# OpenRouter APIs — Google: Gemini 2.5 Flash Lite (google/gemini-2.5-flash-lite)

Guide for calling every confirmed OpenRouter API that serves `google/gemini-2.5-flash-lite`.

Model page: https://openrouter.ai/google/gemini-2.5-flash-lite
Create an API key: https://openrouter.ai/settings/keys

## EU in-region routing

`google/gemini-2.5-flash-lite` is available through EU in-region routing. Requests sent to eu.openrouter.ai are decrypted in the EU and routed only to shared provider endpoints in Europe (the EU/EEA, the UK, and Switzerland).

- Providers in Europe: Google Vertex
- Prices in Europe:
  - Google Vertex: $0.10/M tokens input, $0.40/M tokens output
- Base URL: https://eu.openrouter.ai/api/v1
- Plan: requires Business or Enterprise. Self-serve on Business: no contract, no monthly minimum. https://openrouter.ai/business/eu
- Fails closed: if no shared provider endpoint in Europe is available, the request errors instead of leaving the region. Requests served by your own BYOK key go to your deployment’s region, which you control.

Docs: https://openrouter.ai/docs/guides/features/in-region-routing

## Authentication

Send this header with every request:

- Authorization: Bearer $OPENROUTER_API_KEY

## Text / Chat Completions API

Generate text with `google/gemini-2.5-flash-lite` through OpenRouter's Chat Completions API.

Docs: https://openrouter.ai/docs/api/api-reference/chat/create-a-chat-completion

### Endpoint

POST https://openrouter.ai/api/v1/chat/completions

Headers:
- Content-Type: application/json

### Request fields (google/gemini-2.5-flash-lite)

- model: string (required) — `"google/gemini-2.5-flash-lite"`
- messages: array (required) — ordered conversation messages with `role` and `content`
- stream: boolean (optional) — return Server-Sent Events as tokens are generated
- max_tokens: optional — accepted by this model; see the API reference for its value shape
- reasoning: optional — accepted by this model; see the API reference for its value shape
- response_format: optional — accepted by this model; see the API reference for its value shape
- seed: optional — accepted by this model; see the API reference for its value shape
- stop: optional — accepted by this model; see the API reference for its value shape
- temperature: optional — accepted by this model; see the API reference for its value shape
- tool_choice: optional — accepted by this model; see the API reference for its value shape
- tools: optional — accepted by this model; see the API reference for its value shape
- top_p: optional — accepted by this model; see the API reference for its value shape

The model-specific optional fields above come from this model's advertised capabilities.
`stream` and `provider` routing preferences are API controls accepted independently of that
model capability list.

### Response

Without `stream`, the response is a Chat Completions JSON object:

```json
{
  "id": "gen-abc123",
  "choices": [{ "message": { "role": "assistant", "content": "..." } }],
  "usage": { "prompt_tokens": 12, "completion_tokens": 24, "total_tokens": 36, "cost": 0.001 }
}
```

With `stream: true`, the response is `text/event-stream`: read each `data:` JSON chunk until
`data: [DONE]`. The final usage chunk carries token counts and cost when usage is requested.

### Examples

#### Chat completion

```bash
curl -X POST https://openrouter.ai/api/v1/chat/completions \
  -H "Authorization: Bearer $OPENROUTER_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "model": "google/gemini-2.5-flash-lite",
  "messages": [
    {
      "role": "user",
      "content": "What is the meaning of life?"
    }
  ]
}'
```

### Error differences

- 400 — malformed messages or a parameter this model does not support
- 502 — the upstream text generation failed

## Errors

Failures return `{"error": {"code": <number>, "message": <string>}}` with the HTTP status:

- 400 — malformed request or an unsupported parameter
- 401 — missing or invalid API key
- 402 — insufficient credits
- 403 — spend limit reached, key disabled, or access blocked
- 404 — unknown model or no provider can serve the request
- 429 — rate limited; retry with backoff
- 502 — the operation failed upstream; failed generations are not billed

---

Canonical version of this document: https://openrouter.ai/google/gemini-2.5-flash-lite/llms.txt