Is Claude Opus 5.5 better than GPT-6 Sol?

On intelligence, clearly: Artificial Analysis tested both on the same Intelligence Index version on September 22, 2026 and scored Claude Opus 5.5 at 58 (max effort, default fallback enabled) versus 48 for GPT-6 Sol. Opus 5.5 also leads Terminal-Bench 4.0 (66.4%) and GDPval-AA v2.1 (1846 Elo). GPT-6 Sol is the value play: $2/$10 per million tokens against $4/$20, with OpenAI reporting 33.2% on AutomationBench at $0.27 per task and 68.8% on DeepSWE v1.1 at max, within 1.1 points of Claude Fable 5's best at roughly 80% lower cost.

Which is cheaper per task, Claude Opus 5.5 or GPT-6 Sol?

GPT-6 Sol is cheaper at any score it can reach. Artificial Analysis data cited by reviewers shows Sol as the cheaper route to any Intelligence Index score up to about 44; its best result is 47.5 at max effort for about $1.06 per task, while Opus 5.5 at its default medium effort scores 51.2 for about $1.34. So Sol saves roughly 20% per task at its ceiling, but Opus 5.5 reaches scores Sol cannot. Cache reads are identical at $0.20 per million tokens, so long agentic sessions do not widen the gap.

Should I switch from GPT-5.6 Sol to Claude Opus 5.5 or GPT-6 Sol?

GPT-5.6 Sol costs $4/$20, the same as Claude Opus 5.5 and twice GPT-6 Sol. If you stay in OpenAI's ecosystem, GPT-6 Sol is a straight halving of your bill with better factuality and the same API. If you can tolerate a provider switch and four Anthropic API differences (always-on thinking, no forced tool use, model-bound thinking blocks, new computer-use toolset), Opus 5.5 gives you a ten-point intelligence jump at the price you already pay. There is no reason to remain on GPT-5.6 Sol, whose promotional price is scheduled to rise in November 2026.

Do Claude Opus 5.5 and GPT-6 Sol have the same context window?

Nearly. Opus 5.5 has a 1,000,000-token context with 128,000 max output and no long-prompt surcharge. GPT-6 Sol has a 1,050,000-token context, 922,000 max input and 128,000 max output, but any request over 272,000 input tokens is billed at 2x input and 1.5x output for the whole request, making Sol $4/$15 on such prompts, the same input price as Opus 5.5. Opus 5.5's knowledge cutoff is June 2026; Sol's is April 20, 2026.

Quick Answer

Claude Opus 5.5 vs GPT-6 Sol: $4/$20 vs $2/$10 (Sep 2026)

Published: September 23, 2026

The short answer

GPT-6 Sol is the cheaper model; Claude Opus 5.5 is the better one, and the gap is large. Both launched on September 22, 2026, roughly an hour apart. Artificial Analysis scored Opus 5.5 at 58 and GPT-6 Sol at 48 on the same Intelligence Index version, a ten-point spread that puts Opus 5.5 above GPT-6 Astra and Sol level with GPT-5.6. Sol costs half as much per token ($2/$10 vs $4/$20), but per task the saving is closer to 20% at Sol’s ceiling, and Opus 5.5 reaches scores Sol cannot. Pick Sol for bounded, high-volume agent work; pick Opus 5.5 when the task is open-ended.

Side by side

	Claude Opus 5.5	GPT-6 Sol
Released	September 22, 2026	September 22, 2026
Price (in / cached / out per MTok)	$4 / $0.20 / $20	$2 / $0.20 / $10
Cache write	$5 (5m), $8 (1h)	$2.50
Fast mode	$8 / $40, up to 2.5x speed (API only)	2x price
Context / max output	1M / 128K	1.05M (922K max input) / 128K
Long-prompt surcharge	None	>272K input: 2x in, 1.5x out
Knowledge cutoff	June 2026	April 20, 2026
Thinking	Adaptive, always on; default medium	Effort none → max; default medium
Forced tool use	Not supported	Supported
AA Intelligence Index	58 (max)	48 (max)
Terminal-Bench 4.0	66.4% (Anthropic), 59.6% (AA)	Not published
DeepSWE v1.1	Not published	68.8% (max)
AutomationBench	40.0% (Zapier, safeguards counted as failures)	33.2% (xhigh), $0.27/task
GDPval-AA v2.1	1846 Elo	Not published
Clouds	Anthropic, AWS, GCP, Azure	OpenAI, Azure
Safeguards	Fable-class cyber/bio fallbacks	Standard

