Add first-class C# SDK generation and runtime support

[rossirpaulo]

Summary

• add deterministic C# SDK generation and a managed CFFI runtime
• support streaming, media, host callables, request clients, optional/nullable values, unions, dynamic values, and structural resources
• add C# fixtures, ABI/protocol/package probes, NuGet packaging, release integration, and dedicated CI
• keep generated fixture clients untracked and isolate C# verification/publishing from generic native bridge workflows

Canary rebase and boundary

• rebuilt as one focused commit on Canary 4aad907cc0c421c5275837cb02f46cae05c87db7
• removed the previous baml_std host-boundary annotations and AST/shared compiler-semantic changes
• adapted C# generation and resource ownership to existing Canary semantics
• limited shared changes to cross-language correctness fixes and narrowly scoped, append-only CFFI/protocol extensions required by typed host values and race-safe host-call completion
• generated Python/Rust protocol files are canonical schema fallout; existing Rust collection encoding retains its legacy optional-metadata behavior

Shared correctness fixes

• preserve exact union/literal and realized collection occurrence metadata
• allow retained host-callable handles to be invoked through the VM callable entry point
• preserve array/map descriptors during heap copies and correctly reclaim host-owned arguments
• reject non-null payloads for void callback returns
• claim callback completion before decoding transferred handles so cancellation races cannot leak or double-own resources

Validation

• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets --all-features -- -D warnings
• cargo nextest run -p sdk_test_csharp — 15/15
• cargo test -p sdkgen_csharp — 47/47
• cargo test -p baml_bridge — 62/62 across unit, conversion, and live suites
• cargo test -p bridge_cffi
• cargo test -p bridge_ctypes -p bex_heap -p bex_external_types
• focused cross-language occurrence and retained-host-callable tests
• managed bridge, host-callable, and protocol probes

[vercel]

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Project	Deployment	Actions	Updated (UTC)
beps	Ready	Preview, Comment	Jul 22, 2026 7:45pm
promptfiddle	Ready	Preview, Comment	Jul 22, 2026 7:45pm
promptfiddle2	Error		Jul 22, 2026 7:45pm

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch paulo/csharp-bridge

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[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.

[blacksmith-sh]

Found 2 test failures on Blacksmith runners:

Failures

Test	View Logs
roundtrip_tests.TestForwardRefs/test_round_trip_rec_list()	View Logs
TestHostCallables/test_concurrent_throws_in_flight_rehydrate_to_their_own_object()	View Logs

[github-actions]

Binary size checks failed

❌ 3 violations · ✅ 4 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	🔒 26.2 MB	11.1 MB	file	25.3 MB	+911.2 KB (+3.6%)	FAIL
✅	packed-program	Linux	🔒 17.2 MB	7.1 MB	file	17.0 MB	+165.4 KB (+1.0%)	OK
❌	baml-cli	macOS	🔒 20.3 MB	9.7 MB	file	19.6 MB	+728.0 KB (+3.7%)	FAIL
✅	packed-program	macOS	🔒 13.4 MB	6.2 MB	file	13.2 MB	+198.3 KB (+1.5%)	OK
❌	baml-cli	Windows	🔒 21.9 MB	9.9 MB	file	21.1 MB	+808.4 KB (+3.8%)	FAIL
✅	packed-program	Windows	🔒 14.3 MB	6.3 MB	file	14.2 MB	+161.3 KB (+1.1%)	OK
✅	bridge_wasm	WASM	16.3 MB	🔒 4.4 MB	gzip	4.4 MB	+30.4 KB (+0.7%)	OK

🔒 = 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:

• baml-cli (Linux) file_bytes: 26.2 MB exceeds limit of 26.0 MB (exceeded by +152.7 KB, policy: max_file_bytes)
• baml-cli (Linux) file_delta_pct: +3.6% exceeds limit of 3.0% (exceeded by +0.6pp, policy: max_delta_pct)
• baml-cli (macOS) file_bytes: 20.3 MB exceeds limit of 20.2 MB (exceeded by +140.6 KB, policy: max_file_bytes)
• baml-cli (macOS) file_delta_pct: +3.7% exceeds limit of 3.0% (exceeded by +0.7pp, policy: max_delta_pct)
• baml-cli (Windows) file_bytes: 21.9 MB exceeds limit of 21.7 MB (exceeded by +175.3 KB, policy: max_file_bytes)
• baml-cli (Windows) file_delta_pct: +3.8% exceeds limit of 3.0% (exceeded by +0.8pp, policy: max_delta_pct)

Add/update baselines:

.ci/size-gate/aarch64-apple-darwin.toml:

[artifacts.baml-cli]
file_bytes = 20306304
stripped_bytes = 20306336
gzip_bytes = 9691188

.ci/size-gate/x86_64-pc-windows-msvc.toml:

[artifacts.baml-cli]
file_bytes = 21914624
stripped_bytes = 21914624
gzip_bytes = 9918776

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

[artifacts.baml-cli]
file_bytes = 26196496
stripped_bytes = 26196488
gzip_bytes = 11120413

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Generated by cargo size-gate · workflow run