pullboard-run guide says the engine "refuses only the builder"; engine 90 also refuses any seat under the builder's parent session

What the guide says

skills/pullboard-run/SKILL.md:88: "Start every reviewer outside the builder's root: a fresh session, or a subagent of a different session from the one that started the builder. ... Pullboard itself refuses only the builder (SELF_VERIFY), so the rest is yours to keep."

Step 5 of the same guide has the coordinator start verifier subagents from its own session.

What the engine does

src/machine.js:146 guard notBuilder refuses SELF_VERIFY, VERIFIER_STANDING and SELF_SESSION_VERIFY. Its rule text: the verifier's agent session must not have built or submitted the item under any seat.
src/item-authors.js:25 refuses SELF_SESSION_VERIFY when the verifying seat shares a parent session with any author.
src/item-sessions.js:100 refuses when the agent session itself built or submitted.
src/parent-session.js derives Claude Code identity from CLAUDE_CODE_SESSION_ID alone; an Agent-tool subagent has no id of its own, so every builder and verifier the coordinator spawns shares one parent session.

Observed

Board superagent, 2026-11-04. Coordinator (Claude Code) spawned builder implementation-3 and verifier review-2 as subagents. review-2's pullboard verify 33 accept was refused SELF_SESSION_VERIFY. The refusal's next-step ("ask another agent session to verify it: pullboard next --verify from that session's own worktree") does not say that, under Claude Code, "another agent session" means a separate process the person starts; a subagent of the coordinator is still the same session. The verdict landed only after the person started claude -p in a fresh worktree (review-3).

Proposed fix (agreed design)

1. Generate the guide's independence sentence from the notBuilder row in src/machine.js (its rule and alsoRefuses texts) instead of hand-written prose, with a regression test that fails when the guide and the row diverge.
2. In the Claude Code refusal path, make the SELF_SESSION_VERIFY next-step say: start the verifier as a separate process (new claude session in its own worktree), not an Agent-tool subagent of the coordinator.
3. Keep the engine rule as it is; the stricter rule is right, the guide is wrong.

Related: PR #18 (view health scan session fix), same board.