Proof Checker: Rigorous Mathematical Verification & Fixing

Systematically verify a mathematical proof via cross-model adversarial review, fix identified gaps, re-review until convergence, and generate a detailed audit report with proof-obligation accounting.

Context: $ARGUMENTS

Constants

• MAX_REVIEW_ROUNDS = 3
• REVIEWER_MODEL = gpt-5.4 via Codex MCP, reasoning effort always xhigh
• REVIEWER_BACKEND = codex — Default: Codex MCP (xhigh). Override with — reviewer: oracle-pro for GPT-5.4 Pro via Oracle MCP. See shared-references/reviewer-routing.md.
• AUDIT_DOC: PROOF_AUDIT.md at the paper directory root, alongside main.tex (cumulative log; when invoked via /paper-writing, this is paper/PROOF_AUDIT.md)
• REPORT_TEX: proof_audit_report.tex (formal before/after PDF)
• STATE_FILE: PROOF_CHECK_STATE.json (for recovery)
• SKELETON_DOC: PROOF_SKELETON.md (micro-claim inventory)

Acceptance Gate (objective, replaces subjective scoring)

The proof passes when ALL of the following hold:

1. Zero open FATAL or CRITICAL issues
2. Every theorem/lemma has: (i) explicit hypotheses, (ii) proof with all interchanges justified, (iii) every application discharges hypotheses in the ledger
3. All big-O/Θ/o statements have declared parameter dependence and uniformity scope
4. Counterexample pass executed on all key lemmas (log candidates even if none found)

Issue Taxonomy (20 categories, 4 groups)

Group A: Logic & Proof Structure

Group B: Analysis & Measure Theory

Group C: Model & Parameter Tracking

Group D: Scope & Claims

Two-Axis Severity System

Axis A — Proof Status (what is wrong)

Axis B — Impact (how much breaks)

Severity Labels (derived)

Side-Condition Checklists for Common Theorems

When the proof invokes any of the following, require explicit verification of ALL listed conditions:

Workflow

Phase 0: Preparation

1. Locate the proof: Find the main .tex file(s).
2. Read the entire proof: Extract list of all theorems/lemmas/propositions/corollaries/definitions/assumptions.
3. Read reference materials: Reference papers, prior results.
4. Build a section map: Structured list with line numbers and key claims.
5. Identify the main theorem: Central result, assumptions, claims.

Phase 0.5: Proof-Obligation Ledger

Build formal accounting artifacts. Save to PROOF_SKELETON.md:

1. Dependency DAG

Nodes = Definitions / Assumptions / Lemmas / Theorems. Edges = "uses". Detect cycles (including semantic circularity where Lemma A uses a corollary that quietly depends on A).

2. Assumption Ledger

For each theorem/lemma, list every hypothesis with WHERE each is verified (or mark "UNVERIFIED"). Track usage-minimal assumption sets — which assumptions were actually used vs merely stated.

3. Typed Symbol Table

Each symbol must have a type signature:

κ : scalar ∈ (0,1), depends on (d, α_t, Σ, μ)
u* : vector ∈ ℝ^d, u* = C^{-1}m
B^even : matrix ∈ ℝ^{(L+1)×(L+1)}, symmetric PSD
Ψ_v : function ℝ → ℝ, analytic in (ζ,κ), parity determined by v

Flag any symbol whose meaning changes or whose type is inconsistent across uses.

4. Canonical Quantified Statements

For each theorem/lemma, rewrite the statement with explicit quantifiers, domains, and limit order:

∀K ≥ 3, ∀π ∈ Π_K^{ms,∘} \ E_K, ∃κ_0 > 0 such that ∀κ ∈ (0, κ_0):
  h_act^{(K,π)} = Θ(κ^{α_K^act})  [uniform in π on compact subsets]

If you cannot restate a theorem this precisely, mark it UNCLEAR — needs disambiguation.

5. Micro-Claim Inventory

Every nontrivial step becomes a numbered micro-claim in sequent form:

MC-17: Context: [Lemma 3.1, κ < κ_0, Z_κ has bounded moments up to order 2m+2]
       ⊢ Goal: P̂_0 is positive definite
       Rule: monomials linearly independent on support of continuous distribution
       Side-conditions: positive density near origin ✓ (by GMM weak convergence)

Each micro-claim has: justification rule name + required conditions + where conditions are proven.

6. Limit-Order Map

Track every asymptotic statement's limit order and uniformity scope:

h_act = Θ(κ^α)  [as κ→0, uniform in π on compact subsets of Π_K, for fixed K]
τ_act ~ (b/a)n   [as n→∞, for fixed κ,K,π with x_K ≪ 1]

Flag any statement where limit order is ambiguous or uniformity is unclear.

