Improve Editor text file workflows

Generalize the Editor storage/session path from Markdown-only to exact-text .md and .txt documents, including open, save, Save As, and rename refresh behavior.

Expose Open in Editor as a visible row action in the File Browser for Editor-owned text files, keep non-Editor surface opens in the overflow menu, and route Desktop text MIME handling through the Editor bridge.

Tests: node --check webui/components/modals/file-browser/file-browser-store.js; python -m py_compile plugins/_office/helpers/document_store.py plugins/_editor/helpers/markdown_sessions.py plugins/_editor/api/editor_session.py plugins/_editor/api/ws_editor.py plugins/_desktop/helpers/desktop_session.py plugins/_desktop/api/desktop_session.py plugins/_office/api/office_session.py plugins/_office/api/ws_office.py; pytest tests/test_office_document_store.py tests/test_file_browser_navigation.py tests/test_office_canvas_setup.py -q

plugins/_desktop/AGENTS.md

@@ -16,6 +16,7 @@
 - Preserve session startup, cleanup, and route protection for desktop access.
 - Keep desktop state injected into prompts accurate and bounded.
 - Do not expose desktop routes without the expected auth protections.
+- Keep Markdown and plain text file open-with handling routed to the Editor surface through the desktop intent bridge; Desktop owns the Xfce launcher/MIME setup, while Editor owns `.md` and `.txt` editing.
 
 ## Work Guidance
 

plugins/_desktop/api/desktop_session.py

@@ -74,10 +74,10 @@ class DesktopSession(ApiHandler):
             return {"ok": False, "error": str(exc)}
 
         ext = str(doc.get("extension") or "").lower()
-        if ext == "md":
+        if ext in document_store.EDITOR_TEXT_EXTENSIONS:
             return {
                 "ok": False,
-                "error": "Markdown documents use the Editor surface.",
+                "error": "Text documents use the Editor surface.",
                 "requires_editor": True,
                 "document": _public_doc(doc),
             }

plugins/_desktop/helpers/desktop_session.py

@@ -23,7 +23,7 @@ from plugins._desktop.helpers import desktop_state
 from plugins._office.helpers import document_store, libreoffice
 
 
-OFFICIAL_EXTENSIONS = {"odt", "ods", "odp", "docx", "xlsx", "pptx", "txt"}
+OFFICIAL_EXTENSIONS = {"odt", "ods", "odp", "docx", "xlsx", "pptx"}
 PLUGIN_NAME = "_desktop"
 SYSTEM_SESSION_ID = "agent-zero-desktop"
 SYSTEM_FILE_ID = "system-desktop"
@@ -78,6 +78,7 @@ DESKTOP_FOLDER_LINKS = (
 URL_INTENT_MAX_ITEMS = 50
 URL_INTENT_MAX_LENGTH = 8192
 URL_HANDLER_DESKTOP_ID = "agent-zero-browser.desktop"
+EDITOR_HANDLER_DESKTOP_ID = "agent-zero-editor.desktop"
 SHUTDOWN_HANDLER_DESKTOP_ID = "agent-zero-shutdown.desktop"
 SHUTDOWN_PANEL_LAUNCHER_ID = SHUTDOWN_HANDLER_DESKTOP_ID
 SHUTDOWN_CONFIRM_SECONDS = 8
@@ -1135,6 +1136,7 @@ class DesktopSessionManager:
         applications_dir.mkdir(parents=True, exist_ok=True)
 
         browser_bridge = _write_url_bridge_script(session)
+        editor_bridge = _write_editor_bridge_script(session)
         shutdown_bridge = _write_shutdown_bridge_script(session)
         helpers_rc = config_dir / "xfce4" / "helpers.rc"
         helpers_rc.parent.mkdir(parents=True, exist_ok=True)
@@ -1153,8 +1155,12 @@ class DesktopSessionManager:
             config_dir / "xfce4" / "helpers" / "agent-zero-browser.desktop",
             browser_bridge,
         )
-        _write_mimeapps_defaults(config_dir / "mimeapps.list", URL_HANDLER_DESKTOP_ID)
-        _write_mimeapps_defaults(data_dir / "applications" / "mimeapps.list", URL_HANDLER_DESKTOP_ID)
+        _write_mimeapps_defaults(config_dir / "mimeapps.list", URL_HANDLER_DESKTOP_ID, EDITOR_HANDLER_DESKTOP_ID)
+        _write_mimeapps_defaults(
+            data_dir / "applications" / "mimeapps.list",
+            URL_HANDLER_DESKTOP_ID,
+            EDITOR_HANDLER_DESKTOP_ID,
+        )
         _write_desktop_launcher(
             applications_dir / URL_HANDLER_DESKTOP_ID,
             name="Agent Zero Browser",
@@ -1165,6 +1171,15 @@ class DesktopSessionManager:
             mime_types=_url_handler_mime_types(),
             no_display=True,
         )
+        _write_desktop_launcher(
+            applications_dir / EDITOR_HANDLER_DESKTOP_ID,
+            name="Agent Zero Editor",
+            exec_line=_desktop_exec(editor_bridge, "%F"),
+            icon="accessories-text-editor",
+            categories="Utility;TextEditor;",
+            try_exec=str(editor_bridge),
+            mime_types=_editor_text_handler_mime_types(),
+        )
         _write_desktop_launcher(
             applications_dir / SHUTDOWN_HANDLER_DESKTOP_ID,
             name="Shutdown Desktop",
@@ -1190,6 +1205,14 @@ class DesktopSessionManager:
             categories="Network;WebBrowser;",
             try_exec=str(browser_bridge),
         )
+        _write_desktop_launcher(
+            desktop_dir / "Editor.desktop",
+            name="Editor",
+            exec_line=_desktop_exec(editor_bridge),
+            icon="accessories-text-editor",
+            categories="Utility;TextEditor;",
+            try_exec=str(editor_bridge),
+        )
         self._trust_desktop_launchers(session, desktop_dir)
 
     def _hide_xpra_desktop_entries(self, applications_dir: Path) -> None:
@@ -1830,6 +1853,10 @@ def _url_bridge_script_path(session: DesktopSession) -> Path:
     return _url_bridge_dir(session) / "open-url"
 
 
+def _editor_bridge_script_path(session: DesktopSession) -> Path:
+    return _url_bridge_dir(session) / "open-editor"
+
+
 def _url_bridge_queue_path(session: DesktopSession) -> Path:
     return _url_bridge_dir(session) / "browser-url-intents.jsonl"
 
