fix: register logical models in Pi children

docs/architecture.md

@@ -29,7 +29,7 @@ or resume, it belongs in Pi/pi-subagents or the provider layer rather than Forge
 
 ## Model policy boundary
 
-ForgeFlow registers stable logical roles as Pi virtual models. Their physical model mapping is read from operator policy rather than hard-coded into workflows or subagent definitions. New user/direct requests resolve the current mapping, while continuation/retry requests stay on the physical model already handling the turn to preserve prompt-cache and reasoning-signature continuity.
+ForgeFlow registers stable logical roles as Pi virtual models. Their physical model mapping is read from operator policy rather than hard-coded into workflows or subagent definitions. For native Pi children, the parent session registers a required child-only extension that installs only those virtual-model definitions before child model resolution; it does not duplicate ForgeFlow's prompt policy or workflow resources in the child. New user/direct requests resolve the current mapping, while continuation/retry requests stay on the physical model already handling the turn to preserve prompt-cache and reasoning-signature continuity.
 
 Project-local `.pi/forgeflow-models.json` is considered only when Pi reports the project trusted. User-level policy under `~/.pi/forgeflow-models.json` remains available for untrusted projects. `FORGEFLOW_MODEL_POLICY` is an explicit operator override.
 

docs/model-policy.md

@@ -47,7 +47,7 @@ The pinned `pi-subagents@0.75.0` includes the child-runtime fixes required for P
 
 The parent Pi session can select `forgeflow/planner` when the parent is acting as the planning/orchestration role. ForgeFlow's trusted `forgeflow.review` and `forgeflow.accept` workflows explicitly request `forgeflow/reviewer`, so the workflow owns the stable reviewer role while operator policy remains free to change the physical reviewer model without editing workflow code.
 
-`pi-subagents@0.75.0` contains the upstream child-runtime fixes for queued virtual-model registration and logical-selection verification (#2636 and #2638). ForgeFlow therefore does not carry a compatibility shim for virtual child models.
+`pi-subagents@0.75.0` contains the upstream child-runtime fixes for queued virtual-model registration and logical-selection verification (#2636 and #2638). ForgeFlow additionally registers a required child-only extension that does nothing except register the five `forgeflow/*` virtual models. Native Pi children therefore receive the logical model registry before model resolution without loading a second copy of ForgeFlow's prompt policy or trusted workflow resources. ForgeFlow does not carry a routing shim for virtual child models.
 
 ## Policy file
 

extension/child-model-policy.js

@@ -0,0 +1,5 @@
+import { registerForgeFlowVirtualModels } from "./model-policy.js";
+
+export default function registerForgeFlowChildModelPolicy(pi) {
+  registerForgeFlowVirtualModels(pi);
+}

extension/index.js

@@ -1,9 +1,16 @@
+import { fileURLToPath } from "node:url";
+
+import { registerRequiredChildExtensions } from "pi-subagents/required-child-extensions";
 import { registerWorkflowResource } from "pi-subagents/workflow-resources";
 import { renderPreflight } from "./invariants.js";
 import { createAcceptanceWorkflowDefinition } from "./acceptance-workflow.js";
 import { createReviewWorkflowDefinition } from "./review-workflow.js";
 import { registerForgeFlowVirtualModels } from "./model-policy.js";
 
+const CHILD_MODEL_POLICY_EXTENSION = fileURLToPath(
+  new URL("./child-model-policy.js", import.meta.url)
+);
+
 const CORE_POLICY = [
   "ForgeFlow is a thin engineering-governance extension for Pi; Pi and pi-subagents own agent execution, sessions, delegation, worktrees, missions, schedules, and resume.",
   "ForgeFlow may define stable logical model roles, but Pi owns virtual-model dispatch and the provider layer owns channel, credential, quota, and transport routing.",
@@ -22,6 +29,7 @@ export default function registerForgeFlow(pi) {
 
   let reviewRegistration;
   let acceptanceRegistration;
+  let childModelPolicyRegistration;
 
   pi.on("before_agent_start", (event) => {
     event.systemPromptOptions.sections.forgeflow_policy = buildForgeFlowPromptSection(event.prompt);
@@ -30,6 +38,7 @@ export default function registerForgeFlow(pi) {
   pi.on("session_start", (_event, ctx) => {
     reviewRegistration?.dispose();
     acceptanceRegistration?.dispose();
+    childModelPolicyRegistration?.dispose();
 
