diff --git a/skill/scripts/live-browser.js b/skill/scripts/live-browser.js
index da026e255..c32101b12 100644
--- a/skill/scripts/live-browser.js
+++ b/skill/scripts/live-browser.js
@@ -6216,6 +6216,71 @@
     return /\.[cm]?[jt]sx$/i.test(String(filePath || ''));
   }
 
+  function sourceHasSessionWrapper(text, sessionId) {
+    const src = String(text || '');
+    return src.indexOf('data-impeccable-variants="' + sessionId + '"') !== -1
+      || src.indexOf("data-impeccable-variants='" + sessionId + "'") !== -1
+      || src.indexOf('impeccable-variants-start ' + sessionId) !== -1;
+  }
+
+  /**
+   * Orphan probe for JSX targets (#439 + #454). An unmounted wrapper and a
+   * wrapper deleted from source look identical in the DOM, and only the second
+   * is an orphan, so the DOM alone cannot decide. #454 forbids parsing or
+   * injecting raw JSX; reading the file as plain text and matching the session
+   * marker honors that, because no DOM is ever built from what comes back.
+   * Marker present means the component is simply not mounted right now (a
+   * closed modal, another route) and the variant observer keeps waiting.
+   * Marker absent after the same retry budget the HTML path uses means the
+   * file was edited out from under the session, which no reload, HMR push, or
+   * server restart can repair, so the session self-discards and hands the
+   * surface back to the picker.
+   */
+  function probeJsxWrapperForOrphan(filePath, sessionId, opts) {
+    const attempt = opts._orphanAttempt || 0;
+    const url = 'http://localhost:' + PORT + '/source?token=' + TOKEN + '&path=' + encodeURIComponent(filePath);
+    const stillActive = () => sessionId === currentSessionId && (state === 'GENERATING' || state === 'CYCLING');
+    const retryLater = () => {
+      setTimeout(() => {
+        if (!stillActive()) return;
+        injectVariantsFromSource(filePath, sessionId, { ...opts, _orphanAttempt: attempt + 1 });
+      }, COMPLETED_SOURCE_FALLBACK_RETRY_MS);
+    };
+    // Discarding is durable (the session moves to the discarded phase and the
+    // picker replaces it), so it needs evidence that the wrapper is gone: a
+    // read that answers without the marker, or a 404 (the file itself was
+    // renamed or deleted). Either kind retries on the shared budget first.
+    // A read that fails for any other reason (the server briefly away, a
+    // transient fetch error) says nothing about the wrapper; after the budget
+    // the session is kept, the user told, and the next event retries.
+    const onNoWrapper = (reason) => {
+      if (!stillActive()) return;
+      if (attempt < COMPLETED_SOURCE_FALLBACK_RETRIES) { retryLater(); return; }
+      discardOrphanedSession(reason);
+    };
+    const onUnreadable = (detail) => {
+      if (!stillActive()) return;
+      if (attempt < COMPLETED_SOURCE_FALLBACK_RETRIES) { retryLater(); return; }
+      console.warn('[impeccable] Could not read source to check the variant wrapper; keeping the session: ' + detail);
+      showToast('Could not read the source file to check this session; it stays open and is checked again on the next event.', 5500);
+    };
+    fetch(url)
+      .then(r => { if (!r.ok) throw new Error('source read failed: ' + r.status); return r.text(); })
+      .then(text => {
+        if (!stillActive()) return;
+        if (sourceHasSessionWrapper(text, sessionId)) return;
+        onNoWrapper('variant wrapper missing from source');
+      })
+      .catch(err => {
+        const detail = err && err.message ? err.message : 'fetch failed';
+        if (/source read failed: 404$/.test(detail)) {
+          onNoWrapper('source file missing (404) while checking for the variant wrapper');
+          return;
+        }
+        onUnreadable(detail);
+      });
+  }
+
   function completeSourceInjection(wrapper, sessionId, opts) {
     recoveryWaitingForAnchor = false;
     if (pendingVariantAnchorRetryObserver) {
@@ -6326,14 +6391,7 @@
         return;
       }
       if (opts.orphanDiscard && !liveWrapper && sessionId === currentSessionId) {
-        const attempt = opts._orphanAttempt || 0;
-        if (attempt < COMPLETED_SOURCE_FALLBACK_RETRIES) {
-          setTimeout(() => {
-            if (sessionId !== currentSessionId) return;
-            if (state !== 'GENERATING' && state !== 'CYCLING') return;
-            injectVariantsFromSource(filePath, sessionId, { ...opts, _orphanAttempt: attempt + 1 });
-          }, COMPLETED_SOURCE_FALLBACK_RETRY_MS);
-        }
+        probeJsxWrapperForOrphan(filePath, sessionId, opts);
       }
       return;
     }
diff --git a/tests/live-browser-source.test.mjs b/tests/live-browser-source.test.mjs
index e93dbff86..0617806f8 100644
--- a/tests/live-browser-source.test.mjs
+++ b/tests/live-browser-source.test.mjs
@@ -555,7 +555,7 @@ describe('live-browser source contracts', () => {
 
