diff --git a/agent/transcript_repair.py b/agent/transcript_repair.py
index f245088abc..f9b1500823 100644
--- a/agent/transcript_repair.py
+++ b/agent/transcript_repair.py
@@ -29,8 +29,9 @@ def resolve_and_repair_transcript_batch(
     decode_content_fn: Callable[[Any], Any],
 ) -> List[Dict[str, Any]]:
     """Partition a message batch within an active write transaction. An assistant message carrying an
-    existing integer ``_row_id`` targets its active SQLite row (or the active clone a watermark compaction
-    made of it): a blank row is updated in place; a non-blank one (concurrent winner) has its canonical
+    existing integer ``_row_id`` targets that SQLite row, or the active clone a watermark compaction made
+    of it. An inactive row without a clone is repaired in place without changing its archive/rewind state;
+    an active blank row is filled, while an active non-blank row (concurrent winner) has its canonical
     content adopted without overwrite. Returns the messages that must be inserted as fresh rows."""
     inserted_rows: List[Dict[str, Any]] = []
     for msg in messages:
@@ -44,7 +45,15 @@ def resolve_and_repair_transcript_batch(
         target_id = int(target_row["id"])
         decoded = decode_content_fn(target_row["content"])
         msg["_row_id"] = target_id
-        if is_content_blank(decoded):
+        if int(target_row["active"] or 0) == 0:
+            # The row identity still belongs to this session, but compaction/rewind removed it from the
+            # model projection. Persist an in-place sanitizer rewrite without resurrecting the row or
+            # appending a second display identity.
+            conn.execute(
+                "UPDATE messages SET content = ? WHERE id = ? AND session_id = ? AND active = 0",
+                (encode_content_fn(msg.get("content")), target_id, session_id),
+            )
+        elif is_content_blank(decoded):
             conn.execute(
                 "UPDATE messages SET content = ? "
                 "WHERE id = ? AND session_id = ? AND active = 1",
@@ -56,7 +65,7 @@ def resolve_and_repair_transcript_batch(
 
 
 def _active_assistant_row(conn: sqlite3.Connection, session_id: str, row_id: int):
-    """The active assistant row for ``row_id``, or the active clone a watermark compaction made of it."""
+    """The active clone for ``row_id``, or the addressed inactive assistant when no clone exists."""
     row = conn.execute(
         "SELECT id, role, active, timestamp, content FROM messages "
         "WHERE id = ? AND session_id = ?",
@@ -66,14 +75,16 @@ def _active_assistant_row(conn: sqlite3.Connection, session_id: str, row_id: int
         return None
     if int(row["active"] or 0) == 1:
         return row
-    # Watermark compaction soft-archived the concurrent tail and cloned it.
-    return conn.execute(
+    # Watermark compaction soft-archived the concurrent tail and cloned it. Prefer that live identity;
+    # otherwise keep the addressed inactive row so a later sanitizer pass cannot append it as new.
+    clone = conn.execute(
         "SELECT id, role, active, timestamp, content FROM messages "
         "WHERE session_id = ? AND active = 1 AND role = 'assistant' "
         "AND timestamp IS ? AND id != ? "
         "ORDER BY id DESC LIMIT 1",
         (session_id, row["timestamp"], row["id"]),
     ).fetchone()
+    return clone if clone is not None else row
 
 
 def sync_flushed_message_markers(batch_msgs: List[Dict[str, Any]], batch_rows: List[Dict[str, Any]]) -> None:
diff --git a/tests/agent/test_tool_call_incremental_persistence.py b/tests/agent/test_tool_call_incremental_persistence.py
index 59898c34e5..cb3d99d6d6 100644
--- a/tests/agent/test_tool_call_incremental_persistence.py
+++ b/tests/agent/test_tool_call_incremental_persistence.py
@@ -748,6 +748,82 @@ def test_flush_stale_row_id_from_other_session_does_not_fill_child_blank(tmp_pat
     ]
 
 
+def test_flush_sanitized_archived_row_does_not_append_duplicate(tmp_path):
+    """A sanitizer rewrite of an archived row must preserve its durable identity.
+
+    SessionDB already scrubs lone surrogates on the initial write. The outbound sanitizer later makes the
+    same repair on the live dict and pops ``_db_persisted``. Re-appending that inactive row creates a second
+    assistant with the same content and microsecond timestamp, and both rows enter the display projection.
+    """
+    from agent.message_sanitization import _sanitize_messages_surrogates
+
+    agent = _make_agent()
+    db_path = tmp_path / "state.db"
+    session_id = "sess-sanitized-archived-row"
+    db = _attach_real_session_db(agent, db_path, session_id)
+    messages = [
+        {"role": "user", "content": "summarize"},
+        {"role": "assistant", "content": "answer \ud800 tail"},
+    ]
+    agent._flush_messages_to_session_db(messages)
+    assistant_id = messages[-1]["_row_id"]
+    assistant_timestamp = messages[-1]["timestamp"]
+
+    db.archive_and_compact(
+        session_id,
+        compacted_messages=[{"role": "user", "content": "prior turns summarized"}],
+    )
+    assert _sanitize_messages_surrogates(messages) is True
+    agent._db_flush_scan_prefix = None
+
+    assert agent._flush_messages_to_session_db(messages) is True
+
+    all_rows = db.get_messages(session_id, include_inactive=True)
+    assistants = [row for row in all_rows if row.get("role") == "assistant"]
+    assert len(assistants) == 1
+    assert assistants[0]["id"] == assistant_id
+    assert assistants[0]["timestamp"] == assistant_timestamp
+    assert assistants[0]["active"] in (0, False)
+    assert assistants[0]["compacted"] in (1, True)
+    assert assistants[0]["content"] == "answer \ufffd tail"
+    display = db.get_messages(session_id, include_compacted=True)
+    assert [row["content"] for row in display].count("answer \ufffd tail") == 1
+    assert messages[-1]["_row_id"] == assistant_id
+    assert messages[-1]["_db_persisted"] is True
+
+
+def test_flush_ascii_repair_updates_archived_row_without_resurrecting_it(tmp_path):
+    """A changed archived payload is updated in place while its active/compacted state is preserved."""
+    from agent.message_sanitization import _sanitize_messages_non_ascii
+
+    agent = _make_agent()
+    db_path = tmp_path / "state.db"
+    session_id = "sess-ascii-repaired-archived-row"
+    db = _attach_real_session_db(agent, db_path, session_id)
+    messages = [
+        {"role": "user", "content": "summarize"},
+        {"role": "assistant", "content": "caf\u00e9 answer"},
+    ]
+    agent._flush_messages_to_session_db(messages)
+    assistant_id = messages[-1]["_row_id"]
+
+    db.archive_and_compact(
+        session_id,
+        compacted_messages=[{"role": "user", "content": "prior turns summarized"}],
+    )
+    assert _sanitize_messages_non_ascii(messages) is True
+    agent._db_flush_scan_prefix = None
+
+    assert agent._flush_messages_to_session_db(messages) is True
+
+    all_rows = db.get_messages(session_id, include_inactive=True)
+    assistant = next(row for row in all_rows if row.get("id") == assistant_id)
+    assert assistant["content"] == "caf answer"
+    assert assistant["active"] in (0, False)
+    assert assistant["compacted"] in (1, True)
+    assert len([row for row in all_rows if row.get("role") == "assistant"]) == 1
+    assert not any(row.get("role") == "assistant" for row in db.get_messages(session_id))
+
 def test_flush_archived_same_session_row_id_fills_active_clone(tmp_path):
     """Watermark compaction clones the tail; stale `_row_id` must not win.