Supported AI Models

Claude Opus 5 Most Powerful

Anthropic's current flagship. Best-in-class reasoning, analysis, and code generation, with a dedicated extended-thinking variant. Use it for research, hard multi-step engineering work, and anything where answer quality outranks cost.

Claude Sonnet 5 New

The current mid-tier Claude: near-Opus intelligence at meaningfully lower cost. The default pick for production workloads — fast enough for interactive apps, strong enough for agentic coding. Also available as an extended-thinking variant.

Claude Opus 4.8 / 4.7 / 4.6

Previous-generation Opus releases, kept available for reproducibility and for pinned production deployments. If you are starting fresh, use claude-opus-5 instead.

Claude Sonnet 4.6 / 4.5

Previous-generation Sonnet releases. Still fully supported for existing integrations that pin a specific version.

Claude Haiku 4.5

Ultra-fast and lightweight. Perfect for high-volume, low-latency tasks: classification, extraction, simple Q&A, and content moderation. Responses typically arrive in under a second.

Claude Extended Thinking

Enable extended thinking on any Claude model for complex reasoning tasks. The model "thinks out loud" before responding, producing more accurate results for math, logic, coding, and multi-step analysis.

GPT-5.6 Series Latest

OpenAI's current GPT-5.6 line, available in three tiers. sol is the high-capability tier for hard reasoning, terra sits in the middle, and luna is the cost-optimised tier for high-volume work. Native function calling and JSON mode on all three.

GPT-5.5 / 5.4

Previous-generation GPT-5 releases, kept available for pinned deployments and A/B comparisons against 5.6.

GPT-Image-2

OpenAI's image generation model, billed per image. Call it via the /v1/images/generations endpoint — image models do not use the chat completions route.

OpenAI-Compatible API Format

KissAPI uses the standard OpenAI API format. If your code works with OpenAI, it works with KissAPI — just change the base URL.

curl https://api.kissapi.ai/v1/chat/completions \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-sonnet-5",
    "messages": [{"role": "user", "content": "Hello!"}],
    "stream": true
  }'

Works with Cursor IDE, Claude Code, Cherry Studio, OpenAI Python SDK, and any OpenAI-compatible client.

Which AI models does KissAPI support?

KissAPI supports Claude Opus 5, Claude Sonnet 5, Claude Haiku 4.5, their extended-thinking variants, the GPT-5.6 series (sol, luna, terra), and gpt-image-2 for image generation, all through one OpenAI-compatible endpoint. Previous-generation versions such as Claude Opus 4.8 and GPT-5.5 stay available for pinned deployments. New models are added as they ship.

What context window do KissAPI models support?

Claude models on KissAPI support up to a 200K-token context window. GPT-5 models follow OpenAI's published context limits.

How do I switch between models on KissAPI?

Change the model name in your API request. Because KissAPI is OpenAI-compatible, switching from claude-sonnet-5 to gpt-5.6-sol or any other model is a one-line change — the endpoint and API key stay the same.