diff --git a/packages/@d-zero/google-sheets/src/sheets/sheet.spec.ts b/packages/@d-zero/google-sheets/src/sheets/sheet.spec.ts
index 62125ed3..39ed6bd1 100644
--- a/packages/@d-zero/google-sheets/src/sheets/sheet.spec.ts
+++ b/packages/@d-zero/google-sheets/src/sheets/sheet.spec.ts
@@ -268,6 +268,15 @@ describe('appendRow / flush', () => {
 		expect(sheet.sentCount).toBe(3);
 	});
 
+	test('pendingCount returns to 0 after [Symbol.asyncDispose] flushes the buffer', async () => {
+		const { parent } = createRecordingParent();
+		const sheet = new Sheet(mockSheet as never, parent as never);
+
+		await sheet.appendRow(...Array.from({ length: 3 }, () => eagerRow()));
+		await sheet[Symbol.asyncDispose]();
+		expect(sheet.pendingCount).toBe(0);
+	});
+
 	test('suspends auto-flush as soon as a lazy row enters the buffer', async () => {
 		const { parent, updateCellsRows } = createRecordingParent();
 		const sheet = new Sheet(mockSheet as never, parent as never);
@@ -328,6 +337,47 @@ describe('appendRow / flush', () => {
 		expect(sheet.sentCount).toBe(0);
 	});
 
+	test('pendingCount reflects buffered rows below the auto-flush threshold', async () => {
+		const { parent } = createRecordingParent();
+		const sheet = new Sheet(mockSheet as never, parent as never);
+
+		expect(sheet.pendingCount).toBe(0);
+
+		await sheet.appendRow(...Array.from({ length: 2499 }, () => eagerRow()));
+		expect(sheet.pendingCount).toBe(2499);
+	});
+
+	test('pendingCount drops to the chunk remainder once auto-flush fires', async () => {
+		const { parent } = createRecordingParent();
+		const sheet = new Sheet(mockSheet as never, parent as never);
+
+		// 6000 rows -> two auto-flushed chunks of 2500, 1000 left buffered.
+		await sheet.appendRow(...Array.from({ length: 6000 }, () => eagerRow()));
+		expect(sheet.pendingCount).toBe(1000);
+	});
+
+	test('pendingCount returns to 0 after flush() drains the buffer', async () => {
+		const { parent } = createRecordingParent();
+		const sheet = new Sheet(mockSheet as never, parent as never);
+
+		await sheet.appendRow(...Array.from({ length: 6000 }, () => eagerRow()));
+		await sheet.flush();
+		expect(sheet.pendingCount).toBe(0);
+	});
+
+	test('pendingCount includes rows held past SEND_CHUNK_SIZE while a lazy row suspends auto-flush', async () => {
+		const { parent } = createRecordingParent();
+		const sheet = new Sheet(mockSheet as never, parent as never);
+
+		// 2499 eager (below threshold, no flush yet) + 1 lazy (latches
+		// auto-flush) + 5000 more eager = 7500 held in the buffer instead of
+		// auto-flushing at the 2500 boundary.
+		await sheet.appendRow(...Array.from({ length: 2499 }, () => eagerRow()));
+		await sheet.appendRow(lazyRow());
+		await sheet.appendRow(...Array.from({ length: 5000 }, () => eagerRow()));
+		expect(sheet.pendingCount).toBe(7500);
+	});
+
 	test('detects a lazy cell at any column position, not just the first cell of the row', async () => {
 		// containsLazyCell() iterates every cell of the row. A defensive
 		// "optimization" that only checks row[0] would slip past unit tests
diff --git a/packages/@d-zero/google-sheets/src/sheets/sheet.ts b/packages/@d-zero/google-sheets/src/sheets/sheet.ts
index 3bf40800..067fa448 100644
--- a/packages/@d-zero/google-sheets/src/sheets/sheet.ts
+++ b/packages/@d-zero/google-sheets/src/sheets/sheet.ts
@@ -100,6 +100,28 @@ export class Sheet {
 		return props;
 	}
 
+	/**
+	 * バッファに溜まっているが未送信の行数。`SEND_CHUNK_SIZE` 未満で
+	 * 自動 flush の閾値に達していない行、または遅延セルによって自動
+	 * flush が保留されている行を指す。
+	 *
+	 * `flush()` 呼び出し前に「これから何行分のネットワーク往復が
+	 * 発生するか」を呼び出し元が表示する用途（例: 進捗表示の
+	 * "flushing N rows..." メッセージ）。`onProgress` は chunk の
+	 * `batchUpdate` 完了後にしか呼ばれないため、送信開始前の見積もりは
+	 * この getter でのみ得られる。
+	 * @example
+	 * ```ts
+	 * if (sheet.pendingCount > 0) {
+	 *   showProgress(`flushing ${sheet.pendingCount} rows...`);
+	 * }
+	 * await sheet.flush();
+	 * ```
+	 */
+	get pendingCount() {
+		return this.#pendingRows.length;
+	}
+
 	/**
 	 * `appendRow()` / `flush()` を通じてこれまでに送信した累計行数。
 	 * 進捗表示用途。`setHeaders()` の送信分は含まない。