diff --git a/.github/workflows/release-pr.yml b/.github/workflows/release-pr.yml
index dabdf5d..e529486 100644
--- a/.github/workflows/release-pr.yml
+++ b/.github/workflows/release-pr.yml
@@ -33,13 +33,24 @@ jobs:
         with:
           fetch-depth: 0
 
-      # The monorel CI action runs `go mod tidy` per sub-module to refresh
-      # go.sum entries. Sub-modules require Go 1.25; the runner default is
-      # older and the action sets GOTOOLCHAIN=local, so install the Go we
-      # need explicitly before invoking monorel.
+      # The monorel CI action runs `go mod tidy` per sub-module with
+      # GOPROXY=off, so it can only resolve modules already in the local
+      # cache. Sub-modules also require Go 1.25, which the runner default
+      # doesn't supply. Install Go 1.25 with caching enabled, then prime
+      # the module cache via `go mod download` per module so monorel's
+      # GOPROXY=off tidy can find every transitive dep.
       - uses: actions/setup-go@v5
         with:
           go-version: '1.25'
+          cache: true
+          cache-dependency-path: '**/go.sum'
+
+      - name: Prime module cache for monorel tidy
+        run: |
+          set -euo pipefail
+          while IFS= read -r mod; do
+            (cd "$(dirname "$mod")" && go mod download)
+          done < <(find . -name go.mod -not -path './.git/*' | sort)
 
       - uses: disaresta-org/monorel/ci/github@v0.11.0
         with:
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index fb6e675..a2a4602 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -42,13 +42,24 @@ jobs:
         with:
           fetch-depth: 0
 
-      # The monorel CI action runs `go mod tidy` per sub-module to refresh
-      # go.sum entries. Sub-modules require Go 1.25; the runner default is
-      # older and the action sets GOTOOLCHAIN=local, so install the Go we
-      # need explicitly before invoking monorel.
+      # The monorel CI action runs `go mod tidy` per sub-module with
+      # GOPROXY=off, so it can only resolve modules already in the local
+      # cache. Sub-modules also require Go 1.25, which the runner default
+      # doesn't supply. Install Go 1.25 with caching enabled, then prime
+      # the module cache via `go mod download` per module so monorel's
+      # GOPROXY=off tidy can find every transitive dep.
       - uses: actions/setup-go@v5
         with:
           go-version: '1.25'
+          cache: true
+          cache-dependency-path: '**/go.sum'
+
+      - name: Prime module cache for monorel tidy
+        run: |
+          set -euo pipefail
+          while IFS= read -r mod; do
+            (cd "$(dirname "$mod")" && go mod download)
+          done < <(find . -name go.mod -not -path './.git/*' | sort)
 
       - uses: disaresta-org/monorel/ci/github@v0.11.0
         with: