Claude Opus 5 vs GPT-5.6 Sol: The Value Flagships

Claude Opus 5 shipped July 24, 2026 as Anthropic's value flagship, then the default Opus, at the same $5 in / $25 out per MTok as the Claude Opus 4.8 it replaced. GPT-5.6 Sol went GA July 9, 2026 as the only GPT-5.6 tier with max reasoning effort and ultra mode. They differ by 20% on both input and output:

On cost, Sol is 20% cheaper on both sides of the meter: $4/$20 versus $5/$25 per million input/output tokens. A feature consuming 500k input and 100k output tokens costs about $5.00 on Opus 5 versus $4.00 on Sol. Sol's rate is promotional through at least November 21, 2026. Deeper single-model breakdowns: Claude Opus 5 for coding and GPT-5.6 Sol for coding.

Here is the honest catch, and it is worth stating plainly because most comparisons paper over it. Opus 5 and Sol share no benchmark. Anthropic reports Opus 5 in relative terms against its own lineup, within 0.5% of fable 5 on CursorBench 3.2, beats fable 5's best on OSWorld 2.0, all from Anthropic launch materials. OpenAI reports Sol on Terminal-Bench 2.1, and third parties have run Sol on SWE-bench Pro. There is no test both models have a number on, so any "Opus 5 beats Sol by X points" claim would be fabricated.

What you can do is chain through a shared reference. Anthropic positions Opus 5 within 0.5% of Fable 5 on CursorBench, and Fable 5 has a measured lead over Sol on SWE-bench Pro (80.3% versus Sol's 64.6%). That chain points toward Opus 5 for repo-level, issue-resolution coding, but it is a chain of Anthropic's own relative claims across different benchmarks, not a measured Opus-5-vs-Sol result. Treat it as a lean, not a verdict.

Beyond benchmarks, the two flagships spend compute differently. Opus 5's headline is adjustable effort: dial intelligence up for hard, cross-cutting work or down to conserve tokens on cheaper, faster runs, all within the one $5/$25 model. Sol's headline is an exclusive max reasoning effort level plus ultra mode, which runs parallel subagents natively and lifts Terminal-Bench 2.1 from 88.8% to 91.9% in OpenAI's launch materials.

Note the pricing asymmetry hiding in the capability story: Opus 5's speed lever, Fast mode, is priced as a separate tier (Fast mode ~2.5x speed at twice the base price), while Sol's ultra mode is a capability of the same $4/$20 model, it spends more tokens rather than charging a higher rate.

Because these two were close on price and shared no benchmark, the cheapest way to settle it was to run them head-to-head on your own backlog, which beats any leaderboard for your codebase, and that still holds for their successors. That is the setup AIDEN is built for: a macOS desktop app that orchestrates your existing Claude Code and Codex CLIs on one kanban board, BYOK, local-first, every feature gated behind an approved spec. Assign the same feature once to Opus 5.5 and once to GPT-6.1 Sol, each on its own git branch, and review the two PRs side by side, or split the backlog by task shape. The full lineup lives at AI models for coding, and the tooling comparison at Claude Code vs Codex.

For today's models, see Claude Opus 5.5 vs GPT-6 Astra and GPT-6 Astra vs Sol vs Luna. The archived companions to this page are Opus 5 vs Fable 5 and Fable 5 vs Sol.