Readers first, writers later. Slab's menubar canonicalises agent_type "aesel" to "easel" wherever a marker or ledger is read, NativeAeselSession takes either, the ledger launch endpoint takes agent "aesel" (and runs ~/.local/bin/aes when it is installed, easel otherwise), and PromptPreview looks for frame requests in .aesel/ before .easel/. prox-mcp takes aesel as an agent, a launch enum value and a prox:aesel: namespace, and sends "easel" on to menubars that predate this. Aesel itself keeps writing "easel" (TODO in slab-session.mjs). The claude-* hooks stand aside for AESEL_SESSION_ID or EASEL_SESSION_ID. lith answers /api/aesel-* from the easel-* function of the same name; the old routes stay. Transcripts parse as aesthetic.aesel/aesel or aesthetic.easel/easel and are still written under the old names. AESEL_TRANSCRIPT_STAFF_SUBS is read before EASEL_TRANSCRIPT_STAFF_SUBS. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>