feat(http): add tracer header filter combinators to HttpClient

[Zelys-DFKH]

Opening this at @IMax153's request to replace Effect-TS/effect-smol#2132. Now that V4 development has merged back into this repo's main branch, the linked issue lives here as #6363, so I'm bringing the same change over.

What this adds

Three new HttpClient combinators for controlling which headers get captured as OTEL span attributes:

• withTracerRequestHeadersFilter: filters which request headers are captured
• withTracerResponseHeadersFilter: filters which response headers are captured
• withTracerHeadersFilter: applies the same predicate to both

Each takes a Predicate.Predicate<string> that receives the header name (already lower-cased) and returns true to capture it. The default is constTrue, so every header is captured just like today. This is fully backward compatible.

Why

HttpClient currently captures every header value as a span attribute unconditionally. For chatty APIs (Notion, Cloudflare-fronted services, CloudFront, etc.) that means 15-30+ low-signal attributes per span (cf-ray, alt-svc, via, and the like), which bloats trace storage and buries the few attributes that actually matter for debugging. Headers.CurrentRedactedNames only redacts values; the attributes are still emitted regardless. This gives callers a way to opt individual headers out entirely, matching the header-capture allowlist knobs already common in other OTEL client instrumentations (Java's OTEL_INSTRUMENTATION_HTTP_CLIENT_CAPTURE_REQUEST_HEADERS, for example).

Testing

Adds four tests to HttpClient.test.ts (a default-capture-all baseline plus one per combinator) and a tstyche typetest block that verifies data-first/data-last usage across all three combinators.

Credit

Thanks to @schickling for the well-researched issue #6363, the reproduction repo made this easy to verify, and to @IMax153 for the review on the original Effect-TS/effect-smol#2132.

Fixes #6363

[changeset-bot]

🦋 Changeset detected

Latest commit: a71991d

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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