Problem

Proving fails with ClientError: Failed to prove transaction whenever the npm undici package (>= 8.2.0) is present in the process — e.g. in any test importing testcontainers or @effect/platform-node. Both "should prove a valid transaction" tests in httpProverClient.test.ts fail. This is the same regression that previously forced pinning undici back to 8.1.0 (d9531ec); the combined dependency updates re-introduce it by moving the pin to 8.4.x.

Root cause

Two things conspire:

1. npm undici 8 hijacks global fetch on import. Its lib/global.js installs its own Agent as the global dispatcher at module load, including under the legacy Symbol.for('undici.globalDispatcher.1') slot that Node 22's bundled fetch (undici 6.24.1) reads. Merely importing testcontainers reroutes every fetch() in the process through npm undici 8 via a Dispatcher1Wrapper.
2. undici 8.2.0 added strict content-length validation (fix: reject malformed content-length request headers nodejs/undici#5060, "reject malformed content-length request headers" — value must be a digit-only string). HttpClientRequest.bodyUint8Array from @effect/platform sets an explicit content-length header; Node's bundled fetch also computes one from the body, and the duplicated value arriving at undici 8's validator fails the check with InvalidArgumentError: invalid content-length header.

Verified in isolation: the same fetch POST with an explicit content-length header succeeds before import 'undici' and fails with invalid content-length header after it; without the explicit header it succeeds in both cases.

Fix

Build the proof-server request body with HttpBody.raw(body, { contentType: 'application/octet-stream' }) instead of bodyUint8Array, so no explicit content-length header is attached and fetch derives it from the body. This also matches the fetch spec, where Content-Length is a forbidden request header (browsers strip it silently anyway), and decouples the prover client from whichever undici version owns the global dispatcher.

This is the only place in the SDK that sends a request body through FetchHttpClient, so no other call sites are affected.

Testing

• yarn test --filter=@midnight-ntwrk/wallet-sdk-prover-client --force: 11/11 pass (2 failed before the fix)
• yarn turbo typecheck lint --filter=@midnight-ntwrk/wallet-sdk-prover-client: clean
• Effect language-service diagnostics on the changed file: clean