Read archived Pi chats after their working folder is removed (#8442)

* fix(pi): open an archived Pi agent's history after its folder is removed Opening an archived agent's timeline resumes its provider for history. Pi's resumeSession never received the resume purpose, so it launched the Pi RPC process, and its MCP support probe, in the agent's stored working directory. When that folder had been removed, for example with a merged worktree, Node failed the spawn with "spawn <command> ENOENT" and the history could not be read. Starting the process elsewhere is not enough: with --session, Pi checks the cwd stored in the session file's header and, outside interactive mode, exits when that folder is missing. A history resume whose stored folder is no longer a directory now starts Pi from the home directory on a temporary copy of the session file whose header names that directory. The copy streams everything after the header unchanged and is deleted when the session closes. The agent keeps reporting its stored folder and original session file, and the original file is not written to. The directory check moves out of the ACP provider, which already starts history loads from the home directory (#6228), into a shared helper both providers use. Fixes #7969 * test(terminal): keep the argv test child alive through its assertion The POSIX argv test reads the terminal screen while its child can exit and dispose the parser. Keep the child alive until the assertion completes, as other screen tests do, and let the existing session cleanup terminate it. Co-authored-by: Dominic Anaeto <dominic.anaeto@gmail.com> --------- Co-authored-by: Dominic Anaeto <dominic.anaeto@gmail.com> Co-authored-by: paseo-bot[bot] <266920839+paseo-bot[bot]@users.noreply.github.com>
2026-11-01 14:12:51 +00:00 · 2026-11-01 06:52:48 +00:00
parent 891e62309c
commit 14519bdb5b
8 changed files with 586 additions and 35 deletions
@@ -120,6 +120,7 @@ import {
 } from "../provider-launch-config.js";
 import { renderPromptAttachmentAsText } from "../prompt-attachments.js";
 import { appendOrReplaceGrowingAssistantMessage, runProviderTurn } from "./provider-runner.js";
+import { resolveResumeProcessCwd } from "./resume-process-cwd.js";
 import {
  buildStringCommandShellInvocation,
  createStringCommandShellEnvOverlay,
@@ -165,18 +166,6 @@ function rejectOnProcessFailure(child: ChildProcess, stderrChunks: string[]): Pr
  });
 }

-async function isDirectory(target: string): Promise<boolean> {
-  try {
-    return (await fs.stat(target)).isDirectory();
-  } catch (error) {
-    const code = (error as NodeJS.ErrnoException).code;
-    if (code === "ENOENT" || code === "ENOTDIR") {
-      return false;
-    }
-    throw error;
-  }
-}
-
 function isRecord(value: unknown): value is Record<string, unknown> {
  return value != null && typeof value === "object" && !Array.isArray(value);
 }
@@ -2883,11 +2872,8 @@ export class ACPAgentSession implements AgentSession, ACPClient {
  // Loading an archived agent's history runs nothing in its working directory, which
  // may have been removed with its worktree. session/load still names the original
  // directory; only the process starts from the home directory.
-  private async resolveProcessCwd(): Promise<string> {
-    if (this.resumePurpose !== "history" || (await isDirectory(this.config.cwd))) {
-      return this.config.cwd;
-    }
-    return homedir();
+  private resolveProcessCwd(): Promise<string> {
+    return resolveResumeProcessCwd(this.config.cwd, this.resumePurpose);
  }

  private async spawnProcess(): Promise<SpawnedACPProcess> {
@@ -5,11 +5,13 @@ import {
  mkdirSync,
  mkdtempSync,
  openSync,
+  readFileSync,
  readSync,
+  realpathSync,
  rmSync,
  writeFileSync,
 } from "node:fs";
-import { tmpdir } from "node:os";
+import { homedir, tmpdir } from "node:os";
 import path from "node:path";
 import pino from "pino";
 import { setImmediate as waitForImmediate } from "node:timers/promises";
@@ -23,6 +25,7 @@ import {
  PiRpcAgentSession,
  transformPiModels,
 } from "./agent.js";
+import { PiCliRuntime } from "./cli-runtime.js";
 import { FakePi } from "./test-utils/fake-pi.js";
 import { createPiExtensionHost } from "./extensions/index.js";
 import { PiExtensionHost } from "./extensions/host.js";
@@ -2719,6 +2722,7 @@ describe("PiRpcAgentClient", () => {
    const root = mkdtempSync(path.join(tmpdir(), "paseo-pi-import-config-"));
    const cwd = path.join(root, "workspace");
    const sessionsDir = path.join(root, "sessions");
+    mkdirSync(cwd, { recursive: true });
    mkdirSync(sessionsDir, { recursive: true });
    const sessionFile = path.join(sessionsDir, "20260103_session.jsonl");
    writeFileSync(
@@ -3532,6 +3536,320 @@ describe("PiRpcAgentClient", () => {
  });
 });

