Convex runtime: crypto.subtle.deriveBits for ECDH not supported

[aboire]

Problem

PushForge lists Convex as "Fully supported" in the README, but buildPushHTTPRequest fails in the Convex default runtime because crypto.subtle.deriveBits for ECDH is not implemented.

Error

Not implemented: crypto.subtle.deriveBits for ECDH.
Consider calling an action defined in Node.js instead.
    at deriveSharedSecret (node_modules/@pushforge/builder/dist/lib/shared-secret.js:15:25)
    at encryptPayload (node_modules/@pushforge/builder/dist/lib/payload.js:173:41)
    at async buildPushHTTPRequest (node_modules/@pushforge/builder/dist/lib/request.js:147:60)

Details

• @pushforge/builder v2.0.1
• Convex exposes crypto.subtle but doesn't implement deriveBits for ECDH (P-256)
• The Convex example in the README uses a regular action (no "use node" directive)
• The only workaround is adding "use node" to the file, which forces the Node.js runtime

Suggestion

Either:

1. Update the README/docs to note that Convex requires "use node" for the action file
2. Or provide a fallback implementation that doesn't rely on deriveBits (if possible)

Thanks for the great library!

[linear]

WPN-30

[draphy]

@aboire Thanks for reporting this!

Option 1 is fine. ECDH is required by the Web Push spec (RFC 8291) so there's no alternative to deriveBits. Since "use node"; is a one-line fix, adding dependencies or a custom implementation isn't worth the complexity.

Updating the README now.

[Reshmarpillai]

@draphy I ran into this same issue and "use node"; fixed it. If the README hasn't been updated yet, happy to open a PR for it.