diff --git a/src/agents/sandbox/fs-paths.test.ts b/src/agents/sandbox/fs-paths.test.ts
index cecef5d5c73..e49ccdc2d13 100644
--- a/src/agents/sandbox/fs-paths.test.ts
+++ b/src/agents/sandbox/fs-paths.test.ts
@@ -1,3 +1,4 @@
+import path from "node:path";
 import { describe, expect, it } from "vitest";
 import type { SandboxContext } from "./types.js";
 import {
@@ -41,12 +42,12 @@ function createSandbox(overrides?: Partial<SandboxContext>): SandboxContext {
 describe("parseSandboxBindMount", () => {
   it("parses bind mode and writeability", () => {
     expect(parseSandboxBindMount("/tmp/a:/workspace-a:ro")).toEqual({
-      hostRoot: "/tmp/a",
+      hostRoot: path.resolve("/tmp/a"),
       containerRoot: "/workspace-a",
       writable: false,
     });
     expect(parseSandboxBindMount("/tmp/b:/workspace-b:rw")).toEqual({
-      hostRoot: "/tmp/b",
+      hostRoot: path.resolve("/tmp/b"),
       containerRoot: "/workspace-b",
       writable: true,
     });
@@ -70,7 +71,9 @@ describe("resolveSandboxFsPathWithMounts", () => {
       mounts,
     });
 
-    expect(resolved.hostPath).toBe("/tmp/workspace-two/docs/AGENTS.md");
+    expect(resolved.hostPath).toBe(
+      path.join(path.resolve("/tmp/workspace-two"), "docs", "AGENTS.md"),
+    );
     expect(resolved.containerPath).toBe("/workspace-two/docs/AGENTS.md");
     expect(resolved.relativePath).toBe("/workspace-two/docs/AGENTS.md");
     expect(resolved.writable).toBe(false);
@@ -86,7 +89,7 @@ describe("resolveSandboxFsPathWithMounts", () => {
       defaultContainerRoot: sandbox.containerWorkdir,
       mounts,
     });
-    expect(resolved.hostPath).toBe("/tmp/workspace/src/index.ts");
+    expect(resolved.hostPath).toBe(path.join(path.resolve("/tmp/workspace"), "src", "index.ts"));
     expect(resolved.containerPath).toBe("/workspace/src/index.ts");
     expect(resolved.relativePath).toBe("src/index.ts");
     expect(resolved.writable).toBe(true);