fix: AsyncDrain double-allocation bug and history test singleton isolation

packages/coding-agent/src/session/history-storage.ts

@@ -28,8 +28,7 @@ class AsyncDrain<T> {
 	push(value: T, hnd: (values: T[]) => Promise<void> | void): Promise<void> {
 		let queue = this.#queue;
 		if (!queue) {
-			queue = [];
-			this.#queue = [];
+			this.#queue = queue = [];
 			this.#promise = new Promise((resolve, reject) => {
 				const exec = () => {
 					try {
@@ -128,6 +127,11 @@ CREATE TRIGGER IF NOT EXISTS history_ai AFTER INSERT ON history BEGIN
 		return HistoryStorage.#instance;
 	}
 
+	/** @internal Reset the singleton — test-only. */
+	static resetInstance(): void {
+		HistoryStorage.#instance = undefined;
+	}
+
 	#insertBatch(rows: Array<Pick<HistoryEntry, "prompt" | "cwd">>): void {
 		this.#db.transaction((rows: Array<Pick<HistoryEntry, "prompt" | "cwd">>) => {
 			for (const row of rows) {

packages/coding-agent/test/history-storage-sqlite-compat.test.ts

@@ -1,5 +1,5 @@
 import { Database } from "bun:sqlite";
-import { afterEach, expect, it } from "bun:test";
+import { afterEach, beforeEach, expect, it } from "bun:test";
 import * as fs from "node:fs/promises";
 import * as os from "node:os";
 import * as path from "node:path";
@@ -21,7 +21,12 @@ function readTableSql(dbPath: string, tableName: string): string | null {
 
 let tempDir = "";
 
+beforeEach(() => {
+	HistoryStorage.resetInstance();
+});
+
 afterEach(async () => {
+	HistoryStorage.resetInstance();
 	if (tempDir) {
 		await fs.rm(tempDir, { recursive: true, force: true });
 		tempDir = "";