Files
PaperClipAI/server
Devin Foley ddbcf53e31 fix(server): refuse agent delegation cycles back to an open ancestor's creator (#10658)
## Thinking Path

> - Paperclip is the open source app people use to manage AI agents for
work
> - Agents decompose work by creating child issues assigned to other
agents
> - When two agents each lack a capability the other assumed (e.g.
neither can push to GitHub), each can "resolve" its blocker by
delegating the same step to the other: A creates a child for B, B
creates a grandchild back for A
> - Nothing detects the cycle; the chain of blocked issues grows and no
signal reaches the human who could actually fix the capability gap
> - This pull request refuses agent-initiated child creation when the
child's assignee is the creator of a still-open ancestor in the same
chain — a mechanical, semantics-free cycle signal
> - The benefit is that the hot-potato dies at creation time with an
actionable error instead of growing a dead chain

## Linked Issues or Issue Description

Fixes #10642 (write-time counterpart: #10648 refuses assignment to
paused agents; the credential-gap *preflight* side is tracked separately
in #10644)

## What Changed

- `issueService.findOpenAncestorCreatedByAgent(parentIssueId, agentId,
{maxDepth})`: bounded walk up the parent chain looking for a still-open
(not done/cancelled) ancestor created by the given agent.
- Agent-initiated issue creation with a parent (both the
create-with-`parentId` route and `POST /issues/:id/children`) now
refuses with a structured 409 (`code: delegation_cycle`, naming the
ancestor) when the new child would be assigned to the agent that created
a still-open ancestor: that agent delegated the work into this chain, so
assigning it back is a cycle. The message states the alternatives —
complete the work, leave the child unassigned, or escalate to a board
operator.
- Deliberately unaffected: human actors (deliberate re-routing is their
call), closed ancestors (re-engaging the creator of finished work is
normal), and accepted-plan decomposition (its children come from a
human-approved plan).

## Verification

- `pnpm vitest run
server/src/__tests__/issue-assignee-invokability-routes.test.ts` — cycle
refused with 409 and no create call; the same child allowed when no open
ancestor matches; board actors never consult the guard.
- `pnpm vitest run server/src/__tests__/issues-service.test.ts` — new
embedded-Postgres coverage: ancestor found through the chain, closed
ancestors ignored, depth bound honored (114 total).
- `pnpm vitest run
server/src/__tests__/issue-create-deduplication-routes.test.ts
server/src/__tests__/issue-agent-mutation-ownership-routes.test.ts` —
unchanged (79).
- `cd server && pnpm run typecheck`.

## Risks

- Low-to-moderate: a new 409 for a creation shape that previously
succeeded. The blocked shape (agent assigns new work to the creator of
an open ancestor) is the cycle signature; the legitimate "hand a subtask
to the parent's assignee" pattern is unaffected because it keys on
assignee, not creator. Watchdog and plan-decomposition flows are exempt
or unaffected as described.
- The walk adds at most `maxDepth` (10) single-row lookups per agent
child creation with an assignee.

## Model Used

Claude Fable 5 (`claude-fable-5`, Anthropic) via Claude Code — extended
thinking, agentic tool use. No other models involved.

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have searched GitHub for duplicate or related PRs and linked
them above
- [x] I have either (a) linked existing issues with `Fixes: #` / `Closes
#` / `Refs #` OR (b) described the issue in-PR following the relevant
issue template
- [x] I have not referenced internal/instance-local Paperclip issues or
links (only public GitHub `#NNN` / `github.com/paperclipai/paperclip`
URLs)
- [x] My branch name describes the change (e.g. `docs/...`, `fix/...`)
and contains no internal Paperclip ticket id or instance-derived details
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [ ] All Paperclip CI gates are green
- [ ] Greptile is 5/5 with no open P2s, recommendations, or follow-ups
- [x] I will address all Greptile and reviewer comments before
requesting merge
2026-08-01 17:43:09 -07:00
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