   it('never DOMParser-injects JSX source (#454)', () => {
     const isJsxStart = SOURCE.indexOf('function isJsxSourceFile(');
-    const isJsxEnd = SOURCE.indexOf('function completeSourceInjection', isJsxStart);
+    const isJsxEnd = SOURCE.indexOf('function sourceHasSessionWrapper(', isJsxStart);
     const isJsxSourceFile = new Function(
       SOURCE.slice(isJsxStart, isJsxEnd) + '\nreturn isJsxSourceFile;',
     )();
@@ -580,7 +580,12 @@ describe('live-browser source contracts', () => {
     assert.doesNotMatch(
       jsxGate,
       /discardOrphanedSession/,
-      'a missing JSX wrap must wait for mount, not discard as an orphan',
+      'a missing JSX wrap must not discard from the DOM alone; only the source probe may decide',
+    );
+    assert.match(
+      jsxGate,
+      /if \(opts\.orphanDiscard && !liveWrapper && sessionId === currentSessionId\) \{\s*probeJsxWrapperForOrphan\(filePath, sessionId, opts\);/,
+      'a resumed CYCLING session with no mounted JSX wrapper must run the source orphan probe (#439)',
     );
     assert.match(
       jsxGate,
@@ -606,6 +611,64 @@ describe('live-browser source contracts', () => {
     );
   });
 
+  it('self-discards a JSX session whose wrapper left the source file (#439)', () => {
+    const probeStart = SOURCE.indexOf('function probeJsxWrapperForOrphan(');
+    assert.ok(probeStart !== -1, 'the JSX orphan probe must exist');
+    const probeEnd = SOURCE.indexOf('function completeSourceInjection', probeStart);
+    const probe = SOURCE.slice(probeStart, probeEnd);
+
+    // #454 stands: the probe reads the file as text and never builds a DOM
+    // from it, so raw JSX can never reach the page through this path.
+    for (const forbidden of ['DOMParser', 'parseFromString', 'replaceChild', 'innerHTML']) {
+      assert.ok(!probe.includes(forbidden), 'the orphan probe must not ' + forbidden + ' JSX source');
+    }
+    assert.match(probe, /\.then\(r => \{ if \(!r\.ok\) throw new Error\('source read failed: ' \+ r\.status\); return r\.text\(\); \}\)/);
+    assert.match(
+      probe,
+      /if \(sourceHasSessionWrapper\(text, sessionId\)\) return;/,
+      'a wrapper still in source is an unmounted component, not an orphan',
+    );
+    assert.match(
+      probe,
+      /const onNoWrapper = \(reason\) => \{[\s\S]*?if \(attempt < COMPLETED_SOURCE_FALLBACK_RETRIES\) \{ retryLater\(\); return; \}\s*discardOrphanedSession\(reason\);/,
+      'the probe must exhaust the shared retry budget before discarding',
+    );
+    assert.match(
+      probe,
+      /onNoWrapper\('variant wrapper missing from source'\)/,
+      'a read without the marker retries on the budget, then discards',
+    );
+    // A read that cannot answer must not strand the session (no empty catch),
+    // and only evidence that the wrapper is gone may discard: a 404 (the file
+    // renamed or deleted) counts, a transient failure does not.
+    assert.doesNotMatch(probe, /\.catch\(\(\) => \{\}\)/, 'the probe must not swallow source read failures');
+    assert.match(
+      probe,
+      /source read failed: 404\$\/\.test\(detail\)\) \{\s*onNoWrapper\('source file missing \(404\)/,
+      'a 404 is evidence the file is gone: retry on the budget, then discard',
+    );
+    assert.match(
+      probe,
+      /const onUnreadable = \(detail\) => \{[\s\S]*?retryLater\(\); return; \}[\s\S]*?showToast\(/,
+      'a transient failure retries on the budget and then keeps the session, telling the user',
+    );
+    assert.doesNotMatch(
+      probe.slice(probe.indexOf('const onUnreadable')),
+      /discardOrphanedSession/,
+      'a transient failure must never discard a session',
+    );
+
+    const matchStart = SOURCE.indexOf('function sourceHasSessionWrapper(');
+    const sourceHasSessionWrapper = new Function(
+      SOURCE.slice(matchStart, probeStart) + '\nreturn sourceHasSessionWrapper;',
+    )();
+    assert.equal(sourceHasSessionWrapper('<div data-impeccable-variants="ab12cd34">', 'ab12cd34'), true);
+    assert.equal(sourceHasSessionWrapper("<div data-impeccable-variants='ab12cd34'>", 'ab12cd34'), true);
+    assert.equal(sourceHasSessionWrapper('{/* impeccable-variants-start ab12cd34 */}', 'ab12cd34'), true);
+    assert.equal(sourceHasSessionWrapper('<div data-impeccable-variants="99887766">', 'ab12cd34'), false);
+    assert.equal(sourceHasSessionWrapper('', 'ab12cd34'), false);
+  });
+
   it('does not source-inject per variant_progress checkpoint (HMR owns mid-generation reconciliation)', () => {
     // Isolate the variant_progress handler body.
     const progressCase = SOURCE.match(/case 'variant_progress':[\s\S]*?break;/);