vercel/ai · error

The installed ACP SDK cannot send session prompt metadata wh

Error message

The installed ACP SDK cannot send session prompt metadata while preserving streamed updates.

What it means

Error "The installed ACP SDK cannot send session prompt metadata while preserving streamed updates." thrown in vercel/ai.

Source

Thrown at packages/harness-acp/src/v1/bridge/index.ts:824

  agent: acp.ClientContext;
  prompt: Array<acp.ContentBlock>;
  meta: Record<string, unknown> | undefined;
}): Promise<acp.PromptResponse> {
  if (meta == null) return session.prompt(prompt);
  if (session.promptWithMeta != null) {
    return session.promptWithMeta({ prompt, meta });
  }
  const updates = (
    session as unknown as {
      updates?: {
        clearErrors(): void;
        enqueue(value: acp.ActiveSessionMessage): void;
        reject(error: unknown): void;
      };
    }
  ).updates;
  if (updates == null) {
    throw new Error(
      'The installed ACP SDK cannot send session prompt metadata while preserving streamed updates.',
    );
  }
  updates.clearErrors();
  const response = agent.request<acp.PromptResponse, acp.PromptRequest>(
    acp.methods.agent.session.prompt,
    {
      sessionId: session.sessionId,
      prompt,
      _meta: meta,
    },
  );
  void response.then(
    value => {
      updates.enqueue({
        kind: 'stop',
        response: value,
        stopReason: value.stopReason,

View on GitHub (pinned to 69428b1f8b)

When it happens

Trigger: Thrown at packages/harness-acp/src/v1/bridge/index.ts:824 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/6aca886bd358a3c3. Report an issue: GitHub.