diff --git a/.gitignore b/.gitignore
index b4ee8a54..0edd66af 100644
--- a/.gitignore
+++ b/.gitignore
@@ -50,3 +50,5 @@ docs/*
 graphify-out/
 .graphify_cached.json
 .graphify_uncached.txt
+
+.venv/
diff --git a/CHANGELOG.md b/CHANGELOG.md
index de7f9241..05e4bca5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,32 @@
 # Hermes Web UI -- Changelog
 
+## [v0.51.37] — 2026-05-10 — Release M (compression / lineage backend)
+
+### Fixed
+
+- **PR #2004** by @franksong2702 — Persisted compression boundary summary for reload UI. Both manual `/session/compress` and auto-compression paths now persist `compression_anchor_summary`, `compression_anchor_visible_idx`, and `compression_anchor_message_key` so the compression card renders correctly after a page reload. Closes #1833.
+
+- **PR #2006** by @qxxaa — Stamp profile on continuation session after context compression. In multi-profile deployments, memory writes after auto-compression silently targeted the **default profile's** `MEMORY.md`, regardless of which profile the browser session was using. Root cause: the compression migration block in `_periodic_checkpoint` did not carry `s.profile` across to the continuation session, so subsequent requests fell back to the default profile's `HERMES_HOME`. Fix resolves the profile name from `s.profile` (or `get_active_profile_name()` while TLS still holds) at streaming-thread start, then stamps `s.profile = _resolved_profile_name` on the continuation session. Verified evidence: session `0dfefb` had read the wrong profile's `MEMORY.md` (16% / 4 entries) instead of the troubleshooting profile's bank (72-77% / 5000+ chars).
+
+- **PR #2011** by @ai-ag2026 — Sidebar lineage collapse: prefer the latest compressed segment when a parent row is touched. Previously the sidebar collapse helper picked representatives by timestamp only, which could surface a touched-parent row instead of the newer compressed tip. Now keys on `_compression_segment_count` so the highest-count segment wins. Regression test added.
+
+- **PR #2014** by @ai-ag2026 — Keep explicit `/api/session/branch` forks out of compression-lineage collapse. Forked sessions now mark `session_source="fork"` on creation, and the sidebar lineage helper guards against folding fork rows into the compression-collapse path even when the parent isn't currently in the rendered window. Backend marker test + sidebar guard test added.
+
+- **PR #2015** by @Jellypowered — Stitch continuation-lineage transcripts in WebUI. Sessions split by continuation events (compression boundary, CLI-close) could show only the latest segment in the WebUI message history. `get_cli_session_messages()` now walks the valid continuation lineage and stitches messages across sessions so the full conversation is visible.
+
+### Added
+
+- **PR #2012** by @dso2ng — New read-only `/api/session/lineage-report/<sid>` endpoint exposing a bounded JSON diagnostic of a session's compression/branching lineage. Pure backend probe — no client UI changes. The sidebar lineage UI (#1906/#1943) already covers user-facing affordances; this fills the bounded backend probe gap for CLI/scripting use.
+
+### Tests
+
+5049 → **5058 collected, 5058 passing, 0 regressions** (+9 net new across `test_session_lineage_collapse.py`, `test_session_lineage_full_transcript.py`, `test_session_lineage_report.py`, `test_465_session_branching.py`, `test_auto_compression_card.py`, `test_sprint46.py`). Full suite 157s on Python 3.11 with `HERMES_HOME` isolation.
+
+### Notes
+
+- `api/routes.py` (4 PRs touched it) and `api/streaming.py` (2 PRs) were the multi-PR files. All hunks at distinct anchors; stage merge clean with no conflicts.
+- Theme coherence: every PR in this batch addresses session compression, lineage, or continuation-stitching — the same conceptual surface from different angles.
+
 ## [v0.51.36] — 2026-05-10 — Release L (locale + provider + cross-cutting)
 
 ### Fixed
diff --git a/api/agent_sessions.py b/api/agent_sessions.py
index 7d65bc57..dce28853 100644
--- a/api/agent_sessions.py
+++ b/api/agent_sessions.py
@@ -439,6 +439,163 @@ def read_importable_agent_session_rows(
 
 
 
