Auto-rename safety net: never strip valid SxxExx episode token

Real-world scenario from user logs: package "Drei.Meter.ueber.dem.Himmel.
S01GERMAN.DL.720P.WEB.X264-WAYNE" (note malformed S01GERMAN with no
separator) caused the auto-renamer to strip the source's S01E01..S01E08
episode tokens because SCENE_SEASON_ONLY_RE doesn't match a season followed
by an immediate letter (no separator).

Result: all 8 episodes in the season pack collapsed to the same target name
and collided in the MKV library with (2)(3)(4)(5)(6)(7)(8) suffixes.

Fix: After buildAutoRenameBaseNameFromFoldersWithOptions, check if the
source filename has a valid episode token. If yes:
  1. If target has NO episode token: try to insert it via regex replacement
     (Sxx<garbage> -> SxxExx.<garbage>), then via applyEpisodeTokenToFolderName.
     If both fail, skip the rename entirely (preserve source name).
  2. If target has a DIFFERENT episode token: skip the rename (mislabel risk).

This guard is the last line of defense against the helper's regex
limitations on malformed package names.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/main/download-manager.ts

@@ -3465,7 +3465,7 @@ export class DownloadManager extends EventEmitter {
           folderCandidates.push(extra);
         }
       }
-      const targetBaseName = buildAutoRenameBaseNameFromFoldersWithOptions(folderCandidates, sourceBaseName, {
+      let targetBaseName = buildAutoRenameBaseNameFromFoldersWithOptions(folderCandidates, sourceBaseName, {
         forceEpisodeForSeasonFolder: true
       });
       const resolveRenameItem = (...extra: Array<string | null | undefined>): { item: DownloadItem | null; matchedBy: string | null } => {
@@ -3474,6 +3474,60 @@ export class DownloadManager extends EventEmitter {
         }
         return this.inferItemForMediaLog(pkg, sourcePath, sourceName, folderCandidates.join(" "), targetBaseName || "", ...extra);
       };
+      // SAFETY NET: Never strip a valid SxxExx token from the source filename.
+      // If the source already has an episode token but the computed target lost it
+      // (e.g. malformed package name "S01GERMAN" with no separator), preserve the
+      // episode by either inserting it into the target or skipping the rename entirely.
+      // Without this guard, all episodes from a malformed pack collapse to one name
+      // and collide with (2)(3)(4) suffixes in the MKV library.
+      const sourceEpisodeToken = extractEpisodeToken(sourceBaseName);
+      if (targetBaseName && sourceEpisodeToken) {
+        const targetEpisodeToken = extractEpisodeToken(targetBaseName);
+        if (!targetEpisodeToken) {
+          // Try to insert the source's episode token: replace "Sxx<garbage>" with "SxxExx.<garbage>"
+          const insertedEpisode = targetBaseName.replace(
+            /(^|[._\-\s])(s\d{1,2})(?=[A-Za-z0-9])/i,
+            `$1${sourceEpisodeToken}.`
+          );
+          if (insertedEpisode !== targetBaseName && extractEpisodeToken(insertedEpisode)) {
+            logger.info(`Auto-Rename Safety: Episode-Token in Target eingefuegt: ${targetBaseName} -> ${insertedEpisode}`);
+            targetBaseName = insertedEpisode;
+          } else {
+            const repaired = applyEpisodeTokenToFolderName(targetBaseName, sourceEpisodeToken);
+            if (repaired && extractEpisodeToken(repaired)) {
+              logger.info(`Auto-Rename Safety: Episode-Token via applyToken: ${targetBaseName} -> ${repaired}`);
+              targetBaseName = repaired;
+            } else {
+              logger.warn(`Auto-Rename Safety: Skipping rename - target wuerde Episode-Token verlieren (source=${sourceBaseName}, target=${targetBaseName})`);
+              if (pkg) {
+                const resolved = resolveRenameItem();
+                this.logRenameProcess(pkg, "WARN", "auto-rename", "Auto-Rename uebersprungen: Episode-Token wuerde verloren gehen", {
+                  sourcePath,
+                  sourceName,
+                  sourceEpisodeToken,
+                  targetBaseName
+                }, resolved.item, resolved.matchedBy);
+              }
+              continue;
+            }
+          }
+        } else if (targetEpisodeToken !== sourceEpisodeToken) {
+          // Target has a DIFFERENT episode token than source — that's a clear sign
+          // the rename is wrong (would mislabel the episode). Skip to be safe.
+          logger.warn(`Auto-Rename Safety: Skipping rename - Episode-Token Mismatch (source=${sourceEpisodeToken}, target=${targetEpisodeToken})`);
+          if (pkg) {
+            const resolved = resolveRenameItem();
+            this.logRenameProcess(pkg, "WARN", "auto-rename", "Auto-Rename uebersprungen: Episode-Token Mismatch", {
+              sourcePath,
+              sourceName,
+              sourceEpisodeToken,
+              targetEpisodeToken,
+              targetBaseName
+            }, resolved.item, resolved.matchedBy);
+          }
+          continue;
+        }
+      }
       if (!targetBaseName) {
         if (pkg) {
           this.logPackageForPackage(pkg, "WARN", "Auto-Rename übersprungen: kein Zielname", {

tests/auto-rename.test.ts

@@ -762,4 +762,25 @@ describe("buildAutoRenameBaseNameFromFolders", () => {
     );
     expect(result).toBe("9JKL.S01E14.GERMAN.720p.WEB.x264-WvF");
   });
+
+  it("documents malformed package name (S01GERMAN) limitation", () => {
+    // Real-world: "Drei.Meter.ueber.dem.Himmel.S01GERMAN.DL.720P.WEB.X264-WAYNE"
+    // is malformed (no separator between S01 and GERMAN). SCENE_SEASON_ONLY_RE
+    // doesn't match this, so the helper falls back to the package name as-is.
+    // The download-manager autoRenameExtractedVideoFiles safety net repairs
+    // this at runtime by inserting the source's episode token.
+    const result = buildAutoRenameBaseNameFromFoldersWithOptions(
+      [
+        "3MH.web.7p-101",
+        "Drei.Meter.ueber.dem.Himmel.S01GERMAN.DL.720P.WEB.X264-WAYNE"
+      ],
+      "Drei.Meter.ueber.dem.Himmel.S01E01.GERMAN.DL.720P.WEB.X264-WAYNE",
+      { forceEpisodeForSeasonFolder: true }
+    );
+    // Helper limitation: returns the malformed folder name unchanged.
+    // The download-manager safety net catches this at runtime.
+    if (result !== null) {
+      expect(typeof result).toBe("string");
+    }
+  });
 });