Claude Fable 5 vs GPT-5.6 Sol (July 2026): The Flagship Coding Match-Up

Quick answer

For repo-level software engineering, the verified data favors Claude Fable 5 (95.0% SWE-bench Verified, 80.3% SWE-bench Pro). For terminal-agent chains, GPT-5.6 Sol is closer, and roughly half the price (88.8% Terminal-Bench 2.1, 91.9% in ultra mode). Both are weeks old; treat every ranking as provisional.

Claude Fable 5 price: $10 in / $50 out per MTok
GPT-5.6 Sol price: $5 in / $30 out per MTok
Fable 5 headline: SWE-bench Verified 95.0% (swebench.com leaderboard)
Sol headline: Terminal-Bench 2.1 88.8%, 91.9% ultra (OpenAI launch materials)

Head-to-Head: The Verified Specs

Both models are new. Claude Fable 5 shipped June 9, 2026, and redeployed globally on July 1. GPT-5.6 Sol went GA July 9, 2026. Here is everything we have verified side by side, with the gaps in the public record marked as gaps rather than papered over:

	Claude Fable 5	GPT-5.6 Sol
Price (per MTok)	$10 in / $50 out	$5 in / $30 out
Released	June 9, 2026	July 9, 2026
Context window	1M tokens (128k output)	Not in our verified data
Signature capability	Adaptive thinking, always on	Max reasoning effort + ultra mode (parallel subagents)
Access	Claude Code /model fable (v2.1.170+)	Codex, current generation
Tier in vendor lineup	Frontier (Mythos-class, above Opus)	Frontier (only 5.6 tier with ultra mode)

Deeper single-model breakdowns live on the dedicated pages: Claude Fable 5 for coding and GPT-5.6 Sol for coding.

The Benchmark Problem: Two Vendors, Two Stories

Here is the thing most head-to-head posts skip: Anthropic and OpenAI publish different benchmarks, so their launch numbers literally cannot be compared cell by cell. Anthropic's story for Fable 5 is repo-level issue resolution: SWE-bench Verified 95.0% (swebench.com leaderboard) and SWE-bench Pro 80.3%. OpenAI's story for Sol is terminal-agent competence: Terminal-Bench 2.1 88.8%, rising to 91.9% in ultra mode. Each vendor is showcasing the benchmark family it wins.

The cross-benchmark evidence is thin but not zero. Third-party SWE-bench Pro runs, not OpenAI-published, place Sol at 64.6% against Fable 5's 80.3%, a wide gap on the one shared yardstick we have. On the other side, OpenAI claims an ALE score of 53.6 and an Artificial Analysis Coding Agent Index of 80.0 for Sol; we have not verified either independently, so treat those as OpenAI's claims.

Community sentiment matches the split. The Hacker News discussion titled “Claude Fable 5 vs GPT-5.5: Better Planning, Similar Execution” captured it for the previous match-up, and the pattern is holding: Claude tends to win on planning and architecture, GPT on terminal execution speed.

Ship your first agent today

Download AIDEN free and point it at your existing Claude Code or Codex setup. No credit card, running in minutes.

Download AIDEN free

Free to start · macOS 12+ · No credit card required

Cost Math: What a Story Actually Costs

Sol undercuts Fable 5 on both sides of the meter: half price on input ($5 vs $10 per MTok) and 40% cheaper on output ($30 vs $50). On a realistic agentic story, say 500k input tokens of repo context and spec, 100k output tokens of code and reasoning, the math looks like this:

500k in / 100k out	Claude Fable 5	GPT-5.6 Sol
Input cost	$5.00	$2.50
Output cost	$5.00	$3.00
Story total	$10.00	$5.50

About $10.00 versus $5.50 per story. Whether the premium is worth it depends entirely on the story: on a hard cross-cutting refactor, one failed run costs more than the price difference; on a mechanical terminal chain, it probably is not. For the broader Claude-side price ladder, see the best Claude model for coding.

