vercel/ai · error · Error

ACP lossy rerun requires the same active host tool catalog a

Error message

ACP lossy rerun requires the same active host tool catalog as the original turn.

What it means

Error "ACP lossy rerun requires the same active host tool catalog as the original turn." thrown in vercel/ai.

Source

Thrown at packages/harness-acp/src/v1/acp-v1-harness.ts:1855

    throw new Error(
      'ACP cold-session state is incompatible with the current non-secret session configuration.',
    );
  }
  return current;
}

function assertRecoveryToolCatalog({
  persisted,
  current,
}: {
  persisted: ReadonlyArray<HarnessV1ToolSpec>;
  current: ReadonlyArray<HarnessV1ToolSpec>;
}): void {
  if (
    fingerprintValue({ value: persisted }) !==
    fingerprintValue({ value: current })
  ) {
    throw new Error(
      'ACP lossy rerun requires the same active host tool catalog as the original turn.',
    );
  }
}

function fingerprintValue({ value }: { value: unknown }): string {
  return createHash('sha256').update(JSON.stringify(value)).digest('hex');
}

function isRecord(value: unknown): value is Record<string, unknown> {
  return value != null && typeof value === 'object' && !Array.isArray(value);
}

function unsupported({
  harnessId,
  message,
  cause,
}: {

View on GitHub (pinned to 69428b1f8b)

When it happens

Trigger: Thrown at packages/harness-acp/src/v1/acp-v1-harness.ts:1855 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of vercel/ai@69428b1f8b (2026-08-30). Data as JSON: /api/errors/da9b8ce9e50f0ba2. Report an issue: GitHub.