feat: replace Git-DAG timeline with flat snapshot browser

Replace HistoryTree (DAG with branches, Graphviz rendering) with a flat
chronological SnapshotTimeline. New UI features: split-view layout,
snapshot compare/diff, cherry-pick restore of individual sequences or
fields, auto-snapshots with debounce, and pin/filter support.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

db.py

@@ -242,7 +242,6 @@ class ProjectDB:
         )
         self.conn.commit()
 
-    @staticmethod
     @staticmethod
     def _migrate_lora_keys(data: dict) -> dict:
         """Split combined lora 'name:strength' into separate name and strength keys."""
@@ -340,27 +339,34 @@ class ProjectDB:
     # ------------------------------------------------------------------
 
     def save_history_tree(self, data_file_id: int, tree_data: dict) -> None:
-        """Save history tree, extracting node snapshots into separate table."""
+        """Save history tree, extracting snapshot data into separate table.
+
+        Supports both new format (snapshots dict) and old format (nodes dict).
+        """
         now = time.time()
-        nodes = tree_data.get("nodes", {})
+        if "snapshots" in tree_data:
+            entries = tree_data.get("snapshots", {})
+            entry_key = "snapshots"
+        else:
+            entries = tree_data.get("nodes", {})
+            entry_key = "nodes"
         slim_tree = dict(tree_data)
-        slim_nodes = {}
+        slim_entries = {}
-        for nid, node in nodes.items():
+        for eid, entry in entries.items():
-            slim_nodes[nid] = {k: v for k, v in node.items() if k != "data"}
+            slim_entries[eid] = {k: v for k, v in entry.items() if k != "data"}
-        slim_tree["nodes"] = slim_nodes
+        slim_tree[entry_key] = slim_entries
 
         self.conn.execute("BEGIN IMMEDIATE")
         try:
-            # Extract snapshot data from nodes into history_snapshots table
+            for eid, entry in entries.items():
-            for nid, node in nodes.items():
+                snap = entry.get("data")
-                snap = node.get("data")
                 if snap:
                     self.conn.execute(
                         "INSERT INTO history_snapshots (data_file_id, node_id, snapshot_data, updated_at) "
                         "VALUES (?, ?, ?, ?) "
                         "ON CONFLICT(data_file_id, node_id) DO UPDATE SET "
                         "snapshot_data=excluded.snapshot_data, updated_at=excluded.updated_at",
-                        (data_file_id, nid, json.dumps(snap), now),
+                        (data_file_id, eid, json.dumps(snap), now),
                     )
             self.conn.execute(
                 "INSERT INTO history_trees (data_file_id, tree_data, updated_at) "
@@ -463,24 +469,30 @@ class ProjectDB:
                     )
 
             # Import history tree (extract snapshots into separate table)
+            # Supports both new format (snapshots dict) and old format (nodes dict)
             history_tree = data.get(KEY_HISTORY_TREE)
             if history_tree and isinstance(history_tree, dict):
                 now = time.time()
-                nodes = history_tree.get("nodes", {})
+                if "snapshots" in history_tree:
+                    entries = history_tree.get("snapshots", {})
+                    entry_key = "snapshots"
+                else:
+                    entries = history_tree.get("nodes", {})
+                    entry_key = "nodes"
                 slim_tree = dict(history_tree)
-                slim_nodes = {}
+                slim_entries = {}
-                for nid, node in nodes.items():
+                for eid, entry in entries.items():
-                    snap = node.get("data")
+                    snap = entry.get("data")
                     if snap:
                         self.conn.execute(
                             "INSERT INTO history_snapshots (data_file_id, node_id, snapshot_data, updated_at) "
                             "VALUES (?, ?, ?, ?) "
                             "ON CONFLICT(data_file_id, node_id) DO UPDATE SET "
                             "snapshot_data=excluded.snapshot_data, updated_at=excluded.updated_at",
-                            (df_id, nid, json.dumps(snap), now),
+                            (df_id, eid, json.dumps(snap), now),
                         )
-                    slim_nodes[nid] = {k: v for k, v in node.items() if k != "data"}
+                    slim_entries[eid] = {k: v for k, v in entry.items() if k != "data"}
-                slim_tree["nodes"] = slim_nodes
+                slim_tree[entry_key] = slim_entries
                 self.conn.execute(
                     "INSERT INTO history_trees (data_file_id, tree_data, updated_at) "
                     "VALUES (?, ?, ?) "
@@ -540,9 +552,9 @@ class ProjectDB:
         # Load history tree (metadata only, no snapshot data)
         tree = self.get_history_tree(df["id"])
         if tree:
-            # Strip any residual snapshot data from nodes
+            # Strip any residual snapshot data (supports both formats)
-            for node in tree.get("nodes", {}).values():
+            for entry in tree.get("snapshots", tree.get("nodes", {})).values():
-                node.pop("data", None)
+                entry.pop("data", None)
             data["history_tree"] = tree
         t3 = time.time()
 

