firebase apphosting:backends:get <backendId> exits 0 when the backend does not exist (only warns Backend "<id>" not found)

TL;DR

firebase apphosting:backends:get <backendId> exits 0 when the backend does not exist. It only logs the warning Backend "<id>" not found, so if firebase apphosting:backends:get ...; then treats a missing backend as present. Run it with --json and check .status and .result.name, not the exit code.

Context (observed, Nov 2026)

A Firebase App Hosting deploy script had to choose between "create the backend if it does not exist" and "roll out the existing backend". The exit code of firebase apphosting:backends:get "$BACKEND_ID" was 0 even though no such backend existed, so the existence check was wrong. Treat this as observed behavior. It may differ between firebase-tools versions.

Cause (confirmed in source)

In firebase-tools 15.35.0 (lib/commands/apphosting-backends-get.js) and on master (https://github.com/firebase/firebase-tools/blob/master/src/commands/apphosting-backends-get.ts) as of 2026-11-06, the command lists backends in all locations and filters them by ID. When nothing matches, it does this:

if (backendsList.length === 0) {
  logWarning(`Backend "${backend}" not found`);
  return;
}

No error is thrown, so the CLI exits successfully. A failing list call does throw (Failed to get backend: ...) and exits non-zero. With --json, the 15.35.0 CLI disables console logging and writes {"status": "success", "result": <return value>} on success or {"status": "error", "error": "<message>"} on failure. For a missing backend the return value is undefined, so result is absent.

Fix

out="$(firebase apphosting:backends:get "$BACKEND_ID" --project "$PROJECT_ID" --json 2>/dev/null)" || true
state="$(printf '%s' "$out" | node -e '
let s = ""; process.stdin.on("data", (d) => (s += d)).on("end", () => {
  let j; try { j = JSON.parse(s); } catch { return console.log("error"); }
  if (j.status !== "success") return console.log("error");
  console.log(j.result && j.result.name ? "exists" : "missing");
});')"
case "$state" in
  exists)  echo "backend exists -> roll out" ;;
  missing) echo "backend missing -> create" ;;
  *)       echo "could not check the backend: $out" >&2; exit 1 ;;
esac

The Firebase CLI already needs Node, so node is available. With jq instead: jq -r 'if .status != "success" then "error" elif .result.name then "exists" else "missing" end'. Keep the error case separate. Otherwise an auth or API failure looks like "missing" and the script tries to create a backend that already exists.

Verify

firebase apphosting:backends:get does-not-exist-123 --project "$PROJECT_ID" --json; echo "exit=$?"

Expected with 15.35.0: {"status": "success"} with no result (pretty-printed), then exit=0. An existing backend ID returns result.name like projects/PROJECT/locations/REGION/backends/ID. Re-run this check after upgrading firebase-tools.