=None, sandbox_policy=None, service_tier=None, summary=None) -> TurnResult`
+- `turn(input: str | Input, *, approval_mode=None, cwd=None, effort=None, model=None, output_schema=None, personality=None, sandbox_policy=None, service_tier=None, summary=None) -> TurnHandle`
 - `read(*, include_turns: bool = False) -> ThreadReadResponse`
 - `set_name(name: str) -> ThreadSetNameResponse`
 - `compact() -> ThreadCompactStartResponse`
 
 ### AsyncThread
 
-- `run(input: str | Input, *, approval_mode=ApprovalMode.auto_review, cwd=None, effort=None, model=None, output_schema=None, personality=None, sandbox_policy=None, service_tier=None, summary=None) -> Awaitable[TurnResult]`
-- `turn(input: Input, *, approval_mode=ApprovalMode.auto_review, cwd=None, effort=None, model=None, output_schema=None, personality=None, sandbox_policy=None, summary=None) -> Awaitable[AsyncTurnHandle]`
+- `run(input: str | Input, *, approval_mode=None, cwd=None, effort=None, model=None, output_schema=None, personality=None, sandbox_policy=None, service_tier=None, summary=None) -> Awaitable[TurnResult]`
+- `turn(input: str | Input, *, approval_mode=None, cwd=None, effort=None, model=None, output_schema=None, personality=None, sandbox_policy=None, service_tier=None, summary=None) -> Awaitable[AsyncTurnHandle]`
 - `read(*, include_turns: bool = False) -> Awaitable[ThreadReadResponse]`
 - `set_name(name: str) -> Awaitable[ThreadSetNameResponse]`
 - `compact() -> Awaitable[ThreadCompactStartResponse]`
@@ -185,7 +186,7 @@ Use `turn(...)` when you need low-level turn control (`stream()`, `steer()`,
 
 ### TurnHandle
 
-- `steer(input: Input) -> TurnSteerResponse`
+- `steer(input: str | Input) -> TurnSteerResponse`
 - `interrupt() -> TurnInterruptResponse`
 - `stream() -> Iterator[Notification]`
 - `run() -> TurnResult`
@@ -197,7 +198,7 @@ Behavior notes:
 
 ### AsyncTurnHandle
 
-- `steer(input: Input) -> Awaitable[TurnSteerResponse]`
+- `steer(input: str | Input) -> Awaitable[TurnSteerResponse]`
 - `interrupt() -> Awaitable[TurnInterruptResponse]`
 - `stream() -> AsyncIterator[Notification]`
 - `run() -> Awaitable[TurnResult]`
@@ -218,8 +219,12 @@ Behavior notes:
 
 InputItem = TextInput | ImageInput | LocalImageInput | SkillInput | MentionInput
 Input = list[InputItem] | InputItem
+RunInput = Input | str
 ```
 
+Use a plain `str` as shorthand for `TextInput(...)` anywhere a turn input is accepted:
+`thread.run("...")`, `thread.turn("...")`, and `turn.steer("...")`.
+
 ## Public Types
 
 The SDK wrappers return and accept public app-server models wherever possible:

sdk/python/docs/getting-started.md

@@ -72,6 +72,7 @@ What happened:
 - `thread_start(...)` created a thread.
 - `thread.run("...")` started a turn, consumed events until completion, and returned `TurnResult` with turn metadata, final assistant response, collected items, and usage.
 - `result.final_response` is `None` when no final-answer or phase-less assistant message item completes for the turn.
+- plain strings are accepted anywhere a turn input is accepted; typed inputs are still available for multimodal and structured cases
 - use `thread.turn(...)` when you need a `TurnHandle` for streaming, steering, or interrupting before collecting `TurnResult`
 - one client can consume multiple active turns concurrently; turn streams are routed by turn ID