fix(pairing): avoid duplicate pending requests

conftest.py

@@ -49,6 +49,16 @@ def _isolate_sessions_root(tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> I
     yield
 
 
+@pytest.fixture(autouse=True)
+def _isolate_pairing_store(tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+    """Keep channel pairing tests out of the user's active pairing store."""
+    pairing_path = tmp_path / "pairing.json"
+    monkeypatch.setattr(
+        "nanobot.pairing.store._store_path",
+        lambda: pairing_path,
+    )
+
+
 @pytest.fixture(scope="session", autouse=True)
 def _use_windows_system_ca_for_default_http_clients() -> Iterator[None]:
     """Avoid reparsing certifi's CA bundle for every offline HTTP client.

nanobot/pairing/store.py

@@ -115,19 +115,24 @@ def generate_code(
     sender_id: str,
     ttl: int = _TTL_DEFAULT_S,
 ) -> str:
-    """Create a new pairing code for *sender_id* on *channel*.
+    """Return an active pairing code for *sender_id* on *channel*.
 
     Returns the code (e.g. ``"ABCD-EFGH"``).
     """
     with _LOCK:
         data = _load()
         _gc_pending(data)
+        sender = str(sender_id)
+        for code, info in data.get("pending", {}).items():
+            if info["channel"] == channel and str(info["sender_id"]) == sender:
+                return code
+
         raw = "".join(secrets.choice(_ALPHABET) for _ in range(_CODE_LENGTH))
         code = f"{raw[:4]}-{raw[4:]}"
 
         data.setdefault("pending", {})[code] = {
             "channel": channel,
-            "sender_id": str(sender_id),
+            "sender_id": sender,
             "created_at": time.time(),
             "expires_at": time.time() + ttl,
         }

tests/pairing/test_store.py

@@ -32,6 +32,19 @@ class TestGenerateCode:
         codes = {store.generate_code("telegram", str(i)) for i in range(20)}
         assert len(codes) == 20
 
+    def test_reuses_active_code_for_same_sender(self) -> None:
+        first = store.generate_code("telegram", "123")
+
+        assert store.generate_code("telegram", "123") == first
+        assert len(store.list_pending()) == 1
+
+    def test_scopes_reused_codes_to_channel(self) -> None:
+        telegram = store.generate_code("telegram", "123")
+        discord = store.generate_code("discord", "123")
+
+        assert telegram != discord
+        assert len(store.list_pending()) == 2
+
     def test_ttl_expiration(self, monkeypatch) -> None:
         clock = {"now": 1_000.0}
         monkeypatch.setattr(store.time, "time", lambda: clock["now"])