+describe("PiRpcAgentClient history resume", () => {
+  const BUILTIN_MCP_COMMAND = {
+    name: "mcp",
+    source: "extension",
+    sourceInfo: { path: "builtin:mcp" },
+  } as const;
+  const PASEO_MCP_SERVERS = {
+    paseo: { type: "http", url: "http://127.0.0.1:6767/mcp/agents" },
+  } as const;
+
+  interface ArchivedPiSession {
+    handle: {
+      provider: string;
+      sessionId: string;
+      nativeHandle: string;
+      metadata: { cwd: string; model?: string };
+    };
+    sessionFile: string;
+    header: Record<string, unknown>;
+    body: string;
+    originalBytes: Buffer;
+  }
+
+  function createDeletedFolder(): string {
+    const folder = mkdtempSync(path.join(tmpdir(), "paseo-pi-deleted-cwd-"));
+    rmSync(folder, { recursive: true, force: true });
+    return folder;
+  }
+
+  function createFileWhereFolderWas(): string {
+    const folder = createDeletedFolder();
+    writeFileSync(folder, "not a directory");
+    onTestFinished(() => rmSync(folder, { force: true }));
+    return folder;
+  }
+
+  function createExistingFolder(): string {
+    const folder = mkdtempSync(path.join(tmpdir(), "paseo-pi-existing-cwd-"));
+    onTestFinished(() => rmSync(folder, { recursive: true, force: true }));
+    return folder;
+  }
+
+  function writeArchivedSession(cwd: string, metadata: { model?: string } = {}): ArchivedPiSession {
+    const dir = mkdtempSync(path.join(tmpdir(), "paseo-pi-archived-session-"));
+    onTestFinished(() => rmSync(dir, { recursive: true, force: true }));
+    const sessionFile = path.join(dir, "2026-01-01_pi-session-1.jsonl");
+    const header = {
+      type: "session",
+      version: 3,
+      id: "pi-session-1",
+      timestamp: "2026-01-01T00:00:00.000Z",
+      cwd,
+    };
+    const body = [
+      JSON.stringify({
+        type: "message",
+        id: "entry-1",
+        parentId: null,
+        message: { role: "user", content: "Où est le café ☕ ?" },
+      }),
+      JSON.stringify({
+        type: "message",
+        id: "entry-2",
+        parentId: "entry-1",
+        message: { role: "assistant", content: [{ type: "text", text: "Dans la cuisine." }] },
+      }),
+    ]
+      .map((line) => `${line}\n`)
+      .join("");
+    writeFileSync(sessionFile, `${JSON.stringify(header)}\n${body}`);
+    return {
+      handle: {
+        provider: "pi",
+        sessionId: "pi-session-1",
+        nativeHandle: sessionFile,
+        metadata: { cwd, ...metadata },
+      },
+      sessionFile,
+      header,
+      body,
+      originalBytes: readFileSync(sessionFile),
+    };
+  }
+
+  function readSessionCopy(sessionFile: string): { header: unknown; body: string } {
+    const content = readUtf8File(sessionFile);
+    const headerEnd = content.indexOf("\n");
+    return {
+      header: JSON.parse(content.slice(0, headerEnd)),
+      body: content.slice(headerEnd + 1),
+    };
+  }
+
+  function resumeArchived(
+    client: PiRpcAgentClient,
+    archived: ArchivedPiSession,
+    purpose: "history" | "interactive",
+    overrides: Partial<AgentSessionConfig> = {},
+  ): Promise<AgentSession> {
+    return client.resumeSession(archived.handle, overrides, undefined, { purpose });
+  }
+
+  function writeFakePiProcess(): {
+    command: [string, ...string[]];
+    readLaunches: () => Array<{ cwd: string; session: string | null }>;
+  } {
+    const dir = mkdtempSync(path.join(tmpdir(), "paseo-pi-process-"));
+    onTestFinished(() => rmSync(dir, { recursive: true, force: true }));
+    const scriptPath = path.join(dir, "fake-pi.cjs");
+    const launchesPath = path.join(dir, "launches.jsonl");
+    writeFileSync(
+      scriptPath,
+      `
+const fs = require("node:fs");
+const readline = require("node:readline");
+const [launchesPath, ...piArgs] = process.argv.slice(2);
+const sessionFlag = piArgs.indexOf("--session");
+const sessionFile = sessionFlag === -1 ? null : piArgs[sessionFlag + 1];
+fs.appendFileSync(launchesPath, JSON.stringify({ cwd: process.cwd(), session: sessionFile }) + "\\n");
+if (sessionFile) {
+  const header = JSON.parse(fs.readFileSync(sessionFile, "utf8").split("\\n", 1)[0]);
+  if (header.cwd && !fs.existsSync(header.cwd)) {
+    fs.writeSync(
+      2,
+      "Stored session working directory does not exist: " + header.cwd + "\\nSession file: " + sessionFile + "\\nCurrent working directory: " + process.cwd() + "\\n",
+    );
+    process.exit(1);
+  }
+}
+const models = [
+  { provider: "openrouter", id: "a" },
+  { provider: "openrouter", id: "b" },
+];
+const state = {
+  sessionId: "pi-session-1",
+  sessionFile,
+  model: models[0],
+  thinkingLevel: "medium",
+  isStreaming: false,
+  isCompacting: false,
+  messageCount: 0,
+  pendingMessageCount: 0,
+};
+const commands = [${JSON.stringify(BUILTIN_MCP_COMMAND)}];
+function handle(request) {
+  switch (request.type) {
+    case "get_state":
+      return state;
+    case "get_commands":
+      return { commands };
+    case "get_available_models":
+      return { models };
+    case "set_model":
+      fs.appendFileSync(
+        sessionFile,
+        JSON.stringify({ type: "model_change", id: "model-1", provider: request.provider, modelId: request.modelId }) + "\\n",
+      );
+      state.model = models.find((model) => model.id === request.modelId);
+      return state.model;
+    default:
+      return {};
+  }
+}
+readline.createInterface({ input: process.stdin }).on("line", (line) => {
+  const request = JSON.parse(line);
+  process.stdout.write(
+    JSON.stringify({ id: request.id, type: "response", command: request.type, success: true, data: handle(request) }) + "\\n",
+  );
+});
+`,
+    );
+    return {
+      command: [process.execPath, scriptPath, launchesPath],
+      readLaunches: () =>
+        readUtf8File(launchesPath)
+          .trim()
+          .split("\n")
+          .map((line) => JSON.parse(line) as { cwd: string; session: string | null }),
+    };
+  }
+
+  test.each([
+    ["is gone", createDeletedFolder],
+    ["is now a file", createFileWhereFolderWas],
+  ])(
+    "a history resume of an agent whose folder %s starts Pi from the home directory on a copy of its session",
+    async (_folderState, createFolder) => {
+      const archived = writeArchivedSession(createFolder());
+      const pi = new FakePi();
+
+      const session = await resumeArchived(createClient(pi), archived, "history");
+      onTestFinished(() => session.close());
+
+      expect(pi.recordedLaunches).toHaveLength(1);
+      const launch = pi.recordedLaunches[0]!;
+      expect(launch.cwd).toBe(homedir());
+      expect(launch.session).not.toBe(archived.sessionFile);
+      expect(readSessionCopy(launch.session!)).toEqual({
+        header: { ...archived.header, cwd: homedir() },