main.py

@@ -295,12 +295,12 @@ def index():
                         sync_to_db, pane_state.db, pane_state.current_project, fp, data)
                     tree = data.get('history_tree')
                     if tree and isinstance(tree, dict):
-                        for node in tree.get('nodes', {}).values():
+                        for entry in tree.get('snapshots', tree.get('nodes', {})).values():
-                            node.pop('data', None)
+                            entry.pop('data', None)
             for backup in data.get('history_tree_backup', []):
                 if isinstance(backup, dict):
-                    for node in backup.get('nodes', {}).values():
+                    for entry in backup.get('snapshots', backup.get('nodes', {})).values():
-                        node.pop('data', None)
+                        entry.pop('data', None)
             pane_state.data_cache = data
             pane_state.last_mtime = fp.stat().st_mtime if fp.exists() else 0
             pane_state.loaded_file = str(fp)
@@ -339,13 +339,13 @@ def index():
                     sync_to_db, state.db, state.current_project, fp, data)
                 tree = data.get('history_tree')
                 if tree and isinstance(tree, dict):
-                    for node in tree.get('nodes', {}).values():
+                    for entry in tree.get('snapshots', tree.get('nodes', {})).values():
-                        node.pop('data', None)
+                        entry.pop('data', None)
         # Strip snapshot data from history_tree_backup to prevent RAM/disk bloat
         for backup in data.get('history_tree_backup', []):
             if isinstance(backup, dict):
-                for node in backup.get('nodes', {}).values():
+                for entry in backup.get('snapshots', backup.get('nodes', {})).values():
-                    node.pop('data', None)
+                    entry.pop('data', None)
         state.data_cache = data
         state.last_mtime = fp.stat().st_mtime if fp.exists() else 0
         state.loaded_file = str(fp)

