diff --git a/README.md b/README.md
index 73f7c48..1f04b92 100644
--- a/README.md
+++ b/README.md
@@ -125,6 +125,7 @@ Backend:
 
 ```bash
 zig build test
+zig build test-integration
 ```
 
 Frontend:
@@ -139,6 +140,9 @@ End-to-end:
 ./tests/test_e2e.sh
 ```
 
+`zig build test-integration` runs structured backend HTTP integration tests
+against a real `nullhub` process started in a temporary home directory.
+
 ## Tech Stack
 
 - Zig 0.16.0
diff --git a/build.zig b/build.zig
index 54b11ac..8ee38eb 100644
--- a/build.zig
+++ b/build.zig
@@ -91,6 +91,26 @@ pub fn build(b: *std.Build) void {
     const run_tests = b.addRunArtifact(exe_unit_tests);
     const test_step = b.step("test", "Run unit tests");
     test_step.dependOn(&run_tests.step);
+
+    const integration_test_module = b.createModule(.{
+        .root_source_file = b.path("src/integration_tests.zig"),
+        .target = target,
+        .optimize = optimize,
+        .link_libc = true,
+    });
+    integration_test_module.addImport("build_options", build_options_module);
+    integration_test_module.addImport("ui_assets", ui_assets_module);
+    integration_test_module.addImport("compat", compat_module);
+
+    const integration_tests = b.addTest(.{
+        .root_module = integration_test_module,
+    });
+    const run_integration_tests = b.addRunArtifact(integration_tests);
+    run_integration_tests.step.dependOn(b.getInstallStep());
+    run_integration_tests.setCwd(b.path("."));
+    run_integration_tests.setEnvironmentVariable("NULLHUB_INTEGRATION_BIN", "zig-out/bin/nullhub");
+    const integration_test_step = b.step("test-integration", "Run integration tests");
+    integration_test_step.dependOn(&run_integration_tests.step);
 }
 
 fn createUiAssetsModule(b: *std.Build, embed_ui: bool) *std.Build.Module {
diff --git a/src/integration_tests.zig b/src/integration_tests.zig
new file mode 100644
index 0000000..8da8e02
--- /dev/null
+++ b/src/integration_tests.zig
@@ -0,0 +1,305 @@
+const std = @import("std");
+const std_compat = @import("compat");
+const builtin = @import("builtin");
+const paths_mod = @import("core/paths.zig");
+const state_mod = @import("core/state.zig");
+
+const IntegrationServer = struct {
+    allocator: std.mem.Allocator,
+    tmp_dir: std.testing.TmpDir,
+    temp_root: []const u8,
+    home_dir: []const u8,
+    port: u16,
+    child: std_compat.process.Child,
+    env_map: std_compat.process.EnvMap,
+
+    fn start(allocator: std.mem.Allocator) !IntegrationServer {
+        if (builtin.os.tag == .wasi) return error.SkipZigTest;
+
+        return startWithSeed(allocator, struct {
+            fn call(_: *IntegrationServer) !void {}
+        }.call);
+    }
+
+    fn startWithEnv(
+        allocator: std.mem.Allocator,
+        extra_env: []const EnvEntry,
+    ) !IntegrationServer {
+        return startWithSeedAndEnv(allocator, struct {
+            fn call(_: *IntegrationServer) !void {}
+        }.call, extra_env);
+    }
+
+    fn startWithSeed(
+        allocator: std.mem.Allocator,
+        comptime seedFn: *const fn (*IntegrationServer) anyerror!void,
+    ) !IntegrationServer {
+        return startWithSeedAndEnv(allocator, seedFn, &.{});
+    }
+
+    fn startWithSeedAndEnv(
+        allocator: std.mem.Allocator,
+        comptime seedFn: *const fn (*IntegrationServer) anyerror!void,
+        extra_env: []const EnvEntry,
+    ) !IntegrationServer {
+        if (builtin.os.tag == .wasi) return error.SkipZigTest;
+
+        var tmp_dir = std.testing.tmpDir(.{});
+        errdefer tmp_dir.cleanup();
+
+        const temp_root = try std_compat.fs.Dir.wrap(tmp_dir.dir).realpathAlloc(allocator, ".");
+        errdefer allocator.free(temp_root);
+
+        const home_dir = try std.fs.path.join(allocator, &.{ temp_root, "home" });
+        errdefer allocator.free(home_dir);
+        try std_compat.fs.makeDirAbsolute(home_dir);
+
+        var server = IntegrationServer{
+            .allocator = allocator,
+            .tmp_dir = tmp_dir,
+            .temp_root = temp_root,
+            .home_dir = home_dir,
+            .port = undefined,
+            .child = undefined,
+            .env_map = undefined,
+        };
+        errdefer server.deinit();
+
+        try seedFn(&server);
+
+        const port = try reservePort();
+        server.port = port;
+        const port_text = try std.fmt.allocPrint(allocator, "{d}", .{port});
+        defer allocator.free(port_text);
+
