vercel/ai · error

Pi private session directory ${JSON.stringify(privateSession

Error message

Pi private session directory ${JSON.stringify(privateSessionDir)} must be outside sessionWorkDir ${JSON.stringify(input.sessionWorkDir)}.

What it means

The adapter computes a private directory under the sandbox HOME where Pi session files are stored, and verifies that it does not live inside the agent's session work directory (so session state never leaks into the agent workspace). It throws when the private dir resolves to, or inside, sessionWorkDir. This is a configuration-invariant failure of resolvePiPrivateSessionDirectory.

Source

Thrown at packages/harness-pi/src/pi-resume-state.ts:56

  readonly sessionWorkDir: string;
  readonly sessionId: string;
}): string {
  const sessionKey = createHash('sha256').update(input.sessionId).digest('hex');
  const privateSessionDir = path.posix.join(
    input.sandboxHomeDir,
    '.ai-sdk',
    'harness-pi',
    sessionKey,
  );
  const relativePath = path.posix.relative(
    input.sessionWorkDir,
    privateSessionDir,
  );
  if (
    relativePath === '' ||
    (!relativePath.startsWith('../') && !path.posix.isAbsolute(relativePath))
  ) {
    throw new Error(
      `Pi private session directory ${JSON.stringify(privateSessionDir)} must be outside sessionWorkDir ${JSON.stringify(input.sessionWorkDir)}.`,
    );
  }
  return privateSessionDir;
}

function resolveContainedHostPath(input: {
  readonly baseDir: string;
  readonly sessionFileName: string;
}): string {
  const baseDir = path.resolve(input.baseDir);
  const filePath = path.resolve(
    baseDir,
    safePiSessionFileName(input.sessionFileName),
  );
  const relativePath = path.relative(baseDir, filePath);
  if (
    relativePath === '' ||

View on GitHub (pinned to 69428b1f8b)

Solutions

1. Move sessionWorkDir to a dedicated agent workspace directory that is not inside sandboxHomeDir
2. Ensure sandboxHomeDir is not a parent (or equal) of sessionWorkDir
3. If using defaults, do not override sessionWorkDir to point under the home directory

Example fix

// before
resolvePiPrivateSessionDirectory({
  sandboxHomeDir: '/home/agent',
  sessionWorkDir: '/home/agent', // collides: private dir is inside work dir
  sessionId,
});
// after
resolvePiPrivateSessionDirectory({
  sandboxHomeDir: '/home/agent',
  sessionWorkDir: '/home/agent/workspace', // outside the state path
  sessionId,
});

import path from 'node:path';
export function assertWorkDirOutsideHome(sandboxHomeDir: string, sessionWorkDir: string): void {
  const rel = path.posix.relative(sessionWorkDir, path.posix.join(sandboxHomeDir, '.ai-sdk'));
  if (rel === '' || (!rel.startsWith('../') && !path.posix.isAbsolute(rel))) {
    throw new Error('sessionWorkDir must not overlap the sandbox home .ai-sdk directory');
  }
}

When it happens

Trigger: Calling resolvePiPrivateSessionDirectory (directly or via resume lifecycle code) with a sandboxHomeDir laid out such that `<sandboxHomeDir>/.ai-sdk/harness-pi/<hash>` equals or is nested within the given sessionWorkDir — e.g. sessionWorkDir set to the sandbox home itself, to `<home>/.ai-sdk`, or to `<home>/.ai-sdk/harness-pi`.

Common situations: Misconfiguring the sandbox so the agent workspace and sandbox HOME point at the same directory, or intentionally pointing sessionWorkDir at the home dir to 'simplify' pathing; also occurs when a custom sessionWorkDir overlaps the .ai-sdk state folder.

Related errors

• Invalid argument for parameter model: model ${model.provider
• The Claude Code harness cannot use `mintBridgeToken` with a
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• The Claude Code harness requires an explicit `portEndpoint`
• Cline private session directory ${JSON.stringify(privateSess

AI-assisted analysis of vercel/ai@69428b1f8b (2026-08-30). Data as JSON: /api/errors/32b640027e1da0cf. Report an issue: GitHub.