diff --git a/agent/context_compressor.py b/agent/context_compressor.py
index a16ec913461d8..2884e057ba759 100644
--- a/agent/context_compressor.py
+++ b/agent/context_compressor.py
@@ -2988,7 +2988,13 @@ This compaction should PRIORITISE preserving all information related to the focu
         indicators and aren't what the reporter means by "the output
         of the last message you sent" (#29824).
 
-        Falling back to the most recent assistant message of ANY kind
+        Context-compaction handoff banners can also carry
+        ``role="assistant"``. They are internal continuity state, not a
+        user-visible reply, so ignore them both as text-bearing anchors and
+        as candidates for the fallback below. This mirrors the user-role
+        summary exclusion in ``_find_last_user_message_idx``.
+
+        Falling back to the most recent non-summary assistant message of ANY kind
         only kicks in when no content-bearing assistant message exists
         in the compressible region — typically a fresh session that
         just started a multi-step tool sequence with no prior reply
@@ -2998,7 +3004,9 @@ This compaction should PRIORITISE preserving all information related to the focu
         last_any = -1
         for i in range(len(messages) - 1, head_end - 1, -1):
             msg = messages[i]
-            if msg.get("role") != "assistant":
+            if msg.get("role") != "assistant" or self._is_context_summary_content(
+                msg.get("content")
+            ):
                 continue
             if last_any < 0:
                 last_any = i
diff --git a/tests/agent/test_compressor_assistant_tail_anchor.py b/tests/agent/test_compressor_assistant_tail_anchor.py
index a8be6dc3fef1b..0f870a832828c 100644
--- a/tests/agent/test_compressor_assistant_tail_anchor.py
+++ b/tests/agent/test_compressor_assistant_tail_anchor.py
@@ -74,6 +74,35 @@ def compressor():
 
 
 class TestFindLastAssistantMessageIdx:
+    def test_skips_assistant_role_context_summary_marker(self, compressor):
+        """A persisted assistant-role handoff is internal continuity state,
+        not the last reply the user saw. Tool-call-only assistant messages
+        after it must remain eligible for the fallback anchor."""
+        from agent.context_compressor import SUMMARY_PREFIX
+
+        messages = [
+            {"role": "assistant", "content": f"{SUMMARY_PREFIX}\nold handoff"},
+            {"role": "user", "content": "continue the task"},
+            {"role": "assistant", "content": None,
+             "tool_calls": [{"function": {"name": "t",
+                                          "arguments": "{}"}}]},
+            {"role": "tool", "content": "result", "tool_call_id": "c1"},
+        ]
+        assert compressor._find_last_assistant_message_idx(
+            messages, head_end=0
+        ) == 2
+
+    def test_all_assistant_messages_are_summaries_returns_minus_one(self, compressor):
+        from agent.context_compressor import SUMMARY_PREFIX
+
+        messages = [
+            {"role": "assistant", "content": f"{SUMMARY_PREFIX}\nold handoff"},
+            {"role": "user", "content": "continue the task"},
+        ]
+        assert compressor._find_last_assistant_message_idx(
+            messages, head_end=0
+        ) == -1
+
     def test_finds_content_bearing_assistant(self, compressor):
         messages = [
             {"role": "system", "content": "sys"},