diff --git a/.github/actions/preview-delivery/action.yml b/.github/actions/preview-delivery/action.yml
index 4e7f5e9..592a2c7 100644
--- a/.github/actions/preview-delivery/action.yml
+++ b/.github/actions/preview-delivery/action.yml
@@ -479,6 +479,19 @@ runs:
         PR_NUMBER: ${{ inputs.pr_number }}
         WEB_URL: ${{ steps.heroku.outputs.web_url }}
       run: |
+        if ! docker run --rm \
+          --entrypoint python \
+          "inkcre-preview-release:$HEAD_SHA" \
+          -c \
+          'from pathlib import Path; raise SystemExit(0 if Path("/app/scripts/configure_peer_runtime.py").is_file() else 1)'; then
+          {
+            echo "### Preview runtime compatibility"
+            echo
+            echo "- Peer advertisement: skipped for a pre-Peer Client image"
+          } >> "$GITHUB_STEP_SUMMARY"
+          exit 0
+        fi
+
         peer_id="$(
           python -c \
             "import uuid; print(uuid.uuid5(uuid.NAMESPACE_URL, 'inkcre-core-py-pr-$PR_NUMBER'))"
diff --git a/tasks/preview-jwt-authority/packet.md b/tasks/preview-jwt-authority/packet.md
index 44f55bc..852e8d8 100644
--- a/tasks/preview-jwt-authority/packet.md
+++ b/tasks/preview-jwt-authority/packet.md
@@ -30,11 +30,14 @@ production and same-repository pull-request previews.
 - The repository Secret, Production Core/PostgREST, PR 52 Core/PostgREST, and the browser
   Preview setting have been converged to the selected key without exposing it in Git.
 - Local focused and full repository contracts pass. The live PostgREST transport probe is
-  independently blocked because the database cleanup removed the Preview relations after
-  Core cached its ready state; PR 52 requires one complete Preview initialization run.
+  independently blocked because PR 52 intentionally uses the pre-Peer Client schema while
+  the current preview controller unconditionally invokes the newer Peer advertisement script.
+- The compatibility fix keeps Peer convergence mandatory for capable images and skips only
+  images that prove they do not contain `scripts/configure_peer_runtime.py`; health and
+  authenticated PostgREST probes remain mandatory in both cases.
 
 ## Next Step
 
-Commit and push the verified source slice after explicit authorization, admit it to `main`,
-rerun PR 52 Preview initialization, verify the live transport, then delete the obsolete
-`PREVIEW_JWT_SEED` environment secret.
+Verify and admit the narrow preview-controller compatibility fix to `main`, rerun PR 52
+Preview initialization, and verify the live authenticated transport against the Client
+baseline.
diff --git a/tests/test_preview_delivery.py b/tests/test_preview_delivery.py
index 96d5af2..74a5804 100644
--- a/tests/test_preview_delivery.py
+++ b/tests/test_preview_delivery.py
@@ -26,6 +26,8 @@ def test_preview_builds_releases_probes_and_cleans_postgrest():
   assert "derive_preview_jwt_secret.py" not in delivery
   assert "registry.heroku.com/$POSTGREST_APP_NAME/web" in delivery
   assert 'heroku ps:scale web=1:eco --app "$POSTGREST_APP_NAME"' in delivery
+  assert 'Path("/app/scripts/configure_peer_runtime.py").is_file()' in delivery
+  assert "Peer advertisement: skipped for a pre-Peer Client image" in delivery
   assert "scripts/verify_postgrest_contract.py" in delivery
   assert '--base-url "$POSTGREST_URL"' in delivery