Claude Opus 5.5 vs GPT-6 Sol
Claude Opus 5.5 at medium effort outscores GPT-6 Sol at max — Sol costs 50% less per token but can't close the quality gap at any effort level.
Anthropic's Claude Opus 5.5 and OpenAI's GPT-6 Sol launched on the same day (Sep 22, 2026). GPT-6 Sol is the budget pick at $2/$10 per MTok; Claude Opus 5.5 is the quality leader at $4/$20. This Claude Opus 5.5 vs GPT-6 Sol comparison breaks down their effort ladders, benchmarks and per-task economics — plus why GPT-6.1 Sol replaced Sol after just seven days.
Last updated 2026-10-01 · Vendor data sourced from Anthropic and OpenAI
At a Glance: Opus 5.5 or GPT-6 Sol?
Choose Claude Opus 5.5 when…
You need the highest benchmark quality for agentic coding, business reasoning or knowledge work — Opus leads 5 of 6 benchmarks and its medium effort already beats Sol's max.
Choose GPT-6 Sol when…
Per-token cost is the primary constraint and scores below ~44 on the Intelligence Index are acceptable — Sol's effort ladder is 4–6x cheaper per task than Opus at every level.
Opus 5.5 vs GPT-6 Sol: Key Specifications
API identifiers, pricing, context limits and reasoning behavior — sourced from each vendor's official documentation.
| Spec | Claude Opus 5.5 | GPT-6 Sol |
|---|---|---|
| API model ID | claude-opus-5-5 | gpt-6-sol |
| Released | Sep 22, 2026 | Sep 22, 2026 |
| Tagline | For long-running agentic coding and knowledge work | OpenAI's efficient reasoning model (superseded by GPT-6.1 Sol) |
| Latency | Moderate | Fast |
| Input price (per MTok) | $4 | $2 |
| Output price (per MTok) | $20 | $10 |
| Context window | 1M tokens | 1.05M tokens |
| Max output | 128K tokens (300K on Batch API) | 128K tokens |
| Thinking | Adaptive, always on, cannot be disabled | Reasoning model, effort configurable |
| Default effort | medium | medium |
| Knowledge cutoff | Jun 2026 | Apr 2026 |
| Input modalities | Text + images | Text + images |
| Retirement | Not sooner than Sep 22, 2027 | Superseded by GPT-6.1 Sol (Sep 29, 2026) |
Pricing: Sol Costs 50% Less per Token
At list price, Sol is $2 / $10 vs Opus at $4 / $20 per million tokens — 50% cheaper on both input and output. A typical 100K-input, 20K-output request costs $0.40 on Sol and $0.80 on Opus.
| Pricing Tier | Claude Opus 5.5 | GPT-6 Sol |
|---|---|---|
| Standard API (per MTok) | $4 / $20 | $2 / $10 |
| Batch API (50% off) | $2 / $10 | $1 / $5 |
| Cache write (5 min) | $5 | $2.50 |
| Cache write (1 hour) | $8 | $2.50 |
| Cache read | $0.20 (0.05x base) | $0.20 (0.1x base) |
Cache reads are identical at $0.20 per MTok — the only pricing line where the two match. For cache-heavy workloads, Sol costs 57% of Opus rather than the headline 50%, because cache reads do not benefit from Sol's lower base price.
Batch pricing follows the same 50% pattern: Sol at $1/$5 vs Opus at $2/$10 per MTok. Both offer fast modes at 2x base price.
Long-context surcharge (Sol only): prompts exceeding 272K input tokens trigger Sol's long-context pricing at $4 / $15 per MTok (2x input, 1.5x output). Opus has no long-context surcharge at any prompt length.
Benchmark Results: Opus Leads 5 of 6
Third-party benchmarks from Artificial Analysis (via CodingFleet). Opus scores are at medium effort (its default); Sol scores are at max effort — the best each model can do at their respective default and ceiling.
| Benchmark | Claude Opus 5.5 | GPT-6 Sol | Lead | Note |
|---|---|---|---|---|
| Intelligence Index v4.3.2 | 51 | 48 | Opus +3 | Opus at medium, Sol at max |
| Terminal-Bench 4.0 | 52.5% | 43.9% | Opus +8.6 pp | Agentic coding |
| AA-Briefcase | 1642 Elo | 1483 Elo | Opus +159 | Business reasoning |
| GDPval-AA | 1576 Elo | 1487 Elo | Opus +89 | GDP valuation |
| Long-Context Reasoning | 84.3% | 83.7% | Opus +0.6 pp | — |
| AutomationBench-AA | 61.2% | 61.6% | Sol +0.4 pp | End-to-end automation |
The headline finding: Opus at medium effort (51) already outscores Sol at max effort (48) on the Intelligence Index. Sol's only lead is AutomationBench-AA (+0.4 pp), within noise. Terminal-Bench 4.0 shows the largest gap (+8.6 pp), confirming Opus's agentic coding strength.
