feat(harness): integrate pi runtime into desktop app

apps/code/electron-builder.ts

@@ -49,6 +49,8 @@ const config: Configuration = {
     ".vite/build/plugins/posthog/**",
     ".vite/build/codex-acp/**",
     ".vite/build/grammars/**",
+    ".vite/build/rpc-host.js",
+    ".vite/build/rpc-host.js.map",
     ...asarUnpackGlobs,
   ],
 

apps/code/electron.vite.config.ts

@@ -22,6 +22,7 @@ import {
   copyCodexAcpBinaries,
   copyDrizzleMigrations,
   copyEnricherGrammars,
+  copyPiRpcHost,
   copyPosthogPlugin,
   fixFilenameCircularRef,
   getBuildDate,
@@ -93,6 +94,7 @@ export default defineConfig(({ mode }) => {
         autoServicesPlugin(path.join(__dirname, "src/main/services")),
         fixFilenameCircularRef(),
         copyClaudeExecutable(),
+        copyPiRpcHost(),
         copyPosthogPlugin(isDev),
         copyDrizzleMigrations(),
         copyCodexAcpBinaries(),

apps/code/package.json

@@ -152,6 +152,7 @@
     "reflect-metadata": "^0.2.2",
     "semver": "^7.8.1",
     "shadcn": "^4.1.2",
+    "superjson": "catalog:",
     "smol-toml": "^1.6.1",
     "tailwindcss-scroll-mask": "^0.0.3",
     "tw-animate-css": "^1.4.0",

apps/code/src/main/di/container.ts

@@ -184,6 +184,9 @@ import { OAUTH_CALLBACK_SERVER } from "@posthog/workspace-server/services/oauth-
 import { oauthCallbackModule } from "@posthog/workspace-server/services/oauth-callback/oauth-callback.module";
 import { onboardingImportModule } from "@posthog/workspace-server/services/onboarding-import/onboarding-import.module";
 import { osModule } from "@posthog/workspace-server/services/os/os.module";
+import { PI_SESSION_SERVICE } from "@posthog/workspace-server/services/pi-session/identifiers";
+import type { PiSessionService } from "@posthog/workspace-server/services/pi-session/pi-session";
+import { piSessionModule } from "@posthog/workspace-server/services/pi-session/pi-session.module";
 import { POSTHOG_PLUGIN_SERVICE } from "@posthog/workspace-server/services/posthog-plugin/identifiers";
 import { posthogPluginModule } from "@posthog/workspace-server/services/posthog-plugin/posthog-plugin.module";
 import { PROCESS_TRACKING_SERVICE } from "@posthog/workspace-server/services/process-tracking/identifiers";
@@ -356,6 +359,7 @@ container
   .bind(MAIN_DEFAULT_ADDITIONAL_DIRECTORY_REPOSITORY)
   .toService(DEFAULT_ADDITIONAL_DIRECTORY_REPOSITORY);
 container.load(agentModule);
+container.load(piSessionModule);
 container.bind(AGENT_SLEEP_COORDINATOR).toService(MAIN_SLEEP_SERVICE);
 container.bind(AGENT_MCP_APPS).toService(MCP_APPS_SERVICE);
 container.bind(AGENT_REPO_FILES).toService(MAIN_FS_SERVICE);
@@ -391,8 +395,12 @@ container.bind(MCP_PROXY_AUTH).toDynamicValue((ctx) => {
 });
 container.load(archiveModule);
 container.bind(ARCHIVE_SESSION_CANCELLER).toDynamicValue((ctx) => ({
-  cancelSessionsByTaskId: (taskId: string) =>
-    ctx.get<AgentService>(AGENT_SERVICE).cancelSessionsByTaskId(taskId),
+  cancelSessionsByTaskId: async (taskId: string) => {
+    await Promise.all([
+      ctx.get<AgentService>(AGENT_SERVICE).cancelSessionsByTaskId(taskId),
+      ctx.get<PiSessionService>(PI_SESSION_SERVICE).stop(taskId),
+    ]);
+  },
 }));
 container.bind(ARCHIVE_FILE_WATCHER).toDynamicValue((ctx) => ({
   stopWatching: async (worktreePath: string) => {
@@ -403,8 +411,12 @@ container.bind(ARCHIVE_FILE_WATCHER).toDynamicValue((ctx) => ({
 }));
 container.load(suspensionModule);
 container.bind(SUSPENSION_SESSION_CANCELLER).toDynamicValue((ctx) => ({
-  cancelSessionsByTaskId: (taskId: string) =>
-    ctx.get<AgentService>(AGENT_SERVICE).cancelSessionsByTaskId(taskId),
+  cancelSessionsByTaskId: async (taskId: string) => {
+    await Promise.all([
+      ctx.get<AgentService>(AGENT_SERVICE).cancelSessionsByTaskId(taskId),
+      ctx.get<PiSessionService>(PI_SESSION_SERVICE).stop(taskId),
+    ]);
+  },
 }));
 container.bind(SUSPENSION_FILE_WATCHER).toDynamicValue((ctx) => ({
   stopWatching: async (worktreePath: string) => {
@@ -675,7 +687,12 @@ container.load(workspaceModule);
 container.bind(WORKSPACE_AGENT).toDynamicValue((ctx): WorkspaceAgent => {
   const agent = ctx.get<AgentService>(AGENT_SERVICE);
   return {
-    cancelSessionsByTaskId: (taskId) => agent.cancelSessionsByTaskId(taskId),
+    cancelSessionsByTaskId: async (taskId) => {
+      await Promise.all([
+        agent.cancelSessionsByTaskId(taskId),
+        ctx.get<PiSessionService>(PI_SESSION_SERVICE).stop(taskId),
+      ]);
+    },
     onAgentFileActivity: (handler) =>
       agent.on(AgentServiceEvent.AgentFileActivity, handler),
   };

