fix(lark): isolate Agent Goal Channel binding resolution

loopx/extensions/lark/goal_channel_contracts.py

@@ -216,40 +216,50 @@ def binding_for_goal(
     agent_id: str | None = None,
     connection_id: str | None = None,
 ) -> dict[str, Any] | None:
-    candidates = bindings_for_goal(
-        payload,
-        goal_id,
-        provider_target=provider_target,
-    )
+    # Select one raw connection before resolving its provider target. A target
+    # belongs to one connection; applying it to every sibling lets an unrelated
+    # Agent's target invalidate the requested Agent's otherwise valid binding.
+    candidates = bindings_for_goal(payload, goal_id)
+    selected: dict[str, Any] | None = None
     if connection_id:
-        return next(
+        selected = next(
             (item for item in candidates if item.get("connection_id") == connection_id),
             None,
         )
-    if agent_id is not None:
-        return next(
+    elif agent_id is not None:
+        selected = next(
             (item for item in candidates if item.get("agent_id") == agent_id),
             None,
         )
-    bindings = payload.get("bindings")
-    stored = bindings.get(goal_id) if isinstance(bindings, Mapping) else None
-    default_id = (
-        str(stored.get("default_connection_id") or "")
-        if isinstance(stored, Mapping)
-        else ""
-    )
-    if default_id:
-        selected = next(
-            (item for item in candidates if item.get("connection_id") == default_id),
-            None,
+    else:
+        bindings = payload.get("bindings")
+        stored = bindings.get(goal_id) if isinstance(bindings, Mapping) else None
+        default_id = (
+            str(stored.get("default_connection_id") or "")
+            if isinstance(stored, Mapping)
+            else ""
         )
-        if selected is not None:
-            return selected
-    # Keep the invalid-default fallback aligned with the writer in
-    # _without_goal_topic_connection, which promotes min(connection_id).
-    if not candidates:
-        return None
-    return min(candidates, key=lambda item: str(item.get("connection_id") or ""))
+        if default_id:
+            selected = next(
+                (
+                    item
+                    for item in candidates
+                    if item.get("connection_id") == default_id
+                ),
+                None,
+            )
+        if selected is None and candidates:
+            # Keep the invalid-default fallback aligned with the writer in
+            # _without_goal_topic_connection, which promotes min(connection_id).
+            selected = min(
+                candidates,
+                key=lambda item: str(item.get("connection_id") or ""),
+            )
+    return (
+        _resolve_goal_binding(selected, provider_target=provider_target)
+        if selected is not None
+        else None
+    )
 
 
 def human_gate_auto_notify_enabled(binding: Mapping[str, Any] | None) -> bool:

tests/extensions/test_lark_goal_channel_binding_isolation.py

@@ -0,0 +1,62 @@
+from __future__ import annotations
+
+import pytest
+
+from loopx.extensions.lark.goal_channel_contracts import binding_for_goal
+
+
+def _connection(agent_id: str, target_ref: str) -> dict[str, object]:
+    return {
+        "goal_id": "goal-alpha",
+        "agent_id": agent_id,
+        "provider": "lark",
+        "enabled": True,
+        "target_ref": target_ref,
+        "channel": {},
+    }
+
+
+def _target(name: str, chat_id: str) -> dict[str, object]:
+    return {
+        "name": name,
+        "provider": "lark",
+        "channel": {"chat_id": chat_id},
+        "identity": {
+            "mode": "project_bot",
+            "sender_identity": "bot",
+            "sender_profile": f"{name}-profile",
+        },
+    }
+
+
+def test_binding_resolution_isolates_selected_agent_from_sibling_target() -> None:
+    payload = {
+        "bindings": {
+            "goal-alpha": {
+                "schema_version": "loopx_goal_channel_connection_set_v0",
+                "default_connection_id": "connection-alpha",
+                "connections": {
+                    "connection-alpha": _connection("agent-alpha", "target-alpha"),
+                    "connection-beta": _connection("agent-beta", "target-beta"),
+                },
+            }
+        }
+    }
+
+    alpha = binding_for_goal(
+        payload,
+        "goal-alpha",
+        connection_id="connection-alpha",
+        provider_target=_target("target-alpha", "oc_alpha"),
+    )
+
+    assert alpha is not None
+    assert alpha["agent_id"] == "agent-alpha"
+    assert alpha["channel"] == {"chat_id": "oc_alpha"}
+    with pytest.raises(ValueError, match="does not match target_ref"):
+        binding_for_goal(
+            payload,
+            "goal-alpha",
+            connection_id="connection-beta",
+            provider_target=_target("target-alpha", "oc_alpha"),
+        )