retrospective

# Retrospective Run after every completed **cycle**: a solution leaf reaching a terminal state (launched, archived, killed), or a framework-development arc that shipped. Not only after a diamond completes — a diamond at L0 to L2 can stay open for months while cycles close under it weekly. Measured on the dogfood repo (2026-08-30): 17 cycles in 116 days, median 3.5 days apart, while every diamond stayed open the whole time; the earlier wording ("after every completed delivery diamond or significant milestone") named two units forty times apart and the load-bearing one was the vague one. Source: Forsgren (learning culture). ## Preflight: Read target canvas file(s) before any Write/Edit **Hard rule.** Before issuing `Write` or `Edit` against any `.claude/canvas/*.yml`, use the **Read tool** on that file in this session. Claude Code's Read-before-Write check requires the `Read` tool specifically — `cat`/`head`/`grep` via Bash do NOT satisfy it. **Edit vs Write — different cost profiles** (verified 2026-05-14): - **`Edit`** (exact-string replacement): `Read` with `limit: 1` satisfies the check at ~50 tokens. State-tracking is per-file, not per-byte — subsequent `Edit` calls work anywhere in the file. Use this for partial updates against large canvas files (e.g., `purpose.yml` at 800+ lines). - **`Write`** (full replacement): do a **full Read** first. Write obliterates the file; you should see what you're about to replace. The `limit:1` shortcut is *not* appropriate here. **ID...