Core Concepts
What is Delimiter?#
Delimiter is a lightweight SDK that monitors AI API rate limits across providers in one dashboard. Two lines of code, zero maintenance — Delimiter automatically detects every AI provider your app talks to.
How it works#
The flow is simple:
Your App → AI Provider → Response → Delimiter reads headers → Dashboard updates
When you call delimiter.init(), the SDK hooks into Node's HTTP layer. Every outbound request is checked against known AI provider domains (api.openai.com, api.anthropic.com, etc.). When a match is found, Delimiter reads the rate-limit headers from the response — headers that providers already include on every response.
Reporting is async and fire-and-forget. Your application code runs exactly as it did before, with zero overhead in the critical path.
This means Delimiter works with any AI SDK, any framework (LangChain, Vercel AI SDK, LiteLLM), or raw fetch() calls. If it makes an HTTP request to an AI API, Delimiter sees it.
What Delimiter never does#
- Never reads, stores, or transmits your API keys. The SDK only reads response headers (rate-limit numbers), not request headers (where API keys live). Your keys stay in your environment.
- Never modifies requests or responses. Delimiter is a passive observer at the network layer. Your API calls are untouched.
- Never adds latency. Header extraction and reporting happen asynchronously, after the response is already returned to your code.
- Never fails loudly. If the Delimiter backend is unreachable, the SDK silently continues. Your application is never affected.
Supported providers#
Delimiter works at the network layer — any AI provider that returns rate-limit headers over HTTP is automatically supported.
| Provider | Domain | Status |
| --- | --- | --- |
| OpenAI | api.openai.com | Auto-detected |
| Anthropic | api.anthropic.com | Auto-detected |
| Google Gemini | generativelanguage.googleapis.com | Auto-detected |
| Mistral | api.mistral.ai | Auto-detected |
| Cohere | api.cohere.com | Auto-detected |
| Groq | api.groq.com | Auto-detected |
| DeepSeek | api.deepseek.com | Auto-detected |
| xAI | api.x.ai | Auto-detected |
| Perplexity | api.perplexity.ai | Auto-detected |
| Together AI | api.together.xyz | Auto-detected |
| Fireworks AI | api.fireworks.ai | Auto-detected |
| Replicate | api.replicate.com | Auto-detected |
| Azure OpenAI | *.openai.azure.com | Auto-detected |
| Amazon Bedrock | bedrock-runtime.*.amazonaws.com | Auto-detected |
| OpenRouter | openrouter.ai | Auto-detected |
New providers are added to the SDK's detection list over time. When a new provider is added, your existing delimiter.init() call picks it up automatically — no code changes.
Architecture#
Delimiter has two parts:
- SDK (npm package) — hooks into the HTTP layer at startup, detects AI provider API calls by domain, extracts rate-limit headers from responses, and reports them asynchronously to the Delimiter backend.
- Dashboard (web app) — receives reports from the SDK, aggregates the data, and displays your rate limit usage in real-time.