--- title: "Auto router, fallbacks and presets for agents" canonical: https://relayswitch.io/features/routing generated: 2026-11-02T10:14:57.615Z source: https://api.relayswitch.io/v1/catalog base_url: https://api.relayswitch.io/v1 --- Routing # The right model per request, and a backup when it fails. Send relayswitch/auto and the router picks a fast, balanced or frontier model for each call. Name fallbacks, save presets, route by throughput. Every answer says which model it was and bills at that model's price. [Get an agent key](https://app.relayswitch.io/console)[Code](#example) Auto router, live Model id relayswitch/auto Fast tier 5 models Balanced tier 5 models Frontier tier 5 models Fallbacks per request up to 5 Session stickiness 30 minutes ## What it does for an agent Auto router relayswitch/auto classifies the request on the API and picks a tier. No extra model call, no added fee. Sticky per session With x-session-id the agent keeps one model for the whole run, so its context and tool habits stay put. Fallback lists models: \[...\] names up to 5 backups. A key can carry fallback\_models for every request that names none. Saved presets Model, fallbacks, params, system prompt and tools under one name, called as @preset/. Change the preset, not the agent. Throughput routing routing: throughput tries the route with the most tokens per second first; latency, the quickest first token. Same price. Spend and concurrency per key Daily, weekly or monthly spend limits and a cap on requests in flight, so a runaway agent stops at its own line. ## Copy, paste, run OpenAI SDK: auto router python 1`from openai import OpenAI` 2`import os` 3 4`client = OpenAI(` 5 `base_url="https://api.relayswitch.io/v1",` 6 `api_key=os.environ["RELAYSWITCH_API_KEY"],` 7`)` 8 9`reply = client.chat.completions.create(` 10 `model="relayswitch/auto",` 11 `messages=[{"role": "user", "content": "Refactor this function to async."}],` 12 `extra_body={"auto": {"tier_max": "balanced"}}, # never frontier` 13 `extra_headers={"x-session-id": "agent-run-42"}, # same model all run` 14`)` 15`print(reply.model) # the model the router chose; billed at its price` Anthropic SDK: fallbacks and throughput python 1`import anthropic` 2`import os` 3 4`client = anthropic.Anthropic(` 5 `base_url="https://api.relayswitch.io/v1",` 6 `api_key=os.environ["RELAYSWITCH_API_KEY"],` 7`)` 8 9`reply = client.messages.create(` 10 `model="claude-sonnet-5-5",` 11 `max_tokens=1024,` 12 `messages=[{"role": "user", "content": "Plan the migration."}],` 13 `extra_body={` 14 `"models": ["gpt-6.1-sol", "kimi-k3"], # tried in order if claude-sonnet-5-5 fails` 15 `"routing": "throughput", # fastest output first` 16 `},` 17`)` 18`print(reply.model)` curl: a preset bash 1`# Save the agent's model, fallbacks, defaults and system prompt once (admin key).` 2`curl https://api.relayswitch.io/v1/presets \` 3 `-H "Authorization: Bearer $ADMIN_KEY" \` 4 `-H "Content-Type: application/json" \` 5 `-d '{` 6 `"name": "coder",` 7 `"model": "claude-sonnet-5-5",` 8 `"models": ["gpt-6.1-sol"],` 9 `"params": {"temperature": 0.2, "max_tokens": 4096},` 10 `"system_prompt": "You are a careful senior engineer.",` 11 `"description": "Coding agent defaults"` 12 `}'` 13 14`# Then any agent calls it by name.` 15`curl https://api.relayswitch.io/v1/chat/completions \` 16 `-H "Authorization: Bearer $RELAYSWITCH_API_KEY" -H "Content-Type: application/json" \` 17 `-d '{"model": "@preset/coder", "messages": [{"role": "user", "content": "Fix the failing test."