feat: Streamline isolation scope handling & reset in isolation scopes

[mydea]

This PR does two things:

1. Removes any usage of propagation context on isolation scope. We never really need/read this, as the current scope one will always overwrite this. Generally we should only ever set/read propagation context on current scope.
2. Adjust server-side withIsolationScope to reset the propagation context unless it is continuing a trace. Today, this kind of works in otel-based places because we wrap root spans in startNewTrace. But this does not align with core/browser handling, so going forward this will be removed. instead, we want this logic to be applied in an isolation scope, so the following code will result in separate traces:

Sentry.withIsolationScope(() => {
  Sentry.startSpan({ name: 'process 1' }, () => ...);
});

Sentry.withIsolationScope(() => {
  Sentry.startSpan({ name: 'process 2' }, () => ...);
});

without this change, both of these spans would be part of the same trace, which is not what we want in server.

note: In browser, we do not actually fork the isolation scope, there is just a single one, so this does not apply.

[github-actions]

size-limit report 📦

Path	Size	% Change	Change
@sentry/browser	29.91 kB	-	-
@sentry/browser - with treeshaking flags	28.11 kB	-	-
@sentry/browser (incl. Tracing)	47.36 kB	-0.04%	-15 B 🔽
@sentry/browser (incl. Tracing + Span Streaming)	47.37 kB	-0.03%	-14 B 🔽
@sentry/browser (incl. Tracing, Profiling)	52.14 kB	-0.03%	-11 B 🔽
@sentry/browser (incl. Tracing, Replay)	86.7 kB	-0.02%	-11 B 🔽
@sentry/browser (incl. Tracing, Replay) - with treeshaking flags	76.14 kB	-0.02%	-9 B 🔽
@sentry/browser (incl. Tracing, Replay with Canvas)	91.42 kB	-0.01%	-8 B 🔽
@sentry/browser (incl. Tracing, Replay, Feedback)	104.06 kB	-0.01%	-7 B 🔽
@sentry/browser (incl. Feedback)	47.22 kB	-	-
@sentry/browser (incl. sendFeedback)	34.76 kB	-	-
@sentry/browser (incl. FeedbackAsync)	39.86 kB	-	-
@sentry/browser (incl. Metrics)	30.99 kB	-	-
@sentry/browser (incl. Logs)	31.22 kB	-	-
@sentry/browser (incl. Metrics & Logs)	31.89 kB	-	-
@sentry/react	31.73 kB	-	-
@sentry/react (incl. Tracing)	49.62 kB	-0.05%	-20 B 🔽
@sentry/vue	34.98 kB	-	-
@sentry/vue (incl. Tracing)	49.35 kB	-0.03%	-13 B 🔽
@sentry/svelte	29.94 kB	-	-
CDN Bundle	31.98 kB	-	-
CDN Bundle (incl. Tracing)	47.72 kB	-0.03%	-10 B 🔽
CDN Bundle (incl. Logs, Metrics)	33.55 kB	-	-
CDN Bundle (incl. Tracing, Logs, Metrics)	49.08 kB	-0.02%	-8 B 🔽
CDN Bundle (incl. Replay, Logs, Metrics)	72.9 kB	-	-
CDN Bundle (incl. Tracing, Replay)	85.35 kB	-0.02%	-9 B 🔽
CDN Bundle (incl. Tracing, Replay, Logs, Metrics)	86.65 kB	-0.02%	-10 B 🔽
CDN Bundle (incl. Tracing, Replay, Feedback)	91.14 kB	-0.02%	-13 B 🔽
CDN Bundle (incl. Tracing, Replay, Feedback, Logs, Metrics)	92.46 kB	-0.02%	-10 B 🔽
CDN Bundle - uncompressed	95.49 kB	-	-
CDN Bundle (incl. Tracing) - uncompressed	143.11 kB	-0.1%	-137 B 🔽
CDN Bundle (incl. Logs, Metrics) - uncompressed	100.2 kB	-	-
CDN Bundle (incl. Tracing, Logs, Metrics) - uncompressed	147.09 kB	-0.1%	-137 B 🔽
CDN Bundle (incl. Replay, Logs, Metrics) - uncompressed	224.96 kB	-	-
CDN Bundle (incl. Tracing, Replay) - uncompressed	262.37 kB	-0.06%	-137 B 🔽
CDN Bundle (incl. Tracing, Replay, Logs, Metrics) - uncompressed	266.34 kB	-0.06%	-137 B 🔽
CDN Bundle (incl. Tracing, Replay, Feedback) - uncompressed	276.08 kB	-0.05%	-137 B 🔽
CDN Bundle (incl. Tracing, Replay, Feedback, Logs, Metrics) - uncompressed	280.03 kB	-0.05%	-137 B 🔽
@sentry/nextjs (client)	52.21 kB	-0.01%	-4 B 🔽
@sentry/sveltekit (client)	47.81 kB	-0.02%	-8 B 🔽
@sentry/core/server	80 kB	+0.01%	+6 B 🔺
@sentry/core/browser	51.93 kB	+0.02%	+7 B 🔺
@sentry/node	121.67 kB	+0.04%	+45 B 🔺
@sentry/node/import (ESM hook with diagnostics-channel injection)	0 B	added	added
@sentry/node - without tracing	85.22 kB	+0.07%	+52 B 🔺
@sentry/aws-serverless	93.48 kB	+0.06%	+53 B 🔺
@sentry/cloudflare (withSentry) - minified	199.25 kB	+0.04%	+69 B 🔺
⛔️ @sentry/cloudflare (withSentry) (max: 490.5 kB)	490.77 kB	+0.05%	+212 B 🔺

View base workflow run

[Lms24]

I think this is a good change!

[Lms24]

it seems like this removes a footgun where we potentially incorrectly merged a propagation context before here. I like it!

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit 65c8a4c. Configure here.}

[isaacs]

This is a good change, but there are a few gaps, which I think would result in bugs in trace propagation.

I rebased it onto develop, which picked up the fix for one missing case, which was fixed on 46f7431 as part of #22889.

For the others, I added commits with tests and fixes here: https://gist.github.com/isaacs/790e2d23abeebddf5b9079f53e4fbf45 or on the isaacs/fix-fn/streamline-acs-isolation-scope branch.

I figured this is probably more useful than just comments, since I'm going to be out next 2 weeks, so whoever picks this up can inspect and land with those additions, or go a different direction if you decide. 👍

[isaacs]

Should this also be updated to just scope.getPropagationContext()?

Suggested change

	} = scope.getPropagationContext();

or:

Suggested change

	} = {
	...scope.getPropagationContext(),
	};