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Every channel that shows a typing indicator (the open channel, and each Solo row on the home list) subscribes for typing and message events with `limit: 10` and no `since`, so each subscribe replays that channel's last 10 stored messages. The handler then ignores every one of them that is older than the 8 second typing window, so the replay only costs bytes. On an iPhone 12 mini signed in to Builderlab, seven Solo rows made this about 66 KB of kind 9 messages on each cold start, and again on each resubscribe. The subscription now asks only for events inside the typing window (`since` = now minus 8 s), which are the only ones the handler can act on. ### Validation New test: the typing subscription asks for history starting 8 s before it subscribes. It fails without this change. Full mobile test suite and `flutter analyze` pass. On the iPhone 12 mini (profile build with this change, signed in to Builderlab), stored and live events on the typing subscriptions in the first minute or more after a cold start: | | Subscriptions | Kind 9 messages | Typing events | | --- | --- | --- | --- | | Before (60 s) | 7 | 74 (66.6 KB) | 26 (15.6 KB) | | After (80 s) | 8 | 2 (1.5 KB) | 29 (17.8 KB) | Typing events are mostly live ones from agents working in Solo chats, so they stay about the same. The automated run covered a cold start to the home list and its Solo rows. ### Regressions - A device clock running more than 8 s fast can make the relay skip a message that would have ended an indicator. That indicator still clears when its 8 s window ends, and the handler already drops events it considers older than the window, so the same skew loses the same events today. Signed-off-by: Tom Brow <tomb@squareup.com> Co-authored-by: Tom Brow <tomb@squareup.com> Co-authored-by: studio <dc2fc481343672df31a689840c09299972e704dac592e0da6f18486646a7ee3e@buzz.block.builderlab.xyz>