diff --git a/apps/server/src/serviceLauncher.test.ts b/apps/server/src/serviceLauncher.test.ts
index 45c472af1fc4..036d19f71ddf 100644
--- a/apps/server/src/serviceLauncher.test.ts
+++ b/apps/server/src/serviceLauncher.test.ts
@@ -3,8 +3,18 @@ import { assert, it } from "@effect/vitest";
 import * as Effect from "effect/Effect";
 import * as FileSystem from "effect/FileSystem";
 import * as Path from "effect/Path";
+import * as NodeFS from "node:fs";
+import * as NodeFSP from "node:fs/promises";
+import * as NodeOS from "node:os";
+import * as NodePath from "node:path";
+import { DatabaseSync } from "node:sqlite";
 
-import { Launcher, readServiceState, writeServiceState } from "./serviceLauncher.ts";
+import {
+  Launcher,
+  readServiceState,
+  vacuumDatabaseInto,
+  writeServiceState,
+} from "./serviceLauncher.ts";
 import {
   compareExactServiceVersions,
   decodeServiceState,
@@ -32,6 +42,58 @@ it("orders exact semantic versions without treating build metadata as precedence
   assert.equal(compareExactServiceVersions("2.0.0+one", "2.0.0+two"), 0);
 });
 
+function seedSqlite(databasePath: string): void {
+  const seed = new DatabaseSync(databasePath);
+  try {
+    seed.exec(
+      "CREATE TABLE kv (k TEXT PRIMARY KEY, v TEXT NOT NULL); INSERT INTO kv VALUES ('phase', 'before');",
+    );
+  } finally {
+    seed.close();
+  }
+}
+
+it("snapshots sqlite with VACUUM INTO and no wal sidecar", async () => {
+  const dir = await NodeFSP.mkdtemp(NodePath.join(NodeOS.tmpdir(), "t3-vacuum-backup-"));
+  try {
+    const source = NodePath.join(dir, "state.sqlite");
+    const destination = NodePath.join(dir, "backup");
+    seedSqlite(source);
+    vacuumDatabaseInto(source, destination);
+
+    const restored = new DatabaseSync(destination, { readOnly: true });
+    try {
+      const row = restored.prepare("SELECT v AS v FROM kv WHERE k = 'phase'").get() as {
+        v: string;
+      };
+      assert.equal(row.v, "before");
+    } finally {
+      restored.close();
+    }
+    assert.isFalse(NodeFS.existsSync(`${destination}-wal`));
+    assert.isFalse(NodeFS.existsSync(`${destination}-shm`));
+  } finally {
+    await NodeFSP.rm(dir, { recursive: true, force: true });
+  }
+});
+
+it.skipIf(NodePath.sep === "\\")(
+  "keeps a literal backslash in a POSIX vacuum destination",
+  async () => {
+    const dir = await NodeFSP.mkdtemp(NodePath.join(NodeOS.tmpdir(), "t3-vacuum-posix-"));
+    try {
+      const source = NodePath.join(dir, "state.sqlite");
+      const destination = NodePath.join(dir, "back\\up");
+      seedSqlite(source);
+      vacuumDatabaseInto(source, destination);
+      assert.isTrue(NodeFS.existsSync(destination));
+      assert.isFalse(NodeFS.existsSync(NodePath.join(dir, "back", "up")));
+    } finally {
+      await NodeFSP.rm(dir, { recursive: true, force: true });
+    }
+  },
+);
+
 it("rejects contradictory service state", () => {
   assert.isUndefined(
     decodeServiceState({
@@ -130,7 +192,7 @@ it.layer(NodeServices.layer)("service state persistence", (it) => {
       const statePath = path.join(root, "runtime", "service-state.json");
       const databasePath = path.join(root, "userdata", "state.sqlite");
       yield* fs.makeDirectory(path.dirname(databasePath), { recursive: true });
-      yield* fs.writeFileString(databasePath, "before trial");
+      seedSqlite(databasePath);
       // @effect-diagnostics-next-line preferSchemaOverJson:off - embeds a path in fake child source.
       const encodedDatabasePath = JSON.stringify(databasePath);
       const childSource = `
@@ -183,7 +245,7 @@ if (context.update?.status === "pending") {
       const statePath = path.join(root, "runtime", "service-state.json");
       const databasePath = path.join(root, "userdata", "state.sqlite");
       yield* fs.makeDirectory(path.dirname(databasePath), { recursive: true });
-      yield* fs.writeFileString(databasePath, "before trial");
+      seedSqlite(databasePath);
       // @effect-diagnostics-next-line preferSchemaOverJson:off - embeds a path in fake child source.
       const encodedDatabasePath = JSON.stringify(databasePath);
       const childSource = `
@@ -236,16 +298,21 @@ if (context.update?.status === "pending") {
       const root = yield* fs.makeTempDirectoryScoped({ prefix: "t3-service-launcher-db-" });
       const statePath = path.join(root, "runtime", "service-state.json");
       const databasePath = path.join(root, "userdata", "state.sqlite");
-      const original = "database before migration";
       yield* fs.makeDirectory(path.dirname(databasePath), { recursive: true });
-      yield* fs.writeFileString(databasePath, original);
+      seedSqlite(databasePath);
       // @effect-diagnostics-next-line preferSchemaOverJson:off - embeds a path in fake child source.
       const encodedDatabasePath = JSON.stringify(databasePath);
       const childSource = `
 import { writeFileSync } from "node:fs";
+import { DatabaseSync } from "node:sqlite";
 const context = JSON.parse(process.env.T3_SERVICE_LAUNCHER_CONTEXT);
 if (context.update?.status === "pending") {
-  writeFileSync(context.update.dbPath, "database after migration");
+  const db = new DatabaseSync(context.update.dbPath);
+  try {
+    db.exec("UPDATE kv SET v = 'after'");
+  } finally {
+    db.close();
+  }
   writeFileSync(context.update.dbPath + "-wal", "trial wal");
   writeFileSync(context.update.dbPath + "-shm", "trial shm");
   process.exit(1);
@@ -281,7 +348,15 @@ if (context.update?.status === "pending") {
       const state = yield* Effect.promise(() => readServiceState(statePath));
       assert.equal(state.activeVersion, "1.0.0");
       assert.equal(state.update?.status, "rolled-back");
-      assert.equal(yield* fs.readFileString(databasePath), original);
+      const restored = new DatabaseSync(databasePath, { readOnly: true });
+      try {
+        const row = restored.prepare("SELECT v AS v FROM kv WHERE k = 'phase'").get() as {
+          v: string;
+        };
+        assert.equal(row.v, "before");
+      } finally {
+        restored.close();
+      }
       assert.isFalse(yield* fs.exists(`${databasePath}-wal`));
       assert.isFalse(yield* fs.exists(`${databasePath}-shm`));
       const updateId = state.update?.id;
diff --git a/apps/server/src/serviceLauncher.ts b/apps/server/src/serviceLauncher.ts
index 68f3c346759d..924ce5682c21 100644
--- a/apps/server/src/serviceLauncher.ts
+++ b/apps/server/src/serviceLauncher.ts
@@ -8,6 +8,7 @@ import * as NodeCrypto from "node:crypto";
 import * as NodeFS from "node:fs";
 import * as NodeFSP from "node:fs/promises";
 import * as NodePath from "node:path";
+import { DatabaseSync } from "node:sqlite";
 
