Crate baml 

BAML Runtime for Rust

This crate provides the runtime support for BAML-generated Rust code. Users should not import from this crate directly - instead, use the generated baml_client crate which re-exports necessary types.

Derive Macros

Use #[derive(BamlEncode)] and #[derive(BamlDecode)] to automatically implement serialization for your types:

use baml::{BamlEncode, BamlDecode};

#[derive(BamlEncode, BamlDecode)]
#[baml(name = "Person")]
struct Person {
    name: String,
    #[baml(name = "years_old")]
    age: i64,
}

Macros

baml_unreachable

Panics with a user-friendly error message for internal/unreachable errors.

Structs

AsyncStreamingCall

Async streaming call that yields partial results and a final response

Audio

Audio media type

BamlRuntime

Handle to the BAML runtime

CancellationToken

Token for checking, waiting on, and triggering cancellation.

Check

Individual check result

Checked

Result of a @check constraint

ClassBuilder

Builder for class types

ClassPropertyBuilder

Builder for class properties

ClientRegistry

A registry for configuring LLM clients at runtime.

Collector

Collector for gathering telemetry from function calls

DynamicClass

A fully dynamic class - all fields accessed via .get()

DynamicEnum

A dynamic enum - name and value as strings

DynamicUnion

A dynamic union - wraps a value with union metadata

EnumBuilder

Builder for enum types

EnumValueBuilder

Builder for enum values

FunctionArgs

Arguments for a BAML function call

FunctionLog

Log entry for a function call

HTTPBody

HTTP request or response body

HTTPRequest

HTTP request details

HTTPResponse

HTTP response details

Image

Image media type

LLMCall

Details of a single LLM API call

LLMStreamCall

Details of a streaming LLM API call

Pdf

PDF media type

SSEResponse

Server-Sent Event response chunk

StreamState

Streaming state wrapper for @stream.with_state

StreamTiming

Timing information for a streaming call

StreamingCall

Result of a streaming function call

Timing

Timing information for a function or LLM call

TypeBuilder

Builder for constructing BAML types at runtime

TypeDef

A dynamically constructed BAML type

Usage

Token usage statistics

Video

Video media type

Enums

BamlError

BAML runtime errors

BamlValue

A dynamically-typed BAML value, parameterized by two type enums:

CheckStatus

Status of a check constraint

LLMCallKind

Either an LLMCall or LLMStreamCall

LogType

Type of function log entry

StreamEvent

Event from a streaming function call

StreamingState

Current streaming state

Traits

BamlClass

Helper trait for decoding BAML classes

BamlDecode

Trait for decoding from CFFI protobuf format (BAML -> Rust)

BamlEncode

Trait for encoding to CFFI protobuf format (Rust -> BAML)

BamlEnum

Helper trait for decoding BAML enums

BamlSerializeMapKey

FromBamlValue

Trait for extracting concrete types from BamlValue.

FromBamlValueRef

Trait for zero-copy borrowing from BamlValue.

KnownTypes

Trait for project-specific known types enum. Implemented by CodeGen’d Types and StreamTypes enums.

Functions

decode_enum

Decode an enum from a CffiValueHolder

decode_field

Helper for decoding a field from a class’s fields map

encode_class

Encode a class to HostValue

encode_class_dynamic

Encode a class with dynamic field names (for dynamic classes that flatten __dynamic fields)

encode_enum

Encode an enum to HostValue

invoke_cli

Call baml-cli with the given arguments Returns the exit code

version

Get the BAML library version

Type Aliases

StaticRuntimeType

Derive Macros

BamlDecode

Derive macro for BamlDecode trait.

BamlEncode

Derive macro for BamlEncode trait.