diff --git a/zigux/tests/phase2_install_zig_selftest_contract.zig b/zigux/tests/phase2_install_zig_selftest_contract.zig
new file mode 100644
index 00000000000000..46dafc09c6294a
--- /dev/null
+++ b/zigux/tests/phase2_install_zig_selftest_contract.zig
@@ -0,0 +1,73 @@
+const std = @import("std");
+
+fn readInstallZig(allocator: std.mem.Allocator) ![]u8 {
+    var io_instance: std.Io.Threaded = .init(allocator, .{});
+    defer io_instance.deinit();
+
+    return std.Io.Dir.cwd().readFileAlloc(
+        io_instance.io(),
+        "scripts/zigux/install-zig.py",
+        allocator,
+        .limited(96 * 1024),
+    );
+}
+
+fn expectContains(haystack: []const u8, needle: []const u8) !void {
+    try std.testing.expect(std.mem.indexOf(u8, haystack, needle) != null);
+}
+
+fn expectOrdered(haystack: []const u8, markers: []const []const u8) !void {
+    var offset: usize = 0;
+    for (markers) |marker| {
+        const relative_index = std.mem.indexOf(u8, haystack[offset..], marker) orelse return error.MarkerOutOfOrder;
+        offset += relative_index + marker.len;
+    }
+}
+
+test "install-zig self-test keeps current action-path coverage visible" {
+    const install_zig = try readInstallZig(std.testing.allocator);
+    defer std.testing.allocator.free(install_zig);
+
+    try expectContains(install_zig, "parser.add_argument('--self-test'");
+    try expectContains(install_zig, "if args.self_test:");
+    try expectContains(install_zig, "return run_self_test()");
+    try expectContains(install_zig, "print('ZIG_INSTALL_SELF_TEST=pass')");
+    try expectContains(install_zig, "print('ZIG_INSTALL_SELF_TEST_CASE_COUNT=46')");
+
+    try expectOrdered(install_zig, &.{
+        "def run_self_test() -> int:",
+        "assert normalize_os('Linux') == 'linux'",
+        "assert normalize_arch('amd64') == 'x86_64'",
+        "assert resolve_target(sample_index, 'master', 'x86_64', 'linux')",
+        "assert load_index('0.17.0-dev.87+9b177a7d2') == {}",
+        "assert load_policy_channel(policy_path, '0.15.0') == '0.17.0-dev.87+9b177a7d2'",
+        "assert verify_archive_sha256(archive_path, expected_sha256) == expected_sha256",
+        "assert retry_delay_seconds(1, default_delay=0.5, headers={'Retry-After': '60'}) == MAX_RETRY_DELAY",
+        "def resumable_open_url(target: str | urllib.request.Request",
+        "assert temp_path.read_bytes() == b'zig-data'",
+        "def throttled_download_open_url(target: str | urllib.request.Request",
+        "assert throttled_download_attempts == 2",
+        "copy_url_to_file_with_curl(",
+        "assert '--continue-at' in curl_commands[0]",
+        "assert curl_copy_calls == [",
+        "source = stage_archive(local_archive, 'https://example.invalid/archive.tar.xz', staged_archive)",
+        "assert source == 'local_archive'",
+        "source = stage_archive(None, 'https://example.invalid/archive.tar.xz', staged_archive)",
+        "assert source == 'download'",
+        "print('ZIG_INSTALL_SELF_TEST=pass')",
+        "print('ZIG_INSTALL_SELF_TEST_CASE_COUNT=46')",
+    });
+}
+
+test "install-zig self-test remains local and download-free" {
+    const install_zig = try readInstallZig(std.testing.allocator);
+    defer std.testing.allocator.free(install_zig);
+
+    try expectOrdered(install_zig, &.{
+        "if args.self_test:",
+        "return run_self_test()",
+        "policy_channel = load_policy_channel()",
+        "index = load_index(channel)",
+        "archive_source = stage_archive(local_archive, tarball_url, archive_path)",
+    });
+}
diff --git a/zigux/tests/phase2_install_zig_selftest_contract_build.zig b/zigux/tests/phase2_install_zig_selftest_contract_build.zig
new file mode 100644
index 00000000000000..aa86e32bf5a4dd
--- /dev/null
+++ b/zigux/tests/phase2_install_zig_selftest_contract_build.zig
@@ -0,0 +1,33 @@
+const std = @import("std");
+
+pub fn build(b: *std.Build) void {
+    const target = b.standardTargetOptions(.{});
+    const optimize = b.standardOptimizeOption(.{});
+
+    const root_module = b.createModule(.{
+        .root_source_file = b.path("phase2_install_zig_selftest_contract.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+
+    const contract_tests = b.addTest(.{
+        .name = "phase2-install-zig-selftest-contract",
+        .root_module = root_module,
+    });
+    const run_contract = b.addRunArtifact(contract_tests);
+    run_contract.setCwd(b.path("../.."));
+
+    const contract_step = b.step(
+        "phase2-install-zig-selftest-contract",
+        "Run the focused Phase 2 install-zig self-test contract from zigux/tests",
+    );
+    contract_step.dependOn(&run_contract.step);
+
+    const test_step = b.step(
+        "test",
+        "Run the focused Phase 2 install-zig self-test contract from zigux/tests",
+    );
+    test_step.dependOn(&run_contract.step);
+
+    b.default_step.dependOn(test_step);
+}