✦ Our pick · Explore & explain a codebase
Claude Sonnet 5.5 at xhigh effort, $21.24 per finished task, is the cheapest you can get today. Within our measurement error it ties with Claude Opus 5.5, Claude Opus 5 and Kimi K3: equally good bets, worth trying two.
Updated Oct 13, 2026, every 3 hours. See it live with your plans and costs.
The top 10 for explore & explain a codebase
Trace flows across files and repos, onboard, answer "how does this work", review. Cost per finished task: the tokens at each model's best effort level for this work, plus your time fixing failed attempts ($93 an hour). Success is the share of such tasks a model gets right the first time, on the benchmarks below.
| # | Model | Effort | Success | $/task |
|---|---|---|---|---|
| 1 | Claude Sonnet 5.5 Anthropic | xhigh | 63.1% measured | $21.24 |
| 2 | Claude Opus 5.5 Anthropic | medium | 62.6% measured | $21.63 |
| 3 | Claude Opus 5 Anthropic | high | 65.4% measured | $22.81 |
| 4 | Kimi K3 Kimi | max | 62.4% measured | $23.07 |
| 5 | MiMo-V2.6-Pro Xiaomi | default | 57.3% estimated | $23.40 |
| 6 | Grok 4.7 SpaceXAI | xhigh | 59.6% measured | $23.65 |
| 7 | Qwen3.8 Max Alibaba | default | 58.9% measured | $23.68 |
| 8 | Qwen3.8 Max (0902) Alibaba | default | 58.9% measured | $23.80 |
| 9 | GPT-6.1 Sol OpenAI | medium | 58.0% measured | $24.07 |
| 10 | GLM-5.3 Z AI | max | 56.6% measured | $25.05 |
Best within your tool
| Tool | Model | Effort | $/task |
|---|---|---|---|
| Cursor | Claude Sonnet 5.5 | xhigh | $21.24 |
| Claude Code | Claude Sonnet 5.5 | xhigh | $21.24 |
| Codex | GPT-6.1 Sol | medium | $24.07 |
| Antigravity | Claude Sonnet 5.5 | xhigh | $21.24 |
| GitHub Copilot | Claude Sonnet 5.5 | xhigh | $21.24 |
If tokens come with your plan
Tokens included in a plan cost you nothing extra, so the pick is the most reliable model in it, at the leanest effort level within our error of the best (the top levels only use up the plan sooner).
| Plan | Model | Effort |
|---|---|---|
| Claude Pro | Claude Opus 5.5 | high |
| Claude Max | Claude Opus 5.5 | high |
| ChatGPT Plus or Business | GPT-6.1 Sol | medium |
| ChatGPT Pro | GPT-6.1 Sol | medium |
| Google AI Pro | Claude Opus 5.5 | high |
| Google AI Ultra | Claude Opus 5.5 | high |
Measured on
- SWE-Atlas Codebase QnA · Scale AI; models it hasn't run filled in from Artificial Analysis (agent runs). 124 deep code-comprehension questions on 11 production repos (Go, Python, C, TypeScript): tracing execution across files, explaining behaviour and design. Agents must run and explore the code. Measured for 27 of the 42 ranked models, results as of Oct 13, 2026.
How every number is worked out, with the errors of our estimates: the method.