@@ -1900,6 +1927,64 @@ if __name__ == "__main__":
     return script
 
 
+def _write_editor_bridge_script(session: DesktopSession) -> Path:
+    bridge_dir = _url_bridge_dir(session)
+    bridge_dir.mkdir(parents=True, exist_ok=True)
+    script = _editor_bridge_script_path(session)
+    queue = _url_bridge_queue_path(session)
+    lock = _url_bridge_lock_path(session)
+    script.write_text(
+        f"""#!/usr/bin/env python3
+import fcntl
+import json
+import os
+import sys
+import time
+from urllib.parse import quote
+
+QUEUE_PATH = {str(queue)!r}
+LOCK_PATH = {str(lock)!r}
+MAX_URL_LENGTH = {URL_INTENT_MAX_LENGTH}
+
+
+def editor_url(path):
+    path = str(path or "").strip()
+    if not path:
+        return "a0-editor://open"
+    return "a0-editor://open?path=" + quote(path[:MAX_URL_LENGTH], safe="/:")
+
+
+def main():
+    urls = [editor_url(arg) for arg in sys.argv[1:] if str(arg or "").strip()]
+    if not urls:
+        urls = [editor_url("")]
+    os.makedirs(os.path.dirname(QUEUE_PATH), exist_ok=True)
+    with open(LOCK_PATH, "a+", encoding="utf-8") as lock_file:
+        fcntl.flock(lock_file, fcntl.LOCK_EX)
+        with open(QUEUE_PATH, "a", encoding="utf-8") as queue_file:
+            for url in urls:
+                queue_file.write(json.dumps({{
+                    "url": url,
+                    "created_at": time.time(),
+                    "source": "desktop-editor",
+                }}, ensure_ascii=True) + "\\n")
+            queue_file.flush()
+            os.fsync(queue_file.fileno())
+        fcntl.flock(lock_file, fcntl.LOCK_UN)
+
+
+if __name__ == "__main__":
+    main()
+""",
+        encoding="utf-8",
+    )
+    try:
+        script.chmod(0o755)
+    except OSError:
+        pass
+    return script
+
+
 def _write_shutdown_bridge_script(session: DesktopSession) -> Path:
     bridge_dir = _url_bridge_dir(session)
     bridge_dir.mkdir(parents=True, exist_ok=True)
@@ -2102,14 +2187,25 @@ def _url_handler_mime_types() -> tuple[str, ...]:
     )
 
 
-def _write_mimeapps_defaults(path: Path, desktop_id: str) -> None:
-    associations = ";".join([desktop_id, ""])
+def _editor_text_handler_mime_types() -> tuple[str, ...]:
+    return (
+        "text/markdown",
+        "text/x-markdown",
+        "text/plain",
+    )
+
+
+def _write_mimeapps_defaults(path: Path, url_desktop_id: str, editor_desktop_id: str) -> None:
+    url_associations = ";".join([url_desktop_id, ""])
+    editor_associations = ";".join([editor_desktop_id, ""])
     lines = [
         "[Default Applications]",
-        *(f"{mime_type}={desktop_id}" for mime_type in _url_handler_mime_types()),
+        *(f"{mime_type}={url_desktop_id}" for mime_type in _url_handler_mime_types()),
+        *(f"{mime_type}={editor_desktop_id}" for mime_type in _editor_text_handler_mime_types()),
         "",
         "[Added Associations]",
-        *(f"{mime_type}={associations}" for mime_type in _url_handler_mime_types()),
+        *(f"{mime_type}={url_associations}" for mime_type in _url_handler_mime_types()),
+        *(f"{mime_type}={editor_associations}" for mime_type in _editor_text_handler_mime_types()),
         "",
     ]
     path.parent.mkdir(parents=True, exist_ok=True)

plugins/_desktop/webui/desktop-store.js

@@ -2239,7 +2239,12 @@ const model = {
   async openDesktopUrlIntent(intent = {}) {
     const url = String(intent?.url || "").trim();
     const handled = await handleUrlIntent({ url, source: "desktop-url" });
-    this.setMessage(handled ? "Opened link in Browser" : "Browser is not available");
+    const isEditorIntent = url.startsWith("a0-editor:");
+    this.setMessage(
+      handled
+        ? (isEditorIntent ? "Opened text in Editor" : "Opened link in Browser")
+        : (isEditorIntent ? "Editor is not available" : "Browser is not available"),
+    );
   },
 
   browserDestinationForDesktopUrl() {

plugins/_editor/AGENTS.md

@@ -2,12 +2,12 @@
 
 ## Purpose
 
-- Own the native Markdown editor surface for canvas and floating modal workflows.
+- Own the native Markdown and plain text editor surface for canvas and floating modal workflows.
 
 ## Ownership
 
 - `api/` owns editor session and WebSocket handlers.
-- `helpers/` owns markdown session and open-file context helpers.
+- `helpers/` owns editor text session and open-file context helpers.
 - `prompts/` owns agent-visible open-file context.
 - `webui/` owns editor panel, preview, store, and main surface.
 - `extensions/` owns editor hook contributions.
@@ -17,6 +17,8 @@
 - Keep editor session state synchronized across API, WebSocket, and WebUI panel behavior.
 - Do not expose unsaved content or local paths beyond intended chat/context surfaces.
 - Keep the floating Editor modal on the shared surface modal chrome so the header remains draggable while existing Focus mode continues to work.
+- Keep Editor Open wired through the File Browser text picker so users can open one or more Markdown or plain text files with an obvious confirmation action.
+- Keep Save As distinct from Rename: Save As writes the current editor text to a chosen `.md` or `.txt` path and retargets the active session without removing the original file.
 
