[sxlijin]

Final shrinking pass for baml_sdk LoC by only generating stdlib types if they are reachable from the user's code

• Roots:
  • every generated function and every user type;
  • the always-kept namespaces:
    • baml.media (Image, Audio, Video, Pdf), which are bridge-owned classes;
    • baml.errors, baml.panics, ai.errors and ai.stream. The runtime hands the host error, panic and stream-event values (for example ai.stream.Done) that no signature names, and decoding them needs these typemap entries.
• Edges: class properties and methods; function arguments, return types, throws and watchers; alias targets, including through generics, unions, maps, callables and futures. A type token (Ty::Type) reaches the bridge-owned reflect.Type.

The PR also keeps pruned namespaces importable:

• The Python baml package always re-exports BamlError, BamlPanic and UNSET.
• An otherwise empty TypeScript index.ts gets export {};, because tsc rejects imports from an empty script.

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developer-docs	Ready	Preview	Sep 28, 2026 5:45pm UTC

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Advanced

Run ID: ddd8e137-0c83-49f6-a276-31479fa5f1d2

📥 Commits

Reviewing files that changed from the base of the PR and between 88fa664 and e7977aa.

📒 Files selected for processing (2)

• baml_language/sdks/python/rust/sdkgen_python_pydantic2/src/lib.rs
• baml_language/sdks/typescript/sdkgen_typescript_shared/src/lib.rs

Included review availability: This review used your included allowance. Your plan provides up to 10 included reviews per hour; 8 remain after this review.

---

📝 Walkthrough

Walkthrough

SDK generation now removes unreachable built-in types while retaining types reached through declarations. Python runtime and stub output share bridge re-exports for the baml leaf, including when it is empty. TypeScript output adds export {}; when a generated namespace has no declarations.

Changes

SDK built-in filtering and output

Layer / File(s)	Summary
Built-in type reachability baml_language/crates/baml_sdkgen_types/src/lib.rs, baml_language/crates/baml_sdkgen_types/src/reachable.rs	Adds and exports symbol-pool filtering for built-in types. The traversal follows declaration type references and retains built-ins in specified namespaces. Tests cover reachable types, cycles, and retained namespaces.
Python SDK filtering and package re-exports baml_language/sdks/python/rust/sdkgen_python_pydantic2/src/lib.rs, baml_language/sdks/python/rust/sdkgen_python_pydantic2/src/leaf.rs	Python generation filters unreachable built-in types. Runtime and stub rendering share root re-export handling, including for empty leaves. Tests check retained types and error-wrapper re-exports.
TypeScript SDK filtering and empty modules baml_language/sdks/typescript/sdkgen_typescript_shared/src/lib.rs	TypeScript generation filters unreachable built-in types and adds export {}; when a generated namespace has no declarations. Tests check reachable types and empty output.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Feature

Suggested reviewers: aaronvg

Merge Risk: ⚪ Minimal · up to e7977

No identified issue blocks merging after normal checks.

Architecture Summary

Architecture risk: 🔵 Low · up to e7977

The change affects 1 system.

Changed systems: baml_language

Architecture concerns
No architecture-level concerns identified.

Review details

Systems and components

• observed — baml_language (service) was modified; 5 changed files map to changed impact.

Before / after behavior

• observed — Modified behavior in baml_language/crates/baml_sdkgen_types/src/lib.rs: Declares the private reachable module.
• observed — Modified behavior in baml_language/crates/baml_sdkgen_types/src/lib.rs: Re-exports reachable::without_unreachable_builtin_types publicly.
• observed — Modified behavior in baml_language/sdks/python/rust/sdkgen_python_pydantic2/src/leaf.rs: Added BAML_ROOT_REEXPORTS and baml_root_reexports, which return the bridge re-export import for the baml leaf and an empty string for other leaves. Empty runtime leaf bodies now return that re-export when applicable instead of always returning an empty string.
• observed — Modified behavior in baml_language/sdks/python/rust/sdkgen_python_pydantic2/src/leaf.rs: Runtime rendering now appends the shared helper’s re-export text instead of performing an inline leaf check and constructing the import there.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 41.38% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 29 functions across 5 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: generating only reachable standard-library types in the Python and TypeScript SDKs. The breaking-change marker is appropriate because the pul…

