diff --git a/hermes_state_common.py b/hermes_state_common.py
index d302a47ae6..817625d112 100644
--- a/hermes_state_common.py
+++ b/hermes_state_common.py
@@ -201,6 +201,17 @@ def _legacy_reset_child_sql(alias: str, reasons_sql: str) -> str:
         f"            AND {alias}.session_key != ''            AND {alias}.session_key = p.session_key)")
 
 
+def _non_continuation_child_sql(child: str = "", parent: str = "?") -> str:
+    """``  AND ...`` clauses rejecting children that are NOT compression continuations of *parent*
+    (branch/delegate/reset forks, tool sessions).  Markers are bound to the parent id: continuations
+    inherit ``model_config`` verbatim, so a marker naming another row is inherited, not a fork.
+    ``child`` is the column prefix (``""``, ``"c."``); single owner so prune and compression agree."""
+    return "".join(
+        f"  AND COALESCE({_sql_json_extract(f'{child}model_config', f'$.{marker}')}, '') != {parent}\n"
+        for marker in ("_branched_from", "_delegate_from", "_reset_from")
+    ) + f"  AND COALESCE({child}source, '') != 'tool'\n"
+
+
 # A reset starts a separate user-visible conversation though rows keep parent_session_id for lineage.
 # Stable marker, or the same-key fallback for pre-marker rows (exact key keeps subagent children out).
 _RESET_CHILD_SQL = (f"{_sql_json_extract('{a}.model_config', '$._reset_from')} IS NOT NULL"
diff --git a/hermes_state_maintenance.py b/hermes_state_maintenance.py
index 26a9b642bc..bf9e1f767b 100644
--- a/hermes_state_maintenance.py
+++ b/hermes_state_maintenance.py
@@ -8,7 +8,7 @@ from pathlib import Path
 from typing import Any, Dict, List, Optional, Tuple
 
 from hermes_state_common import (
-    AUTO_VACUUM_MIN_FREELIST_RATIO, _id_chunks, _placeholders, _sql_json_extract, _sql_session_last_active,
+    AUTO_VACUUM_MIN_FREELIST_RATIO, _id_chunks, _non_continuation_child_sql, _placeholders, _sql_session_last_active,
     escape_like as _escape_like
 )
 from hermes_startup_watchdog import report_startup_progress
@@ -75,14 +75,8 @@ _PRUNE_FILTERS = (
 )
 _PRUNE_FILTER_NAMES = frozenset(name for name, _, _ in _PRUNE_FILTERS) | {"archived", "include_pinned", "lineage_tips_only"}
 
-# Child ``c`` continues compression-ended ``p``; a fork names ``p`` in its marker (compression copies
-# ``model_config``, so a marker naming another row is inherited, not a fork of ``p``).
-_CONTINUATION_EDGE_SQL = " AND ".join([
-    "p.end_reason = 'compression'",
-    *(f"COALESCE({_sql_json_extract('c.model_config', f'$.{marker}')}, '') != p.id"
-      for marker in ("_branched_from", "_delegate_from", "_reset_from")),
-    "COALESCE(c.source, '') != 'tool'",
-])
+# Child ``c`` continues compression-ended ``p`` (same predicate as compression's child lookup).
+_CONTINUATION_EDGE_SQL = "p.end_reason = 'compression'\n" + _non_continuation_child_sql("c.", "p.id")
 
 
 def _continued_ancestors_sql(candidates_where: str) -> str:
diff --git a/hermes_state_sessions.py b/hermes_state_sessions.py
index 74c861e660..ce2591cf41 100644
--- a/hermes_state_sessions.py
+++ b/hermes_state_sessions.py
@@ -17,7 +17,8 @@ from agent.session_activity import (
 from hermes_startup_watchdog import report_startup_progress
 from hermes_state_common import (
     _LISTABLE_CHILD_SQL, _PREVIEW_ELIGIBLE_SQL, _PREVIEW_RAW_SELECT, _RECOVERABLE_END_REASONS,
-    _RECOVERABLE_END_REASONS_SQL, _RESET_CHILD_SQL, _RESET_END_REASONS, _legacy_reset_child_sql, _shape_preview,
+    _RECOVERABLE_END_REASONS_SQL, _RESET_CHILD_SQL, _RESET_END_REASONS, _legacy_reset_child_sql, _non_continuation_child_sql,
+    _shape_preview,
     _sql_in_window, _sql_json_extract, _sql_session_last_active, _sql_session_last_active_by_id,
     escape_like as _escape_like, _SQL_IN_CHUNK, _id_chunks, _placeholders as _session_ids_placeholders,
 )
@@ -451,16 +452,9 @@ class SessionSessionsMixin:
     # quiet and its unkeyed successor (incident was ~60s; 15 min without spanning conversations).
     _ORPHAN_ADOPTION_MAX_GAP_S = 900.0
 
-    # Children that are NOT compression continuations (branches, delegates, reset forks, tool
-    # sessions). Markers are bound to the queried parent id: continuations inherit model_config
-    # verbatim, so presence-matching misclassified them as delegates. Callers bind the parent id
-    # three times for this filter.
-    _NON_CONTINUATION_CHILD_FILTER_SQL = (
-        f"  AND COALESCE({_sql_json_extract('{alias}model_config', '$._branched_from')}, '') != ?\n"
-        f"  AND COALESCE({_sql_json_extract('{alias}model_config', '$._delegate_from')}, '') != ?\n"
-        f"  AND COALESCE({_sql_json_extract('{alias}model_config', '$._reset_from')}, '') != ?\n"
-        "  AND COALESCE({alias}source, '') != 'tool'\n"
-    )
+    # Children that are NOT compression continuations (see _non_continuation_child_sql); presence-
+    # matching misclassified inherited markers as delegates. Callers bind the parent id three times.
+    _NON_CONTINUATION_CHILD_FILTER_SQL = _non_continuation_child_sql("{alias}")
 
     def end_session(self, session_id: str, end_reason: str) -> None:
         """Mark a session ended; the first end_reason wins (a compression split must keep