Model comparison
GPT-5.5 Pro vs Kimi K3
OpenAI against Moonshot AI, compared on context, price, and verified benchmark results.
Catalog record checked September 3, 2026Individual provider fields may changeEvidence confidence: High — see receipts below
OpenAI
GPT-5.5 Pro
Frontier
Moonshot AI
Kimi K3
Frontier · Open weights
| Specification | GPT-5.5 Pro | Kimi K3 |
|---|---|---|
| Provider | OpenAI | Moonshot AI |
| Tier | Frontier | Frontier |
| Context window | Winner: 1.05M | 1.05M |
| Max output | 128K | 128K |
| Input / 1M tokens | $30 | Winner: $3 |
| Output / 1M tokens | $180 | Winner: $15 |
| Weights | Closed | Open |
| Parameters | Not disclosedUnverified | 2.8T (open-weight MoE) |
| Reasoning levels | none, low, medium, high, xhigh, max | low, high, max |
| Modalities | text, image | text, image, video |
| API model id | gpt-5.5-pro | kimi-k3 |
| Released | April 23, 2026 | July 16, 2026 |
| Artificial Analysis Intelligence Index [xhigh] (2026-08-14) | 60 | Not verifiedUnverified |
| Artificial Analysis Intelligence Index [max] (2026-08-14) | Not verifiedUnverified | 60 |
| Terminal-Bench 2.1 (2026-07-27) | Not verifiedUnverified | 88.3 |
| GPQA Diamond (2026-07-27) | Not verifiedUnverified | 93.5 |
| Humanity's Last Exam (2026-07-27) | Not verifiedUnverified | 56 |
| SWE-bench Verified (2026-09-01) | Not verifiedUnverified | 93.4 |
Prices are USD per million tokens at standard rates, excluding batch and caching discounts. Bold indicates the better figure where one is objectively better. Values we could not confirm from the provider are shown as “Not verified” rather than estimated.
Benchmark receipts
- 2026-09-01: vals.ai SWE-bench Verified leaderboard (independent, mini-swe-agent bash-only); not published by Moonshot; a 76.8 aggregator claim is low-reliability — both notedReal GitHub issue resolution: does the model's patch pass the hidden tests. Comparability: comparable with caveat — Post-audit vendor claims and pre-audit scores sit on different task trust levels; scaffolding (agent harness, compute budget) also dominates results. Never aggregate across scaffolds.
- 2026-08-14: Artificial AnalysisComposite index blending reasoning, knowledge, and coding evals into one 0–100 score. Comparability: directly comparable — AA occasionally rebaselines the index scale between snapshots — a score captured on one date is only comparable to same-snapshot scores (check measuredAt).
- 2026-07-27: Kimi K3 HF model card (vendor, with tools; 43.5 no tools)Agentic terminal work: multi-step tasks executed in a sandboxed shell environment. Comparability: comparable with caveat — Scores across Terminal-Bench major versions (v1 vs v2) are NOT comparable; harness configuration (container, time limits) also shifts results.
Pricing tiers: GPT-5.5 Pro: Standard $30/$180 per MTok; no cached-input discount. Batch $15/$90. · Kimi K3: $3/$15 per MTok; cached input $0.30/MTok. Open-weight under the custom Kimi K3 License (not a standard open-source licence). 2.8T MoE with native vision.
GPT-5.5 Pro
GPT-5.5 Pro is OpenAI's highest-effort tier for maximal accuracy on the hardest tasks.
Best for
- Maximum-accuracy reasoning
- Research
- Hard enterprise workloads
Watch out
At $30/$180 per MTok it is the most expensive OpenAI tier; reserve for work that needs it.
Kimi K3
Kimi K3 is Moonshot AI's open-weight frontier model — 2.8T MoE, 1M context, tied near the top of open-weight leaderboards.
Best for
- Open-weight frontier work
- Long-context
- Multimodal
Watch out
Self-hosting needs large clusters; hosted rates vary.
When the cheaper one wins
Kimi K3 is cheaper on output at $15 per million tokens against $180 for GPT-5.5 Pro — about 12×. Use the cheaper tier for classification, extraction, summarisation, and any task where the expensive model’s extra score does not change the accepted output. The expensive one only pays if your hardest task actually fails on the cheap tier. These are standard-tier API rates, excluding batch and cache discounts.
