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bug(subagents): --print/--json parent can settle while required children are still running [under investigation] #512
Description
Status
Wiring landed on research branch research/openpi-cursor-reliability-20260908 @ 7950570 and PR #515. PR is not merged. Isolated evidence only. Not a formal Benchmark.
Impact
In pi --print / --mode json, a parent that calls subagent_spawn and then ends the turn emits agent_settled and the process exits. Automatic result delivery only helps an interactive TUI. Required child results are lost.
Evidence — same E task+acceptor, cursor-grok-4.6-high-fast
Receipts still say source=a3edee28 because the harness hardcoded that SHA. Split is by spawn-result text + attempt window. Index: /tmp/openpi-reliability-20260908/results/e-high-fast-512-version-split.md.
| Window | Product behavior | n | Correct |
|---|---|---|---|
| E-01..10 | stock v0.8.1 spawn (“end your turn” / auto re-invoke). E-06..10 are still this window, not after-fix. | 10 | 7 |
| E-11..20 | print-host spawn from 7950570 (“MUST call subagent_wait”). All 10 stdout traces show that text. |
10 | 10 |
E-01 spawn result (trimmed): “end your turn; its result is delivered automatically and you are automatically re-invoked”. E-11 spawn result: “This host cannot re-invoke you after you end the turn. You MUST call subagent_wait…”
Isolated bun run check exit 0 (results/isolated-bun-check.log) and bun run test exit 0, 1470 pass (results/isolated-bun-test.log).
Fix (on the research branch only)
buildSubagentSpawnResult({ canDeliverLater: false })requires wait and does not say “end your turn”.- On
agent_settled, if the host cannot deliver later and direct children are still running, send up to twofollowUp+triggerTurnbarriers.
Do not disable tools, loosen permissions, or lengthen timeouts.
Applicability
OpenPI v0.8.1 subagent spawn/delivery. Not Cursor native-tool rejection (PR #484). Related hung-after-success: #516.
Activity
tt-a1i commentedon Sep 8, 2026
Isolated worktree now has a failing-repro-first helper plus wiring (not merged):
extensions/subagents/src/print-host.ts— TUI-onlycanDeliverLater, pending follow-up textbuildSubagentSpawnResult({ canDeliverLater: false })requiressubagent_waitand does not say “end your turn”--print/json/rpcparentagent_settledwith running direct children sends up to twofollowUp+triggerTurnbarriersUnit tests:
tests/extensions/subagents/print-host.test.tsand the new prompt contract. Same E task+acceptor has 10 before-samples on v0.8.1 stock spawn text (3 print-settle failures, 7 waits). After-sample revalidation is in progress. No merge/release.tt-a1i commentedon Sep 8, 2026
Before/after on the same E task+acceptor,
cursor-grok-4.6-high-fast, isolated v0.8.1:You MUST call subagent_waitand the model called Pisubagent_wait.PR opened from
research/openpi-cursor-reliability-20260908. Isolatedbun run check+bun run testgreen. Not merged.docs(research): record #512 version split and evidence-gap close