Reuse verified immutable plans and streamline cooperative hashing

Continue final hosted development reliability qualification.

test/execution-world.test.ts

@@ -9,6 +9,9 @@ import {
   implementationDigest,
   clientContractCatalog,
   hexDigest,
+  executionPlanDigest,
+  executionPlanDigestAsync,
+  sealExecutionPlan,
   parsePackageArtifacts,
   artifactPath,
   type PackageArtifacts,
@@ -21,6 +24,54 @@ import { compileKernelProgram } from "../src/execution-world/kernel.js";
 import { loadCompositeWorkspace } from "./composite-fixture.js";
 import { standardNativeBackends } from "../src/execution-world/native-backends.js";
 
+test("sealed runtime plans reuse verified integrity while mutable copies are rechecked", async () => {
+  const workspace = await loadReaderWorkspace();
+  const compiled = compileExecutionPlan(workspace);
+  const plan: ExecutionPlan = JSON.parse(JSON.stringify(compiled));
+  assert.equal(await sealExecutionPlan(plan), true);
+  assert.equal(executionPlanDigest(plan), compiled.digest);
+  assert.equal(await executionPlanDigestAsync(plan), compiled.digest);
+  assert.throws(() => {
+    plan.definition.workspace.sourceRootCommit = "f".repeat(40);
+  }, TypeError);
+  assert.throws(() => {
+    plan.digest = "0".repeat(64);
+  }, TypeError);
+
+  const stringify = JSON.stringify;
+  JSON.stringify = () => {
+    throw Error("Repeated serialization of sealed metadata");
+  };
+  try {
+    assert.equal(executionPlanDigest(plan), compiled.digest);
+    assert.equal(await executionPlanDigestAsync(plan), compiled.digest);
+  } finally {
+    JSON.stringify = stringify;
+  }
+
+  const changed: ExecutionPlan = structuredClone(plan);
+  changed.definition.workspace.sourceRootCommit = "f".repeat(40);
+  Object.freeze(changed);
+  assert.notEqual(executionPlanDigest(changed), plan.digest);
+  assert.notEqual(await executionPlanDigestAsync(changed), plan.digest);
+  assert.equal(await sealExecutionPlan(changed), false, "shallow freezing is not an integrity proof");
+
+  const resigned: ExecutionPlan = structuredClone(plan);
+  resigned.definition.workspace.sourceRootCommit = "e".repeat(40);
+  resigned.digest = executionPlanDigest(resigned);
+  assert.equal(await sealExecutionPlan(resigned), true);
+  assert.notEqual(executionPlanDigest(resigned), plan.digest);
+  workspace.sourceRootCommit = "d".repeat(40);
+  assert.equal(workspace.sourceRootCommit, "d".repeat(40), "sealing owned JSON leaves compiler inputs editable");
+});
+
+test("runtime plan sealing rejects accessor-backed metadata", async () => {
+  const plan: ExecutionPlan = compileExecutionPlan(await loadReaderWorkspace());
+  assert.equal(await sealExecutionPlan(Object.create(plan)), false, "inherited integrity fields cannot be sealed");
+  Object.defineProperty(plan.definition, "codec", { get: () => "camino-execution-plan-v1", enumerable: true });
+  await assert.rejects(sealExecutionPlan(plan), /INVALID_PLAN_JSON/);
+});
+
 test("optional targets close over calls into another package", async () => {
   const workspace = await loadCompositeWorkspace();
   const before = compileExecutionPlan(workspace).definition.operations.find(