pi-subagents/src/wrapper/cli.mjs

import { appendFile, readFile, writeFile } from "node:fs/promises";
import { spawn } from "node:child_process";
import { normalizePiEvent } from "./normalize.mjs";
import { renderHeader, renderEventLine } from "./render.mjs";

async function appendJsonLine(path, value) {
  await appendBestEffort(path, `${JSON.stringify(value)}\n`);
}

async function appendBestEffort(path, text) {
  try {
    await appendFile(path, text, "utf8");
  } catch {
    // Best-effort artifact logging should never prevent result.json from being written.
  }
}

function makeResult(meta, startedAt, input = {}) {
  const errorText = typeof input.errorMessage === "string" ? input.errorMessage.trim() : "";
  const exitCode = typeof input.exitCode === "number" ? input.exitCode : 1;
  return {
    runId: meta.runId,
    mode: meta.mode,
    taskIndex: meta.taskIndex,
    step: meta.step,
    agent: meta.agent,
    agentSource: meta.agentSource,
    task: meta.task,
    cwd: meta.cwd,
    requestedModel: meta.requestedModel,
    resolvedModel: input.resolvedModel ?? meta.resolvedModel,
    sessionPath: meta.sessionPath,
    startedAt,
    finishedAt: new Date().toISOString(),
    exitCode,
    stopReason: input.stopReason ?? (exitCode === 0 ? undefined : "error"),
    finalText: input.finalText ?? "",
    usage: input.usage,
    stdoutPath: meta.stdoutPath,
    stderrPath: meta.stderrPath,
    resultPath: meta.resultPath,
    eventsPath: meta.eventsPath,
    transcriptPath: meta.transcriptPath,
    errorMessage: errorText || undefined,
  };
}

async function runWrapper(meta, startedAt) {
  const header = renderHeader(meta);
  await appendBestEffort(meta.transcriptPath, `${header}\n`);
  console.log(header);

  const effectiveModel =
    typeof meta.resolvedModel === "string" && meta.resolvedModel.length > 0
      ? meta.resolvedModel
      : meta.requestedModel;

  const args = ["--mode", "json", "--session", meta.sessionPath];
  if (effectiveModel) args.push("--model", effectiveModel);
  if (Array.isArray(meta.tools) && meta.tools.length > 0) args.push("--tools", meta.tools.join(","));
  if (meta.systemPromptPath) args.push("--append-system-prompt", meta.systemPromptPath);
  args.push(meta.task);

  let finalText = "";
  let resolvedModel = meta.resolvedModel;
  let stopReason;
  let usage = undefined;
  let stdoutBuffer = "";
  let stderrText = "";
  let spawnError;
  let queue = Promise.resolve();

  const enqueue = (work) => {
    queue = queue.then(work, work);
    return queue;
  };

  const handleStdoutLine = async (line) => {
    if (!line.trim()) return;

    let parsed;
    try {
      parsed = JSON.parse(line);
    } catch {
      return;
    }

    const normalized = normalizePiEvent(parsed);
    if (!normalized) return;

    await appendJsonLine(meta.eventsPath, normalized);
    const rendered = renderEventLine(normalized);
    await appendBestEffort(meta.transcriptPath, `${rendered}\n`);
    console.log(rendered);

    if (normalized.type === "assistant_text") {
      finalText = normalized.text;
      resolvedModel = normalized.model ?? resolvedModel;
      stopReason = normalized.stopReason ?? stopReason;
      usage = normalized.usage ?? usage;
    }
  };

  const childEnv = { ...process.env };
  // Ensure the copilot initiator flag is not accidentally inherited from the parent
  // environment; set it only for github-copilot models.
  delete childEnv.PI_TMUX_SUBAGENT_GITHUB_COPILOT_INITIATOR;
  // Mark every child run as a nested tmux subagent so it cannot spawn further subagents.
  childEnv.PI_TMUX_SUBAGENT_CHILD = "1";

  if (typeof effectiveModel === "string" && effectiveModel.startsWith("github-copilot/")) {
    childEnv.PI_TMUX_SUBAGENT_GITHUB_COPILOT_INITIATOR = "agent";
  }

  const child = spawn("pi", args, {
    cwd: meta.cwd,
    env: childEnv,
    stdio: ["ignore", "pipe", "pipe"],
  });

  child.stdout.on("data", (chunk) => {
    const text = chunk.toString();
    enqueue(async () => {
      stdoutBuffer += text;
      await appendBestEffort(meta.stdoutPath, text);

      const lines = stdoutBuffer.split("\n");
      stdoutBuffer = lines.pop() ?? "";

      for (const line of lines) {
        await handleStdoutLine(line);
      }
    });
  });

  child.stderr.on("data", (chunk) => {
    const text = chunk.toString();
    enqueue(async () => {
      stderrText += text;
      await appendBestEffort(meta.stderrPath, text);
    });
  });

  const exitCode = await new Promise((resolve) => {
    let done = false;
    const finish = (code) => {
      if (done) return;
      done = true;
      resolve(code);
    };

    child.on("error", (error) => {
      spawnError = error;
      finish(1);
    });

    child.on("close", (code) => {
      finish(code ?? (spawnError ? 1 : 0));
    });
  });

  await queue;

  if (stdoutBuffer.trim()) {
    await handleStdoutLine(stdoutBuffer);
    stdoutBuffer = "";
  }

  if (spawnError) {
    const message = spawnError instanceof Error ? spawnError.stack ?? spawnError.message : String(spawnError);
    if (!stderrText.trim()) {
      stderrText = message;
      await appendBestEffort(meta.stderrPath, `${message}\n`);
    }
  }

  return makeResult(meta, startedAt, {
    exitCode,
    stopReason,
    finalText,
    usage,
    resolvedModel,
    errorMessage: stderrText,
  });
}

async function main() {
  const metaPath = process.argv[2];
  if (!metaPath) throw new Error("Expected meta.json path as argv[2]");

  const meta = JSON.parse(await readFile(metaPath, "utf8"));
  const startedAt = meta.startedAt ?? new Date().toISOString();

  let result;
  try {
    result = await runWrapper(meta, startedAt);
  } catch (error) {
    const message = error instanceof Error ? error.stack ?? error.message : String(error);
    await appendBestEffort(meta.stderrPath, `${message}\n`);
    result = makeResult(meta, startedAt, {
      exitCode: 1,
      stopReason: "error",
      errorMessage: message,
    });
  }

  await writeFile(meta.resultPath, JSON.stringify(result, null, 2), "utf8");
  if (result.exitCode !== 0) process.exitCode = result.exitCode;
}

main().catch((error) => {
  console.error(error instanceof Error ? error.stack : String(error));
  process.exitCode = 1;
});