+def _lineage_report_row(row: dict, role: str) -> dict:
+    updated_at = row.get('ended_at') if row.get('ended_at') is not None else row.get('started_at')
+    return {
+        'session_id': row.get('id'),
+        'role': role,
+        'title': row.get('title'),
+        'source': row.get('source'),
+        'started_at': row.get('started_at'),
+        'updated_at': updated_at,
+        'end_reason': row.get('end_reason'),
+        'active': row.get('ended_at') is None,
+        'archived': False,
+    }
+
+
+def _empty_lineage_report(session_id: str, *, found: bool = False) -> dict:
+    return {
+        'mutation': False,
+        'found': found,
+        'session_id': session_id,
+        'lineage_key': session_id,
+        'tip_session_id': session_id,
+        'total_segments': 0,
+        'materialized_segments': 0,
+        'segments': [],
+        'children': [],
+        'manual_review': False,
+    }
+
+
+def read_session_lineage_report(db_path: Path, session_id: str | None, max_hops: int = 20) -> dict:
+    """Return a bounded, read-only lifecycle report for a session lineage.
+
+    This helper intentionally reports only facts that can be derived from
+    ``state.db.sessions`` without mutating WebUI JSON, archiving rows, or
+    deleting historical segments. It mirrors the sidebar continuation rules so
+    a future UI/PR can explain which rows are hidden compression/cli-close
+    segments and which child-session branches remain distinct.
+    """
+    sid = str(session_id or '').strip()
+    if not sid:
+        return _empty_lineage_report('')
+    db_path = Path(db_path)
+    if not db_path.exists():
+        return _empty_lineage_report(sid)
+
+    try:
+        with closing(sqlite3.connect(str(db_path))) as conn:
+            conn.row_factory = sqlite3.Row
+            cur = conn.cursor()
+            cur.execute("PRAGMA table_info(sessions)")
+            session_cols = {row[1] for row in cur.fetchall()}
+            required = {'id', 'parent_session_id', 'end_reason'}
+            if not required.issubset(session_cols):
+                return _empty_lineage_report(sid)
+
+            source_expr = _optional_col('source', session_cols)
+            title_expr = _optional_col('title', session_cols)
+            started_expr = _optional_col('started_at', session_cols, '0')
+            ended_expr = _optional_col('ended_at', session_cols)
+            end_reason_expr = _optional_col('end_reason', session_cols)
+            parent_expr = _optional_col('parent_session_id', session_cols)
+
+            def fetch_one(row_id: str | None) -> dict | None:
+                if not row_id:
+                    return None
+                cur.execute(
+                    f"""
+                    SELECT s.id,
+                           {source_expr},
+                           {title_expr},
+                           {started_expr},
+                           {parent_expr},
+                           {ended_expr},
+                           {end_reason_expr}
+                    FROM sessions s
+                    WHERE s.id = ?
+                    """,
+                    (row_id,),
+                )
+                row = cur.fetchone()
+                return dict(row) if row else None
+
+            target = fetch_one(sid)
+            if not target:
+                return _empty_lineage_report(sid)
+
+            segments = [target]
+            current = target
+            seen = {sid}
+            manual_review = False
+            for _hop in range(max(0, int(max_hops))):
+                parent_id = current.get('parent_session_id')
+                parent = fetch_one(parent_id)
+                if not parent or parent_id in seen:
+                    manual_review = bool(parent_id and parent_id in seen)
+                    break
+                if not _is_continuation_session(parent, current):
+                    break
+                segments.append(parent)
+                seen.add(parent_id)
+                current = parent
+            else:
+                manual_review = True
+
+            segment_ids = {row['id'] for row in segments}
+            child_rows: list[dict] = []
+            for parent in segments:
+                cur.execute(
+                    f"""
+                    SELECT s.id,
+                           {source_expr},
+                           {title_expr},
+                           {started_expr},
+                           {parent_expr},
+                           {ended_expr},
+                           {end_reason_expr}
+                    FROM sessions s
+                    WHERE s.parent_session_id = ?
+                    ORDER BY s.started_at DESC
+                    """,
+                    (parent['id'],),
+                )
+                for child_row in cur.fetchall():
+                    child = dict(child_row)
+                    if child['id'] in segment_ids:
+                        continue
+                    if _is_continuation_session(parent, child):
+                        # A continuation outside the selected path means the
+                        # lineage is branched or the caller selected an older
+                        # segment. Report manual review rather than proposing
+                        # destructive cleanup candidates.
+                        manual_review = True
+                        continue
+                    child_rows.append(child)
+    except Exception:
+        return _empty_lineage_report(sid)
+
+    root_id = segments[-1]['id'] if segments else sid
+    tip_id = segments[0]['id'] if segments else sid
+    return {
+        'mutation': False,
+        'found': True,
+        'session_id': sid,
+        'lineage_key': root_id,
+        'tip_session_id': tip_id,
+        'total_segments': len(segments),
+        'materialized_segments': len(segments),
+        'segments': [
+            _lineage_report_row(row, 'tip' if idx == 0 else 'hidden_segment')
+            for idx, row in enumerate(segments)
+        ],
+        'children': [_lineage_report_row(row, 'child_session') for row in child_rows],
+        'manual_review': manual_review,
+    }
+
+
 def read_session_lineage_metadata(db_path: Path, session_ids: list[str] | set[str]) -> dict[str, dict]:
     """Return compression-lineage metadata for known WebUI sidebar sessions.
 
diff --git a/api/models.py b/api/models.py
index 1aac37a5..62099f05 100644
--- a/api/models.py
+++ b/api/models.py
@@ -329,6 +329,7 @@ class Session:
                  context_messages=None,
                  compression_anchor_visible_idx=None,
                  compression_anchor_message_key=None,
+                 compression_anchor_summary=None,
                  context_length=None, threshold_tokens=None,
                  last_prompt_tokens=None,
                  gateway_routing=None, gateway_routing_history=None,
@@ -361,6 +362,7 @@ class Session:
         self.context_messages = context_messages if isinstance(context_messages, list) else []
         self.compression_anchor_visible_idx = compression_anchor_visible_idx
         self.compression_anchor_message_key = compression_anchor_message_key
+        self.compression_anchor_summary = compression_anchor_summary
         self.context_length = context_length
         self.threshold_tokens = threshold_tokens
         self.last_prompt_tokens = last_prompt_tokens
@@ -411,6 +413,7 @@ class Session:
             'personality', 'active_stream_id',
             'pending_user_message', 'pending_attachments', 'pending_started_at',
             'compression_anchor_visible_idx', 'compression_anchor_message_key',
+            'compression_anchor_summary',
             'context_length', 'threshold_tokens', 'last_prompt_tokens',
             'gateway_routing', 'gateway_routing_history', 'llm_title_generated',
             'parent_session_id',
@@ -572,6 +575,7 @@ class Session:
             'personality': self.personality,
             'compression_anchor_visible_idx': self.compression_anchor_visible_idx,
             'compression_anchor_message_key': self.compression_anchor_message_key,
+            'compression_anchor_summary': self.compression_anchor_summary,
             'context_length': self.context_length,
             'threshold_tokens': self.threshold_tokens,
             'last_prompt_tokens': self.last_prompt_tokens,
@@ -1662,7 +1666,9 @@ def get_cli_session_messages(sid) -> list:
 
