diff --git a/.github/actions/upgrade-test-setup/action.yaml b/.github/actions/upgrade-test-setup/action.yaml
index 4eb4c7f93c..8a3dd0ce34 100644
--- a/.github/actions/upgrade-test-setup/action.yaml
+++ b/.github/actions/upgrade-test-setup/action.yaml
@@ -30,8 +30,11 @@ runs:
     - name: Resolve upgrade-from version
       id: resolve
       shell: bash
+      env:
+        # A merge group has no base_ref; its ref name is gh-readonly-queue/<base>/pr-N-<sha>.
+        BASE_REF: ${{ github.base_ref || github.event.merge_group.base_ref || github.ref_name }}
       run: |
-        base_ref="${GITHUB_BASE_REF:-${GITHUB_REF_NAME:-}}"
+        base_ref="${BASE_REF#refs/heads/}"
         is_release_line=false
         if [[ "$base_ref" =~ ^release/v[0-9]+\.[0-9]+\.x$ ]]; then
           is_release_line=true
@@ -41,7 +44,7 @@ runs:
           # prev-stable = the previous minor line's latest published version.
           # Before that line has a final release, use its latest prerelease so
           # main keeps upgrade coverage after the release branch is cut.
-          V="$(./scripts/prev-stable-version.sh)"
+          V="$(CURRENT_REF="$base_ref" ./scripts/prev-stable-version.sh)"
           if [ -z "$V" ]; then
             echo "no published version on the previous release line; skipping prev-stable leg."
             echo "skip=true" >> "$GITHUB_OUTPUT"
diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 9a8b686ef1..53cc2ac832 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -9,6 +9,7 @@ on:
     branches: [main, "release/**"]
     paths-ignore:
       - "**/*.md"
+  merge_group:
   workflow_dispatch:
 
 concurrency:
@@ -18,7 +19,8 @@ concurrency:
 env:
   # Cache key components for better organization
   CACHE_KEY_PREFIX: kagent-v2
-  BRANCH_CACHE_KEY: ${{ github.head_ref || github.ref_name }}
+  # Merge groups share one cache scope; their ref names are unique and would each write a throwaway one.
+  BRANCH_CACHE_KEY: ${{ github.head_ref || (github.event.merge_group.base_ref && 'merge-queue') || github.ref_name }}
   # Consistent builder configuration
   BUILDX_BUILDER_NAME: kagent-builder-v0.23.0
   BUILDX_VERSION: v0.23.0
diff --git a/.github/workflows/migration-immutability.yaml b/.github/workflows/migration-immutability.yaml
index f18526baf2..11f4e96f1b 100644
--- a/.github/workflows/migration-immutability.yaml
+++ b/.github/workflows/migration-immutability.yaml
@@ -5,6 +5,7 @@ on:
     branches: [main, "release/**"]
     paths:
       - "go/core/pkg/migrations/**"
+  merge_group:
 
 jobs:
   check:
@@ -15,8 +16,11 @@ jobs:
           fetch-depth: 0
 
       - name: Fail if any existing migration file was modified
+        env:
+          # A merge group has no base_ref; it only exposes the base branch as refs/heads/<branch>.
+          BASE_REF: ${{ github.base_ref || github.event.merge_group.base_ref }}
         run: |
-          BASE=$(git merge-base HEAD origin/${{ github.base_ref }})
+          BASE=$(git merge-base HEAD "origin/${BASE_REF#refs/heads/}")
           CHANGED=$(git diff --no-renames --name-status --diff-filter=MDR "$BASE" HEAD \
             -- 'go/core/pkg/migrations/**/*.sql' \
             | awk '$1 != "D" || $2 !~ /\.(up|down)\.sql$/ { print $2 }')
diff --git a/.github/workflows/sqlc-generate-check.yaml b/.github/workflows/sqlc-generate-check.yaml
index 4efb50604d..5280ec6932 100644
--- a/.github/workflows/sqlc-generate-check.yaml
+++ b/.github/workflows/sqlc-generate-check.yaml
@@ -7,6 +7,7 @@ on:
       - "go/core/internal/database/queries/**"
       - "go/core/internal/database/sqlc.yaml"
       - "go/core/pkg/migrations/**"
+  merge_group:
 
 jobs:
   check: