Claude Sonnet 5.5 vs Kimi K3.1 Pro
Claude Sonnet 5.5 leads on coding; both list at the same price per million tokens.
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As of 26 Oct 2026, 11:37 UTC · 24-hour board
- 92
- Claude Sonnet 5.5 on the Combined board, last 24 hours · joint 1st of 24
- 81
- Kimi K3.1 Pro on the Combined board, last 24 hours · 19th of 24
- same
- list price per 1M tokens: both $2 in / $10 out
01
Claude Sonnet 5.5 vs Kimi K3.1 Pro at a glance
Both models on the same four boards, the same list-price view and the same drift detectors. Scores carry their standard error; a place is shared, written joint, when the gap is inside that noise.
| Measure | Claude Sonnet 5.5 | Kimi K3.1 Pro |
|---|---|---|
| Combinedscore ± standard error · place, 24-hour board | 92 ± 2.2joint 1st of 24 | 81 ± 2.019th of 24 |
| Codingscore ± standard error · place, 24-hour board | 93 ± 0.5joint 5th of 24 | 81 ± 2.5joint 22nd of 24 |
| List price per 1M tokensinput / output · blended 40/60 | $2 / $10$6.80 blended | $2 / $10$6.80 blended |
| Median response timecoding tasks, last 30 days | 10 s | 12 s |
| Pass ratecoding attempts, last 30 days | 86% | 80% |
| Cost per 1,000 correct answerscoding, last 30 days, every attempt billed | $6.25 | $7.89 |
| Drift statustrend on the 24-hour board · Page-Hinkley per suite | Holding steadyno detection on coding, reasoning and tool use | Holding steady |
| Tracked since | 28 Sep 202622 days | 26 Oct 2026 |
The boards re-rank after every run, so the figures here follow the leaderboard: each model’s own page, Claude Sonnet 5.5 and Kimi K3.1 Pro, carry the full history. The whole board for each category is on best LLM for coding, best LLM for reasoning and best AI model for agents.
02
Is Claude Sonnet 5.5 better than Kimi K3.1 Pro for coding?
The Coding board: seven repository debugging tasks graded by running the project’s own tests, including hidden tests the model never sees, re-tested every four hours.
Claude Sonnet 5.5 scores 93 ± 0.5 — joint 5th of the 24 models on the Coding board in the last 24 hours. Kimi K3.1 Pro scores 81 ± 2.5 — joint 22nd of the 24 models on the Coding board in the last 24 hours. The gap of 12 points is beyond the measurement noise, so Claude Sonnet 5.5 leads on coding.
Over the last 30 days, Claude Sonnet 5.5 passed 86% of its coding attempts and Kimi K3.1 Pro 80%.
See every model on the Coding board on best LLM for coding, or each model’s own page, Claude Sonnet 5.5 and Kimi K3.1 Pro.
03
Is Claude Sonnet 5.5 better than Kimi K3.1 Pro for reasoning?
The Reasoning board: four long, multi-turn working sessions every day, with continuity checked by running code against rules stated earlier in the session.
Claude Sonnet 5.5 scores 97 ± 2.5 — joint 1st of the 22 models on the Reasoning board in the last 24 hours.
See every model on the Reasoning board on best LLM for reasoning.
04
Is Claude Sonnet 5.5 or Kimi K3.1 Pro better for agents and tool calling?
The Tool use board: nine tasks, each in a real sandboxed machine — either the job is done at the end or it is not. Task completion, tool selection, parameter accuracy, efficiency, error handling, context awareness and safety are scored.
Claude Sonnet 5.5 scores 86 ± 2.5 — joint 1st of the 22 models on the Tool use board in the last 24 hours.
See every model on the Tool use board on best AI model for agents.
05
Which is cheaper, Claude Sonnet 5.5 or Kimi K3.1 Pro?
List prices are each provider’s standard rate per million tokens, cache-miss input and output. Cost per correct answer counts every attempt on the coding tasks, failed ones included, over the last 30 days.
Claude Sonnet 5.5 lists at $2 in / $10 out per 1M tokens; Kimi K3.1 Pro at $2 in / $10 out.
On a 40/60 input–output blend the two list at the same price.
Over the last 30 days, 1,000 correct coding answers cost about $6.25 with Claude Sonnet 5.5 and $7.89 with Kimi K3.1 Pro, every attempt billed, failed ones included.
The cheapest model that still passes the tests is on best value AI model.
06
Which is faster, Claude Sonnet 5.5 or Kimi K3.1 Pro?
Median response time of one attempt or one session, from the same runs as the scores, over the last 30 days.
Median response time on the coding tasks over the last 30 days: Claude Sonnet 5.5 10 s, Kimi K3.1 Pro 12 s.
The two are close.
Every model’s median is on fastest AI model.
07
Is Claude Sonnet 5.5 or Kimi K3.1 Pro getting worse?
Page-Hinkley change-point detection (a CUSUM-family test) runs per suite on each model’s daily median, with every constant published; a real shift is confirmed over days, not hours. An hourly canary of two fixed coding probes catches sharp drops.
Claude Sonnet 5.5 is holding steady on the 24-hour board; no Page-Hinkley detection on coding, reasoning or tool use.
Kimi K3.1 Pro is holding steady on the 24-hour board.
The family pages answer the question for every model of a provider: Is Claude getting worse? and Are AI models getting worse?. The method is on AI drift detection.
Three models free · email when a watched model's coding score falls five points in a week
Three models free · email when a watched model's coding score falls five points in a week
08
Should I use Claude Sonnet 5.5 or Kimi K3.1 Pro?
