Release22 days ago3 min read

BAML 0.17.0

Runtime reflection, native BAML model clients, cryptography and filesystem APIs, toolchain pinning, and a rewritten type checker.

Features

Added runtime reflection and type construction, including compiling and mounting packages, invoking reflected callables, and isolating dynamic work in sessions. (#4325) - Antonio Sarosi
Added native BAML clients for OpenAI, Anthropic, Google, Vertex AI, AWS Bedrock, Azure, Ollama, OpenRouter, and Vercel AI Gateway, including typed streaming, media outputs, AWS SigV4, and Google Cloud authentication. (#4430) - aaronvg
Added baml.sys.pid(), baml.fs.chmod(), and baml.fs.symlink(). (#4427) - 2kai2kai2
Added baml.crypto.* APIs for SHA-256 hashing, authenticated encryption, and key generation. (#4431) - 2kai2kai2
Added baml toolchain pin <canary|nightly|version|path> to select a project-local toolchain in the nearest baml.toml (#4386) - Sam Lijin
Added arithmetic across baml.time values (#4366) - 2kai2kai2
Added assert.is_type<T>(value) and improved assertion failure formatting (#4388) - 2kai2kai2
Added integer and bigint bitwise operators (&, |, ^, <<, and >>), including mixed int/bigint widening, and added generic baml.ops.Index support for arrays, string-keyed maps, and uint8array. (#4301) - Avery Townsend
Enabled advertised LSP code-action support so spec-compliant editors can request BAML code actions, including “Open in Playground.” (#3358) - Miguel F. Serna

Breaking and compatibility changes

Renamed openai.OpenAiClient to openai.ResponsesClient. (#4430) - aaronvg
Improved the string stdlib APIs: renamed String.char_at to String.at, kept negative indexing, and made out-of-range access return null; made String.code_point_at return null out of range; removed String.matches in favor of String.includes; renamed String.substring to String.slice; and added String.last_index_of. (#4433) - 2kai2kai2
Drop support for Jinja templates: BAML now has TS-style template literals that are much easier to use. (#4367) - Avery Townsend
LLM function fields now require colon-delimited client:, prompt:, and tools: syntax. (#4317) - Vaibhav Mittal
Rewrote the type checker to enable more powerful type inference (#4301) - Avery Townsend

Fixes

Enabled runtime package compilation from baml run scripts and expressions. (#4451) - Antonio Sarosi
Supported double-quoted LLM prompts as literal, non-interpolating prompts and fixed the segfault they could cause. (#4432) - 2kai2kai2
Made Array.join stringify non-string elements instead of silently replacing them with empty strings. (#4433) - 2kai2kai2
Fixed null-coalescing assignments, property shorthand scope, runtime type tests, and media kind validation. (#4434) - Avery Townsend
Fixed Windows path, URI, and VFS handling. (#4103) - jubjub727
Fixed method dispatch through optional interface receivers. (#4435) - Avery Townsend
Preserved authored escapes, leading and trailing whitespace, blank lines, and relative indentation in backtick strings by dedenting raw source before escape decoding. In particular, a trailing \n is no longer silently removed. (#4365) - hellovai
Improved B1129 diagnostics for invalid postfix ! syntax so the suggested optional-unwrapping alternatives are valid BAML. (#4383) - 2kai2kai2
Stopped the LSP server from advertising textDocumentSync.willSave, which it accepts only as a no-op, while retaining full-document synchronization and didSave. (#3366) - Miguel F. Serna
Restored cross-namespace LLM calls in playground workflow graphs by resolving relative call paths to canonical package-qualified names before graph expansion. (#4246) - Sam Lijin
Made baml run -e evaluate standard-library-only expressions even when unrelated project files do not compile, while preserving project-context fallback for expressions that reference project declarations. (#4401) - Sam Lijin
Made //# header comments parse consistently: they are preserved in expression functions, executable blocks, match arms, and catch arms, and rejected elsewhere with a targeted diagnostic instead of causing cascading parser failures. (#4406) - Sam Lijin
Corrected the no-project CLI diagnostic to recommend the supported baml test --project <DIR> option instead of the nonexistent --file option. (#4410) - Sam Lijin
Prevented required interface methods from being treated as callable default bodies. (#4301) - Avery Townsend
Make Array.sort_by and Array.sort_by_key a stable O(n log n) merge sort. (#4382) - Sam Lijin
Restored and improved compiler and VM performance after BEP-066, reducing overhead in package inference, calls, arrays, interface dispatch, and string operations. (#4448; #4450) - Antonio Sarosi

