diff --git a/zigux/tests/lane17_phase1_bench_live_step_patch_applier.zig b/zigux/tests/lane17_phase1_bench_live_step_patch_applier.zig
new file mode 100644
index 00000000000000..c111efc35cd247
--- /dev/null
+++ b/zigux/tests/lane17_phase1_bench_live_step_patch_applier.zig
@@ -0,0 +1,116 @@
+const std = @import("std");
+
+const bench_self_test_step =
+    "      - name: Self-test current Phase 1 bench checker\n" ++
+    "        run: python3 scripts/zigux/check-phase1-bench.py --self-test";
+
+const bench_live_check_step =
+    "      - name: Check current Phase 1 bench packet\n" ++
+    "        run: python3 scripts/zigux/check-phase1-bench.py";
+
+const find_bit_bench_self_test_step =
+    "      - name: Self-test current Phase 1 find-bit bench anchor checker\n" ++
+    "        run: python3 scripts/zigux/check-phase1-find-bit-bench-anchors.py --self-test";
+
+const find_bit_bench_live_check_step =
+    "      - name: Check current Phase 1 find-bit bench anchor packet\n" ++
+    "        run: python3 scripts/zigux/check-phase1-find-bit-bench-anchors.py";
+
+const current_missing_handoff =
+    bench_self_test_step ++
+    "\n\n" ++
+    find_bit_bench_self_test_step ++
+    "\n\n" ++
+    find_bit_bench_live_check_step ++
+    "\n";
+
+const expected_patched_handoff =
+    bench_self_test_step ++
+    "\n\n" ++
+    bench_live_check_step ++
+    "\n\n" ++
+    find_bit_bench_self_test_step ++
+    "\n\n" ++
+    find_bit_bench_live_check_step ++
+    "\n";
+
+fn countMarkers(haystack: []const u8, needle: []const u8) usize {
+    var count: usize = 0;
+    var offset: usize = 0;
+    while (std.mem.indexOfPos(u8, haystack, offset, needle)) |index| {
+        count += 1;
+        offset = index + needle.len;
+    }
+    return count;
+}
+
+fn singleMarkerOffset(haystack: []const u8, needle: []const u8) !usize {
+    const first = std.mem.indexOf(u8, haystack, needle) orelse return error.MissingWorkflowMarker;
+    if (std.mem.indexOfPos(u8, haystack, first + needle.len, needle) != null) {
+        return error.DuplicateWorkflowMarker;
+    }
+    return first;
+}
+
+fn appendWithBenchLiveCheck(allocator: std.mem.Allocator, workflow: []const u8) ![]u8 {
+    const bench_self_test = try singleMarkerOffset(workflow, bench_self_test_step);
+    const find_bit_self_test = try singleMarkerOffset(workflow, find_bit_bench_self_test_step);
+
+    if (countMarkers(workflow, bench_live_check_step) != 0) {
+        return error.LiveBenchCheckAlreadyPresent;
+    }
+    if (bench_self_test >= find_bit_self_test) {
+        return error.WorkflowMarkerOutOfOrder;
+    }
+
+    const insert_at = bench_self_test + bench_self_test_step.len;
+    return std.mem.concat(allocator, u8, &.{
+        workflow[0..insert_at],
+        "\n\n",
+        bench_live_check_step,
+        workflow[insert_at..],
+    });
+}
+
+test "lane17 bench live patch applier inserts the exact workflow step" {
+    const patched = try appendWithBenchLiveCheck(std.testing.allocator, current_missing_handoff);
+    defer std.testing.allocator.free(patched);
+
+    try std.testing.expectEqualStrings(expected_patched_handoff, patched);
+    try std.testing.expectEqual(@as(usize, 1), countMarkers(patched, bench_live_check_step));
+}
+
+test "lane17 bench live patch applier rejects duplicate application" {
+    try std.testing.expectError(
+        error.LiveBenchCheckAlreadyPresent,
+        appendWithBenchLiveCheck(std.testing.allocator, expected_patched_handoff),
+    );
+}
+
+test "lane17 bench live patch applier rejects missing anchors" {
+    const missing_bench_self_test =
+        find_bit_bench_self_test_step ++
+        "\n\n" ++
+        find_bit_bench_live_check_step ++
+        "\n";
+
+    try std.testing.expectError(
+        error.MissingWorkflowMarker,
+        appendWithBenchLiveCheck(std.testing.allocator, missing_bench_self_test),
+    );
+}
+
+test "lane17 bench live patch applier rejects reordered anchors" {
+    const reordered_handoff =
+        find_bit_bench_self_test_step ++
+        "\n\n" ++
+        bench_self_test_step ++
+        "\n\n" ++
+        find_bit_bench_live_check_step ++
+        "\n";
+
+    try std.testing.expectError(
+        error.WorkflowMarkerOutOfOrder,
+        appendWithBenchLiveCheck(std.testing.allocator, reordered_handoff),
+    );
+}
diff --git a/zigux/tests/lane17_phase1_bench_live_step_patch_applier_build.zig b/zigux/tests/lane17_phase1_bench_live_step_patch_applier_build.zig
new file mode 100644
index 00000000000000..fa43f11b3fe71f
--- /dev/null
+++ b/zigux/tests/lane17_phase1_bench_live_step_patch_applier_build.zig
@@ -0,0 +1,29 @@
+const std = @import("std");
+
+pub fn build(b: *std.Build) void {
+    const target = b.standardTargetOptions(.{});
+    const optimize = b.standardOptimizeOption(.{});
+
+    const tests = b.addTest(.{
+        .root_module = b.createModule(.{
+            .root_source_file = b.path("lane17_phase1_bench_live_step_patch_applier.zig"),
+            .target = target,
+            .optimize = optimize,
+        }),
+    });
+
+    const run_tests = b.addRunArtifact(tests);
+    const named_step = b.step(
+        "lane17-phase1-bench-live-step-patch-applier",
+        "Run the Lane 17 Phase 1 bench live-step patch-applier proof",
+    );
+    named_step.dependOn(&run_tests.step);
+
+    const test_step = b.step(
+        "test",
+        "Run the Lane 17 Phase 1 bench live-step patch-applier proof",
+    );
+    test_step.dependOn(&run_tests.step);
+
+    b.default_step.dependOn(named_step);
+}