✨ Finishing Touches 💡 2

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• Create a new PR

🛠️ Fix failing CI checks 💡

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• Create a new PR

🧪 Generate unit tests (beta)

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---

_{A rabbit checks the types in rows,
Keeps each path that reachability shows.
The unused names hop out of sight,
While root-leaf imports stay in flight.
Empty modules still stand upright,
Then carrots mark the build complete.}

_{Comment @coderabbitai help to get the list of available commands.}

[github-actions]

⏭️ Performance benchmarks were skipped

Perf benchmarks (CodSpeed) are opt-in on pull requests — they no longer run on every push. They always run automatically after merge to canary/main.

To run them on this PR, do any of the following, then push a commit (or re-run CI):

• Add RUN_CODSPEED=1 to the PR description, or
• Include run-perf or /perf in the PR title or any commit message.

[github-actions]

Binary size checks failed

❌ 2 violations · ✅ 1 passed

⚠️ Please fix the size gate issues or acknowledge them by updating baselines.

	Artifact	Platform	File	Gzip	Gated on	Baseline	Delta	Status
✅	baml-cli	Linux	🔒 61.1 MB	25.4 MB	file	73.1 MB	-11.9 MB (-16.3%)	OK
❌	packed-program	Linux	🔒 40.1 MB	15.9 MB	file	28.9 MB	+11.2 MB (+38.7%)	FAIL
❌	bridge_wasm	WASM	28.2 MB	🔒 7.8 MB	gzip	5.8 MB	+2.1 MB (+35.8%)	FAIL

🔒 = the size this artifact is GATED on (ceiling + delta). Binaries gate on file size (installed binary); WASM gates on gzip (download size). The other size is shown for information only.

Details & how to fix

Violations:

• packed-program (Linux) file_bytes: 40.1 MB exceeds limit of 29.8 MB (exceeded by +10.4 MB, policy: max_file_bytes)
• packed-program (Linux) file_delta_pct: +38.7% exceeds limit of 3.0% (exceeded by +35.7pp, policy: max_delta_pct)
• bridge_wasm (WASM) gzip_bytes: 7.8 MB exceeds limit of 5.9 MB (exceeded by +2.0 MB, policy: max_gzip_bytes)
• bridge_wasm (WASM) gzip_delta_pct: +35.8% exceeds limit of 3.0% (exceeded by +32.8pp, policy: max_delta_pct)

Add/update baselines:

.ci/size-gate/wasm32-unknown-unknown.toml:

[artifacts.bridge_wasm]
file_bytes = 28221460
gzip_bytes = 7834305

.ci/size-gate/x86_64-unknown-linux-gnu.toml:

[artifacts.packed-program]
file_bytes = 40142856
gzip_bytes = 15871097

---

Generated by cargo size-gate · workflow run

[chatgpt-codex-connector]

Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-26T23:39:02.106687Z	c7d3618	Draft marked ready

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[chatgpt-codex-connector]

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Reviewed commit: c7d3618b96

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[chatgpt-codex-connector]

Preserve types that can escape through unknown

When a generated function exposes unknown, a value of any built-in class can cross the SDK boundary even though its static signature contains no named reference—for example, function f() -> unknown { baml.time.Duration.from_seconds(1) }. This traversal treats Ty::Unknown as having no reachability edges, so baml.time.Duration is removed from the generated typemap; Python then fails in _decode_class with Unknown class FQN, while TypeScript silently returns a plain object instead of the generated instance. Detecting an exposed unknown needs to conservatively retain possible built-in runtime values (or otherwise provide a decoder fallback that preserves them).

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[blacksmith-sh]

Found 1 test failure on Blacksmith runners:

Failure

Test	View Logs
bex_engine/ telemetry::failure_tests::disk_error_with_full_file_queue_and_chunk_pool_does_not_fail_ application	View Logs

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