diff --git a/app/Auth/AuthException.php b/app/Auth/AuthException.php
index 49772976..8d38d5ae 100644
--- a/app/Auth/AuthException.php
+++ b/app/Auth/AuthException.php
@@ -3,6 +3,7 @@
 namespace App\Auth;
 
 use RuntimeException;
+use Throwable;
 
 final class AuthException extends RuntimeException
 {
@@ -10,13 +11,14 @@ private function __construct(
         private readonly int $status,
         private readonly string $reason,
         string $message,
+        ?Throwable $previous = null,
     ) {
-        parent::__construct($message);
+        parent::__construct($message, 0, $previous);
     }
 
-    public static function configuration(string $message): self
+    public static function configuration(string $message, ?Throwable $previous = null): self
     {
-        return new self(500, 'server_error', $message);
+        return new self(500, 'server_error', $message, $previous);
     }
 
     public static function unauthenticated(string $message): self
diff --git a/app/Auth/ConfiguredAuthProvider.php b/app/Auth/ConfiguredAuthProvider.php
index dbafea60..a638d041 100644
--- a/app/Auth/ConfiguredAuthProvider.php
+++ b/app/Auth/ConfiguredAuthProvider.php
@@ -111,8 +111,8 @@ private function authenticateToken(Request $request): Principal
         if ($runtimeCredentialsEnabled) {
             try {
                 $credential = RuntimeCredential::activeForToken($provided);
-            } catch (\Throwable) {
-                throw AuthException::configuration('Database runtime credential authentication is enabled but unavailable.');
+            } catch (\Throwable $exception) {
+                throw AuthException::configuration('Database runtime credential authentication is enabled but unavailable.', $exception);
             }
 
             if ($credential instanceof RuntimeCredential) {
diff --git a/app/Http/Middleware/Authenticate.php b/app/Http/Middleware/Authenticate.php
index 4063864e..3a856172 100644
--- a/app/Http/Middleware/Authenticate.php
+++ b/app/Http/Middleware/Authenticate.php
@@ -5,6 +5,7 @@
 use App\Auth\AuthException;
 use App\Auth\Principal;
 use App\Contracts\AuthProvider;
+use App\Support\BackendUnavailable;
 use App\Support\ControlPlaneProtocol;
 use App\Support\RuntimeExternalPayloadAudit;
 use App\Support\WorkerProtocol;
@@ -32,6 +33,11 @@ public function handle(Request $request, Closure $next): Response
         try {
             $principal = $this->authProvider->authenticate($request);
         } catch (AuthException $exception) {
+            if (BackendUnavailable::is($exception)
+                && ($response = BackendUnavailable::workerResponse($request)) !== null) {
+                return $response;
+            }
+
             return self::error($request, $exception->status(), $exception->reason(), $exception->getMessage());
         }
 
diff --git a/app/Http/Middleware/RequireWorkflowBootstrapReady.php b/app/Http/Middleware/RequireWorkflowBootstrapReady.php
index fee3e372..fd9f528a 100644
--- a/app/Http/Middleware/RequireWorkflowBootstrapReady.php
+++ b/app/Http/Middleware/RequireWorkflowBootstrapReady.php
@@ -2,6 +2,7 @@
 
 namespace App\Http\Middleware;
 
+use App\Support\BackendUnavailable;
 use App\Support\ControlPlaneProtocol;
 use App\Support\ServerReadiness;
 use App\Support\WorkerProtocol;
@@ -19,6 +20,11 @@ public function __construct(
     public function handle(Request $request, Closure $next): Response
     {
         $status = $this->readiness->bootstrapStatus();
+        if (($status['reason'] ?? null) === 'backend_unavailable'
+            && ($response = BackendUnavailable::workerResponse($request)) !== null) {
+            return $response;
+        }
+
         $blockedBy = is_array($status['blocked_by'] ?? null)
             ? array_values(array_filter($status['blocked_by'], static fn (mixed $value): bool => is_string($value) && $value !== ''))
             : [];
diff --git a/app/Support/BackendUnavailable.php b/app/Support/BackendUnavailable.php
new file mode 100644
index 00000000..2302b702
--- /dev/null
+++ b/app/Support/BackendUnavailable.php
@@ -0,0 +1,85 @@
+<?php
+
+namespace App\Support;
+
+use Illuminate\Http\JsonResponse;
+use Illuminate\Http\Request;
+use PDOException;
+use Throwable;
+
+final class BackendUnavailable
+{
+    public static function is(Throwable $exception): bool
+    {
+        for ($current = $exception; $current !== null; $current = $current->getPrevious()) {
+            if (! $current instanceof PDOException || ! is_array($current->errorInfo)) {
+                continue;
+            }
+
+            [$state, $code] = $current->errorInfo + [null, null];
+
+            // Use driver fields, never SQL text or customer-controlled bindings.
+            if (($state === 'HY000' && in_array((int) $code, [2002, 2003, 2006, 2013, 2055], true))
+                || in_array($state, ['08000', '08001', '08003', '08006', '08007', '08S01', '57P01', '57P02', '57P03'], true)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    public static function workerResponse(Request $request): ?JsonResponse
+    {
+        if (! WorkerProtocol::isWorkerPlaneRequest($request)
+            || ! WorkerProtocol::requestUsesCompatibleProtocolVersion($request)) {
+            return null;
+        }
+
+        $operation = match (true) {
+            $request->is('api/worker/workflow-tasks/poll') => 'poll_workflow_task',
+            $request->is('api/worker/activity-tasks/poll') => 'poll_activity_task',
+            $request->is('api/worker/query-tasks/poll') => 'poll_query_task',
+            $request->is('api/worker/update-validation-tasks/poll') => 'poll_update_validation_task',
+            $request->is('api/worker/register') => 'register_worker',
+            $request->is('api/worker/heartbeat') => 'heartbeat_worker',
+            default => null,
+        };
+        if ($operation === null) {
+            return null;
+        }
+
+        $workerId = self::identity($request->input('worker_id'));
+        $taskQueue = self::identity($request->input('task_queue'));
+        $pollId = self::identity($request->input('poll_request_id'));
+        $isPoll = str_starts_with($operation, 'poll_');
+        $payload = [
+            'reason' => 'backend_unavailable',
+            'message' => 'The database is temporarily unavailable. Retry the same request with backoff; its outcome may be unknown.',
+            'operation' => $operation,
+            'outcome' => 'unknown',
+            'worker_id' => $workerId,
+            'task_queue' => $taskQueue,
+            'retryable' => $workerId !== null
+                && ($operation === 'heartbeat_worker' || $taskQueue !== null)
+                && (! $isPoll || $pollId !== null),
+            'retry_after_seconds' => 1,
+        ];
+        if ($isPoll) {
+            // A lost connection can follow COMMIT. Reusing this ID lets native
+            // lease bindings reconcile it; task=null is not proof of no lease.
+            $payload += [
+                'task' => null,
+                'poll_status' => 'backend_unavailable',
+                'poll_request_id' => $pollId,
+                'retry_same_poll_request_id' => true,
+            ];
+        }
+
+        return WorkerProtocol::json($payload, 503)->header('Retry-After', '1');
+    }
+
+    private static function identity(mixed $value): ?string
+    {
+        return is_string($value) && $value !== '' && strlen($value) <= 255 ? $value : null;
+    }
+}
diff --git a/app/Support/ServerReadiness.php b/app/Support/ServerReadiness.php
index d9501d65..bf9abebd 100644
--- a/app/Support/ServerReadiness.php
+++ b/app/Support/ServerReadiness.php
@@ -92,6 +92,7 @@ private function databaseCheck(): array
             return [
                 'status' => 'unavailable',
                 'message' => $exception->getMessage(),
+                'reason' => BackendUnavailable::is($exception) ? 'backend_unavailable' : null,
             ];
         }
     }
@@ -109,6 +110,7 @@ private function migrationCheck(): array
             return [
                 'status' => 'unavailable',
                 'message' => $exception->getMessage(),
+                'reason' => BackendUnavailable::is($exception) ? 'backend_unavailable' : null,
             ];
         }
 
