diff --git a/src/infra/os-summary.test.ts b/src/infra/os-summary.test.ts
new file mode 100644
index 00000000000..533321f8dba
--- /dev/null
+++ b/src/infra/os-summary.test.ts
@@ -0,0 +1,64 @@
+import os from "node:os";
+import { afterEach, describe, expect, it, vi } from "vitest";
+
+const spawnSyncMock = vi.hoisted(() => vi.fn());
+
+vi.mock("node:child_process", () => ({
+  spawnSync: (...args: unknown[]) => spawnSyncMock(...args),
+}));
+
+import { resolveOsSummary } from "./os-summary.js";
+
+describe("resolveOsSummary", () => {
+  afterEach(() => {
+    vi.restoreAllMocks();
+  });
+
+  it("formats darwin labels from sw_vers output", () => {
+    vi.spyOn(os, "platform").mockReturnValue("darwin");
+    vi.spyOn(os, "release").mockReturnValue("24.0.0");
+    vi.spyOn(os, "arch").mockReturnValue("arm64");
+    spawnSyncMock.mockReturnValue({
+      stdout: " 15.4 \n",
+      stderr: "",
+      pid: 1,
+      output: [],
+      status: 0,
+      signal: null,
+    });
+
+    expect(resolveOsSummary()).toEqual({
+      platform: "darwin",
+      arch: "arm64",
+      release: "24.0.0",
+      label: "macos 15.4 (arm64)",
+    });
+  });
+
+  it("falls back to os.release when sw_vers output is blank", () => {
+    vi.spyOn(os, "platform").mockReturnValue("darwin");
+    vi.spyOn(os, "release").mockReturnValue("24.1.0");
+    vi.spyOn(os, "arch").mockReturnValue("x64");
+    spawnSyncMock.mockReturnValue({
+      stdout: "   ",
+      stderr: "",
+      pid: 1,
+      output: [],
+      status: 0,
+      signal: null,
+    });
+
+    expect(resolveOsSummary().label).toBe("macos 24.1.0 (x64)");
+  });
+
+  it("formats windows and non-darwin labels from os metadata", () => {
+    vi.spyOn(os, "release").mockReturnValue("10.0.26100");
+    vi.spyOn(os, "arch").mockReturnValue("x64");
+
+    vi.spyOn(os, "platform").mockReturnValue("win32");
+    expect(resolveOsSummary().label).toBe("windows 10.0.26100 (x64)");
+
+    vi.spyOn(os, "platform").mockReturnValue("linux");
+    expect(resolveOsSummary().label).toBe("linux 10.0.26100 (x64)");
+  });
+});
diff --git a/src/infra/tailnet.test.ts b/src/infra/tailnet.test.ts
new file mode 100644
index 00000000000..eeb259cbeb4
--- /dev/null
+++ b/src/infra/tailnet.test.ts
@@ -0,0 +1,54 @@
+import os from "node:os";
+import { afterEach, describe, expect, it, vi } from "vitest";
+import {
+  isTailnetIPv4,
+  listTailnetAddresses,
+  pickPrimaryTailnetIPv4,
+  pickPrimaryTailnetIPv6,
+} from "./tailnet.js";
+
+describe("tailnet helpers", () => {
+  afterEach(() => {
+    vi.restoreAllMocks();
+  });
+
+  it("detects tailscale ipv4 ranges", () => {
+    expect(isTailnetIPv4("100.64.0.1")).toBe(true);
+    expect(isTailnetIPv4("100.127.255.254")).toBe(true);
+    expect(isTailnetIPv4("100.63.255.255")).toBe(false);
+    expect(isTailnetIPv4("192.168.1.10")).toBe(false);
+  });
+
+  it("lists unique non-internal tailnet addresses only", () => {
+    vi.spyOn(os, "networkInterfaces").mockReturnValue({
+      lo0: [{ address: "127.0.0.1", family: "IPv4", internal: true, netmask: "" }],
+      en0: [
+        { address: " 100.88.1.5 ", family: "IPv4", internal: false, netmask: "" },
+        { address: "100.88.1.5", family: "IPv4", internal: false, netmask: "" },
+        { address: "fd7a:115c:a1e0::1", family: "IPv6", internal: false, netmask: "" },
+        { address: " ", family: "IPv6", internal: false, netmask: "" },
+        { address: "fe80::1", family: "IPv6", internal: false, netmask: "" },
+      ],
+      // oxlint-disable-next-line typescript/no-explicit-any
+    } as any);
+
+    expect(listTailnetAddresses()).toEqual({
+      ipv4: ["100.88.1.5"],
+      ipv6: ["fd7a:115c:a1e0::1"],
+    });
+  });
+
+  it("picks the first available tailnet addresses", () => {
+    vi.spyOn(os, "networkInterfaces").mockReturnValue({
+      utun1: [
+        { address: "100.99.1.1", family: "IPv4", internal: false, netmask: "" },
+        { address: "100.99.1.2", family: "IPv4", internal: false, netmask: "" },
+        { address: "fd7a:115c:a1e0::9", family: "IPv6", internal: false, netmask: "" },
+      ],
+      // oxlint-disable-next-line typescript/no-explicit-any
+    } as any);
+
+    expect(pickPrimaryTailnetIPv4()).toBe("100.99.1.1");
+    expect(pickPrimaryTailnetIPv6()).toBe("fd7a:115c:a1e0::9");
+  });
+});