Nodejs26 rejected at deploy, though Cloud Run functions supports it (Preview) #11393

[REQUIRED] Environment info

firebase-tools: 15.34.2

Platform: Linux (Debian 13), Node v24.22.1

[REQUIRED] Test case

firebase.json
{ "functions": { "source": "." } }

package.json
{ "engines": { "node": "26" }, "main": "index.js" }

index.js can be empty: deploy fails before it loads the source.

Using "runtime": "nodejs26" in firebase.json in place of engines.node gives the same result.

[REQUIRED] Steps to reproduce

1. Create the three files above.
2. Run firebase deploy --only functions --project --debug.

[REQUIRED] Expected behavior

The deploy goes through on the nodejs26 runtime, perhaps with a warning that it's in Preview. Cloud Run functions already lists nodejs26 as Preview: https://docs.cloud.google.com/run/docs/runtimes/nodejs

[REQUIRED] Actual behavior

i functions: ensuring required API cloudfunctions.googleapis.com is enabled...
i functions: ensuring required API cloudbuild.googleapis.com is enabled...
i artifactregistry: ensuring required API artifactregistry.googleapis.com is enabled...
✔ functions: required API cloudfunctions.googleapis.com is enabled
✔ artifactregistry: required API artifactregistry.googleapis.com is enabled
✔ functions: required API cloudbuild.googleapis.com is enabled

Error: Detected node engine 26 in package.json, which is not a supported version. Valid versions are 20, 22, 24

src/deploy/functions/runtimes/supported/types.ts on main has no nodejs26 entry; the list stops at nodejs24. Node.js 26 is now Active LTS. Adding it with status: "beta" until Cloud Run marks it GA would let projects deploy on Node 26, and match the runtime they already test and build on.