 ## Work Guidance
 

plugins/_editor/api/editor_session.py

@@ -38,13 +38,13 @@ class EditorSession(ApiHandler):
             return closed
         if action == "create":
             fmt = str(input.get("format") or "md").lower().lstrip(".")
-            if fmt != "md":
-                return {"ok": False, "error": "Editor can only create Markdown documents."}
+            if fmt not in document_store.EDITOR_TEXT_EXTENSIONS:
+                return {"ok": False, "error": "Editor can only create Markdown (.md) and text (.txt) documents."}
             try:
                 doc = document_store.create_document(
                     kind="document",
                     title=str(input.get("title") or "Untitled"),
-                    fmt="md",
+                    fmt=fmt,
                     content=str(input.get("content") or ""),
                     path=str(input.get("path") or ""),
                     context_id=context_id,
@@ -72,6 +72,28 @@ class EditorSession(ApiHandler):
             if not session_id:
                 return {"ok": False, "error": "session_id is required."}
             return markdown_sessions.get_manager().save(session_id, text=input.get("text"))
+        if action == "save_as":
+            session_id = str(input.get("session_id") or "").strip()
+            path = str(input.get("path") or "").strip()
+            if not session_id:
+                return {"ok": False, "error": "session_id is required."}
+            if not path:
+                return {"ok": False, "error": "path is required."}
+            try:
+                result = markdown_sessions.get_manager().save_as(session_id, path, text=input.get("text"))
+            except Exception as exc:
+                return {"ok": False, "error": str(exc)}
+            document_store.close_session(session_id=str(input.get("store_session_id") or "").strip())
+            store_session = document_store.create_session(
+                result["document"]["file_id"],
+                user_id=str(input.get("user_id") or "agent-zero-user"),
+                permission="write",
+                origin=self._origin(request),
+            )
+            return {
+                **result,
+                "store_session_id": store_session["session_id"],
+            }
         if action == "renamed":
             return self._renamed(input, context_id)
         if action == "refresh":
@@ -85,7 +107,7 @@ class EditorSession(ApiHandler):
         request: Request,
         context_id: str = "",
     ) -> dict:
-        if str(doc.get("extension") or "").lower() != "md":
+        if str(doc.get("extension") or "").lower() not in document_store.EDITOR_TEXT_EXTENSIONS:
             return {
                 "ok": False,
                 "error": f".{doc.get('extension', '')} documents use the Desktop surface.",

plugins/_editor/api/ws_editor.py

@@ -53,10 +53,17 @@ class WsEditor(WsHandler):
         elif path:
             doc = document_store.register_document(path, context_id=context_id)
         else:
+            fmt = str(data.get("format") or "md").lower().strip().lstrip(".")
+            if fmt not in document_store.EDITOR_TEXT_EXTENSIONS:
+                return WsResult.error(
+                    code="UNSUPPORTED_EDITOR_DOCUMENT",
+                    message=f"Editor can only create Markdown (.md) and text (.txt) documents, not .{fmt}.",
+                    correlation_id=data.get("correlationId"),
+                )
             doc = document_store.create_document(
                 kind="document",
                 title=str(data.get("title") or "Untitled"),
-                fmt="md",
+                fmt=fmt,
                 content=str(data.get("content") or ""),
                 context_id=context_id,
             )

plugins/_editor/helpers/markdown_sessions.py

@@ -31,7 +31,7 @@ class MarkdownSession:
 
 
 class MarkdownSessionManager:
-    """Owns native Editor sessions for Markdown documents."""
+    """Owns native Editor sessions for Markdown and plain text documents."""
 
     def __init__(self) -> None:
         self._sessions: dict[str, MarkdownSession] = {}
@@ -39,8 +39,8 @@ class MarkdownSessionManager:
 
     def open(self, doc: dict[str, Any], sid: str = "", context_id: str = "", refresh: bool = False) -> dict[str, Any]:
         ext = str(doc["extension"]).lower()
-        if ext != "md":
-            raise ValueError(f"Editor is only available for Markdown. Open .{ext} files in the Desktop.")
+        if ext not in document_store.EDITOR_TEXT_EXTENSIONS:
+            raise ValueError(f"Editor is only available for Markdown and text files. Open .{ext} files in the Desktop.")
 
         normalized_context = str(context_id or "")
         if refresh:
@@ -64,6 +64,7 @@ class MarkdownSessionManager:
                 _mark_session_external(session, doc)
             session.path = doc["path"]
             session.title = doc["basename"]
+            session.extension = ext
             session.updated_at = time.time()
             self.activate(session.session_id)
             return self._payload(session, doc)
@@ -103,11 +104,12 @@ class MarkdownSessionManager:
         if conflict is not None:
             return conflict
 
-        updated = document_store.write_markdown(session.file_id, session.text)
+        updated = document_store.write_text_document(session.file_id, session.text)
         session.updated_at = time.time()
         session.dirty = False
         session.path = updated["path"]
         session.title = updated["basename"]
+        session.extension = str(updated.get("extension") or session.extension).lower()
         _set_session_base(session, updated)
         self._refresh_file_sessions(
             updated,
@@ -121,6 +123,32 @@ class MarkdownSessionManager:
             "version": document_store.item_version(updated),
         }
 
+    def save_as(self, session_id: str, path: str, text: str | None = None) -> dict[str, Any]:
+        session = self._require(session_id)
+        if text is not None:
+            session.text = str(text)
+
+        updated = document_store.save_text_document_as(
+            session.file_id,
+            path,
+            session.text,
+            context_id=session.context_id,
+        )
+        old_file_id = session.file_id
+        session.file_id = updated["file_id"]
+        session.updated_at = time.time()
+        session.dirty = False
+        session.path = updated["path"]
+        session.title = updated["basename"]
+        session.extension = str(updated.get("extension") or session.extension).lower()
+        _set_session_base(session, updated)
+        return {
+            "ok": True,
+            "previous_file_id": old_file_id,
+            "document": _public_doc(updated),
+            "version": document_store.item_version(updated),
+        }
+
     def activate(self, session_id: str) -> dict[str, Any]:
         session = self._require(session_id)
         now = time.time()
@@ -145,7 +173,7 @@ class MarkdownSessionManager:
             doc = document_store.get_document(normalized)
         except Exception:
             return {"ok": False, "refreshed": 0, "sessions": []}
-        if str(doc.get("extension") or "").lower() != "md":
+        if str(doc.get("extension") or "").lower() not in document_store.EDITOR_TEXT_EXTENSIONS:
             return {"ok": True, "refreshed": 0, "sessions": []}
 
         refreshed = self._refresh_file_sessions(
@@ -342,6 +370,7 @@ class MarkdownSessionManager:
                 session.text = str(text)
             session.path = doc["path"]
             session.title = doc["basename"]
+            session.extension = str(doc.get("extension") or session.extension).lower()
             if dirty is not None and (can_replace_text or refresh_dirty or not session.dirty):
                 session.dirty = dirty
             if can_replace_text or not session.dirty:

plugins/_editor/helpers/open_files_context.py

@@ -11,7 +11,7 @@ def build_context(context_id: str = "", max_items: int = 20) -> str:
         return ""
 
     lines = [
-        "These Markdown files are open in the Editor for the active Agent Zero context. Content is omitted; use `text_editor` with action `read` before content-sensitive edits.",
+        "These Markdown or plain text files are open in the Editor for the active Agent Zero context. Content is omitted; use `text_editor` with action `read` before content-sensitive edits.",
     ]
     for item in files:
         lines.append(format_open_file_line(item))

plugins/_editor/webui/editor-panel.html

@@ -9,7 +9,7 @@
     <template x-if="$store.editor">
       <div class="editor-panel" x-create="$store.editor.onMount($el, xAttrs($el) || {})" x-destroy="$store.editor.cleanup()">
         <div class="editor-shell" @keydown="$store.editor.handleEditorKeydown($event)">
-          <div class="editor-tabs" x-show="$store.editor.visibleTabs().length > 0" style="display: none;" role="tablist" aria-label="Open Markdown files">
+          <div class="editor-tabs" x-show="$store.editor.visibleTabs().length > 0" style="display: none;" role="tablist" aria-label="Open text files">
             <template x-for="tab in $store.editor.visibleTabs()" :key="tab.tab_id">
               <div
                 class="editor-tab-shell"
@@ -82,6 +82,8 @@
               <button
                 type="button"
                 class="editor-icon-button editor-mode-toggle"
+                x-show="$store.editor.isMarkdown()"
+                style="display: none;"
                 :title="$store.editor.viewModeTitle()"
                 :aria-label="$store.editor.viewModeTitle()"
                 @click="$store.editor.toggleViewMode()"
@@ -89,30 +91,30 @@
                 <span class="material-symbols-outlined" aria-hidden="true" x-text="$store.editor.viewModeIcon()"></span>
               </button>
 
