Fix multipart limit violations being silently swallowed

[Chaoran-Huang]

Type of change

• Bug fix

Description

Fixes #6392.

Multipart.makeChannel (packages/effect/src/unstable/http/Multipart.ts) stores the parser's failure and its end-of-parse signal in the same exit slot. multipasta keeps running after it signals a limit/parse error and always calls onDone at the end, and the terminal onDone handler unconditionally overwrote a previously captured failure with the completion sentinel:

onError(error_) {
  exit = Option.some(Exit.fail(convertError(error_)))
},
onDone() {
  exit = Option.some(Exit.fail(Cause.Done())) // clobbers a captured failure
}

The consuming loop only inspects exit once partsBuffer is drained — which happens after the pump pull that calls parser.end() (→ onDone). Whenever the violation and end-of-input are reached in the same delivery — always the case when the body arrives in a single chunk, i.e. essentially every small upload — the captured MultipartError is overwritten by Cause.Done() and the stream completes normally. In practice this means maxParts, maxFileSize, and maxFieldSize are silently not enforced (maxTotalSize still trips because the body stream's MaxBodySize aborts it independently, before onDone).

Fix

onDone now records normal completion only when no failure was already captured:

onDone() {
  if (Option.isNone(exit)) {
    exit = Option.some(Exit.fail(Cause.Done()))
  }
}

onDone is multipasta's terminal callback (fires once, after any onError), so first-signal-wins is the correct precedence.

Test

Adds a regression test that feeds a 3-part body as a single chunk under maxParts: 2 and asserts the stream fails with TooManyParts. Verified it fails before the fix (the stream wrongly completes) and passes after — the two pre-existing Multipart tests remain green (vitest run test/unstable/http/Multipart.test.ts: 3 passed).

Note on affected versions

Reported against the published @effect/platform (0.94.5 and 0.97.0), where the same clobber uses Exit.void; on main the module has moved to effect/unstable/http and the sentinel is Cause.Done(), but the bug and fix are identical. Maintainers may want to backport to the @effect/platform line.

🤖 Generated with Claude Code

[changeset-bot]

🦋 Changeset detected

Latest commit: 1e09df5

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 27 packages

Name	Type
effect	Patch
@effect/opentelemetry	Patch
@effect/platform-browser	Patch
@effect/platform-bun	Patch
@effect/platform-node-shared	Patch
@effect/platform-node	Patch
@effect/vitest	Patch
@effect/ai-anthropic	Patch
@effect/ai-openai-compat	Patch
@effect/ai-openai	Patch
@effect/ai-openrouter	Patch
@effect/atom-react	Patch
@effect/atom-solid	Patch
@effect/atom-vue	Patch
@effect/sql-clickhouse	Patch
@effect/sql-d1	Patch
@effect/sql-libsql	Patch
@effect/sql-mssql	Patch
@effect/sql-mysql2	Patch
@effect/sql-pg	Patch
@effect/sql-pglite	Patch
@effect/sql-sqlite-bun	Patch
@effect/sql-sqlite-do	Patch
@effect/sql-sqlite-node	Patch
@effect/sql-sqlite-react-native	Patch
@effect/sql-sqlite-wasm	Patch
@effect/openapi-generator	Patch

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