diff --git a/README.md b/README.md
index 797659f2ecff5539e258837a81441446f3e2cbe3..01b3f584e0d9443e836af253d97be24e2f718f24 100644
--- a/README.md
+++ b/README.md
@@ -15,17 +15,18 @@ in your program:
 ```zig
 const std = @import("std");
 const tracer = @import("tracer");
+const nfs = @import("nfs");
 pub const build_options = @import("build_options");
 
 pub const tracer_impl = tracer.spall; // see 'Backends' section below
 
 pub fn main() !void {
-    try tracer.init();
+    try tracer.init(.{});
     defer tracer.deinit();
 
     // main loop
     while (true) {
-        try tracer.init_thread();
+        try tracer.init_thread(.{nfs.cwd()});
         defer tracer.deinit_thread();
 
         handler();
diff --git a/src/chrome.zig b/src/chrome.zig
index db436c6f66e7572472a37002788518bd661feb8d..db54400d5ebfe61c19d3836de084c39683e1b33b 100644
--- a/src/chrome.zig
+++ b/src/chrome.zig
@@ -14,7 +14,8 @@ threadlocal var path: [:0]const u8 = undefined;
 threadlocal var file: nfs.File = undefined;
 threadlocal var buffered_writer: nio.BufferedWriter(4096, nfs.File) = undefined;
 
-pub fn init() !void {
+pub fn init(args: struct {}) !void {
+    _ = args;
     pid = linux.getpid();
 }
 
@@ -22,7 +23,8 @@ pub fn deinit() void {
     //
 }
 
-pub fn init_thread(dir: nfs.Dir) !void {
+pub fn init_thread(args: struct { nfs.Dir }) !void {
+    const dir = args[0];
     tid = linux.gettid();
 
     path = try std.fmt.allocPrintZ(alloc, "trace.{d}.{d}.chrome.json", .{ pid, tid });
diff --git a/src/log.zig b/src/log.zig
index c5a0eb714f99cfdc6ddc745c144048f46d6c2adc..5eb0b88e55e8b9e3a570f4cc4cc9e5bd5ca12f52 100644
--- a/src/log.zig
+++ b/src/log.zig
@@ -1,14 +1,15 @@
 const std = @import("std");
 const tracer = @import("./mod.zig");
 const log = std.log.scoped(.tracer);
-const nfs = @import("nfs");
 
-pub fn init() !void {}
+pub fn init(args: struct {}) !void {
+    _ = args;
+}
 
 pub fn deinit() void {}
 
-pub fn init_thread(dir: nfs.Dir) !void {
-    _ = dir;
+pub fn init_thread(args: struct {}) !void {
+    _ = args;
 }
 
 pub fn deinit_thread() void {}
diff --git a/src/main.zig b/src/main.zig
index 9bee6ee685dc5f7f1d1f83f278cb906ba992638e..f93bcec1e2aa3f773effbbf55d198d824d12b53d 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -13,14 +13,18 @@ pub const tracer_impl = switch (build_options.backend) {
 };
 
 pub fn main() !void {
-    try tracer.init();
+    try tracer.init(.{});
     defer tracer.deinit();
 
     // main loop
     var go = false;
     _ = &go;
     while (go) {
-        try tracer.init_thread(nfs.cwd());
+        try tracer.init_thread(switch (build_options.backend) {
+            0, 1 => .{},
+            2, 3 => .{nfs.cwd()},
+            else => comptime unreachable,
+        });
         defer tracer.deinit_thread();
 
         handler();
diff --git a/src/mod.zig b/src/mod.zig
index 762334869e2efb47f1055ef4be8b284819c16990..ba675c05440cad2ceeb77f6f18230e6e3b21537a 100644
--- a/src/mod.zig
+++ b/src/mod.zig
@@ -11,16 +11,16 @@ pub const log = @import("./log.zig");
 pub const chrome = @import("./chrome.zig");
 pub const spall = @import("./spall.zig");
 
-pub fn init() !void {
-    try impl.init();
+pub fn init(args: @typeInfo(@TypeOf(impl.init)).@"fn".params[0].type.?) !void {
+    try impl.init(args);
 }
 
 pub fn deinit() void {
     impl.deinit();
 }
 
-pub fn init_thread(dir: ?nfs.Dir) !void {
-    try impl.init_thread(dir orelse nfs.cwd());
+pub fn init_thread(args: @typeInfo(@TypeOf(impl.init_thread)).@"fn".params[0].type.?) !void {
+    try impl.init_thread(args);
     started = true;
 }
 
diff --git a/src/none.zig b/src/none.zig
index 4208d976dae11390bacf24935eab8a9213ceefb2..e9034a9e3b978fa44ce3b6b2220a89c4305754ff 100644
--- a/src/none.zig
+++ b/src/none.zig
@@ -1,14 +1,15 @@
 const std = @import("std");
 const tracer = @import("./mod.zig");
 const log = std.log.scoped(.tracer);
-const nfs = @import("nfs");
 
-pub fn init() !void {}
+pub fn init(args: struct {}) !void {
+    _ = args;
+}
 
 pub fn deinit() void {}
 
-pub fn init_thread(dir: nfs.Dir) !void {
-    _ = dir;
+pub fn init_thread(args: struct {}) !void {
+    _ = args;
 }
 
 pub fn deinit_thread() void {}
diff --git a/src/spall.zig b/src/spall.zig
index a4b8b89654a306a968d094eacf5c1ab2ce793792..406c9e1c996cb5420971116b43b3e52a2da57705 100644
--- a/src/spall.zig
+++ b/src/spall.zig
@@ -14,7 +14,8 @@ threadlocal var path: [:0]const u8 = undefined;
 threadlocal var file: nfs.File = undefined;
 threadlocal var buffered_writer: nio.BufferedWriter(4096, nfs.File) = undefined;
 
-pub fn init() !void {
+pub fn init(args: struct {}) !void {
+    _ = args;
     pid = linux.getpid();
 }
 
@@ -22,7 +23,8 @@ pub fn deinit() void {
     //
 }
 
-pub fn init_thread(dir: nfs.Dir) !void {
+pub fn init_thread(args: struct { nfs.Dir }) !void {
+    const dir = args[0];
     tid = linux.gettid();
 
     path = try std.fmt.allocPrintZ(alloc, "{d}.{d}.spall", .{ pid, tid });