+        body: archived.body,
+      });
+    },
+  );
+
+  test("a history resume of an agent whose folder is gone removes its session copy on close and leaves the original unchanged", async () => {
+    const archived = writeArchivedSession(createDeletedFolder());
+    const pi = new FakePi();
+
+    const session = await resumeArchived(createClient(pi), archived, "history");
+    const sessionCopy = pi.recordedLaunches[0]!.session!;
+    expect(existsSync(sessionCopy)).toBe(true);
+    await session.close();
+
+    expect(existsSync(path.dirname(sessionCopy))).toBe(false);
+    expect(readFileSync(archived.sessionFile)).toEqual(archived.originalBytes);
+  });
+
+  test("a history resume of an agent whose folder is gone persists the original session file while Pi reports the copy", async () => {
+    const storedCwd = createDeletedFolder();
+    const archived = writeArchivedSession(storedCwd);
+    const pi = new FakePi();
+
+    const session = await resumeArchived(createClient(pi), archived, "history");
+    onTestFinished(() => session.close());
+    await session.getRuntimeInfo();
+
+    expect(pi.latestSession().state.sessionFile).toBe(pi.recordedLaunches[0]!.session);
+    expect(session.describePersistence()).toMatchObject({
+      nativeHandle: archived.sessionFile,
+      metadata: { cwd: storedCwd },
+    });
+  });
+
+  test("a history resume of an agent whose folder is gone removes its session copy when Pi fails to start", async () => {
+    const archived = writeArchivedSession(createDeletedFolder());
+    const pi = new FakePi();
+    pi.queueSessionSetup((session) => {
+      session.getStateError = new Error("Pi RPC process exited with code 1 and signal null");
+    });
+
+    await expect(resumeArchived(createClient(pi), archived, "history")).rejects.toThrow(
+      "Pi RPC process exited with code 1",
+    );
+
+    expect(pi.recordedLaunches).toHaveLength(1);
+    expect(pi.recordedLaunches[0]!.session).not.toBe(archived.sessionFile);
+    expect(existsSync(path.dirname(pi.recordedLaunches[0]!.session!))).toBe(false);
+  });
+
+  test("a history resume of an agent whose folder is gone checks MCP support from the home directory", async () => {
+    const archived = writeArchivedSession(createDeletedFolder());
+    const pi = new FakePi();
+    pi.queueCommands([BUILTIN_MCP_COMMAND]);
+
+    const session = await resumeArchived(createClient(pi), archived, "history", {
+      mcpServers: PASEO_MCP_SERVERS,
+    });
+    onTestFinished(() => session.close());
+
+    expect(pi.recordedLaunches.map((launch) => launch.cwd)).toEqual([homedir(), homedir()]);
+    expect(session.capabilities.supportsMcpServers).toBe(true);
+  });
+
+  test("an interactive resume of an agent whose folder is gone still fails in its stored folder", async () => {
+    const storedCwd = createDeletedFolder();
+    const archived = writeArchivedSession(storedCwd);
+    const pi = new FakePi();
+
+    await expect(resumeArchived(createClient(pi), archived, "interactive")).rejects.toThrow(
+      `Stored session working directory does not exist: ${storedCwd}`,
+    );
+
+    expect(pi.recordedLaunches).toMatchObject([{ cwd: storedCwd, session: archived.sessionFile }]);
+  });
+
+  test("a history resume of an agent whose folder exists keeps the stored folder and session file", async () => {
+    const storedCwd = createExistingFolder();
+    const archived = writeArchivedSession(storedCwd);
+    const pi = new FakePi();
+
+    const session = await resumeArchived(createClient(pi), archived, "history");
+    onTestFinished(() => session.close());
+
+    expect(pi.recordedLaunches).toMatchObject([{ cwd: storedCwd, session: archived.sessionFile }]);
+  });
+
+  test("a history resume of an agent whose folder is gone opens its session in a real Pi process started from the home directory", async () => {
+    const archived = writeArchivedSession(createDeletedFolder(), { model: "openrouter/b" });
+    const fakePiProcess = writeFakePiProcess();
+    const logger = pino({ level: "silent" });
+    const client = new PiRpcAgentClient({
+      logger,
+      runtime: new PiCliRuntime({ logger, command: fakePiProcess.command }),
+    });
+
+    const session = await resumeArchived(client, archived, "history", {
+      mcpServers: PASEO_MCP_SERVERS,
+    });
+    onTestFinished(() => session.close());
+
+    const launches = fakePiProcess.readLaunches();
+    const home = realpathSync.native(homedir());
+    expect(launches.map((launch) => realpathSync.native(launch.cwd))).toEqual([home, home]);
+    expect(session.capabilities.supportsMcpServers).toBe(true);
+    const sessionCopy = launches[1]!.session!;
+    expect(readUtf8File(sessionCopy)).toContain('"type":"model_change"');
+    expect(session.describePersistence()?.nativeHandle).toBe(archived.sessionFile);
+
+    await session.close();
+    expect(existsSync(path.dirname(sessionCopy))).toBe(false);
+    expect(readFileSync(archived.sessionFile)).toEqual(archived.originalBytes);
+  });
+});
+
 describe("transformPiModels", () => {
  test("normalizes labels that include the upstream provider prefix", () => {
    expect(
@@ -2,7 +2,7 @@ import { mapCustomMessageToToolCall } from "../custom-message.js";
 import { randomUUID } from "node:crypto";
 import { existsSync, mkdtempSync, readFileSync, rmSync, writeFileSync } from "node:fs";
 import { homedir, tmpdir } from "node:os";
-import { join, resolve as resolvePath } from "node:path";
+import { basename, join, resolve as resolvePath } from "node:path";
 import type { Logger } from "pino";
 import stripAnsi from "strip-ansi";
 import { z } from "zod";
@@ -22,6 +22,7 @@ import {
  type AgentPersistenceHandle,
  type AgentPromptInput,
  type AgentProvider,
+  type AgentResumeSessionOptions,
  type AgentRunOptions,
  type AgentRunResult,
  type AgentRuntimeInfo,
@@ -75,8 +76,13 @@ import {
  piExtensionRuntimeBridge,
  type PiExtensionEventOutput,
 } from "./extensions/index.js";
+import { resolveResumeProcessCwd } from "../resume-process-cwd.js";
 import { revertPiConversation } from "./rewind.js";
-import { listPiImportableSessions, readPiImportSessionConfig } from "./session-descriptor.js";
+import {
+  copyPiSessionFileWithCwd,
+  listPiImportableSessions,
+  readPiImportSessionConfig,
+} from "./session-descriptor.js";
 import type { PiRuntime, PiRuntimeSession, PiStartSessionInput } from "./runtime.js";
 import type {
  PiAgentSessionEvent,
@@ -245,6 +251,7 @@ interface PiRpcAgentSessionOptions {
  initialState: PiSessionState;
  capabilities: AgentCapabilityFlags;
  currentModeId?: string | null;
+  persistedSessionFile?: string;
  cleanup?: () => void;
  extensionTimeoutMs?: number;
  logger: Logger;
@@ -492,13 +499,14 @@ function buildResumeConfig(