Run the model pickerEvidence confidence: High
How strong and complete the evidence behind this comparison is — not a prediction of which model is better.
- Pricing verified on both sides — Input and output rates are verified for both models.
- 4/5 core specs verified on both sides — Not published for at least one side: parameter count.
- 1 shared named benchmark (scores match) — Measured on: Artificial Analysis Intelligence Index — scores are equivalent, so the benchmark does not separate the pair.
- Verified within the last 90 days — Newest catalog check was 8 days ago.
- Both models carry source citations — Each side has at least two catalog sources on record.
Source receipts
Each catalog figure was checked against the provider or an independent second source on the date shown.
- GPT-5.5 Pro: OpenAI — Introducing GPT-5.5 (accessed 2026-08-29)
- GPT-5.5 Pro: OpenAI API pricing (gpt-5.5-pro $30/$180) (accessed 2026-08-29)
- Kimi K3: HuggingFace — Kimi K3 (accessed 2026-08-29)
- Kimi K3: Moonshot — Kimi K3 guide (accessed 2026-08-29)
Related comparisons
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- Claude Fable 5 vs GPT-5.5 Pro
- Claude Fable 5 vs Kimi K3
- Claude Mythos 5.1 vs GPT-5.5 Pro
- Claude Mythos 5.1 vs Kimi K3
Diving deeper on one model? GPT-5.5 Pro · Kimi K3
Common questions
GPT-5.5 Pro vs Kimi K3
Answered from the verified figures on this page rather than general guidance.
Is GPT-5.5 Pro or Kimi K3 cheaper for input?
Kimi K3 is cheaper at $3 per million input tokens, against $30 for GPT-5.5 Pro — roughly 10× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; GPT-5.5 Pro has tiered pricing: Standard $30/$180 per MTok; no cached-input discount. Batch $15/$90. Kimi K3 has tiered pricing: $3/$15 per MTok; cached input $0.30/MTok. Open-weight under the custom Kimi K3 License (not a standard open-source licence). 2.8T MoE with native vision.
Is GPT-5.5 Pro or Kimi K3 cheaper for output?
Kimi K3 is cheaper at $15 per million output tokens, against $180 for GPT-5.5 Pro — roughly 12× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; GPT-5.5 Pro has tiered pricing: Standard $30/$180 per MTok; no cached-input discount. Batch $15/$90. Kimi K3 has tiered pricing: $3/$15 per MTok; cached input $0.30/MTok. Open-weight under the custom Kimi K3 License (not a standard open-source licence). 2.8T MoE with native vision.
Which has the larger context window, GPT-5.5 Pro or Kimi K3?
Both accept about 1.05M tokens of context, so document length will not decide between them.
Do GPT-5.5 Pro and Kimi K3 support the same reasoning levels?
GPT-5.5 Pro exposes none, low, medium, high, xhigh, max, while Kimi K3 exposes low, high, max.
Should I use GPT-5.5 Pro or Kimi K3?
Both sit in the frontier tier, so the choice usually comes down to price and context rather than capability. GPT-5.5 Pro suits maximum-accuracy reasoning; Kimi K3 suits open-weight frontier work.
Can I self-host GPT-5.5 Pro or Kimi K3?
Kimi K3 publishes open weights, but self-hosting and third-party provider access depend on the licence, hardware, serving support, and availability. GPT-5.5 Pro is a closed model whose supported access paths are controlled by its provider.
Next step
Choosing between them
The verified figures that separate this pair, computed from the catalog rather than restated boilerplate.
- Input price: Kimi K3 costs $3 per 1M tokens versus $30 for GPT-5.5 Pro — a 10x difference at the headline tier.
- Context: GPT-5.5 Pro takes 1.05M against 1.05M for Kimi K3 — only decisive if your prompts approach the smaller window.
- Deployment: Kimi K3 publishes weights you can self-host; the other is API-only.
Choosing a harness rather than a model — Cursor, Copilot, Claude Code, Windsurf, or Lovable? Compare agentic harnesses · Latest releases.