Only a difference that clears a threshold counts: a board lead beyond the measurement noise (the leaderboard’s own tie rule), 10% on list price, 20% on response time or cost per correct answer.
Choose Claude Sonnet 5.5 when
- the work is coding: it leads the Coding board by 12 points in the last 24 hours (93 ± 0.5 against 81 ± 2.5)
- cost per correct answer matters: about $6.25 per 1,000 correct coding answers against $7.89 over the last 30 days
No difference clears a threshold in favour of Kimi K3.1 Pro.
09
Can I route between Claude Sonnet 5.5 and Kimi K3.1 Pro automatically?
One OpenAI-compatible endpoint sends each request to whichever model the boards favour for that kind of work, with your own provider keys.
Yes. The Smart Router is one OpenAI-compatible endpoint with 14 auto-* routing modes: a quality mode such as auto-coding sends each request to the model placing highest on that board, the value modes pick within 5 points of the best and then the cheapest measured cost per run, and auto-split sends traffic by weights you set. Routing is drift-aware by default, uses your own provider keys and adds zero markup on tokens. Free includes 1,000 routed requests a month.
Every mode is described in the router documentation.
1,000 routed requests a month free · your own provider keys · no card
10
How we test Claude Sonnet 5.5 and Kimi K3.1 Pro
Every model on the board runs the same tasks on the same schedule: coding every four hours, reasoning and tool use daily, with an hourly canary probe.
Scores come from our own runs through each provider’s public API, not vendor-reported numbers. Every model gets the same prompts and output budget, and the same sampling settings wherever a provider accepts them, and is graded by executing what it produces. Every score carries a standard error from its own run-to-run repeatability; models whose lead is inside that noise share a place, written joint.
The methodology is public — every weight, statistical test and drift constant. The test tasks are private, so no lab can train on them. The full method, weights and constants are on the methodology page.
11
Claude Sonnet 5.5 vs Kimi K3.1 Pro: questions people ask
Is Claude Sonnet 5.5 better than Kimi K3.1 Pro for coding?
Claude Sonnet 5.5 scores 93 ± 0.5 — joint 5th of the 24 models on the Coding board in the last 24 hours. Kimi K3.1 Pro scores 81 ± 2.5 — joint 22nd of the 24 models on the Coding board in the last 24 hours. The gap of 12 points is beyond the measurement noise, so Claude Sonnet 5.5 leads on coding. Over the last 30 days, Claude Sonnet 5.5 passed 86% of its coding attempts and Kimi K3.1 Pro 80%.
Is Claude Sonnet 5.5 better than Kimi K3.1 Pro for reasoning?
Claude Sonnet 5.5 scores 97 ± 2.5 — joint 1st of the 22 models on the Reasoning board in the last 24 hours.
Is Claude Sonnet 5.5 or Kimi K3.1 Pro better for agents and tool calling?
Claude Sonnet 5.5 scores 86 ± 2.5 — joint 1st of the 22 models on the Tool use board in the last 24 hours.
Which is cheaper, Claude Sonnet 5.5 or Kimi K3.1 Pro?
Claude Sonnet 5.5 lists at $2 in / $10 out per 1M tokens; Kimi K3.1 Pro at $2 in / $10 out. On a 40/60 input–output blend the two list at the same price. Over the last 30 days, 1,000 correct coding answers cost about $6.25 with Claude Sonnet 5.5 and $7.89 with Kimi K3.1 Pro, every attempt billed, failed ones included.
Which is faster, Claude Sonnet 5.5 or Kimi K3.1 Pro?
Median response time on the coding tasks over the last 30 days: Claude Sonnet 5.5 10 s, Kimi K3.1 Pro 12 s. The two are close.
Is Claude Sonnet 5.5 or Kimi K3.1 Pro getting worse?
Claude Sonnet 5.5 is holding steady on the 24-hour board; no Page-Hinkley detection on coding, reasoning or tool use. Kimi K3.1 Pro is holding steady on the 24-hour board. Page-Hinkley change-point detection (a CUSUM-family test) runs per suite on each model’s daily median, with every constant published; a real shift is confirmed over days, not hours. An hourly canary of two fixed coding probes catches sharp drops.
Should I use Claude Sonnet 5.5 or Kimi K3.1 Pro?
Claude Sonnet 5.5 leads on coding; both list at the same price per million tokens. Choose Claude Sonnet 5.5 when the work is coding: it leads the Coding board by 12 points in the last 24 hours (93 ± 0.5 against 81 ± 2.5); cost per correct answer matters: about $6.25 per 1,000 correct coding answers against $7.89 over the last 30 days.
Can I route between Claude Sonnet 5.5 and Kimi K3.1 Pro automatically?
Yes. The Smart Router is one OpenAI-compatible endpoint with 14 auto-* routing modes: a quality mode such as auto-coding sends each request to the model placing highest on that board, the value modes pick within 5 points of the best and then the cheapest measured cost per run, and auto-split sends traffic by weights you set. Routing is drift-aware by default, uses your own provider keys and adds zero markup on tokens. Free includes 1,000 routed requests a month.
Route between them automatically
The Smart Router sends each request to whichever of Claude Sonnet 5.5 and Kimi K3.1 Pro — or any model on the board — the boards favour for that kind of work, with your own provider keys and zero markup on tokens.
1,000 routed requests a month free · your own provider keys · no card
Free account · 24 hours, 7 days and 30 days · no card
Already have an account? Log in