 function buildResumeStartInput(input: {
  resumeConfig: PiResumeConfig;
+  processCwd: string;
  sessionFile: string;
  launchContext: AgentLaunchContext | undefined;
  mcpConfigFile: PiTempFile | null;
  paseoExtension: PiTempFile | null;
 }): PiStartSessionInput {
  return {
-    cwd: input.resumeConfig.cwd,
+    cwd: input.processCwd,
    env: input.launchContext?.env,
    session: input.sessionFile,
    thinkingOptionId: normalizePiThinkingOption(input.resumeConfig.thinkingOptionId) ?? undefined,
@@ -618,6 +626,19 @@ function createPiMcpConfigFile(
  };
 }

+async function createPiSessionCopy(sessionFile: string, cwd: string): Promise<PiTempFile> {
+  const dir = mkdtempSync(join(tmpdir(), "paseo-pi-session-"));
+  const cleanup = () => rmSync(dir, { recursive: true, force: true });
+  const filePath = join(dir, basename(sessionFile));
+  try {
+    await copyPiSessionFileWithCwd({ sourceFile: sessionFile, targetFile: filePath, cwd });
+  } catch (error) {
+    cleanup();
+    throw error;
+  }
+  return { path: filePath, cleanup };
+}
+
 function createPiPaseoExtensionFile({
  systemPrompt,
  mcpServers = {},
@@ -1232,6 +1253,7 @@ export class PiRpcAgentSession implements AgentSession {
    this.capabilities = options.capabilities;
    this.provider = PI_PROVIDER;
    this.currentModeId = options.currentModeId ?? null;
+    this.persistedSessionFile = options.persistedSessionFile;
    this.cleanup = options.cleanup;
    this.extensionTimeoutMs = options.extensionTimeoutMs ?? DEFAULT_PI_EXTENSION_RESULT_TIMEOUT_MS;
    this.logger = options.logger;
@@ -1262,6 +1284,7 @@ export class PiRpcAgentSession implements AgentSession {

