fix(analytics): bypass Cloudflare Rocket Loader for Mixpanel snippet by rosuH · Pull Request #5 · rosuH/fx-lab

rosuH · 2026-07-06T13:57:45Z

Symptom

PR #4 fixed the SDK URL, but Mixpanel still shows zero data after deploy.

Root cause — Cloudflare Rocket Loader

The live HTML shows Rocket Loader rewrote our analytics <script>:

- <script>
+ <script type=\"bbb8cf785a6518761e24ebb8-text/javascript\">

Rocket Loader changes every inline script's type to a hashed-prefixed variant, which the browser treats as unknown → does not execute. It then defers execution to its own loader.

For the Mixpanel snippet this is fatal: the IIFE that injects the SDK never runs, so window.mixpanel is never initialized, the SDK is never loaded, and every downstream mixpanel.track(...) call is a no-op. Zero events reach Mixpanel.

Evidence the rest of the chain is fine

Tested directly (bypassing Rocket Loader):

✅ mixpanel-2-latest.min.js → HTTP 200 (PR fix(analytics): load working Mixpanel SDK (was 404) + confirm Rybbit removed #4)
✅ api-js.mixpanel.com/track/ → POST returns `1` (Mixpanel accepted the event)
✅ decide endpoint 200 → token/region (US) correct
✅ No CSP meta blocking anything

So the only remaining blocker is Rocket Loader suppressing the inline init.

Fix

Add data-cfasync=\"false\" — Cloudflare's official escape hatch that says "run this script normally, don't touch it":

- <script>
+ <script data-cfasync=\"false\">

Applied to both `site/index.html` and `web/index.html`. Also expanded the comment to explain why the attribute is there, so nobody removes it later.

After merge

Cloudflare Pages rebuilds automatically (Git integration)
Open https://fx.rosuh.me, DevTools → Network → filter `mixpanel`
Should see POST to `api-js.mixpanel.com/track/` returning `1`
Mixpanel Live View should light up within ~30s

Root cause of "no data in Mixpanel": Cloudflare Rocket Loader rewrites every inline <script>, changing type="text/javascript" into type="<hash>-text/javascript". The browser then refuses to execute it, so the Mixpanel IIFE + mixpanel.init(...) never run — the SDK is never injected and zero events are sent. The fix is the standard Cloudflare escape hatch: data-cfasync="false" tells Rocket Loader to leave this script alone and let the browser run it immediately, in document order. Verified the rest of the chain is healthy: - SDK URL mixpanel-2-latest.min.js → HTTP 200 (fixed in PR #4) - api-js.mixpanel.com/track/ → returns 1 (accepts events) - token/region correct (US decide endpoint 200) So this is the last remaining blocker.

cloudflare-workers-and-pages · 2026-07-06T13:57:46Z

Deploying fx-lab with Cloudflare Pages

Latest commit:	`0a16886`
Status:	✅ Deploy successful!
Preview URL:	https://b55e8eec.fx-lab.pages.dev
Branch Preview URL:	https://fix-mixpanel-rocket-loader.fx-lab.pages.dev

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chatgpt-codex-connector · 2026-07-06T13:59:08Z

+     data-cfasync="false" tells Cloudflare Rocket Loader to leave this script alone (run immediately, in document order).
+     Without it, Rocket Loader rewrites <script type> and the inline init never executes → zero events reach Mixpanel. -->
+<script data-cfasync="false">
+(function(f,b){if(!b.__SV){var e,g,i,h;window.mixpanel=b;b._i=[];b.init=function(a,e,d){function f(b){var c=b.split(".");2==c.length&&(b=b[c[0]],a=c[0]]=a[c[0]]||{},a=a[c[0]])}b._q.push({a:d});f("track");f("identify");f("reset");f("register");f("alias");f("people.set");f("people.increment");f("track_charge");f("append");b._i[d]={};a&&"function"==typeof a&&(b._i[d]=a)};b.__SV=1.2;e=f.createElement("script");e.type="text/javascript";e.async=!0;e.src="https://cdn.mxpnl.com/libs/mixpanel-2-latest.min.js";g=f.getElementsByTagName("script")[0];g.parentNode.insertBefore(e,g)}})(document,window.mixpanel||[]);


Restore valid Mixpanel bootstrap syntax

In browsers this inline script now fails to parse because the assignment expression was changed to a=c[0]]=..., so none of the script block runs, including mixpanel.init(...). In the deployed analytics path this leaves window.mixpanel uninitialized and keeps all events at zero despite the Rocket Loader opt-out; the same typo is present in web/index.html as well.

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Pull request overview

This PR aims to restore Mixpanel analytics by preventing Cloudflare Rocket Loader from rewriting (and effectively disabling) the inline Mixpanel bootstrap snippet, using Cloudflare’s data-cfasync="false" escape hatch.

Changes:

Add data-cfasync="false" to the inline Mixpanel <script> tag so Rocket Loader won’t rewrite/defer it.
Expand the inline comment explaining why Rocket Loader must be bypassed for this snippet.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
web/index.html	Adds Rocket Loader bypass + explanatory comment to keep the inline Mixpanel init executing.
site/index.html	Same Rocket Loader bypass + explanatory comment for the site variant of the HTML.