@@ -243,6 +245,7 @@ private function queueCheck(): array
             return $check + [
                 'status' => 'unavailable',
                 'message' => $exception->getMessage(),
+                'reason' => BackendUnavailable::is($exception) ? 'backend_unavailable' : null,
             ];
         }
     }
@@ -555,10 +558,12 @@ private function workflowCheck(array $checks): array
     private function bootstrapCheck(array $checks): array
     {
         $blockedBy = [];
+        $reason = null;
 
         foreach (['database', 'migrations', 'queue'] as $key) {
             if (! self::statusAllowsReady($checks[$key]['status'] ?? null)) {
                 $blockedBy[] = $key;
+                $reason ??= $checks[$key]['reason'] ?? null;
             }
         }
 
@@ -566,6 +571,7 @@ private function bootstrapCheck(array $checks): array
             return [
                 'status' => 'blocked',
                 'blocked_by' => $blockedBy,
+                'reason' => $reason,
                 'remediation' => 'Restore database connectivity and run server-bootstrap to migrate workflow and configured queue storage before serving workflow v2 traffic.',
             ];
         }
@@ -717,7 +723,7 @@ private function normalizeWorkflowCheck(array $check): array
             'checks' => is_array($check['checks'] ?? null) ? array_values($check['checks']) : [],
         ];
 
-        foreach (['blocked_by', 'message', 'remediation'] as $key) {
+        foreach (['blocked_by', 'message', 'remediation', 'reason'] as $key) {
             if (array_key_exists($key, $check)) {
                 $normalized[$key] = $check[$key];
             }
diff --git a/bootstrap/app.php b/bootstrap/app.php
index 10904bcb..d6f735bd 100644
--- a/bootstrap/app.php
+++ b/bootstrap/app.php
@@ -4,6 +4,7 @@
 use App\Http\Middleware\EnforcePayloadLimits;
 use App\Http\Middleware\RemoveServerHeader;
 use App\Support\BackendLockPressure;
+use App\Support\BackendUnavailable;
 use App\Support\ControlPlaneFailureDiagnostics;
 use App\Support\ControlPlaneOperation;
 use App\Support\ControlPlaneProtocol;
@@ -40,6 +41,12 @@
         ]);
     })
     ->withExceptions(function (Exceptions $exceptions) {
+        $exceptions->render(function (Throwable $exception, Request $request) {
+            return BackendUnavailable::is($exception)
+                ? BackendUnavailable::workerResponse($request)
+                : null;
+        });
+
         $exceptions->render(function (NamespaceDurableStateException $exception, Request $request) {
             $payload = array_filter([
                 'schema' => 'durable-workflow.v2.namespace-durable-state-error.v1',
diff --git a/composer.json b/composer.json
index f70de7f5..31febed9 100644
--- a/composer.json
+++ b/composer.json
@@ -48,7 +48,7 @@
     },
     "extra": {
         "durable-workflow": {
-            "product-train": "2.2.0"
+            "product-train": "2.2.1"
         },
         "laravel": {
             "dont-discover": []
diff --git a/composer.lock b/composer.lock
index fefc9bb2..fcf08cad 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "3ae0ae62f86d838b1bb51b98c0595c25",
+    "content-hash": "74de81dfe7587091bf9b40d221ffb410",
     "packages": [
         {
             "name": "apache/avro",
diff --git a/docker-compose.dedicated-matching.yml b/docker-compose.dedicated-matching.yml
index f6ca4283..93264db2 100644
--- a/docker-compose.dedicated-matching.yml
+++ b/docker-compose.dedicated-matching.yml
@@ -32,13 +32,13 @@ name: durable-workflow-server
 # daemon reports `shape: dedicated`.
 
 # Generated by scripts/ci/sync-source-release.mjs. Do not edit the fallback.
-x-server-image: &server-image ${DW_SERVER_IMAGE:-durableworkflow/server:${DW_SERVER_TAG:-2.2.0}}
+x-server-image: &server-image ${DW_SERVER_IMAGE:-durableworkflow/server:${DW_SERVER_TAG:-2.2.1}}
 
 x-server-environment: &server-environment
   APP_NAME: "Durable Workflow Server"
   APP_ENV: ${APP_ENV:-local}
   DW_SERVER_KEY: ${DW_SERVER_KEY:-}
-  APP_VERSION: ${APP_VERSION:-${DW_SERVER_TAG:-2.2.0}}
+  APP_VERSION: ${APP_VERSION:-${DW_SERVER_TAG:-2.2.1}}
   APP_DEBUG: ${APP_DEBUG:-false}
   DB_CONNECTION: mysql
   DB_HOST: mysql
diff --git a/docker-compose.memo-rolling.yml b/docker-compose.memo-rolling.yml
index 8da222b7..29a2b6ed 100644
--- a/docker-compose.memo-rolling.yml
+++ b/docker-compose.memo-rolling.yml
@@ -49,14 +49,14 @@ services:
     command: ["server-bootstrap"]
     environment:
       <<: *runtime-environment
-      APP_VERSION: ${APP_VERSION:-2.2.0}
+      APP_VERSION: ${APP_VERSION:-2.2.1}
 
