Neither wins outright: Anthropic: Claude Opus 5.5 is the pick when you need file / PDF input, MoonshotAI: Kimi K3.1 Pro when cost matters at scale.
| Spec | Anthropic: Claude Opus 5.5 | MoonshotAI: Kimi K3.1 Pro |
|---|---|---|
| Provider | Anthropic | Moonshotai |
| Input price (per 1M tokens) | $4.00 | $2.00 |
| Output price (per 1M tokens) | $20.00 | $10.00 |
| Blended price (3:1 input/output) | $8.00 | $4.00 |
| Cheaper than … of all models we track | 7% | 15% |
| Context window | 1M tokens (~1,500 pages) | 1.0M tokens (~1,573 pages) |
| Larger context than … of all models | 69% | 80% |
| Max output per response | 128K tokens (~96,000 words) | 944K tokens (~707,800 words) |
| Input types | text, image, file | text, image, video |
| Output types | text | text |
| Free variant | No | No |
| Listed since | 2026-09-22 | 2026-10-23 |
Monthly cost at list price for five common workloads. Token counts per unit are stated so you can scale them to your own traffic. A workload that does not fit a model's context window is marked rather than priced.
| Workload (per month) | Anthropic: Claude Opus 5.5 | MoonshotAI: Kimi K3.1 Pro | Difference |
|---|---|---|---|
| Customer-support chatbot 50,000 conversations — each a 6-turn conversation (1,500 in / 400 out tokens) | $700 | $350 | MoonshotAI: Kimi K3.1 Pro saves $350 |
| RAG search over documents 20,000 questions — each a question answered from ~8 retrieved passages (6,000 in / 500 out tokens) | $680 | $340 | MoonshotAI: Kimi K3.1 Pro saves $340 |
| Coding / tool-using agent 2,000 tasks — each a multi-step task with tool calls and file context (60,000 in / 6,000 out tokens) | $720 | $360 | MoonshotAI: Kimi K3.1 Pro saves $360 |
| Batch summarisation 10,000 documents — each a 6,000-word report summarised to a page (8,000 in / 600 out tokens) | $440 | $220 | MoonshotAI: Kimi K3.1 Pro saves $220 |
| Long-document analysis 500 documents — each a 150-page contract or codebase read in one pass (100,000 in / 2,000 out tokens) | $220 | $110 | MoonshotAI: Kimi K3.1 Pro saves $110 |
| Capability | Anthropic: Claude Opus 5.5 | MoonshotAI: Kimi K3.1 Pro | What it lets you do |
|---|---|---|---|
| Tool / function calling | ✓ Yes | ✓ Yes | call your APIs and run agent loops |
| Structured output (JSON schema) | ✓ Yes | ✓ Yes | return JSON that validates against your schema |
| Reasoning / thinking mode | ✓ Yes | ✓ Yes | spend extra tokens thinking before answering hard problems |
| Image input | ✓ Yes | ✓ Yes | read screenshots, charts and scanned pages |
| Audio input | — | — | take speech or audio directly |
| File / PDF input | ✓ Yes | — | accept documents without your own parsing step |
| Image output | — | — | generate images, not just text |
| Built-in web search | ✓ Yes | — | answer from live web results |
| Seed (reproducible sampling) | — | — | repeat a generation for tests and evals |
| Log-probabilities | — | — | read token confidence for classification and scoring |
From each model's published parameters and input/output types. “—” means not advertised, not proven absent.
Neither wins outright: Anthropic: Claude Opus 5.5 is the pick when you need file / PDF input, MoonshotAI: Kimi K3.1 Pro when cost matters at scale. In short: Anthropic: Claude Opus 5.5 when you need file / PDF input, you need built-in web search; MoonshotAI: Kimi K3.1 Pro when cost matters at scale, you generate long outputs in one go.
MoonshotAI: Kimi K3.1 Pro is cheaper: $4.00 vs $8.00 per 1M tokens at a typical 3:1 input/output mix, 50% less. For 50,000 support conversations a month that is $350 against $700.
Anthropic: Claude Opus 5.5 costs $4.00 per 1M input tokens and $20.00 per 1M output tokens; MoonshotAI: Kimi K3.1 Pro costs $2.00 input and $10.00 output. Output tokens are billed separately, so long answers shift the gap.
MoonshotAI: Kimi K3.1 Pro: 1.0M tokens, about 1,573 pages, against 1M (about 1,500 pages) for Anthropic: Claude Opus 5.5.
Tool calling — Anthropic: Claude Opus 5.5: yes, MoonshotAI: Kimi K3.1 Pro: yes. JSON-schema structured output — Anthropic: Claude Opus 5.5: yes, MoonshotAI: Kimi K3.1 Pro: yes.
Yes, both accept image input.
No free variant is listed for either; both are pay-per-token.
Anthropic: Claude Opus 5.5 can write up to 128K tokens (about 96,000 words) per response; MoonshotAI: Kimi K3.1 Pro up to 944K (about 707,800 words).
Anthropic: Claude Opus 5.5 was listed on 2026-09-22; MoonshotAI: Kimi K3.1 Pro on 2026-10-23.
Claude Opus 5.5 is Anthropic's flagship model for demanding reasoning, coding, and long-horizon agentic work, succeeding Claude Opus 5. It is particularly strong at multi-step changes in large codebases, code...
Full Anthropic: Claude Opus 5.5 specs →Kimi K3.1 Pro is Moonshot AI's flagship open-weight multimodal reasoning model and a post-trained successor to Kimi K3, with a 1M-token context window. It is built for long-horizon coding, 3D...
Full MoonshotAI: Kimi K3.1 Pro specs →