diff --git a/src/agents/sandbox/fs-bridge.backend.e2e.test.ts b/src/agents/sandbox/fs-bridge.backend.e2e.test.ts
new file mode 100644
index 00000000000..f458223b176
--- /dev/null
+++ b/src/agents/sandbox/fs-bridge.backend.e2e.test.ts
@@ -0,0 +1,125 @@
+import { spawn } from "node:child_process";
+import fs from "node:fs/promises";
+import os from "node:os";
+import path from "node:path";
+import { describe, expect, it } from "vitest";
+import type {
+  SandboxBackendHandle,
+  SandboxBackendCommandParams,
+  SandboxBackendCommandResult,
+} from "./backend-handle.types.js";
+
+async function runLocalShellCommand(
+  params: SandboxBackendCommandParams,
+): Promise<SandboxBackendCommandResult> {
+  return await new Promise<SandboxBackendCommandResult>((resolve, reject) => {
+    const child = spawn(
+      "sh",
+      ["-c", params.script, "openclaw-sandbox-fs", ...(params.args ?? [])],
+      {
+        stdio: ["pipe", "pipe", "pipe"],
+      },
+    );
+
+    const stdoutChunks: Buffer[] = [];
+    const stderrChunks: Buffer[] = [];
+    let aborted = false;
+
+    const onAbort = () => {
+      if (aborted) {
+        return;
+      }
+      aborted = true;
+      child.kill("SIGTERM");
+    };
+    params.signal?.addEventListener("abort", onAbort);
+
+    child.stdout?.on("data", (chunk) => {
+      stdoutChunks.push(Buffer.isBuffer(chunk) ? chunk : Buffer.from(chunk));
+    });
+    child.stderr?.on("data", (chunk) => {
+      stderrChunks.push(Buffer.isBuffer(chunk) ? chunk : Buffer.from(chunk));
+    });
+
+    child.on("error", reject);
+    child.on("close", (code) => {
+      params.signal?.removeEventListener("abort", onAbort);
+      if (aborted || params.signal?.aborted) {
+        const error = new Error("Aborted");
+        error.name = "AbortError";
+        reject(error);
+        return;
+      }
+
+      const result = {
+        stdout: Buffer.concat(stdoutChunks),
+        stderr: Buffer.concat(stderrChunks),
+        code: code ?? 0,
+      };
+      if (result.code !== 0 && !params.allowFailure) {
+        reject(new Error(result.stderr.toString("utf8").trim() || `shell exited ${result.code}`));
+        return;
+      }
+      resolve(result);
+    });
+
+    if (child.stdin) {
+      child.stdin.end(params.stdin);
+    }
+  });
+}
+
+describe("sandbox fs bridge local backend e2e", () => {
+  it.runIf(process.platform !== "win32")(
+    "writes through backend shell commands using the pinned mutation helper",
+    async () => {
+      const stateDir = await fs.mkdtemp(path.join(os.tmpdir(), "openclaw-fsbridge-e2e-"));
+      const workspacePath = path.join(stateDir, "workspace");
+      await fs.mkdir(workspacePath, { recursive: true });
+      const workspaceDir = await fs.realpath(workspacePath);
+      const scripts: string[] = [];
+      const backend: SandboxBackendHandle = {
+        id: "local-test",
+        runtimeId: "local-backend-fsbridge",
+        runtimeLabel: "local-backend-fsbridge",
+        workdir: workspaceDir,
+        buildExecSpec: async ({ command, env }) => ({
+          argv: ["sh", "-c", command],
+          env,
+          stdinMode: "pipe-closed",
+        }),
+        runShellCommand: async (params) => {
+          scripts.push(params.script);
+          return await runLocalShellCommand(params);
+        },
+      };
+
+      try {
+        const [{ createSandboxFsBridge }, { createSandboxTestContext }] = await Promise.all([
+          import("./fs-bridge.js"),
+          import("./test-fixtures.js"),
+        ]);
+
+        const sandbox = createSandboxTestContext({
+          overrides: {
+            workspaceDir,
+            agentWorkspaceDir: workspaceDir,
+            containerName: "local-backend-fsbridge",
+            containerWorkdir: workspaceDir,
+            backend,
+          },
+        });
+
+        const bridge = createSandboxFsBridge({ sandbox });
+        await bridge.writeFile({ filePath: "nested/hello.txt", data: "from-backend" });
+
+        await expect(
+          fs.readFile(path.join(workspaceDir, "nested", "hello.txt"), "utf8"),
+        ).resolves.toBe("from-backend");
+        expect(scripts.some((script) => script.includes("operation = sys.argv[1]"))).toBe(true);
+      } finally {
+        await fs.rm(stateDir, { recursive: true, force: true });
+      }
+    },
+  );
+});