fix: eager binding in from_json prevents cross-chat resolution (P1)

When deserializing via activate() or global singleton (no explicit
chat= parameter), from_json now eagerly binds adapter and state from
the currently active Chat. This prevents a thread/channel deserialized
under chat_a from later resolving to chat_b when the context changes.

Changes:
- ThreadImpl.from_json: eagerly bind from get_chat_singleton() when
  no explicit chat= or adapter= is provided
- ChannelImpl.from_json: same fix
- 2 new tests: eagerly-bound thread survives context exit, and doesn't
  re-resolve to a different chat activated later
- Fix loose cache assertion (<=2 → ==1) in Discord eviction test
- Remove unused real_tests variable in fidelity script

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: patrick-chinchill

scripts/verify_test_fidelity.py

@@ -210,7 +210,6 @@ def main() -> int:
         total_missing += len(missing)
         total_absorbers += absorbers
 
-        real_tests = matched - absorbers
         absorber_note = f" ({absorbers} absorbers)" if absorbers else ""
         status = "OK" if not missing else f"GAPS ({len(missing)})"
         print(f"\n{ts_rel}")

src/chat_sdk/channel.py

@@ -21,6 +21,7 @@
     _is_async_iterable,
     _to_message,
     get_chat_singleton,
+    has_chat_singleton,
 )
 from chat_sdk.types import (
     THREAD_STATE_TTL_MS,
@@ -404,6 +405,12 @@ def from_json(
                     raise RuntimeError(f'Adapter "{channel._adapter_name}" not found in the provided Chat instance')
                 channel._adapter = resolved
             channel._state_adapter_instance = chat.get_state()
+        elif has_chat_singleton() and channel._adapter_name:
+            active = get_chat_singleton()
+            resolved = active.get_adapter(channel._adapter_name)
+            if resolved is not None:
+                channel._adapter = resolved
+            channel._state_adapter_instance = active.get_state()
         return channel
 
     @classmethod

src/chat_sdk/thread.py

@@ -740,6 +740,14 @@ def from_json(
                     raise RuntimeError(f'Adapter "{thread._adapter_name}" not found in the provided Chat instance')
                 thread._adapter = resolved
             thread._state_adapter_instance = chat.get_state()
+        elif has_chat_singleton() and thread._adapter_name:
+            # Eagerly bind from the active/global chat so the thread doesn't
+            # lazily re-resolve later (which could hit a different chat).
+            active = get_chat_singleton()
+            resolved = active.get_adapter(thread._adapter_name)
+            if resolved is not None:
+                thread._adapter = resolved
+            thread._state_adapter_instance = active.get_state()
         return thread
 
     @classmethod

tests/test_chat_resolver.py

@@ -168,6 +168,31 @@ def test_from_json_resolves_via_activate(self):
             assert thread.adapter is not None
             assert thread.adapter.name == "slack"
 
+    def test_from_json_eagerly_binds_so_survives_context_exit(self):
+        """Thread deserialized inside activate() keeps its binding after exit."""
+        chat = _make_chat("slack")
+
+        with chat.activate():
+            thread = ThreadImpl.from_json(_thread_json("slack"))
+            channel = ChannelImpl.from_json(_channel_json("slack"))
+
+        # After context exit, thread/channel should still work
+        # because adapter was eagerly bound during from_json
+        assert thread.adapter.name == "slack"
+        assert channel.adapter.name == "slack"
+
+    def test_from_json_eagerly_binds_prevents_wrong_chat(self):
+        """Thread deserialized under chat_a doesn't resolve to chat_b later."""
+        chat_a = _make_chat("a_adapter")
+        chat_b = _make_chat("b_adapter")
+
+        with chat_a.activate():
+            thread = ThreadImpl.from_json(_thread_json("a_adapter"))
+
+        # Now activate a different chat — thread should NOT re-resolve
+        with chat_b.activate():
+            assert thread.adapter.name == "a_adapter"  # still bound to chat_a
+
 
 class TestExplicitChatParameter:
     """Explicit chat= parameter on from_json beats all fallbacks."""

tests/test_production_fixes.py

@@ -559,7 +559,7 @@ async def test_thread_parent_cache_eviction_on_overflow(self):
 
         # After eviction, all 1001 expired entries should be purged,
         # leaving only the newly inserted one
-        assert len(adapter._thread_parent_cache) <= 2
+        assert len(adapter._thread_parent_cache) == 1
         assert "new-thread-channel" in adapter._thread_parent_cache