refactor: organize agent harness courses

learn-claude-code/docs/en/s09-agent-teams.md

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+# s09: Agent Teams
+
+`s01 > s02 > s03 > s04 > s05 > s06 | s07 > s08 > [ s09 ] s10 > s11 > s12`
+
+> *"When the task is too big for one, delegate to teammates"* -- persistent teammates + async mailboxes.
+>
+> **Harness layer**: Team mailboxes -- multiple models, coordinated through files.
+
+## Problem
+
+Subagents (s04) are disposable: spawn, work, return summary, die. No identity, no memory between invocations. Background tasks (s08) run shell commands but can't make LLM-guided decisions.
+
+Real teamwork needs: (1) persistent agents that outlive a single prompt, (2) identity and lifecycle management, (3) a communication channel between agents.
+
+## Solution
+
+```
+Teammate lifecycle:
+  spawn -> WORKING -> IDLE -> WORKING -> ... -> SHUTDOWN
+
+Communication:
+  .team/
+    config.json           <- team roster + statuses
+    inbox/
+      alice.jsonl         <- append-only, drain-on-read
+      bob.jsonl
+      lead.jsonl
+
+              +--------+    send("alice","bob","...")    +--------+
+              | alice  | -----------------------------> |  bob   |
+              | loop   |    bob.jsonl << {json_line}    |  loop  |
+              +--------+                                +--------+
+                   ^                                         |
+                   |        BUS.read_inbox("alice")          |
+                   +---- alice.jsonl -> read + drain ---------+
+```
+
+## How It Works
+
+1. TeammateManager maintains config.json with the team roster.
+
+```python
+class TeammateManager:
+    def __init__(self, team_dir: Path):
+        self.dir = team_dir
+        self.dir.mkdir(exist_ok=True)
+        self.config_path = self.dir / "config.json"
+        self.config = self._load_config()
+        self.threads = {}
+```
+
+2. `spawn()` creates a teammate and starts its agent loop in a thread.
+
+```python
+def spawn(self, name: str, role: str, prompt: str) -> str:
+    member = {"name": name, "role": role, "status": "working"}
+    self.config["members"].append(member)
+    self._save_config()
+    thread = threading.Thread(
+        target=self._teammate_loop,
+        args=(name, role, prompt), daemon=True)
+    thread.start()
+    return f"Spawned teammate '{name}' (role: {role})"
+```
+
+3. MessageBus: append-only JSONL inboxes. `send()` appends a JSON line; `read_inbox()` reads all and drains.
+
+```python
+class MessageBus:
+    def send(self, sender, to, content, msg_type="message", extra=None):
+        msg = {"type": msg_type, "from": sender,
+               "content": content, "timestamp": time.time()}
+        if extra:
+            msg.update(extra)
+        with open(self.dir / f"{to}.jsonl", "a") as f:
+            f.write(json.dumps(msg) + "\n")
+
+    def read_inbox(self, name):
+        path = self.dir / f"{name}.jsonl"
+        if not path.exists(): return "[]"
+        msgs = [json.loads(l) for l in path.read_text().strip().splitlines() if l]
+        path.write_text("")  # drain
+        return json.dumps(msgs, indent=2)
+```
+
+4. Each teammate checks its inbox before every LLM call, injecting received messages into context.
+
+```python
+def _teammate_loop(self, name, role, prompt):
+    messages = [{"role": "user", "content": prompt}]
+    for _ in range(50):
+        inbox = BUS.read_inbox(name)
+        if inbox != "[]":
+            messages.append({"role": "user",
+                "content": f"<inbox>{inbox}</inbox>"})
+        response = client.messages.create(...)
+        if response.stop_reason != "tool_use":
+            break
+        # execute tools, append results...
+    self._find_member(name)["status"] = "idle"
+```
+
+## What Changed From s08
+
+| Component      | Before (s08)     | After (s09)                |
+|----------------|------------------|----------------------------|
+| Tools          | 6                | 9 (+spawn/send/read_inbox) |
+| Agents         | Single           | Lead + N teammates         |
+| Persistence    | None             | config.json + JSONL inboxes|
+| Threads        | Background cmds  | Full agent loops per thread|
+| Lifecycle      | Fire-and-forget  | idle -> working -> idle    |
+| Communication  | None             | message + broadcast        |
+
+## Try It
+
+```sh
+cd learn-claude-code
+python agents/s09_agent_teams.py
+```
+
+1. `Spawn alice (coder) and bob (tester). Have alice send bob a message.`
+2. `Broadcast "status update: phase 1 complete" to all teammates`
+3. `Check the lead inbox for any messages`
+4. Type `/team` to see the team roster with statuses
+5. Type `/inbox` to manually check the lead's inbox