# One LlamaIndex LLM class for every model family

> Markdown mirror of https://router.one/integrations/llamaindex for AI assistants and crawlers. Router One is an OpenAI-compatible LLM API gateway.
> Last updated: 2026-09-02

LlamaIndex is the data framework for RAG and agents over your own documents, and a single query can fan out into many LLM calls — answer synthesis, sub-questions, reranking, agent steps. Its OpenAILike class talks to any OpenAI-compatible endpoint, so one configuration pointed at Router One reaches GPT, Claude, Gemini, and DeepSeek family models by changing the model string — and every one of those calls gets a per-request cost trace on the gateway, without adding callbacks.

## Configure LlamaIndex to use the Router One base URL

Install llama-index-llms-openai-like and build an OpenAILike with the gateway base URL, your key, and the exact model ID from /models. Set is_chat_model to True (every text model in the catalog is a chat model), is_function_calling_model to True for models that support tools, and context_window to the window shown on /models — left unset it falls back to a 3900-token default. Assign the instance to Settings.llm, or pass it to any index, query engine, or agent:

`llamaindex-router-one.py`

```bash
# pip install llama-index llama-index-llms-openai-like
from llama_index.core import Settings
from llama_index.llms.openai_like import OpenAILike

Settings.llm = OpenAILike(
    model="<model-id-from-/models>",
    api_base="https://api.router.one/v1",
    api_key="sk-your-router-one-key",
    is_chat_model=True,
    is_function_calling_model=True,
    context_window=200000,  # copy the window shown on /models
)

print(Settings.llm.complete("Hello!"))
```

## Which model ID should LlamaIndex send?

Copy the exact model ID from the /models page — IDs are case-sensitive, and the page lists each model's context window, capabilities, and current per-token rates. Create a dedicated API key per tool with its own maxSpend cap, so one runaway tool can't affect other workloads.

## Verify the LlamaIndex call in your request trace

After your first request, open Dashboard → Logs to see its full trace: model, tokens, cost, latency, and status code. From here every LlamaIndex call has a ledger and a trail instead of being a black box.

## FAQ

### Why OpenAILike instead of the OpenAI class with api_base?

Because the plain OpenAI class checks the model name against OpenAI's own model list to infer its context size, and raises ValueError: Unknown model for anything else — including every non-GPT catalog ID — as soon as it needs that metadata. OpenAILike is the documented route for OpenAI-compatible endpoints: it skips the lookup and takes the model's metadata from the arguments you pass, which is why is_chat_model and context_window are set explicitly.

### Is there a TypeScript equivalent?

Yes. In LlamaIndex.TS the OpenAI class from @llamaindex/openai takes baseURL and apiKey in its constructor — new OpenAI({ model, apiKey, baseURL }) with the gateway URL — or reads OPENAI_BASE_URL and OPENAI_API_KEY from the environment. Assign it to Settings.llm and the same model-string switching applies.

### Which models can LlamaIndex use through the gateway?

Any chat-capable model in the catalog — GPT, Claude, Gemini, Grok, DeepSeek, GLM, MiniMax, and Doubao families. The /models page is the source of truth for model IDs and per-token rates.

### Does this work from Mainland China?

Yes. The gateway is reachable from Mainland China without a VPN, and the configuration is identical to the global setup.

### How do I debug a 401/403/429?

Open Dashboard → Logs first to see whether requests reached the gateway and with what status, then walk the error-codes reference to check env vars, key status, and limits.

## See also

- All integration guides: https://router.one/integrations
- Debug 401/403/429 in LlamaIndex: https://router.one/llm-api-error-codes
- Vercel AI SDK setup: https://router.one/integrations/vercel-ai-sdk
- OpenAI SDK setup: https://router.one/integrations/openai-sdk
- LangChain setup: https://router.one/integrations/langchain
- Dify setup: https://router.one/integrations/dify
- What the gateway layer does: https://router.one/llm-api-gateway
- OpenAI-compatible API: https://router.one/openai-compatible-api
- API docs: https://router.one/docs
- Canonical page: https://router.one/integrations/llamaindex
- Models and per-model token rates: https://router.one/models (markdown: https://router.one/models.md)
- Pricing: https://router.one/pricing
- API docs (markdown): https://router.one/docs.md
- Company facts: https://router.one/facts/company.md