diff --git a/test/remote_child_endpoint.zig b/test/remote_child_endpoint.zig
index 379136e..47d771a 100644
--- a/test/remote_child_endpoint.zig
+++ b/test/remote_child_endpoint.zig
@@ -18,6 +18,16 @@ const cbor = @import("cbor");
 const framing = @import("framing");
 const protocol = @import("protocol");
 
+var trace_file: ?std.fs.File = null;
+var trace_buf: [4096]u8 = undefined;
+var trace_file_writer: std.fs.File.Writer = undefined;
+
+fn trace_handler(buf: tp.message.c_buffer_type) callconv(.c) void {
+    if (trace_file == null) return;
+    cbor.toJsonWriter(buf.base[0..buf.len], &trace_file_writer.interface, .{}) catch return;
+    trace_file_writer.interface.writeByte('\n') catch return;
+}
+
 // ---------------------------------------------------------------------------
 // EchoActor (wire ID 2)
 // ---------------------------------------------------------------------------
@@ -150,8 +160,6 @@ const StdioEndpoint = struct {
     }
 
     fn init(args: Args) !void {
-        tp.trace_to_json_file("remote_child_endpoint_trace.json");
-        tp.env.get().enable_all_channels();
         const fd_stdin = try tp.file_descriptor.init("stdin", 0);
         const self = try args.allocator.create(@This());
         self.* = .{
@@ -282,6 +290,17 @@ pub fn main() !void {
     defer _ = gpa.deinit();
     const allocator = gpa.allocator();
 
+    var initial_env: ?tp.env = null;
+    if (std.posix.getenv("TRACE") != null) {
+        const f = try std.fs.cwd().createFile("remote_child_endpoint_trace.json", .{});
+        trace_file = f;
+        trace_file_writer = f.writer(&trace_buf);
+        var e = tp.env.init();
+        e.on_trace(&trace_handler);
+        e.enable_all_channels();
+        initial_env = e;
+    }
+
     var ctx = try tp.context.init(allocator);
     defer ctx.deinit();
 
@@ -299,10 +318,17 @@ pub fn main() !void {
         StdioEndpoint.start,
         "stdio_endpoint",
         &exit_handler,
-        null,
+        if (initial_env) |*e| e else null,
     );
 
     ctx.run();
 
+    if (initial_env) |e| {
+        trace_file_writer.interface.flush() catch {};
+        trace_file.?.close();
+        trace_file = null;
+        e.deinit();
+    }
+
     std.process.exit(if (exit_ok) 0 else 1);
 }
diff --git a/test/remote_endpoint_id_test.zig b/test/remote_endpoint_id_test.zig
index 5a6dd5a..267dee6 100644
--- a/test/remote_endpoint_id_test.zig
+++ b/test/remote_endpoint_id_test.zig
@@ -11,9 +11,20 @@
 ///   5. TestActor receives ["done"] → exits "success".
 const std = @import("std");
 const thespian = @import("thespian");
+const cbor = @import("cbor");
 const endpoint = @import("endpoint");
 const build_options = @import("build_options");
 
+var trace_file: ?std.fs.File = null;
+var trace_buf: [4096]u8 = undefined;
+var trace_file_writer: std.fs.File.Writer = undefined;
+
+fn trace_handler(buf: thespian.message.c_buffer_type) callconv(.c) void {
+    if (trace_file == null) return;
+    cbor.toJsonWriter(buf.base[0..buf.len], &trace_file_writer.interface, .{}) catch return;
+    trace_file_writer.interface.writeByte('\n') catch return;
+}
+
 const Allocator = std.mem.Allocator;
 const result = thespian.result;
 const unexpected = thespian.unexpected;
@@ -34,8 +45,6 @@ const TestActor = struct {
     }
 
     fn init(args: Args) !void {
-        thespian.trace_to_json_file("remote_endpoint_id_trace.json");
-        thespian.env.get().enable_all_channels();
         thespian.env.get().proc_set("test_receiver", thespian.self_pid().ref());
 
         const argv = try args.allocator.dupe(u8, message.fmt(.{build_options.remote_child_endpoint_path}).buf);
@@ -94,6 +103,24 @@ const TestActor = struct {
 
 test "remote: inbound proxy table, from-substitution, outbound ID table, and send-by-ID routing" {
     const allocator = std.testing.allocator;
+
+    var initial_env: ?thespian.env = null;
+    if (std.posix.getenv("TRACE") != null) {
+        const f = try std.fs.cwd().createFile("remote_endpoint_id_trace.json", .{});
+        trace_file = f;
+        trace_file_writer = f.writer(&trace_buf);
+        var e = thespian.env.init();
+        e.on_trace(&trace_handler);
+        e.enable_all_channels();
+        initial_env = e;
+    }
+    defer if (initial_env) |e| {
+        trace_file_writer.interface.flush() catch {};
+        trace_file.?.close();
+        trace_file = null;
+        e.deinit();
+    };
+
     var ctx = try thespian.context.init(allocator);
     defer ctx.deinit();
 
@@ -109,7 +136,7 @@ test "remote: inbound proxy table, from-substitution, outbound ID table, and sen
         TestActor.start,
         "test_actor",
         &exit_handler,
-        null,
+        if (initial_env) |*e| e else null,
     );
 
     ctx.run();