snapshot_timeline.py

@@ -0,0 +1,184 @@
+import time
+import uuid
+from typing import Any
+
+KEY_PROMPT_HISTORY = "prompt_history"
+
+
+class SnapshotTimeline:
+    """Flat chronological snapshot list — replaces the old HistoryTree DAG."""
+
+    def __init__(self, raw_data: dict[str, Any]) -> None:
+        # Detect and migrate old HistoryTree format
+        if "nodes" in raw_data and "branches" in raw_data:
+            self._migrate_from_tree(raw_data)
+        elif KEY_PROMPT_HISTORY in raw_data and isinstance(raw_data[KEY_PROMPT_HISTORY], list):
+            self._migrate_legacy(raw_data[KEY_PROMPT_HISTORY])
+        else:
+            self.snapshots: dict[str, dict[str, Any]] = raw_data.get("snapshots", {})
+            self.current_id: str | None = raw_data.get("current_id", None)
+
+    # ------------------------------------------------------------------
+    # Migration
+    # ------------------------------------------------------------------
+
+    def _migrate_from_tree(self, raw_data: dict[str, Any]) -> None:
+        """Flatten old HistoryTree nodes into snapshot list, discarding DAG info."""
+        self.snapshots = {}
+        nodes = raw_data.get("nodes", {})
+        for nid, node in nodes.items():
+            self.snapshots[nid] = {
+                "id": nid,
+                "timestamp": node.get("timestamp", time.time()),
+                "note": node.get("note", "Migrated"),
+                "pinned": False,
+                "auto": False,
+                "seq_count": self._count_seqs(node.get("data")),
+            }
+            # Preserve snapshot data if present
+            if "data" in node and node["data"]:
+                self.snapshots[nid]["data"] = node["data"]
+        self.current_id = raw_data.get("head_id")
+
+    def _migrate_legacy(self, old_list: list[dict[str, Any]]) -> None:
+        """Convert ancient prompt_history list into snapshots."""
+        self.snapshots = {}
+        self.current_id = None
+        for item in reversed(old_list):
+            sid = self._make_id()
+            self.snapshots[sid] = {
+                "id": sid,
+                "timestamp": time.time(),
+                "note": item.get("note", "Legacy Import"),
+                "pinned": False,
+                "auto": False,
+                "seq_count": self._count_seqs(item),
+                "data": item,
+            }
+            self.current_id = sid
+
+    # ------------------------------------------------------------------
+    # Core operations
+    # ------------------------------------------------------------------
+
+    def record(self, data: dict[str, Any], note: str = "Snapshot",
+               auto: bool = False) -> str:
+        """Create a new snapshot and return its ID."""
+        sid = self._make_id()
+        self.snapshots[sid] = {
+            "id": sid,
+            "timestamp": time.time(),
+            "note": note,
+            "pinned": False,
+            "auto": auto,
+            "seq_count": self._count_seqs(data),
+            "data": data,
+        }
+        self.current_id = sid
+        return sid
+
+    def get_snapshot_data(self, snapshot_id: str) -> dict[str, Any] | None:
+        """Return the inline snapshot data if present."""
+        snap = self.snapshots.get(snapshot_id)
+        if snap:
+            return snap.get("data")
+        return None
+
+    def toggle_pin(self, snapshot_id: str) -> bool:
+        """Toggle pinned state, return new value."""
+        snap = self.snapshots.get(snapshot_id)
+        if snap:
+            snap["pinned"] = not snap.get("pinned", False)
+            return snap["pinned"]
+        return False
+
+    def delete(self, snapshot_id: str) -> None:
+        """Remove a snapshot."""
+        self.snapshots.pop(snapshot_id, None)
+        if self.current_id == snapshot_id:
+            # Fall back to most recent remaining
+            if self.snapshots:
+                self.current_id = max(
+                    self.snapshots.values(), key=lambda s: s["timestamp"]
+                )["id"]
+            else:
+                self.current_id = None
+
+    def strip_snapshots(self) -> None:
+        """Remove inline data from all snapshots (for slim JSON storage)."""
+        for snap in self.snapshots.values():
+            snap.pop("data", None)
+
+    # ------------------------------------------------------------------
+    # Serialization
+    # ------------------------------------------------------------------
+
+    def to_dict(self) -> dict[str, Any]:
+        return {
+            "snapshots": self.snapshots,
+            "current_id": self.current_id,
+        }
+
+    # ------------------------------------------------------------------
+    # Helpers
+    # ------------------------------------------------------------------
+
+    def _make_id(self) -> str:
+        for _ in range(10):
+            sid = str(uuid.uuid4())[:8]
+            if sid not in self.snapshots:
+                return sid
+        raise ValueError("Failed to generate unique snapshot ID after 10 attempts")
+
+    @staticmethod
+    def _count_seqs(data: dict | None) -> int:
+        if not data:
+            return 0
+        from utils import KEY_BATCH_DATA
+        batch = data.get(KEY_BATCH_DATA, [])
+        return len(batch) if isinstance(batch, list) else 0
+
+
+# ------------------------------------------------------------------
+# Diff function
+# ------------------------------------------------------------------
+
+def diff_snapshots(old_batch: list[dict], new_batch: list[dict]) -> list[dict]:
+    """Compare two batch lists by sequence_number, return per-sequence diffs.
+
+    Returns a list of dicts:
+        {
+            "seq_num": int,
+            "status": "unchanged" | "changed" | "added" | "removed",
+            "changes": [{"field": str, "old": Any, "new": Any}],
+        }
+    """
+    from utils import KEY_SEQUENCE_NUMBER
+
+    old_by_seq = {int(s.get(KEY_SEQUENCE_NUMBER, 0)): s for s in old_batch}
+    new_by_seq = {int(s.get(KEY_SEQUENCE_NUMBER, 0)): s for s in new_batch}
+
+    all_seqs = sorted(set(old_by_seq) | set(new_by_seq))
+    result = []
+
+    for seq_num in all_seqs:
+        old_item = old_by_seq.get(seq_num)
+        new_item = new_by_seq.get(seq_num)
+
+        if old_item and not new_item:
+            result.append({"seq_num": seq_num, "status": "removed", "changes": []})
+        elif new_item and not old_item:
+            result.append({"seq_num": seq_num, "status": "added", "changes": []})
+        else:
+            # Both exist — field-by-field comparison
+            all_keys = sorted(set(old_item) | set(new_item))
+            changes = []
+            for k in all_keys:
+                old_val = old_item.get(k)
+                new_val = new_item.get(k)
+                if old_val != new_val:
+                    changes.append({"field": k, "old": old_val, "new": new_val})
+            status = "changed" if changes else "unchanged"
+            result.append({"seq_num": seq_num, "status": status, "changes": changes})
+
+    return result

