diff --git a/static/js/documentLibrary.js b/static/js/documentLibrary.js
index 6d86a8e..aabf7a9 100644
--- a/static/js/documentLibrary.js
+++ b/static/js/documentLibrary.js
@@ -652,9 +652,10 @@ let _libraryArchivedView = false;   // Documents tab showing archived docs?
     if (doc.session_id) {
       openItem.addEventListener('click', (e) => { e.stopPropagation(); hideCardDropdown(); libraryOpenInSession(doc); });
     } else {
-      openItem.disabled = true;
-      openItem.style.opacity = '0.35';
-      openItem.title = 'Not linked to a session';
+      // Orphaned doc (closed / session detached) is still openable in the editor
+      // by id — libraryOpenDocument handles the no-session case (#1602).
+      openItem.title = 'Open in the editor';
+      openItem.addEventListener('click', (e) => { e.stopPropagation(); hideCardDropdown(); libraryOpenDocument(doc); });
     }
     dropdown.appendChild(openItem);
 
@@ -772,10 +773,10 @@ let _libraryArchivedView = false;   // Documents tab showing archived docs?
       openBtn.title = 'Open in original session';
       openBtn.addEventListener('click', (e) => { e.stopPropagation(); libraryOpenInSession(doc); });
     } else {
-      openBtn.disabled = true;
-      openBtn.style.opacity = '0.35';
-      openBtn.style.cursor = 'not-allowed';
-      openBtn.title = 'This document is not linked to a session';
+      // Orphaned doc (closed / session detached) is still openable in the editor
+      // by id — libraryOpenDocument handles the no-session case (#1602).
+      openBtn.title = 'Open in the editor';
+      openBtn.addEventListener('click', (e) => { e.stopPropagation(); libraryOpenDocument(doc); });
     }
 
     const cloneBtn = document.createElement('button');
diff --git a/tests/test_doc_library_open_orphaned.py b/tests/test_doc_library_open_orphaned.py
new file mode 100644
index 0000000..b164cd4
--- /dev/null
+++ b/tests/test_doc_library_open_orphaned.py
@@ -0,0 +1,47 @@
+"""Regression for issue #1602 — after closing an AI-written document, its "Open"
+button in the Documents library is grayed out, so the user can't reopen it.
+
+Root cause: closing/detaching a document nulls its session_id (the detach
+behaviour from #1238), and both Open controls in static/js/documentLibrary.js
+(the card's expanded Open button AND the card dropdown's Open item) gated on
+`doc.session_id` — wiring `libraryOpenInSession` (which early-returns when there's
+no session) and DISABLING the control otherwise. But the module already has
+`libraryOpenDocument`, which explicitly handles the orphaned case ("just open in
+editor without switching session"). The fix routes the no-session path there
+instead of disabling.
+
+documentLibrary.js pulls in browser-only modules so it can't run under node; this
+guards the wiring at the source level (red→green via git-stash).
+"""
+
+import re
+from pathlib import Path
+
+SRC = Path(__file__).resolve().parent.parent / "static/js/documentLibrary.js"
+
+
+def _src() -> str:
+    return SRC.read_text(encoding="utf-8")
+
+
+def test_orphaned_doc_open_controls_are_not_disabled():
+    text = _src()
+    # Neither Open control may hard-disable itself for a session-less doc anymore.
+    assert "openItem.disabled = true" not in text, "dropdown Open must not be disabled for orphaned docs (#1602)"
+    assert "openBtn.disabled = true" not in text, "card Open button must not be disabled for orphaned docs (#1602)"
+    # The old 'not linked to a session' dead-end titles are gone.
+    assert "not linked to a session" not in text.lower()
+
+
+def test_orphaned_doc_open_routes_to_editor_load():
+    """Both Open controls' no-session branch must call libraryOpenDocument, the
+    function that opens an orphaned doc directly in the editor by id."""
+    text = _src()
+    # definition + two wirings (dropdown item + card button)
+    assert text.count("libraryOpenDocument(doc)") >= 3, \
+        "both Open controls must route the no-session case to libraryOpenDocument"
+    # libraryOpenDocument genuinely handles the orphaned case.
+    body = text[text.index("async function libraryOpenDocument(doc)"):]
+    body = body[: body.index("async function libraryOpenInSession")]
+    assert "if (!doc.session_id)" in body and "_loadDocument(doc.id)" in body, \
+        "libraryOpenDocument must open a session-less doc by id"