apps/code/src/main/trpc/router.ts

@@ -35,6 +35,7 @@ import { notificationRouter } from "@posthog/host-router/routers/notification.ro
 import { oauthRouter } from "@posthog/host-router/routers/oauth.router";
 import { onboardingImportRouter } from "@posthog/host-router/routers/onboarding-import.router";
 import { osRouter } from "@posthog/host-router/routers/os.router";
+import { piSessionRouter } from "@posthog/host-router/routers/pi-session.router";
 import { processTrackingRouter } from "@posthog/host-router/routers/process-tracking.router";
 import { provisioningRouter } from "@posthog/host-router/routers/provisioning.router";
 import { secureStoreRouter } from "@posthog/host-router/routers/secure-store.router";
@@ -93,6 +94,7 @@ export const trpcRouter = router({
   onboardingImport: onboardingImportRouter,
   logs: logsRouter,
   os: osRouter,
+  piSession: piSessionRouter,
   processTracking: processTrackingRouter,
   provisioning: provisioningRouter,
   sleep: sleepRouter,

apps/code/src/renderer/di/bindings.ts

@@ -65,6 +65,8 @@ import {
   GITHUB_CONNECT_CLIENT,
   type GithubConnectClient,
 } from "@posthog/core/onboarding/identifiers";
+import { PI_RUNNER } from "@posthog/core/pi-runtime/identifiers";
+import type { PiRunner } from "@posthog/core/pi-runtime/piRunner";
 import {
   type BundleLocalSkill,
   CLOUD_ARTIFACT_BUNDLE_LOCAL_SKILL,
@@ -276,6 +278,7 @@ export interface RendererBindings {
   [SHELL_PROCESS_READER]: ShellProcessReader;
   [ANALYTICS_TRACKER]: AnalyticsTracker;
   [TASK_CREATION_HOST]: ITaskCreationHost;
+  [PI_RUNNER]: PiRunner;
   [TASK_CREATION_EFFECTS]: TaskCreationEffects;
   [RENDERER_TASK_SERVICE]: TaskService;
   [TASK_SERVICE]: TaskService;

apps/code/src/renderer/di/container.ts

@@ -30,6 +30,8 @@ import {
 import { LLM_GATEWAY_SERVICE } from "@posthog/core/llm-gateway/identifiers";
 import type { LlmGatewayService } from "@posthog/core/llm-gateway/llm-gateway";
 import type { LlmMessage } from "@posthog/core/llm-gateway/schemas";
+import { PI_RUNNER } from "@posthog/core/pi-runtime/identifiers";
+import type { PiRunner } from "@posthog/core/pi-runtime/piRunner";
 import {
   CLOUD_ARTIFACT_BUNDLE_LOCAL_SKILL,
   CLOUD_ARTIFACT_READ_FILE_AS_BASE64,
@@ -149,6 +151,7 @@ import { trpcClient } from "@renderer/trpc";
 import { hostTrpcClient } from "@renderer/trpc/client";
 import type { TRPCClient } from "@trpc/client";
 import { hostLog, logger } from "@utils/logger";
+import { TrpcPiRunner } from "../platform-adapters/trpc-pi-runner";
 import type { RendererBindings } from "./bindings";
 import { TASK_SERVICE as RENDERER_TASK_SERVICE, TRPC_CLIENT } from "./tokens";
 