   successor:
     image: ${DW_MEMO_SUCCESSOR_IMAGE:-durable-workflow/server-memo-rolling:local}
     ports: !override []
     environment:
       <<: *runtime-environment
-      APP_VERSION: ${APP_VERSION:-2.2.0}
+      APP_VERSION: ${APP_VERSION:-2.2.1}
       DW_SERVER_ID: memo-successor
       DW_SERVER_TOPOLOGY_SHAPE: standalone_server
       DW_SERVER_PROCESS_CLASS: server_http_node
diff --git a/docker-compose.published.yml b/docker-compose.published.yml
index c920149b..7a5f924a 100644
--- a/docker-compose.published.yml
+++ b/docker-compose.published.yml
@@ -1,13 +1,13 @@
 name: durable-workflow-server
 
 # Generated by scripts/ci/sync-source-release.mjs. Do not edit the fallback.
-x-server-image: &server-image ${DW_SERVER_IMAGE:-durableworkflow/server:${DW_SERVER_TAG:-2.2.0}}
+x-server-image: &server-image ${DW_SERVER_IMAGE:-durableworkflow/server:${DW_SERVER_TAG:-2.2.1}}
 
 x-server-environment: &server-environment
   APP_NAME: "Durable Workflow Server"
   APP_ENV: ${APP_ENV:-local}
   DW_SERVER_KEY: ${DW_SERVER_KEY:-}
-  APP_VERSION: ${APP_VERSION:-${DW_SERVER_TAG:-2.2.0}}
+  APP_VERSION: ${APP_VERSION:-${DW_SERVER_TAG:-2.2.1}}
   APP_DEBUG: ${APP_DEBUG:-false}
   LOG_CHANNEL: ${LOG_CHANNEL:-stderr}
   LOG_LEVEL: ${LOG_LEVEL:-info}
diff --git a/docker-compose.small-cluster.yml b/docker-compose.small-cluster.yml
index 52b496c0..b9265a9a 100644
--- a/docker-compose.small-cluster.yml
+++ b/docker-compose.small-cluster.yml
@@ -12,7 +12,7 @@ x-server-build: &server-build
 x-server-environment: &server-environment
   APP_NAME: "Durable Workflow Server"
   APP_ENV: testing
-  APP_VERSION: ${APP_VERSION:-2.2.0}
+  APP_VERSION: ${APP_VERSION:-2.2.1}
   APP_DEBUG: "false"
   DW_SERVER_KEY: ${DW_SERVER_KEY:-base64:5Zt4nUhlCm3DD0nLXZJQdHiwPfb56yGo9gNV/g3jYbY=}
   DB_CONNECTION: ${DW_SMALL_CLUSTER_DB:-mysql}
diff --git a/docker-compose.yml b/docker-compose.yml
index f281e0a5..180a187c 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -15,7 +15,7 @@ services:
       DW_SERVER_KEY: "${DW_SERVER_KEY:-}"
       DW_SERVER_TOPOLOGY_SHAPE: standalone_server
       DW_SERVER_PROCESS_CLASS: server_http_node
-      APP_VERSION: "${APP_VERSION:-2.2.0}"
+      APP_VERSION: "${APP_VERSION:-2.2.1}"
       APP_DEBUG: "false"
       DB_CONNECTION: mysql
       DB_HOST: mysql
@@ -62,7 +62,7 @@ services:
       APP_NAME: "Durable Workflow Server"
       APP_ENV: local
       DW_SERVER_KEY: "${DW_SERVER_KEY:-}"
-      APP_VERSION: "${APP_VERSION:-2.2.0}"
+      APP_VERSION: "${APP_VERSION:-2.2.1}"
       APP_DEBUG: "false"
       DB_CONNECTION: mysql
       DB_HOST: mysql
@@ -123,7 +123,7 @@ services:
       DW_SERVER_KEY: "${DW_SERVER_KEY:-}"
       DW_SERVER_TOPOLOGY_SHAPE: standalone_server
       DW_SERVER_PROCESS_CLASS: worker_node
-      APP_VERSION: "${APP_VERSION:-2.2.0}"
+      APP_VERSION: "${APP_VERSION:-2.2.1}"
       DB_CONNECTION: mysql
       DB_HOST: mysql
       DB_PORT: 3306
@@ -176,7 +176,7 @@ services:
       DW_SERVER_KEY: "${DW_SERVER_KEY:-}"
       DW_SERVER_TOPOLOGY_SHAPE: standalone_server
       DW_SERVER_PROCESS_CLASS: scheduler_node
-      APP_VERSION: "${APP_VERSION:-2.2.0}"
+      APP_VERSION: "${APP_VERSION:-2.2.1}"
       DB_CONNECTION: mysql
       DB_HOST: mysql
       DB_PORT: 3306
diff --git a/k8s/README.md b/k8s/README.md
index 6f0ef60c..70c12d19 100644
--- a/k8s/README.md
+++ b/k8s/README.md
@@ -13,7 +13,7 @@ The checked-in manifests are synchronized with the repository's stable source
 release and pin its Docker Hub tag:
 
 ```text
-durableworkflow/server:2.2.0
+durableworkflow/server:2.2.1
 ```
 
 Before production use, patch every workload image to the exact published tag or
@@ -21,15 +21,15 @@ digest you intend to run:
 
 ```bash
 kubectl set image -n durable-workflow deploy/durable-workflow-server \
-  server=durableworkflow/server:2.2.0
+  server=durableworkflow/server:2.2.1
 kubectl set image -n durable-workflow deploy/durable-workflow-worker \
-  worker=durableworkflow/server:2.2.0
+  worker=durableworkflow/server:2.2.1
 kubectl set image -n durable-workflow cronjob/durable-workflow-scheduler \
-  scheduler=durableworkflow/server:2.2.0
+  scheduler=durableworkflow/server:2.2.1
 ```
 
 GitHub Container Registry publishes the same release line at
-`ghcr.io/durable-workflow/server:2.2.0`. Digest pinning is preferred for strict
+`ghcr.io/durable-workflow/server:2.2.1`. Digest pinning is preferred for strict
 change control.
 