}]}'` Key API: limits and default fallbacks bash 1`# An agent key with a daily spend limit, 8 requests in flight and fallbacks.` 2`curl https://api.relayswitch.io/v1/keys \` 3 `-H "Authorization: Bearer $ADMIN_KEY" -H "Content-Type: application/json" \` 4 `-d '{"name": "nightly-agent", "monthly_cap_usd": 5, "spend_limit_period": "daily",` 5 `"concurrency": 8, "routing": "throughput",` 6 `"fallback_models": ["gpt-6.1-sol", "kimi-k3"]}'` ## The auto router’s tiers today From GET /v1/catalog auto\_router, priced live in USD per million tokens. | Tier | Model | Input | Output | | --- | --- | --- | --- | | fast | [Claude Haiku 5.5](https://relayswitch.io/models/claude-haiku-5-5) | $0.06 | $0.15 | | fast | [GLM 5.3 Flash](https://relayswitch.io/models/glm-5.3-flash) | $0.09 | $0.15 | | fast | [GPT-6 Luna](https://relayswitch.io/models/gpt-6-luna) | $0.0625 | $0.20 | | fast | [MiniMax M3](https://relayswitch.io/models/minimax-m3) | $0.09 | $0.36 | | fast | [DeepSeek V4.1 Flash](https://relayswitch.io/models/deepseek-v4.1-flash) | $0.06 | $0.18 | | balanced | [Claude Sonnet 5.5](https://relayswitch.io/models/claude-sonnet-5-5) | $1.20 | $3.00 | | balanced | [GPT-6.1 Sol](https://relayswitch.io/models/gpt-6.1-sol) | $0.60 | $3.00 | | balanced | [Gemini 4 Argon](https://relayswitch.io/models/gemini-4-argon) | $0.60 | $3.00 | | balanced | [Kimi K3](https://relayswitch.io/models/kimi-k3) | $0.90 | $4.50 | | balanced | [GLM 5.3](https://relayswitch.io/models/glm-5.3) | $0.3276 | $1.0296 | | frontier | [Claude Opus 5.5](https://relayswitch.io/models/claude-opus-5-5) | $2.80 | $10.00 | | frontier | [GPT-6 Astra](https://relayswitch.io/models/gpt-6-astra) | $3.00 | $15.00 | | frontier | [Claude Fable 5.1](https://relayswitch.io/models/claude-fable-5.1) | $6.00 | $30.00 | | frontier | [Gemini 3.1 Pro Preview](https://relayswitch.io/models/gemini-3.1-pro-preview) | $1.20 | $7.20 | | frontier | [Claude Opus 5](https://relayswitch.io/models/claude-opus-5) | $1.80 | $7.50 | Agent setup guides - [OpenClaw](https://relayswitch.io/guides/openclaw) - [Hermes Agent](https://relayswitch.io/guides/hermes-agent) - [OpenCode](https://relayswitch.io/guides/opencode) - [Claude Code](https://relayswitch.io/guides/claude-code) - [n8n](https://relayswitch.io/guides/n8n) More features - [Agent tools](https://relayswitch.io/features/agent-tools) - [Files and redaction](https://relayswitch.io/features/files) - [Caching and compression](https://relayswitch.io/features/caching) - [Guardrails and sign-in](https://relayswitch.io/features/guardrails) - [MCP gateway](https://relayswitch.io/features/mcp-gateway) - [Endpoints](https://relayswitch.io/features/endpoints) - [Key budgets](https://relayswitch.io/features/key-budgets) - [Observability](https://relayswitch.io/features/observability) - [Hosted agents](https://relayswitch.io/agents) - [Workflows](https://relayswitch.io/workflows) - [Docs](https://relayswitch.io/docs) FAQs ## Questions For agent builders. Open the console A key in under a minute [Get a key](https://app.relayswitch.io/console) Or email [hello@relayswitch.io](mailto:hello@relayswitch.io) ### ### ### ### ### ### ## Route your agents by the request One model id that picks the tier, a backup list, and the price of the model that answered. [All features](https://relayswitch.io/features)[Get an agent key](https://app.relayswitch.io/console)