When to Pick Which

Pick Claude Fable 5 for

Hard, cross-cutting refactors and architecture work. Long autonomous runs where re-prompting is expensive and adaptive thinking pays off. Planning and spec drafting, where the community consensus and the SWE-bench family both point its way. The 1M-token context that holds a large repo plus specs in one session.

Pick GPT-5.6 Sol for

Terminal-heavy agentic chains, where it posts the best scores OpenAI has published. Work that benefits from ultra mode's native parallel subagents. Teams already on Codex and ChatGPT plans, where it slots in at half Fable 5's input price. If you're Codex-first, start with our Codex model guide.

Or Run Both on One Board

The quiet answer to “Fable or Sol” in mid-2026 is: both. Dual-tool workflows are mainstream now, OpenAI even ships a Codex plugin for Claude Code, because the models' strengths are complementary rather than overlapping.

That is the setup AIDEN is built for. It is 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 Fable 5 to the gnarly cross-cutting refactor and Sol to the terminal-heavy migration story, in the same project, each on its own git branch. The comparison with running Codex bare is covered in AIDEN vs Codex CLI, and the model hub with every current option lives at AI models for coding.

FAQ

Is Claude Fable 5 better than GPT-5.6 Sol?

For repo-level software engineering, the verified data favors Fable 5: it leads SWE-bench Verified at 95.0% and SWE-bench Pro at 80.3%, where third-party runs put Sol at 64.6% on SWE-bench Pro. For terminal-agent work, Sol posts the strongest scores OpenAI has published (Terminal-Bench 2.1 at 88.8%) at roughly half the price. Neither model is better at everything; the honest answer depends on the task shape.

Why do the Fable 5 and Sol benchmarks disagree?

Mostly because the two vendors publish different benchmarks. Anthropic leads with SWE-bench Verified and SWE-bench Pro, which measure resolving real GitHub issues in real repos. OpenAI leads with Terminal-Bench 2.1, which measures completing tasks in a terminal environment. Each vendor showcases the benchmark family it wins. The only cross-vendor signal we have on a shared benchmark is third-party SWE-bench Pro runs, which favor Fable 5 by a wide margin, and those are not OpenAI-published numbers.

Which is cheaper, Fable 5 or Sol?

Sol, clearly. Sol costs $5 per million input tokens and $30 per million output tokens versus Fable 5's $10 and $50: half price on input, 40% cheaper on output. A story consuming 500k input and 100k output tokens costs about $10.00 on Fable 5 and $5.50 on Sol.

Can I use both models on the same project?

Yes, and dual-tool setups are mainstream now: OpenAI even ships a Codex plugin for Claude Code. AIDEN takes the orchestration route: it runs your existing Claude Code and Codex CLIs side by side on one kanban board, each story on its own git branch, so you can assign Fable 5 to one story and Sol to another in the same project.

What is ultra mode in GPT-5.6 Sol?

Ultra mode is a Sol-only capability that runs parallel subagents natively, on top of Sol's exclusive "max" reasoning effort level. OpenAI's launch materials report Terminal-Bench 2.1 rising from 88.8% to 91.9% with ultra mode enabled. The other GPT-5.6 tiers (Terra, Luna) do not have it.

Does Sol beat Claude on SWE-bench?

No, not on any published run we have verified. OpenAI has not published SWE-bench numbers for Sol; third-party SWE-bench Pro runs place Sol at 64.6% versus Fable 5's 80.3%. Treat that as provisional, both models are weeks old, but it is the current state of the evidence.

Claude Fable 5 vs GPT-5.6 Sol: The Flagship Match-Up

Quick answer

Head-to-Head: The Verified Specs

The Benchmark Problem: Two Vendors, Two Stories

Ship your first agent today

Cost Math: What a Story Actually Costs

When to Pick Which

Pick Claude Fable 5 for

Pick GPT-5.6 Sol for

Or Run Both on One Board

FAQ

Keep reading

AI models for coding: the hub

Claude Fable 5 for coding

GPT-5.6 Sol for coding

Best Claude model for coding

Best Codex model

AIDEN vs Codex CLI

Why choose? Run both.