 The manifests expect you to provide:
diff --git a/k8s/helm/durable-workflow/Chart.yaml b/k8s/helm/durable-workflow/Chart.yaml
index c6487425..da98083c 100644
--- a/k8s/helm/durable-workflow/Chart.yaml
+++ b/k8s/helm/durable-workflow/Chart.yaml
@@ -5,11 +5,11 @@ type: application
 # The chart's own semver version. Bumped on every chart release; treated as
 # independent of the server image version (appVersion). Breaking-change rules
 # for this version live in docs/helm-upgrading.md alongside the chart.
-version: 0.1.77
+version: 0.1.78
 # The immutable Durable Workflow Server identity this chart release packages.
 # The onboarding default in values.yaml and appVersion are generated from the
 # checked-in source release record.
-appVersion: "2.2.0"
+appVersion: "2.2.1"
 kubeVersion: ">=1.27.0-0"
 home: https://durable-workflow.github.io/docs/2.0/deployment
 sources:
@@ -30,7 +30,7 @@ annotations:
   # exact commit that most recently changed the packaged chart.
   org.opencontainers.image.source: https://github.com/durable-workflow/server
   dev.durable-workflow.source-revision: "unreleased"
-  dev.durable-workflow.image-reference: "docker.io/durableworkflow/server:2.2.0"
+  dev.durable-workflow.image-reference: "docker.io/durableworkflow/server:2.2.1"
   artifacthub.io/license: MIT
   artifacthub.io/category: integration-delivery
   # Free-form changelog for the current chart release shown by Artifact Hub.
diff --git a/k8s/helm/durable-workflow/README.md b/k8s/helm/durable-workflow/README.md
index d6f6545d..c857760e 100644
--- a/k8s/helm/durable-workflow/README.md
+++ b/k8s/helm/durable-workflow/README.md
@@ -63,7 +63,7 @@ helm install durable-workflow ./k8s/helm/durable-workflow \
 
 ```yaml
 image:
-  tag: "2.2.0"
+  tag: "2.2.1"
   # Pin a digest in production:
   # digest: "sha256:abc123..."
   # memoPayloadStorage: "raw-json-v1" # Required for a digest or custom image.
diff --git a/k8s/helm/durable-workflow/ci/existing-secrets-values.yaml b/k8s/helm/durable-workflow/ci/existing-secrets-values.yaml
index 5d5f03c5..c54ecfde 100644
--- a/k8s/helm/durable-workflow/ci/existing-secrets-values.yaml
+++ b/k8s/helm/durable-workflow/ci/existing-secrets-values.yaml
@@ -1,7 +1,7 @@
 # CI fixture: GitOps / externally-managed-secret path. The chart consumes
 # existing Secrets and renders no Secret resources of its own.
 image:
-  tag: "2.2.0"
+  tag: "2.2.1"
 
 externalDatabase:
   connection: pgsql
diff --git a/k8s/helm/durable-workflow/ci/ingress-and-hpa-values.yaml b/k8s/helm/durable-workflow/ci/ingress-and-hpa-values.yaml
index 7366fac3..b6064ff5 100644
--- a/k8s/helm/durable-workflow/ci/ingress-and-hpa-values.yaml
+++ b/k8s/helm/durable-workflow/ci/ingress-and-hpa-values.yaml
@@ -1,6 +1,6 @@
 # CI fixture: ingress + autoscaling enabled. Exercises optional templates.
 image:
-  tag: "2.2.0"
+  tag: "2.2.1"
 
 externalDatabase:
   connection: mysql
diff --git a/k8s/helm/durable-workflow/ci/inline-secrets-values.yaml b/k8s/helm/durable-workflow/ci/inline-secrets-values.yaml
index 6d13a9be..ad403c2c 100644
--- a/k8s/helm/durable-workflow/ci/inline-secrets-values.yaml
+++ b/k8s/helm/durable-workflow/ci/inline-secrets-values.yaml
@@ -2,7 +2,7 @@
 # chart's render path is exercised end-to-end. Real deployments should use
 # existingSecret instead.
 image:
-  tag: "2.2.0"
+  tag: "2.2.1"
 
 externalDatabase:
   connection: mysql
diff --git a/k8s/helm/durable-workflow/templates/_helpers.tpl b/k8s/helm/durable-workflow/templates/_helpers.tpl
index 1516e526..c624de0e 100644
--- a/k8s/helm/durable-workflow/templates/_helpers.tpl
+++ b/k8s/helm/durable-workflow/templates/_helpers.tpl
@@ -88,7 +88,7 @@ resolved by an explicit capability declaration or an existing workload marker.
 {{- define "durable-workflow.memoPayloadStorageForImage" -}}
 {{- $image := toString . -}}
 {{- $normalized := regexReplaceAll "^index\\.docker\\.io/" $image "docker.io/" -}}
-{{- if eq $normalized "docker.io/durableworkflow/server:2.2.0" -}}
+{{- if eq $normalized "docker.io/durableworkflow/server:2.2.1" -}}
 dual-v1
 {{- else if regexMatch "^docker\\.io/durableworkflow/server:2\\.0\\.0-rc\\.[0-9]+$" $normalized -}}
 {{- $releaseCandidate := atoi (regexFind "[0-9]+$" $normalized) -}}
diff --git a/k8s/helm/durable-workflow/values.yaml b/k8s/helm/durable-workflow/values.yaml
index b55c15dc..22d167de 100644
--- a/k8s/helm/durable-workflow/values.yaml
+++ b/k8s/helm/durable-workflow/values.yaml
@@ -21,7 +21,7 @@ image:
   registry: docker.io
   repository: durableworkflow/server
   # Generated by scripts/ci/sync-source-release.mjs. Do not edit this default.
-  tag: "2.2.0"
+  tag: "2.2.1"
   # Optional digest pin. When set, takes precedence over tag for change control.
   # Example: "sha256:abc123..."
   digest: ""
diff --git a/k8s/helm/examples/values-dev.yaml b/k8s/helm/examples/values-dev.yaml
index ac1f6439..5b3cfbd5 100644
--- a/k8s/helm/examples/values-dev.yaml
+++ b/k8s/helm/examples/values-dev.yaml
@@ -3,7 +3,7 @@
 # shape in production.
 
 image:
-  tag: "2.2.0"
+  tag: "2.2.1"
 
 externalDatabase:
   connection: mysql
diff --git a/k8s/helm/examples/values-external-secrets-operator.yaml b/k8s/helm/examples/values-external-secrets-operator.yaml
index f9ec5beb..24d852e9 100644
--- a/k8s/helm/examples/values-external-secrets-operator.yaml
+++ b/k8s/helm/examples/values-external-secrets-operator.yaml
@@ -5,7 +5,7 @@
 # concern.
 
 image:
-  tag: "2.2.0"
+  tag: "2.2.1"
 
 externalDatabase:
   connection: pgsql
diff --git a/k8s/helm/examples/values-production-existing-secrets.yaml b/k8s/helm/examples/values-production-existing-secrets.yaml
index 06936248..946ed456 100644
--- a/k8s/helm/examples/values-production-existing-secrets.yaml
+++ b/k8s/helm/examples/values-production-existing-secrets.yaml
