The first message of an agent session is not a command in the same sense as subsequent messages. It is an initialization signal: it sets context, establishes session goals, references past work, defines priorities, and may include meta-commentary about the interaction itself. The current prompt routing specification and the interpret-message skill treat all messages identically, which means the first message either gets routed to a skill it doesn’t fit (command dispatch) or falls through to the full encoding loop when what it actually needs is session initialization.
What first messages do
A first message typically:
- Establishes continuity — references what was done in previous sessions, what state the work is in, what the user has been thinking about since.
- Sets session scope — declares what this session should focus on, what counts as success.
- Provides meta-guidance — how the agent should approach the work (e.g., “use less context for mechanical tasks,” “focus on creative thought”).
- Embeds corrections or priorities — things that should change about how the agent operates, based on the user’s experience since the last session.
Why this matters for context economy
Session initialization is expensive. The agent currently reads CLAUDE.md, the working notes, the TODO, the registry, recent plans, and the relevant specs — all before doing any actual work. Much of this reading is mechanical and repetitive. A dedicated first-message skill can structure this initialization so that the reading is targeted (only read what the session goals require) and the results are summarized efficiently (so the agent’s context window is not consumed by boilerplate).
The goal is not just to interpret the first message but to use it as a key that unlocks only the relevant context, rather than loading everything and hoping the agent filters it.
Source
emsenn identified this gap on 2026-03-07: the system has improved prompt interpretation for individual messages but has no special handling for session-initializing messages, which are structurally different.