  private readonly runtimeSession: PiRuntimeSession;
  private readonly config: AgentSessionConfig;
+  private readonly persistedSessionFile?: string;
  private readonly cleanup?: () => void;
  private readonly extensionTimeoutMs: number;

@@ -1496,7 +1519,7 @@ export class PiRpcAgentSession implements AgentSession {
    return {
      provider: this.provider,
      sessionId: this.state.sessionId,
-      nativeHandle: this.state.sessionFile,
+      nativeHandle: this.persistedSessionFile ?? this.state.sessionFile,
      metadata: {
        cwd: this.config.cwd,
        ...(this.config.model ? { model: this.config.model } : {}),
@@ -2645,6 +2668,7 @@ export class PiRpcAgentClient implements AgentClient {
    handle: AgentPersistenceHandle,
    overrides?: Partial<AgentSessionConfig>,
    launchContext?: AgentLaunchContext,
+    options?: AgentResumeSessionOptions,
  ): Promise<AgentSession> {
    const sessionFile = handle.nativeHandle;
    if (!sessionFile) {
@@ -2653,6 +2677,7 @@ export class PiRpcAgentClient implements AgentClient {

    const persistenceMetadata = parsePersistenceMetadata(handle.metadata);
    const resumeConfig = buildResumeConfig(persistenceMetadata, overrides, this.provider);
+    const processCwd = await resolveResumeProcessCwd(resumeConfig.cwd, options?.purpose);

