[dinasaur404]

Errors from Artifacts (and other bindings) lose code and numericCode in local development. Developers can only branch on message text, so code that works in production can fail locally.

What was broken

Comparison for the same calls (get() on a missing repo, invalid name, list({ limit: 0 })):

Path	Before	After
Production (Worker on Cloudflare)	name: "ArtifactsError", code: "NOT_FOUND", numericCode: 10200	unchanged
wrangler dev with remote: true, inside the Worker	name: "Error", message: "ArtifactsError: Repository not found…", no code	code and numericCode kept, clean message, name: "Error"
getPlatformProxy() with remote: true	same as above	code and numericCode kept, clean message
Miniflare#getBindings() with a local binding	same as above	identical to production, including name: "ArtifactsError"

Why

Three internal workers pass errors between Workers. They use compatibility dates from before workerd's enhanced_error_serialization behavior, so they keep only the message text and fold the name into it:

• the remote-bindings proxy server (packages/remote-bindings/src/start-remote-proxy-session.ts)
• the remote-proxy client (packages/miniflare/src/plugins/shared/constants.ts)
• the entry worker that hosts ProxyServer for Node callers (packages/miniflare/src/plugins/core/index.ts)

Miniflare already enables this flag for local D1 for the same reason.

Separately, the devalue Error reducer used by the Node proxy (packages/miniflare/src/workers/core/devalue.ts) sent only name, message, stack and cause. It now also sends own properties with primitive values (string, number, boolean or null) and a custom error name. It skips non-primitive values so they can't make an error unserialisable. Errors without extra properties keep the old encoding.

Known limitation

Inside a Worker, remote-binding errors are still named Error. capnweb rebuilds unrecognized error types as plain Error and doesn't restore name. Code should branch on code. That's fixed separately in cloudflare/capnweb#289. With both changes, remote: true errors match production exactly, including name: "ArtifactsError"; I verified this end to end.

Testing

• New unit tests: devalue error round-trips (custom name and properties, built-in constructors, unchanged encoding without extra properties); Node proxy keeps name, code and numericCode thrown by an RPC binding. All three behavior tests fail without the source changes.
• Updated the raw-TCP opt-in assertions in remote-bindings-connect.spec.ts. experimental is still opt-in only.
• miniflare: full suite 1,664 passed (3 skipped) after the assertion update. remote-bindings: 31 passed. wrangler remote-bindings and startDevWorker tests: 160 passed. tsc, oxlint --type-aware and oxfmt clean.
• Manual check against production with read-only calls, before and after this change, through wrangler dev with remote: true, getPlatformProxy() and wrangler dev --remote. Results are in the table.

---

• Tests
  • Tests included/updated
  • Automated tests not possible - manual testing has been completed as follows:
  • Additional testing not necessary because:
• Public documentation
  • Cloudflare docs PR(s):
  • Documentation not necessary because: bug fix that restores production error behavior in local development

[changeset-bot]

🦋 Changeset detected

Latest commit: 74baf24

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

This PR includes changesets to release 8 packages

Name	Type
miniflare	Patch
wrangler	Patch
@cloudflare/deploy-helpers	Patch
@cloudflare/pages-shared	Patch
@cloudflare/remote-bindings	Patch
@cloudflare/runtime-types	Patch
@cloudflare/vite-plugin	Patch
@cloudflare/vitest-plugin	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[github-actions]

Hi @dinasaur404. Thanks for taking the time to contribute to Workers SDK.

This PR has been automatically closed because you are not currently a registered (vouched) collaborator for this repository.

AI tools now let our team generate proposed code changes quickly. Reviewing changes, checking that they solve the right problem, and maintaining code quality over time still take substantial care and effort. We therefore limit PRs to registered collaborators so we can focus that effort where it is most useful.

For the majority of external contributors, the most effective way to help is through issues: describing a problem or use case, providing a minimal reproduction, investigating its cause, or helping us verify a fix. Those contributions help us understand what needs to change and are very welcome.

We will take an initial look at this PR and decide whether it is something we want to invest time in reviewing and maintaining. We may reopen it if we decide to proceed, but we cannot guarantee that it will be reopened or receive a full review.

[workers-devprod]

Codeowners approval required for this PR:

• ✅ @cloudflare/wrangler

Show detailed file reviewers

[clanky-the-clanker]

✅ Approved — No issues found. The flag changes are consistent across the three workers, and the error serialization change is narrow and covered by tests.

_{The decision is advisory: this comment never approves, blocks or requests changes on the pull request.}

---

✅ All checks passed

🚀 Release: ✅ LGTM

Risk: Low. The changeset describes the combined fix and requests patch releases for the affected packages.

---

🔒 Security: ✅ LGTM

No security concerns. Revived error properties are limited to primitive values and set with Object.defineProperty as own properties of the error. They can't change the prototype or override message, stack or cause.

---

📖 AGENTS.md: ✅ LGTM

The change follows the repository conventions.

---

📋 Code Quality: ✅ LGTM

The compatibility-flag additions match across the three internal workers. The devalue Error reducer and reviver round-trip correctly, and errors without extra properties keep their old encoding. The reviver checks property types and protects message, stack and cause. Tests cover all three behaviour changes.

---

⚡ Performance: ✅ LGTM

Serializing an error now loops over its few own property names, which costs very little. The flag changes add nothing to hot paths.

---

📝 Documentation: ✅ LGTM

The changeset and the code comments describe the change accurately.

---

_{Reviewed commit: 74baf24d}

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commit: 74baf24

[devin-ai-integration]

Devin Review found 1 new potential issue.

[workers-devprod]

Codeowners reviews satisfied