@@ -288,6 +291,7 @@ container
 
 // Bind services
 container.bind<ITaskCreationHost>(TASK_CREATION_HOST).to(TrpcTaskCreationHost);
+container.bind<PiRunner>(PI_RUNNER).to(TrpcPiRunner);
 container.bind(TASK_CREATION_EFFECTS).toConstantValue(taskCreationEffects);
 container.bind<TaskService>(RENDERER_TASK_SERVICE).to(TaskService);
 container.bind<TaskService>(TASK_SERVICE).toService(RENDERER_TASK_SERVICE);

apps/code/src/renderer/platform-adapters/trpc-pi-runner.ts

@@ -0,0 +1,28 @@
+import type {
+  PiResumeInput,
+  PiRunInput,
+  PiRunner,
+} from "@posthog/core/pi-runtime/piRunner";
+import { resolveService } from "@posthog/di/container";
+import {
+  HOST_TRPC_CLIENT,
+  type HostTrpcClient,
+} from "@posthog/host-router/client";
+
+function hostClient(): HostTrpcClient {
+  return resolveService<HostTrpcClient>(HOST_TRPC_CLIENT);
+}
+
+export class TrpcPiRunner implements PiRunner {
+  async create(input: PiRunInput): Promise<void> {
+    await hostClient().piSession.start.mutate(input);
+  }
+
+  resume(input: PiResumeInput): Promise<void> {
+    return hostClient().piSession.resume.mutate(input);
+  }
+
+  stop(taskId: string): Promise<void> {
+    return hostClient().piSession.stop.mutate({ taskId });
+  }
+}

apps/code/src/renderer/trpc/client.ts

@@ -7,14 +7,18 @@ import {
   createTRPCOptionsProxy,
 } from "@trpc/tanstack-react-query";
 import { queryClient } from "@utils/queryClient";
+import superjson from "superjson";
 import type { TrpcRouter } from "../../main/trpc/router";
 
 export const trpcClient = createTRPCClient<TrpcRouter>({
-  links: [ipcInstrumentationLink<TrpcRouter>(), ipcLink()],
+  links: [
+    ipcInstrumentationLink<TrpcRouter>(),
+    ipcLink({ transformer: superjson }),
+  ],
 });
 
 export const hostTrpcClient = createTRPCClient<HostRouter>({
-  links: [ipcLink()],
+  links: [ipcLink({ transformer: superjson })],
 });
 
 const context = createTRPCContext<TrpcRouter>();

apps/code/vite-main-plugins.mts

@@ -163,6 +163,29 @@ function copyClaudeSupportAssets(sourcePath: string, destDir: string): void {
   }
 }
 
+export function copyPiRpcHost(): Plugin {
+  return {
+    name: "copy-pi-rpc-host",
+    writeBundle() {
+      const candidates = [
+        join(__dirname, "node_modules/@posthog/agent/dist/pi/rpc-host.js"),
+        join(
+          __dirname,
+          "../../node_modules/@posthog/agent/dist/pi/rpc-host.js",
+        ),
+        join(__dirname, "../../packages/agent/dist/pi/rpc-host.js"),
+      ];
+      const source = candidates.find((candidate) => existsSync(candidate));
+      if (!source) {
+        throw new Error(
+          `[copy-pi-rpc-host] Unable to find Pi RPC host, required at runtime by createPiRpcClient. Build @posthog/agent first. Checked:\n  ${candidates.join("\n  ")}`,
+        );
+      }
+      copyFileSync(source, join(__dirname, ".vite/build/rpc-host.js"));
+    },
+  };
+}
+
 export function copyClaudeExecutable(): Plugin {
   return {
     name: "copy-claude-executable",

apps/web/package.json

@@ -20,6 +20,7 @@
     "@posthog/workspace-client": "workspace:*",
     "@tanstack/react-query": "^5.100.14",
     "@trpc/client": "^11.17.0",
+    "superjson": "catalog:",
     "@trpc/tanstack-react-query": "^11.17.0",
     "inversify": "^7.10.6",
     "react": "19.2.6",

apps/web/src/web-trpc.ts

@@ -5,6 +5,7 @@ import {
   httpSubscriptionLink,
   splitLink,
 } from "@trpc/client";
+import superjson from "superjson";
 