Effort Ladder: Score vs Cost per Task
How each model scales with reasoning effort — Intelligence Index score alongside average cost per task. Sol is cheaper at every level but hits a lower ceiling.
| Effort | Opus Score | Opus $/task | Sol Score | Sol $/task |
|---|---|---|---|---|
| low | 42.3 | $0.55 | 33.9 | $0.13 |
| medium | 51 | $1.34 | 39.8 | $0.25 |
| high | 53.6 | $1.82 | 42.8 | $0.37 |
| xhigh | 56.0 | $3.46 | 44.1 | $0.53 |
| max | 58 | $5.98 | 48 | $1.04 |
At low effort, Sol costs $0.13 per task (vs Opus $0.55) — 4.2x cheaper — but scores 33.9 vs 42.3. At max effort, Sol costs $1.04 (vs Opus $5.98) — 5.6x cheaper — but scores 48 vs 58. Sol dominates when your quality threshold is below ~44; above that, only Opus can reach it.
Independent Evaluations: Opus 5.5 vs Sol on BenchLM
BenchLM category averages (Sep 30, 2026). Note: Sol has only 12 benchmarks on BenchLM with many categories marked “coming soon” — treat these numbers as directional.
| Category | Claude Opus 5.5 | GPT-6 Sol |
|---|---|---|
| Overall | 87.68 | 79.16 |
| Agentic | 88.1 | 59.1 |
| Coding | 83.3 | 61.9 |
| Reasoning | 82.4 | 79.6 |
| Multimodal | 88.8 | 83.8 |
| Knowledge | 88.3 | 77.3 |
Opus leads every BenchLM category. The widest gaps are agentic (+29.0) and coding (+21.4). Reasoning is the closest (82.4 vs 79.6). Overall: 87.68 vs 79.16.
Further reading and hands-on comparisons:
Opus 5.5 vs GPT-6 Sol: Which to Choose by Use Case
Match your workload to the model that gives the best balance of quality and cost.
| Scenario | Recommended | Why |
|---|---|---|
| Agentic coding | Opus 5.5 | Terminal-Bench 4.0 lead (+8.6 pp) and higher BenchLM coding score (83.3 vs 61.9) |
| Business reasoning | Opus 5.5 | AA-Briefcase lead (+159 Elo) and GDPval-AA lead (+89 Elo) |
| Long-context workloads (>272K) | Opus 5.5 | No long-context surcharge; Sol reprices at $4/$15 past 272K tokens |
| High-volume low-quality-bar tasks | GPT-6 Sol | 4-6x cheaper per task; acceptable when score below ~44 suffices |
| Budget batch processing | GPT-6 Sol | $1/$5 batch pricing vs $2/$10 — half the cost for bulk work |
| Cache-heavy workloads | Either | Cache reads are identical ($0.20/MTok); Sol saves on non-cached tokens only |
| New projects (greenfield) | GPT-6.1 Sol | If staying with OpenAI, use 6.1 Sol instead — same price, better scores, cheaper cache reads |
GPT-6.1 Sol: The Seven-Day Successor
OpenAI announced GPT-6.1 Sol at DevDay on September 29, 2026 — just seven days after Sol's launch. Key changes:
| GPT-6 Sol | GPT-6.1 Sol | |
|---|---|---|
| Intelligence Index (max) | 48 | 52 (+4) |
| Cache read | $0.20 / MTok | $0.10 / MTok |
| Effort levels | none, low … max | low … max (no none) |
| Knowledge cutoff | Apr 20, 2026 | Apr 30, 2026 |
GPT-6.1 Sol scores ~1 point below GPT-6 Astra on the Intelligence Index at roughly one-quarter the per-task cost. If you are currently on GPT-6 Sol, upgrading to 6.1 Sol is a strict improvement with no downside. Against Opus 5.5, the comparison narrows but Opus still leads most benchmarks.
Switching Between Claude Opus 5.5 and GPT-6 Sol
Different APIs, different ecosystems. Claude and GPT use different message formats, tool-calling conventions and streaming protocols. Migrating a workload between them requires prompt and schema adaptation — there is no drop-in swap.
Reasoning effort maps similarly. Both models support configurable effort levels and default to medium. Sol also offers a “none” level that Opus does not. Higher effort increases quality and cost on both, but token-per-task ratios differ — benchmark on your own workload before comparing cost.
Knowledge cutoffs are close. Both have an April 2026 cutoff (Opus: June 2026). For tasks requiring the latest information, Opus has a two-month advantage.
