The builder's .input() did not typecheck as written (TS2345). The phantom
__input/__output markers make ProcedureDef invariant, which is exactly why
.output<T>() already carried a cast - .input() needed the analogous one and
did not have it.
Caught by the Task 3 implementer, who also verified via @ts-expect-error that
InferProcedureInput/InferProcedureOutput genuinely reject wrong shapes, so
the phantom markers are carrying real type information rather than silently
widening.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
ClintchizandClaude Opus 5
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