MCP: cancelled exports delete only their own files

remove_partial removed every '<stem>[digits].<any ext>' file in the output folder modified since the export started, so cancelling an export to trailer.mp4 also deleted trailer.aep or trailer2.psd if they were saved during the export. It now removes only the output file, numbered stills with the output's extension, and the .srt/.vtt caption sidecar. Regression test with decoy files.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/automation/src/long_job.rs

@@ -106,21 +106,78 @@ impl FilmcraftMcp {
     }
 }
 
-/// Delete what an interrupted export wrote: the output file and, for image sequences and caption
-/// sidecars, the files next to it named `<stem>[digits].<ext>` — only those written since `since`.
+/// Delete what an interrupted export wrote, and nothing else: the output file itself, the numbered
+/// stills of an image sequence (`<stem><digits>.<same extension>`) and the caption sidecar
+/// (`<stem>.srt` / `<stem>.vtt`), each only if it was written since `since`. Other files that
+/// merely share the name's stem (`<stem>.aep`, `<stem>2.psd`, …) are never touched, even when they
+/// were saved during the export.
 pub fn remove_partial(path: &str, since: SystemTime) {
     let p = Path::new(path);
-    let (Some(dir), Some(stem)) = (p.parent(), p.file_stem().map(|s| s.to_string_lossy().to_string())) else { return };
+    let (Some(dir), Some(stem), Some(file)) = (p.parent(), p.file_stem().and_then(|s| s.to_str()), p.file_name().and_then(|s| s.to_str())) else {
+        return;
+    };
+    let ext = p.extension().and_then(|s| s.to_str()).unwrap_or_default();
     let dir = if dir.as_os_str().is_empty() { Path::new(".") } else { dir };
     let Ok(entries) = std::fs::read_dir(dir) else { return };
     // file times are coarser than the clock
     let since = since.checked_sub(Duration::from_secs(1)).unwrap_or(since);
     for e in entries.flatten() {
-        let name = e.file_name().to_string_lossy().to_string();
-        let sibling = name.strip_prefix(&stem).is_some_and(|rest| rest.trim_start_matches(|c: char| c.is_ascii_digit()).starts_with('.'));
-        let ours = sibling && e.metadata().is_ok_and(|m| m.is_file() && m.modified().is_ok_and(|t| t >= since));
-        if ours {
+        let name = e.file_name();
+        let Some(name) = name.to_str() else { continue };
+        if is_export_output(name, file, stem, ext) && e.metadata().is_ok_and(|m| m.is_file() && m.modified().is_ok_and(|t| t >= since)) {
             let _ = std::fs::remove_file(e.path());
         }
     }
 }
+
+/// Whether `name` is a file an export to `file` (`stem` + `.ext`) writes.
+fn is_export_output(name: &str, file: &str, stem: &str, ext: &str) -> bool {
+    if name == file {
+        return true;
+    }
+    let Some(rest) = name.strip_prefix(stem) else { return false };
+    if let Some(sidecar) = rest.strip_prefix('.') {
+        return sidecar.eq_ignore_ascii_case("srt") || sidecar.eq_ignore_ascii_case("vtt");
+    }
+    // image sequence: one or more digits, then the output's own extension
+    let digits = rest.len() - rest.trim_start_matches(|c: char| c.is_ascii_digit()).len();
+    digits > 0 && !ext.is_empty() && rest.get(digits..).is_some_and(|r| r.strip_prefix('.').is_some_and(|x| x == ext))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn only_the_exports_own_files_are_removed() {
+        let dir = std::env::temp_dir().join(format!("fc-remove-partial-{}", std::process::id()));
+        let _ = std::fs::remove_dir_all(&dir);
+        std::fs::create_dir_all(&dir).unwrap();
+        let started = SystemTime::now();
+        let ours = ["trailer.png", "trailer000.png", "trailer123.png", "trailer.srt", "trailer.vtt"];
+        // same stem, written during the export, but not the export's
+        let theirs = ["trailer.aep", "trailer2.psd", "trailer.docx", "trailer000.jpg", "trailers.png", "trailer.png.bak", "other.png"];
+        for f in ours.iter().chain(theirs.iter()) {
+            std::fs::write(dir.join(f), b"x").unwrap();
+        }
+        remove_partial(&dir.join("trailer.png").to_string_lossy(), started);
+        for f in ours {
+            assert!(!dir.join(f).exists(), "{f} should be removed");
+        }
+        for f in theirs {
+            assert!(dir.join(f).exists(), "{f} must not be removed");
+        }
+        let _ = std::fs::remove_dir_all(&dir);
+    }
+
+    #[test]
+    fn files_older_than_the_export_are_kept() {
+        let dir = std::env::temp_dir().join(format!("fc-remove-partial-old-{}", std::process::id()));
+        let _ = std::fs::remove_dir_all(&dir);
+        std::fs::create_dir_all(&dir).unwrap();
+        std::fs::write(dir.join("clip.mp4"), b"x").unwrap();
+        remove_partial(&dir.join("clip.mp4").to_string_lossy(), SystemTime::now() + Duration::from_secs(60));
+        assert!(dir.join("clip.mp4").exists());
+        let _ = std::fs::remove_dir_all(&dir);
+    }
+}