Claude Sonnet 5.5 vs Kimi K3: Specs & Benchmark Comparison
Claude Sonnet 5.5 is developed by Anthropic, while Kimi K3 comes from Moonshot AI. Kimi K3 was released in July 2026, and Claude Sonnet 5.5 followed 2 months later in September 2026. Kimi K3 has a published size of about 2.8 trillion parameters; Anthropic has not disclosed the parameter count of Claude Sonnet 5.5.
The two models share 4 published benchmarks. Claude Sonnet 5.5 leads on 4 of them. The widest gaps are on AutomationBench, where Claude Sonnet 5.5 scores 44.7% against 30.8%; OfficeQA Pro, where Claude Sonnet 5.5 scores 65.6% against 63.3%. Averaged across everything we track, Claude Sonnet 5.5 sits at 67.4% and Kimi K3 at 67.8%.
Claude Sonnet 5.5 is the cheaper API at $2 per million input tokens and $10 per million output tokens, about 50% below Kimi K3 at $3 and $15. Both accept a context window of about 1M tokens. Both accept text and images as input.
| Characteristic | Claude Sonnet 5.5 | Kimi K3 |
|---|---|---|
| Company | Anthropic | Moonshot AI |
| Release Date | September 28, 2026 | July 16, 2026 |
| Parameters | — | 2.8T |
| Multimodal | Yes | Yes |
| Context (input) | 1.0M | 1.0M |
| Context (output) | 128K | 1.0M |
| Input Price / 1M | $2.00 | $3.00 |
| Output Price / 1M | $10.00 | $15.00 |
| Average Score | 67.4% | 67.8% |
| Benchmarks | ||
| AutomationBench | 44.7% | 30.8% |
| OfficeQA Pro | 65.6% | 63.3% |
| DeepSWE 1.1 | 71.0% | 69.0% |
| Program Bench | 79.7% | 77.8% |
Visual Benchmark Comparison
Verdict
Claude Sonnet 5.5 leads in 2 out of 4 comparison categories.
Both models show comparable average scores: Claude Sonnet 5.5 — 0.7, Kimi K3 — 0.7.
Claude Sonnet 5.5 is 1.5x cheaper: input $2.00/1M vs $3.00/1M tokens.
Same context size: 1M tokens.
Claude Sonnet 5.5 is newer: released 9/28/2026 vs 7/16/2026.
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Frequently Asked Questions
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The Claude Sonnet 5.5 and Kimi K3 comparison is updated for 2026. Data includes benchmark results, API pricing, context window size and other specifications. For more detailed information, visit the Claude Sonnet 5.5 or Kimi K3 page. See also the complete list of AI model comparisons.