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baml_bridge

Python bindings for the BAML runtime (powered by bex_engine).

baml_bridge is the bridge layer that generated baml_sdk packages import at runtime: it provides the BamlRuntime singleton, the protobuf encoder/decoder and the function/method factories.

from baml_bridge import BamlRuntime

rt = BamlRuntime.initialize_runtime(
    root_path=".",
    files={"main.baml": baml_source},
)

This package is generally consumed indirectly via the code generated by baml-cli generate --target python — direct use is reserved for runtime authors and bridge tests.

Python callback execution

Passing a Python callable to BAML uses the environment of the call that invokes it. Reusing a callback across threads, event loops, or requests does not retain its registration environment.

BAML entry Python callback Execution environment
Synchronous Synchronous Calling Python thread, with its current context
Synchronous Coroutine result Bridge-owned worker loop, with copied caller context
Asynchronous Synchronous or coroutine result Originating application loop, with copied entry context

Each dispatch of an async entry receives a separate copy of its application ContextVars. Callback writes do not change the awaiting task's context or another dispatch's context. An async callback need not run in the caller's exact asyncio.Task.

A synchronous entry blocks its calling thread, including any application loop running there. Coroutine callbacks of that entry must use resources of their executing worker loop. Awaiting resources owned by the blocked loop is unsupported.

Returned BAML closures support closure(...) and await closure.call_async(...). Passing a closure back into BAML preserves its native function handle. Each new invocation selects its own environment.

Cancelling a BAML call cancels executing coroutine callbacks on their owning loops. Callback tasks retain their arguments and context until their bodies and async cleanup finish. Cancellation does not interrupt a synchronous Python body. A callback that suppresses cancellation may finish later; its result does not revive the cancelled BAML call.

Requirements

  • Python 3.10+
  • protobuf >= 6.31.1

License

Apache-2.0

Metadata

Release files for baml-bridge 0.21.1.dev2026100900

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baml_bridge-0.21.1.dev2026100900-cp310-abi3-musllinux_1_1_x86_64.whl CPython 3.10 abi3 Linux musl 1.1+ x86-64 Details
baml_bridge-0.21.1.dev2026100900-cp310-abi3-musllinux_1_1_aarch64.whl CPython 3.10 abi3 Linux musl 1.1+ ARM64 Details
baml_bridge-0.21.1.dev2026100900-cp310-abi3-manylinux_2_24_aarch64.whl CPython 3.10 abi3 Linux glibc 2.24+ ARM64 Details
baml_bridge-0.21.1.dev2026100900-cp310-abi3-manylinux_2_17_x86_64.manylinux2014_x86_64.whl CPython 3.10 abi3 Linux glibc 2.17+ x86-64 Details
baml_bridge-0.21.1.dev2026100900-cp310-abi3-macosx_11_0_arm64.whl CPython 3.10 abi3 macOS 11.0+ ARM64 Details
baml_bridge-0.21.1.dev2026100900-cp310-abi3-macosx_10_12_x86_64.whl CPython 3.10 abi3 macOS 10.12+ x86-64 Details

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Release history Release notifications | RSS feed

0.22.2

8 release files

0.22.1

8 release files

0.22.0

8 release files

This release

0.20.1

8 release files

0.20.0

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0.19.0

8 release files

0.17.0

8 release files

0.16.0

8 release files

0.15.0

8 release files

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