💸 Perf - AI for Business Leaders event page - LCP 9.3s, TBT 1,250ms on mobile

Pain

Mobile Lighthouse 13.4 on https://www.ssw.com.au/events/ai-for-business-leaders (Moto G Power, Slow 4G, 23 Jul 2026) is poor:

Accessibility is 81. Total page weight 2,867 KiB. Lighthouse also flags: unused JS 1,064 KiB, JS execution 2.9 s, main-thread work 3.9 s, 17 long tasks, forced reflow, inefficient cache lifetimes (246 KiB), legacy JavaScript (41 KiB).

TL;DR of the root causes

The page itself is simple — 39 blocks of only 6 component types (20 × spacer, 8 × imageTextBlock, 4 × cardCarousel, 2 × accordionBlock, 1 × logoCarousel, 1 × breadcrumbs). The cost is almost entirely framework and shared-component overhead, not content:

1. 1.1 MB of TinaCMS's MDX parser ships in the initial bundle of every page. From .next/app-build-manifest.json, this route's entry is 1.70 MB of JS, and dd3583a7-*.js alone is 1,115 KB of it. 65 components import TinaMarkdown from tinacms/dist/rich-text, whose first line is import { sanitizeUrl } from "@tinacms/mdx" — a 1.97 MB package (remark/mdast/slate/acorn) pulled in for one URL sanitiser. This accounts for essentially all of Lighthouse's "unused JavaScript — 1,064 KiB".
2. The LCP image is lazy-loaded. blocks-renderer.tsx grants priority to block 0, which is breadcrumbs (no image). The hero is block 2 and gets loading="lazy" with no fetchpriority. The file is only 78 KB — 9.3 s is entirely "requested late, behind 1.7 MB of JS".
3. Every one of the 39 blocks pays for V2ComponentWrapper — a getBoundingClientRect() in a mount effect, its own resize listener, a framer-motion useInView observer, and an inline background-image: url("") / url(undefined). 20 of those 39 blocks are empty 45 px spacers.
4. Site-wide passengers: AOS initialises on every page (unused on this one), Application Insights constructs during the critical window, minimumCacheTTL: 60 makes optimised images near-uncacheable, and 8 Eventbrite CTAs each mount an always-live react-responsive-modal.
5. CLS 0.133 is the header — it SSRs with the flag and Contact button, then useMobileHeaderAppearance strips them after hydration. header-appearance.tsx documents this and its fix.

Order of work

Items are sequenced by impact-per-risk, and grouped so PRs touching the same files land together.

Re-run Lighthouse after wave 1 and again after wave 2 — waves 3 and 4 should be measured against the improved baseline, not this one.

Acceptance criteria

1. All 13 sub-issues are closed or explicitly deferred with a reason
2. Mobile Lighthouse on /events/ai-for-business-leaders shows LCP under 2.5 s and TBT under 200 ms
3. CLS is under 0.1
4. The route's initial JS (per app-build-manifest.json) is under 700 KB uncompressed
5. Accessibility score is 95 or above
6. Before/after Lighthouse runs are attached to this issue

Notes

• Findings are from a static read of the codebase plus the committed .next build (22 Jul 15:27), cross-checked against the Lighthouse run. The accessibility items in #4907 are code-inferred — run axe on the page to confirm the full list before starting.
• Every fix below is shared infrastructure: this page is the worst case, but wins apply to all eventsv2, consultingv2 and v3 pages.

Related

• #4889 — the equivalent homepage PageSpeed PBI, with sub-issues #4890–#4893. Several findings there apply site-wide.
• #4892 overlaps with #4896 but blames a different import chain: 9 schema files value-importing the full tinacms package for admin form helpers. That is a real and separate cause — both need fixing. Note also that #4892 states these chunks don't appear in the route's static manifest; for the events route, dd3583a7 is in app-build-manifest.json, so it is not only arriving via dynamic(). Whoever picks up #4896 should read #4892 first and the two should probably be done together.

Treat this as an umbrella performance investigation rather than a single edit. Read blocks-renderer.tsx, header-appearance.tsx, and the route entry in .next/app-build-manifest.json, then review sub-issues #4895–#4907 and related #4892. Done means the sub-issues are resolved or deferred with reasons and the specified Lighthouse, bundle-size, CLS, and accessibility targets are measured and documented.