diff --git a/cli/chunk_ingest.py b/cli/chunk_ingest.py
index d81bc6f7..8da86cde 100644
--- a/cli/chunk_ingest.py
+++ b/cli/chunk_ingest.py
@@ -1,13 +1,41 @@
+import json
+
+
+def _tool_call_signature(tool_call):
+    if isinstance(tool_call, dict):
+        name = tool_call["name"]
+        args = tool_call["args"]
+    else:
+        name = tool_call.name
+        args = tool_call.args
+    return (name, json.dumps(args, sort_keys=True, default=str))
+
+
+def _message_fingerprint(message, msg_type, content):
+    tool_calls = tuple(_tool_call_signature(tool_call) for tool_call in getattr(message, "tool_calls", []) or [])
+    return (
+        message.__class__.__name__,
+        msg_type,
+        content.strip() if isinstance(content, str) else str(content),
+        tool_calls,
+    )
+
+
 def ingest_chunk_messages(message_buffer, chunk, classify_message_type) -> None:
     """Ingest all newly seen messages from a graph stream chunk."""
     for message in chunk.get("messages", []):
+        msg_type, content = classify_message_type(message)
         msg_id = getattr(message, "id", None)
         if msg_id is not None:
             if msg_id in message_buffer._processed_message_ids:
                 continue
             message_buffer._processed_message_ids.add(msg_id)
+        else:
+            fingerprint = _message_fingerprint(message, msg_type, content)
+            if fingerprint in message_buffer._processed_message_fingerprints:
+                continue
+            message_buffer._processed_message_fingerprints.add(fingerprint)
 
-        msg_type, content = classify_message_type(message)
         if content and content.strip():
             message_buffer.add_message(msg_type, content)
 
diff --git a/cli/main.py b/cli/main.py
index 2cbb70a1..8810f8df 100644
--- a/cli/main.py
+++ b/cli/main.py
@@ -82,6 +82,7 @@ class MessageBuffer:
         self.report_sections = {}
         self.selected_analysts = []
         self._processed_message_ids = set()
+        self._processed_message_fingerprints = set()
 
     def init_for_analysis(self, selected_analysts):
         """Initialize agent status and report sections based on selected analysts.
@@ -117,6 +118,7 @@ class MessageBuffer:
         self.messages.clear()
         self.tool_calls.clear()
         self._processed_message_ids.clear()
+        self._processed_message_fingerprints.clear()
 
     def get_completed_reports_count(self):
         """Count reports that are finalized (their finalizing agent is completed).
diff --git a/tests/test_cli_chunk_message_ingest.py b/tests/test_cli_chunk_message_ingest.py
index b4efeef9..a9c4ca90 100644
--- a/tests/test_cli_chunk_message_ingest.py
+++ b/tests/test_cli_chunk_message_ingest.py
@@ -17,6 +17,7 @@ class FakeMessage:
 class FakeMessageBuffer:
     def __init__(self):
         self._processed_message_ids = set()
+        self._processed_message_fingerprints = set()
         self.messages = []
         self.tool_calls = []
 
@@ -62,3 +63,29 @@ def test_ingest_chunk_messages_skips_duplicate_message_ids():
 
     assert len(message_buffer.messages) == 1
     assert len(message_buffer.tool_calls) == 1
+
+
+def test_ingest_chunk_messages_skips_duplicate_messages_without_ids():
+    message_buffer = FakeMessageBuffer()
+    chunk = {"messages": [FakeMessage(None, "same", [{"name": "tool_a", "args": {"x": 1}}])]}
+
+    ingest_chunk_messages(message_buffer, chunk, fake_classifier)
+    ingest_chunk_messages(message_buffer, chunk, fake_classifier)
+
+    assert len(message_buffer.messages) == 1
+    assert len(message_buffer.tool_calls) == 1
+
+
+def test_ingest_chunk_messages_keeps_distinct_messages_without_ids():
+    message_buffer = FakeMessageBuffer()
+    chunk = {
+        "messages": [
+            FakeMessage(None, "first", [{"name": "tool_a", "args": {"x": 1}}]),
+            FakeMessage(None, "second", [{"name": "tool_b", "args": {"y": 2}}]),
+        ]
+    }
+
+    ingest_chunk_messages(message_buffer, chunk, fake_classifier)
+
+    assert [content for _, content in message_buffer.messages] == ["first", "second"]
+    assert [name for name, _ in message_buffer.tool_calls] == ["tool_a", "tool_b"]