[dinasaur404]

Errors whose type capnweb can't reconstruct (anything other than the built-in error classes) arrive as plain Error with name: "Error". Own properties like code already survive, but the original name is lost. workerd keeps the name when it passes these errors between Workers, so capnweb behaves differently from the platform it runs alongside.

This shows up in Wrangler's remote bindings, which use capnweb between the local and remote proxy workers. A Cloudflare Artifacts binding throws ArtifactsError in production, but in wrangler dev with remote: true the error arrives as Error.

Change

When the receiver falls back to Error for an unknown type, set name to the sender's value as a non-enumerable own property. The object is still a real Error with Error.prototype, so instanceof checks and type safety don't change.

Names that resolve to Object.prototype members (for example constructor or __proto__) still become Error, so the existing type-confusion guarantees and test still hold.

Testing

• New test: a custom ArtifactsError subclass with code and numericCode round-trips with its name, stays instanceof Error with Error.prototype, keeps name out of Object.keys, and String(error) gives "ArtifactsError: …". It fails without the change.
• node project: 422 passed. workerd project: 225 passed. The browser projects weren't run locally because Playwright browsers aren't installed.
• tsc --noEmit reports the same 44 errors as main, none new.
• End to end: bundled this build into Wrangler's remote-bindings proxy alongside [miniflare] Preserve binding error codes in local development workers-sdk#16499 and called a production Artifacts binding with remote: true. Errors came back as { name: "ArtifactsError", code: "NOT_FOUND", numericCode: 10200 }, identical to production.

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🦋 Changeset detected

Latest commit: 87517dd

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

This PR includes changesets to release 1 package

Name	Type
capnweb	Patch

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commit: 87517dd

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