models.fyi

Claude Sonnet 5

AnthropicProprietary

Anthropic's mid-tier: near-frontier coding at a third of Opus pricing, with a 1M context window.

Index @ Medium

71.1

Context

1M

$/M in · out

$3 · $15

Median speed

80 tok/s

Released

Sep 29, 2025

02·Which effort for which task

The sweet spot, per task

Cheapest effort tier that keeps ≥96% of this model's peak quality on the benchmarks behind each task type. Below the floor number, quality is not okay — it just fails quietly.

Everyday writing & Q&A

Medium

Chat, drafting, summaries, general questions.

keeps 98.0% of peak−64% cost

Code assist

High

Autocomplete, single functions, small fixes.

keeps 100.0% of peakpeak tier needed

Coding agents

High

Real repos, multi-file changes, end-to-end tickets.

keeps 100.0% of peakpeak tier needed

Math & quantitative

High

Derivations, statistics, financial models.

keeps 100.0% of peakpeak tier needed

⚠ at Low: only 70% of peak — avoid

Hard research problems

High

Novel, frontier, genuinely difficult questions.

keeps 100.0% of peakpeak tier needed

⚠ at Low: only 78% of peak — avoid

Agents & tool use

High

Long workflows with tools, policies, and state.

keeps 100.0% of peakpeak tier needed

03·The effort ladder

Quality and cost, tier by tier

On everyday tasks, Medium keeps 98.0% of High quality at $0.042 vs $0.12 per task.

Intelligence Index by effort

Cost per typical task by effort

04·Benchmark detail

Scores at High

LowMediumHigh
at Highat High (peak)
BenchmarkHighPeakWhat it predicts
MMLU-Pro85.085.0Everyday Q&A · Drafting emails & docs · Summarizing articles
GPQA Diamond84.084.0Technical analysis · Root-cause debugging · Scientific writing
Humanity's Last Exam24.024.0Novel research questions · Frontier problem solving
AIME 202588.088.0Financial modeling · Statistics · Algorithm design
SWE-bench Verified76.076.0Coding agents · Bug fixing in real repos · Multi-file refactors
LiveCodeBench80.080.0Writing functions from scratch · Algorithms · Code autocomplete
τ²-bench82.082.0Tool-using agents · Customer-facing automation · Multi-step workflows
IFEval91.091.0Structured output (JSON) · Templated generation · Batch pipelines

06·Drift

Is it still the same model this week?

Weekly Intelligence Index · dashed rules mark serving-change events

No serving-change events detected for Claude Sonnet 5 in the tracked window.

07·Call it

One key, this model, your effort

The gateway speaks the OpenAI Chat Completions dialect. Pick a host with claude-sonnet-5@host syntax, set reasoning_effort, and the sweet spot above becomes one line of config. Full docs →

chat with Claude Sonnet 5
curl https://models.fyi/api/v1/chat/completions \
  -H "Authorization: Bearer $MFYI_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-sonnet-5",
    "reasoning_effort": "medium",
    "messages": [{"role": "user", "content": "Hello"}]
  }'
# local dev: replace https://models.fyi with http://localhost:3000