# Boundary Contract Analysis — Finding #62

**Date:** 2026-05-10  
**Lens:** Boundary Contract Analysis (NEW)  
**Document:** gargoyle's `signal-lifecycle.md` (111 lines)  
**Models:** GPT-5, Claude Opus 4, Claude Sonnet 4

## Summary

New analytical lens that examines implicit contracts at component interfaces — what one component promises/expects that another must deliver/understand. Unlike assumption-finding (what must be true) or race condition analysis (temporal interleavings), this focuses specifically on INTERFACE ASSUMPTIONS.

## Results

| Model | Time | Output tokens | Reasoning tokens | Gaps found | Critical | High |
|---|---|---|---|---|---|---|
| GPT-5 | 125s | 2,062 | 7,744 | 17 | 5 | 4 |
| Claude Opus 4 | ~74s | 2,243 | (internal) | 11 | 3 | 4 |
| Claude Sonnet 4 | ~40s | 947 | (internal) | 8 | 2 | 3 |

## Key Findings

### Common Ground (all 3 found)
- Action normalization responsibility and position state dependency (CRITICAL)
- Instrument ID resolution timing across corporate actions
- stop_loss semantic transfer from signal to PortfolioMonitor
- Quantity/units interpretation for options vs stocks (100x sizing error)
- Audit log write failure handling

### GPT-5 Unique (5 most significant)
1. **Signal fan-out double-execution** (CRITICAL) — "one signal can appear under many decisions" creates execution-level hazard with no dedupe contract
2. **Signal replay/dedup gap** — pipeline processes duplicates normally, only audit-level symptoms
3. **Instrument resolution trust boundary** — wrong-but-known instrument_id passes through
4. **Late-arriving signals silently re-grouped** — no notification or audit
5. **Ticker vs instrument_id mismatch** — misleading observability

### Opus Unique
1. **Entry price reconciliation** — multiple signals with different entry_prices aggregate; which wins?
2. **Aggregator group identification key** — not specified in signal fields
3. **Backpressure expiration criteria** — FIFO without priority could drop risk-critical signals

### Sonnet Unique
1. **Signal ordering contract** — close signal could arrive before buy signal
2. **Signal ID generation entropy** — poor entropy could cause collisions

## Model Strengths for This Lens

| Model | Strength | Best For |
|---|---|---|
| GPT-5 | Exhaustive validation gap enumeration | Comprehensive boundary audits |
| Opus | Design-level incompleteness | "Model is fundamentally underspecified" |
| Sonnet | Protocol/temporal assumptions | Quick first-pass screening |

## Key Insight

The union of all findings (~26 distinct gaps) significantly exceeds any single model's output (17, 11, 8). Only 5 gaps were found by all three models. This lens produces highly differentiated outputs across models — run all three for architecture documents describing component interfaces.

## Practical Application

For documents that describe component interfaces, boundary contract analysis is high-value:
1. Run Sonnet first for quick temporal/protocol screening (40s, cheap)
2. Run GPT-5 for exhaustive validation/semantic gaps (125s, thorough)
3. Run Opus for design-level coherence gaps (74s, insightful)

The combination catches significantly more issues than any single pass.