@@ -10,7 +10,7 @@ image:
   repository: durable-workflow/server
   # Pin a digest in production for change-control auditability.
   digest: ""    # e.g. "sha256:abc123..."
-  tag: "2.2.0"
+  tag: "2.2.1"
 
 externalDatabase:
   connection: pgsql
diff --git a/k8s/migration-job.yaml b/k8s/migration-job.yaml
index 868ffa8a..b7dc0088 100644
--- a/k8s/migration-job.yaml
+++ b/k8s/migration-job.yaml
@@ -13,7 +13,7 @@ spec:
       restartPolicy: OnFailure
       containers:
         - name: migrate
-          image: durableworkflow/server:2.2.0
+          image: durableworkflow/server:2.2.1
           command: ["server-entrypoint"]
           args: ["server-bootstrap"]
           envFrom:
diff --git a/k8s/scheduler-cronjob.yaml b/k8s/scheduler-cronjob.yaml
index 91b9fa61..1bcd6a6a 100644
--- a/k8s/scheduler-cronjob.yaml
+++ b/k8s/scheduler-cronjob.yaml
@@ -24,7 +24,7 @@ spec:
           restartPolicy: Never
           containers:
             - name: scheduler
-              image: durableworkflow/server:2.2.0
+              image: durableworkflow/server:2.2.1
               command: ["server-entrypoint"]
               args: ["sh", "-c", "php artisan schedule:evaluate --limit=100 --json; php artisan activity:timeout-enforce --limit=100; if php artisan list --raw | grep -q '^external-payloads:cleanup '; then php artisan external-payloads:cleanup --limit=100 --json; fi; php artisan history:prune --limit=100"]
               envFrom:
diff --git a/k8s/secret.yaml b/k8s/secret.yaml
index 96287437..1f54411e 100644
--- a/k8s/secret.yaml
+++ b/k8s/secret.yaml
@@ -12,7 +12,7 @@ metadata:
     app.kubernetes.io/name: durable-workflow
 data:
   APP_NAME: "Durable Workflow Server"
-  APP_VERSION: "2.2.0"
+  APP_VERSION: "2.2.1"
   APP_ENV: production
   APP_DEBUG: "false"
   DB_CONNECTION: mysql
diff --git a/k8s/server-deployment.yaml b/k8s/server-deployment.yaml
index 9ba93f9c..4e2cf0d4 100644
--- a/k8s/server-deployment.yaml
+++ b/k8s/server-deployment.yaml
@@ -23,7 +23,7 @@ spec:
     spec:
       containers:
         - name: server
-          image: durableworkflow/server:2.2.0
+          image: durableworkflow/server:2.2.1
           ports:
             - containerPort: 8080
               name: http
diff --git a/k8s/worker-deployment.yaml b/k8s/worker-deployment.yaml
index 0e147211..1c08961f 100644
--- a/k8s/worker-deployment.yaml
+++ b/k8s/worker-deployment.yaml
@@ -19,7 +19,7 @@ spec:
     spec:
       containers:
         - name: worker
-          image: durableworkflow/server:2.2.0
+          image: durableworkflow/server:2.2.1
           command: ["server-entrypoint"]
           args: ["php", "artisan", "queue:work", "--sleep=1", "--tries=3", "--max-time=3600"]
           envFrom:
diff --git a/resources/platform-protocol-specs/worker-protocol-api.openapi.yaml b/resources/platform-protocol-specs/worker-protocol-api.openapi.yaml
index 7d1e2784..dbf5d409 100644
--- a/resources/platform-protocol-specs/worker-protocol-api.openapi.yaml
+++ b/resources/platform-protocol-specs/worker-protocol-api.openapi.yaml
@@ -1,7 +1,7 @@
 openapi: 3.1.0
 info:
   title: durable-workflow.v2.worker-protocol-api
-  version: "18"
+  version: "19"
   summary: Durable Workflow worker-plane HTTP+JSON API
   description: >
     Normative OpenAPI specification for the worker-plane HTTP+JSON API:
@@ -208,6 +208,7 @@ paths:
         "400": { $ref: "#/components/responses/WorkerError" }
         "409": { $ref: "#/components/responses/WorkerRegistrationFailure" }
         "422": { $ref: "#/components/responses/WorkerError" }
+        "503": { $ref: "#/components/responses/WorkerServiceUnavailable" }
   /worker/registrations/{workerId}:
     delete:
       operationId: deregisterWorker
@@ -242,6 +243,7 @@ paths:
       responses:
         "200": { $ref: "#/components/responses/WorkerEnvelope" }
         "404": { $ref: "#/components/responses/WorkerError" }
+        "503": { $ref: "#/components/responses/WorkerServiceUnavailable" }
   /worker/sessions:
     post:
       operationId: createWorkerSession
@@ -312,6 +314,7 @@ paths:
         "429": { $ref: "#/components/responses/WorkerPollBackpressure" }
         "409": { $ref: "#/components/responses/WorkflowTaskPollConflict" }
         "422": { $ref: "#/components/responses/WorkerError" }
+        "503": { $ref: "#/components/responses/WorkerServiceUnavailable" }
   /worker/workflow-tasks/{taskId}/history:
     post:
       operationId: getWorkflowTaskHistoryPage
@@ -399,6 +402,7 @@ paths:
         "409": { $ref: "#/components/responses/WorkerError" }
         "429": { $ref: "#/components/responses/WorkerPollBackpressure" }
         "422": { $ref: "#/components/responses/WorkerError" }
+        "503": { $ref: "#/components/responses/WorkerServiceUnavailable" }
   /worker/update-validation-tasks/{taskId}/approve:
     post:
       operationId: approveUpdateValidationTask
@@ -446,6 +450,7 @@ paths:
       responses:
         "200": { $ref: "#/components/responses/WorkerEnvelope" }
         "429": { $ref: "#/components/responses/WorkerPollBackpressure" }
+        "503": { $ref: "#/components/responses/WorkerServiceUnavailable" }
   /worker/query-tasks/{queryTaskId}/complete:
     post:
       operationId: completeQueryTask
@@ -504,6 +509,7 @@ paths:
                   - $ref: "#/components/schemas/EmptyPoll"
                   - $ref: "#/components/schemas/DrainingPoll"
         "429": { $ref: "#/components/responses/WorkerPollBackpressure" }
+        "503": { $ref: "#/components/responses/WorkerServiceUnavailable" }
   /worker/activity-tasks/{taskId}/heartbeat:
     post:
       operationId: heartbeatActivityTask
@@ -598,6 +604,25 @@ components:
       content:
         application/json:
