Claims AFTER all subagent children resolve — by then Lane 1B's queue
changes have posted one child_done message per terminal transition into
this job's inbox (complete / failed / dead / cancelled / timeout). The
aggregator reads those, builds a deterministic markdown summary, and
returns it as the handler result.
Not an LLM call in v0.15 — output is reproducible concatenation so
fan-out runs stay comparable. v0.16+ can add an LLM synthesis pass
behind an opt-in flag.
Contract:
- empty children_ids → `(no children)` marker
- missing child_done (shouldn't happen under v0.15 invariants but
possible if a terminal-state path slipped past Lane 1B) → counted as
failed with "no child_done message observed" error
- non-complete outcomes: result is null in the output so no payload
leaks alongside a failure label
- children appear in the order children_ids was supplied
- custom aggregate_prompt_template replaces the markdown header
13 unit tests cover: empty input, all-success, mixed outcomes, result
suppression on failure, missing child_done handling, order preservation,
custom template, progress + log emission, stringified JSONB payload
parsing, non-child_done inbox filtering, legacy-writer outcome fallback,
and internal helper edges.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
