[shivros]

Summary

• Track TypeScript JSON Schema expression precedence instead of flattening nested unions/intersections as strings.
• Parenthesize lower-precedence union operands when they are rendered inside intersections, while preserving existing scalar, nullable, array, object, and deterministic output behavior.
• Add a real nested-schema fixture with strict TypeScript assignments, baseline evidence, two-write byte comparison, hydra check, and CI invocation.

Linear

COD-521 — Hydra: preserve nested JSON Schema union/intersection grouping in TypeScript.

Baseline evidence

The pre-fix fixture was generated from Hydra origin/main at b210ff55147dbf5667b2c098c833a94a96126fba and compiled with the pinned TypeScript 5.9.2 toolchain. The compiler exited 2 with four TS2578: Unused '@ts-expect-error' directive failures at type-tests.ts lines 21, 24, 26, and 29, proving the ungrouped renderer accepted invalid values. The reproducible record is committed at crates/hydra-codegen/tests/fixtures/nested-ts-schema/baseline.md.

Verification

• cargo build --all-targets
• cargo test --all-targets — 59 codegen tests plus Notes/Security Scan suites passed
• cargo clippy --all-targets -- -D warnings
• cargo fmt --all -- --check
• cargo run -p hydra-codegen --bin hydra-codegen -- check in examples/notes, examples/security-scan, and examples/ts-client
• npm run test:nested-schema — two writes byte-identical across CLI/HTTP/MCP/TypeScript, hydra check passed, strict TypeScript 5.9.2 positive/negative assignments passed
• npm run typecheck
• npm run build
• creed diff
• git diff --check
• cargo metadata --locked --no-deps --format-version 1

No consumer repin, release/tag, npm publication, deployment, credential, or runtime transport behavior is included.

[shivros]

🤖 Automated Review Panel

Reviewer A

APPROVE

• The precedence-aware TsTypeExpression model correctly ranks unions below intersections and parenthesizes lower-precedence operands inside & expressions.
• The generated-output assertions cover anyOf, oneOf, enum, nested intersections, and array/object nesting.
• The strict TypeScript fixture covers valid assignments and rejects out-of-domain intersection and union values. The committed baseline.md records the pre-fix b210ff5 compiler failure with the four unused @ts-expect-error diagnostics.
• The fixture checks two byte-identical writes across all four artifacts and runs hydra check; no unrelated runtime or transport behavior was introduced.

No remaining correctness or acceptance blockers found.

Reviewer B

APPROVE

• The renderer preserves TypeScript operator precedence and produces the required ("a" | "b") & "b" grouping for the target schema.
• Recursive handling remains correct for oneOf, anyOf, allOf, enum, nullable types, arrays, and objects, with deterministic ordering preserved.
• The checked-in fixture validates the generated result with TypeScript 5.9.2, and the two-write determinism plus freshness checks provide reproducible evidence.
• The change stays bounded to Hydra code generation and CI evidence; it does not add runtime transport behavior, consumer adoption, or release work.

No blocking findings.

[shivros]

Auto-Merge Gate

Confidence: 0.95

The implementation directly satisfies COD-521: it replaces precedence-blind TypeScript schema rendering with an explicit precedence model and adds real generated-output, strict TypeScript, determinism, and CI coverage for the reported nested union/intersection bug.

Checks observed: CI Test and Creed context drift succeeded. The PR's review panel found no remaining blockers. The linked Linear issue contains no manual-review or do-not-merge requirement, and this change excludes releases, deployment, credentials, and consumer adoption.

Scope reviewed: Hydra code-generation correctness plus focused fixtures and CI invocation only.