vercel/ai · error · CodeModeProtocolError

CODE_MODE_PROTOCOL_ERROR

CODE_MODE_PROTOCOL_ERROR

Error message

Tool "${toolName}" approval callback returned a malformed approval decision.

What it means

Error "Tool "${toolName}" approval callback returned a malformed approval decision." thrown in vercel/ai.

Source

Thrown at packages/code-mode/src/tool-invocation.ts:131

          toolCallId,
        }),
      ),
      baseExecutionOptions.abortSignal,
    );
    if (approval === undefined) {
      throw new CodeModeToolApprovalRequiredError(
        toolName,
        validation.value,
        toolCallId,
      );
    }
    const approved =
      typeof approval === 'string'
        ? approval === 'approved'
        : approval?.approved;
    const reason = typeof approval === 'string' ? undefined : approval?.reason;
    if (typeof approved !== 'boolean') {
      throw new CodeModeProtocolError(
        `Tool "${toolName}" approval callback returned a malformed approval decision.`,
        { toolName, toolCallId },
      );
    }
    if (reason !== undefined && typeof reason !== 'string') {
      throw new CodeModeProtocolError(
        `Tool "${toolName}" approval callback returned a malformed approval reason.`,
        { toolName, toolCallId },
      );
    }
    if (!approved) {
      throw new CodeModeToolApprovalDeniedError(
        toolName,
        validation.value,
        toolCallId,
        reason,
      );
    }

View on GitHub (pinned to 69428b1f8b)

When it happens

Trigger: Thrown at packages/code-mode/src/tool-invocation.ts:131 when the library encounters an invalid state.

Common situations: See trigger scenarios.

Understand the failure class

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

AI-assisted analysis of vercel/ai@69428b1f8b (2026-08-30). Data as JSON: /api/errors/d870dfe39c0c21f3. Report an issue: GitHub.