state.py

@@ -13,7 +13,7 @@ class AppState:
     snippets: dict = field(default_factory=dict)
     file_path: Path | None = None
     restored_indicator: str | None = None
-    timeline_selected_nodes: set = field(default_factory=set)
+    timeline_selected_id: str | None = None
     live_toggles: dict = field(default_factory=dict)
     show_comfy_monitor: bool = True
 

tab_batch_ng.py

@@ -16,9 +16,11 @@ from utils import (
     DEFAULTS, save_json, load_json, sync_to_db,
     KEY_BATCH_DATA, KEY_HISTORY_TREE, KEY_PROMPT_HISTORY, KEY_SEQUENCE_NUMBER,
 )
-from history_tree import HistoryTree
+from snapshot_timeline import SnapshotTimeline
 
 IMAGE_EXTENSIONS = {'.png', '.jpg', '.jpeg', '.webp', '.bmp', '.gif'}
+_AUTO_SNAP_DEBOUNCE = 30  # seconds between auto-snapshots
+_last_auto_snap: dict[str, float] = {}  # file_path -> timestamp
 SUB_SEGMENT_MULTIPLIER = 1000
 SUB_SEGMENT_NUM_COLORS = 6
 FRAME_TO_SKIP_DEFAULT = DEFAULTS['frame_to_skip']
@@ -86,18 +88,18 @@ def find_insert_position(batch_list, parent_index, parent_seq_num):
 
 # --- Auto change note ---
 
-def _auto_change_note(htree, batch_list, state=None, file_path=None):
+def _auto_change_note(timeline, batch_list, state=None, file_path=None):
     """Compare current batch_list against last snapshot and describe changes."""
-    # Get previous batch data from the current head
+    # Get previous batch data from the current snapshot
-    if not htree.head_id or htree.head_id not in htree.nodes:
+    if not timeline.current_id or timeline.current_id not in timeline.snapshots:
         return f'Initial save ({len(batch_list)} sequences)'
 
-    # Load previous snapshot from DB (nodes no longer hold data in memory)
+    # Load previous snapshot from inline data or DB
-    prev_data = htree.nodes[htree.head_id].get('data')
+    prev_data = timeline.get_snapshot_data(timeline.current_id)
     if not prev_data and state and state.db_enabled and state.db and state.current_project and file_path:
         df = state.db.get_data_file_by_names(state.current_project, file_path.stem)
         if df:
-            prev_data = state.db.get_node_snapshot(df['id'], htree.head_id)
+            prev_data = state.db.get_node_snapshot(df['id'], timeline.current_id)
     prev_batch = (prev_data or {}).get(KEY_BATCH_DATA, [])
 