    const providerOptions = PiProviderOptionsSchema.parse(
      resumeConfig.config.providerOptions ?? {},
@@ -2663,7 +2688,7 @@ export class PiRpcAgentClient implements AgentClient {
      ...launchContext?.env,
    };
    const mcp = await this.prepareMcpInjection(
-      resumeConfig.cwd,
+      processCwd,
      resumeConfig.config.mcpServers,
      mcpEnv,
      runtime,
@@ -2676,20 +2701,29 @@ export class PiRpcAgentClient implements AgentClient {
      ),
      mcpServers: mcp?.kind === "builtin" ? mcp.servers : undefined,
    });
+    const tempFiles = mcpConfigFile ? [mcpConfigFile, paseoExtension] : [paseoExtension];
+    const cleanupTempFiles = () => {
+      for (const tempFile of tempFiles) tempFile.cleanup();
+    };
+    let sessionCopy: PiTempFile | null = null;
    let runtimeSession: PiRuntimeSession;
    try {
+      if (processCwd !== resumeConfig.cwd) {
+        sessionCopy = await createPiSessionCopy(sessionFile, processCwd);
+        tempFiles.push(sessionCopy);
+      }
      runtimeSession = await runtime.startSession(
        buildResumeStartInput({
          resumeConfig,
-          sessionFile,
+          processCwd,
+          sessionFile: sessionCopy?.path ?? sessionFile,
          launchContext,
          mcpConfigFile,
          paseoExtension,
        }),
      );
    } catch (error) {
-      mcpConfigFile?.cleanup();
-      paseoExtension?.cleanup();
+      cleanupTempFiles();
      throw error;
    }
    try {
@@ -2702,15 +2736,15 @@ export class PiRpcAgentClient implements AgentClient {
        },
        initialState,
        capabilities: capabilitiesForSession(mcp !== null),
-        cleanup: combineCleanup([mcpConfigFile?.cleanup, paseoExtension?.cleanup]),
+        persistedSessionFile: sessionCopy ? sessionFile : undefined,
+        cleanup: cleanupTempFiles,
        extensionTimeoutMs: providerOptions.extensionTimeoutMs,
        logger: this.logger,
        usagePollScheduler: this.usagePollScheduler,
      });
    } catch (error) {
      await runtimeSession.close().catch(() => undefined);
-      mcpConfigFile?.cleanup();
-      paseoExtension?.cleanup();
+      cleanupTempFiles();
      throw error;
    }
  }
@@ -1,9 +1,13 @@
-import { mkdtemp, mkdir, utimes, writeFile } from "node:fs/promises";
+import { mkdtemp, mkdir, readFile, rm, utimes, writeFile } from "node:fs/promises";
 import { tmpdir } from "node:os";
 import path from "node:path";
-import { expect, test } from "vitest";
+import { expect, onTestFinished, test } from "vitest";

-import { listPiImportableSessions, readPiImportSessionConfig } from "./session-descriptor.js";
+import {
+  copyPiSessionFileWithCwd,
+  listPiImportableSessions,
+  readPiImportSessionConfig,
+} from "./session-descriptor.js";