 // The ENTIRE electron->web transport difference. The renderer builds the same
 // client with `links: [ipcLink()]`; web swaps in HTTP: httpBatchLink for
@@ -16,8 +17,8 @@ export const hostTrpcClient = createTRPCClient<HostRouter>({
   links: [
     splitLink({
       condition: (op) => op.type === "subscription",
-      true: httpSubscriptionLink({ url: API_URL }),
-      false: httpBatchLink({ url: API_URL }),
+      true: httpSubscriptionLink({ url: API_URL, transformer: superjson }),
+      false: httpBatchLink({ url: API_URL, transformer: superjson }),
     }),
   ],
 });

packages/agent/package.json

@@ -28,6 +28,10 @@
       "types": "./dist/posthog-products.d.ts",
       "import": "./dist/posthog-products.js"
     },
+    "./pi/rpc-client": {
+      "types": "./dist/pi/rpc-client.d.ts",
+      "import": "./dist/pi/rpc-client.js"
+    },
     "./pr-url-detector": {
       "types": "./dist/pr-url-detector.d.ts",
       "import": "./dist/pr-url-detector.js"

packages/agent/src/pi/rpc-client.test.ts

@@ -7,7 +7,12 @@ describe("createPiRpcClient", () => {
     const client = createPiRpcClient({
       cwd: "/workspace",
       model: "claude-opus-4-8",
-      apiKey: "token",
+      oauthCredentials: {
+        access: "access-token",
+        refresh: "refresh-token",
+        expires: 0,
+        region: "us",
+      },
       env: { POSTHOG_REGION: "us" },
     });
 
@@ -17,7 +22,12 @@ describe("createPiRpcClient", () => {
         cwd: "/workspace",
         model: "claude-opus-4-8",
         env: {
-          POSTHOG_API_KEY: "token",
+          POSTHOG_OAUTH_CREDENTIALS: JSON.stringify({
+            access: "access-token",
+            refresh: "refresh-token",
+            expires: 0,
+            region: "us",
+          }),
           POSTHOG_REGION: "us",
         },
         provider: "posthog",

packages/agent/src/pi/rpc-client.ts

@@ -1,37 +1,49 @@
+import type { ChildProcess } from "node:child_process";
 import { fileURLToPath } from "node:url";
 import {
   RpcClient,
   type RpcClientOptions,
 } from "@earendil-works/pi-coding-agent";
+import type { PosthogOAuthCredentials } from "@posthog/harness";
 
 export type PiRpcClient = RpcClient;
 
+type RpcClientProcessAccess = {
+  process?: ChildProcess;
+};
+
+// HACK: Pi RpcClient does not expose its spawned child process or PID publicly.
+export function getPiRpcClientProcess(
+  client: PiRpcClient,
+): ChildProcess | null {
+  return (client as unknown as RpcClientProcessAccess).process ?? null;
+}
+
 export type PiRpcClientOptions = Pick<
   RpcClientOptions,
   "cwd" | "env" | "model"
 > & {
-  /** PostHog token passed only to the isolated RPC host process. */
-  apiKey?: string;
+  sessionFile?: string;
+  oauthCredentials: PosthogOAuthCredentials;
 };
 
-/**
- * Create a native Pi RPC client backed by the PostHog harness.
- *
- * The client owns an isolated child process. Call `start()` before sending
- * commands and `stop()` when the run is finished.
- */
-export function createPiRpcClient(
-  options: PiRpcClientOptions = {},
-): PiRpcClient {
-  const { apiKey, env, ...rpcOptions } = options;
+export function createPiRpcClient(options: PiRpcClientOptions): PiRpcClient {
+  const { env, sessionFile, oauthCredentials, ...rpcOptions } = options;
+  const args = sessionFile ? ["--session-file", sessionFile] : undefined;
+  const cliPath = fileURLToPath(new URL("./rpc-host.js", import.meta.url));
+  const oauthEnvironment: Record<string, string> = {
+    POSTHOG_OAUTH_CREDENTIALS: JSON.stringify(oauthCredentials),
+  };
+  const childEnvironment: Record<string, string> = {
+    ...env,
+    ...oauthEnvironment,
+  };
 
   return new RpcClient({
     ...rpcOptions,
-    cliPath: fileURLToPath(new URL("./rpc-host.js", import.meta.url)),
-    env: {
-      ...env,
-      ...(apiKey ? { POSTHOG_API_KEY: apiKey } : {}),
-    },
+    args,
+    cliPath,
+    env: childEnvironment,
     provider: "posthog",
   });
 }