Contract: R76.S2 — Seal-audit staging file

Task: R76.S2 Deliverable: .agents/spawns/r76-phase-0-to-1-bridge/seal-audit.md Governing spec: docs/agents/sigma-orchestrator.md §4 Phase B

1. Behavioral contract

The seal-audit staging file MUST:

Carry YAML frontmatter that Sigma Phase B can write to without re-authoring the file.
Name TBD fields explicitly for every value Sigma produces during Phase B seal.
Enumerate every Wave 1–3 PR with merge commit SHA (already known).
Leave Wave 4 PR numbers and merge SHAs as TBD — both S1 and S2 are in flight during staging.
Reference the manifest via relative link.
Cite CLAUDE.md §7 ordering rule in the writeback chain manifest (thought_record before merkle_finalize).
Reproduce Sigma’s Phase B checklist verbatim from docs/agents/sigma-orchestrator.md §8.
Declare status: staging until Phase B flips it to sealed.

2. Frontmatter schema

---
round: R76                       # Fixed, known now
theme: phase-0-to-1-bridge       # Fixed, known now
phase: B                         # Placeholder phase for Phase B artefact
sigma: claude-opus-4-7-1m        # Who runs Phase B seal (fixed)
pm: claude-opus-4-7-1m           # Who ran T2 promotion (fixed)
parent: ./manifest.md            # Relative link to the landed Phase A artefact
created: 2026-04-19              # Date file was staged (Wave 4 ceremony)
status: staging                  # → flips to "sealed" in Phase B
merkle_root: TBD                 # Sigma fills after merkle_finalize
seal_commit: TBD                 # Sigma fills after round commit
---

Rationale:

created: 2026-04-19 is the Wave 4 ceremony date (a day after Phase 0 seal 2026-04-18 per memory).
status: staging is a load-bearing flag — Sigma flips it last during Phase B.
TBD placeholders are bare tokens (not strings) per gray-matter convention.

3. Section contract (6 sections)

#	Title	Purpose	TBD content?
1	Phase A reference	Link to manifest.md	None — fully known
2	Wave-by-wave PR map	Wave 1/2/3 merged PR rows (9) + Wave 4 staging rows (2) + Phase B seal row (1)	Wave 4 merge SHAs + Phase B artefacts all TBD
3	Writeback chain manifest	13-entry chain statement + ordering rule citation	None — structural
4	Acceptance claims	Checkbox list of 7 items Sigma verifies in Phase B	All unchecked
5	Failures to watch for	Sigma contract §4 failure-mode recap	None — reference
6	Phase B checklist	Verbatim from sigma-orchestrator.md §8	All unchecked

4. Non-goals (explicit)

NOT modifying manifest.md (already merged).
NOT filling merkle_root or seal_commit (Sigma’s job).
NOT filling Wave 4 merge SHAs (both S1 and S2 pending at staging time).
NOT duplicating docs/session-seal-s8.md content (that is R76.S1’s deliverable).
NOT changing src/, any test, or any shipped doc.
NOT adding new tool references or tool calls.

5. Size target

~130–160 lines, aligned with the template in the task prompt.

6. Acceptance tests (for Step 5 verification)

File exists at .agents/spawns/r76-phase-0-to-1-bridge/seal-audit.md.
Line count within [130, 160] inclusive.
YAML frontmatter parses cleanly (no gray-matter errors).
Exactly 4 TBD markers in frontmatter area (merkle_root, seal_commit, plus 2 Wave 4 rows).
Wave 1–3 rows contain all 9 verified merge SHAs.
PR-map table cross-references match §1.3 of this contract.
npm run build && npm run lint && npm test pass on the worktree head (docs-only → expect 1085/1085).

7. Commit shape

Single commit containing:

.agents/spawns/r76-phase-0-to-1-bridge/seal-audit.md (NEW)
docs/audits/r76-s2-round-card-audit.md (NEW)
docs/contracts/r76-s2-round-card-contract.md (NEW — this file)
docs/packets/r76-s2-round-card-packet.md (NEW)
docs/verification/r76-s2-round-card-verification.md (NEW)

No other files touched.