# Model Research Report: AI Models for Analytical Work

> **Generated:** 2026-05-11 09:00 PDT  
> **Findings analyzed:** 74  
> **Period:** 2026-04-26 to 2026-05-11

_74 experiments across 16 days. Six models tested on architecture document analysis — not coding._

---

## What's New (Since May 6)

**45 new findings** (29 → 74) covering:

- **New task types validated:** Operational blind spot analysis (#46), emergent behavior from rule composition (#47), defense-in-depth gaps (#48), adversarial evasion/tampering (#49), concurrency race conditions (#50), implementation ambiguity (#51), degraded mode propagation (#52), unstated constraints (#53), state reconstruction correctness (#55), operational burden (#56), event flow correctness (#57), state machine completeness (#58), convention-rule gaps (#59), counterfactual event ordering (#60), regulatory completeness (#61), data integrity signal flow (#62), external system assumptions (#63), specification gaps (#64), temporal correctness (#65), concurrent write hazards (#65b), cross-context contract coherence (#68), boundary contract analysis, boundary violation analysis, inter-document contradiction analysis, security boundary analysis, audit log data integrity (#11-May), wash sale regulatory compliance (#11-May)
- **Cross-document consistency expanded** (#37, #44): Opus confirmed as dominant for subtle contradictions across tightly-coupled docs
- **Regulatory compliance analysis depth** (#38, #54, #61): GPT-5 excels at IRS/regulatory specificity with correct citations
- **Narrow framing tested and rejected** (#39, #43): Sonnet cannot match GPT-5/Opus via prompt framing alone — reasoning depth is the bottleneck
- **Adversarial ensemble validated** (#35): Critique-then-extend produces 30% more findings at 28% more cost
- **Operational burden as distinct lens** (#45, #56): Models diverge on what constitutes "operator cognitive load"
- **Silent data corruption paths** (#40): GPT-5 excels at tracing multi-step corruption through financial accounting
- **Temporal ordering dependencies** (#41): All models catch obvious ordering; GPT-5 unique on subtle cascades
- **Failure propagation chains** (#42): Opus finds the architectural insight; GPT-5 finds the enumeration

---

## Executive Summary

We tested GPT-5, Claude Opus, Claude Sonnet 4.6, Claude Sonnet 4.5, GPT-4.1, and GPT-4.1 Mini on analytical tasks: finding hidden assumptions, race conditions, design contradictions, adversarial attack paths, regulatory gaps, cross-document inconsistencies, operational blind spots, emergent behaviors, and security boundaries in real architecture documents.

**The central finding:** Different models don't just find more or fewer things — they find *qualitatively different kinds* of things. Model choice is task-dependent, and no single model dominates all analytical work.

**The secondary finding:** Task type predicts model performance better than "model X is better." A model that excels at gap-finding may struggle at contradiction detection. Match the model to the task.

---

## Part 1: What Each Model Is Good At

### GPT-5

**Strength:** Exhaustive enumeration + domain-specific reasoning about the real world.

GPT-5's reasoning tokens change the *kind* of analysis, not just the depth. Non-reasoning models identify risks within a document's own frame of reference. GPT-5 reasons about the document's relationship to the external world: broker semantics, deployment topology, OTP runtime behavior under load, timing correlations across independent subsystems, IRS regulatory requirements.

| Capability | Evidence |
|------------|----------|
| Domain-specific gaps | #9, #31: Broker rate limiting, credential rotation, corporate actions |
| Multi-component interactions | #10, #14: Finds assumptions requiring cross-boundary reasoning |
| Adversarial enumeration | #29, #35: Most thorough attack surface coverage |
| Temporal boundary analysis | #18: 15 findings with mathematical precision |
| Regulatory compliance | #23, #38, #54: Correct IRS citations, regulatory edge cases |
| Silent data corruption | #40: Traces multi-step corruption paths |
| Invariant violation paths | #20: Precise, verifiable paths through state space |
| Operational blind spots | #46: 18 findings including cross-service trace gaps |

- Best at: gap-finding, hidden assumptions, adversarial enumeration, temporal boundary analysis, regulatory compliance, operational blind spots
- Unique ability: finds multi-component interaction failures requiring domain knowledge
- Weakness: slow (2-4x longer than Opus), expensive (5-10x more tokens per finding), sometimes over-enumerates
- Finding count: typically 15-35 depending on document complexity