     prev_by_seq = {int(s.get(KEY_SEQUENCE_NUMBER, 0)): s for s in prev_batch}
@@ -363,38 +365,34 @@ def render_batch_processor(state: AppState):
                 logger.info("save_and_snap START")
                 data[KEY_BATCH_DATA] = batch_list
                 tree_data = data.get(KEY_HISTORY_TREE, {})
-                htree = HistoryTree(tree_data)
+                timeline = SnapshotTimeline(tree_data)
-                note = commit_input.value if commit_input.value else _auto_change_note(htree, batch_list, state=state, file_path=file_path)
+                note = commit_input.value if commit_input.value else _auto_change_note(timeline, batch_list, state=state, file_path=file_path)
                 # Single serialization: json roundtrip gives us an isolated snapshot
-                # without the expensive deepcopy
                 t1 = time.perf_counter()
                 snapshot_json = json.dumps({k: v for k, v in data.items()
                                             if k != KEY_HISTORY_TREE})
                 snapshot_payload = json.loads(snapshot_json)
                 logger.info("save_and_snap snapshot %.3fs", time.perf_counter() - t1)
                 try:
-                    htree.commit(snapshot_payload, note=note)
+                    timeline.record(snapshot_payload, note=note)
                 except ValueError as e:
                     ui.notify(f'Save failed: {e}', type='negative')
                     return
                 if state.db_enabled and state.current_project and state.db:
-                    # DB path: sync full tree (with snapshots) to DB, then
+                    full_tree = timeline.to_dict()
-                    # write slim tree (no snapshots) to JSON and memory
-                    full_tree = htree.to_dict()
                     data[KEY_HISTORY_TREE] = full_tree
                     t1 = time.perf_counter()
                     db_snapshot = json.loads(json.dumps(data))
                     await asyncio.to_thread(sync_to_db, state.db, state.current_project, file_path, db_snapshot)
                     logger.info("save_and_snap sync_to_db %.3fs", time.perf_counter() - t1)
-                    htree.strip_snapshots()
+                    timeline.strip_snapshots()
-                    data[KEY_HISTORY_TREE] = htree.to_dict()
+                    data[KEY_HISTORY_TREE] = timeline.to_dict()
                     t1 = time.perf_counter()
                     slim_snapshot = json.loads(json.dumps(data))
                     await asyncio.to_thread(save_json, file_path, slim_snapshot)
                     logger.info("save_and_snap save_json %.3fs", time.perf_counter() - t1)
                 else:
-                    # No DB: write full tree (with snapshots) to JSON
+                    data[KEY_HISTORY_TREE] = timeline.to_dict()
-                    data[KEY_HISTORY_TREE] = htree.to_dict()
                     t1 = time.perf_counter()
                     save_snapshot = json.loads(json.dumps(data))
                     await asyncio.to_thread(save_json, file_path, save_snapshot)
@@ -416,9 +414,30 @@ def _render_sequence_card(i, seq, batch_list, data, file_path, state,
                           refresh_list):
     async def commit(message=None):
         data[KEY_BATCH_DATA] = batch_list
+        # Auto-snapshot with debounce
+        fp_key = str(file_path)
+        now = time.time()
+        did_snap = False
+        if now - _last_auto_snap.get(fp_key, 0) >= _AUTO_SNAP_DEBOUNCE:
+            timeline = SnapshotTimeline(data.get(KEY_HISTORY_TREE, {}))
+            snap_json = json.dumps({k: v for k, v in data.items()
+                                    if k != KEY_HISTORY_TREE})
+            snap_payload = json.loads(snap_json)
+            try:
+                timeline.record(snap_payload, note=message or "Auto-save", auto=True)
+                if state.db_enabled and state.current_project and state.db:
+                    data[KEY_HISTORY_TREE] = timeline.to_dict()
+                    db_snap = json.loads(json.dumps(data))
+                    await asyncio.to_thread(sync_to_db, state.db, state.current_project, file_path, db_snap)
+                    timeline.strip_snapshots()
+                    did_snap = True
+                data[KEY_HISTORY_TREE] = timeline.to_dict()
+                _last_auto_snap[fp_key] = now
+            except ValueError:
+                pass  # Non-critical: skip auto-snapshot on ID collision
         snapshot = json.loads(json.dumps(data))
         await asyncio.to_thread(save_json, file_path, snapshot)
-        if state.db_enabled and state.current_project and state.db:
+        if state.db_enabled and state.current_project and state.db and not did_snap:
             await asyncio.to_thread(sync_to_db, state.db, state.current_project, file_path, snapshot)
         if message:
             ui.notify(message, type='positive')
@@ -845,26 +864,26 @@ def _render_mass_update(batch_list, data, file_path, state: AppState, refresh_li
                     batch_list[idx][key] = copy.deepcopy(source_seq.get(key))
 
