docs: add stop-reason normalization implementation plan

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pi
2026-04-11 01:50:21 +01:00
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# Subagent Stop-Reason Normalization Implementation Plan
> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
**Goal:** Prevent wrapper from killing subagents on non-terminal assistant tool-use messages while preserving the lingering-child completion fix for true terminal completion.
**Architecture:** Keep JSON mode and fix the shared wrapper boundary. Normalize raw Pi stop reasons in `src/wrapper/normalize.mjs`, preserve `rawStopReason` for debugging, and make `src/wrapper/cli.mjs` start semantic cleanup only for canonical terminal reasons. Cover the regression with focused normalize and wrapper tests before touching implementation.
**Tech Stack:** Node.js ESM `.mjs`, `child_process`, `fs/promises`, `tsx --test`, Pi JSON event normalization
---
## Worktree and file structure
This plan runs in dedicated worktree:
`/home/dev/.pi/agent/extensions/subagents/.worktrees/subagent-stop-reason-normalization`
Baseline already verified in this worktree:
- `npm test``52 pass, 0 fail`
**Modify**
- `src/wrapper/normalize.mjs` — canonicalize raw stop reasons and preserve raw value
- `src/wrapper/normalize.test.ts` — regression tests for canonical stop-reason mapping
- `src/wrapper/cli.mjs` — gate semantic cleanup on terminal canonical stop reasons and thread `rawStopReason` into `result.json`
- `src/wrapper/cli.test.ts` — regression test for non-terminal `toolUse` assistant message followed by later true completion
### Task 1: Normalize raw stop reasons at wrapper boundary
**Files:**
- Modify: `src/wrapper/normalize.mjs`
- Modify: `src/wrapper/normalize.test.ts`
- Test: `src/wrapper/normalize.test.ts`
- [ ] **Step 1: Write the failing normalization tests**
Replace `src/wrapper/normalize.test.ts` content with:
```ts
import test from "node:test";
import assert from "node:assert/strict";
import { normalizePiEvent, normalizeStopReason } from "./normalize.mjs";
test("normalizePiEvent converts tool start events into protocol tool-call records", () => {
const normalized = normalizePiEvent({
type: "tool_execution_start",
toolName: "read",
args: { path: "src/app.ts", offset: 1, limit: 20 },
});
assert.deepEqual(normalized, {
type: "tool_call",
toolName: "read",
args: { path: "src/app.ts", offset: 1, limit: 20 },
});
});
test("normalizeStopReason maps raw tool-use variants to canonical toolUse", () => {
assert.deepEqual(normalizeStopReason("toolUse"), {
stopReason: "toolUse",
rawStopReason: "toolUse",
});
assert.deepEqual(normalizeStopReason("tool_use"), {
stopReason: "toolUse",
rawStopReason: "tool_use",
});
});
test("normalizeStopReason preserves unknown stop reasons without marking them terminal", () => {
assert.deepEqual(normalizeStopReason("custom_reason"), {
stopReason: undefined,
rawStopReason: "custom_reason",
});
});
test("normalizePiEvent converts assistant message_end into canonical final-text record", () => {
const normalized = normalizePiEvent({
type: "message_end",
message: {
role: "assistant",
model: "anthropic/claude-sonnet-4-5",
stopReason: "end_turn",
content: [{ type: "text", text: "Final answer" }],
usage: { input: 10, output: 5, totalTokens: 15, cost: { total: 0.001 } },
},
});
assert.deepEqual(normalized, {
type: "assistant_text",
text: "Final answer",
model: "anthropic/claude-sonnet-4-5",
stopReason: "stop",
rawStopReason: "end_turn",
usage: { input: 10, output: 5, totalTokens: 15, cost: { total: 0.001 } },
});
});
```
- [ ] **Step 2: Run normalize tests and verify red**
Run:
```bash
cd /home/dev/.pi/agent/extensions/subagents/.worktrees/subagent-stop-reason-normalization
npx tsx --test src/wrapper/normalize.test.ts
```
Expected: FAIL because `normalize.mjs` does not export `normalizeStopReason` yet, does not canonicalize `end_turn` to `stop`, and does not include `rawStopReason`.
- [ ] **Step 3: Implement minimal stop-reason normalization**
Replace `src/wrapper/normalize.mjs` content with:
```js
const STOP_REASON_MAP = new Map([
["stop", "stop"],
["end_turn", "stop"],
["endturn", "stop"],
["length", "length"],
["tooluse", "toolUse"],
["tool_use", "toolUse"],
["aborted", "aborted"],
["error", "error"],
]);
export function normalizeStopReason(value) {
if (typeof value !== "string") {
return { stopReason: undefined, rawStopReason: undefined };
}
const rawStopReason = value.trim();
if (!rawStopReason) {
return { stopReason: undefined, rawStopReason: undefined };
}
return {
stopReason: STOP_REASON_MAP.get(rawStopReason.toLowerCase()),
rawStopReason,
};
}
export function normalizePiEvent(event) {
if (event?.type === "tool_execution_start") {
return {
type: "tool_call",
toolName: event.toolName,
args: event.args ?? {},
};
}
if (event?.type === "message_end" && event.message?.role === "assistant") {
const text = (event.message.content ?? [])
.filter((part) => part.type === "text")
.map((part) => part.text)
.join("\n")
.trim();
const { stopReason, rawStopReason } = normalizeStopReason(event.message.stopReason);
return {
type: "assistant_text",
text,
model: event.message.model,
stopReason,
rawStopReason,
usage: event.message.usage,
};
}
if (event?.type === "tool_execution_end") {
return {
type: "tool_result",
toolName: event.toolName,
isError: Boolean(event.isError),
};
}
return null;
}
```
- [ ] **Step 4: Run normalize tests and verify green**
Run:
```bash
cd /home/dev/.pi/agent/extensions/subagents/.worktrees/subagent-stop-reason-normalization
npx tsx --test src/wrapper/normalize.test.ts
```
Expected: PASS with 4 passing subtests.
