diff --git a/scripts/src/platform-infra-pac-provenance.test.ts b/scripts/src/platform-infra-pac-provenance.test.ts
index 381623b2..3b3a54be 100644
--- a/scripts/src/platform-infra-pac-provenance.test.ts
+++ b/scripts/src/platform-infra-pac-provenance.test.ts
@@ -88,10 +88,15 @@ test("versioned admission desired state protects controller proof, candidate ide
   const oldRun = { spec: { pipelineSpec: { tasks: [{ name: "plan-artifacts" }] }, workspaces: [], timeouts: { pipeline: "1h" } } };
   const mutatedRun = structuredClone(oldRun);
   mutatedRun.spec.pipelineSpec.tasks[0].name = "forged-task";
-  for (const field of ["managedBy", "params", "pipelineRef", "pipelineSpec", "taskRunSpecs", "taskRunTemplate", "timeouts", "workspaces"]) {
+  for (const field of ["managedBy", "params", "pipelineRef", "taskRunSpecs", "taskRunTemplate", "timeouts", "workspaces"]) {
     expect(specGuard.expression).toContain(`has(object.spec.${field})`);
     expect(specGuard.expression).toContain(`object.spec.${field} == oldObject.spec.${field}`);
   }
+  expect(specGuard.expression).toContain("has(dyn(object.spec).pipelineSpec)");
+  expect(specGuard.expression).toContain("has(dyn(oldObject.spec).pipelineSpec)");
+  expect(specGuard.expression).toContain("dyn(object.spec).pipelineSpec == dyn(oldObject.spec).pipelineSpec");
+  expect(specGuard.expression).not.toContain("has(object.spec.pipelineSpec)");
+  expect(specGuard.expression).not.toContain("object.spec.pipelineSpec == oldObject.spec.pipelineSpec");
   expect(specGuard.expression).not.toContain("pipelinesascode.tekton.dev/state");
   expect(mutatedRun.spec).not.toEqual(oldRun.spec);
   expect(queueGuard.expression).toContain('request.userInfo.username == "system:serviceaccount:pipelines-as-code:pipelines-as-code-watcher"');
@@ -141,6 +146,21 @@ test("live admission evaluator requires exact desired hashes, observed generatio
   };
   const input = { policy, binding, role: rbac[0], roleBinding: rbac[1], namespace: "agentrun-ci", defaultCanMutate: false, expected };
   expect(evaluator.evaluatePacAdmissionState(input)).toMatchObject({ ready: true, activeAfter: "2026-01-01T00:00:01Z", defaultCanMutate: false });
+  expect(evaluator.evaluatePacAdmissionState({
+    ...input,
+    policy: {
+      ...policy,
+      status: {
+        ...policy.status,
+        typeChecking: {
+          expressionWarnings: [{
+            fieldRef: "spec.validations[7].expression",
+            warning: "undefined field 'pipelineSpec'",
+          }],
+        },
+      },
+    },
+  })).toMatchObject({ ready: false, reasons: expect.arrayContaining(["policy-expression-warning"]) });
   const apiDefaultedPolicy = {
     ...policy,
     spec: {
diff --git a/scripts/src/platform-infra-pac-provenance.ts b/scripts/src/platform-infra-pac-provenance.ts
index 94983b12..434bbb02 100644
--- a/scripts/src/platform-infra-pac-provenance.ts
+++ b/scripts/src/platform-infra-pac-provenance.ts
@@ -319,11 +319,19 @@ function pipelineRefEqual(): string {
 }
 
 function specFieldEqual(field: string): string {
+  if (field === "pipelineSpec") return schemalessSpecFieldEqual(field);
   const current = `has(object.spec.${field})`;
   const previous = `has(oldObject.spec.${field})`;
   return `((${current}) == (${previous}) && (!(${current}) || object.spec.${field} == oldObject.spec.${field}))`;
 }
 
+function schemalessSpecFieldEqual(field: string): string {
+  // Tekton pipelineSpec 保留未知字段且没有静态类型，必须在 dyn 根上检查存在性并做完整深度相等。
+  const current = `has(dyn(object.spec).${field})`;
+  const previous = `has(dyn(oldObject.spec).${field})`;
+  return `((${current}) == (${previous}) && (!(${current}) || dyn(object.spec).${field} == dyn(oldObject.spec).${field}))`;
+}
+
 function specStatusState(root: "object" | "oldObject", state: string): string {
   if (state === "absent") return `!has(${root}.spec.status)`;
   return `has(${root}.spec.status) && ${root}.spec.status == ${cel(state)}`;