-              <div class="editor-tool-group editor-source-tools" x-show="$store.editor.isMarkdown() && $store.editor.isSourceMode()" style="display: none;">
+              <div class="editor-tool-group editor-source-tools" x-show="$store.editor.isTextDocument() && $store.editor.isSourceMode()" style="display: none;">
                 <button type="button" class="editor-icon-button" title="Undo" aria-label="Undo" :disabled="!$store.editor.canUndo()" @click="$store.editor.undo()">
                   <span class="material-symbols-outlined">undo</span>
                 </button>
                 <button type="button" class="editor-icon-button" title="Redo" aria-label="Redo" :disabled="!$store.editor.canRedo()" @click="$store.editor.redo()">
                   <span class="material-symbols-outlined">redo</span>
                 </button>
-                <button type="button" class="editor-icon-button" title="Bold" aria-label="Bold" @click="$store.editor.format('bold')">
+                <button type="button" class="editor-icon-button" title="Bold" aria-label="Bold" x-show="$store.editor.isMarkdown()" @click="$store.editor.format('bold')">
                   <span class="material-symbols-outlined">format_bold</span>
                 </button>
-                <button type="button" class="editor-icon-button" title="Italic" aria-label="Italic" @click="$store.editor.format('italic')">
+                <button type="button" class="editor-icon-button" title="Italic" aria-label="Italic" x-show="$store.editor.isMarkdown()" @click="$store.editor.format('italic')">
                   <span class="material-symbols-outlined">format_italic</span>
                 </button>
-                <button type="button" class="editor-icon-button" title="List" aria-label="List" @click="$store.editor.format('list')">
+                <button type="button" class="editor-icon-button" title="List" aria-label="List" x-show="$store.editor.isMarkdown()" @click="$store.editor.format('list')">
                   <span class="material-symbols-outlined">format_list_bulleted</span>
                 </button>
-                <button type="button" class="editor-icon-button" title="Numbered list" aria-label="Numbered list" @click="$store.editor.format('numbered')">
+                <button type="button" class="editor-icon-button" title="Numbered list" aria-label="Numbered list" x-show="$store.editor.isMarkdown()" @click="$store.editor.format('numbered')">
                   <span class="material-symbols-outlined">format_list_numbered</span>
                 </button>
-                <button type="button" class="editor-icon-button" title="Table" aria-label="Table" @click="$store.editor.format('table')">
+                <button type="button" class="editor-icon-button" title="Table" aria-label="Table" x-show="$store.editor.isMarkdown()" @click="$store.editor.format('table')">
                   <span class="material-symbols-outlined">table</span>
                 </button>
               </div>
-              <div class="editor-tool-group editor-preview-tools" x-show="$store.editor.isPreviewMode()" style="display: none;">
+              <div class="editor-tool-group editor-preview-tools" x-show="$store.editor.isMarkdown() && $store.editor.isPreviewMode()" style="display: none;">
                 <button type="button" class="editor-icon-button" title="Previous page" aria-label="Previous page" :disabled="$store.editor.previewEditing || $store.editor.activePageIndex <= 0" @click="$store.editor.previousPage()">
                   <span class="material-symbols-outlined">chevron_left</span>
                 </button>
@@ -147,6 +149,17 @@
                 <span class="material-symbols-outlined" :class="{ spinning: $store.editor.saving }" x-text="$store.editor.saving ? 'progress_activity' : 'save'"></span>
               </button>
 
+              <button
+                type="button"
+                class="editor-icon-button editor-save-as-button"
+                title="Save As"
+                aria-label="Save As"
+                :disabled="$store.editor.saving"
+                @click="$store.editor.saveAs()"
+              >
+                <span class="material-symbols-outlined">save_as</span>
+              </button>
+
               <div class="editor-file-actions" x-data="{ open: false }" @click.outside="open = false" @keydown.escape.window="open = false">
                 <button
                   type="button"
@@ -213,7 +226,7 @@
                 <textarea
                   class="editor-source-editor"
                   data-editor-source
-                  aria-label="Markdown source"
+                  aria-label="Text source"
                   x-show="$store.editor.aceUnavailable"
                   x-model="$store.editor.editorText"
                   @input="$store.editor.onSourceInput()"
@@ -224,7 +237,7 @@
               </div>
             </div>
 
-            <div class="editor-preview-shell" x-show="$store.editor.session && $store.editor.isPreviewMode()" style="display: none;">
+            <div class="editor-preview-shell" x-show="$store.editor.session && $store.editor.isMarkdown() && $store.editor.isPreviewMode()" style="display: none;">
               <div class="editor-preview-title">
                 <h1 x-text="$store.editor.pageTitle()"></h1>
               </div>
@@ -261,6 +274,10 @@
                   <span class="material-symbols-outlined" aria-hidden="true">article</span>
                   <span class="editor-button-label">Markdown</span>
                 </button>
+                <button type="button" class="editor-icon-button editor-command-button" @click="$store.editor.runNewMenuAction('text')">
+                  <span class="material-symbols-outlined" aria-hidden="true">description</span>
+                  <span class="editor-button-label">Text</span>
+                </button>
               </div>
             </div>
           </div>

plugins/_editor/webui/editor-store.js

@@ -3,7 +3,9 @@ import { callJsonApi } from "/js/api.js";
 import { getNamespacedClient } from "/js/websocket.js";
 import { store as fileBrowserStore } from "/components/modals/file-browser/file-browser-store.js";
 import {
+  openLatest as openLatestSurface,
   placeSurfaceModalHeaderAction,
+  registerUrlHandler,
   setupFloatingSurfaceModalChrome,
 } from "/js/surfaces.js";
 import {
@@ -24,6 +26,7 @@ const INPUT_PUSH_DELAY_MS = 650;
 const MAX_HISTORY = 80;
 const SOURCE_MODE = "source";
 const PREVIEW_MODE = "preview";
+const EDITOR_TEXT_EXTENSIONS = new Set(["md", "txt"]);
 
 function currentContextId() {
   try {
@@ -51,6 +54,33 @@ function parentPath(path = "") {
   return normalized.slice(0, index);
 }
 
