# _runtime

URL: /pounce/api/_runtime/
Section: api
Description: Runtime detection utilities.

Detects GIL state and determines the appropriate worker mode for the
current Python interpreter. Used by the supervisor to decide between
thread-based (nogil) and process-based (GIL) worker spawning.

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Module

#
`_runtime`

Runtime detection utilities.

Detects GIL state and determines the appropriate worker mode for the
current Python interpreter. Used by the supervisor to decide between
thread-based (nogil) and process-based (GIL) worker spawning.

2Classes8Functions

## Classes

`WorkerMode`

0

▼

Worker spawning strategy.

Bases:

`StrEnum`

Worker spawning strategy.

`WorkerExecutionMode`

0

▼

Worker execution model.

Bases:

`StrEnum`

Worker execution model.

## Functions

`is_gil_enabled`

0

`bool`

▼

Check whether the GIL is active in the current interpreter.

Returns the runtim…

`def is_gil_enabled() -> bool`

Check whether the GIL is active in the current interpreter.

Returns the runtime state, which can be`True`on either a standard
build or a free-threaded build started with its GIL enabled. Falls back to
`True` on Python < 3.13 where `sys._is_gil_enabled`does not exist.

##### Returns

`bool`

`is_free_threaded_build`

0

`bool`

▼

Return whether this interpreter was compiled with free-threading support.

This…

`def is_free_threaded_build() -> bool`

Return whether this interpreter was compiled with free-threading support.

This is distinct from `is_gil_enabled` (/pounce/api/_runtime/#is_gil_enabled)(): a free-threaded build can
still start with its GIL enabled, while a standard build cannot disable it.

##### Returns

`bool`

`has_subinterpreters`

0

`bool`

▼

Check whether ``concurrent.interpreters`` is available (Python 3.14+).

`def has_subinterpreters() -> bool`

##### Returns

`bool`

`detect_worker_mode`

0

`WorkerMode (/pounce/api/_runtime/#WorkerMode)`

▼

Choose the worker spawning strategy based on GIL state.

`def detect_worker_mode() -> WorkerMode`

##### Returns

`WorkerMode (/pounce/api/_runtime/#WorkerMode)`

`default_worker_count`

0

`int`

▼

Return a sensible default worker count based on available CPUs.

Returns ``os.c…

`def default_worker_count() -> int`

Return a sensible default worker count based on available CPUs.

Returns`os.cpu_count()` or `1`when the CPU count cannot be
determined.

##### Returns

`int`

`resolve_worker_execution_mode`

1

`WorkerExecutionMode (/pounce/api/_runtime/#WorkerExecutionMode)`

▼

Resolve the effective worker execution mode.

`def resolve_worker_execution_mode(worker_mode: str) -> WorkerExecutionMode`

##### Parameters

Name
Type
Description

`worker_mode`
`str`

Config value ("auto", "sync", "async", "subinterpreter").

##### Returns

`WorkerExecutionMode (/pounce/api/_runtime/#WorkerExecutionMode)`

`resolve_worker_model`

2

`str`

▼

Return the actual spawning and execution model for this runtime.

A single work…

`def resolve_worker_model(worker_mode: str, worker_count: int) -> str`

Return the actual spawning and execution model for this runtime.

A single worker uses the direct async server path. Multi-worker`auto`
uses sync thread workers on a free-threaded build and async process workers
on a GIL build. Explicit subinterpreter mode always uses isolated async
workers, including when the configured worker count is one.

##### Parameters

Name
Type
Description

`worker_mode`
`str`

`worker_count`
`int`

##### Returns

`str`

`validate_subinterpreter_app_path`

2

`None`

▼

Fail at the embedding boundary when isolated workers cannot import the app.

`def validate_subinterpreter_app_path(worker_mode: str, app_path: str | None) -> None`

##### Parameters

Name
Type
Description

`worker_mode`
`str`

`app_path`
`str | None`