diff --git a/strix/core/agents.py b/strix/core/agents.py
index c96204df..dd117b45 100644
--- a/strix/core/agents.py
+++ b/strix/core/agents.py
@@ -5,6 +5,7 @@ from __future__ import annotations
 import asyncio
 import json
 import logging
+import re
 import tempfile
 from dataclasses import dataclass, field
 from pathlib import Path
@@ -29,6 +30,22 @@ Status = Literal["running", "waiting", "completed", "stopped", "crashed", "faile
 # on other agents is re-checked on a timer.
 WaitKind = Literal["user", "agents", "stalled"]
 
+_CHATGPT_TRANSCRIPT_TAGS = (
+    "analysis",
+    "assistant",
+    "channel",
+    "final",
+    "user",
+)
+_CHATGPT_TRANSCRIPT_TAG_RE = re.compile(
+    rf"</?(?:{'|'.join(_CHATGPT_TRANSCRIPT_TAGS)})\s*>",
+    flags=re.IGNORECASE,
+)
+
+
+def _strip_chatgpt_transcript_tags(content: str) -> str:
+    return _CHATGPT_TRANSCRIPT_TAG_RE.sub("", content)
+
 
 @dataclass(slots=True)
 class AgentRuntime:
@@ -372,7 +389,7 @@ class AgentCoordinator:
         await self._maybe_snapshot()
 
     async def cancel_descendants(self, agent_id: str) -> None:
-        tasks = []
+        tasks: list[asyncio.Task[Any]] = []
         async with self._lock:
             for aid in reversed(self._subtree_order_locked(agent_id)):
                 task = self.runtimes.get(aid, AgentRuntime()).task
@@ -437,7 +454,7 @@ class AgentCoordinator:
 
     def _message_to_session_item(self, message: dict[str, Any]) -> TResponseInputItem:
         sender = str(message.get("from", "unknown"))
-        content = str(message.get("content", ""))
+        content = _strip_chatgpt_transcript_tags(str(message.get("content", "")))
         if sender == "user":
             return cast("TResponseInputItem", {"role": "user", "content": content})
         sender_name = self.names.get(sender, sender)
diff --git a/tests/test_agent_messages.py b/tests/test_agent_messages.py
new file mode 100644
index 00000000..1594c47e
--- /dev/null
+++ b/tests/test_agent_messages.py
@@ -0,0 +1,35 @@
+"""Tests for agent-to-session message conversion."""
+
+from __future__ import annotations
+
+from strix.core.agents import AgentCoordinator
+
+
+CHATGPT_TRANSCRIPT_CONTENT = (
+    "<analysis>checked target</analysis>\n<channel>final</channel>\n<final>done</final>"
+)
+
+
+def test_message_to_session_item_strips_chatgpt_transcript_tags() -> None:
+    coordinator = AgentCoordinator()
+    coordinator.names["child"] = "Researcher"
+
+    item = coordinator._message_to_session_item(
+        {
+            "from": "child",
+            "type": "information",
+            "priority": "normal",
+            "content": CHATGPT_TRANSCRIPT_CONTENT,
+        }
+    )
+
+    content = str(item["content"])
+
+    assert "<analysis>" not in content
+    assert "</analysis>" not in content
+    assert "<channel>" not in content
+    assert "</channel>" not in content
+    assert "<final>" not in content
+    assert "</final>" not in content
+    assert "checked target" in content
+    assert "done" in content