             data[KEY_BATCH_DATA] = batch_list
-            htree = HistoryTree(data.get(KEY_HISTORY_TREE, {}))
+            timeline = SnapshotTimeline(data.get(KEY_HISTORY_TREE, {}))
             snapshot_json = json.dumps({k: v for k, v in data.items()
                                         if k != KEY_HISTORY_TREE})
             snapshot = json.loads(snapshot_json)
             try:
-                htree.commit(snapshot, f"Mass update: {', '.join(selected_keys)}")
+                timeline.record(snapshot, f"Mass update: {', '.join(selected_keys)}")
             except ValueError as e:
                 ui.notify(f'Mass update failed: {e}', type='negative')
                 return
             if state.db_enabled and state.current_project and state.db:
-                full_tree = htree.to_dict()
+                full_tree = timeline.to_dict()
                 data[KEY_HISTORY_TREE] = full_tree
                 db_snapshot = json.loads(json.dumps(data))
                 await asyncio.to_thread(sync_to_db, state.db, state.current_project, file_path, db_snapshot)
-                htree.strip_snapshots()
+                timeline.strip_snapshots()
-                data[KEY_HISTORY_TREE] = htree.to_dict()
+                data[KEY_HISTORY_TREE] = timeline.to_dict()
                 slim_snapshot = json.loads(json.dumps(data))
                 await asyncio.to_thread(save_json, file_path, slim_snapshot)
             else:
-                data[KEY_HISTORY_TREE] = htree.to_dict()
+                data[KEY_HISTORY_TREE] = timeline.to_dict()
                 save_snapshot = json.loads(json.dumps(data))
                 await asyncio.to_thread(save_json, file_path, save_snapshot)
             ui.notify(f'Updated {len(targets)} sequences', type='positive')

tests/test_db.py

@@ -208,10 +208,10 @@ class TestHistoryTrees:
     def test_upsert_updates(self, db):
         pid = db.create_project("p1", "/p1")
         df_id = db.create_data_file(pid, "batch", "generic")
-        db.save_history_tree(df_id, {"v": 1})
+        db.save_history_tree(df_id, {"snapshots": {}, "v": 1})
-        db.save_history_tree(df_id, {"v": 2})
+        db.save_history_tree(df_id, {"snapshots": {}, "v": 2})
         result = db.get_history_tree(df_id)
-        assert result == {"v": 2}
+        assert result == {"snapshots": {}, "v": 2}
 
     def test_get_nonexistent(self, db):
         pid = db.create_project("p1", "/p1")