Phase 1: First Review (Codex GPT-5.4 xhigh)

Submit the complete proof content with the following mandatory reviewer checklist in the prompt:

mcp__codex__codex:
  config: {"model_reasoning_effort": "xhigh"}
  prompt: |
    You are performing a rigorous mathematical proof review. For EVERY theorem,
    lemma, and proposition, check ALL of the following:

    ## MANDATORY CHECKS

    A. DEFINITIONS: List any symbol whose meaning is ambiguous or changes.
    B. HYPOTHESIS DISCHARGE: For each lemma/theorem APPLICATION (not statement),
       list each hypothesis and whether it was verified, with location.
    C. INEQUALITY AUDIT: For each inequality chain, verify direction, missing
       absolute values, missing conditions (convexity, PSD, integrability).
    D. INTERCHANGE AUDIT: Flag every limit/derivative/expectation/integral
       interchange. State which theorem justifies it (DCT/MCT/Fubini/Leibniz)
       and which conditions are verified/missing.
    E. PROBABILITY MODE: Track whether claims are a.s./in prob./in expectation/
       w.h.p. Ensure transitions are justified.
    F. UNIFORMITY & CONSTANTS: For every O(·), o(·), Θ(·), ≲, state whether
       it is uniform over all parameters. List hidden parameter dependence.
    G. EDGE/DEGENERATE CASES: Attempt to break each key lemma with a 1D,
       low-rank, or extreme-parameter construction.
    H. DEPENDENCY CONSISTENCY: Detect cycles or forward references to unproven
       results.

    ## OUTPUT FORMAT (per issue)
    For each issue found, provide:
    - id: sequential number
    - status: INVALID / UNJUSTIFIED / UNDERSTATED / OVERSTATED / UNCLEAR
    - impact: GLOBAL / LOCAL / COSMETIC
    - category: [from taxonomy]
    - location: section/equation/line
    - statement: what the proof claims
    - why_invalid: why this is wrong or unjustified
    - counterexample: YES (describe) / NO / CANDIDATE (describe attempt)
    - affects: which downstream results break if this is wrong
    - minimal_fix: how to fix it

    [FULL PROOF CONTENT HERE]

Save the threadId. Parse into structured issue list. Write to PROOF_AUDIT.md.

Phase 1.5: Counterexample Red Team

For each CRITICAL or MAJOR issue, and for every key lemma that introduces:

• a new inequality bound
• an identifiability/uniqueness claim
• a curvature/PSD/strong convexity assertion
• a uniform-in-parameter claim
• a convergence mode upgrade (pointwise → uniform, in prob → w.h.p.)

Systematically attempt to construct counterexamples using:

Rule: Label "counterexample found" ONLY if algebraically verified. Otherwise log as "candidate counterexample — needs verification."

Record all attempts (successful or not) in PROOF_AUDIT.md.

Phase 2: Fix Implementation

For each issue, ordered by severity (FATAL → CRITICAL → MAJOR → MINOR):

Step 2a: Choose fix strategy

For each issue, explicitly choose one of:

• ADD_DERIVATION: Write missing proof steps
• STRENGTHEN_ASSUMPTION: Add conditions to theorem statement
• WEAKEN_CLAIM: Reduce conclusion scope
• ADD_REFERENCE: Cite known result + verify its conditions apply

Log this choice — it is a scope-changing decision when it alters theorem statements.

Step 2b: Derive the fix mathematically

• Complete mathematical derivation, not just a claim
• If new proposition/lemma needed, write in full theorem-proof style

Step 2c: Implement in LaTeX

• Edit the .tex file
• Preserve existing \label references where possible

Step 2d: Record the fix

### Fix N: [SHORT TITLE]
**Issue**: [id] [CATEGORY] — [description]
**Severity**: FATAL / CRITICAL / MAJOR / MINOR
**Status**: INVALID / UNJUSTIFIED / UNDERSTATED / OVERSTATED
**Impact**: GLOBAL / LOCAL / COSMETIC
**Fix strategy**: ADD_DERIVATION / STRENGTHEN_ASSUMPTION / WEAKEN_CLAIM / ADD_REFERENCE
**Location**: Section X, Lines Y-Z

**BEFORE**: [what the proof originally did]
**WHY WRONG**: [mathematical problem, with counterexample if applicable]
**AFTER**: [what the fix does]
**KEY EQUATION**: [central new equation]
**PROOF OBLIGATIONS ADDED**: [new conditions/lemmas introduced]
**DOWNSTREAM EFFECTS**: [which results now need re-checking]

Step 2e: Compile check

pdflatex -interaction=nonstopmode <file>.tex 2>&1 | grep -E "Error|Warning|undefined"

Phase 3: Re-Review (Codex GPT-5.4 xhigh)

Use codex-reply with saved threadId. Include fix summaries. Request the same mandatory checklist.

