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+# Timeline Markers Design
+
+## Overview
+
+When a file is loaded that matches a previously processed source, numbered markers appear on the timeline at the exact positions where clips were previously extracted. Hovering over a marker shows the output path of that export.
+
+## DB Schema Change
+
+Drop the `UNIQUE` constraint on `filename` and add `start_time` and `output_path` columns:
+
+```sql
+CREATE TABLE processed (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    filename TEXT NOT NULL,
+    start_time REAL NOT NULL,
+    output_path TEXT NOT NULL,
+    processed_at TEXT NOT NULL
+)
+```
+
+Multiple rows per source filename are now allowed (one per export).
+
+**Migration:** On startup, detect the old schema via `PRAGMA table_info(processed)`. If `start_time` column is missing, drop and recreate the table. Data from the old schema is lost (acceptable — it only stored filenames, not positions).
+
+## New DB Methods
+
+- `add(filename, start_time, output_path)` — inserts a new row; no deduplication (accumulates all exports)
+- `get_markers(filename) -> list[tuple[float, int, str]]` — finds the best fuzzy-similar filename in the DB, fetches all its rows ordered by `start_time`, returns `[(start_time, marker_number, output_path), ...]` (1-indexed)
+
+Existing `find_similar` is kept unchanged for the status bar warning.
+
+## TimelineWidget Changes
+
+- `set_markers(markers: list[tuple[float, int, str]])` — stores marker list, calls `update()`
+- `paintEvent`: for each marker, draws a red vertical line at the corresponding x position + the marker number in small white text above the line
+- `mouseMoveEvent`: checks if mouse x is within ±4px of any marker's x. If yes, calls `QToolTip.showText(QCursor.pos(), output_path)`. Otherwise hides the tooltip.
+
+## MainWindow Changes
+
+- `_after_load`: calls `db.get_markers(basename)` and passes result to `timeline.set_markers()`
+- `_on_export_done`: calls `db.add(filename, cursor, output_path)` (now with start_time and output_path), then refreshes markers on the timeline immediately via `db.get_markers` + `timeline.set_markers`