+        const exe_path = try std_compat.process.getEnvVarOwned(allocator, "NULLHUB_INTEGRATION_BIN");
+        defer allocator.free(exe_path);
+
+        server.env_map = try std_compat.process.getEnvMap(allocator);
+        errdefer server.env_map.deinit();
+        try server.env_map.put("HOME", home_dir);
+        for (extra_env) |entry| try server.env_map.put(entry.key, entry.value);
+
+        const argv = try allocator.dupe([]const u8, &.{ exe_path, "serve", "--port", port_text, "--no-open" });
+        defer allocator.free(argv);
+
+        server.child = std_compat.process.Child.init(argv, allocator);
+        server.child.cwd = ".";
+        server.child.env_map = &server.env_map;
+        server.child.stdin_behavior = .Ignore;
+        server.child.stdout_behavior = .Ignore;
+        server.child.stderr_behavior = .Ignore;
+        try server.child.spawn();
+
+        try server.waitUntilReady();
+        return server;
+    }
+
+    fn deinit(self: *IntegrationServer) void {
+        if (@intFromPtr(self.child.argv.ptr) != 0) {
+            _ = self.child.kill() catch {};
+            _ = self.child.wait() catch {};
+        }
+        if (self.env_map.count() > 0) self.env_map.deinit();
+        self.allocator.free(self.home_dir);
+        self.allocator.free(self.temp_root);
+        self.tmp_dir.cleanup();
+        self.* = undefined;
+    }
+
+    fn waitUntilReady(self: *IntegrationServer) !void {
+        var attempt: usize = 0;
+        while (attempt < 40) : (attempt += 1) {
+            const result = self.fetch(.{ .path = "/health" });
+            if (result) |resp| {
+                defer resp.deinit(self.allocator);
+                if (resp.status == .ok) return;
+            } else |_| {}
+
+            std_compat.thread.sleep(250 * std.time.ns_per_ms);
+        }
+
+        return error.ServerNotReady;
+    }
+
+    fn fetch(self: *IntegrationServer, req: Request) !HttpResponse {
+        const url = try std.fmt.allocPrint(self.allocator, "http://127.0.0.1:{d}{s}", .{ self.port, req.path });
+        defer self.allocator.free(url);
+
+        var client: std.http.Client = .{ .allocator = self.allocator, .io = std_compat.io() };
+        defer client.deinit();
+
+        var body: std.Io.Writer.Allocating = .init(self.allocator);
+        errdefer body.deinit();
+
+        var header_buf: [1]std.http.Header = undefined;
+        const extra_headers: []const std.http.Header = if (req.body.len > 0) blk: {
+            header_buf[0] = .{ .name = "Content-Type", .value = "application/json" };
+            break :blk header_buf[0..1];
+        } else &.{};
+
+        const result = try client.fetch(.{
+            .location = .{ .url = url },
+            .method = req.method,
+            .payload = if (req.body.len > 0 or req.method.requestHasBody()) req.body else null,
+            .response_writer = &body.writer,
+            .extra_headers = extra_headers,
+        });
+
+        return .{
+            .status = result.status,
+            .body = try body.toOwnedSlice(),
+        };
+    }
+
+    fn paths(self: *IntegrationServer) !paths_mod.Paths {
+        const root = try std.fs.path.join(self.allocator, &.{ self.home_dir, ".nullhub" });
+        defer self.allocator.free(root);
+        return try paths_mod.Paths.init(self.allocator, root);
+    }
+};
+
+const EnvEntry = struct {
+    key: []const u8,
+    value: []const u8,
+};
+
+const Request = struct {
+    path: []const u8,
+    method: std.http.Method = .GET,
+    body: []const u8 = "",
+};
+
+const HttpResponse = struct {
+    status: std.http.Status,
+    body: []u8,
+
+    fn deinit(self: HttpResponse, allocator: std.mem.Allocator) void {
+        allocator.free(self.body);
+    }
+};
+
+fn reservePort() !u16 {
+    const addr = try std_compat.net.Address.resolveIp("127.0.0.1", 0);
+    var listener = try addr.listen(.{});
+    defer listener.deinit();
+    return listener.listen_address.in.getPort();
+}
+
+fn seedManagedInstance(server: *IntegrationServer, component: []const u8, name: []const u8) !void {
+    var paths = try server.paths();
+    defer paths.deinit(server.allocator);
+    try paths.ensureDirs();
+
+    const state_path = try paths.state(server.allocator);
+    defer server.allocator.free(state_path);
+    var state = state_mod.State.init(server.allocator, state_path);
+    defer state.deinit();
+
+    try state.addInstance(component, name, .{
+        .version = "1.0.0",