+function textDocumentFilename(path = "", fallback = "Untitled.md") {
+  const name = basename(path || fallback || "Untitled.md");
+  const ext = extensionOf(name);
+  if (EDITOR_TEXT_EXTENSIONS.has(ext)) return name;
+  return `${name.replace(/\.+$/, "") || "Untitled"}.md`;
+}
+
+function textDocumentDefaultExtension(path = "") {
+  const ext = extensionOf(path);
+  return EDITOR_TEXT_EXTENSIONS.has(ext) ? ext : "md";
+}
+
+function editorIntent(url = "") {
+  const raw = String(url || "").trim();
+  if (!raw) return null;
+  try {
+    const parsed = new URL(raw);
+    if (parsed.protocol !== "a0-editor:") return null;
+    if (parsed.hostname === "open") {
+      return { path: parsed.searchParams.get("path") || "" };
+    }
+    return null;
+  } catch {
+    return null;
+  }
+}
+
 function uniqueTabId(session = {}) {
   return String(session.file_id || session.session_id || `${Date.now().toString(36)}-${Math.random().toString(36).slice(2)}`);
 }
@@ -77,7 +107,7 @@ function placeCaretAtEnd(element) {
   selection.addRange(range);
 }
 
-function normalizeMarkdown(doc = {}) {
+function normalizeTextDocument(doc = {}) {
   const path = doc.path || "";
   const extension = String(doc.extension || extensionOf(path)).toLowerCase();
   return {
@@ -90,7 +120,7 @@ function normalizeMarkdown(doc = {}) {
 }
 
 function normalizeSession(payload = {}) {
-  const document = normalizeMarkdown(payload.document || payload);
+  const document = normalizeTextDocument(payload.document || payload);
   return {
     ...payload,
     document,
@@ -301,7 +331,7 @@ const model = {
   },
 
   async setViewMode(mode) {
-    const next = mode === PREVIEW_MODE ? PREVIEW_MODE : SOURCE_MODE;
+    const next = mode === PREVIEW_MODE && this.isMarkdown() ? PREVIEW_MODE : SOURCE_MODE;
     if (this.viewMode === next) return;
     this.applyPreviewEdit({ silent: true });
     this.syncEditorText();
@@ -319,6 +349,7 @@ const model = {
   },
 
   async toggleViewMode() {
+    if (!this.isMarkdown()) return;
     await this.setViewMode(this.isPreviewMode() ? SOURCE_MODE : PREVIEW_MODE);
   },
 
@@ -331,6 +362,7 @@ const model = {
   },
 
   pages() {
+    if (!this.isMarkdown()) return [];
     return buildMarkdownPages(this.editorText, this.tabTitle(this.session || {}));
   },
 
@@ -351,6 +383,7 @@ const model = {
   },
 
   previewHtml() {
+    if (!this.isMarkdown()) return "";
     return renderEditorPreviewMarkdown(this.currentPage().markdown || "", this.editorText);
   },
 
@@ -476,7 +509,7 @@ const model = {
   },
 
   schedulePreviewEnhance() {
-    if (!this.isPreviewMode()) return;
+    if (!this.isMarkdown() || !this.isPreviewMode()) return;
     if (this._previewEnhanceTimer) globalThis.clearTimeout(this._previewEnhanceTimer);
     this._previewEnhanceTimer = globalThis.setTimeout(() => {
       this._previewEnhanceTimer = null;
@@ -669,6 +702,7 @@ const model = {
   },
 
   openSearch() {
+    if (!this.isMarkdown()) return;
     if (!this.isPreviewMode()) {
       this.setViewMode(PREVIEW_MODE);
     }
@@ -832,13 +866,15 @@ const model = {
 
   handleEditorKeydown(event) {
     if ((event.metaKey || event.ctrlKey) && event.key.toLowerCase() === "f") {
+      if (!this.isMarkdown()) return;
       event.preventDefault();
       this.openSearch();
     }
   },
 
   async create(kind = "document", format = "") {
-    const fmt = "md";
+    const requested = String(format || "md").toLowerCase().replace(/^\./, "");
+    const fmt = EDITOR_TEXT_EXTENSIONS.has(requested) ? requested : "md";
     const title = this.defaultTitle(kind, fmt);
     return await this.openSession({
       action: "create",
@@ -866,7 +902,17 @@ const model = {
         // The file browser can still open with the static fallback.
       }
     }
-    await fileBrowserStore.open(workdirPath);
+    await fileBrowserStore.openTextPicker(workdirPath, async ({ selectedFiles = [] } = {}) => {
+      const files = selectedFiles.filter((file) => file?.path);
+      if (!files.length) return false;
+      for (const file of files) {
+        const session = await this.openPath(file.path, { source: "file-browser", refresh: true });
+        if (!session || session.ok === false) {
+          throw new Error(this.error || `Could not open ${file.name || file.path}`);
+        }
+      }
+      return true;
+    });
   },
 