### Claude Opus

**Strength:** Design tensions, logical argumentation, creative adversarial thinking, cross-document consistency.

Opus consistently identifies where one part of a design undermines another part. It doesn't enumerate failure modes — it finds the deeper question of *why* the design's own principles conflict.

| Capability | Evidence |
|------------|----------|
| Contradiction detection | #25, #43: Finds logical impossibilities via deductive reasoning |
| Cross-document consistency | #28, #37, #44: 2.4x faster than GPT-5, finds more issues |
| Race conditions (design-level) | #13: 10 high-quality findings, self-corrects mid-analysis |
| Adversarial creativity | #29, #35: "Your safety mechanism IS your vulnerability" patterns |
| False assumption detection | #31, #32: Finds where spec's own logic contradicts itself |
| Emergent behavior insight | #47: Stop-loss defeated by temporal composition (best single finding) |
| Survivor bias identification | #46: Decision latency histogram hides stuck decisions |

- Best at: contradiction detection, cross-document consistency, race conditions (design-level), adversarial creativity, finding false assumptions
- Unique ability: self-corrects mid-analysis, finds where protection mechanisms become vulnerabilities
- Most efficient model: 6-9x fewer tokens per finding than GPT-5 on shared task types
- Weakness: produces fewer findings on pure enumeration tasks (10-13 vs GPT-5's 20-35)

### Claude Sonnet 4.6

**Strength:** Speed, structural issues, assumption-finding. Best precision-per-dollar.

| Capability | Evidence |
|------------|----------|
| Quick first-pass screening | #9, #12: 2-3x faster than other models |
| Structural review | #5: Catches formatting, broken links, missing sections |
| Specification gap identification | #16: 13 findings, zero false positives |
| Observability gaps | #33: 11 findings in 36s |

- Best at: quick first-pass screening, structural review, specification gap identification
- Zero false positives on most tasks — every finding is actionable
- Weakness: struggles with concurrency reasoning, contradiction detection, tasks requiring formal logical reasoning
- Produces false positives on verification-heavy tasks (contradiction, race conditions)

**Critical limitation (Finding #39):** Narrow framing does NOT close the gap with GPT-5/Opus. Sonnet can find 3 contradictions but only 1 is genuine (2 are misreadings). The gap is reasoning depth, not framing — Sonnet can't reliably verify whether two statements actually contradict each other.

### Claude Sonnet 4.5

**Strength:** Exhaustive coverage. More findings than 4.6, at the cost of some noise.

| Capability | Evidence |
|------------|----------|
| Specification completeness | #16: 25 findings vs 4.6's 13 |
| Temporal reasoning | #18: 12 findings with no errors (vs 4.6's errors in #13) |
| Operational gaps | Catches gaps that 4.6 filters out |

- Best at: specification completeness, broad coverage
- Tradeoff: severity inflation, more verbose output
- Use 4.5 for coverage, 4.6 for precision

### GPT-4.1

**Strength:** Structured, thorough, good middle ground. Generic but competent.

| Capability | Evidence |
|------------|----------|
| Stays within document framing | #9, #10: Finds assumptions the document almost states |
| Meta-observations | #10: "All failure modes treated as isolated" |
| Cost-effective first pass | Good enough when GPT-5's cost isn't justified |

- Best unique contribution: meta-observations about design structure
- Good enough for first-pass review where GPT-5's cost isn't justified

### GPT-4.1 Mini

**Strength:** Cheapest. Formulaic but catches the obvious things.

| Capability | Evidence |
|------------|----------|
| Scales with document size | #9, #19: 6 findings on 459 lines → 21 on 1,110 lines |
| Clean templates | Every finding maps to a document section |
| Bias detection | #8: Catches bias when signal isn't buried |

- Fine for quick sanity checks, not for architectural insight
- Best for: bulk screening, sanity checks, obvious-issue detection

---

## Part 2: Task Type → Model Mapping

Not all analytical tasks are the same. Models that excel at one struggle at another.