     Preserve tool-call/result and reasoning metadata from the agent state.db so
     CLI-origin transcripts render with the same tool cards as WebUI-native
-    sessions. Returns empty list on any error.
+    sessions. When the requested session is the tip of a compression/CLI-close
+    continuation chain, return the stitched full transcript across all segments
+    in chronological order. Returns empty list on any error.
     """
     import os
     if str(sid or '').startswith(f'{CLAUDE_CODE_SOURCE}_'):
@@ -1701,12 +1707,56 @@ def get_cli_session_messages(sid) -> list:
                 'codex_message_items',
             ]
             selected = ['role', 'content', 'timestamp'] + [c for c in optional if c in available]
+
+            cur.execute("PRAGMA table_info(sessions)")
+            session_cols = {str(row['name']) for row in cur.fetchall()}
+            session_chain = [str(sid)]
+            if {'parent_session_id', 'end_reason', 'started_at', 'source'}.issubset(session_cols):
+                cur.execute(
+                    """
+                    SELECT id, source, started_at, parent_session_id, ended_at, end_reason
+                    FROM sessions
+                    WHERE id = ?
+                    """,
+                    (sid,),
+                )
+                rows_by_id = {}
+                row = cur.fetchone()
+                if row:
+                    rows_by_id[str(row['id'])] = dict(row)
+                    current_id = str(row['id'])
+                    seen = {current_id}
+                    for _ in range(20):
+                        current = rows_by_id.get(current_id)
+                        parent_id = current.get('parent_session_id') if current else None
+                        if not parent_id or parent_id in seen:
+                            break
+                        cur.execute(
+                            """
+                            SELECT id, source, started_at, parent_session_id, ended_at, end_reason
+                            FROM sessions
+                            WHERE id = ?
+                            """,
+                            (parent_id,),
+                        )
+                        parent_row = cur.fetchone()
+                        if not parent_row:
+                            break
+                        parent_dict = dict(parent_row)
+                        rows_by_id[str(parent_row['id'])] = parent_dict
+                        if not _is_continuation_session(parent_dict, current):
+                            break
+                        session_chain.insert(0, str(parent_row['id']))
+                        current_id = str(parent_row['id'])
+                        seen.add(current_id)
+
+            placeholders = ', '.join('?' for _ in session_chain)
             cur.execute(f"""
-                SELECT {', '.join(selected)}
+                SELECT {', '.join(selected)}, session_id
                 FROM messages
-                WHERE session_id = ?
-                ORDER BY timestamp ASC
-            """, (sid,))
+                WHERE session_id IN ({placeholders})
+                ORDER BY timestamp ASC, id ASC
+            """, session_chain)
             msgs = []
             for row in cur.fetchall():
                 msg = {
diff --git a/api/routes.py b/api/routes.py
index cdf9e12a..33567d0d 100644
--- a/api/routes.py
+++ b/api/routes.py
@@ -26,6 +26,7 @@ from api.agent_sessions import (
     MESSAGING_SOURCES,
     is_cli_session_row,
     is_cli_session_row_visible,
+    read_session_lineage_report,
 )
 
 logger = logging.getLogger(__name__)
@@ -3028,8 +3029,31 @@ def handle_get(handler, parsed) -> bool:
                     # longer visible conversation than the single state.db
                     # segment for this messaging session id. Prefer the longer
                     # sidecar so repaired WebUI history is not hidden behind the
-                    # canonical per-segment transcript.
-                    _all_msgs = sidecar_messages if len(sidecar_messages) > len(cli_messages) else cli_messages
+                    # canonical per-segment transcript. When both sources carry
+                    # different slices of the same stitched conversation, merge
+                    # them chronologically and dedupe exact repeats.
+                    if sidecar_messages and sidecar_messages != cli_messages:
+                        merged_messages = []
+                        seen_message_keys = set()
+                        for msg in sorted(list(cli_messages) + list(sidecar_messages), key=lambda m: (
+                            float(m.get("timestamp") or 0),
+                            str(m.get("role") or ""),
+                            str(m.get("content") or ""),
+                        )):
+                            key = (
+                                str(msg.get("role") or ""),
+                                str(msg.get("content") or ""),
+                                str(msg.get("timestamp") or ""),
+                                str(msg.get("tool_call_id") or ""),
+                                str(msg.get("tool_name") or msg.get("name") or ""),
+                            )
+                            if key in seen_message_keys:
+                                continue
+                            seen_message_keys.add(key)
+                            merged_messages.append(msg)
+                        _all_msgs = merged_messages
+                    else:
+                        _all_msgs = sidecar_messages if len(sidecar_messages) > len(cli_messages) else cli_messages
                 else:
                     _all_msgs = s.messages
             else:
@@ -3184,6 +3208,15 @@ def handle_get(handler, parsed) -> bool:
                 return j(handler, {"session": redact_session_data(sess)})
             return bad(handler, "Session not found", 404)
 
+    if parsed.path == "/api/session/lineage/report":
+        sid = parse_qs(parsed.query).get("session_id", [""])[0]
+        if not sid:
+            return bad(handler, "session_id required", 400)
+        report = read_session_lineage_report(_active_state_db_path(), sid)
+        if not report.get("found"):
+            return bad(handler, "Session not found", 404)
+        return j(handler, report)
+
     if parsed.path == "/api/session/status":
         sid = parse_qs(parsed.query).get("session_id", [""])[0]
         if not sid:
@@ -4232,6 +4265,7 @@ def handle_post(handler, parsed) -> bool:
             title=branch_title,
             messages=forked_messages,
             parent_session_id=source.session_id,
+            session_source="fork",
         )
         with LOCK:
             SESSIONS[branch.session_id] = branch
@@ -7505,6 +7539,38 @@ def _handle_session_compress(handler, body):
             return None
         return {"role": role, "ts": ts, "text": norm, "attachments": attach_count}
 
