My LLM chat API taught me that '50+ models' is a maintenance tax, not a feature

An OpenAI-compatible chat API was launched with over 50 models accessible through a single integration. While the marketing promise of simplicity was straightforward, the engineering reality proved much more challenging. The first hurdle was creating a model registry, which had to account for inconsistencies in model listings from different providers.

Each provider used varying terminology and parameters for models, leading to the creation of a normalization layer to translate between these vocabularies. The second challenge was routing requests to the most appropriate model based on the user's chosen pricing tier. This required maintaining up-to-date latency and cost data for each model, as outdated information could result in agents selecting models that had become more expensive.

The most surprising cost was handling model deprecations. Providers would retire models with varying notice periods, causing agents using the API to encounter 404 errors when they used hardcoded model names. To address this, the API now treats model IDs as leases rather than permanent identities, returning a deprecation header when a model is expected to be removed.

The author learned that providing a unified model catalog is more than just a convenience wrapper; it requires schema validation, freshness guarantees, and a clear deprecation policy, just like any other API. The chat API is available at https://x402.freeq.one/tools/llm_chat.html for those interested in exploring the normalization challenges.