A delegate_task child dispatched with an output_schema whose final answer
still violates the schema after the one bounded retry (including the
common empty {} fallback) was reported status="completed" with a ✓ in
the batch report. Since the structured-output feature landed (d6ee58b58),
the result entry does carry schema_valid=false + schema_errors on
failure, but the status logic in _run_single_child only checked for a
non-empty summary and never consulted the validation outcome — so
consumers that read only status (orchestrators, the batch ✓/✗ icon,
subagent lifecycle state mapping) accepted a contract-violating verdict
as success.
Fix: in the status derivation, treat _schema_valid is False as a
failure ("failed"), between the interrupted and summary checks. The
failed entry names the schema violation in its error field instead of
the generic "Subagent did not produce a response.", and schema_errors
keep propagating verbatim. _schema_valid stays None on schema-less
delegations, so their entries remain byte-identical (wire-shape
pinning), and schema_valid=true children are untouched. Covers both
the single-goal and batch paths, which share _run_single_child.
Regression tests: schema-failing final ({} after retry) is failed with
a schema-specific error and the invalid text still in summary; retry-
exception path is failed; schema-valid and schema-less paths pinned
unchanged.
Per-task `output_schema` (JSON Schema object) on task items plus the
top-level single-goal form — a one-time static addition to the tool
schema (never varies per call).
- Child side: the schema is appended to the child's context as an
explicit OUTPUT CONTRACT block before spawn.
- Completion side: the parent validates the child's final answer with
jsonschema; on failure it sends exactly ONE bounded retry turn
carrying the validation errors verbatim (no schema re-paste).
- Result entries gain schema_valid (+ schema_retries, and schema_errors
on final failure) ONLY when a schema was requested; schema-less calls
keep a byte-identical result shape.
- Malformed schemas are rejected loudly at dispatch (coerce_output_schema
meta-validates via jsonschema's validator_for/check_schema).
- New helpers in tools/delegation_output_schema.py: coerce, contract
block, fence/prose-tolerant extraction+validation, retry message.
Pattern from: github/copilot-cli ctx.agent(prompt,{schema}) — PATTERN
ONLY, zero code/prompt text copied (proprietary); proven consumer:
delegate-task-output-patterns skill.
Tests: tests/tools/test_delegate_output_schema.py (24 tests — valid
first try, invalid->retry->valid, invalid twice -> schema_valid false +
errors surfaced, retry-exception degrade, no-schema legacy shape pin,
dispatch rejection, contract plumbing). Delegation suite: 221/221 green.
itskaism