           schema: { $ref: "#/components/schemas/WorkerError" }
+    WorkerServiceUnavailable:
+      description: >
+        Temporary database connection loss returns backend_unavailable with an
+        unknown operation outcome. Retry with bounded backoff and the identical
+        worker, queue and poll_request_id; task=null does not prove that no task
+        was claimed. Registration and heartbeat likewise do not acknowledge or
+        reject an operation whose result is unknown. Other 503 errors retain
+        their own contracts and are not automatically retryable.
+      headers:
+        X-Durable-Workflow-Protocol-Version:
+          schema: { $ref: "#/components/schemas/AdvertisedWorkerProtocolVersion" }
+        Retry-After:
+          schema: { type: integer, minimum: 1 }
+      content:
+        application/json:
+          schema:
+            anyOf:
+              - $ref: "#/components/schemas/WorkerBackendUnavailable"
+              - $ref: "#/components/schemas/WorkerError"
     WorkerPollBackpressure:
       description: The node has no capacity for another held long poll; retry after the advertised delay.
       headers:
@@ -736,6 +761,31 @@ components:
         reason: { type: [string, "null"] }
         remediation: { type: [string, "null"] }
         server_capabilities: { $ref: "#/components/schemas/WorkerServerCapabilities" }
+    WorkerBackendUnavailable:
+      allOf:
+        - $ref: "#/components/schemas/WorkerError"
+        - type: object
+          required: [reason, operation, outcome, worker_id, task_queue, retryable, retry_after_seconds]
+          properties:
+            reason: { type: string, const: backend_unavailable }
+            operation:
+              type: string
+              enum: [register_worker, heartbeat_worker, poll_workflow_task, poll_activity_task, poll_query_task, poll_update_validation_task]
+            outcome: { type: string, const: unknown }
+            worker_id: { type: [string, "null"], minLength: 1, maxLength: 255 }
+            task_queue: { type: [string, "null"], minLength: 1, maxLength: 255 }
+            retryable: { type: boolean }
+            retry_after_seconds: { type: integer, minimum: 1 }
+          if:
+            properties:
+              operation: { enum: [poll_workflow_task, poll_activity_task, poll_query_task, poll_update_validation_task] }
+          then:
+            required: [task, poll_status, poll_request_id, retry_same_poll_request_id]
+            properties:
+              task: { type: "null" }
+              poll_status: { type: string, const: backend_unavailable }
+              poll_request_id: { type: [string, "null"], minLength: 1, maxLength: 255 }
+              retry_same_poll_request_id: { type: boolean, const: true }
     WorkerPollBackpressure:
       allOf:
         - $ref: "#/components/schemas/WorkerError"
diff --git a/resources/release/source-release.json b/resources/release/source-release.json
index ea02bfa2..761722c0 100644
--- a/resources/release/source-release.json
+++ b/resources/release/source-release.json
@@ -1,9 +1,9 @@
 {
   "schema": "durable-workflow.server.source-release/v1",
   "server": {
-    "version": "2.2.0"
+    "version": "2.2.1"
   },
   "helm_chart": {
-    "version": "0.1.77"
+    "version": "0.1.78"
   }
 }
diff --git a/scripts/k8s-kind-smoke.sh b/scripts/k8s-kind-smoke.sh
index 95184d68..3f846aa5 100755
--- a/scripts/k8s-kind-smoke.sh
+++ b/scripts/k8s-kind-smoke.sh
@@ -7,7 +7,7 @@ cluster="${K8S_SMOKE_CLUSTER:-durable-workflow-server-smoke}"
 image="${K8S_SMOKE_IMAGE:-durableworkflow/server:k8s-smoke}"
 # Generated by scripts/ci/sync-source-release.mjs so the smoke replaces the
 # same default shipped by the public manifests.
-manifest_image="durableworkflow/server:2.2.0"
+manifest_image="durableworkflow/server:2.2.1"
 kind_node_image="${K8S_SMOKE_KIND_NODE_IMAGE:-kindest/node:v1.29.4}"
 artifact_dir="${K8S_SMOKE_ARTIFACT_DIR:-/tmp/durable-workflow-k8s-kind-smoke-artifacts}"
 rendered_dir="${artifact_dir}/rendered-manifests"
diff --git a/tests/Feature/WorkerDatabaseUnavailableTest.php b/tests/Feature/WorkerDatabaseUnavailableTest.php
new file mode 100644
index 00000000..8a5b2a70
--- /dev/null
+++ b/tests/Feature/WorkerDatabaseUnavailableTest.php
@@ -0,0 +1,191 @@
+<?php
+
+namespace Tests\Feature;
+
+use App\Models\RuntimeCredential;
+use App\Models\WorkerRegistration;
+use App\Support\WorkerProtocol;
+use Illuminate\Database\Connection;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+use Illuminate\Support\Facades\DB;
+use Mockery;
+use PDOException;
+use PHPUnit\Framework\Attributes\DataProvider;
+use Tests\Feature\Concerns\ServerTestHelpers;
+use Tests\Support\OpenApiSchema;
+use Tests\TestCase;
+
+class WorkerDatabaseUnavailableTest extends TestCase
+{
+    use RefreshDatabase;
+    use ServerTestHelpers;
+
+    private bool $databaseUnavailable = false;
+
+    private string $failureQuery = 'workflow_worker_registrations';
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+        $this->createNamespace('default');
+        $this->registerWorker(workerId: 'database-worker', taskQueue: 'database-queue',
+            supportedWorkflowTypes: ['ExampleWorkflow'], supportedActivityTypes: ['ExampleActivity']);
+
+        DB::connection()->beforeExecuting(function (string $query): void {
+            if ($this->databaseUnavailable && str_contains($query, $this->failureQuery)) {
+                $exception = new PDOException('SQLSTATE[HY000] [2002] Connection refused');
+                $exception->errorInfo = ['HY000', 2002, 'private database connection refused'];
+                throw $exception;
+            }
+        });
+    }
+
+    #[DataProvider('pollPaths')]