Check acceptance gate. If not met, repeat Phases 2-3 (up to MAX_REVIEW_ROUNDS).

Phase 3.5: Global Closure & Independent Verification

Global closure checks

After all fixes, verify the proof as a whole:

• Statement–conclusion match: Does the proof end with EXACTLY what the theorem claims (quantifiers, constants, uniformity)?
• All obligations discharged: Every node in the obligation DAG is proven or explicitly assumed (and the theorem statement includes it).
• Case analysis coverage: Cases partition the domain AND include boundary/degenerate cases.
• Induction correctness (if applicable): Base case, inductive step, correct use of IH, induction measure strictly decreases.
• WLOG reductions: Each "without loss of generality" spawns a micro-claim proving the reduction is lossless.
• No silent assumption strengthening: Any fix that strengthened assumptions has propagated to the main theorem statement.

Independent second review for FATAL/CRITICAL fixes

For any fix that resolved a FATAL or CRITICAL issue, submit the fixed section alone (without showing the previous critique) to a fresh Codex thread:

mcp__codex__codex:
  config: {"model_reasoning_effort": "xhigh"}
  prompt: |
    Blind review of the following proof section. You have NOT seen any prior
    review or discussion. Check every step for correctness, hidden assumptions,
    illegal interchanges, and counterexamples.
    [FIXED SECTION ONLY]

If the blind reviewer finds new issues, re-enter Phase 2.

Regression proof-audit

After fixes, re-run:

• DAG acyclicity check (no new cycles introduced)
• Counterexample suite on all DOWNSTREAM lemmas of modified results
• Assumption-delta report: what became stronger/weaker due to fixes?

Phase 3.9: Unrecoverable Proof Protocol

If acceptance gate is not met after MAX_REVIEW_ROUNDS, output a Proof Unrecoverable Report:

1. Minimal set of blocking FATAL/CRITICAL issues that could not be resolved
2. Salvage options ranked: (a) weaken claim, (b) strengthen assumptions, (c) add missing lemmas, (d) restructure argument
3. Which parts of the proof are likely still reusable
4. Recommended next steps for the author

Do NOT silently declare success. The report must be honest.

Phase 4: Audit Report Generation

Generate proof_audit_report.tex with:

1. Overview table: All issues with two-axis severity, category, fix strategy, status
2. Before/After logic chain: Red (BEFORE) → Green (AFTER) comparison
3. For each fix: original proof → why wrong → counterexample (if any) → complete derivation → remaining subtleties
4. Proof-obligation diff: What was unverified before, what is verified now
5. Summary: Now proven / still assumed / open problems
6. Colored boxes: BEFORE (red), AFTER (green), WHY WRONG (orange), KEY INSIGHT (blue), WARNING (yellow)

Compile: pdflatex proof_audit_report.tex && pdflatex proof_audit_report.tex

Phase 5: State Persistence

Write PROOF_CHECK_STATE.json:

{
  "status": "completed",
  "rounds": 2,
  "threadId": "...",
  "fatal_fixed": 0,
  "critical_fixed": 3,
  "major_fixed": 2,
  "minor_fixed": 1,
  "counterexamples_found": 1,
  "counterexample_candidates": 2,
  "acceptance_gate": "PASS",
  "timestamp": "..."
}

Key Rules

Mathematical rigor

• Never accept a proof step on faith. "Clearly" / "it follows" / "by standard arguments" are red flags — each must spawn a micro-claim.
• Hypothesis discharge: Every time a lemma is APPLIED, verify EACH of its hypotheses at that point. Use the side-condition checklists above.
• Interchange discipline: Every swap of limit/expectation/derivative/integral must cite a theorem (DCT/MCT/Fubini/Leibniz) and verify its conditions with explicit dominating function or integrability proof.
• Uniformity discipline: Every O(·)/Θ(·) must declare what parameters it is uniform over. "O(1)" that secretly depends on d,n,K is a CONSTANT_DEPENDENCE_HIDDEN issue.
• Quantifier discipline: Check ∀/∃ order. "For sufficiently small κ" must specify: does κ₀ depend on K? On π? On d?
• Counterexample-first: Before trying to fix a gap, first try to break it.
• WLOG prohibition: Every "without loss of generality" must have an explicit micro-claim proving the reduction. No free WLOGs.
• No silent assumption strengthening: Any fix that adds conditions must propagate to the theorem statement.

