Keep Iterate extensions as one minimal patch on Cap’n Web 0.12.0

[jonastemplestein]

Keep Iterate's WebSocket upgrade and onCall extensions as one commit directly on vanilla capnweb@0.12.0 (7702075d4122e6808512ee50acc591310b77da7a). The release-relative patch is 26 files, +2,372 / −46, including tests, documentation, and scoped publishing. Runtime changes are confined to six files (+806 / −30); 613 lines are the new WebSocket module.

Scope

• Serialize WebSocket upgrade Responses using existing RPC streams. Preserve upgradeWebSocketResponse, portable WebSocketPair, native Workers upgrades, close propagation, queued-frame draining, copied binary buffers, listener isolation, and single-transfer ownership. Binary events contain exactly-sized ArrayBuffers.
• Carry runtime-independent onCall through promise pipelining. Enforce one synchronous invocation and release arguments or results when a wrapper fails.
• Keep one three-line stream timing guard: zero-duration samples must not make the flow-control window NaN and permanently block writes. A focused regression fails without it; the unmodified upstream browser suite also reproduces the problem.
• Keep upstream types, validator, and other RPC/stream behavior. Add focused feature tests, concise fork documentation, package identity, and minimal workflow changes for fork CI and tag-triggered scoped npm publication. Cloudflare-only workflows retain owner guards.

Claude Opus 5.5 implemented this reduction with xhigh reasoning following the earlier upstream issues, discussions, and remote-branch review. Package version remains 0.12.2 with a pending patch changeset.

Validation

• Library build and type tests passed; 1,469 Vitest tests + 16 Bun tests passed across Node, workerd, Chromium, Firefox, WebKit, and Bun.
• Installed the packed candidate throughout iterate/iterate at latest main, 3802a1b28c6a89cfe78b6f12cfce873eaa61b092. OS production build and the entire monorepo type check passed.
• 251 SDK tests, 7 CLI tunnel tests, 122 targeted unit/Workers tests, and ten relevant E2E files passed (67 passed, 3 existing expected failures, 5 deployment-only skips). Coverage includes Node-provider WebSocket upgrades, CLI tunnels, ingress routes, sockets surviving context resets, RPC values and lifetimes, reconnect/attach, connectors, secrets, sessions, and wire round trips.
• Confirmed the consumer's installed ESM, CJS, and declarations match the final build. No consumer source changes were required; temporary package overrides were restored.

These are local workerd checks, not a production deployment. Package publication and the tag-triggered release workflow have not been exercised. Remaining forwarding and buffering limitations are documented in FORK.md.

History and adoption

Landed on main as fc68b9cf214ce8b0ab0ef8c3c4136934c27cad6c: exactly one commit above vanilla 0.12.0. The PR was reviewed against pristine upstream-0.12, then retargeted to main and marked merged when the reviewed commit landed. The former main is preserved at archive/main-before-0.12-20260924; upstream-0.12 remains pristine. Post-merge Test and Semgrep workflows passed.

[pkg-pr-new]

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npm i https://pkg.pr.new/iterate/capnweb/@iterate-com/capnweb@9

commit: fc68b9c

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