 import type {
   PendingServiceUpdate,
@@ -89,10 +90,29 @@ async function syncDirectory(directory: string): Promise<void> {
   }
 }
 
+function quoteSqliteLiteral(value: string): string {
+  return `'${value.replaceAll("'", "''")}'`;
+}
+
+export function vacuumDatabaseInto(sourcePath: string, destinationPath: string): void {
+  const db = new DatabaseSync(sourcePath, { readOnly: true });
+  try {
+    const vacuumPath =
+      NodePath.sep === "\\" ? destinationPath.replaceAll("\\", "/") : destinationPath;
+    db.exec(`VACUUM INTO ${quoteSqliteLiteral(vacuumPath)}`);
+  } finally {
+    db.close();
+  }
+}
+
 /**
  * Snapshots the database once per update before the first trial. A completed
  * backup is never overwritten because a restarted launcher may be looking at
  * database writes from an earlier attempt by the same trial.
+ *
+ * VACUUM INTO writes one consistent file. A live copy of sqlite plus WAL plus
+ * shm can be a torn snapshot. WAL does not survive VACUUM INTO, so restore
+ * copies this file and drops leftover sidecars.
  */
 async function backupDatabaseOnce(baseDir: string, pending: PendingServiceUpdate): Promise<void> {
   const backupDir = databaseBackupDir(baseDir, pending.id);
@@ -102,13 +122,10 @@ async function backupDatabaseOnce(baseDir: string, pending: PendingServiceUpdate
   await NodeFSP.rm(stagingDir, { recursive: true, force: true });
   await NodeFSP.mkdir(stagingDir, { recursive: true, mode: 0o700 });
   try {
-    for (const suffix of DB_FILE_SUFFIXES) {
-      const source = `${pending.dbPath}${suffix}`;
-      if (suffix !== "" && !(await pathExists(source))) continue;
-      const destination = databaseBackupFile(stagingDir, suffix);
-      await NodeFSP.copyFile(source, destination);
-      await syncFile(destination);
-    }
+    const destination = databaseBackupFile(stagingDir, "");
+    vacuumDatabaseInto(pending.dbPath, destination);
+    await NodeFSP.chmod(destination, 0o600);
+    await syncFile(destination);
     await NodeFSP.rename(stagingDir, backupDir);
     await syncDirectory(NodePath.dirname(backupDir));
   } catch (cause) {
@@ -376,7 +393,8 @@ export class Launcher {
   }
 
   async #startTrial(pending: PendingServiceUpdate): Promise<void> {
-    // The previous child is dead here, so all three SQLite files are quiescent.
+    // The previous child is dead here. VACUUM INTO still snapshots one
+    // consistent file if a sidecar is left behind.
     try {
       await backupDatabaseOnce(this.#baseDir, pending);
     } catch {