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

Claude Opus 5 shipped July 24, 2026 as Anthropic's new value flagship, the current default Opus, at the same $5 in / $25 out per MTok as the Claude Opus 4.8 it replaces. GPT-5.6 Sol went GA July 9, 2026 as the only GPT-5.6 tier with max reasoning effort and ultra mode. They land within 10% of each other on price, so cost mostly cancels out:

On cost, the only daylight is output: both charge $5 per million input tokens, while Sol's $30 output rate runs 20% above Opus 5's $25. A story consuming 500k input and 100k output tokens costs about $5.00 on Opus 5 versus $5.50 on Sol, real, but rarely decision-grade. 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 $5/$30 model, it spends more tokens rather than charging a higher rate.

Because these two are so close on price and share no benchmark, the cheapest way to settle it is to run them head-to-head on your own backlog, which beats any leaderboard for your codebase. 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 story gated behind an approved spec. Assign the same story once to Opus 5 and once to Sol, each on its own git branch, and review the two PRs side by side, or split the backlog by task shape: repo-heavy stories to Opus 5, terminal-heavy ones to Sol. The full lineup lives at AI models for coding, and the tooling comparison at Claude Code vs Codex.

If your comparison is really Opus 5 against the rest of the Anthropic lineup, see Opus 5 vs Fable 5; if it is the frontier match-up, see Fable 5 vs Sol.