${var} — Selects the digest's topic and which source classes feed it. Grammar:

"" (empty) → digest's default sources (WebSearch + xAI/Grok + aggregators), no topic filter — a broad daily digest.

"<topic>" → topic-focused digest on the default web sources, filtered to <topic> (e.g. "solana", "AI agents", "rust").

"rss" → RSS-only: pull feeds from memory/feeds.yml, no topic filter.

"rss: <topic>" → RSS-only, filtered to <topic> (e.g. "rss: rust").

"<topic> +rss" → default web sources and RSS feeds combined, both filtered to <topic> (e.g. "AI agents +rss").

Today is ${today}. Generate and send a daily ${var} digest.

The whole point of a digest is signal, not volume. A reader skimming for 60 seconds should walk away with three things they didn't know that morning and one of them should change a decision they'd make this week. Anything that doesn't clear that bar gets cut.

digest

Preamble — orient and parse the selector