diff --git a/.trae/rules/project_rules.md b/.trae/rules/project_rules.md
new file mode 100644
index 0000000..b749419
--- /dev/null
+++ b/.trae/rules/project_rules.md
@@ -0,0 +1,39 @@
+# Project Rules
+
+## Python Async Generator Safety
+
+When writing async generator functions (async def with yield), NEVER use early `return` before the first `yield`. This causes Python to treat the function as a coroutine instead of an async generator, resulting in `'async for' requires an object with __aiter__ method, got coroutine` errors at runtime.
+
+**Wrong:**
+```python
+async def subscribe(self):
+    if self._closed:
+        return  # BUG: makes this a coroutine when _closed=True
+    ...
+    yield event
+```
+
+**Correct — use `return; yield` pattern:**
+```python
+async def subscribe(self):
+    if self._closed:
+        return
+        yield  # Makes this always an async generator
+    ...
+    yield event
+```
+
+**Correct — restructure to avoid early return:**
+```python
+async def subscribe(self):
+    if not self._closed:
+        ...
+        yield event
+```
+
+This applies to ALL async generator functions in the codebase. When adding an early exit path to any `async def` that contains `yield`, always ensure the `yield` is reachable or add a `return; yield` guard.
+
+## Testing
+
+- Run `python3 -m pytest tests/unit/ -x -q` before committing
+- Known failing test (unrelated): `test_rewoo_agent_yaml_loads` — skip if needed
diff --git a/AGENTS.md b/AGENTS.md
index dac2acc..383ae87 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -10,6 +10,7 @@
 - Expert names validated with `_EXPERT_NAME_RE = re.compile(r"^[a-zA-Z0-9_-]{1,64}$")`
 - HandoffTransport queues bounded (`maxsize=1024`), close uses sentinel pattern
 - Frontend: Vue 3 + TypeScript + Ant Design Vue, Pinia stores, no `require()` calls
+- **Async generator safety**: Never use early `return` before the first `yield` in `async def` — use `return; yield` pattern instead (see `.trae/rules/project_rules.md`)
 
 ## Tech Stack