Cross-model protocol

• Claude analyzes, Codex reviews: Claude reads proof, formulates questions, implements fixes. Codex provides adversarial review.
• Codex reasoning always xhigh: Never downgrade.
• Send full content: Don't summarize — send actual math for line-by-line checking.
• Preserve threadId: Use codex-reply for follow-up rounds.

Fix quality

• Minimal fixes: Fix exactly what's broken, nothing more.
• Full derivation: Every fix includes complete mathematical argument.
• Explicit scope decisions: Each fix is tagged ADD_DERIVATION / STRENGTHEN_ASSUMPTION / WEAKEN_CLAIM / ADD_REFERENCE.
• Compile after each fix: LaTeX must compile cleanly.

Scope honesty

• Don't overclaim: If a fix makes a result conditional, say so.
• Separate "proven" from "assumed": The audit report has an explicit section for this.
• Log open problems: Issues requiring future work are listed, not hidden.

Output Files

Submission Artifact Emission

This skill always writes PROOF_AUDIT.json at the paper directory root (i.e. paper/PROOF_AUDIT.json when invoked from /paper-writing with paper-dir paper/; <your-paper-dir>/PROOF_AUDIT.json when invoked standalone), regardless of caller or whether the paper contains theorems. A paper with no \begin{theorem} / \begin{lemma} / \begin{proof} emits verdict NOT_APPLICABLE; silent skip is forbidden. paper-writing Phase 6 and tools/verify_paper_audits.sh both rely on this artifact existing at <paper-dir>/PROOF_AUDIT.json.

The artifact conforms to the schema in shared-references/assurance-contract.md:

{
  "audit_skill":      "proof-checker",
  "verdict":          "PASS | WARN | FAIL | NOT_APPLICABLE | BLOCKED | ERROR",
  "reason_code":      "all_proofs_complete | minor_gaps | critical_gap | no_theorems | ...",
  "summary":          "One-line human-readable verdict summary.",
  "audited_input_hashes": {
    "main.tex":                 "sha256:...",
    "sections/4.theory.tex":    "sha256:..."
  },
  "trace_path":       ".prism/traces/proof-checker/<date>_run<NN>/",
  "thread_id":        "<codex mcp thread id>",
  "reviewer_model":   "gpt-5.4",
  "reviewer_reasoning": "xhigh",
  "generated_at":     "<UTC ISO-8601>",
  "details": {
    "theorems_audited": <int>,
    "issues": [ { "id": "T1-H3", "severity": "FATAL|CRITICAL|MAJOR|MINOR",
                  "category": "quantifier|domination|...",
                  "location": "sections/4.theory.tex:L182",
                  "note": "..." }, ... ]
  }
}

audited_input_hashes scope

Hash the declared input set actually reviewed — the theorem-bearing .tex files passed into this invocation — not a repo-wide union and not the reviewer's self-reported opened subset. The external verifier rehashes these entries; any mismatch flags STALE.

Path convention (must match tools/verify_paper_audits.sh): keys are paths relative to the paper directory (no paper/ prefix — the verifier resolves relative to the paper dir; prefixing produces paper/paper/... and false-fails as STALE). Use absolute paths for files outside the paper dir.

Verdict decision table

MAJOR issues alone map to WARN or FAIL at the reviewer's discretion and must carry an explicit justification in summary + details.issues.

Thread independence

Every invocation uses a fresh mcp__codex__codex thread. Never codex-reply across proof-checker runs. Do not accept prior audit outputs (PAPER_CLAIM_AUDIT, CITATION_AUDIT, EXPERIMENT_LOG) as input — the fresh thread preserves reviewer independence per shared-references/reviewer-independence.md.

This skill never blocks by itself; paper-writing Phase 6 plus the verifier decide whether the verdict blocks finalization based on the assurance level.

Example Invocations

/proof-checker "neurips_2025.tex"
/proof-checker "check the GMM generalization proof, focus on dimension dependence"
/proof-checker "verify proof in paper.tex — difficulty: nightmare"

Self-calibration

This detector is regression-tested against a labeled gold set so its false-negative rate (flawed proofs passed) stays < 0.15 and false-positive rate (valid proofs wrongly flagged) stays < 0.10.

• Gold examples: evals/gold/proof-checker/*.json
• Run this skill on each example's input, record verdicts to evals/runs/<date>/proof-checker.jsonl, then score:

  python3 tools/audit_calibrate.py \
    --gold-dir evals/gold/proof-checker \
    --predictions evals/runs/<date>/proof-checker.jsonl

• Exit 1 = recalibrate (adjust rigor/flagging here, or fix the blind spot the breached category rows reveal). See evals/README.md for the full loop.
• When this audit misses a real flaw or false-alarms in practice, add that case to the gold set so it never regresses again.