Platform availability differs. Claude Opus 5.5 is available on Claude API, AWS Bedrock, Google Cloud, Microsoft Foundry and Claude Platform on AWS. GPT-6 Sol is on OpenAI API, Azure OpenAI, ChatGPT Work and Codex. Multi-cloud routing through OpenRouter can abstract the vendor difference for some use cases.
The Bottom Line
GPT-6 Sol is the cheaper model per token, but Claude Opus 5.5 is the cheaper model per quality point above the ~44 threshold. Opus at medium effort already outscores Sol at max, and leads 5 of 6 independent benchmarks. Choose Sol when budget is king and modest quality suffices; choose Opus when benchmark quality, agentic coding strength or long-context work without surcharges matters. And if you are picking an OpenAI model today, skip Sol entirely — GPT-6.1 Sol is the direct upgrade at the same base price.
Opus 5.5 vs GPT-6 Sol: FAQ
What are the main differences between Claude Opus 5.5 and GPT-6 Sol?
Opus 5.5 is Anthropic's flagship reasoning model ($4/$20 per MTok); GPT-6 Sol is OpenAI's efficient reasoning model ($2/$10). Both have million-token-class context windows and configurable effort. Opus leads 5 of 6 benchmarks including agentic coding and business reasoning, while Sol is cheaper per token and wins on AutomationBench. Opus at medium effort outscores Sol at max effort.
Is Claude Opus 5.5 better than GPT-6 Sol?
On benchmarks, yes. Opus at medium effort scores 51 on the Intelligence Index while Sol at max scores 48 — Opus leads without even maxing out its effort budget. Opus also leads Terminal-Bench 4.0 (+8.6 pp), AA-Briefcase (+159 Elo) and GDPval-AA (+89 Elo). Sol edges ahead only on AutomationBench (+0.4 pp). For workloads where quality matters more than per-token cost, Opus is the stronger choice.
Is GPT-6 Sol cheaper than Claude Opus 5.5?
Per token, yes — Sol costs $2/$10 vs Opus at $4/$20 per million input/output tokens. But per task the picture is more nuanced. Sol at max effort costs $1.04 per task to reach a 48 score, while Opus at medium costs $1.34 to reach 51 — only 26% more for a significantly higher score. For budget-constrained workloads below the ~44 score threshold, Sol's lower per-task cost makes it the better value.
Why does Claude Opus 5.5 at medium effort outscore GPT-6 Sol at max?
Claude Opus 5.5 is a more capable base model. Even at medium effort (its default), Opus reaches 51 on the Intelligence Index, while GPT-6 Sol at maximum effort reaches only 48. This means extra reasoning tokens on Sol cannot close the gap — the quality ceiling is lower. This pattern holds across most benchmarks in the comparison.
What happened to GPT-6 Sol? Is it still available?
GPT-6 Sol was superseded by GPT-6.1 Sol just seven days after launch (Sep 29, 2026). OpenAI's documentation now directs users to GPT-6.1 Sol, which scores higher (Intelligence Index 52 at max vs 48) and has cheaper cache reads ($0.10 vs $0.20 per MTok). GPT-6 Sol remains accessible via the API but may be deprecated following OpenAI's standard policy.
How does GPT-6 Sol compare to GPT-6.1 Sol?
GPT-6.1 Sol is the direct upgrade: same $2/$10 base pricing, but cache reads drop from $0.20 to $0.10 per MTok and the Intelligence Index rises from 48 to 52 at max effort. GPT-6.1 Sol also drops the none effort level, starting at low. If you are choosing between the two Sol models, always pick 6.1 Sol.
Do Claude Opus 5.5 and GPT-6 Sol have the same context window?
Nearly identical. Claude Opus 5.5 has a 1M-token context window; GPT-6 Sol has 1.05M tokens. Both support 128K output tokens. Sol triggers long-context pricing past 272K input tokens ($4/$15 per MTok); Opus has no long-context surcharge at any length.
Is Claude Opus 5.5 or GPT-6 Sol better for coding?
Claude Opus 5.5 leads Terminal-Bench 4.0 by 8.6 percentage points (52.5% vs 43.9%) and has higher BenchLM coding scores (83.3 vs 61.9). For agentic coding workflows, Opus delivers significantly stronger results. Sol's lower per-token cost does not compensate for the quality gap on coding tasks.
Can I switch from GPT-6 Sol to Claude Opus 5.5?
Not within a single API conversation. They are from different vendors with different APIs, message formats and tool-calling conventions. Migrating requires adapting prompts and tool schemas. Context and thinking blocks are not portable across vendors.
When were Claude Opus 5.5 and GPT-6 Sol released?
Both launched on the same day: September 22, 2026. Claude Opus 5.5 was Anthropic's flagship launch; GPT-6 Sol was OpenAI's efficient reasoning release. Sol was superseded by GPT-6.1 Sol on September 29, 2026 — just seven days later.
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