diff --git a/BRANCH_TODO b/BRANCH_TODO
index b54140d4a0..ffc063b7cc 100644
--- a/BRANCH_TODO
+++ b/BRANCH_TODO
@@ -77,3 +77,26 @@ closes #31397
 
 * `b.build_root` (Directory) -> `b.root` (Path)
 * `ConfigHeader.Options`: `include_guard_override` -> `include_guard`
+
+### Perf Data Point: `zig build -h` (cached)
+
+```
+Benchmark 1 (34 runs): master/zig build -h
+  measurement          mean ± σ            min … max           outliers         delta
+  wall_time           150ms ± 5.52ms     145ms …  165ms          4 (12%)        0%
+  peak_rss           84.8MB ±  275KB    84.2MB … 85.1MB          0 ( 0%)        0%
+  cpu_cycles          593M  ± 4.01M      588M  …  608M           2 ( 6%)        0%
+  instructions        995M  ± 52.5K      995M  …  995M           0 ( 0%)        0%
+  cache_references   25.8M  ±  165K     25.4M  … 26.1M           0 ( 0%)        0%
+  cache_misses        651K  ± 20.1K      619K  …  697K           0 ( 0%)        0%
+  branch_misses       918K  ± 7.44K      906K  …  935K           0 ( 0%)        0%
+Benchmark 2 (348 runs): branch/zig build -h
+  measurement          mean ± σ            min … max           outliers         delta
+  wall_time          14.3ms ±  744us    13.2ms … 23.3ms          8 ( 2%)        ⚡- 90.4% ±  0.4%
+  peak_rss           78.5MB ±  562KB    77.1MB … 81.4MB          7 ( 2%)        ⚡-  7.4% ±  0.2%
+  cpu_cycles         24.1M  ±  821K     22.8M  … 27.1M           3 ( 1%)        ⚡- 95.9% ±  0.1%
+  instructions       43.7M  ± 23.8K     43.7M  … 43.8M          56 (16%)        ⚡- 95.6% ±  0.0%
+  cache_references   1.46M  ± 14.6K     1.40M  … 1.50M          19 ( 5%)        ⚡- 94.3% ±  0.1%
+  cache_misses        142K  ± 4.87K      127K  …  157K           2 ( 1%)        ⚡- 78.1% ±  0.4%
+  branch_misses       126K  ± 1.37K      120K  …  129K          12 ( 3%)        ⚡- 86.3% ±  0.1%
+```
diff --git a/lib/compiler/Maker.zig b/lib/compiler/Maker.zig
index 48a7cf785d..d443a6ae4d 100644
--- a/lib/compiler/Maker.zig
+++ b/lib/compiler/Maker.zig
@@ -446,6 +446,9 @@ pub fn main(init: process.Init.Minimal) !void {
                 else => {},
             }
         }
+        for (c.search_prefixes) |search_prefix| {
+            try graph.search_prefixes.append(arena, search_prefix.slice(c));
+        }
         break :sc .{
             .configuration = configuration,
             .top_level_steps = top_level_steps,
diff --git a/lib/compiler/Maker/ScannedConfig.zig b/lib/compiler/Maker/ScannedConfig.zig
index 7fc7cc9608..5bb3a9871f 100644
--- a/lib/compiler/Maker/ScannedConfig.zig
+++ b/lib/compiler/Maker/ScannedConfig.zig
@@ -20,6 +20,12 @@ pub fn print(sc: *const ScannedConfig, w: *Writer) Writer.Error!void {
     var serializer: Serializer = .{ .writer = w };
     var s = try serializer.beginStruct(.{});
 