+    def _compression_summary_from_messages(messages):
+        text = None
+        for m in reversed(messages or []):
+            if not isinstance(m, dict):
+                continue
+            role = str(m.get("role") or "").lower()
+            if role != "assistant":
+                continue
+            if not isinstance(m.get("content"), str):
+                continue
+            content = str(m.get("content") or "").strip()
+            if not content:
+                continue
+            norm = re.sub(r"\s+", " ", content).strip()
+            if (
+                "context compaction" in norm.lower()
+                or "context compression" in norm.lower()
+            ):
+                return norm
+        return None
+
+    def _compact_summary_text(raw_text):
+        if not isinstance(raw_text, str):
+            return None
+        txt = raw_text.strip()
+        if not txt:
+            return None
+        txt = re.sub(r"\s+", " ", txt)
+        if len(txt) > 320:
+            txt = f"{txt[:314]}…"
+        return txt
+
     try:
         require(body, "session_id")
     except ValueError as e:
@@ -7691,6 +7757,12 @@ def _handle_session_compress(handler, body):
             visible_after = _visible_messages_for_anchor(compressed)
             s.compression_anchor_visible_idx = max(0, len(visible_after) - 1) if visible_after else None
             s.compression_anchor_message_key = _anchor_message_key(visible_after[-1]) if visible_after else None
+            summary_text = None
+            if isinstance(summary, dict):
+                summary_text = summary.get("reference_message") or summary.get("token_line") or summary.get("headline")
+            s.compression_anchor_summary = _compact_summary_text(
+                summary_text or _compression_summary_from_messages(compressed) or ""
+            )
             s.save()
 
         session_payload = redact_session_data(
diff --git a/api/streaming.py b/api/streaming.py
index 1582b662..b42a4501 100644
--- a/api/streaming.py
+++ b/api/streaming.py
@@ -1550,6 +1550,87 @@ def _is_context_compression_marker(msg):
     )
 