 async function writeSession(root: string, lines: unknown[]): Promise<string> {
  const sessionsDir = path.join(root, "sessions", "project");
@@ -216,3 +220,97 @@ test("Pi import config preserves thinking before a later model in large sessions
    thinkingOptionId: "low",
  });
 });
+
+test("a Pi session copy names the new cwd in its header and keeps every later byte", async () => {
+  const root = await mkdtemp(path.join(tmpdir(), "paseo-pi-session-copy-"));
+  onTestFinished(() => rm(root, { recursive: true, force: true }));
+  const header = {
+    type: "session",
+    version: 3,
+    id: "pi-session-1",
+    timestamp: "2026-01-01T00:00:00.000Z",
+    cwd: path.join(root, "removed-worktree"),
+  };
+  const body = Buffer.from(
+    Array.from(
+      { length: 2_000 },
+      (_, index) =>
+        `${JSON.stringify({ type: "message", id: `entry-${index}`, message: { role: "user", content: `café ☕ ${index}` } })}\n`,
+    ).join(""),
+  );
+  expect(body.length).toBeGreaterThan(64 * 1024);
+  const sourceFile = path.join(root, "source.jsonl");
+  const targetFile = path.join(root, "copy.jsonl");
+  await writeFile(sourceFile, Buffer.concat([Buffer.from(`${JSON.stringify(header)}\n`), body]));
+
+  await copyPiSessionFileWithCwd({ sourceFile, targetFile, cwd: "/home/user" });
+
+  const copy = await readFile(targetFile);
+  const headerEnd = copy.indexOf(0x0a);
+  expect(JSON.parse(copy.subarray(0, headerEnd).toString("utf8"))).toEqual({
+    ...header,
+    cwd: "/home/user",
+  });
+  expect(copy.subarray(headerEnd + 1).equals(body)).toBe(true);
+});
+
+test("a Pi session copy refuses a file without a session header", async () => {
+  const root = await mkdtemp(path.join(tmpdir(), "paseo-pi-session-copy-"));
+  onTestFinished(() => rm(root, { recursive: true, force: true }));
+  const sourceFile = path.join(root, "source.jsonl");
+  await writeFile(sourceFile, `${JSON.stringify({ type: "message", id: "entry-1" })}\n`);
+
+  await expect(
+    copyPiSessionFileWithCwd({ sourceFile, targetFile: path.join(root, "copy.jsonl"), cwd: "/" }),
+  ).rejects.toThrow(`Pi session file has no session header: ${sourceFile}`);
+});
+
+const COPY_BODY = [
+  { type: "message", id: "entry-1", message: { role: "user", content: "café ☕" } },
+  { type: "message", id: "entry-2", message: { role: "assistant", content: "Dans la cuisine." } },
+]
+  .map((entry) => `${JSON.stringify(entry)}\n`)
+  .join("");
+
+const COPY_HEADER = {
+  type: "session",
+  version: 3,
+  id: "pi-session-1",
+  timestamp: "2026-01-01T00:00:00.000Z",
+  cwd: "/removed-worktree",
+};
+
+async function copySessionContent(content: string): Promise<Buffer> {
+  const root = await mkdtemp(path.join(tmpdir(), "paseo-pi-session-copy-"));
+  onTestFinished(() => rm(root, { recursive: true, force: true }));
+  const sourceFile = path.join(root, "source.jsonl");
+  const targetFile = path.join(root, "copy.jsonl");
+  await writeFile(sourceFile, content);
+  await copyPiSessionFileWithCwd({ sourceFile, targetFile, cwd: "/home/user" });
+  return readFile(targetFile);
+}
+
+test.each([
+  ["a header line longer than 64 KiB", "", { ...COPY_HEADER, padding: "x".repeat(70 * 1024) }],
+  ["a header with an empty cwd", "", { ...COPY_HEADER, cwd: "" }],
+  ["blank lines before the header", "\n\r\n", COPY_HEADER],
+])("a Pi session copy accepts %s", async (_headerShape, prefix, header) => {
+  const copy = await copySessionContent(`${prefix}${JSON.stringify(header)}\n${COPY_BODY}`);
+
+  const headerEnd = copy.indexOf(0x0a);
+  expect(JSON.parse(copy.subarray(0, headerEnd).toString("utf8"))).toEqual({
+    ...header,
+    cwd: "/home/user",
+  });
+  expect(copy.subarray(headerEnd + 1).equals(Buffer.from(COPY_BODY))).toBe(true);
+});
+
+test("a Pi session copy reports a missing session file", async () => {
+  const root = await mkdtemp(path.join(tmpdir(), "paseo-pi-session-copy-"));
+  onTestFinished(() => rm(root, { recursive: true, force: true }));
+  const sourceFile = path.join(root, "missing.jsonl");
+
+  await expect(
+    copyPiSessionFileWithCwd({ sourceFile, targetFile: path.join(root, "copy.jsonl"), cwd: "/" }),
+  ).rejects.toThrow(`Pi session file is missing: ${sourceFile}`);
+});
@@ -1,7 +1,8 @@
-import type { Dirent } from "node:fs";
-import { open, readdir, readFile, stat } from "node:fs/promises";
+import { createReadStream, createWriteStream, type Dirent } from "node:fs";
+import { open, readdir, readFile, stat, writeFile } from "node:fs/promises";
 import { homedir } from "node:os";
 import path from "node:path";
+import { pipeline } from "node:stream/promises";

 import type {
  ImportableProviderSession,
@@ -18,6 +19,7 @@ const PI_SESSION_DIR_ENV = "PI_CODING_AGENT_SESSION_DIR";
 const HEAD_BYTES = 64 * 1024;
 const TAIL_BYTES = 256 * 1024;
 const FULL_SCAN_LINE_LIMIT = 2_000;
+const PI_SESSION_HEADER_SCAN_BYTES = 1024 * 1024;
 // Rank all discovered files cheaply, then parse only a bounded recent window.
 const IMPORT_CANDIDATE_OVERSCAN = 40;
 const IMPORT_CANDIDATE_MIN = 400;
@@ -100,6 +102,59 @@ export async function listPiImportableSessions(
  );
 }

