Support JSRPC for remote bindings #10249

penalosa · 2025-08-06T14:44:53Z

Fixes https://jira.cfdata.org/browse/DEVX-2042, https://jira.cfdata.org/browse/DEVX-1929, https://jira.cfdata.org/browse/DEVX-1933

Support JSRPC bindings! This uses a vendored version of the upcoming @cloudflare/jsrpc library. See code for detailed comments.

Tests
- Tests included
- Tests not necessary because:
Public documentation
- Cloudflare docs PR(s):
- Documentation not necessary because: captured by separate ticket
Wrangler V3 Backport
- Wrangler PR:
- Not necessary because: not a V3 feature

changeset-bot · 2025-08-06T14:44:57Z

🦋 Changeset detected

Latest commit: ccbb30d

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

This PR includes changesets to release 5 packages

Name	Type
miniflare	Patch
wrangler	Patch
@cloudflare/pages-shared	Patch
@cloudflare/vite-plugin	Patch
@cloudflare/vitest-pool-workers	Patch

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penalosa · 2025-08-06T14:45:44Z

packages/miniflare/src/workers/shared/remote-proxy-client.worker.ts

+constructor(ctx: ExecutionContext, env: Env) {
+const url = new URL(env.remoteProxyConnectionString);
+url.protocol = "ws:";
+url.searchParams.set("MF-Binding", env.binding);
+const session = rpcOverWebSocket(url.href);
+const stub = session.getStub();
+
+super(ctx, env);
+
+return new Proxy(this, {
+get(target, prop) {
+if (Reflect.has(target, prop)) {
+return Reflect.get(target, prop);
+}
+
+const value = Reflect.get(stub, prop);
+return value;
+},
+});
+}


This proxy code is inspired by that written for rpc in local dev with the router worker—thanks @CarmenPopoviciu!

dario-piotrowicz

Looks great to me! 😄

I just left a few comments (some just asking info so that I can understand the implementation better 🙂)

However one thing I'd like to ask however is, I can see you'd chosen to use rpcOverWebSocket, have you considered generally using rpcOverHttp instead?
It would likely be slightly slower and more noisy but since we're not talking about something that needs to handle live traffic that could be acceptable. Using non-persistent http could help us avoid persistence issues that can happen for different reasons (such as sessions restarts, weird remote preview bugs and vite environments reloads).

I am by no means saying that I think rpcOverHttp would be more appropriate/better, I'm just curious if you've considered or tested using that instead of the permanent websocket connection 🙂

packages/wrangler/src/utils/print-bindings.ts

packages/wrangler/e2e/remote-binding/wrangler-remote-resources.test.ts

packages/miniflare/src/workers/shared/jsrpc.d.ts

packages/miniflare/src/workers/shared/remote-proxy-client.worker.ts

penalosa · 2025-08-12T09:42:50Z

have you considered generally using rpcOverHttp instead

I was hoping to be able to use that, yes! Unfortunately it requires an explicit batch.send() operation to actually send things over the wire, which is a non-starter for us (since we don't control the code interacting with the RPC stub and don't know when it's appropriate to initiate that)

dario-piotrowicz · 2025-08-12T10:12:02Z

since we don't control the code interacting with the RPC stub and don't know when it's appropriate to initiate that

Couldn't we do that as part of the proxy objects? 🤔 as in, when we return a function in a Proxy getter, we could wrap that function so that after its execution it runs batch.send() no?

For example something like:

new Proxy(this, { get(target, prop) { if (Reflect.has(target, prop)) { return Reflect.get(target, prop); } const stubProp = Reflect.get(stub, prop); if (typeof stubProp === 'function') { return async (...args) => { const resPromise = stubProp(...args); batch.send(); return resPromise; }; } return stubProp; } });

penalosa · 2025-08-12T11:50:18Z

Couldn't we do that as part of the proxy objects? 🤔 as in, when we return a function in a Proxy getter, we could wrap that function so that after its execution it runs batch.send() no?

There are lots of edge cases here:

What if the value is a getter? When would we send the batch?
What if the function returns an RpcTarget that the user then interacts with further? We'd have to do another batch.send() but there wouldn't be a natural place to do this

dario-piotrowicz · 2025-08-12T23:23:17Z

Couldn't we do that as part of the proxy objects? 🤔 as in, when we return a function in a Proxy getter, we could wrap that function so that after its execution it runs batch.send() no?

