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## Summary Improve scrolling performance in the Messages channel list by building Solo and Team rows only as needed. Sections currently mount all their rows as one scroll item, which causes long UI stalls with large channel lists. In manual iPhone runs with 500 channels, maximum observed Flutter UI work fell from **65.5 ms to 4.2 ms** after adding lazy rows to a build with header isolation (#9400). The tester reported much smoother scrolling. This was an exploratory comparison with different gestures, not a controlled benchmark of this independent branch. Use stable channel keys and retain section controls, sorting, and collapse animations. Clip the sliver extent during collapse so the animation does not mount the entire section. The shared transition supports downward vertical lists. This is an independent production-only change. Test fixtures and diagnostic instrumentation are excluded; regression checks were run locally and are not included in this PR. ### Related issue Related: #5911 addresses scrolling behavior inside conversations. This change addresses eager row mounting in the Messages channel inventory. No matching open PR or issue was identified in the focused duplicate search. ### Testing On a physical iPhone with 500 channels against an isolated local relay, maximum Flutter UI work fell from 65.5 ms to 4.2 ms after adding lazy rows to a build that already isolated header rebuilds. The tester reported much smoother scrolling. Gestures differed between runs, so this is not a controlled benchmark or an isolated measurement of this branch on its own. The device run preceded the refresh onto current main. Local-only regression journeys passed 12 tests on this independent branch. They cover page laziness and updates, variable-height rows, large text, the last row, collapse reversal, reduced motion, and semantics. These checks are excluded from the commit. Smaller visible jumps remain under investigation; this PR does not claim to resolve them. Generated with Codex --------- Signed-off-by: Michael Fransen <mfransen@squareup.com> Signed-off-by: Tom Brow <tomb@squareup.com> Co-authored-by: Karl <9e8471f7b792e46c9c100840959dc71c660786c79c2a3165dbcaf58f52c4266e@buzz.block.builderlab.xyz> Co-authored-by: Tom Brow <tomb@block.xyz> Co-authored-by: Tom Brow <tomb@squareup.com> Co-authored-by: studio <dc2fc481343672df31a689840c09299972e704dac592e0da6f18486646a7ee3e@buzz.block.builderlab.xyz>