   async openPath(path, options = {}) {
@@ -883,11 +929,11 @@ const model = {
     try {
       const response = await callEditor(payload.action || "open", payload);
       if (response?.ok === false) {
-        this.error = response.error || "Markdown could not be opened.";
+        this.error = response.error || "Text document could not be opened.";
         return null;
       }
       if (response?.requires_desktop) {
-        const document = normalizeMarkdown(response.document || response);
+        const document = normalizeTextDocument(response.document || response);
         this.setMessage(`${documentLabel(document)} uses the Desktop surface.`);
         await this.refresh();
         return response;
@@ -931,6 +977,11 @@ const model = {
     this.activeTabId = tab?.tab_id || "";
     this.editorText = String(tab?.text || "");
     this.dirty = Boolean(tab?.dirty);
+    if (!this.isMarkdown(tab) && this.isPreviewMode()) {
+      this.viewMode = SOURCE_MODE;
+      this.searchOpen = false;
+      this.searchQuery = "";
+    }
     if (this.previewEditing) this.cancelPreviewEdit();
     if (!options.preservePage) {
       this.activePageIndex = 0;
@@ -941,6 +992,7 @@ const model = {
     this.searchIndex = -1;
     this.resetHistory(this.editorText);
     this.setSourceEditorText(this.editorText);
+    this.updateSourceEditorMode();
     if (tab?.session_id) {
       requestEditor("editor_activate", { session_id: tab.session_id }, 2500).catch(() => {});
     }
@@ -994,7 +1046,7 @@ const model = {
     if (!pending) return "";
     const dirtyCount = Number(pending.dirtyCount || 0);
     if (pending.kind === "all") {
-      if (dirtyCount === 0) return "All open Markdown files will be closed.";
+      if (dirtyCount === 0) return "All open text files will be closed.";
       return `${dirtyCount} open ${dirtyCount === 1 ? "file has" : "files have"} unsaved changes.`;
     }
     if (dirtyCount > 0) return "This file has unsaved changes.";
@@ -1069,7 +1121,7 @@ const model = {
         file_id: tab.file_id || "",
       });
     } catch (error) {
-      console.warn("Markdown close skipped", error);
+      console.warn("Editor close skipped", error);
     }
     this.tabs = this.tabs.filter((item) => item.tab_id !== tabId);
     if (this.pendingClose?.tabId === tabId || this.pendingClose?.tabIds?.includes(tabId)) {
@@ -1140,7 +1192,7 @@ const model = {
     const darkMode = globalThis.localStorage?.getItem("darkMode");
     const theme = darkMode !== "false" ? "ace/theme/github_dark" : "ace/theme/github";
     editor.setTheme(theme);
-    editor.session.setMode("ace/mode/markdown");
+    editor.session.setMode(this.sourceEditorMode());
     editor.session.setUseWrapMode(true);
     editor.setOptions({
       fontSize: "13px",
@@ -1159,9 +1211,20 @@ const model = {
     editor.session.on("change", this._sourceEditorChangeHandler);
     this.sourceEditor = editor;
     this.aceUnavailable = false;
+    this.updateSourceEditorMode();
     this.queueRender({ focus: Boolean(this.session), end: false });
   },
 
+  sourceEditorMode(tab = this.session) {
+    return this.isMarkdown(tab) ? "ace/mode/markdown" : "ace/mode/text";
+  },
+
+  updateSourceEditorMode(tab = this.session) {
+    try {
+      this.sourceEditor?.session?.setMode(this.sourceEditorMode(tab));
+    } catch {}
+  },
+
   destroySourceEditor() {
     if (this.sourceEditor?.session && this._sourceEditorChangeHandler) {
       this.sourceEditor.session.off?.("change", this._sourceEditorChangeHandler);
@@ -1199,7 +1262,7 @@ const model = {
   },
 
   async save() {
-    if (!this.session || this.saving || !this.isMarkdown()) return;
+    if (!this.session || this.saving || !this.isTextDocument()) return;
     this.applyPreviewEdit({ silent: true });
     this.syncEditorText();
     this.saving = true;
@@ -1213,7 +1276,7 @@ const model = {
         response = await callEditor("save", payload);
       }
       if (response?.ok === false) throw new Error(response.error || "Save failed.");
-      const document = normalizeMarkdown(response.document || this.session.document || {});
+      const document = normalizeTextDocument(response.document || this.session.document || {});
       const updated = {
         ...this.session,
         text: this.editorText,
@@ -1221,6 +1284,7 @@ const model = {
         document,
         path: document.path || this.session.path,
         file_id: document.file_id || this.session.file_id,
+        extension: document.extension || this.session.extension,
         version: document.version || response.version || this.session.version,
       };
       this.replaceActiveSession(updated);
@@ -1234,8 +1298,73 @@ const model = {
     }
   },
 
+  async saveAs() {
+    if (!this.session || this.saving || !this.isTextDocument()) return;
+    this.applyPreviewEdit({ silent: true });
+    this.syncEditorText();
+
+    let startPath = parentPath(this.session.path || this.session.document?.path || "");
+    if (!startPath || startPath === "/") {
+      try {
+        const home = await callEditor("home");
+        startPath = home?.path || startPath || "/a0/usr/workdir";
+      } catch {
+        startPath = "/a0/usr/workdir";
+      }
+    }
+
+    await fileBrowserStore.openSaveAsPicker(startPath, {
+      filename: textDocumentFilename(this.session.path || this.session.title || "Untitled.md"),
+      defaultExtension: textDocumentDefaultExtension(this.session.path || this.session.title || "Untitled.md"),
+      onConfirm: async ({ path } = {}) => {
+        if (!path) return false;
+        await this.saveAsPath(path);
+        return true;
+      },
+    });
+  },
+
+  async saveAsPath(path) {
+    if (!this.session || this.saving || !this.isTextDocument()) return null;
+    this.saving = true;
+    this.error = "";
+    try {
+      const payload = {
+        session_id: this.session.session_id,
+        store_session_id: this.session.store_session_id || "",
+        path,
+        text: this.editorText,
+      };
+      const response = await callEditor("save_as", payload);
+      if (response?.ok === false) throw new Error(response.error || "Save As failed.");
+      const document = normalizeTextDocument(response.document || this.session.document || {});
+      const updated = {
+        ...this.session,
+        text: this.editorText,
+        dirty: false,
+        document,
+        title: document.title || document.basename || basename(document.path),
+        path: document.path || path,
+        file_id: document.file_id || this.session.file_id,
+        extension: document.extension || this.session.extension,
+        store_session_id: response.store_session_id || this.session.store_session_id,
+        version: document.version || response.version || this.session.version,
+      };
+      this.replaceActiveSession(updated);
+      this.dirty = false;
+      this.setMessage("Saved As");
+      await this.refresh();
+      return updated;
+    } catch (error) {
+      this.error = error instanceof Error ? error.message : String(error);
+      throw error;
+    } finally {
+      this.saving = false;
+    }
+  },
+
   async saveTab(tab) {
-    if (!tab || this.saving || !this.isMarkdown(tab)) return false;
+    if (!tab || this.saving || !this.isTextDocument(tab)) return false;
     if (this.isActiveTab(tab)) {
       this.applyPreviewEdit({ silent: true });
       this.syncEditorText();
@@ -1254,7 +1383,7 @@ const model = {
         response = await callEditor("save", payload);
       }
       if (response?.ok === false) throw new Error(response.error || "Save failed.");
-      const document = normalizeMarkdown(response.document || tab.document || {});
+      const document = normalizeTextDocument(response.document || tab.document || {});
       const updated = {
         ...tab,
         text: payload.text,
@@ -1262,6 +1391,7 @@ const model = {
         document,
         path: document.path || tab.path,
         file_id: document.file_id || tab.file_id,
+        extension: document.extension || tab.extension,
         version: document.version || response.version || tab.version,
       };
       this.replaceSession(tab, updated);
@@ -1310,7 +1440,7 @@ const model = {
             file_id: session.file_id || "",
             path: renamedPath,
           };
-          if (this.isMarkdown(session)) {
+          if (this.isTextDocument(session)) {
             this.syncEditorText();
             payload.text = this.session?.tab_id === session.tab_id ? this.editorText : session.text || "";
           }
@@ -1330,7 +1460,7 @@ const model = {
     });
     if (response?.ok === false) throw new Error(response.error || "Rename failed.");
 