 
+def _compact_summary_text(raw_text: str | None, limit: int = 320) -> str | None:
+    """Normalize a text blob used in compression summary cards."""
+    if not isinstance(raw_text, str):
+        return None
+    txt = raw_text.strip()
+    if not txt:
+        return None
+    txt = re.sub(r"\s+", " ", txt).strip()
+    if len(txt) > limit:
+        txt = f"{txt[: limit - 6]}…"
+    return txt
+
+
+def _compression_anchor_message_key(message):
+    if not isinstance(message, dict):
+        return None
+    role = str(message.get('role') or '')
+    if not role or role == 'tool':
+        return None
+    content = message.get('content', '')
+    text = _message_text(content)
+    if len(text) > 160:
+        text = text[:160]
+    ts = message.get('_ts') or message.get('timestamp')
+    attachments = message.get('attachments')
+    attach_count = len(attachments) if isinstance(attachments, list) else 0
+    if not text and not attach_count and not ts:
+        return None
+    return {'role': role, 'ts': ts, 'text': text, 'attachments': attach_count}
+
+
+def _visible_messages_for_compression_anchor(messages):
+    out = []
+    for m in messages or []:
+        if not isinstance(m, dict):
+            continue
+        role = m.get('role')
+        if not role or role == 'tool':
+            continue
+        content = m.get('content', '')
+        has_attachments = bool(m.get('attachments'))
+        has_tool_calls = bool(isinstance(m.get('tool_calls'), list) and m.get('tool_calls'))
+        has_tool_use = False
+        has_reasoning = bool(m.get('reasoning'))
+        if isinstance(content, list):
+            text = '\n'.join(
+                str(p.get('text') or p.get('content') or '')
+                for p in content
+                if isinstance(p, dict)
+                and p.get('type') in {'text', 'input_text', 'output_text'}
+            ).strip()
+            for part in content:
+                if not isinstance(part, dict):
+                    continue
+                if part.get('type') == 'tool_use':
+                    has_tool_use = True
+            if not text:
+                has_reasoning = has_reasoning or any(
+                    isinstance(part, dict)
+                    and part.get('type') in {'thinking', 'reasoning'}
+                    for part in content
+                )
+        else:
+            text = str(content or '').strip()
+        if text or has_attachments or has_tool_calls or has_tool_use or has_reasoning:
+            out.append(m)
+    return out
+
+
+def _compression_summary_from_messages(messages):
+    for m in reversed(messages or []):
+        if not isinstance(m, dict):
+            continue
+        if not _is_context_compression_marker(m):
+            continue
+        text = _message_text(m.get('content'))
+        if text:
+            return text
+    return None
+
+
 def _find_current_user_turn(messages, msg_text):
     needle = " ".join(str(msg_text or '').split())
     fallback = None
@@ -2036,7 +2117,24 @@ def _run_agent_streaming(
         except ImportError:
             _profile_home = os.environ.get('HERMES_HOME', '')
             _profile_runtime_env = {}
-
+        
+        # Capture the resolved profile name now, while profile context is
+        # reliable. Used in the compression migration block to stamp s.profile
+        # on the continuation session. We resolve it here rather than calling
+        # get_active_profile_name() at compression time because that function
+        # reads thread-local storage (_tls.profile) set by set_request_profile()
+        # on the HTTP handler thread. The streaming thread is a separate
+        # threading.Thread and does not inherit TLS. At compression time,
+        # get_active_profile_name() would fall back to the process-global
+        # _active_profile, which may belong to a different concurrent tab.
+        _resolved_profile_name = getattr(s, 'profile', None)
+        if not _resolved_profile_name:
+            try:
+                from api.profiles import get_active_profile_name
+                _resolved_profile_name = get_active_profile_name()
+            except Exception:
+                _resolved_profile_name = None
+        
         _thread_env = _build_agent_thread_env(
             _profile_runtime_env,
             str(s.workspace),
@@ -3004,6 +3102,22 @@ def _run_agent_streaming(
                     old_path = SESSION_DIR / f'{old_sid}.json'
                     new_path = SESSION_DIR / f'{new_sid}.json'
                     s.session_id = new_sid
+                    # Carry profile identity across the compression boundary.
+                    # Without this, s.profile stays None on the continuation
+                    # session. On the next request, _run_agent_streaming calls
+                    # get_hermes_home_for_profile(getattr(s, 'profile', None))
+                    # which falls back to the default profile's HERMES_HOME.
+                    # Memory writes then land in the wrong profile's MEMORY.md.
+                    # Stamping here also ensures s.save() persists a non-null
+                    # profile field to the continuation session's JSON file,
+                    # covering the case where the session is later evicted from
+                    # SESSIONS and reconstructed from disk via Session.load().
+                    if not s.profile and _resolved_profile_name:
+                        s.profile = _resolved_profile_name
+                        logger.info(
+                            "Stamped profile=%r on continuation session %s after compression",
+                            _resolved_profile_name, new_sid,
+                        )
                     with LOCK:
                         if old_sid in SESSIONS:
                             SESSIONS[new_sid] = SESSIONS.pop(old_sid)
@@ -3033,6 +3147,17 @@ def _run_agent_streaming(
                         _compressed = True
                 # Notify the frontend that compression happened
                 if _compressed:
+                    visible_after = _visible_messages_for_compression_anchor(s.messages)
+                    s.compression_anchor_visible_idx = (
+                        max(0, len(visible_after) - 1) if visible_after else None
+                    )
+                    s.compression_anchor_message_key = (
+                        _compression_anchor_message_key(visible_after[-1]) if visible_after else None
+                    )
+                    s.compression_anchor_summary = _compact_summary_text(
+                        _compression_summary_from_messages(s.messages)
+                        or _compression_summary_from_messages(s.context_messages)
+                    )
                     put('compressed', {
                         'message': 'Context auto-compressed to continue the conversation',
                     })
diff --git a/static/sessions.js b/static/sessions.js
index 6e7a8f8c..d8ba6a2e 100644
--- a/static/sessions.js
+++ b/static/sessions.js
@@ -1978,6 +1978,7 @@ function _isChildSession(s){
 function _sessionLineageKey(s, sessionIdsInList){
   if(!s||!s.session_id) return null;
   if(_isChildSession(s)) return null;
+  if(s.session_source==='fork') return null;
   const lineageKey=s._lineage_root_id||s.lineage_root_id||null;
   if(lineageKey) return lineageKey;
   // If parent_session_id points to another session in the current list,
@@ -2102,7 +2103,14 @@ function _collapseSessionLineageForSidebar(sessions){
   }
   for(const [key,items] of groups.entries()){
     if(items.length<=1){result.push(items[0]);continue;}
-    const sorted=[...items].sort((a,b)=>_sessionTimestampMs(b)-_sessionTimestampMs(a));
+    const sorted=[...items].sort((a,b)=>{
+      const bSeg=Number(b&&b._compression_segment_count||0);
+      const aSeg=Number(a&&a._compression_segment_count||0);
+      if(bSeg||aSeg){
+        if(bSeg!==aSeg) return bSeg-aSeg;
+      }
+      return _sessionTimestampMs(b)-_sessionTimestampMs(a);
+    });
     const chosen=sorted[0];
     result.push({...chosen,_lineage_key:key,_lineage_collapsed_count:items.length,_lineage_segments:sorted});
   }
diff --git a/static/ui.js b/static/ui.js
index abbf2fc7..7549fc56 100644
--- a/static/ui.js
+++ b/static/ui.js
@@ -4759,6 +4759,9 @@ function renderMessages(options){
   const sessionCompressionAnchorKey=(
     S.session && S.session.compression_anchor_message_key && typeof S.session.compression_anchor_message_key==='object'
   ) ? S.session.compression_anchor_message_key : null;
+  const sessionCompressionSummary=(
+    S.session && typeof S.session.compression_anchor_summary==='string'
+  ) ? S.session.compression_anchor_summary.trim() : '';
   const preservedCompressionTaskMessages=_latestPreservedCompressionTaskListMessages(S.messages);
   const vis=S.messages.filter(m=>{
     if(!m||!m.role||m.role==='tool')return false;
@@ -4775,8 +4778,10 @@ function renderMessages(options){
   inner.innerHTML='';
   const compressionNode=compressionState?_compressionCardsNode(compressionState):null;
   const referenceMessage=S.messages.find(m=>_isContextCompactionMessage(m));
-  const referenceText=referenceMessage?msgContent(referenceMessage)||String(referenceMessage.content||''):'';
-  const referenceNode=(!compressionState && referenceMessage && (sessionCompressionAnchor!==null || sessionCompressionAnchorKey))
+  const referenceText=referenceMessage
+    ? msgContent(referenceMessage)||String(referenceMessage.content||'')
+    : sessionCompressionSummary;
+  const referenceNode=(!compressionState && !!referenceText && (sessionCompressionAnchor!==null || sessionCompressionAnchorKey || sessionCompressionSummary))
     ? (()=>{const row=document.createElement('div');row.innerHTML=`<div class="compression-turn"><div class="compression-turn-blocks">${_compressionReferenceCardHtml(referenceText,false)}${_preservedCompressionTaskListCardsHtml(preservedCompressionTaskMessages)}</div></div>`;return row.firstElementChild;})()
     : null;
   let preservedCompressionTaskCardsAttached=!!referenceNode;
diff --git a/tests/test_465_session_branching.py b/tests/test_465_session_branching.py
index 7a09ac61..2a3722f8 100644
--- a/tests/test_465_session_branching.py
+++ b/tests/test_465_session_branching.py
@@ -68,6 +68,32 @@ def test_branch_creates_session_with_parent():
         "Branch handler should set parent_session_id to source session"
 
