more tweaks

packages/svelte/src/internal/client/dev/tracing.js

@@ -126,17 +126,22 @@ export function trace(fn, label, computed) {
 			var read_stack = ['read', get_stack()];
 
 			if (tracing_expression_reactive !== NOT_REACTIVE) {
-				var write_stack;
+				var set_stack;
 				if (signals.size === 1) {
-					write_stack = Array.from(signals)[0].stack;
+					set_stack = Array.from(signals)[0].stack;
+				}
+				var sub = null;
+				if (tracing_expressions.length !== 0) {
+					sub = tracing_expressions.slice();
+					tracing_expressions = [];
 				}
 				tracing_expressions.push({
 					changed: tracing_expression_reactive === REACTIVE_CHANGED,
 					label,
 					value,
 					time,
-					stacks: write_stack ? [read_stack, write_stack] : [read_stack],
-					sub: null
+					stacks: set_stack ? [read_stack, set_stack] : [read_stack],
+					sub
 				});
 
 				if (previously_tracing_expressions !== null) {

packages/svelte/src/internal/client/reactivity/deriveds.js

@@ -24,6 +24,7 @@ import { equals, safe_equals } from './equality.js';
 import * as e from '../errors.js';
 import { destroy_effect } from './effects.js';
 import { inspect_effects, set_inspect_effects } from './sources.js';
+import { get_stack } from '../dev/tracing.js';
 
 /**
  * @template V
@@ -56,6 +57,10 @@ export function derived(fn) {
 		parent: active_effect
 	};
 
+	if (DEV) {
+		signal.stack = ['created', get_stack()];
+	}
+
 	if (active_reaction !== null && (active_reaction.f & DERIVED) !== 0) {
 		var derived = /** @type {Derived} */ (active_reaction);
 		(derived.children ??= []).push(signal);