fix(streaming): re-resolve the leaf per delta so deltas stay in the right file

src/main.ts

@@ -252,9 +252,14 @@ export default class BeaverPlugin extends Plugin {
     const filename = this.gatewayFilename(file);
     if (!filename) return;
 
-    const { editor, view } = this.findEditorFor(file);
-    const content = editor
-      ? editor.getValue()
+    // Snapshot the buffer if the file is open, otherwise read disk. We
+    // don't keep the editor: an ``Editor`` belongs to a leaf, not a
+    // file, so if the user opens another note in the same tab mid-
+    // stream the old handle now points at the wrong document. Every
+    // delta and the final write re-resolve the leaf by ``file.path``.
+    const initialEditor = this.findEditorFor(file);
+    const content = initialEditor
+      ? initialEditor.getValue()
       : await this.app.vault.read(file);
 
     const notice = new Notice(`Beaver: sending to ${agent}…`, 0);
@@ -269,7 +274,10 @@ export default class BeaverPlugin extends Plugin {
             // write the partial to disk. The gateway also skips its own
             // intermediate file writes on this endpoint, so the local
             // file (and Obsidian Sync's copy) only sees the final state
-            // once.
+            // once. Re-resolved per delta: if ``file`` is no longer
+            // open anywhere, the delta is dropped and the final
+            // ``vault.modify`` catches the buffer up.
+            const editor = this.findEditorFor(file);
             if (editor) spliceIntoEditor(editor, newContent);
           },
           onDone: (resp) => {
@@ -305,7 +313,7 @@ export default class BeaverPlugin extends Plugin {
     }
 
     if (typeof resp.new_content === "string") {
-      await this.writeBack(file, editor, view, resp.new_content);
+      await this.writeBack(file, resp.new_content);
     }
     new Notice(`Beaver: ${agent} replied`);
   }
@@ -324,29 +332,22 @@ export default class BeaverPlugin extends Plugin {
     return null;
   }
 
-  private findEditorFor(file: TFile): {
-    editor: Editor | null;
-    view: MarkdownView | null;
-  } {
+  private findEditorFor(file: TFile): Editor | null {
     // Walk open markdown views — we want the editor instance that owns
-    // ``file`` so we can use setValue (keeps the buffer's edit history
-    // intact) instead of falling back to vault.modify.
+    // ``file`` *right now* so we can splice (keeps the buffer's edit
+    // history intact) instead of falling back to vault.modify. Never
+    // cached by callers: ``view.file`` changes when the user navigates
+    // within the same leaf, and is ``null`` between switches.
     const leaves = this.app.workspace.getLeavesOfType("markdown");
     for (const leaf of leaves) {
       const view = leaf.view as MarkdownView;
-      if (view?.file?.path === file.path) {
-        return { editor: view.editor, view };
-      }
+      if (view?.file?.path === file.path) return view.editor;
     }
-    return { editor: null, view: null };
+    return null;
   }
 
-  private async writeBack(
-    file: TFile,
-    editor: Editor | null,
-    _view: MarkdownView | null,
-    newContent: string,
-  ): Promise<void> {
+  private async writeBack(file: TFile, newContent: string): Promise<void> {
+    const editor = this.findEditorFor(file);
     if (editor) {
       // Reuse the splice path so the final write (frontmatter refresh
       // at the top + USER_SCAFFOLD appended at the bottom) preserves
@@ -354,6 +355,9 @@ export default class BeaverPlugin extends Plugin {
       spliceIntoEditor(editor, newContent);
       return;
     }
+    // File not open (anymore): write to disk. Obsidian refreshes any
+    // buffer that opens it later, and a leaf that shows it in another
+    // pane gets the update through the vault event.
     await this.app.vault.modify(file, newContent);
   }