MCP tools crash: TypeError on value.output.output in processor.ts (AI SDK 6.0.74 breaking change) #13042

value.output = {
  output: string,
  metadata: Record<string, any>,
  title: string,
  attachments?: FilePart[]
}

value.output = {
  type: 'text' | 'json' | 'error-text' | 'error-json' | 'execution-denied' | 'content',
  value: string | JSONValue,
  providerOptions?: ProviderOptions
}

case "tool-result": {
  const match = toolcalls[value.toolCallId]
  if (match && match.state.status === "running") {
    await Session.updatePart({
      ...match,
      state: {
        status: "completed",
        input: value.input ?? match.state.input,
        output: value.output.output,       // ← undefined.toLowerCase() crashes here
        metadata: value.output.metadata,   // ← undefined
        title: value.output.title,         // ← undefined
        attachments: value.output.attachments,
      },
    })
  }
}

// In convertMcpTool(), wrap the execute return:
execute: async (args: unknown) => {
  const result = await client.callTool(...)
  const textContent = result.content
    ?.filter((c: any) => c.type === "text")
    .map((c: any) => c.text)
    .join("\n") ?? ""
  return {
    output: textContent,
    title: mcpTool.name,
    metadata: {},
  }
},

case "tool-result": {
  const match = toolcalls[value.toolCallId]
  if (match && match.state.status === "running") {
    const raw = value.output ?? {}
    // Handle both old format { output, metadata, title } and new AI SDK format { type, value }
    const output = raw.output ?? raw.value ?? (typeof raw === "string" ? raw : JSON.stringify(raw))
    const metadata = raw.metadata ?? {}
    const title = raw.title ?? match.tool
    await Session.updatePart({
      ...match,
      state: {
        status: "completed",
        input: value.input ?? match.state.input,
        output,
        metadata,
        title,
        time: { start: match.state.time.start, end: Date.now() },
        attachments: raw.attachments,
      },
    })
  }
}