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Opus 5 or Kimi K3 Max: an 18-point performance gap, a 40 percent cost difference
Kimi carries a 40 percent lower operating cost and sits only 18 points below on the web-dev leaderboard, the narrowest performance gap in our entire table. What the extra 40 percent cost actually buys is not a higher-performing model; it is official tooling and an Iran access parameter that has at least been measured.
Specifications where both sides have a verified figure on record
| Claude Opus 5 | Kimi K3 Max | |
|---|---|---|
| API model ID | claude-opus-5 | kimi-k3 |
| Context window | 1 million tokens | 1 million tokens |
| Input price | $5 per million tokens | $3 per million tokens |
| Output price | $25 per million tokens | $15 per million tokens |
A row where one side lacks a verified figure is dropped from the table entirely, because a half-empty row biases the reader toward the filled side.
The narrowest performance gap in this table
Opus 5 scores 1692 on WebDev Arena and Kimi K3 Max scores 1674. Eighteen points of gap, on a leaderboard whose top-to-floor range spans 138 points. Meanwhile Opus 5's output cost is $25 and Kimi's is $15. If the decision rested solely on these two figures, Kimi would be the obvious choice.
A technical note in the first row of the table above
Two rows in that table require careful reading. The context window row prints one million tokens on both sides, because the Kimi figure is 1,048,576 and our formatting tool rounds it; the real difference is under five percent and creates no operational limitation in practice. The second row matters more: in the API id row, the Kimi side reads kimi-k3, not kimi-k3-max. The technical reason is that no model named Kimi K3 Max exists in the Moonshot catalogue; that name is simply a leaderboard row describing a higher reasoning-effort level. What you are actually purchasing is kimi-k3, and the table's price and context window belong to that base model.
What that 40 percent extra cost is spent on
In the tooling maturity column, Opus 5 scores 4 of 4 and Kimi scores 1 of 4: the Moonshot platform documentation carries neither an official command-line tool nor an editor extension. The second parameter is the Iran column. Anthropic publishes a supported-countries list and Iran is not on it, so Opus 5 is recorded as blocked; Moonshot publishes no list at all, so Kimi stays in an unchecked state. In our ranking system, a vendor that documents its own restriction outranks one that documents nothing.
This is the right pick if Claude Opus 5
- You have an operational requirement for official tooling: a command line, an editor extension, batch execution, presence on a major cloud infrastructure.
- You want your country's access status documented at all, even when the answer is negative.
- That eighteen-point gap is decisive for you, because your workload sits at the hard edge of performance.
This is the right pick if Kimi K3 Max
- Operating cost is the deciding parameter: $3 and $15 against $5 and $25.
- Your team writes its own tooling layer and requires no ready-made SDK.
- You send very long inputs: the Kimi window is 1,048,576 tokens, slightly above one million.
Frequently raised questions, with documented answers
Does Kimi K3 Max differ from Kimi K3 in specification
No. The Moonshot catalogue holds only kimi-k3, and the max suffix is a reasoning-effort level recorded in the leaderboard row. The price and context window shown in the table above belong to that same base model.
Which is the better choice for a code workload
If your team builds its own tooling layer and cost is an operational constraint, Kimi; the eighteen-point gap is felt less in practice than the forty percent cost difference. If you rely on official tooling and vendor support, Opus 5, which also ranks first in our table.