- [ ] **Step 5: Commit normalization layer**
Run:
```bash
cd /home/dev/.pi/agent/extensions/subagents/.worktrees/subagent-stop-reason-normalization
git add src/wrapper/normalize.mjs src/wrapper/normalize.test.ts
git commit -m "test: normalize subagent wrapper stop reasons"
```
### Task 2: Only trigger semantic cleanup on terminal canonical stop reasons
**Files:**
- Modify: `src/wrapper/cli.mjs`
- Modify: `src/wrapper/cli.test.ts`
- Test: `src/wrapper/cli.test.ts`
- [ ] **Step 1: Write the failing early-exit regression test**
Insert this test in `src/wrapper/cli.test.ts` before `wrapper exits and writes result.json after terminal output even if the pi child lingers`:
```ts
test("wrapper does not exit early on non-terminal toolUse assistant messages", async () => {
const dir = await mkdtemp(join(tmpdir(), "pi-subagents-wrapper-"));
const metaPath = join(dir, "meta.json");
const resultPath = join(dir, "result.json");
const eventsPath = join(dir, "events.jsonl");
const piPath = join(dir, "pi");
await writeFile(
piPath,
[
`#!${process.execPath}`,
"console.log(JSON.stringify({type:'message_end',message:{role:'assistant',content:[{type:'text',text:'starting'}],model:'openai/gpt-5',stopReason:'toolUse'}}));",
"setTimeout(() => console.log(JSON.stringify({type:'tool_execution_start',toolName:'read',args:{path:'src/auth.ts'}})), 400);",
"setTimeout(() => console.log(JSON.stringify({type:'message_end',message:{role:'assistant',content:[{type:'text',text:'final'}],model:'openai/gpt-5',stopReason:'stop'}})), 700);",
"setTimeout(() => process.exit(0), 1200);",
].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,
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.rawStopReason, "stop");
assert.equal(result.finalText, "final");
const eventsText = await readFile(eventsPath, "utf8");
assert.match(eventsText, /"type":"tool_call"/);
});
```
- [ ] **Step 2: Run wrapper tests and verify red**
Run:
```bash
cd /home/dev/.pi/agent/extensions/subagents/.worktrees/subagent-stop-reason-normalization
npx tsx --test src/wrapper/cli.test.ts
```
Expected: FAIL in the new test because current wrapper exits after the first `toolUse` assistant message. Typical failure is `result.stopReason` being `toolUse` instead of `stop`, and/or missing `tool_call` evidence in `events.jsonl`.
- [ ] **Step 3: Implement terminal-only cleanup and thread rawStopReason into results**
Make these exact edits in `src/wrapper/cli.mjs`.
Add this helper below `sleep()`:
```js
function isTerminalAssistantStopReason(stopReason) {
return stopReason === "stop" || stopReason === "length" || stopReason === "aborted" || stopReason === "error";
}
```
In `makeResult(...)`, add `rawStopReason` after `stopReason`:
```js
stopReason: input.stopReason ?? (exitCode === 0 ? undefined : "error"),
rawStopReason: input.rawStopReason,
finalText: input.finalText ?? "",
```
Add wrapper state for raw stop reason next to `let stopReason;`:
```js
let stopReason;
let rawStopReason;
```
Update the `assistant_text` branch inside `handleStdoutLine` to:
```js
if (normalized.type === "assistant_text") {
finalText = normalized.text;
resolvedModel = normalized.model ?? resolvedModel;
stopReason = normalized.stopReason ?? stopReason;
rawStopReason = normalized.rawStopReason ?? rawStopReason;
usage = normalized.usage ?? usage;
if (isTerminalAssistantStopReason(normalized.stopReason)) {
void forceChildExitAfterSemanticCompletion();
}
}
```
Update the final `makeResult(...)` call at the end of `runWrapper(...)` to pass `rawStopReason`:
```js
return makeResult(meta, startedAt, {
exitCode,
stopReason,
rawStopReason,
finalText,
usage,
resolvedModel,
errorMessage: stderrText,
});
```
This is deliberately small: keep current artifact handling, keep current child env behavior, keep current grace timings, and only change how completion is triggered and reported.
- [ ] **Step 4: Run wrapper tests and verify green**
Run:
```bash
cd /home/dev/.pi/agent/extensions/subagents/.worktrees/subagent-stop-reason-normalization
npx tsx --test src/wrapper/cli.test.ts
```
Expected: PASS. In particular:
- non-terminal `toolUse` regression test passes
- lingering terminal-message child test still passes
- spawn-failure test still passes
- artifact-write-failure test still passes
- [ ] **Step 5: Run full package test suite**
Run:
```bash
cd /home/dev/.pi/agent/extensions/subagents/.worktrees/subagent-stop-reason-normalization
npm test
```
Expected: all tests PASS across wrapper, runner, extension, and tool coverage.
- [ ] **Step 6: Commit wrapper completion fix**
Run:
```bash
cd /home/dev/.pi/agent/extensions/subagents/.worktrees/subagent-stop-reason-normalization
git add src/wrapper/cli.mjs src/wrapper/cli.test.ts
git commit -m "fix: preserve non-terminal subagent tool-use turns"
```