28 models on LLM.API accept the same requests as Claude Sonnet 5. They are rated 1.0–5.0 from our own catalogue data, benchmarked where independent scores exist, and priced against Claude Sonnet 5, so you can see what a swap costs before you make it.
Pick your main pain point — the picks, reviews and table below narrow to models that fix it.
Top picks
Chosen automatically from rating, published price and capability match, updated weekly. Every point comes from published data, including where Claude Sonnet 5 is still the better choice.
Pick the stage closest to yours. Costs use each model's published per-token list price and assume 75% of tokens are input, which is typical for chat and RAG. Your own ratio will move the numbers, not the ranking much.
Claude Sonnet 5 at this volume: $20.00 a month75% input / 25% output tokens, list prices
Showing the top 12 of 28. Pick a filter to see every match.
Benchmarks: quality and speed, not just price
Independent scores from Artificial Analysis: the intelligence index blends reasoning, knowledge, maths and coding tests; output speed is measured tokens per second. "Input $ per index point" shows how much quality each dollar buys.
Source: Artificial Analysis. 11 of 28 alternatives have published scores; the rest are shown without one rather than estimated. Always confirm on your own prompts.
Which one for your workload?
Different pipelines stress different numbers. Here is what actually drives the choice for each one, which model wins on that number, and how it stacks up against Claude Sonnet 5.
If you needDocument extraction and RAG→ GPT-5.6 Luna
What matters: Long inputs, lots of them: context size and input price matter most.
Retrieval pipelines send far more tokens in than they get back — often 20 to 50 input tokens for every output token. That makes input price and context size the two numbers that decide your bill. A bigger window also means fewer chunks, simpler retrieval logic and less risk of cutting off the passage that holds the answer.
Our pick: GPT-5.6 Luna★ 3.8 1.1M context at $0.20 / 1M in.
Context window (tokens)
Claude Sonnet 51M
GPT-5.6 Luna1.1M
Agents and tool calling
What matters: Needs reliable function calls and JSON output across many steps.
Agents fail in quiet ways: a malformed JSON argument or a skipped tool call breaks the loop several steps later. Native tool calling plus JSON mode is the baseline, and general reasoning strength matters because the model plans each next step itself. The intelligence index is the best public proxy for that.
Our pick: DeepSeek V4.1 Flash★ 3.9 Tool calling and JSON mode, rated ★ 3.9, intelligence index 40.
Intelligence index (Artificial Analysis)
Claude Sonnet 538
DeepSeek V4.1 Flash40
1.1× Claude Sonnet 5.
Air-gapped or compliance-bound
What matters: Data cannot leave your cloud or region.
If data residency or an air-gapped network is a hard requirement, no hosted-only model qualifies, however good it is. Open weights give you an exit: prototype through the API today, then run the same model inside your own cloud when the compliance review lands, without rewriting prompts.
Our pick: DeepSeek V4.1 Flash★ 3.9 Published weights — self-host it and keep every token in your own environment.
LLM API rating (1–5)
Claude Sonnet 53.3
DeepSeek V4.1 Flash3.9
1.2× Claude Sonnet 5.
Budget batch jobs
What matters: Classification, tagging, summaries at volume where cost per token dominates.
Tagging, classification and summaries at volume rarely need a frontier model. Here cost per token dominates and a small quality drop is invisible after aggregation. We only consider models rated 3.0 or higher, so the cheapest pick is still a reliable one.
Our pick: GLM-4.6V FlashX★ 3.8 $0.04 per 1M input — 98% under Claude Sonnet 5.
Input price per 1M tokens (lower is better)
Claude Sonnet 5$2.00
GLM-4.6V FlashX$0.04
98% cheaper than Claude Sonnet 5.
Coding assistants
What matters: Code generation, review and refactoring inside editors or CI.
Code work punishes small mistakes: one wrong import and the suggestion is useless. Models built or tuned for code usually beat general models of the same size, and a high intelligence index (which includes coding tests) is the next best signal.
Point your existing OpenAI client at LLM.API and change the model name. Nothing else in your code moves.
cURL
# Same OpenAI-compatible request — only the model name changes.
curl https://api.llmapi.ai/v1/chat/completions \
-H "Authorization: Bearer $LLMAPI_KEY" \
-H "Content-Type: application/json" \
-d '{
"model": "gemini-3.5-flash-lite",
"messages": [{"role":"user","content":"Hello!"}]
}'
Should you actually switch?
✓Good reasons to move off Claude Sonnet 5
1Token spend is your biggest line item and a cheaper model passes your evals.
2You need published weights so the model can move in-house or into a private region later.
3Your prompts or agent traces no longer fit the context window.
4You want a second model behind the same key as a fallback when one provider has a bad day.
–Good reasons to stay
1Your prompts are tuned to Claude Sonnet 5 and the quality gap shows up in your own evals.
2You rely on features the alternatives do not list on their model page.
3The saving is small next to the cost of re-testing a production pipeline.
4Running Claude Sonnet 5 through LLM.API already cuts the list price, so the gap is narrower than it looks.
Frequently asked questions
Are these Claude Sonnet 5 alternatives drop-in replacements?
Every model listed here is served on LLM.API through the same OpenAI-compatible /v1/chat/completions endpoint, and each one accepts the same input types as Claude Sonnet 5. In most cases you change the "model" string and nothing else. Provider-specific parameters are listed on each model page, so check those before you switch a production prompt.
Do I need a separate API key for each alternative?
No. One LLM.API key covers every model on this page, with one invoice and one set of usage logs, so you can A/B two models against the same traffic without opening new accounts.
How is the rating calculated?
It comes from our own catalogue data, not paid reviews: 40% capability (price tier and how recent the model is), 35% value for money compared with similar models, and 25% context size plus support for tools, JSON and streaming. Each model has one rating, and it is the same on every page it appears on. It updates weekly.
Where do the benchmark scores come from?
The intelligence index and output speed are published by Artificial Analysis, an independent benchmarking site. We only show a score where they publish one; models without a score show a dash rather than an estimate.
Will I lose quality by moving off Claude Sonnet 5?
It depends on the workload. Swap the top-rated alternative in for a sample of real traffic, compare the outputs side by side, and keep whichever wins. Because both models sit behind the same key, running that comparison costs you only the tokens.
Are the prices on this page current?
Prices come straight from the LLM.API catalogue and refresh every Sunday. Where a provider has not published a rate, the table shows a dash instead of an estimate.
28 alternatives live now
Swap Claude Sonnet 5 in one line. Keep the one that wins.
One API key for every model on this page. Run Claude Sonnet 5 and any alternative side by side on your real traffic, then keep whichever is cheaper, faster or better.