diff --git a/run_agent.py b/run_agent.py
index bca815da3c6..1ded29f3679 100644
--- a/run_agent.py
+++ b/run_agent.py
@@ -692,6 +692,24 @@ class AIAgent:
             reset_engine=True,
         )
 
+        # Reset-only session switches (/new, /resume, /branch) update
+        # agent.session_id before calling reset_session_state(). The built-in
+        # compressor keeps durable cooldown state keyed by its bound session,
+        # so rebind it when the active session changed but no full start hook ran.
+        engine = getattr(self, "context_compressor", None)
+        target_session_id = getattr(self, "session_id", "") or ""
+        bound_session_id = getattr(engine, "_session_id", "") if engine is not None else ""
+        if (
+            engine is not None
+            and hasattr(engine, "bind_session_state")
+            and target_session_id
+            and target_session_id != bound_session_id
+        ):
+            try:
+                engine.bind_session_state(getattr(self, "_session_db", None), target_session_id)
+            except Exception as exc:
+                logger.debug("context engine bind_session_state during reset: %s", exc)
+
     def _ensure_lmstudio_runtime_loaded(self, config_context_length: Optional[int] = None) -> None:
         """
         Preload the LM Studio model with at least Hermes' minimum context.
diff --git a/tests/agent/test_context_engine_host_contract.py b/tests/agent/test_context_engine_host_contract.py
index bb6fb4c4108..9bcde04cc90 100644
--- a/tests/agent/test_context_engine_host_contract.py
+++ b/tests/agent/test_context_engine_host_contract.py
@@ -28,7 +28,8 @@ from __future__ import annotations
 
 from unittest.mock import MagicMock
 
-
+from agent.context_compressor import ContextCompressor
+from hermes_state import SessionDB
 from run_agent import AIAgent
 
 
@@ -158,6 +159,43 @@ def test_reset_session_state_default_call_only_resets():
     assert not engine.on_session_start.called
 
 
+def test_reset_session_state_rebinds_builtin_compressor_after_session_switch(tmp_path, monkeypatch):
+    """Reset-only session switches must rebind durable cooldown state to the new session."""
+    db = SessionDB(db_path=tmp_path / "state.db")
+    db.create_session("old-sid", source="cli")
+    db.create_session("new-sid", source="cli")
+    db.record_compression_failure_cooldown("old-sid", 4_000_000_000.0, "old-timeout")
+
+    monkeypatch.setattr(
+        "agent.context_compressor.get_model_context_length",
+        lambda *_a, **_k: 100_000,
+    )
+    compressor = ContextCompressor(
+        model="fake-model",
+        threshold_percent=0.85,
+        protect_first_n=2,
+        protect_last_n=2,
+        quiet_mode=True,
+    )
+    compressor.bind_session_state(db, "old-sid")
+
+    agent = _bare_agent()
+    agent._session_db = db
+    agent.context_compressor = compressor
+    agent.session_id = "new-sid"
+
+    agent.reset_session_state()
+
+    assert compressor._session_id == "new-sid"
+    assert compressor.get_active_compression_failure_cooldown() is None
+    assert db.get_compression_failure_cooldown("old-sid") is not None
+
+    compressor._record_compression_failure_cooldown(30.0, "new-timeout")
+
+    assert db.get_compression_failure_cooldown("new-sid") is not None
+    assert db.get_compression_failure_cooldown("old-sid")["error"] == "old-timeout"
+
+
 def test_update_from_response_forwards_canonical_cache_buckets():
     """conversation_loop passes cache_read/write/reasoning tokens to engine."""
     # Test the contract directly: a usage_dict built from CanonicalUsage must