+export async function copyPiSessionFileWithCwd(input: {
+  sourceFile: string;
+  targetFile: string;
+  cwd: string;
+}): Promise<void> {
+  const found = findSessionHeaderLine(
+    await readSessionFileStart(input.sourceFile, PI_SESSION_HEADER_SCAN_BYTES),
+  );
+  if (!found) {
+    throw new Error(`Pi session file has no session header: ${input.sourceFile}`);
+  }
+  await writeFile(input.targetFile, `${JSON.stringify({ ...found.header, cwd: input.cwd })}\n`, {
+    mode: 0o600,
+  });
+  await pipeline(
+    createReadStream(input.sourceFile, { start: found.bodyStart }),
+    createWriteStream(input.targetFile, { flags: "a" }),
+  );
+}
+
+function findSessionHeaderLine(
+  scanned: Buffer,
+): { header: Record<string, unknown>; bodyStart: number } | null {
+  let lineStart = 0;
+  while (lineStart < scanned.length) {
+    const newline = scanned.indexOf(0x0a, lineStart);
+    const bodyStart = newline === -1 ? scanned.length : newline + 1;
+    const line = scanned.subarray(lineStart, bodyStart).toString("utf8").trim();
+    if (line) {
+      const header = parseJsonRecord(line);
+      return header?.type === "session" ? { header, bodyStart } : null;
+    }
+    lineStart = bodyStart;
+  }
+  return null;
+}
+
+async function readSessionFileStart(filePath: string, maxBytes: number): Promise<Buffer> {
+  const handle = await open(filePath, "r").catch((error: unknown) => {
+    if ((error as NodeJS.ErrnoException).code === "ENOENT") {
+      throw new Error(`Pi session file is missing: ${filePath}`);
+    }
+    throw error;
+  });
+  try {
+    const buffer = Buffer.alloc(maxBytes);
+    const { bytesRead } = await handle.read(buffer, 0, maxBytes, 0);
+    return buffer.subarray(0, bytesRead);
+  } finally {
+    await handle.close().catch(() => undefined);
+  }
+}
+
 export async function readPiImportSessionConfig(filePath: string): Promise<PiImportSessionConfig> {
  const descriptor = await readPiSessionDescriptor(filePath);
  if (!descriptor) return {};
@@ -1,3 +1,5 @@
+import { existsSync, readFileSync } from "node:fs";
+
 import type {
  PiRuntime,
  PiRuntimeLaunch,
@@ -75,6 +77,12 @@ export class FakePi implements PiRuntime {
    const session = new FakePiSession(launch, this.removedModels);
    session.commands = this.queuedCommands.shift() ?? [];
    this.queuedSessionSetups.shift()?.(session);
+    const missingSessionCwd = launch.noSession ? null : readMissingSessionCwd(launch.session);
+    if (missingSessionCwd !== null) {
+      session.getStateError = new Error(
+        `Pi RPC process exited with code 1 and signal null\nStored session working directory does not exist: ${missingSessionCwd}\nSession file: ${launch.session}\nCurrent working directory: ${launch.cwd}`,
+      );
+    }
    this.sessions.push(session);
    return session;
  }
@@ -101,6 +109,27 @@ export class FakePi implements PiRuntime {
  }
 }

+function readMissingSessionCwd(sessionFile: string | undefined): string | null {
+  if (!sessionFile || !existsSync(sessionFile)) {
+    return null;
+  }
+  const [headerLine = ""] = readFileSync(sessionFile, "utf8").split("\n", 1);
+  let header: unknown;
+  try {
+    header = JSON.parse(headerLine);
+  } catch {
+    return null;
+  }
+  if (typeof header !== "object" || header === null || !("cwd" in header)) {
+    return null;
+  }
+  const { type, cwd } = header as { type?: unknown; cwd?: unknown };
+  if (type !== "session" || typeof cwd !== "string" || !cwd || existsSync(cwd)) {
+    return null;
+  }
+  return cwd;
+}
+
 export class FakePiSession implements PiRuntimeSession {
  readonly environment: Record<string, string>;
  readonly prompts: Array<{ message: string; imageCount: number }> = [];
@@ -0,0 +1,26 @@
+import { stat } from "node:fs/promises";
+import { homedir } from "node:os";
+
+import type { AgentResumePurpose } from "../agent-sdk-types.js";
+
+export async function resolveResumeProcessCwd(
+  cwd: string,
+  purpose: AgentResumePurpose | undefined,
+): Promise<string> {
+  if (purpose !== "history" || (await isDirectory(cwd))) {
+    return cwd;
+  }
+  return homedir();
+}
+
+async function isDirectory(target: string): Promise<boolean> {
+  try {
+    return (await stat(target)).isDirectory();
+  } catch (error) {
+    const code = (error as NodeJS.ErrnoException).code;
+    if (code === "ENOENT" || code === "ENOTDIR") {
+      return false;
+    }
+    throw error;
+  }
+}
@@ -410,7 +410,12 @@ describe("createTerminal", () => {
          cwd: realpathSync(tmpdir()),
          cols: 500,
          command: process.execPath,
-          args: ["-e", "process.stdout.write(JSON.stringify(process.argv.slice(1)))", nastyPrompt],
+          // Keep the PTY alive until the screen assertion; exit disposes its parser.
+          args: [
+            "-e",
+            "process.stdout.write(JSON.stringify(process.argv.slice(1))); setInterval(() => {}, 100000)",
+            nastyPrompt,
+          ],
        }),
      );