diff --git a/package-lock.json b/package-lock.json
index 1f73e64..24d1e26 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "@agent-relay/sandbox",
-  "version": "0.1.8",
+  "version": "0.1.9",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@agent-relay/sandbox",
-      "version": "0.1.8",
+      "version": "0.1.9",
       "license": "Apache-2.0",
       "devDependencies": {
         "@aws-sdk/client-bedrock-agentcore": "^3.1115.0",
diff --git a/package.json b/package.json
index a7d7798..089c683 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@agent-relay/sandbox",
-  "version": "0.1.8",
+  "version": "0.1.9",
   "description": "Provider-agnostic sandbox runtimes and orchestration for agent workloads.",
   "license": "Apache-2.0",
   "type": "module",
diff --git a/src/orchestrator.flush-mount.test.ts b/src/orchestrator.flush-mount.test.ts
new file mode 100644
index 0000000..b665c43
--- /dev/null
+++ b/src/orchestrator.flush-mount.test.ts
@@ -0,0 +1,70 @@
+import { strict as assert } from "node:assert";
+import { describe, it } from "node:test";
+
+import {
+  SandboxOrchestrator,
+  type SandboxRunScriptOptions,
+} from "./orchestrator.js";
+
+function recordingOrchestrator(): {
+  orchestrator: SandboxOrchestrator<string>;
+  calls: SandboxRunScriptOptions[];
+} {
+  const calls: SandboxRunScriptOptions[] = [];
+  return {
+    calls,
+    orchestrator: new SandboxOrchestrator<string>({
+      runScript: async (_handle, options) => {
+        calls.push(options);
+        return { output: "", exitCode: 0 };
+      },
+    }),
+  };
+}
+
+describe("flushMount exact-root timeout budget", () => {
+  it("keeps the pathless mount at one default allowance", async () => {
+    const { orchestrator, calls } = recordingOrchestrator();
+
+    await orchestrator.flushMount("sandbox-1", {
+      baseUrl: "https://relayfile.example",
+      workspaceId: "rw_abc12345",
+      localDir: "/home/daytona/workspace",
+      stateDir: "/home/daytona/.relayfile-mount-state",
+      token: "relay_pa_test",
+    });
+
+    assert.equal(calls.length, 1);
+    assert.equal(calls[0]?.timeoutMs, 120_000);
+  });
+
+  it("budgets the default allowance for every sequential exact root", async () => {
+    const { orchestrator, calls } = recordingOrchestrator();
+
+    const config = {
+      baseUrl: "https://relayfile.example",
+      workspaceId: "rw_abc12345",
+      localDir: "/home/daytona/workspace",
+      stateDir: "/home/daytona/.relayfile-mount-state",
+      token: "relay_pa_test",
+      paths: [
+        "/slack/channels/C123/**",
+        "/github/repos/acme/cloud/**",
+        "/linear/issues/TEAM/**",
+      ],
+    };
+    await orchestrator.flushMount("sandbox-1", config);
+
+    assert.equal(calls.length, 1);
+    assert.equal(calls[0]?.timeoutMs, 360_000);
+
+    await orchestrator.flushMount("sandbox-1", config, { timeoutMs: 9_000 });
+
+    assert.equal(calls.length, 2);
+    assert.equal(
+      calls[1]?.timeoutMs,
+      9_000,
+      "an explicit whole-operation timeout must remain authoritative",
+    );
+  });
+});
diff --git a/src/orchestrator.ts b/src/orchestrator.ts
index a3089a1..be9191a 100644
--- a/src/orchestrator.ts
+++ b/src/orchestrator.ts
@@ -112,6 +112,10 @@ export type StartMountOptions = {
 
 export type FlushMountOptions = {
   cwd?: string;
+  /**
+   * Optional whole-operation runtime timeout. When omitted, the default
+   * allowance scales by the number of sequential exact-layout commands.
+   */
   timeoutMs?: number;
 };
 
@@ -299,10 +303,13 @@ export class SandboxOrchestrator<Handle> {
     config: RelayfileMountShellOptions,
     options: FlushMountOptions = {},
   ): Promise<void> {
+    const exactLayout = resolveRelayfileMountExactLayout(config);
+    const defaultTimeoutMs = 120_000
+      * Math.max(1, exactLayout.mountLocalDirs.length);
     const result = await this.runtime.runScript(handle, {
       command: buildRelayfileMountFlushShell(config),
       cwd: options.cwd,
-      timeoutMs: options.timeoutMs ?? 120_000,
+      timeoutMs: options.timeoutMs ?? defaultTimeoutMs,
     });
     if (result.exitCode !== 0) {
       throw new Error(`Failed to flush relayfile mount: ${result.output}`);