Claude Opus 5.5 is the best AI for debugging hard problems. Anthropic reports 89.9% on SWE-bench Pro — a test built from real bugs in real repositories — and it is good at the part of debugging that matters most: following a failure across files and layers to its actual cause rather than patching the symptom. For everyday bugs, Claude Sonnet 5.5 is fast enough to use interactively at half the price.
The safest debugging default, the cheaper option worth trying first, and the specialist pick — before you read the detail below.
Claude Opus 5.5 is the strongest answer here for debugging — pick it when quality of output matters more than the $4.00/1M/1M input you pay for it.
Claude Sonnet 5.5 handles the same job for about 50% less per token. Start here and only move up if the output is not good enough.
GPT-6.1 Sol is the fastest of these for debugging — worth it when latency is what the reader notices, not the last few points of reasoning depth.
Claude Opus 5.5 is the strongest debugging model for bugs that span files and systems.
Claude Sonnet 5.5 handles most day-to-day debugging at half the price, and faster.
DeepSeek V4.1 Flash is the low-cost open-weight option for high-volume, reviewed fixes.
Use Claude Opus 5.5 for tricky bugs, architecture-level breakages and multi-file reasoning.
Use Claude Sonnet 5.5 for day-to-day debugging inside your editor.
Use DeepSeek V4.1 Flash for cheap first-pass fixes that a developer reviews before merging.
Switch the scoring lens to see whether the debugging answer changes when cost, speed, or long-document depth leads the decision.
Anthropic / Balanced / Oct 10, 2026
Near-Opus 5.5 quality on scoped work at half the price.
Ranks models by the broadest mix of coding, writing, research, and long-context usefulness.
The work is long, ambiguous and multi-step — Anthropic positions Opus 5.5 for exactly that — or you need the lowest possible price, where Haiku 5.5 costs a twentieth as much.
Where the debugging recommendation shifts once you weigh price or latency differently.
Anthropic's new coding default — top SWE-bench Pro score at a lower price than Opus 5.
Near-Opus 5.5 quality on scoped work at half the price.
Near-Astra capability at Sol pricing — OpenAI's value pick.
DeepSeek's open, cheap new default — V4-Pro now routes to it.
List prices and published scores — the numbers this page's pick is built from.
| Model | Input | Output | Est. month | Context | Speed | Coding | Writing | Research |
|---|---|---|---|---|---|---|---|---|
| Claude Opus 5.5Anthropic | $4.00/1M | $20.00/1M | $80 | 1M tokens | Deliberate | 100 | 97 | 99 |
| Claude Sonnet 5.5Anthropic | $2.00/1M | $10.00/1M | $40 | 1M tokens | Fast | 98 | 98 | 95 |
| GPT-6.1 SolOpenAI | $2.00/1M | $10.00/1M | $40 | 1.1M tokens | Balanced | 98 | 94 | 97 |
| DeepSeek V4.1 FlashDeepSeek | $0.30/1M | $1.20/1M | $5.40 | 1.0M tokens | Fast | 89 | 83 | 83 |
Scores out of 100 — how we evaluate models. “Est. month” is 10M in / 2M out at list price: a ceiling, no discounts.
Why each one is on the shortlist for debugging, what it is genuinely good at, and where we would steer you away from it.
Our pick for debugging. It scores 100/100 on the coding axis we weight this page by, and nothing else in this shortlist matches it on output quality.
Anthropic's September 22, 2026 Opus — a step up from Opus 5 on agentic coding, long-running agent work and vision, at a lower $4/$20 list price and with fewer tokens spent per finished task.
Your tasks are well-scoped and latency-sensitive — Sonnet 5.5 is half the price and Anthropic says it is the fastest Sonnet yet.
The new premium coding default from Anthropic. Opus 5.5 posts the highest SWE-bench Pro figure in any launch table we track and costs less than Opus 5 did. Fable 5.1 still makes sense for the hardest open-ended research at $10/$50; for almost everything else Opus 5.5 is the better buy, and Sonnet 5.5 at half the price is close behind on well-scoped work.
Full pricing, benchmark table and release notes on the Claude Opus 5.5 page.
Where most budgets should land for debugging — about 50% less per token than Claude Opus 5.5, and still 98/100 on the coding axis.
Anthropic's September 28, 2026 Sonnet — built for well-scoped everyday work like features, bug fixes, documents, slides and spreadsheets, priced at $2/$10 and close to Opus 5.5 on most of Anthropic's launch rows.
The work is long, ambiguous and multi-step — Anthropic positions Opus 5.5 for exactly that — or you need the lowest possible price, where Haiku 5.5 costs a twentieth as much.
The model most people should default to in the Claude lineup. Sonnet 5.5 lands within a few points of Opus 5.5 on most of Anthropic's launch rows, beats it on Terminal-Bench 4.0, and costs half as much. Step up to Opus 5.5 only when the task is open-ended and long.
Full pricing, benchmark table and release notes on the Claude Sonnet 5.5 page.
Here for latency: it answers fastest of anything listed for debugging, at 98/100 on coding.
Near-Astra capability at Sol pricing — OpenAI's value pick. Full GPT-6.1 Sol review →
Also worth a look for debugging, at 89/100 on the coding axis.
DeepSeek's open, cheap new default — V4-Pro now routes to it. Full DeepSeek V4.1 Flash review →
UseRightAI recommendations are based on practical decision factors people actually feel in day-to-day use.
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For debugging, Claude Opus 5.5 (Anthropic) is our pick. Anthropic's new coding default — top SWE-bench Pro score at a lower price than Opus 5. It costs $4/1M input and $20/1M output tokens, with a 1M-token context window — enough headroom for all but the largest debugging jobs. Claude Sonnet 5.5 is the closest alternative if it doesn't fit your setup.
Because the work it is built for overlaps closely with debugging: repository-scale changes and PR work — Anthropic reports 89.9% on SWE-bench Pro, up from 79.2% for Opus 5 and long unattended agent runs where per-task token spend matters as much as the per-token price. The new premium coding default from Anthropic. Opus 5.5 posts the highest SWE-bench Pro figure in any launch table we track and costs less than Opus 5 did. Fable 5.1 still makes sense for the hardest open-ended research at $10/$50; for almost everything else Opus 5.5 is the better buy, and Sonnet 5.5 at half the price is close behind on well-scoped work.
On a moderate month — 10M input and 2M output tokens — Claude Opus 5.5 runs about $80.00 at list price, with no batch or caching discounts applied, so treat that as a ceiling. DeepSeek V4.1 Flash is the cheaper route at roughly $5.40 for the same volume, if debugging is high-volume enough for price to lead the decision.
Not ahead everywhere: Anthropic's own table has Opus 5 higher on Toolathlon Verified (80.6% vs 77.8%). Fast mode doubles the price to $8/$40. Avoid it if your tasks are well-scoped and latency-sensitive — Sonnet 5.5 is half the price and Anthropic says it is the fastest Sonnet yet. None of that rules it out for debugging on its own — but if one of those limits maps onto how you actually work, take the alternative on this page seriously rather than defaulting to the top pick.
DeepSeek V4.1 Flash at $0.3/1M input is the budget option here. DeepSeek's open, cheap new default — V4-Pro now routes to it. Expect a quality step down on the hardest cases — the usual pattern is to route routine debugging volume to DeepSeek V4.1 Flash and keep Claude Opus 5.5 for the work where a wrong answer is expensive.
Claude Sonnet 5.5, rated fast against Claude Opus 5.5's deliberate. Speed matters most for interactive and high-volume work; if your debugging runs in the background, the slower and more capable model is usually the better trade.