Features

Added runtime reflection and type construction, including compiling and mounting packages, invoking reflected callables, and isolating dynamic work in sessions. (#4325) - Antonio Sarosi

Added native BAML clients for OpenAI, Anthropic, Google, Vertex AI, AWS Bedrock, Azure, Ollama, OpenRouter, and Vercel AI Gateway, including typed streaming, media outputs, AWS SigV4, and Google Cloud authentication. (#4430) - aaronvg

Added baml.sys.pid(), baml.fs.chmod(), and baml.fs.symlink(). (#4427) - 2kai2kai2

Added baml.crypto.* APIs for SHA-256 hashing, authenticated encryption, and key generation. (#4431) - 2kai2kai2

Added baml toolchain pin <canary|nightly|version|path> to select a project-local toolchain in the nearest baml.toml (#4386) - Sam Lijin

Added arithmetic across baml.time values (#4366) - 2kai2kai2

Added assert.is_type<T>(value) and improved assertion failure formatting (#4388) - 2kai2kai2

Added integer and bigint bitwise operators (&, |, ^, <<, and >>), including mixed int/bigint widening, and added generic baml.ops.Index support for arrays, string-keyed maps, and uint8array. (#4301) - Avery Townsend

Enabled advertised LSP code-action support so spec-compliant editors can request BAML code actions, including “Open in Playground.” (#3358) - Miguel F. Serna

Breaking and compatibility changes

Renamed openai.OpenAiClient to openai.ResponsesClient. (#4430) - aaronvg

Improved the string stdlib APIs: renamed String.char_at to String.at, kept negative indexing, and made out-of-range access return null; made String.code_point_at return null out of range; removed String.matches in favor of String.includes; renamed String.substring to String.slice; and added String.last_index_of. (#4433) - 2kai2kai2

Drop support for Jinja templates: BAML now has TS-style template literals that are much easier to use. (#4367) - Avery Townsend

LLM function fields now require colon-delimited client:, prompt:, and tools: syntax. (#4317) - Vaibhav Mittal

Rewrote the type checker to enable more powerful type inference (#4301) - Avery Townsend

Fixes

Enabled runtime package compilation from baml run scripts and expressions. (#4451) - Antonio Sarosi

Supported double-quoted LLM prompts as literal, non-interpolating prompts and fixed the segfault they could cause. (#4432) - 2kai2kai2

Made Array.join stringify non-string elements instead of silently replacing them with empty strings. (#4433) - 2kai2kai2

Fixed null-coalescing assignments, property shorthand scope, runtime type tests, and media kind validation. (#4434) - Avery Townsend

Fixed Windows path, URI, and VFS handling. (#4103) - jubjub727

Fixed method dispatch through optional interface receivers. (#4435) - Avery Townsend

Preserved authored escapes, leading and trailing whitespace, blank lines, and relative indentation in backtick strings by dedenting raw source before escape decoding. In particular, a trailing \n is no longer silently removed. (#4365) - hellovai

Improved B1129 diagnostics for invalid postfix ! syntax so the suggested optional-unwrapping alternatives are valid BAML. (#4383) - 2kai2kai2

Stopped the LSP server from advertising textDocumentSync.willSave, which it accepts only as a no-op, while retaining full-document synchronization and didSave. (#3366) - Miguel F. Serna

Restored cross-namespace LLM calls in playground workflow graphs by resolving relative call paths to canonical package-qualified names before graph expansion. (#4246) - Sam Lijin

Made baml run -e evaluate standard-library-only expressions even when unrelated project files do not compile, while preserving project-context fallback for expressions that reference project declarations. (#4401) - Sam Lijin

Made //# header comments parse consistently: they are preserved in expression functions, executable blocks, match arms, and catch arms, and rejected elsewhere with a targeted diagnostic instead of causing cascading parser failures. (#4406) - Sam Lijin

Corrected the no-project CLI diagnostic to recommend the supported baml test --project <DIR> option instead of the nonexistent --file option. (#4410) - Sam Lijin

Prevented required interface methods from being treated as callable default bodies. (#4301) - Avery Townsend

Make Array.sort_by and Array.sort_by_key a stable O(n log n) merge sort. (#4382) - Sam Lijin

Restored and improved compiler and VM performance after BEP-066, reducing overhead in package inference, calls, arrays, interface dispatch, and string operations. (#4448; #4450) - Antonio Sarosi