Coroutine calls

A call request returns one result or one error envelope. The bridge awaits a Python awaitable before it serializes the result. It rejects generators and async generators. It does not expose tasks, streams, retries, or cached results.

Node subprocess

The Python JSONL server handles requests in order. A synchronous call runs directly. For an awaitable result, handle_call() wraps it in a coroutine and uses asyncio.run(). Python 3.10 through 3.12 create and close one event loop for that call. Pending background tasks do not survive the call.

The call must return an awaitable that can run on this new loop. A Future bound to another loop fails in the normal Python error envelope. A synchronous function that needs a running loop before it returns must create that loop itself or use an async def function.

After a request reaches stdin, a timeout or abort retires that Python process. The transport rejects other requests on the same process and starts a new process for later calls. Replacement runs the configured worker warmup. Python state held only in the retired process is lost. A request that times out before its first write does not retire the process.

Retirement sends SIGTERM first. If the child stays alive, it sends SIGKILL after one second and waits for the child to exit. A failed kill blocks replacement of that process generation. The pool keeps the worker slot until disposal succeeds. If cleanup fails, the pool rejects new leases and keeps the child handle for a later disposal retry.

Disposal kills the process and rejects pending requests. The caller receives one timeout, abort, or disposal error. A retired process cannot send a late response into a replacement process. A timeout does not cancel Python code in place; process retirement stops code that does not cooperate with cancellation.

Pyodide

Pyodide owns its WebLoop. The bootstrap registers a task by request ID before it returns the task to JavaScript. The transport awaits the task and destroys its Pyodide proxies after the task settles. Timeout, abort, and disposal call Task.cancel() for that request. The task map removes settled and cancelled tasks.

Cancellation is cooperative. Python receives CancelledError at an await. The caller receives one timeout, abort, or disposal error. The transport consumes a late task rejection without sending another response.

CPU-bound Python on the browser thread can block both the JavaScript timer and the Pyodide event loop. This transport cannot stop it at a deadline. Pyodide documents interrupt buffers for web workers. The bridge does not install an interrupt buffer or terminate a worker. Host applications must manage their own worker lifecycle if they need that limit.