tests/test_snapshot_timeline.py

@@ -0,0 +1,159 @@
+import pytest
+from snapshot_timeline import SnapshotTimeline, diff_snapshots
+
+
+def test_record_creates_snapshot():
+    tl = SnapshotTimeline({})
+    sid = tl.record({"batch_data": [{"seed": 42}]}, note="first")
+    assert sid in tl.snapshots
+    assert tl.current_id == sid
+    assert tl.snapshots[sid]["note"] == "first"
+    assert tl.snapshots[sid]["auto"] is False
+    assert tl.snapshots[sid]["seq_count"] == 1
+
+
+def test_record_auto_flag():
+    tl = SnapshotTimeline({})
+    sid = tl.record({"batch_data": []}, note="auto save", auto=True)
+    assert tl.snapshots[sid]["auto"] is True
+
+
+def test_multiple_records():
+    tl = SnapshotTimeline({})
+    id1 = tl.record({"batch_data": [{"a": 1}]}, note="one")
+    id2 = tl.record({"batch_data": [{"b": 2}]}, note="two")
+    assert len(tl.snapshots) == 2
+    assert tl.current_id == id2
+
+
+def test_to_dict_roundtrip():
+    tl = SnapshotTimeline({})
+    tl.record({"batch_data": [{"x": 1}]}, note="test")
+    d = tl.to_dict()
+    tl2 = SnapshotTimeline(d)
+    assert tl2.current_id == tl.current_id
+    assert set(tl2.snapshots.keys()) == set(tl.snapshots.keys())
+
+
+def test_migrate_from_history_tree():
+    """Old HistoryTree format should be flattened into snapshots."""
+    old_data = {
+        "nodes": {
+            "aaa": {"id": "aaa", "parent": None, "timestamp": 1000, "note": "First", "data": {"batch_data": [{"seed": 1}]}},
+            "bbb": {"id": "bbb", "parent": "aaa", "timestamp": 2000, "note": "Second", "data": {"batch_data": [{"seed": 2}]}},
+        },
+        "branches": {"main": "bbb"},
+        "head_id": "bbb",
+    }
+    tl = SnapshotTimeline(old_data)
+    assert len(tl.snapshots) == 2
+    assert tl.current_id == "bbb"
+    assert tl.snapshots["aaa"]["note"] == "First"
+    assert tl.snapshots["bbb"]["note"] == "Second"
+    # Data should be preserved
+    assert tl.snapshots["aaa"]["data"]["batch_data"] == [{"seed": 1}]
+
+
+def test_migrate_from_history_tree_no_data():
+    """Slim tree nodes (no inline data) should still migrate."""
+    old_data = {
+        "nodes": {
+            "aaa": {"id": "aaa", "parent": None, "timestamp": 1000, "note": "First"},
+        },
+        "branches": {"main": "aaa"},
+        "head_id": "aaa",
+    }
+    tl = SnapshotTimeline(old_data)
+    assert len(tl.snapshots) == 1
+    assert tl.snapshots["aaa"]["seq_count"] == 0
+
+
+def test_migrate_legacy_prompt_history():
+    legacy = {
+        "prompt_history": [
+            {"note": "A", "seed": 1},
+            {"note": "B", "seed": 2},
+        ]
+    }
+    tl = SnapshotTimeline(legacy)
+    assert len(tl.snapshots) == 2
+    assert tl.current_id is not None
+
+
+def test_toggle_pin():
+    tl = SnapshotTimeline({})
+    sid = tl.record({"batch_data": []}, note="test")
+    assert tl.snapshots[sid]["pinned"] is False
+    result = tl.toggle_pin(sid)
+    assert result is True
+    assert tl.snapshots[sid]["pinned"] is True
+    result = tl.toggle_pin(sid)
+    assert result is False
+
+
+def test_delete_snapshot():
+    tl = SnapshotTimeline({})
+    id1 = tl.record({"batch_data": []}, note="one")
+    id2 = tl.record({"batch_data": []}, note="two")
+    tl.delete(id2)
+    assert id2 not in tl.snapshots
+    assert tl.current_id == id1
+
+
+def test_delete_all_snapshots():
+    tl = SnapshotTimeline({})
+    sid = tl.record({"batch_data": []}, note="only")
+    tl.delete(sid)
+    assert len(tl.snapshots) == 0
+    assert tl.current_id is None
+
+
+def test_strip_snapshots():
+    tl = SnapshotTimeline({})
+    tl.record({"batch_data": [{"a": 1}]}, note="test")
+    tl.strip_snapshots()
+    for snap in tl.snapshots.values():
+        assert "data" not in snap
+
+
+def test_get_snapshot_data():
+    tl = SnapshotTimeline({})
+    sid = tl.record({"batch_data": [{"x": 1}]}, note="test")
+    data = tl.get_snapshot_data(sid)
+    assert data == {"batch_data": [{"x": 1}]}
+    assert tl.get_snapshot_data("nonexistent") is None
+
+
+# --- diff_snapshots tests ---
+
+def test_diff_unchanged():
+    batch = [{"sequence_number": 1, "seed": 42}]
+    result = diff_snapshots(batch, batch)
+    assert len(result) == 1
+    assert result[0]["status"] == "unchanged"
+    assert result[0]["changes"] == []
+
+
+def test_diff_changed():
+    old = [{"sequence_number": 1, "seed": 42, "cfg": 1.5}]
+    new = [{"sequence_number": 1, "seed": 99, "cfg": 1.5}]
+    result = diff_snapshots(old, new)
+    assert result[0]["status"] == "changed"
+    assert len(result[0]["changes"]) == 1
+    assert result[0]["changes"][0]["field"] == "seed"
+    assert result[0]["changes"][0]["old"] == 42
+    assert result[0]["changes"][0]["new"] == 99
+
+
+def test_diff_added_and_removed():
+    old = [{"sequence_number": 1, "seed": 1}]
+    new = [{"sequence_number": 2, "seed": 2}]
+    result = diff_snapshots(old, new)
+    assert len(result) == 2
+    statuses = {r["seq_num"]: r["status"] for r in result}
+    assert statuses[1] == "removed"
+    assert statuses[2] == "added"
+
+
+def test_diff_empty():
+    assert diff_snapshots([], []) == []

