fix: keep honcho recall out of cached system prefix (#1201)

Attach later-turn Honcho recall to the current-turn user message at API
call time instead of appending it to the system prompt. This preserves the
stable system-prefix cache while keeping Honcho continuity context
available for the turn.

Also adds regression coverage for the injection helper and for continuing
sessions so Honcho recall stays out of the system prompt.

tests/test_run_agent.py

@@ -14,7 +14,7 @@ from unittest.mock import MagicMock, patch
 import pytest
 
 from honcho_integration.client import HonchoClientConfig
-from run_agent import AIAgent
+from run_agent import AIAgent, _inject_honcho_turn_context
 from agent.prompt_builder import DEFAULT_AGENT_IDENTITY
 
 
@@ -1441,6 +1441,53 @@ class TestSystemPromptStability:
         should_prefetch = bool(conversation_history) and recall_mode != "tools"
         assert should_prefetch is True
 
+    def test_inject_honcho_turn_context_appends_system_note(self):
+        content = _inject_honcho_turn_context("hello", "## Honcho Memory\nprior context")
+        assert "hello" in content
+        assert "Honcho memory was retrieved from prior sessions" in content
+        assert "## Honcho Memory" in content
+
+    def test_honcho_continuing_session_keeps_turn_context_out_of_system_prompt(self, agent):
+        captured = {}
+
+        def _fake_api_call(api_kwargs):
+            captured.update(api_kwargs)
+            return _mock_response(content="done", finish_reason="stop")
+
+        agent._honcho = object()
+        agent._honcho_session_key = "session-1"
+        agent._honcho_config = SimpleNamespace(
+            ai_peer="hermes",
+            memory_mode="hybrid",
+            write_frequency="async",
+            recall_mode="hybrid",
+        )
+        agent._use_prompt_caching = False
+        conversation_history = [
+            {"role": "user", "content": "hello"},
+            {"role": "assistant", "content": "hi there"},
+        ]
+
+        with (
+            patch.object(agent, "_honcho_prefetch", return_value="## Honcho Memory\nprior context"),
+            patch.object(agent, "_queue_honcho_prefetch"),
+            patch.object(agent, "_persist_session"),
+            patch.object(agent, "_save_trajectory"),
+            patch.object(agent, "_cleanup_task_resources"),
+            patch.object(agent, "_interruptible_api_call", side_effect=_fake_api_call),
+        ):
+            result = agent.run_conversation("what were we doing?", conversation_history=conversation_history)
+
+        assert result["completed"] is True
+        api_messages = captured["messages"]
+        assert api_messages[0]["role"] == "system"
+        assert "prior context" not in api_messages[0]["content"]
+        current_user = api_messages[-1]
+        assert current_user["role"] == "user"
+        assert "what were we doing?" in current_user["content"]
+        assert "prior context" in current_user["content"]
+        assert "Honcho memory was retrieved from prior sessions" in current_user["content"]
+
     def test_honcho_prefetch_runs_on_first_turn(self):
         """Honcho prefetch should run when conversation_history is empty."""
         conversation_history = []