fix(ci): replace tsc --build with tsc --composite false to prevent race condition

[davidkonigsberg]

Description

Refs: Failed CI job — intermittent @fern-api/ir-utils:compile failure with:

'"@fern-api/ir-sdk"' has no exported member named 'ExampleInlinedRequestBodyProperty'.
Did you mean 'ExampleInlinedRequestBodyExtraProperty'?

The type exists in ir-sdk source and the error disappears on re-run.

Requested by: @davidkonigsberg
Link to Devin run: https://app.devin.ai/sessions/c176a6d6126b4616b03415f9af267f95

Root Cause Analysis

When turbo runs compile tasks, it respects dependsOn: ["^compile"] for ordering but runs sibling tasks concurrently. Each package's tsc --build follows project references in tsconfig.json and checks whether referenced projects need rebuilding. 25+ packages reference ir-sdk. If any concurrent tsc --build process decides ir-sdk is stale and starts rewriting its lib/ output, other concurrent processes reading from ir-sdk/lib/ can see incomplete declarations.

Changes Made

• compile: tsc --build → tsc --composite false (174 packages)
• compile:debug: tsc --build --sourceMap → tsc --composite false --sourceMap (171 packages)
• clean: tsc --build --clean → rm -f tsconfig.tsbuildinfo (175 packages)

tsc --composite false overrides the composite: true from tsconfig.json, causing tsc to compile only the current package without following project references. Turbo still handles build ordering via dependsOn: ["^compile"].

⚠️ Human Review Checklist

This is a large mechanical change. Please scrutinize the approach, not just the diff.

• Is the root cause correct? The race condition theory is plausible but was not definitively proven — only inferred from log timing analysis and the fact that tsc --build follows references. The flake could have other causes (infra, turbo bug, etc.).
• Is tsc --composite false the right pattern? This is an uncommon approach. It disables composite at the CLI level while tsconfig.json still says composite: true. This means: (a) no .tsbuildinfo files → no incremental compilation, (b) references in tsconfig become dead config, (c) IDE behavior may diverge from build behavior.
• Impact on local dev? Every pnpm run compile in a package will now do a full recompile (no incremental builds). Turbo cache helps in CI but not for local iterative development.
• Are there packages that rely on .tsbuildinfo for other tools? The clean script now does rm -f tsconfig.tsbuildinfo but tsc --composite false doesn't generate it anyway.
• Module resolution edge cases? With tsc --build, TypeScript uses project references for resolution. With tsc --composite false, it uses normal node_modules resolution. Tested on ir-sdk and ir-utils but not all 175 packages.

Testing

• Local test: ir-sdk and ir-utils compile successfully with tsc --composite false
• Local test: turbo run compile --filter=@fern-api/ir-utils (7 packages) passes
• Full monorepo compile (will be tested in CI)
• Seed tests (will be tested in CI)

Alternative Approaches Considered

1. Use tsc without --composite false: Doesn't work — tsc respects composite: true in tsconfig and requires --build flag.
2. Remove composite: true from all tsconfig.json files: More invasive; affects IDE behavior and requires updating 175+ tsconfig files.
3. Serialize compilation with turbo concurrency limits: Would significantly slow down CI.
4. Fix the actual race in tsc --build: Not feasible — this is TypeScript compiler behavior.

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✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 3 additional findings.