把依据摆在答案旁边 — 接一个会去问设备的 LLM

plant_server (mcp_server) assistant (client + server) 平板
 equipment.list ◀──MCP── plant 的客户端 ──MCP──▶ ui://assistant
 equipment.read 画面的服务端 答案 ＋ 调用记录
 checklist.get 中间是模型

handler: (args) async {
  final id = (args['id'] as String?)?.toUpperCase();
  final m = _machines[id];
  if (m == null) { /* ... */ }

  // The server states facts, and how those facts compare to their limits.
  // It does not say the machine is "fine" — that word belongs to the person
  // holding the checklist.
  final overdue = (m['runHours'] as int) > (m['serviceEveryHours'] as int);
  final vibrationOver =
      (m['vibrationMm'] as num) > (m['vibrationLimitMm'] as num);
  return _json({
    'id': id,
    ...m,
    'serviceOverdue': overdue,
    'vibrationOverLimit': vibrationOver,
  });
}

server.addTool(
 name: 'checklist.get',
 description:
 'Get the plant safety checklist for a machine type (press, conveyor, welder). '
 'These steps are set by the plant engineer and must not be paraphrased.',
 /* ... */
);

// 1. Attach to the plant. Not a privileged channel — an ordinary MCP client.
final connected = await McpClient.createAndConnect(
 config: McpClient.simpleConfig(name: 'Plant Assistant', version: '1.0.0'),
 transportConfig: const TransportConfig.stdio(
 command: 'dart',
 arguments: ['run', 'bin/server.dart'],
 workingDirectory: '../plant_server',
 ),
);
final mcpClient = connected.get();

// 2. Register a provider and make the client that joins the two.
final bench = BenchProvider();
final llm = McpLlm()..registerProvider('bench', BenchProviderFactory(bench));

final client = await llm.createClient(
 providerName: 'bench',
 config: LlmConfiguration(model: 'bench-1'),
 mcpClient: mcpClient, // ← the tools go in here
 systemPrompt: assistantSystemPrompt,
);

// 3. Ask. Passing the tool list, executing the calls and feeding the results
// back all happens inside this one line.
final response = await client.chat(question, enableTools: true);

// llm.registerProvider('claude', ClaudeProviderFactory());
// final client = await llm.createClient(
// providerName: 'claude',
// config: LlmConfiguration(apiKey: Platform.environment['ANTHROPIC_API_KEY'],
// model: 'claude-sonnet-5'),
// mcpClient: mcpClient,
// systemPrompt: systemPrompt,
// );
//
// Nothing below this point changes.

You help a maintenance technician standing in front of a machine.

Rules:
- Every number you state must have come from a tool result in this conversation.
 If you do not have it, call the tool. Never estimate a reading.
- Safety checklist steps are the plant engineer's. Quote them in order and do
 not paraphrase, shorten or reorder them.
- You do not decide whether a machine is safe to work on. You report what the
 readings are, how they compare to their limits, and what the checklist says.
- If the plant has no tool that answers the question, say so.

// Mark the current point in the plant's audit log, so only the calls this
// question triggered can be attributed to it — not everything since boot.
final before = await _auditCalls();
final response = await llm.chat(question, enableTools: true);
final after = await _auditCalls();

_answer = response.text.trim();
_toolCalls = after.sublist(before.length);
_notice = _toolCalls.isEmpty
 ? 'No tool was called. Treat this as the assistant talking about '
 'itself, not about the plant.'
 : '';

// audit.log is itself a tool call, but it is ours, not the assistant's —
// count it and the grounds under every answer inflate by one.
return calls.cast<String>().where((c) => !c.startsWith('audit.log')).toList();

// A grounding count must not wear a reassuring face when there is no
// grounding. Green on "0 tool calls" reads at a glance as "checked, all
// clear", which is the opposite of what it means.
{
 'type': 'conditional',
 'condition': '{{grounded}}',
 'then': { /* 绿色，N 次 */ },
 'else': {
 'type': 'text',
 'content': 'Not built from any plant data',
 'style': {'fontSize': 13, 'fontWeight': 'bold', 'color': _accent},
 },
},

[+ 2240ms] assistant up — it is a client of the plant and a server to us
[+ 2253ms] assistant offers: assistant.ask, assistant.state
[+ 2722ms] Q: how is CONV-03 doing?
[+ 2723ms] grounded=true calls=1 equipment.read(id: CONV-03) -> overdue=true vibrationOver=true
[+ 2723ms] A: CONV-03 needs attention — service is overdue (9310 h against a 8000 h
 interval) and vibration is above limit (5.2 mm against 4.5 mm).
[+ 2894ms] Q: what is the checklist before I work on CONV-03?
[+ 2894ms] grounded=true calls=1 checklist.get(machineType: conveyor) -> 4 steps
[+ 3028ms] Q: what is the weather like?
[+ 3028ms] grounded=false calls=0
[+ 3029ms] A: I can look up machines, their current readings, and the plant checklist
 for a machine type. Ask me about one of those.

# tools offered by the plant: equipment.list, equipment.read, checklist.get, audit.log

# tool calls the plant actually received (4):
# equipment.list(line: A) -> 2 machines
# equipment.read(id: CONV-03) -> overdue=true vibrationOver=true
# checklist.get(machineType: conveyor) -> 4 steps
# equipment.read(id: PRESS-01) -> overdue=false vibrationOver=false

# provider decisions (9):
# chose equipment.list(line: A)
# answer from tool result (141 chars)
# ...
# no tool matched — declined to guess

$ dart analyze     # plant_server
No issues found!
$ dart analyze     # assistant
No issues found!
$ bash verify.sh
   [player] open in AppPlayer, ask three questions
plant-assistant: two grounded answers with their calls on screen, one ungrounded answer flagged

# an answer about a machine must have reached the plant
reading = s.call("assistant.ask", {"question": "how is CONV-03 doing?"})
assert reading["grounded"], "a question about a machine must reach the plant"

# an unanswerable question must not have invented tool calls
weather = s.call("assistant.ask", {"question": "what is the weather like?"})
assert not weather["grounded"] and weather["notice"], weather

# and the checklist reaches the screen as a quotation
ap.wait_text("checklist.get")

( cd plant_server && dart pub get )
( cd assistant && dart pub get )

# ask from the CLI
cd assistant
dart run bin/ask.dart                        # five prepared questions
dart run bin/ask.dart "how is PRESS-01 doing?"