build: decouple the Go modules with a workspace so Dependabot PRs stay green

.github/dependabot.yml

@@ -26,9 +26,16 @@ updates:
 
   # Go modules were not covered above, so Go advisories reached us only as a red
   # trivy-scan gate and had to be bumped by hand -- CVE-2026-84304 (grpc) in #203.
-  # Dependabot needs one entry per go.mod; there is no recursive directory match.
+  #
+  # `directories` is a shorthand for the two go.mod files, NOT a way to bundle them:
+  # Dependabot still opens one PR per directory. Bundling would need
+  # `group-by: dependency-name`, which is version-updates-only and splits one PR per
+  # dependency -- so it would leave security bumps, the reason this entry exists,
+  # unbundled. The root go.work is what keeps those per-directory PRs green; see #212.
   - package-ecosystem: gomod
-    directory: /gen/go
+    directories:
+      - /gen/go
+      - /remote-worker
     schedule:
       interval: weekly
     groups:
@@ -39,14 +46,3 @@ updates:
           - 'google.golang.org/grpc*'
           - 'google.golang.org/protobuf*'
           - 'google.golang.org/genproto*'
-
-  - package-ecosystem: gomod
-    directory: /remote-worker
-    schedule:
-      interval: weekly
-    groups:
-      grpc-protobuf:
-        patterns:
-          - 'google.golang.org/grpc*'
-          - 'google.golang.org/protobuf*'
-          - 'google.golang.org/genproto*'

.github/workflows/ci.yml

@@ -145,6 +145,19 @@ jobs:
           git diff --cached --exit-code -- packages/k8s-sandbox/src/gen gen \
             || { echo "::error::Generated stubs are out of date or untracked. Run 'buf generate' and commit."; exit 1; }
 
+      # A module left out of go.work falls back to standalone resolution and brings
+      # back the stale-go.mod failure the workspace exists to prevent (#212).
+      - name: Verify go.work covers every module
+        run: |
+          covered="$(go work edit -json | jq -r '.Use[].DiskPath')"
+          rc=0
+          while read -r mod; do
+            dir="./$(dirname "$mod")"
+            grep -qxF "$dir" <<<"$covered" \
+              || { echo "::error file=$mod::$mod is not listed in go.work -- add \"$dir\" to the use block."; rc=1; }
+          done < <(git ls-files | grep -E '(^|/)go\.mod$')
+          exit $rc
+
       - name: Build and test Go stubs
         run: cd gen/go && go build ./... && go test ./...
 
@@ -154,3 +167,15 @@ jobs:
           test -z "$(gofmt -l .)" || { echo "::error::gofmt needs running:"; gofmt -l .; exit 1; }
           go vet ./...
           go test -race ./...
+
+      # Advisory only. In workspace mode a stale go.mod no longer breaks the build, so
+      # this is hygiene rather than correctness -- and failing here would put Dependabot's
+      # coupled bumps back in the red, which is the whole point of #212. Neither module is
+      # consumed externally (gen/go is reached only through the local replace), so drift
+      # can be tidied whenever convenient.
+      - name: Check go.mod tidiness (advisory)
+        run: |
+          for mod in gen/go remote-worker; do
+            (cd "$mod" && go mod tidy -diff) \
+              || echo "::warning file=$mod/go.mod::$mod/go.mod is not tidy -- run 'cd $mod && go mod tidy'"
+          done

.gitignore

@@ -32,3 +32,7 @@ docs/plans/*
 # E2 writes each run's measured table here; experiments/RESULTS.md is the committed
 # baseline and is no longer overwritten by a test run (see experiments/README.md).
 experiments/.results/
+
+# Workspace-only checksums. Redundant with each module go.sum, and the checksum
+# database still verifies downloads without it -- one less sum file to keep in sync.
+go.work.sum

go.work

@@ -0,0 +1,15 @@
+// Both Go modules are coupled: remote-worker consumes gen/go through a local
+// `replace`, and the `proto` CI job builds both. Without a workspace, any bump to a
+// gen/go dependency leaves remote-worker/go.mod stale and the build fails with
+// "updates to go.mod needed" -- which Dependabot cannot fix, because the tidy has to
+// land in the same commit as the bump and its branches are not maintainer-writable.
+// In workspace mode the go command resolves one MVS across both modules, so the
+// modules can be bumped independently. See issue #212.
+//
+// Keep this `go` line in sync with both go.mod files (and CI's go-version-file).
+go 1.25.0
+
+use (
+	./gen/go
+	./remote-worker
+)

remote-worker/Dockerfile

@@ -8,6 +8,9 @@
 # RELAY_ADDR=sandbox-relay.default.svc:8443 (no port-forward needed in-cluster).
 FROM golang:1.25-alpine AS build
 WORKDIR /src
+# go.work first: it is what lets the two modules be bumped independently (see #212).
+# Without it the build here resolves each go.mod on its own and fails on a stale one.
+COPY go.work ./
 COPY gen/go/ ./gen/go/
 COPY remote-worker/ ./remote-worker/
 WORKDIR /src/remote-worker