-    const document = normalizeMarkdown(response.document || session.document || {});
+    const document = normalizeTextDocument(response.document || session.document || {});
     const updated = {
       ...session,
       document,
@@ -1355,7 +1485,11 @@ const model = {
 
   replaceSession(previous, next) {
     const wasActive = this.activeTabId === (previous?.tab_id || next.tab_id);
-    if (wasActive) this.session = next;
+    if (wasActive) {
+      this.session = next;
+      if (!this.isMarkdown(next) && this.isPreviewMode()) this.viewMode = SOURCE_MODE;
+      this.updateSourceEditorMode(next);
+    }
     const index = this.tabs.findIndex((tab) => tab.tab_id === (previous?.tab_id || next.tab_id));
     if (index >= 0) this.tabs.splice(index, 1, next);
   },
@@ -1447,7 +1581,7 @@ const model = {
   },
 
   scheduleInputPush() {
-    if (!this.session?.session_id || !this.isMarkdown()) return;
+    if (!this.session?.session_id || !this.isTextDocument()) return;
     if (this._inputTimer) globalThis.clearTimeout(this._inputTimer);
     this._inputTimer = globalThis.setTimeout(() => {
       this._inputTimer = null;
@@ -1456,7 +1590,7 @@ const model = {
   },
 
   flushInput() {
-    if (!this.session?.session_id || !this.isMarkdown()) return;
+    if (!this.session?.session_id || !this.isTextDocument()) return;
     if (this.previewEditing) return;
     this.syncEditorText();
     requestEditor("editor_input", {
@@ -1525,7 +1659,7 @@ const model = {
   },
 
   focusEditor(options = {}) {
-    if (!this.session || !this.isMarkdown()) return false;
+    if (!this.session || !this.isTextDocument()) return false;
     if (this.sourceEditor && this.isSourceMode()) {
       this.sourceEditor.focus();
       if (options.end !== false) {
@@ -1549,8 +1683,13 @@ const model = {
     return ext === "md";
   },
 
+  isTextDocument(tab = this.session) {
+    const ext = String(tab?.extension || tab?.document?.extension || "").toLowerCase();
+    return EDITOR_TEXT_EXTENSIONS.has(ext);
+  },
+
   hasActiveFile(tab = this.session) {
-    return Boolean(tab && this.isMarkdown(tab));
+    return Boolean(tab && this.isTextDocument(tab));
   },
 
   visibleTabs() {
@@ -1560,7 +1699,8 @@ const model = {
   defaultTitle(kind, fmt) {
     const date = new Date().toISOString().slice(0, 10);
     if (fmt === "md") return `Markdown ${date}`;
-    return `Markdown ${date}`;
+    if (fmt === "txt") return `Text ${date}`;
+    return `Text ${date}`;
   },
 
   tabTitle(tab = {}) {
@@ -1578,6 +1718,7 @@ const model = {
     tab = tab || {};
     const ext = String(tab.extension || tab.document?.extension || "").toLowerCase();
     if (ext === "md") return "article";
+    if (ext === "txt") return "description";
     return "draft";
   },
 
@@ -1585,6 +1726,7 @@ const model = {
     const normalized = String(action || "").trim().toLowerCase();
     if (normalized === "open") return await this.openFileBrowser();
     if (normalized === "markdown") return await this.create("document", "md");
+    if (normalized === "text") return await this.create("document", "txt");
     return null;
   },
 
@@ -1608,6 +1750,10 @@ const model = {
           <span class="material-symbols-outlined" aria-hidden="true">article</span>
           <span>Markdown</span>
         </button>
+        <button type="button" class="editor-new-menu-item" role="menuitem" data-editor-new-action="text">
+          <span class="material-symbols-outlined" aria-hidden="true">description</span>
+          <span>Text</span>
+        </button>
       </div>
     `;
 
@@ -1678,6 +1824,19 @@ const model = {
       inner.classList.remove("editor-modal", "is-focus-mode");
     };
   },
+
+  async handleEditorUrlIntent(intent = {}) {
+    const editor = editorIntent(intent?.url || "");
+    if (!editor) return false;
+    await openLatestSurface("editor", {
+      path: editor.path,
+      refresh: true,
+      source: intent?.source || "desktop-open",
+    });
+    return true;
+  },
 };
 
 export const store = createStore("editor", model);
+
+registerUrlHandler((intent) => model.handleEditorUrlIntent(intent));

plugins/_office/AGENTS.md

@@ -16,6 +16,7 @@
 - Preserve document storage integrity and live session synchronization.
 - Keep LibreOffice operations bounded to intended workspaces and artifact paths.
 - Do not expose document contents or temporary files beyond intended UI/tool flows.
+- Editor text Save As storage helpers must preserve exact `.md` or `.txt` text and create a new registered document without mutating or deleting the source document.
 
 ## Work Guidance
 

plugins/_office/api/office_session.py

@@ -63,10 +63,10 @@ class OfficeSession(ApiHandler):
 
     async def _open_document(self, doc: dict, input: dict, request: Request) -> dict:
         mode = "edit" if str(input.get("mode") or "edit").lower() == "edit" else "view"
-        if str(doc.get("extension") or "").lower() == "md":
+        if str(doc.get("extension") or "").lower() in document_store.EDITOR_TEXT_EXTENSIONS:
             return {
                 "ok": False,
-                "error": "Markdown documents use the Editor surface.",
+                "error": "Text documents use the Editor surface.",
                 "document": _public_doc(doc),
             }
         if str(doc.get("extension") or "").lower() in desktop_session.OFFICIAL_EXTENSIONS:
@@ -116,7 +116,7 @@ class OfficeSession(ApiHandler):
         return {"ok": False, "error": f".{doc.get('extension', '')} documents are not supported by LibreOffice."}
 
     def _save(self, input: dict) -> dict:
-        return {"ok": False, "error": "Markdown saves use /plugins/_editor/editor_session."}
+        return {"ok": False, "error": "Text document saves use /plugins/_editor/editor_session."}
 
     def _renamed(self, input: dict, context_id: str = "") -> dict:
         file_id = str(input.get("file_id") or "").strip()