The benchmark picture

The two labs benchmarked against different targets, so direct rows are scarce. What overlaps:

AutomationBench (Zapier): Opus 5.5 40.0% versus Sol 33.2%. Sol’s number comes with a cost: $0.27 per task, which OpenAI says is 9% of Claude Opus 5’s cost at max. Anthropic’s Opus 5.5 run counted safeguard interventions as failures, so its true score is likely higher.
Intelligence Index (Artificial Analysis): 58 versus 48. Opus 5.5 leads six of ten sub-evaluations outright; Sol’s index barely moved from GPT-5.6 Sol’s 47.
Coding: Anthropic reports Opus 5.5 beating GPT-6 Astra on FrontierCode at ~20% of the cost per task; OpenAI reports Sol matching Fable 5.1 xhigh on FrontierCode at “much lower cost” and 68.8% on DeepSWE. Both claims can be true; Sol is a strong coder for its price, Opus 5.5 is stronger.
Computer use: Sol 60.5% on OSWorld 2.0 offline; Opus 5.5 81.8% partial on OSWorld 2.0 (different reporting bases, so not directly comparable, but the ordering is unlikely to flip).

Cost per task, worked

List prices say Sol is 50% cheaper. Independent cost-per-task data narrows that:

Setting	Index score	Cost per AA task
GPT-6 Sol, max	47.5	~$1.06
Claude Opus 5.5, medium (default)	51.2	~$1.34
Claude Opus 5.5, max	58	Higher; ~119K output tokens/task

So at the top of Sol’s range you pay about 20% less per task than Opus 5.5’s default, for about four fewer index points. Below that, Sol at low or medium effort is the cheaper way to reach any score up to roughly 44. Above 48, only Opus 5.5 is on the menu.

Example, 1,000 agent turns with 30K input (80% cached) and 5K output:

Opus 5.5: input (24K × $0.20 + 6K × $4) = $0.0288; output 5K × $20 = $0.10 → $0.129/turn, $129 total
GPT-6 Sol: input (24K × $0.20 + 6K × $2) = $0.0168; output 5K × $10 = $0.05 → $0.067/turn, $67 total

Identical cache-read prices mean the more of your prompt is cached, the smaller Sol’s percentage advantage gets.

When GPT-6 Sol wins

Bounded, repeatable agent tasks where you can verify output (tests pass, schema validates). Sol’s factuality halved its error rate versus GPT-5.6 Sol, and $0.27 per AutomationBench task is hard to beat.
You need forced tool use (tool_choice: {"type": "tool"}), which Opus 5.5 rejects.
OpenAI-only stacks: Codex, ChatGPT Work, the Responses API’s hosted_shell and apply_patch tools.
Prompts you can keep under 272K tokens. Over that, Sol reprices to $4/$15 and the input-price advantage disappears.

When Claude Opus 5.5 wins

Open-ended engineering: migrations, audits, multi-hour terminal sessions. Terminal-Bench 4.0 66.4% and a 200,000-line audit in under three hours.
Knowledge work with an accuracy bar: GDPval-AA 1846 Elo; 16 of 18 fact-checked reports passed Anthropic’s zero-invented-figures test where Opus 5 and Fable 5.1 passed none.
Very long context: no repricing on 1M tokens.
Security posture: ties Fable 5.1 for lowest prompt-injection success rate on Gray Swan’s benchmark, 85% fewer containment-boundary attempts than Opus 5.
Clearer output: the writing rework was the most-requested Opus fix.

The migration angle

If you are on GPT-5.6 Sol ($4/$20) today, both options are strictly better: GPT-6 Sol halves your bill with no code change; Opus 5.5 keeps your bill and adds ten index points at the cost of a provider switch and four API differences (see How to migrate to Claude Opus 5.5). If you are on Claude Opus 5 ($5/$25), Opus 5.5 is a same-provider upgrade that also cuts cost; see Opus 5.5 vs Opus 5.

Many teams will end up with both: Sol as the high-volume worker, Opus 5.5 as the escalation model. Identical $0.20 cache-read pricing makes that split unusually clean to budget.

Last verified: September 23, 2026.