Writing
One problem per post, the fix stated in the first paragraph, then how it works and when it isn't worth doing. No newsletter, no popups.
String diffs don't work on free-text output. Freeze the traces, assert on behaviour instead of text, and run the suite after every prompt or model change.
Charge after the stream using the provider's real token counts, and let a unique key on the ledger reject Stripe's duplicate webhooks.