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+     data-cfasync="false" tells Cloudflare Rocket Loader to leave this script alone (run immediately, in document order).
+     Without it, Rocket Loader rewrites <script type> and the inline init never executes → zero events reach Mixpanel. -->
+<script data-cfasync="false">
+(function(f,b){if(!b.__SV){var e,g,i,h;window.mixpanel=b;b._i=[];b.init=function(a,e,d){function f(b){var c=b.split(".");2==c.length&&(b=b[c[0]],a=c[0]]=a[c[0]]||{},a=a[c[0]])}b._q.push({a:d});f("track");f("identify");f("reset");f("register");f("alias");f("people.set");f("people.increment");f("track_charge");f("append");b._i[d]={};a&&"function"==typeof a&&(b._i[d]=a)};b.__SV=1.2;e=f.createElement("script");e.type="text/javascript";e.async=!0;e.src="https://cdn.mxpnl.com/libs/mixpanel-2-latest.min.js";g=f.getElementsByTagName("script")[0];g.parentNode.insertBefore(e,g)}})(document,window.mixpanel||[]);


+     data-cfasync="false" tells Cloudflare Rocket Loader to leave this script alone (run immediately, in document order).
+     Without it, Rocket Loader rewrites <script type> and the inline init never executes → zero events reach Mixpanel. -->
+<script data-cfasync="false">
+(function(f,b){if(!b.__SV){var e,g,i,h;window.mixpanel=b;b._i=[];b.init=function(a,e,d){function f(b){var c=b.split(".");2==c.length&&(b=b[c[0]],a=c[0]]=a[c[0]]||{},a=a[c[0]])}b._q.push({a:d});f("track");f("identify");f("reset");f("register");f("alias");f("people.set");f("people.increment");f("track_charge");f("append");b._i[d]={};a&&"function"==typeof a&&(b._i[d]=a)};b.__SV=1.2;e=f.createElement("script");e.type="text/javascript";e.async=!0;e.src="https://cdn.mxpnl.com/libs/mixpanel-2-latest.min.js";g=f.getElementsByTagName("script")[0];g.parentNode.insertBefore(e,g)}})(document,window.mixpanel||[]);


The bootstrap IIFE shipped since 7c95a83 was a hand-edited variant with a structurally broken init stub: it called b._q.push(...) but only ever initialized b._i (never b._q), so every mixpanel.init(...) threw 'TypeError: Cannot read properties of undefined (reading push') before any tracking method (track/identify/people.set/...) could be stubbed onto the object. Result: zero events, even with a valid SDK URL and Rocket Loader bypass. PR #6 fixed one symptom (the a=c[0]] syntax typo from #5), but the underlying _q/_i logic bug remained — flagged again as P1 by Codex review on #6. Fix: replace the whole IIFE with Mixpanel's official snippet verbatim from https://docs.mixpanel.com/docs/tracking-methods/sdks/javascript. The official stub stubs out all methods (track, identify, people.*, ...) and records the init call via b._i.push([...]) — matching the SDK's own contract. Verified by executing the extracted <script> block in Node with a DOM mock: - mixpanel._i receives the init call - mixpanel.track / identify / people.set are all functions - No TypeError, no SyntaxError Same snippet in site/index.html and web/index.html. data-cfasync="false" and the existing mixpanel.init(...) config line are preserved.

* fix(analytics): restore Mixpanel IIFE syntax broken in PR #5 PR #5 (Rocket Loader bypass) accidentally introduced a typo in the Mixpanel bootstrap IIFE: a[c[0]]= became a=c[0]]=, which is a JS SyntaxError (Unexpected token ']'). The whole <script> block fails to parse, so mixpanel.init() never runs and no events are sent — the Rocket Loader fix was correct but got masked by this regression. Confirmed via `node --check` on the extracted <script> block: SyntaxError on the merged code, OK after this fix. Reported by Codex (P1) and Copilot review on PR #5. Only the two bytes a[ → a= are changed; nothing else. * fix(analytics): replace corrupted Mixpanel stub with official snippet The bootstrap IIFE shipped since 7c95a83 was a hand-edited variant with a structurally broken init stub: it called b._q.push(...) but only ever initialized b._i (never b._q), so every mixpanel.init(...) threw 'TypeError: Cannot read properties of undefined (reading push') before any tracking method (track/identify/people.set/...) could be stubbed onto the object. Result: zero events, even with a valid SDK URL and Rocket Loader bypass. PR #6 fixed one symptom (the a=c[0]] syntax typo from #5), but the underlying _q/_i logic bug remained — flagged again as P1 by Codex review on #6. Fix: replace the whole IIFE with Mixpanel's official snippet verbatim from https://docs.mixpanel.com/docs/tracking-methods/sdks/javascript. The official stub stubs out all methods (track, identify, people.*, ...) and records the init call via b._i.push([...]) — matching the SDK's own contract. Verified by executing the extracted <script> block in Node with a DOM mock: - mixpanel._i receives the init call - mixpanel.track / identify / people.set are all functions - No TypeError, no SyntaxError Same snippet in site/index.html and web/index.html. data-cfasync="false" and the existing mixpanel.init(...) config line are preserved.

Copilot AI review requested due to automatic review settings July 6, 2026 13:57

Copilot started reviewing on behalf of rosuH July 6, 2026 13:58 View session

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rosuH merged commit d32aa63 into main Jul 6, 2026
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rosuH mentioned this pull request Jul 6, 2026

fix(analytics): restore Mixpanel IIFE syntax broken in PR #5 (P1) #6

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fix(analytics): bypass Cloudflare Rocket Loader for Mixpanel snippet#5

fix(analytics): bypass Cloudflare Rocket Loader for Mixpanel snippet#5
rosuH merged 1 commit into
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fix/mixpanel-rocket-loader

rosuH commented Jul 6, 2026

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cloudflare-workers-and-pages Bot commented Jul 6, 2026 •

edited

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rosuH commented Jul 6, 2026

Symptom

Root cause — Cloudflare Rocket Loader

Evidence the rest of the chain is fine

Fix

After merge

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cloudflare-workers-and-pages Bot commented Jul 6, 2026 •

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