plugins/_office/api/ws_office.py

@@ -22,7 +22,7 @@ class WsOffice(WsHandler):
             if event in {"office_input", "office_save", "office_close"}:
                 return {
                     "ok": False,
-                    "error": "Office WebSocket editing is not available for Markdown; use the Editor surface.",
+                    "error": "Office WebSocket editing is not available for text documents; use the Editor surface.",
                 }
         except FileNotFoundError as exc:
             return WsResult.error(code="OFFICE_SESSION_NOT_FOUND", message=str(exc), correlation_id=data.get("correlationId"))
@@ -59,10 +59,10 @@ class WsOffice(WsHandler):
                 context_id=context_id,
             )
         ext = str(doc.get("extension") or "").lower()
-        if ext == "md":
+        if ext in document_store.EDITOR_TEXT_EXTENSIONS:
             return WsResult.error(
                 code="UNSUPPORTED_OFFICE_DOCUMENT",
-                message="Markdown documents use the Editor surface.",
+                message="Text documents use the Editor surface.",
                 correlation_id=data.get("correlationId"),
             )
         if ext in desktop_session.OFFICIAL_EXTENSIONS:

plugins/_office/helpers/document_store.py

@@ -23,8 +23,8 @@ from plugins._office.helpers import pptx_writer
 PLUGIN_NAME = "_office"
 OPEN_DOCUMENT_EXTENSIONS = {"odt", "ods", "odp"}
 OOXML_EXTENSIONS = {"docx", "xlsx", "pptx"}
-DESKTOP_TEXT_EXTENSIONS = {"txt"}
-SUPPORTED_EXTENSIONS = {"md", *OPEN_DOCUMENT_EXTENSIONS, *OOXML_EXTENSIONS, *DESKTOP_TEXT_EXTENSIONS}
+EDITOR_TEXT_EXTENSIONS = {"md", "txt"}
+SUPPORTED_EXTENSIONS = {*EDITOR_TEXT_EXTENSIONS, *OPEN_DOCUMENT_EXTENSIONS, *OOXML_EXTENSIONS}
 DEFAULT_TTL_SECONDS = 8 * 60 * 60
 MAX_SAVE_BYTES = 512 * 1024 * 1024
 ODF_OFFICE_NS = "urn:oasis:names:tc:opendocument:xmlns:office:1.0"
@@ -336,8 +336,8 @@ def rename_document(
     ext = normalize_extension(resolved.suffix.lstrip("."))
     data = None
     if content is not None:
-        if ext != "md":
-            raise ValueError("Inline content can only be provided for Markdown documents.")
+        if ext not in EDITOR_TEXT_EXTENSIONS:
+            raise ValueError("Inline content can only be provided for Editor text documents.")
         data = str(content or "").encode("utf-8")
         if len(data) > MAX_SAVE_BYTES:
             raise OverflowError("Document save exceeds maximum size")
@@ -495,13 +495,91 @@ def close_session(session_id: str = "", file_id: str = "") -> int:
 def read_text_for_editor(doc: dict[str, Any]) -> str:
     path = Path(doc["path"])
     ext = str(doc["extension"]).lower()
-    if ext == "md":
+    if ext in EDITOR_TEXT_EXTENSIONS:
         return path.read_text(encoding="utf-8", errors="replace")
     raise ValueError(f"Text editing is not available for .{ext}.")
 
 
+def write_text_document(file_id: str, content: str) -> dict[str, Any]:
+    doc = get_document(file_id)
+    ext = str(doc.get("extension") or "").lower()
+    if ext not in EDITOR_TEXT_EXTENSIONS:
+        raise ValueError(f"Editor text saves are not available for .{ext}.")
+    return replace_document_bytes(file_id, str(content or "").encode("utf-8"), actor=f"editor:{ext}")
+
+
 def write_markdown(file_id: str, content: str) -> dict[str, Any]:
-    return replace_document_bytes(file_id, str(content or "").encode("utf-8"), actor="editor:markdown")
+    return write_text_document(file_id, content)
+
+
+def save_text_document_as(
+    file_id: str,
+    path: str | Path,
+    content: str,
+    context_id: str = "",
+) -> dict[str, Any]:
+    target = normalize_path(path, context_id=context_id)
+    ext = normalize_extension(target.suffix.lstrip("."))
+    if ext not in EDITOR_TEXT_EXTENSIONS:
+        raise ValueError("Editor Save As only supports Markdown (.md) and text (.txt) files.")
+    if target.exists():
+        raise FileExistsError(f"Target already exists: {display_path(target)}")
+
+    data = str(content or "").encode("utf-8")
+    if len(data) > MAX_SAVE_BYTES:
+        raise OverflowError("Document save exceeds maximum size")
+
+    with connect() as conn:
+        source = get_document(file_id, conn=conn)
+        source_ext = str(source.get("extension") or "").lower()
+        if source_ext not in EDITOR_TEXT_EXTENSIONS:
+            raise ValueError(f"Editor Save As is not available for .{source_ext}.")
+        changed_at = now()
+        target.parent.mkdir(parents=True, exist_ok=True)
+        _write_atomic(target, data)
+        digest = sha256_bytes(data)
+        stat = target.stat()
+        new_file_id = uuid.uuid4().hex
+        conn.execute(
+            """
+            INSERT INTO documents
+            (file_id, path, basename, extension, owner_id, size, version, sha256, last_modified, created_at, updated_at)
+            VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+            """,
+            (
+                new_file_id,
+                str(target),
+                target.name,
+                ext,
+                str(source.get("owner_id") or "a0"),
+                stat.st_size,
+                1,
+                digest,
+                now_iso(),
+                changed_at,
+                changed_at,
+            ),
+        )
+        _record_version(conn, new_file_id, target, "1", data)
+        conn.execute(
+            "INSERT INTO events (file_id, event_type, payload, created_at) VALUES (?, ?, ?, ?)",
+            (
+                file_id,
+                "saved_as",
+                json.dumps({"from": display_path(source["path"]), "to": display_path(target)}),
+                changed_at,
+            ),
+        )
+        conn.execute(
+            "INSERT INTO events (file_id, event_type, payload, created_at) VALUES (?, ?, ?, ?)",
+            (
+                new_file_id,
+                "created_from_save_as",
+                json.dumps({"from": display_path(source["path"])}),
+                changed_at,
+            ),
+        )
+        return get_document(new_file_id, conn=conn)
 
 
 def replace_document_bytes(
@@ -623,7 +701,7 @@ def create_document(
 
 def _unique_document_path(title: str, ext: str, context_id: str = "") -> Path:
     base = safe_document_stem(title, ext, "Document")
-    root = document_home(context_id) if ext == "md" else document_binary_home(context_id)
+    root = document_home(context_id) if ext in EDITOR_TEXT_EXTENSIONS else document_binary_home(context_id)
     candidate = root / f"{base}.{ext}"
     index = 2
     while candidate.exists():