+    public function test_database_loss_preserves_the_logical_poll_identity(string $path): void
+    {
+        $this->databaseUnavailable = true;
+        $response = $this->postJson($path, [
+            'worker_id' => 'database-worker', 'task_queue' => 'database-queue',
+            'poll_request_id' => 'same-logical-poll', 'timeout_seconds' => 0,
+        ], $this->workerHeaders());
+
+        $response->assertStatus(503)->assertHeader(WorkerProtocol::HEADER, WorkerProtocol::VERSION)
+            ->assertHeader('Retry-After', '1')->assertJsonPath('reason', 'backend_unavailable')
+            ->assertJsonPath('poll_status', 'backend_unavailable')->assertJsonPath('task', null)
+            ->assertJsonPath('outcome', 'unknown')->assertJsonPath('retryable', true)
+            ->assertJsonPath('poll_request_id', 'same-logical-poll')
+            ->assertJsonPath('retry_same_poll_request_id', true);
+        $this->assertStringNotContainsString('private database', $response->getContent());
+        $this->assertStringNotContainsString('SQLSTATE', $response->getContent());
+        OpenApiSchema::fromFile(base_path('resources/platform-protocol-specs/worker-protocol-api.openapi.yaml'))
+            ->assertReferenceMatches('#/components/schemas/WorkerBackendUnavailable', json_decode($response->getContent()));
+
+        $this->databaseUnavailable = false;
+        $this->assertSame(1, WorkerRegistration::query()->where('worker_id', 'database-worker')->count());
+    }
+
+    public static function pollPaths(): array
+    {
+        return [
+            ['/api/worker/workflow-tasks/poll'],
+            ['/api/worker/activity-tasks/poll'],
+            ['/api/worker/query-tasks/poll'],
+            ['/api/worker/update-validation-tasks/poll'],
+        ];
+    }
+
+    public function test_worker_heartbeat_does_not_claim_an_acknowledgement_during_database_loss(): void
+    {
+        $this->databaseUnavailable = true;
+        $this->postJson('/api/worker/heartbeat', ['worker_id' => 'database-worker'], $this->workerHeaders())
+            ->assertStatus(503)->assertJsonPath('reason', 'backend_unavailable')
+            ->assertJsonPath('operation', 'heartbeat_worker')->assertJsonPath('worker_id', 'database-worker')
+            ->assertJsonPath('retryable', true)->assertJsonPath('outcome', 'unknown')
+            ->assertJsonMissingPath('acknowledged');
+    }
+
+    public function test_connection_loss_in_a_bootstrap_query_keeps_the_retry_contract(): void
+    {
+        $this->failureQuery = 'migrations';
+        $this->databaseUnavailable = true;
+
+        $this->postJson('/api/worker/workflow-tasks/poll', [
+            'worker_id' => 'database-worker', 'task_queue' => 'database-queue',
+            'poll_request_id' => 'same-logical-poll', 'timeout_seconds' => 0,
+        ], $this->workerHeaders())->assertStatus(503)
+            ->assertJsonPath('reason', 'backend_unavailable')
+            ->assertJsonPath('poll_request_id', 'same-logical-poll');
+    }
+
+    public function test_invalid_authentication_remains_unauthorized_during_database_loss(): void
+    {
+        config(['server.auth.driver' => 'token', 'server.auth.token' => 'test-secret-token']);
+        $this->databaseUnavailable = true;
+
+        $this->postJson('/api/worker/workflow-tasks/poll', [
+            'worker_id' => 'database-worker', 'task_queue' => 'database-queue',
+            'poll_request_id' => 'same-logical-poll', 'timeout_seconds' => 0,
+        ], $this->workerHeaders() + ['Authorization' => 'Bearer invalid-token'])
+            ->assertStatus(401)->assertJsonMissingPath('retryable');
+    }
+
+    public function test_runtime_credential_lookup_loss_retries_without_authenticating_the_request(): void
+    {
+        $token = 'disposable-worker-token';
+        RuntimeCredential::query()->create([
+            'id' => 'outage-worker', 'subject' => 'test-worker', 'roles' => ['worker'],
+            'tenant' => 'default', 'token_prefix' => RuntimeCredential::prefixFor($token),
+            'token_hash' => RuntimeCredential::hashToken($token),
+        ]);
+        config([
+            'server.auth.driver' => 'token', 'server.auth.token' => null,
+            'server.auth.runtime_credentials.enabled' => true,
+        ]);
+        $this->failureQuery = 'runtime_credentials';
+        $this->databaseUnavailable = true;
+        $request = ['worker_id' => 'database-worker'];
+        $headers = $this->workerHeaders() + ['Authorization' => 'Bearer '.$token];
+        $originalHeartbeat = WorkerRegistration::query()->firstOrFail()->last_heartbeat_at;
+
+        $this->postJson('/api/worker/heartbeat', $request, $headers)
+            ->assertStatus(503)->assertJsonPath('reason', 'backend_unavailable')
+            ->assertJsonPath('outcome', 'unknown')->assertJsonMissingPath('acknowledged');
+        $this->assertTrue($originalHeartbeat->equalTo(WorkerRegistration::query()->firstOrFail()->last_heartbeat_at));
+
+        $this->databaseUnavailable = false;
+        $this->postJson('/api/worker/heartbeat', $request, $headers)->assertOk();
+        $this->postJson('/api/worker/heartbeat', $request,
+            $this->workerHeaders() + ['Authorization' => 'Bearer invalid-token'])
+            ->assertStatus(401)->assertJsonMissingPath('retryable');
+    }
+
+    public function test_registration_outcome_is_unknown_not_falsely_rejected(): void
+    {
+        $this->databaseUnavailable = true;
+        $this->postJson('/api/worker/register', [
+            'worker_id' => 'database-worker', 'task_queue' => 'database-queue', 'runtime' => 'php',
+            'capability_manifest' => $this->portableWorkerAffinityRefusalManifest(),
+        ], $this->workerHeaders())