There are lots of edge cases here:

What if the value is a getter? When would we send the batch?

What if the function returns an RpcTarget that the user then interacts with further? We'd have to do another batch.send() but there wouldn't be a natural place to do this

Yeah good points 🤔👍

pkg-pr-new · 2025-08-14T18:16:43Z

create-cloudflare

npm i https://pkg.pr.new/create-cloudflare@10249

@cloudflare/kv-asset-handler

npm i https://pkg.pr.new/@cloudflare/kv-asset-handler@10249

miniflare

npm i https://pkg.pr.new/miniflare@10249

@cloudflare/pages-shared

npm i https://pkg.pr.new/@cloudflare/pages-shared@10249

@cloudflare/unenv-preset

npm i https://pkg.pr.new/@cloudflare/unenv-preset@10249

@cloudflare/vite-plugin

npm i https://pkg.pr.new/@cloudflare/vite-plugin@10249

@cloudflare/vitest-pool-workers

npm i https://pkg.pr.new/@cloudflare/vitest-pool-workers@10249

@cloudflare/workers-editor-shared

npm i https://pkg.pr.new/@cloudflare/workers-editor-shared@10249

wrangler

npm i https://pkg.pr.new/wrangler@10249

commit: 357e32f

Create yellow-kangaroos-bathe.md fix checks fix checks Increase timeouts more logging static workers static workers pre-compile proxy server worker

petebacondarwin · 2025-08-15T13:29:54Z

packages/wrangler/tsup.config.ts

 sourcemap: process.env.SOURCEMAPS !== "false",
 sourcesContent: false,
 metafile: true,
+external: ["cloudflare:email", "cloudflare:workers"],


NIT: this can take regular expressions. So maybe?

Suggested change

external: ["cloudflare:email", "cloudflare:workers"],

external: /^cloudflare:/,

It's type seems to be BuildOptions.external?: string[] | undefined?

.gitignore

.prettierignore

packages/vite-plugin-cloudflare/e2e/remote-bindings.test.ts

dario-piotrowicz · 2025-08-15T13:21:37Z

packages/wrangler/package.json

 "@cloudflare/cli": "workspace:*",
 "@cloudflare/containers-shared": "workspace:*",
 "@cloudflare/eslint-config-worker": "workspace:*",
+"@cloudflare/jsrpc": "link:../../vendor/jsrpc",


I wonder, wouldn't it be cleaner adding `"vendor/*" directory to the packages list in "pnpm-workspace.yaml" and treat jsrpc as any other workspace package? 🤔

Potentially? But I wanted to draw a clear difference between this and other packages—e.g. we're not running JSRPC's tests, and we're just including the built output.

What would the benefit of treating it as a workspace package be?

I was just wondering it that'd be cleaner, pnpm could also optimize something... but it is not a huge deal I'm happy with the current approach I was just wondering 🙂

packages/wrangler/templates/remoteBindings/ProxyServerWorker.ts

packages/miniflare/src/plugins/dispatch-namespace/index.ts

dario-piotrowicz

Amazing stuff! 😄 🚀

workers-devprod added this to workers-sdk Aug 6, 2025

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penalosa commented Aug 6, 2025

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penalosa requested a review from a team as a code owner August 14, 2025 19:25

Support RPC bindings

5bab92a

Create yellow-kangaroos-bathe.md fix checks fix checks Increase timeouts more logging static workers static workers pre-compile proxy server worker

penalosa force-pushed the penalosa/remote-bindings-rpc branch from 87b55c2 to 5bab92a Compare August 15, 2025 12:20

Mark cloudflare:* as external in CI tests

ccbb30d

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penalosa merged commit 875197a into main Aug 15, 2025
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Version Packages #10372

Merged

This was referenced Sep 3, 2025

Update remote bindings docs in regards to RPC now being supported cloudflare/cloudflare-docs#24903

Merged

remove outdated note saying that RPC is not supported in remote service bindings cloudflare/cloudflare-docs#24982

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	external: ["cloudflare:email", "cloudflare:workers"],
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