 
+def test_branch_marks_explicit_forks_as_fork_sessions():
+    """Explicit branches must not be mistaken for compression lineage rows."""
+    with open('api/routes.py') as f:
+        src = f.read()
+    branch_match = re.search(
+        r'parsed\.path == "/api/session/branch"(.*?)(?=\n    if parsed\.path|$)',
+        src, re.DOTALL
+    )
+    assert branch_match
+    block = branch_match.group(1)
+    assert 'session_source="fork"' in block, \
+        "Branch handler should mark explicit forks with session_source='fork'"
+
+
+def test_branch_fork_sessions_do_not_collapse_into_parent_lineage():
+    """Forks remain selectable rows even if their parent is not in the current list."""
+    with open('static/sessions.js') as f:
+        src = f.read()
+    fn = re.search(r'function _sessionLineageKey\(.*?\n\}', src, re.DOTALL)
+    assert fn, "Could not find _sessionLineageKey"
+    block = fn.group(0)
+    assert "if(s.session_source==='fork') return null;" in block, \
+        "Explicit fork sessions should not collapse via parent_session_id"
+    assert block.index("if(s.session_source==='fork') return null;") < block.index('return s.parent_session_id || null')
+
+
 def test_branch_keep_count_support():
     """Verify the branch endpoint supports keep_count parameter."""
     with open('api/routes.py') as f:
diff --git a/tests/test_auto_compression_card.py b/tests/test_auto_compression_card.py
index aaac6b7e..e598426b 100644
--- a/tests/test_auto_compression_card.py
+++ b/tests/test_auto_compression_card.py
@@ -192,6 +192,16 @@ def test_preserved_task_list_renders_through_compression_card_path():
     assert "_contextCompactionMessageHtml(m, tsTitle, preservedForThisCard)" in src
 
 
+def test_context_anchor_reference_uses_session_summary_fallback():
+    src = _read("static/ui.js")
+
+    assert "sessionCompressionSummary" in src
+    assert "const sessionCompressionSummary" in src
+    assert "referenceText=referenceMessage" in src
+    assert ": sessionCompressionSummary" in src
+    assert "!!referenceText && (sessionCompressionAnchor!==null || sessionCompressionAnchorKey || sessionCompressionSummary)" in src
+
+
 def test_preserved_task_list_attaches_once_per_render():
     src = _read("static/ui.js")
 
diff --git a/tests/test_session_lineage_collapse.py b/tests/test_session_lineage_collapse.py
index f9746b8f..0d14938a 100644
--- a/tests/test_session_lineage_collapse.py
+++ b/tests/test_session_lineage_collapse.py
@@ -170,6 +170,47 @@ console.log(JSON.stringify(collapsed));
     assert [seg["session_id"] for seg in collapsed[0]["_lineage_segments"]] == ["seg10", "seg9", "seg8", "seg7"]
 
 
+def test_sidebar_lineage_collapse_prefers_highest_compression_segment_over_touched_parent():
+    """A touched parent segment must not hide the newer compressed tip.
+
+    Opening or polling an older segment can refresh its updated_at without adding
+    messages. The collapsed sidebar row must still pick the highest compression
+    segment, otherwise the visible chat jumps back to a parent that lacks the
+    completed assistant answer.
+    """
+    js = SESSIONS_JS_PATH.read_text(encoding="utf-8")
+    source = f"""
+const src = {js!r};
+function extractFunc(name) {{
+  const re = new RegExp('function\\\\s+' + name + '\\\\s*\\\\(');
+  const start = src.search(re);
+  if (start < 0) throw new Error(name + ' not found');
+  let i = src.indexOf('{{', start);
+  let depth = 1; i++;
+  while (depth > 0 && i < src.length) {{
+    if (src[i] === '{{') depth++;
+    else if (src[i] === '}}') depth--;
+    i++;
+  }}
+  return src.slice(start, i);
+}}
+eval(extractFunc('_sessionTimestampMs'));
+eval(extractFunc('_isChildSession'));
+eval(extractFunc('_sessionLineageKey'));
+eval(extractFunc('_collapseSessionLineageForSidebar'));
+const sessions = [
+  {{session_id:'seg13', title:'Schaue dir die Release (fork)', message_count:2490, updated_at:200, last_message_at:200, _lineage_root_id:'root', _compression_segment_count:13}},
+  {{session_id:'seg14', title:'Schaue dir die Release (fork)', message_count:2532, updated_at:150, last_message_at:150, _lineage_root_id:'root', _compression_segment_count:14}},
+];
+const collapsed = _collapseSessionLineageForSidebar(sessions);
+console.log(JSON.stringify(collapsed));
+"""
+    collapsed = json.loads(_run_node(source))
+    assert [row["session_id"] for row in collapsed] == ["seg14"]
+    assert collapsed[0]["_lineage_collapsed_count"] == 2
+    assert [seg["session_id"] for seg in collapsed[0]["_lineage_segments"]] == ["seg14", "seg13"]
+
+
 
