Chain arithmetic audit

Skill lubochka/xiigen-mvp-engine/.agents/skills/chain-arithmetic-audit

Self-building AI code generation engine that generates application flows instead of implementing them. AGPL-3.0.From the repository description

Install

npx -y skills add lubochka/xiigen-mvp-engine --skill chain-arithmetic-audit

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SKILL.md

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Chain Arithmetic Audit Skill

Verifies that baseline + Σ(phase deltas) = final for every tracked metric across all sessions and phases. FC-1 checks single-document consistency; this skill checks end-to-end chain math.

When to Invoke

At FC-1 check time — extends FC-1 from "do documents agree" to "does the math work end-to-end"
At session end when writing Section A — verify "Before" equals the previous session's "After"
Any time a plan spans multiple sessions or phases with incremental counts

Rules

Extract all count references from STATE.json, REFERENCE-PLAN, and every SESSION file
Build directed graph: baseline → S1 delta → S2 delta → ... → final
Verify every edge: node[n].after == node[n+1].before
Verify terminal: baseline + Σ(all deltas) == final_expected
Any gap or mismatch = FC-1 FAIL with exact location and value

Detection

# Extract all count transitions
grep -n "before\|after\|delta\|expected\|baseline\|tests_after\|spec_files_after" STATE.json

# For each session A → B: verify A.after == B.before
# Example chain for XIIGen test coverage plan:
# 2365 (Phase 11) → +18 (S1) = 2383 → +10 (S3) = 2393 → +N (S4) = final

Verification Table Format

Transition	Before	Delta	After	Verified
Phase 11 → S1	2365	+18	2383	✅
S1 → S2	2383	+0 (server)	2383	✅
S2 → S3	2383	+10	2393	✅
S3 → S4	2393	+N	2393+N	TBD

Anti-Pattern

Plan 1 said final_expected_counts: 103 but phase totals summed to 105. FC-1 passed (individual documents agreed). Chain arithmetic failed. This skill catches what FC-1 misses.

Integration

Extends plan-review-skill FC-1
Invoked by infrastructure-discovery Gate 0 Step 3
Results feed into Section A "zero-regression delta" at session end

What ships with it

Read from the repository

Just SKILL.md. No reference files, no scripts.