+            ->assertStatus(503)->assertJsonPath('reason', 'backend_unavailable')
+            ->assertJsonPath('operation', 'register_worker')->assertJsonPath('worker_id', 'database-worker')
+            ->assertJsonPath('retryable', true)->assertJsonPath('outcome', 'unknown')
+            ->assertJsonMissingPath('registered');
+    }
+
+    #[DataProvider('bootstrapErrors')]
+    public function test_bootstrap_admission_distinguishes_connection_loss_from_configuration_failure(int $code, string $reason): void
+    {
+        $exception = new PDOException('private database diagnostic');
+        $exception->errorInfo = ['HY000', $code, 'private database diagnostic'];
+        $connection = Mockery::mock(Connection::class);
+        $connection->shouldReceive('getPdo')->andThrow($exception);
+        $manager = DB::getFacadeRoot();
+        DB::shouldReceive('connection')->andReturn($connection);
+
+        try {
+            $response = $this->postJson('/api/worker/workflow-tasks/poll', [
+                'worker_id' => 'database-worker', 'task_queue' => 'database-queue',
+                'poll_request_id' => 'bootstrap-poll', 'timeout_seconds' => 0,
+            ], $this->workerHeaders());
+            $response->assertStatus(503)->assertJsonPath('reason', $reason);
+            $this->assertStringNotContainsString('private database', $response->getContent());
+            if ($reason === 'backend_unavailable') {
+                $response->assertJsonPath('poll_request_id', 'bootstrap-poll')
+                    ->assertJsonPath('retry_same_poll_request_id', true);
+            } else {
+                $response->assertJsonMissingPath('retryable');
+            }
+        } finally {
+            DB::swap($manager);
+        }
+    }
+
+    public static function bootstrapErrors(): array
+    {
+        return [
+            [2002, 'backend_unavailable'],
+            [1045, 'workflow_v2_blocked'],
+            [1049, 'workflow_v2_blocked'],
+        ];
+    }
+}
diff --git a/tests/Unit/BackendUnavailableTest.php b/tests/Unit/BackendUnavailableTest.php
new file mode 100644
index 00000000..38c7c4eb
--- /dev/null
+++ b/tests/Unit/BackendUnavailableTest.php
@@ -0,0 +1,51 @@
+<?php
+
+namespace Tests\Unit;
+
+use App\Support\BackendUnavailable;
+use Illuminate\Database\QueryException;
+use PDOException;
+use PHPUnit\Framework\Attributes\DataProvider;
+use PHPUnit\Framework\TestCase;
+use RuntimeException;
+
+class BackendUnavailableTest extends TestCase
+{
+    #[DataProvider('driverErrors')]
+    public function test_only_recognized_connection_failures_are_retryable(string $state, int $code, bool $retryable): void
+    {
+        $exception = new PDOException('arbitrary database error text');
+        $exception->errorInfo = [$state, $code, 'diagnostic'];
+
+        $this->assertSame($retryable, BackendUnavailable::is($exception));
+        $this->assertSame($retryable, BackendUnavailable::is(new QueryException('mysql', 'select ?', ['value'], $exception)));
+    }
+
+    public static function driverErrors(): array
+    {
+        return [
+            'mysql refused' => ['HY000', 2002, true],
+            'mysql host unavailable' => ['HY000', 2003, true],
+            'mysql gone away' => ['HY000', 2006, true],
+            'mysql connection lost' => ['HY000', 2013, true],
+            'mysql extended connection lost' => ['HY000', 2055, true],
+            'postgres shutdown' => ['57P01', 7, true],
+            'postgres recovery' => ['57P03', 7, true],
+            'connection failure' => ['08006', 7, true],
+            'unknown transaction result' => ['08007', 7, true],
+            'access denied' => ['HY000', 1045, false],
+            'missing database' => ['HY000', 1049, false],
+            'disk full' => ['HY000', 1114, false],
+            'deadlock' => ['40001', 1213, false],
+            'schema error' => ['42S02', 1146, false],
+            'unique violation' => ['23000', 1062, false],
+            'wrong sqlstate' => ['42000', 2002, false],
+        ];
+    }
+
+    public function test_error_text_cannot_classify_a_failure(): void
+    {
+        $this->assertFalse(BackendUnavailable::is(new RuntimeException('SQLSTATE[HY000] [2002] Connection refused')));
+        $this->assertFalse(BackendUnavailable::is(new PDOException('SQLSTATE[HY000] [2002] Connection refused')));
+    }
+}
diff --git a/tests/Unit/WorkerProtocolOpenApiContractTest.php b/tests/Unit/WorkerProtocolOpenApiContractTest.php
index d3b5dda2..3298f1ef 100644
--- a/tests/Unit/WorkerProtocolOpenApiContractTest.php
+++ b/tests/Unit/WorkerProtocolOpenApiContractTest.php
@@ -96,6 +96,18 @@ public function test_worker_poll_routes_publish_typed_backpressure(): void
         );
     }
 
+    public function test_worker_lifecycle_and_poll_routes_describe_unknown_database_outcomes(): void
+    {
+        foreach (['register', 'heartbeat', 'workflow-tasks/poll', 'activity-tasks/poll', 'query-tasks/poll', 'update-validation-tasks/poll'] as $path) {
+            $this->assertSame('#/components/responses/WorkerServiceUnavailable',
+                $this->spec['paths']['/worker/'.$path]['post']['responses']['503']['$ref'] ?? null);
+        }
+        $contract = $this->spec['components']['schemas']['WorkerBackendUnavailable']['allOf'][1];
+        $this->assertSame('unknown', $contract['properties']['outcome']['const']);
+        $this->assertContains('poll_request_id', $contract['then']['required']);
+        $this->assertSame(true, $contract['then']['properties']['retry_same_poll_request_id']['const']);
+    }
+
     public function test_portable_worker_affinity_is_machine_described_at_protocol_1_18(): void
     {
         $contract = $this->spec['x-durable-workflow-portable-worker-affinity-contract'];