diff --git a/.github/workflows/notify-merge.yml b/.github/workflows/notify-merge.yml
new file mode 100644
index 0000000..2f076d2
--- /dev/null
+++ b/.github/workflows/notify-merge.yml
@@ -0,0 +1,36 @@
+name: notify-sourcey-merge
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - "entities/**/*.yaml"
+
+permissions:
+  contents: read
+
+concurrency:
+  group: notify-merge-${{ github.sha }}
+  cancel-in-progress: false
+
+jobs:
+  notify:
+    if: github.event.before != '0000000000000000000000000000000000000000'
+    runs-on: ubuntu-latest
+    timeout-minutes: 2
+    steps:
+      # -f sends every field as a string; -F would turn the numeric
+      # repository id into a JSON number and the workspace lane pins it as text.
+      - name: Dispatch the exact merged head to Sourcey
+        env:
+          GH_TOKEN: ${{ secrets.SOURCEY_WORKSPACE_DISPATCH_TOKEN }}
+          BASE_SHA: ${{ github.event.before }}
+          HEAD_SHA: ${{ github.sha }}
+          REPOSITORY_ID: ${{ github.repository_id }}
+        run: |
+          test -n "$GH_TOKEN"
+          gh api --method POST repos/sourcey/sourcey-workspace/dispatches \
+            -f event_type=agent-ready-services-merge \
+            -f client_payload[base_sha]="$BASE_SHA" \
+            -f client_payload[head_sha]="$HEAD_SHA" \
+            -f client_payload[repository_id]="$REPOSITORY_ID"
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 7bccb4d..a937689 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -278,7 +278,9 @@ curl --fail-with-body --silent --show-error -H 'content-type: application/json'
 This is the same public package, signed identity-context protocol, and rooted trust input used by
 CI—not a second validator. Context issuance is explicit; final validation is offline over those bytes.
 
-After merge, Sourcey retains the exact repository, commit, path, Git blob OID,
-and SHA-256 blob digest before any private assessment begins. Identity,
-authority, evidence coverage, human review, and release admission remain
-separate gates.
+After merge, a workflow in this repository tells Sourcey the exact merged head
+(`notify-merge.yml`; it sends only the base and head commits and this
+repository's id). Sourcey then retains the exact repository, commit, path, Git
+blob OID, and SHA-256 blob digest before any private assessment begins.
+Identity, authority, evidence coverage, human review, and release admission
+remain separate gates.