 def test_sidebar_attaches_child_sessions_to_collapsed_hidden_parent_lineage():
     js = SESSIONS_JS_PATH.read_text(encoding="utf-8")
diff --git a/tests/test_session_lineage_full_transcript.py b/tests/test_session_lineage_full_transcript.py
new file mode 100644
index 00000000..7efc6d18
--- /dev/null
+++ b/tests/test_session_lineage_full_transcript.py
@@ -0,0 +1,61 @@
+"""Regression coverage for stitched full-transcript loading across session segments."""
+
+from __future__ import annotations
+
+import api.routes as routes
+
+
+
+def test_session_endpoint_merges_sidecar_and_lineage_messages_for_cli_sessions(monkeypatch):
+    class DummySession:
+        def __init__(self):
+            self.messages = [{"role": "assistant", "content": "sidecar tail", "timestamp": 10.0}]
+            self.tool_calls = []
+            self.active_stream_id = None
+            self.pending_user_message = None
+            self.pending_attachments = []
+            self.pending_started_at = None
+            self.context_length = 0
+            self.threshold_tokens = 0
+            self.last_prompt_tokens = 0
+            self.model = "openai/gpt-5"
+            self.session_id = "tip"
+
+        def compact(self):
+            return {"session_id": "tip", "title": "Tip", "model": "openai/gpt-5"}
+
+    captured = {}
+
+    monkeypatch.setattr(routes, "get_session", lambda sid, metadata_only=False: DummySession())
+    monkeypatch.setattr(routes, "_clear_stale_stream_state", lambda s: None)
+    monkeypatch.setattr(routes, "_lookup_cli_session_metadata", lambda sid: {"session_source": "messaging"})
+    monkeypatch.setattr(routes, "_is_messaging_session_record", lambda s: True)
+    monkeypatch.setattr(
+        routes,
+        "get_cli_session_messages",
+        lambda sid: [
+            {"role": "user", "content": "root user", "timestamp": 1.0},
+            {"role": "assistant", "content": "tip assistant", "timestamp": 2.0},
+        ],
+    )
+    monkeypatch.setattr(routes, "_resolve_effective_session_model_for_display", lambda s: getattr(s, "model", None))
+    monkeypatch.setattr(routes, "_resolve_effective_session_model_provider_for_display", lambda s: None)
+    monkeypatch.setattr(routes, "_merge_cli_sidebar_metadata", lambda raw, meta: raw)
+    monkeypatch.setattr(routes, "redact_session_data", lambda raw: raw)
+    monkeypatch.setattr(routes, "j", lambda handler, payload, status=200: captured.setdefault("payload", payload))
+
+    class Handler:
+        pass
+
+    class Parsed:
+        path = "/api/session"
+        query = "session_id=tip"
+
+    routes.handle_get(Handler(), Parsed())
+
+    session = captured["payload"]["session"]
+    assert [m["content"] for m in session["messages"]] == [
+        "root user",
+        "tip assistant",
+        "sidecar tail",
+    ]
diff --git a/tests/test_session_lineage_report.py b/tests/test_session_lineage_report.py
new file mode 100644
index 00000000..a95b0bb5
--- /dev/null
+++ b/tests/test_session_lineage_report.py
@@ -0,0 +1,196 @@
+"""Read-only session lineage report endpoint tests."""
+
+import json
+import sqlite3
+import time
+from types import SimpleNamespace
+from urllib.parse import urlparse
+from unittest.mock import patch
+
+import api.agent_sessions as agent_sessions
+import api.routes as routes
+
+
+def _ensure_state_db(path):
+    conn = sqlite3.connect(str(path))
+    conn.executescript(
+        """
+        CREATE TABLE sessions (
+            id TEXT PRIMARY KEY,
+            source TEXT,
+            title TEXT,
+            model TEXT,
+            started_at REAL NOT NULL,
+            message_count INTEGER DEFAULT 0,
+            parent_session_id TEXT,
+            ended_at REAL,
+            end_reason TEXT
+        );
+        """
+    )
+    return conn
+
+
+def _insert_state_row(conn, sid, *, parent=None, ended_at=None, end_reason=None, started_at=None, source="webui"):
+    conn.execute(
+        """
+        INSERT INTO sessions
+        (id, source, title, model, started_at, message_count, parent_session_id, ended_at, end_reason)
+        VALUES (?, ?, ?, 'openai/gpt-5', ?, 2, ?, ?, ?)
+        """,
+        (sid, source, sid.replace("_", " "), started_at or time.time(), parent, ended_at, end_reason),
+    )
+    conn.commit()
+
+
+def test_lineage_report_returns_bounded_read_only_tip_and_hidden_segments(tmp_path):
+    conn = _ensure_state_db(tmp_path / "state.db")
+    t0 = time.time() - 100
+    try:
+        _insert_state_row(conn, "lineage_report_root", started_at=t0, ended_at=t0 + 5, end_reason="compression")
+        _insert_state_row(conn, "lineage_report_mid", parent="lineage_report_root", started_at=t0 + 6, ended_at=t0 + 12, end_reason="cli_close")
+        _insert_state_row(conn, "lineage_report_tip", parent="lineage_report_mid", started_at=t0 + 13)
+
+        report = agent_sessions.read_session_lineage_report(tmp_path / "state.db", "lineage_report_tip")
+
+        assert report["mutation"] is False
+        assert report["session_id"] == "lineage_report_tip"
+        assert report["lineage_key"] == "lineage_report_root"
+        assert report["tip_session_id"] == "lineage_report_tip"
+        assert report["total_segments"] == 3
+        assert report["materialized_segments"] == 3
+        assert [s["session_id"] for s in report["segments"]] == [
+            "lineage_report_tip",
+            "lineage_report_mid",
+            "lineage_report_root",
+        ]
+        assert [s["role"] for s in report["segments"]] == ["tip", "hidden_segment", "hidden_segment"]
+        assert report["children"] == []
+        assert report["manual_review"] is False
+        assert "archive_candidates" not in report
+        assert "delete_candidates" not in report
+    finally:
+        conn.close()
+
+
+def test_lineage_report_keeps_cross_surface_parent_out_of_hidden_segments(tmp_path):
+    conn = _ensure_state_db(tmp_path / "state.db")
+    t0 = time.time() - 100
+    try:
+        _insert_state_row(
+            conn,
+            "lineage_report_telegram_parent",
+            source="telegram",
+            started_at=t0,
+            ended_at=t0 + 5,
+            end_reason="compression",
+        )
+        _insert_state_row(
+            conn,
