diff --git a/scripts/documentWatcherSession.test.ts b/scripts/documentWatcherSession.test.ts
new file mode 100644
index 0000000..f7498e1
--- /dev/null
+++ b/scripts/documentWatcherSession.test.ts
@@ -0,0 +1,12 @@
+import assert from 'node:assert/strict';
+import { readFileSync } from 'node:fs';
+import test from 'node:test';
+
+const session = readFileSync('src/lib/sessions/documentSession.svelte.ts', 'utf8');
+
+test('self writes suppress watcher reloads only during their grace period', () => {
+	const handler = session.slice(session.indexOf('function shouldReloadExternalChange'));
+	assert.match(handler, /if \(Date\.now\(\) < until\) return false;/);
+	assert.match(handler, /selfWriteUntilByPath\.delete\(path\);/);
+	assert.match(handler, /return true;/);
+});
diff --git a/src/lib/MarkdownViewer.svelte b/src/lib/MarkdownViewer.svelte
index 98172c6..f34c578 100644
--- a/src/lib/MarkdownViewer.svelte
+++ b/src/lib/MarkdownViewer.svelte
@@ -155,7 +155,6 @@ import { createDocumentSession, type LoadMarkdownOptions } from './sessions/docu
 	const lastContentRefByTab = new Map<string, string>();
 	// Suppress the file-watcher reload that fires when we ourselves write the file.
 	// Maps absolute path -> wall-clock ms after which an event for that path is real again.
-	const selfWriteUntilByPath = new Map<string, number>();
 	const SELF_WRITE_GRACE_MS = 400;
 	const AUTO_SAVE_DEBOUNCE_MS = 1500;
 
@@ -492,8 +491,7 @@ import { createDocumentSession, type LoadMarkdownOptions } from './sessions/docu
 			console.error(message, error);
 			addToast(`${message}: ${String(error)}`, 'error');
 		},
-		markSelfWrite: (path) => selfWriteUntilByPath.set(path, Date.now() + SELF_WRITE_GRACE_MS),
-		clearSelfWrite: (path) => selfWriteUntilByPath.delete(path),
+		selfWriteGraceMs: SELF_WRITE_GRACE_MS,
 	});
 
 	async function discardPersistedWindowState() {
@@ -2588,11 +2586,7 @@ import { createDocumentSession, type LoadMarkdownOptions } from './sessions/docu
 					// Skip events caused by our own auto-save / save invocations,
 					// otherwise the reload would clobber any keystrokes that landed
 					// between fs::write and this listener firing.
-					const until = selfWriteUntilByPath.get(currentFile);
-					if (until !== undefined) {
-						if (Date.now() < until) return;
-						selfWriteUntilByPath.delete(currentFile);
-					}
+					if (!documentSession.shouldReloadExternalChange(currentFile)) return;
 					loadMarkdown(currentFile);
 				}),
 			);
diff --git a/src/lib/sessions/documentSession.svelte.ts b/src/lib/sessions/documentSession.svelte.ts
index fe453ec..b89172b 100644
--- a/src/lib/sessions/documentSession.svelte.ts
+++ b/src/lib/sessions/documentSession.svelte.ts
@@ -25,13 +25,29 @@ type DocumentSessionOptions = {
 	isScrolling: () => boolean;
 	renderRichContent: () => void;
 	onError: (message: string, error: unknown) => void;
-	markSelfWrite: (path: string) => void;
-	clearSelfWrite: (path: string) => void;
+	selfWriteGraceMs: number;
 };
 
 export function createDocumentSession(options: DocumentSessionOptions) {
 	const loadRevisionByTab = new Map<string, number>();
 	const loadingTabs = new Set<string>();
+	const selfWriteUntilByPath = new Map<string, number>();
+
+	function markSelfWrite(path: string) {
+		selfWriteUntilByPath.set(path, Date.now() + options.selfWriteGraceMs);
+	}
+
+	function clearSelfWrite(path: string) {
+		selfWriteUntilByPath.delete(path);
+	}
+
+	function shouldReloadExternalChange(path: string) {
+		const until = selfWriteUntilByPath.get(path);
+		if (until === undefined) return true;
+		if (Date.now() < until) return false;
+		selfWriteUntilByPath.delete(path);
+		return true;
+	}
 
 	function updateLoading(tabId: string, loading: boolean) {
 		if (loading) loadingTabs.add(tabId);
@@ -146,10 +162,10 @@ export function createDocumentSession(options: DocumentSessionOptions) {
 			targetPath = selected;
 		}
 		const snapshot = tab.rawContent;
-		options.markSelfWrite(targetPath);
+		markSelfWrite(targetPath);
 		try {
 			await invoke('save_file_content', { path: targetPath, content: snapshot });
-			options.markSelfWrite(targetPath);
+			markSelfWrite(targetPath);
 			if (tab.path === '') {
 				tabManager.updateTabPath(tab.id, targetPath);
 				options.saveRecentFile(targetPath);
@@ -158,7 +174,7 @@ export function createDocumentSession(options: DocumentSessionOptions) {
 			tab.isDirty = tab.rawContent !== snapshot;
 			return true;
 		} catch (error) {
-			options.clearSelfWrite(targetPath);
+			clearSelfWrite(targetPath);
 			options.onError('Failed to save file', error);
 			return false;
 		}
@@ -176,17 +192,17 @@ export function createDocumentSession(options: DocumentSessionOptions) {
 		});
 		if (!selected) return false;
 		const snapshot = tab.rawContent;
-		options.markSelfWrite(selected);
+		markSelfWrite(selected);
 		try {
 			await invoke('save_file_content', { path: selected, content: snapshot });
-			options.markSelfWrite(selected);
+			markSelfWrite(selected);
 			tabManager.updateTabPath(tab.id, selected);
 			options.saveRecentFile(selected);
 			tab.originalContent = snapshot;
 			tab.isDirty = tab.rawContent !== snapshot;
 			return true;
 		} catch (error) {
-			options.clearSelfWrite(selected);
+			clearSelfWrite(selected);
 			options.onError('Failed to save file as', error);
 			return false;
 		}
@@ -207,5 +223,5 @@ export function createDocumentSession(options: DocumentSessionOptions) {
 		return true;
 	}
 
-	return { loadMarkdown, saveContent, saveContentAs, toggleTaskCheckbox };
+	return { loadMarkdown, saveContent, saveContentAs, toggleTaskCheckbox, shouldReloadExternalChange };
 }