agentic-design-session

# Design session You are settling **how**, and recording it so it survives. The main output is `.claude/features/<slug>/decisions.md`, from `.claude/pipeline/decision-log.template.md`. Read the charter first. You also close by filling one section of the charter — `Size and sessions` — and that is the only edit you may make outside the decision log. It is the last step of this skill, described at the bottom. ## Why the rejected alternatives matter more than the decisions An orchestrator will re-encounter every fork you settle here when it writes specs, weeks of context later. Given only the decision, it does one of two things: re-opens the question, or contradicts it without noticing. Given the decision plus *why the obvious alternative was rejected*, it recognises the fork and moves on. So a `Rejected` bullet with no reason is worth nothing. "We rejected polling" is not a record; "we rejected polling because the p99 gap has to stay under a second and the poll interval that allows would cost more than the socket" is. The same applies when you turn out to be wrong. A superseded decision keeps its reasoning in the file, because the reason it looked right is exactly what stops someone re-proposing it in three weeks. ## Hard rules - **Write no code.** Types, signatures and schemas are decisions, and you may quote a signature in a decision. You may not implement one. - **Edit no file but the decision log**, and the charter's `Size and sessions` section at the close. Not...