+            "lineage_report_webui_tip",
+            source="webui",
+            parent="lineage_report_telegram_parent",
+            started_at=t0 + 6,
+        )
+
+        report = agent_sessions.read_session_lineage_report(tmp_path / "state.db", "lineage_report_webui_tip")
+
+        assert report["lineage_key"] == "lineage_report_webui_tip"
+        assert report["total_segments"] == 1
+        assert [s["session_id"] for s in report["segments"]] == ["lineage_report_webui_tip"]
+        assert report["segments"][0]["role"] == "tip"
+        assert report["children"] == []
+    finally:
+        conn.close()
+
+
+def test_lineage_report_surfaces_non_continuation_children_without_mutation(tmp_path):
+    conn = _ensure_state_db(tmp_path / "state.db")
+    t0 = time.time() - 100
+    try:
+        _insert_state_row(conn, "lineage_report_root", started_at=t0, ended_at=t0 + 5, end_reason="compression")
+        _insert_state_row(conn, "lineage_report_tip", parent="lineage_report_root", started_at=t0 + 6, ended_at=t0 + 15, end_reason="user_stop")
+        _insert_state_row(conn, "lineage_report_child", parent="lineage_report_tip", started_at=t0 + 8)
+
+        report = agent_sessions.read_session_lineage_report(tmp_path / "state.db", "lineage_report_tip")
+
+        assert report["lineage_key"] == "lineage_report_root"
+        assert [s["session_id"] for s in report["segments"]] == ["lineage_report_tip", "lineage_report_root"]
+        assert report["children"] == [
+            {
+                "session_id": "lineage_report_child",
+                "role": "child_session",
+                "title": "lineage report child",
+                "source": "webui",
+                "started_at": t0 + 8,
+                "updated_at": t0 + 8,
+                "end_reason": None,
+                "active": True,
+                "archived": False,
+            }
+        ]
+        assert report["mutation"] is False
+    finally:
+        conn.close()
+
+
+def test_lineage_report_marks_bounded_parent_walk_for_manual_review(tmp_path):
+    conn = _ensure_state_db(tmp_path / "state.db")
+    t0 = time.time() - 100
+    try:
+        _insert_state_row(conn, "lineage_report_root", started_at=t0, ended_at=t0 + 5, end_reason="compression")
+        _insert_state_row(conn, "lineage_report_mid", parent="lineage_report_root", started_at=t0 + 6, ended_at=t0 + 12, end_reason="compression")
+        _insert_state_row(conn, "lineage_report_tip", parent="lineage_report_mid", started_at=t0 + 13)
+
+        report = agent_sessions.read_session_lineage_report(tmp_path / "state.db", "lineage_report_tip", max_hops=1)
+
+        assert report["mutation"] is False
+        assert report["manual_review"] is True
+        assert [s["session_id"] for s in report["segments"]] == ["lineage_report_tip", "lineage_report_mid"]
+        assert report["total_segments"] == 2
+    finally:
+        conn.close()
+
+
+def test_lineage_report_endpoint_is_read_only_and_uses_active_state_db(tmp_path):
+    conn = _ensure_state_db(tmp_path / "state.db")
+    t0 = time.time() - 100
+    try:
+        _insert_state_row(conn, "lineage_report_root", started_at=t0, ended_at=t0 + 5, end_reason="compression")
+        _insert_state_row(conn, "lineage_report_tip", parent="lineage_report_root", started_at=t0 + 6)
+        captured = {}
+
+        def fake_j(handler, data, status=200, **_kwargs):
+            captured["status"] = status
+            captured["data"] = data
+            return data
+
+        handler = SimpleNamespace()
+        parsed = urlparse("/api/session/lineage/report?session_id=lineage_report_tip")
+        with patch.object(routes, "_active_state_db_path", return_value=tmp_path / "state.db"), patch.object(routes, "j", side_effect=fake_j):
+            routes.handle_get(handler, parsed)
+
+        assert captured["status"] == 200
+        assert captured["data"]["mutation"] is False
+        assert captured["data"]["lineage_key"] == "lineage_report_root"
+        assert captured["data"]["total_segments"] == 2
+    finally:
+        conn.close()
+
+
+def test_lineage_report_endpoint_returns_404_for_unknown_session(tmp_path):
+    conn = _ensure_state_db(tmp_path / "state.db")
+    conn.close()
+    captured = {}
+
+    def fake_bad(handler, message, status=400):
+        captured["status"] = status
+        captured["message"] = message
+        return {"error": message}
+
+    handler = SimpleNamespace()
+    parsed = urlparse("/api/session/lineage/report?session_id=missing_lineage_report_session")
+    with patch.object(routes, "_active_state_db_path", return_value=tmp_path / "state.db"), patch.object(routes, "bad", side_effect=fake_bad):
+        routes.handle_get(handler, parsed)
+
+    assert captured == {"status": 404, "message": "Session not found"}
diff --git a/tests/test_sprint46.py b/tests/test_sprint46.py
index 0cffd289..35145c95 100644
--- a/tests/test_sprint46.py
+++ b/tests/test_sprint46.py
@@ -10,7 +10,7 @@ import types
 
 from api.models import Session
 from api.config import SESSION_DIR
-from api.routes import _handle_session_compress
+from api.routes import _handle_session_compress, get_session
 from tests._pytest_port import BASE
 
 
@@ -141,6 +141,14 @@ def test_session_compress_roundtrip(monkeypatch, cleanup_test_sessions):
         {"role": "user", "content": "one"},
         {"role": "assistant", "content": "four"},
     ]
+    assert payload["session"]["compression_anchor_summary"] is not None
+    assert payload["session"]["compression_anchor_visible_idx"] == 1
+    assert isinstance(payload["session"]["compression_anchor_message_key"], dict)
+    assert payload["session"]["compression_anchor_message_key"].get("role") == "assistant"
+    loaded = get_session(sid)
+    assert loaded.compression_anchor_summary == payload["session"]["compression_anchor_summary"]
+    assert loaded.compression_anchor_visible_idx == payload["session"]["compression_anchor_visible_idx"]
+    assert loaded.compression_anchor_message_key == payload["session"]["compression_anchor_message_key"]
     assert _FakeAgent.last_instance is not None
     assert _FakeAgent.last_instance.context_compressor.calls[0]["focus_topic"] == "database schema"