An investigation reported that under PostgreSQL `updateTask(id, { steps: [] })`
silently no-ops while a non-empty array writes fine, and worked around it in
fixtures. Reproduced and traced: the write is literal and correct — the row and
task.json both hold `[]`. What actually happens is that an empty array means
"plan not parsed yet", not "this task has no steps", so all four read paths
re-derive steps from PROMPT.md when the stored array is empty: getTaskImpl, the
two list hydrations (reads.ts), and updateStep's auto-init, whose range error
already says outright that "its steps are defined in PROMPT.md".
No product change: removing the re-derivation would strand every task whose plan
lives only in PROMPT.md. Instead both halves of the contract are now pinned by a
PG test and documented at the write site, so the next reader sees the mechanism
instead of re-diagnosing it as a lost write. To make a task genuinely stepless,
remove the step headings from PROMPT.md.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
3533fc8a47