fix(memory): avoid duplicate summary injection

tests/agent/test_auto_compact.py

@@ -724,6 +724,10 @@ class TestAutoCompactIntegration:
     async def test_full_lifecycle(self, tmp_path):
         loop = _make_loop(tmp_path, session_ttl_minutes=15)
         session = loop.sessions.get_or_create("cli:test")
+        overview = (
+            "IDLE_OVERVIEW_MARKER: User is learning English past tense. "
+            "Example: 'I walked to the store yesterday.'"
+        )
 
         # Phase 1: User has a conversation longer than the retained recent suffix
         session.add_message("user", "I'm learning English, teach me past tense")
@@ -745,7 +749,7 @@ class TestAutoCompactIntegration:
         # Phase 3: User returns with a new message
         loop.provider.chat_with_retry = AsyncMock(
             return_value=LLMResponse(
-                content="User is learning English past tense. Example: 'I walked to the store yesterday.'",
+                content=overview,
                 tool_calls=[],
             )
         )
@@ -759,6 +763,9 @@ class TestAutoCompactIntegration:
 
         # Phase 4: Verify
         session_after = loop.sessions.get_or_create("cli:test")
+        resumed_system_prompt = loop.provider.chat_with_retry.await_args_list[-1].kwargs[
+            "messages"
+        ][0]["content"]
 
         assert any(
             "past tense is used" in str(m.get("content", "")).lower()
@@ -773,6 +780,7 @@ class TestAutoCompactIntegration:
         assert not any(
             "[Resumed Session]" in str(m.get("content", "")) for m in session_after.messages
         )
+        assert resumed_system_prompt.count(overview) == 1
         # Runtime context end marker should NOT be persisted
         assert not any(
             "[/Runtime Context]" in str(m.get("content", "")) for m in session_after.messages

tests/agent/test_context_prompt_cache.py

@@ -112,6 +112,35 @@ def test_recent_history_injection_is_session_scoped(tmp_path) -> None:
     assert "legacy entry without session" not in prompt
 
 
+def test_session_summary_replaces_matching_recent_history_entry(tmp_path) -> None:
+    workspace = _make_workspace(tmp_path)
+    builder = ContextBuilder(workspace)
+    session_key = "telegram:chat-1"
+    overview = "CURRENT_SESSION_OVERVIEW_MARKER"
+
+    builder.memory.append_history("another session event", session_key=session_key)
+    summary_cursor = builder.memory.append_history(overview, session_key=session_key)
+    summary = f"Previous conversation summary (last active 2026-08-19T10:00:00):\n{overview}"
+
+    prompt = builder.build_system_prompt(
+        session_key=session_key,
+        session_summary=summary,
+    )
+
+    assert "# Recent History" in prompt
+    assert "another session event" in prompt
+    assert "[Archived Context Summary]" in prompt
+    assert prompt.count(overview) == 1
+
+    builder.memory.set_last_dream_cursor(summary_cursor)
+    processed_prompt = builder.build_system_prompt(
+        session_key=session_key,
+        session_summary=summary,
+    )
+    assert "# Recent History" not in processed_prompt
+    assert processed_prompt.count(overview) == 1
+
+
 def test_recent_history_injection_unified_excludes_cron_internals(tmp_path) -> None:
     workspace = _make_workspace(tmp_path)
     builder = ContextBuilder(workspace)