Stage 2: Compound Architecture — Twin Swarm + Cognitive Routing

## Step 1: Twin-First Default + Cascade Escalation (inherits Stage 0 + Path D + Path B) **Decision:** Path D's "twin-first, escalate on failure" is the right default because it eliminates routing latency for 80% of tasks and leverages the key finding that RAG achieves 87.2% accuracy alone. But Path D's blind escalation is wasteful. Path B's cascade adds intelligence without replacing the fast path. **Default flow (80% of tasks):** Task → Twin Alpha (Qwen3-235B via Together AI, RAG-augmented) → Output. No classification. No routing. ~1500ms latency (RAG retrieval + generation). **Smart escalation (replaces Path D's blind retry):** When Twin Alpha fails (build error, test failure, user rejection), don't just retry or blindly escalate. Run Path B's Layer 1 feature classifier on the failed task to determine WHY it failed: - Complexity > 0.7 → escalate to Claude (task was too hard for twin) - Domain mismatch detected → route to domain specialist (Swift→Claude on Mac1, analysis→Codex) - The failure reason itself becomes a classification signal **Result:** Twin handles everything by default. Failures get intelligent triage. No upfront routing cost.