Observed

Source-reviewed: caching works but its savings are unverifiable from the gateway's own telemetry: the cache_hit metric reports 0 even when the upstream provider returns cached_tokens (#6229, closed not-planned); Azure gpt-5.2 prompt caching returned 0/5 hits through the proxy vs 4/5 calling Azure directly (#18219, vendor-closed completed 2025-12-29, not TD-re-verified); default load balancing scatters requests across deployments and defeats provider-side cache warmup (#6784 — a prompt-caching-aware routing strategy was later added, closed completed 2025-02-25).