| Task Type | Best Model | Runner-up | Avoid | Evidence |
|-----------|-----------|-----------|-------|----------|
| **Gap-finding** | GPT-5 | GPT-4.1 | Mini (surface-level) | #9, #31, #64 |
| **Hidden assumptions** | GPT-5 | Opus | Mini (formulaic) | #10, #11, #12, #53 |
| **Race conditions** | GPT-5 + Opus | — | Sonnet (errors) | #13, #50 |
| **Contradiction detection** | **Opus** | GPT-5 | Sonnet (false positives) | #25, #43 |
| **Cross-document consistency** | **Opus** | GPT-5 | — | #28, #37, #44 |
| **Adversarial attack paths** | GPT-5 (enum) + Opus (creativity) | — | — | #29, #35, #49 |
| **Design coherence** | Document-dependent | — | — | #15, #27 |
| **Specification completeness** | Sonnet 4.5 (breadth) / GPT-5 (self-contradictions) | — | — | #16, #31 |
| **Regulatory compliance** | GPT-5 | Sonnet (first-pass) | — | #23, #38, #54 |
| **Operational blind spots** | GPT-5 | Opus | Sonnet | #46 |
| **Emergent behavior** | GPT-5 (feedback loops) | Opus (best single insight) | — | #47 |
| **Temporal boundaries** | GPT-5 | Opus | — | #18, #41, #65 |
| **State machine completeness** | GPT-5 | Opus | — | #58 |
| **Silent data corruption** | GPT-5 | — | — | #40, #62 |
| **Defense-in-depth gaps** | GPT-5 + Opus | — | — | #48 |
| **Security boundaries** | GPT-5 | Opus | — | #10-May |

**Key pattern:** Tasks requiring *identification* (what's missing? what's assumed?) are accessible to all models. Tasks requiring *verification* (is this sequence legal? does this contradict that?) favor reasoning models (GPT-5, Opus) and exclude Sonnet.

**Task category taxonomy:**

| Category | Sonnet value | Best models |
|----------|--------------|-------------|
| Systematic/exhaustive | None | GPT-5, Opus |
| Creative/generative | Meta-analytical synthesis | Opus, GPT-5 |
| Compliance/regulatory | Adequate but shallow | GPT-5 (deep), Sonnet (first-pass) |
| Cross-document | None | Opus strongly preferred |

---

## Part 3: Meta-Findings About How to Use Models

### 1. Signal-to-noise ratio matters more than model capability (#8)

When biased text is the ONLY input, even GPT-4.1 Mini catches it. When the same bias is buried inside a full PR review with diffs, issues, and project context, expensive models miss it. The issue isn't model intelligence — it's attention dilution.

**Implication:** For important analytical checks, isolate the signal. Extract the relevant text and ask about it specifically. Don't bury important questions inside broad review mandates.

### 2. Prompt framing dominates model personality for OPEN tasks (#26)

Opus's "finds design tensions" and GPT-5's "exhaustive enumeration" are DEFAULT tendencies, not hard limits. With structured prompts that explicitly ask for breadth, Opus produces MORE findings than GPT-5. With structured prompts asking for contradictions, GPT-5 becomes highly selective.

**Implication:** Model choice matters less than you think for any single task. Prompt structure is the primary lever. Model personality matters for open-ended tasks where you want emergent analytical behavior.

### 3. Narrow framing does NOT fix Sonnet's reasoning gaps (#39, #43)

Sonnet can't match GPT-5/Opus via narrow prompts alone. Narrow framing changes WHAT Sonnet looks for but not HOW WELL it reasons. Sonnet found 3 contradictions but only 1 was genuine (2 were misreadings). The gap is reasoning depth, not prompt engineering.

### 4. Task type predicts model performance better than "model X is better" (#13)

Sonnet scores 85% of GPT-5's performance on assumption-finding but drops to ~50% on concurrency reasoning. Don't extrapolate across task types.

### 5. The union of models finds the most (#19)

GPT-5 Mini + Sonnet covers ~71% of GPT-5's findings at 31% of the cost. But the missing 29% contains the domain-specific interaction-level findings most likely to prevent production incidents. Each model also finds things the others miss — the total unique finding space is larger than any single model's output.

### 6. Adversarial ensemble produces 30% more findings (#35)

Run GPT-5 for exhaustive enumeration, then give Opus GPT-5's findings and ask it to critique and extend. Result: 56 findings vs 43 (GPT-5 alone) or 28 (Opus alone). Zero full disagreements. The critique's structured assessment is more valuable than raw extensions. Cost: ~28% more tokens for 30% more coverage + prioritization.

### 7. Reasoning tokens change the KIND of analysis, not just the amount (#10)

Non-reasoning models ask "what could this mechanism fail at?" Reasoning models ask "what must be true about the world for this mechanism to work?" This is a qualitative difference in analytical mode, not just thoroughness.

