diff --git a/lib/log-mode.js b/lib/log-mode.js
index b3b876c..2bb7987 100644
--- a/lib/log-mode.js
+++ b/lib/log-mode.js
@@ -75,7 +75,29 @@
     return `${base}${ext}`;
   }
 
-  const api = { normalizeLogMode, resolveLogFileName, formatDateStamp, formatSessionStamp, VALID_MODES };
+  /**
+   * Reverse of resolveLogFileName: given a full filename like
+   * "fileuploader-2026-06-03.log" or
+   * "fileuploader-session-2026-06-03_18-16-20-8132.log", strip the mode-stamp
+   * so the bare base ("fileuploader.log") remains. Used when persisting an
+   * auto-resolved fallback path back into config — otherwise the saved path
+   * would keep growing a new stamp on every reload.
+   */
+  function stripModeStampFromFileName(fileName) {
+    if (!fileName || typeof fileName !== 'string') return fileName;
+    // Order matters: session first (longer, more specific) before daily.
+    // Both regexes are anchored to $ with no nested/ambiguous quantifiers, so
+    // matching is linear — the eslint security warning is precautionary.
+    // eslint-disable-next-line security/detect-unsafe-regex
+    const sessionRe = /-session-\d{4}-\d{2}-\d{2}_\d{2}-\d{2}-\d{2}(?:-\d+)?(\.[^.]+)?$/;
+    // eslint-disable-next-line security/detect-unsafe-regex
+    const dailyRe = /-\d{4}-\d{2}-\d{2}(\.[^.]+)?$/;
+    let out = fileName.replace(sessionRe, (m, ext) => ext || '');
+    out = out.replace(dailyRe, (m, ext) => ext || '');
+    return out;
+  }
+
+  const api = { normalizeLogMode, resolveLogFileName, formatDateStamp, formatSessionStamp, stripModeStampFromFileName, VALID_MODES };
 
   if (typeof module !== 'undefined' && module.exports) {
     module.exports = api;
diff --git a/main.js b/main.js
index 4b0b8b4..e28f245 100644
--- a/main.js
+++ b/main.js
@@ -245,7 +245,7 @@ function getBaseLogFilePath() {
 // given session lands in the same file. A close→reopen of the app starts a new
 // main process, so a new SESSION_ID, so a new session file. PID is appended as
 // a cheap hedge against same-second restart collisions.
-const { resolveLogFileName, formatSessionStamp, formatDateStamp } = require('./lib/log-mode');
+const { resolveLogFileName, formatSessionStamp, formatDateStamp, stripModeStampFromFileName } = require('./lib/log-mode');
 const SESSION_ID = formatSessionStamp(new Date(), process.pid);
 let _activeLogKey = null;   // remembers (mode + date-or-session) so cache rolls correctly
 let _activeLogPath = null;
@@ -398,16 +398,18 @@ function _persistFallbackLogPath(workingPath) {
   try {
     const cfg = configStore.load();
     const gs = cfg.globalSettings || {};
-    // If daily-log is on, workingPath has a date suffix (fileuploader-YYYY-MM-DD.log).
-    // Strip that before saving so the base path rolls forward to tomorrow's
-    // file correctly — otherwise the next day's getLogFilePath would append
-    // another date onto the already-dated base.
+    const mode = gs.logMode || 'single';
+    // Strip the mode-specific suffix so logFilePath stores the BARE base path.
+    // Otherwise daily would compound into "...-2026-06-03-2026-06-04.log" and
+    // session would compound a second session-stamp onto the first — which split
+    // a session's lines across two files (the first few before _persistFallback
+    // ran, the rest after, into the doubly-stamped path). gated on logMode (the
+    // legacy `sessionLog` field is no longer the source of truth).
     let toSave = workingPath;
-    if (gs.sessionLog) {
+    if (mode === 'daily' || mode === 'session') {
       const dir = path.dirname(workingPath);
       const base = path.basename(workingPath);
-      const stripped = base.replace(/-\d{4}-\d{2}-\d{2}(\.[^.]+)$/, '$1');
-      toSave = path.join(dir, stripped);
+      toSave = path.join(dir, stripModeStampFromFileName(base));
     }
     if (gs.logFilePath === toSave) return;
     gs.logFilePath = toSave;
diff --git a/tests/log-mode.test.js b/tests/log-mode.test.js
index b686afc..86cf29f 100644
--- a/tests/log-mode.test.js
+++ b/tests/log-mode.test.js
@@ -78,6 +78,50 @@ test('resolveLogFileName: unknown mode is treated as single', () => {
   );
 });
 
+// --- stripModeStampFromFileName ---
+
+const { stripModeStampFromFileName } = require('../lib/log-mode');
+
+test('stripModeStampFromFileName: leaves bare names alone', () => {
+  assert.equal(stripModeStampFromFileName('fileuploader.log'), 'fileuploader.log');
+  assert.equal(stripModeStampFromFileName('fileuploader'), 'fileuploader');
+});
+
+test('stripModeStampFromFileName: strips a daily YYYY-MM-DD suffix', () => {
+  assert.equal(stripModeStampFromFileName('fileuploader-2026-06-03.log'), 'fileuploader.log');
+});
+
+test('stripModeStampFromFileName: strips a session-stamp suffix (with and without pid)', () => {
+  assert.equal(
+    stripModeStampFromFileName('fileuploader-session-2026-06-03_18-16-20-8132.log'),
+    'fileuploader.log'
+  );
+  assert.equal(
+    stripModeStampFromFileName('fileuploader-session-2026-06-03_18-16-20.log'),
+    'fileuploader.log'
+  );
+});
+
+test('regression: resolveLogFileName(stripModeStampFromFileName(...)) is idempotent — persisting then re-resolving never compounds stamps', () => {
+  // This is the exact bug shape: persist the resolved path, then on next call
+  // re-resolve from the saved base — must produce the same file, not a doubled
+  // session-stamped one. The fix is the strip; this test guards against
+  // regressing _persistFallbackLogPath into the 3.3.35 bug.
+  const sessionId = '2026-06-03_18-16-20-8132';
+  const dailyDate = new Date(2026, 5, 3);
+  for (const mode of ['daily', 'session']) {
+    const date = mode === 'daily' ? dailyDate : new Date();
+    const initial = resolveLogFileName({ baseName: 'fileuploader', ext: '.log', mode, date, sessionId });
+    const stripped = stripModeStampFromFileName(initial);
+    // After strip, the base should be back to the bare name.
+    assert.equal(stripped, 'fileuploader.log', `${mode}: strip should produce bare base`);
+    // Re-resolving from the bare base gives the same final filename — no doubling.
+    const reBase = stripped.replace(/\.log$/, '');
+    const second = resolveLogFileName({ baseName: reBase, ext: '.log', mode, date, sessionId });
+    assert.equal(second, initial, `${mode}: round-trip must be idempotent`);
+  }
+});
+
 // --- format helpers ---
 
 test('formatDateStamp: zero-pads month and day', () => {