+    {
+        var tf = try s.beginTupleField("search_prefixes", .{});
+        for (c.search_prefixes) |string| try tf.field(string.slice(c), .{});
+        try tf.end();
+    }
+
     try s.field("default_step", @intFromEnum(c.default_step), .{});
     {
         var sf = try s.beginStructField("top_level_steps", .{});
diff --git a/lib/std/Build.zig b/lib/std/Build.zig
index b5eeefa171..ad87bc2466 100644
--- a/lib/std/Build.zig
+++ b/lib/std/Build.zig
@@ -295,12 +295,12 @@ fn createChild(
     pkg_deps: AvailableDeps,
     user_input_options: UserInputOptionsMap,
 ) error{OutOfMemory}!*Build {
-    const allocator = parent.allocator;
-    const child = try allocator.create(Build);
+    const arena = parent.graph.arena;
+    const child = try arena.create(Build);
     child.* = .{
         .graph = parent.graph,
         .root = root,
-        .allocator = allocator,
+        .allocator = arena,
         .install_tls = .{
             .step = .init(.{
                 .tag = .top_level,
@@ -334,8 +334,8 @@ fn createChild(
         .pkg_hash = pkg_hash,
         .available_deps = pkg_deps,
     };
-    try child.top_level_steps.put(allocator, child.install_tls.step.name, &child.install_tls);
-    try child.top_level_steps.put(allocator, child.uninstall_tls.step.name, &child.uninstall_tls);
+    try child.top_level_steps.put(arena, child.install_tls.step.name, &child.install_tls);
+    try child.top_level_steps.put(arena, child.uninstall_tls.step.name, &child.uninstall_tls);
     child.default_step = &child.install_tls.step;
     return child;
 }
@@ -1773,10 +1773,16 @@ pub fn run(b: *Build, argv: []const []const u8) []u8 {
 /// it is desirable to use that same information without requiring the user to
 /// provide it again.
 pub fn addSearchPrefix(b: *Build, search_prefix: []const u8) void {
-    _ = b;
-    _ = search_prefix;
-    @panic("TODO");
-    //b.search_prefixes.append(b.allocator, b.dupePath(search_prefix)) catch @panic("OOM");
+    if (b.isRoot()) {
+        const graph = b.graph;
+        const wc = &graph.wip_configuration;
+        const string = wc.addString(search_prefix) catch @panic("OOM");
+        wc.search_prefixes.append(wc.gpa, string) catch @panic("OOM");
+    }
+}
+
+pub fn isRoot(b: *const Build) bool {
+    return b.pkg_hash.len == 0;
 }
 
 pub const Dependency = struct {
diff --git a/lib/std/Build/Configuration.zig b/lib/std/Build/Configuration.zig
index b08fb39543..c008dcc90f 100644
--- a/lib/std/Build/Configuration.zig
+++ b/lib/std/Build/Configuration.zig
@@ -13,6 +13,7 @@ path_deps_sub: []String,
 unlazy_deps: []String,
 system_integrations: []SystemIntegration,
 available_options: []AvailableOption,
+search_prefixes: []String,
 extra: []u32,
 default_step: Step.Index,
 generated_files_len: u32,
@@ -26,6 +27,7 @@ pub const Header = extern struct {
     unlazy_deps_len: u32,
     system_integrations_len: u32,
     available_options_len: u32,
+    search_prefixes_len: u32,
     extra_len: u32,
 
     default_step: Step.Index,
@@ -47,6 +49,7 @@ pub const Wip = struct {
     available_options: std.ArrayList(AvailableOption) = .empty,
     steps: std.ArrayList(Step) = .empty,
     path_deps: std.MultiArrayList(Path) = .empty,
+    search_prefixes: std.ArrayList(String) = .empty,
     extra: std.ArrayList(u32) = .empty,
     next_generated_file_index: u32 = 0,
 
@@ -126,6 +129,7 @@ pub const Wip = struct {
         wip.available_options.deinit(gpa);
         wip.steps.deinit(gpa);
         wip.path_deps.deinit(gpa);
+        wip.search_prefixes.deinit(gpa);
         wip.extra.deinit(gpa);
         wip.* = undefined;
     }
@@ -143,6 +147,7 @@ pub const Wip = struct {
             .unlazy_deps_len = @intCast(wip.unlazy_deps.items.len),
             .system_integrations_len = @intCast(wip.system_integrations.items.len),
             .available_options_len = @intCast(wip.available_options.items.len),
+            .search_prefixes_len = @intCast(wip.search_prefixes.items.len),
             .extra_len = @intCast(wip.extra.items.len),
 
             .default_step = static.default_step,
@@ -157,6 +162,7 @@ pub const Wip = struct {
             @ptrCast(wip.unlazy_deps.items),
             @ptrCast(wip.system_integrations.items),
             @ptrCast(wip.available_options.items),
+            @ptrCast(wip.search_prefixes.items),
             @ptrCast(wip.extra.items),
         };
         try w.writeVecAll(&buffers);
@@ -3017,6 +3023,7 @@ pub fn load(arena: Allocator, reader: *Io.Reader) LoadError!Configuration {
         .unlazy_deps = try arena.alloc(String, header.unlazy_deps_len),
         .system_integrations = try arena.alloc(SystemIntegration, header.system_integrations_len),
         .available_options = try arena.alloc(AvailableOption, header.available_options_len),
+        .search_prefixes = try arena.alloc(String, header.search_prefixes_len),
         .extra = try arena.alloc(u32, header.extra_len),
         .default_step = header.default_step,
         .generated_files_len = header.generated_files_len,
@@ -3029,6 +3036,7 @@ pub fn load(arena: Allocator, reader: *Io.Reader) LoadError!Configuration {
         @ptrCast(result.unlazy_deps),
         @ptrCast(result.system_integrations),
         @ptrCast(result.available_options),
+        @ptrCast(result.search_prefixes),
         @ptrCast(result.extra),
     };
     try reader.readVecAll(&vecs);