     const sessionId = ctx.sessionManager.getSessionId();
     const sessionCwd = ctx.cwd;
@@ -41,12 +50,23 @@ export default function registerForgeFlow(pi) {
       sessionId,
       definition: createAcceptanceWorkflowDefinition(sessionCwd)
     });
+    childModelPolicyRegistration = registerRequiredChildExtensions({
+      sessionId,
+      extensions: [
+        {
+          id: "forgeflow-model-policy",
+          path: CHILD_MODEL_POLICY_EXTENSION
+        }
+      ]
+    });
   });
 
   pi.on("session_shutdown", () => {
     reviewRegistration?.dispose();
     acceptanceRegistration?.dispose();
+    childModelPolicyRegistration?.dispose();
     reviewRegistration = undefined;
     acceptanceRegistration = undefined;
+    childModelPolicyRegistration = undefined;
   });
 }

package.json

@@ -35,6 +35,6 @@
   },
   "scripts": {
     "test": "node --test tests/*.test.js",
-    "check": "npm test && node --check extension/index.js && node --check extension/model-policy.js && node --check extension/invariants.js && node --check extension/review-workflow.js && node --check extension/review-verdict.js && node --check extension/github-acceptance.js && node --check extension/acceptance-workflow.js && node --check scripts/review-verdict.mjs && node --check scripts/github-acceptance.mjs"
+    "check": "npm test && node --check extension/index.js && node --check extension/child-model-policy.js && node --check extension/model-policy.js && node --check extension/invariants.js && node --check extension/review-workflow.js && node --check extension/review-verdict.js && node --check extension/github-acceptance.js && node --check extension/acceptance-workflow.js && node --check scripts/review-verdict.mjs && node --check scripts/github-acceptance.mjs"
   }
 }

tests/extension.test.js

@@ -1,6 +1,9 @@
 import assert from "node:assert/strict";
+import { fileURLToPath } from "node:url";
 import test from "node:test";
 
+import { registerRequiredChildExtensions } from "pi-subagents/required-child-extensions";
+import registerForgeFlowChildModelPolicy from "../extension/child-model-policy.js";
 import registerForgeFlow from "../extension/index.js";
 
 test("extension registers Pi lifecycle hooks and injects policy without a model call", () => {
@@ -40,14 +43,58 @@ test("extension registers Pi lifecycle hooks and injects policy without a model
   assert.match(event.systemPromptOptions.sections.forgeflow_policy, /INV-CUTOVER-001/);
   assert.match(event.systemPromptOptions.sections.forgeflow_policy, /INV-REPLAY-001/);
 
+  const sessionId = "forgeflow-pi-native-test";
   assert.doesNotThrow(() => {
     handlers.get("session_start")(
       {},
       {
         cwd: process.cwd(),
-        sessionManager: { getSessionId: () => "forgeflow-pi-native-test" }
+        sessionManager: { getSessionId: () => sessionId }
       }
     );
   });
+
+  const childExtensionPath = fileURLToPath(
+    new URL("../extension/child-model-policy.js", import.meta.url)
+  );
+  assert.throws(
+    () => registerRequiredChildExtensions({
+      sessionId,
+      extensions: [{ id: "duplicate-probe", path: childExtensionPath }]
+    }),
+    /already registered/
+  );
+
   assert.doesNotThrow(() => handlers.get("session_shutdown")());
+
+  const afterShutdown = registerRequiredChildExtensions({
+    sessionId,
+    extensions: [{ id: "post-shutdown-probe", path: childExtensionPath }]
+  });
+  afterShutdown.dispose();
+});
+
+test("child-only model policy extension registers only ForgeFlow virtual models", () => {
+  const registrations = [];
+  const handlers = [];
+  registerForgeFlowChildModelPolicy({
+    registerVirtualModel(definition) {
+      registrations.push(definition);
+    },
+    on(...args) {
+      handlers.push(args);
+    }
+  });
+
+  assert.deepEqual(
+    registrations.map(({ provider, id }) => `${provider}/${id}`),
+    [
+      "forgeflow/planner",
+      "forgeflow/worker",
+      "forgeflow/reviewer",
+      "forgeflow/scout",
+      "forgeflow/oracle"
+    ]
+  );
+  assert.deepEqual(handlers, []);
 });