### 8. Reasoning effort parameter is a no-op for analytical work (#21)

Low/medium/high reasoning effort had negligible effect on GPT-5's output for open-ended analysis. Task type is a far stronger predictor of reasoning behavior. Don't waste time tuning this parameter for document review.

### 9. Output length kills, input length doesn't (#6)

Single agents die trying to generate 1000+ line documents. Rich input context is fine — it's the output length that causes OOM/timeout. Break output into sections, keep input context rich, draft in parallel, assemble.

### 10. Document complexity shifts model rankings (#27)

Opus beat GPT-5 on coherence analysis for one document but lost on another (more complex) document. Rankings are not universal — they interact with document complexity, domain specificity, and prompt structure.

### 11. Token budget matters more than model size (#7b)

When output is truncated by token limits, even GPT-5 produces shallow findings. Ensure sufficient max_completion_tokens (≥16K for GPT-5). A cheap model with enough tokens beats an expensive model that runs out of space.

### 12. Opus excels at finding where specs believe false things (#31, #32)

Across experiments, Opus consistently finds where the spec's OWN ASSUMPTIONS are false. GPT-5 reasons about what the spec FAILS TO SAY. Opus reasons about what the spec BELIEVES to be true and checks whether those beliefs hold. Different but complementary.

### 13. GPT-5's reasoning tokens are spent on VERIFICATION for regulatory tasks (#54)

For domain-specific regulatory analysis (IRS wash sale rules), GPT-5 consistently cited correct publication sections, code numbers, and regulatory references. The 9,600 reasoning tokens appear spent on verification, not generation.

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## Part 4: Cost-Effectiveness

| Model | Typical tokens/finding | Relative cost | Best use case |
|-------|----------------------|---------------|---------------|
| Opus | 179-336 | 1x (baseline) | Cross-doc consistency, contradictions, design tensions |
| Sonnet 4.6 | 111-194 | 0.2-0.3x | Quick screening, structural review, assumption-finding |
| Sonnet 4.5 | 150-250 | 0.25x | Broad coverage when noise is acceptable |
| GPT-5 | 511-2,967 | 5-9x | High-stakes analysis where missing something has real cost |
| GPT-4.1 | ~500 | 0.5x | Middle-ground first pass |
| GPT-4.1 Mini | ~300 | 0.1x | Bulk screening, sanity checks |

**For financial/safety-critical systems:** Run all three (Opus + GPT-5 + Sonnet). The ~$1-2 total cost per document is trivially justified vs the value of comprehensive coverage.

**For routine review:** Opus alone or Sonnet + Opus pair. Skip GPT-5 unless the document is complex and the stakes justify it.

**For regulatory compliance:** GPT-5 for depth + correct citations, Sonnet for first-pass breadth.

---

## Part 5: Open Questions

### Still Unanswered

1. **Are these findings corpus-specific?** All 74 experiments used gargoyle architecture docs. Different domains may shift rankings.

2. **How much do results vary across runs?** All findings are single-run. Stochastic variation is unquantified.

3. **What happens on 2000+ line documents?** Largest tested is 1,110 lines. Unknown if model rankings shift at extreme scale.

4. **Cross-document consistency as maintenance tool:** Does running cross-doc analysis across MORE document pairs yield additional real inconsistencies? Could become a systematic documentation maintenance tool.

5. **Why Opus dominates cross-doc consistency:** Is it because contradictions are easy to verify once spotted (reducing GPT-5's verification advantage)? Or because boundary reasoning (Opus's strength) is the primary skill needed?

### Answered Questions (from open-questions.md)

- ~~Opus + narrow framing for contradiction detection~~ → **WRONG QUESTION** (#43). Opus doesn't try to match GPT-5 — it finds a different CLASS of contradiction. GPT-5 finds specification conflicts (same scenario, conflicting prescriptions). Opus finds logical impossibilities (rules whose interaction produces impossible conditions). Neither dominates.

- ~~Sonnet + narrow framing = GPT-5 level?~~ → **NO** (#39). The gap is reasoning depth, not framing.

- ~~Adversarial ensemble (GPT-5 → Opus)?~~ → **YES** (#35). 30% more findings at 28% more cost.

- ~~Opus's "missing feature identification" mode — is it promptable?~~ → **YES** (#26). All models find regulatory gaps when explicitly prompted.

- ~~Is Opus > GPT-5 for coherence tasks universal?~~ → **NO** (#27). Document complexity affects ranking.