+        .auto_start = false,
+        .launch_mode = "gateway",
+        .verbose = false,
+    });
+    try state.save();
+}
+
+test "integration harness serves health and core api routes" {
+    var server = try IntegrationServer.start(std.testing.allocator);
+    defer server.deinit();
+
+    {
+        const resp = try server.fetch(.{ .path = "/health" });
+        defer resp.deinit(std.testing.allocator);
+        try std.testing.expectEqual(std.http.Status.ok, resp.status);
+    }
+
+    {
+        const resp = try server.fetch(.{ .path = "/api/status" });
+        defer resp.deinit(std.testing.allocator);
+        try std.testing.expectEqual(std.http.Status.ok, resp.status);
+        try std.testing.expect(std.mem.indexOf(u8, resp.body, "\"hub\"") != null);
+        try std.testing.expect(std.mem.indexOf(u8, resp.body, "\"version\"") != null);
+    }
+
+    {
+        const resp = try server.fetch(.{ .path = "/api/nonexistent" });
+        defer resp.deinit(std.testing.allocator);
+        try std.testing.expectEqual(std.http.Status.not_found, resp.status);
+    }
+}
+
+test "integration harness covers settings and config round-trips" {
+    var server = try IntegrationServer.startWithSeed(std.testing.allocator, struct {
+        fn call(srv: *IntegrationServer) !void {
+            try seedManagedInstance(srv, "nullboiler", "demo");
+        }
+    }.call);
+    defer server.deinit();
+
+    {
+        const resp = try server.fetch(.{ .path = "/api/settings" });
+        defer resp.deinit(std.testing.allocator);
+        try std.testing.expectEqual(std.http.Status.ok, resp.status);
+        try std.testing.expect(std.mem.indexOf(u8, resp.body, "\"port\":") != null);
+        try std.testing.expect(std.mem.indexOf(u8, resp.body, "\"access\"") != null);
+    }
+
+    {
+        const resp = try server.fetch(.{
+            .path = "/api/settings",
+            .method = .PUT,
+            .body = "{\"port\":19901}",
+        });
+        defer resp.deinit(std.testing.allocator);
+        try std.testing.expectEqual(std.http.Status.ok, resp.status);
+        try std.testing.expect(std.mem.indexOf(u8, resp.body, "\"status\":\"ok\"") != null);
+        try std.testing.expect(std.mem.indexOf(u8, resp.body, "\"port\":19901") != null);
+    }
+
+    {
+        const resp = try server.fetch(.{ .path = "/api/instances" });
+        defer resp.deinit(std.testing.allocator);
+        try std.testing.expectEqual(std.http.Status.ok, resp.status);
+        try std.testing.expect(std.mem.indexOf(u8, resp.body, "\"nullboiler\"") != null);
+        try std.testing.expect(std.mem.indexOf(u8, resp.body, "\"demo\"") != null);
+    }
+
+    {
+        const resp = try server.fetch(.{
+            .path = "/api/instances/nullboiler/demo/config",
+            .method = .PUT,
+            .body = "{\"gateway\":{\"port\":43123},\"provider\":\"openrouter\"}",
+        });
+        defer resp.deinit(std.testing.allocator);
+        try std.testing.expectEqual(std.http.Status.ok, resp.status);
+        try std.testing.expect(std.mem.indexOf(u8, resp.body, "\"status\":\"saved\"") != null);
+    }
+
+    {
+        const resp = try server.fetch(.{ .path = "/api/instances/nullboiler/demo/config" });
+        defer resp.deinit(std.testing.allocator);
+        try std.testing.expectEqual(std.http.Status.ok, resp.status);
+        try std.testing.expect(std.mem.indexOf(u8, resp.body, "\"gateway\"") != null);
+        try std.testing.expect(std.mem.indexOf(u8, resp.body, "43123") != null);
+    }
+
+    {
+        const resp = try server.fetch(.{ .path = "/api/instances/nullboiler/demo/config?path=gateway.port" });
+        defer resp.deinit(std.testing.allocator);
+        try std.testing.expectEqual(std.http.Status.ok, resp.status);
+        try std.testing.expect(std.mem.indexOf(u8, resp.body, "\"path\":\"gateway.port\"") != null);
+        try std.testing.expect(std.mem.indexOf(u8, resp.body, "\"value\":43123") != null);
+    }
+}
+
+test "integration harness covers orchestration proxy not configured" {
+    var server = try IntegrationServer.start(std.testing.allocator);
+    defer server.deinit();
+
+    const resp = try server.fetch(.{ .path = "/api/orchestration/runs" });
+    defer resp.deinit(std.testing.allocator);
+    try std.testing.expectEqual(std.http.Status.service_unavailable, resp.status);
+    try std.testing.expect(std.mem.indexOf(u8, resp.body, "NullBoiler not configured") != null);
+}