Claude Opus 5.5 vs Kimi K2.7 Code (Workers AI)
Reading a 26.2K-token pull request costs $0.1048 on Claude Opus 5.5, 4.2× the $0.0249 it costs on Kimi K2.7 Code (Workers AI). Claude Opus 5.5 is a frontier model and Kimi K2.7 Code (Workers AI) a mid-range one. In the benchmark Claude Opus 5.5 caught 52 percentage points more of the known defects than Kimi K2.7 Code (Workers AI) (95% interval +41 pts to +63 pts, a − b).
Side by side
| Figure | Claude Opus 5.5 | Kimi K2.7 Code (Workers AI) |
|---|---|---|
| Price tier | Frontier | Mid-range |
| Bugs caughtshare of known bugs | 90% (better) | 38% |
| False alarmsper clean PR | 1.7 (better) | 2.6 |
| Cost per reviewmeasured | $0.1525 | $0.0567 (better) |
| Cost per bug caught | $0.1921 | $0.0805 (better) |
| Exact linecatches on the expected lines | 89% (better) | 79% |
| Review timemean | 33s (better) | 610s |
| Typical review calllist price | $0.1532 | $0.0346 (better) |
| Input / 1M tokens | $4.00 | $0.95 (better) |
| Output / 1M tokens | $20.00 | $4.00 (better) |
| Context window | 1M | 262.1K |
Head to head
The known bugs both were scored on, by who caught each in at least one run.
By language
| Model | All | TypeScript6 bugs | Go4 bugs | Java4 bugs | Rust4 bugs | C#3 bugs | JavaScript3 bugs | Kotlin3 bugs | PHP3 bugs | Python3 bugs | Ruby3 bugs | Swift3 bugs | C++2 bugs | C1 bug |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Claude Opus 5.5 | 90% | 100% | 50% | 78% | 100% | 100% | 100% | 67% | 100% | 100% | 89% | 100% | 100% | 100% |
| Kimi K2.7 Code (Workers AI) | 38% | 75% | 26% | 31% | 46% | 19% | 8% | 14% | 42% | 62% | 33% | 46% | 6% | 40% |
Of the 42 known bugs both were scored on, both caught 31 and neither caught 1. Claude Opus 5.5 caught 8 bugs that Kimi K2.7 Code (Workers AI) missed: 2 in JavaScript, 2 in Ruby, 1 in C++, 1 in C#, 1 in Java and 1 in Rust. Kimi K2.7 Code (Workers AI) caught 2 bugs that Claude Opus 5.5 missed: 1 in Go and 1 in Kotlin.
On pull requests with no known bug, Claude Opus 5.5 raised 1.7 false alarms per review and Kimi K2.7 Code (Workers AI) 2.6. A measured review cost $0.1525 on Claude Opus 5.5, 2.7× the cost of $0.0567 on Kimi K2.7 Code (Workers AI).
| Pull request | Language · kind | Claude Opus 5.5 | Kimi K2.7 Code (Workers AI) |
|---|---|---|---|
| denoland/denoperf(libs/core): poll only ready handles and yield between I/O batches | Rust · Concurrency | 1/1 | 0/5 |
| dotnet/orleansfix(serialization): cap codec allocations | C# · Logic | 1/1 | 0/7 |
| ggml-org/llama.cpprpc : cache and reuse compute graphs | C++ · Security | 1/1 | 0/5 |
| pinojs/thread-streamrefactor: replace setTimeout with Atomics.waitAsync | JavaScript · Concurrency | 1/1 | 0/8 |
| sindresorhus/p-throttleAdd `weight` option | JavaScript · Logic | 1/1 | 0/8 |
| socketry/asyncBarrier wait in completion order + `Queue#close`. | Ruby · Concurrency | 1/1 | 0/5 |
| rails/railsReimplement Action Cable redis adapter with redis-client | Ruby · Logic | 2/3 | 0/5 |
| jhy/jsoupStore cached child els in Attributes, not field | Java · Concurrency | 1/2 | 0/16 |
| go-gitea/giteaperf(gitdiff): optimize inline diff highlighting using cache | Go · Error handling | 0/1 | 1/4 |
| kotest/kotestFix DataClassEq comparator | Kotlin · Logic | 0/1 | 1/7 |
Defects caught over all runs: a PR reviewed three times with one known bug shows 3/3 when it was caught every time.
Every bug each was scored on: Claude Opus 5.5 and Kimi K2.7 Code (Workers AI).