utils.py

@@ -305,38 +305,47 @@ def sync_to_db(db, project_name: str, file_path: Path, data: dict) -> None:
                 else:
                     db.conn.execute("DELETE FROM sequences WHERE data_file_id = ?", (df_id,))
 
-            # Sync history tree (extract node snapshots into separate table)
+            # Sync history tree (extract snapshot data into separate table)
+            # Supports both new format (snapshots dict) and old format (nodes dict)
             history_tree = data.get(KEY_HISTORY_TREE)
             if history_tree and isinstance(history_tree, dict):
-                nodes = history_tree.get("nodes", {})
+                # Detect format: new has "snapshots", old has "nodes"
+                if "snapshots" in history_tree:
+                    entries = history_tree.get("snapshots", {})
+                else:
+                    entries = history_tree.get("nodes", {})
                 slim_tree = dict(history_tree)
-                slim_nodes = {}
+                slim_entries = {}
-                for nid, node in nodes.items():
+                for eid, entry in entries.items():
-                    snap = node.get("data")
+                    snap = entry.get("data")
                     if snap:
                         db.conn.execute(
                             "INSERT INTO history_snapshots (data_file_id, node_id, snapshot_data, updated_at) "
                             "VALUES (?, ?, ?, ?) "
                             "ON CONFLICT(data_file_id, node_id) DO UPDATE SET "
                             "snapshot_data=excluded.snapshot_data, updated_at=excluded.updated_at",
-                            (df_id, nid, json.dumps(snap), now),
+                            (df_id, eid, json.dumps(snap), now),
                         )
-                    slim_nodes[nid] = {k: v for k, v in node.items() if k != "data"}
+                    slim_entries[eid] = {k: v for k, v in entry.items() if k != "data"}
-                slim_tree["nodes"] = slim_nodes
+                # Write back slim version using the correct key
+                if "snapshots" in history_tree:
+                    slim_tree["snapshots"] = slim_entries
+                else:
+                    slim_tree["nodes"] = slim_entries
                 db.conn.execute(
                     "INSERT INTO history_trees (data_file_id, tree_data, updated_at) "
                     "VALUES (?, ?, ?) "
                     "ON CONFLICT(data_file_id) DO UPDATE SET tree_data=excluded.tree_data, updated_at=excluded.updated_at",
                     (df_id, json.dumps(slim_tree), now),
                 )
-                # Clean up orphaned snapshots for nodes no longer in tree
+                # Clean up orphaned snapshots
-                current_node_ids = set(nodes.keys())
+                current_ids = set(entries.keys())
-                if current_node_ids:
+                if current_ids:
-                    placeholders = ",".join("?" for _ in current_node_ids)
+                    placeholders = ",".join("?" for _ in current_ids)
                     db.conn.execute(
                         f"DELETE FROM history_snapshots WHERE data_file_id = ? "
                         f"AND node_id NOT IN ({placeholders})",
-                        (df_id, *current_node_ids),
+                        (df_id, *current_ids),
                     )
                 else:
                     db.conn.execute(