fix: finish lingering subagent wrapper runs

src/wrapper/cli.mjs

@@ -3,6 +3,13 @@ import { spawn } from "node:child_process";
 import { normalizePiEvent } from "./normalize.mjs";
 import { renderHeader, renderEventLine } from "./render.mjs";
 
+const SEMANTIC_EXIT_GRACE_MS = 250;
+const FORCED_EXIT_GRACE_MS = 250;
+
+async function sleep(ms) {
+  await new Promise((resolve) => setTimeout(resolve, ms));
+}
+
 async function appendJsonLine(path, value) {
   await appendBestEffort(path, `${JSON.stringify(value)}\n`);
 }
@@ -68,8 +75,26 @@ async function runWrapper(meta, startedAt) {
   let stdoutBuffer = "";
   let stderrText = "";
   let spawnError;
+  let childClosed = false;
+  let completionCleanupStarted = false;
+  let child;
   let queue = Promise.resolve();
 
+  const forceChildExitAfterSemanticCompletion = async () => {
+    if (completionCleanupStarted) return;
+    completionCleanupStarted = true;
+
+    await sleep(SEMANTIC_EXIT_GRACE_MS);
+    if (childClosed) return;
+
+    child.kill("SIGTERM");
+
+    await sleep(FORCED_EXIT_GRACE_MS);
+    if (childClosed) return;
+
+    child.kill("SIGKILL");
+  };
+
   const enqueue = (work) => {
     queue = queue.then(work, work);
     return queue;
@@ -98,6 +123,10 @@ async function runWrapper(meta, startedAt) {
       resolvedModel = normalized.model ?? resolvedModel;
       stopReason = normalized.stopReason ?? stopReason;
       usage = normalized.usage ?? usage;
+
+      if (normalized.stopReason) {
+        void forceChildExitAfterSemanticCompletion();
+      }
     }
   };
 
@@ -112,7 +141,7 @@ async function runWrapper(meta, startedAt) {
     childEnv.PI_SUBAGENTS_GITHUB_COPILOT_INITIATOR = "agent";
   }
 
-  const child = spawn("pi", args, {
+  child = spawn("pi", args, {
     cwd: meta.cwd,
     env: childEnv,
     stdio: ["ignore", "pipe", "pipe"],
@@ -151,10 +180,12 @@ async function runWrapper(meta, startedAt) {
 
     child.on("error", (error) => {
       spawnError = error;
+      childClosed = true;
       finish(1);
     });
 
     child.on("close", (code) => {
+      childClosed = true;
       finish(code ?? (spawnError ? 1 : 0));
     });
   });

src/wrapper/cli.test.ts

@@ -191,6 +191,66 @@ test("wrapper exits and writes result.json when the pi child cannot be spawned",
   assert.match(result.errorMessage ?? "", /ENOENT|not found|spawn pi/i);
 });
 
+test("wrapper exits and writes result.json after terminal output even if the pi child lingers", async () => {
+  const dir = await mkdtemp(join(tmpdir(), "pi-subagents-wrapper-"));
+  const metaPath = join(dir, "meta.json");
+  const resultPath = join(dir, "result.json");
+  const piPath = join(dir, "pi");
+
+  await writeFile(
+    piPath,
+    [
+      `#!${process.execPath}`,
+      "console.log(JSON.stringify({type:'message_end',message:{role:'assistant',content:[{type:'text',text:'done'}],model:'openai/gpt-5',stopReason:'stop'}}));",
+      "setTimeout(() => {}, 10_000);",
+    ].join("\n"),
+    "utf8",
+  );
+  await chmod(piPath, 0o755);
+
+  await writeFile(
+    metaPath,
+    JSON.stringify(
+      {
+        runId: "run-1",
+        mode: "single",
+        agent: "scout",
+        agentSource: "builtin",
+        task: "inspect auth",
+        cwd: dir,
+        requestedModel: "openai/gpt-5",
+        resolvedModel: "openai/gpt-5",
+        startedAt: "2026-04-09T00:00:00.000Z",
+        sessionPath: join(dir, "child-session.jsonl"),
+        eventsPath: join(dir, "events.jsonl"),
+        resultPath,
+        stdoutPath: join(dir, "stdout.log"),
+        stderrPath: join(dir, "stderr.log"),
+        transcriptPath: join(dir, "transcript.log"),
+        systemPromptPath: join(dir, "system-prompt.md"),
+      },
+      null,
+      2,
+    ),
+    "utf8",
+  );
+
+  const wrapperPath = join(dirname(fileURLToPath(import.meta.url)), "cli.mjs");
+  const child = spawn(process.execPath, [wrapperPath, metaPath], {
+    env: { ...process.env, PATH: dir },
+    stdio: ["ignore", "pipe", "pipe"],
+  });
+
+  const exitCode = await waitForExit(child);
+  assert.equal(exitCode, 0);
+
+  const result = JSON.parse(await readFile(resultPath, "utf8"));
+  assert.equal(result.exitCode, 0);
+  assert.equal(result.stopReason, "stop");
+  assert.equal(result.finalText, "done");
+  assert.equal(result.resolvedModel, "openai/gpt-5");
+});
+
 test("wrapper still writes result.json when transcript/stdout artifact writes fail", async () => {
   const dir = await mkdtemp(join(tmpdir(), "pi-subagents-wrapper-"));
   const metaPath = join(dir, "meta.json");