Claude Fable 5.1 is the strongest alternative to Claude Mythos 5.1 — it matches it on coding (100/100) at $10/1M input (Claude Mythos 5.1 costs $10/1M). Claude Opus 4.8 is the budget swap: $5/1M input is 50% cheaper. Kimi K3 is the top open-weight option if you want a model you can self-host.
The shortest way to see the safest default, the lower-cost option, and the specialist pick before you read deeper.
Claude Fable 5.1 is the safest overall answer here when you want the strongest default instead of the lowest list price.
Grok 4.5 is the lower-cost option to start with when you still need useful output at scale.
Claude Mythos 5.1 is the better pick when response speed matters more than maximum reasoning depth.
Claude Fable 5.1 matches Claude Mythos 5.1 on coding (100/100) at $10/1M input tokens.
Claude Opus 4.8 cuts input cost by 50% ($5 vs $10/1M) while scoring 100/100 on coding.
Kimi K3 is open-weight — self-host it or run it via low-cost API providers at $3/1M input.
Choose Claude Fable 5.1 when you want the closest overall replacement — it targets frontier agentic coding, long-horizon autonomous work, and agentic scientific research.
Choose Claude Opus 4.8 when token volume matters more than peak quality — it is 50% cheaper on input.
Staying with Anthropic? Claude Fable 5.1 is the strongest in-house switch at $10/1M input.
Switch the scoring lens to see whether the top answer changes when you care more about cost, speed, or long-document work.
Anthropic / Premium / Sep 1, 2026
New frontier leader — better than Fable 5 on every published benchmark, and cheaper to run.
Ranks models by the broadest mix of coding, writing, research, and long-context usefulness.
You need low latency, or your workload is uncached and cost-sensitive — Claude Opus 5 is half the base price and within a few points on agentic coding.
The fastest way to see where the recommendation shifts when your priority changes.
Fable 5.1 with the safeguards lifted — partner-only, 60.9% Terminal-Bench 4.0.
New frontier leader — better than Fable 5 on every published benchmark, and cheaper to run.
Best value premium coder — frontier-grade at half of Fable 5's price.
Closest Chinese challenger to the frontier — #4 overall on intelligence.
Superseded by Fable 5.1 — still 80.3% SWE-Bench Pro, but 5.1 is better and cheaper to run.
Every figure below is the provider's list price or a published capability score — the same numbers the recommendation on this page is built from.
| Model | Input | Output | Est. month | Context | Speed | Coding | Writing | Research |
|---|---|---|---|---|---|---|---|---|
| Claude Fable 5.1Anthropic | $10.00/1M | $50.00/1M | $200 | 1M tokens | Deliberate | 100 | 98 | 100 |
| Claude Mythos 5.1Anthropic | $10.00/1M | $50.00/1M | $200 | 1M tokens | Deliberate | 100 | 97 | 99 |
| Claude Opus 4.8Anthropic | $5.00/1M | $25.00/1M | $100 | 1M tokens | Deliberate | 100 | 96 | 98 |
| Kimi K3Moonshot | $3.00/1M | $15.00/1M | $60 | 1M tokens | Deliberate | 96 | 90 | 93 |
Capability scores are out of 100 and reflect our own weighting of published benchmarks and production signals — see how we evaluate models. “Est. month” assumes 10M input and 2M output tokens at list price, with no batch or caching discounts applied, so treat it as a ceiling.
What each one is genuinely good at, where it falls down, and the situations we would steer you away from it — not just the headline score.
Anthropic's September 1, 2026 frontier release and the new capability ceiling for coding, agents, and scientific work. Base pricing is unchanged at $10/$50, but cache reads dropped 75% to $0.25/1M — roughly 25% cheaper on typical workloads and up to 45% cheaper on agentic ones. 1M context, 128K output, adaptive thinking always on.
You need low latency, or your workload is uncached and cost-sensitive — Claude Opus 5 is half the base price and within a few points on agentic coding.
The new frontier leader, and the rare upgrade that costs less than the model it replaces. Base $10/$50 pricing did not move, but a 75% cut to cache reads makes typical workloads ~25% cheaper than Fable 5 and heavily agentic ones ~45% cheaper — while more than doubling Fable 5 on agentic science and beating Opus 5 on agentic coding. If you were already on Fable 5, switching is a straight win. If you were on Opus 5 for the price, it still costs 2x on uncached tokens.
Released September 1, 2026 alongside Claude Mythos 5.1, the first update to the Mythos-class line since Fable 5 on June 9. API ID claude-fable-5-1; generally available on the Claude API, Amazon Bedrock, Google Cloud, and Microsoft Foundry. Published launch numbers (Fable 5.1 / Fable 5 / Opus 5 / GPT-5.6 Sol): Terminal-Bench-Science 0.1 52.6 / 24.7 / 29.0 / 22.4; Terminal-Bench 4.0 55.8 / 42.0 / 52.3 / 37.3; CursorBench 3.2.0 73.4 / 70.5 / 70.0 / 67.2; AutomationBench 31.4 / 17.1 / 26.9 / 19.6; OSWorld 2.0 strict 41.7 / 36.1 / 39.6; Humanity's Last Exam (no tools) 60.9 / 57.8 / 56.6; GDPval-AA v2 1853 / 1723 / 1824 / 1711. GDPval-AA v2 is rescaled from the v1 numbers quoted on the Fable 5 page and is not directly comparable to them.
The unrestricted twin of Claude Fable 5.1 — the same model with safeguards lifted in high-risk areas, released September 1, 2026 to vetted cybersecurity and life-sciences organisations under Anthropic's trusted-access programme. Scores 60.9% on Terminal-Bench 4.0, the highest agentic-coding result Anthropic has published.
You don't hold vetted trusted access, or your work never trips Fable 5.1's safeguards — the two models are otherwise identical.
The highest published agentic-coding score anywhere — 60.9% on Terminal-Bench 4.0 — but you almost certainly cannot get it. Mythos 5.1 is Fable 5.1 with safeguards lifted, gated to vetted cybersecurity and life-sciences organisations. Unless you hold trusted access and hit refusals that block real research, Fable 5.1 is the same model at the same price.
Released September 1, 2026 alongside Claude Fable 5.1, continuing the Mythos-class line that began with Project Glasswing's April 2026 private preview. Access is limited to vetted US cybersecurity and life-sciences professionals. Same underlying model, pricing, context window, and cache-read discount as Fable 5.1; the only published difference is the safeguard level and the resulting Terminal-Bench 4.0 score (60.9% vs 55.8%).
Anthropic's newest Opus flagship — 69.2% SWE-Bench Pro, 88.6% SWE-Bench Verified, 1890 Arena Elo (121 pts ahead of GPT-5.5), and native parallel subagents. Same $5/$25 price as Opus 4.7.
You need the highest possible coding ceiling (Fable 5 / Mythos 5), low-latency responses, or a workflow locked to OpenAI tooling.
The best value at the premium tier now that Claude Fable 5 leads on raw capability. 69.2% SWE-Bench Pro, 1890 Elo, and built-in parallel subagents at $5/$25 — half the price of Fable 5. The smart default for serious coding when you don't need the absolute frontier.
Launched May 27, 2026. Available on Claude API, AWS Bedrock, Google Vertex AI, Microsoft Foundry, and GitHub Copilot. Fast mode available at $10/$50 per 1M tokens.
Moonshot's 2.8-trillion-parameter multimodal reasoning flagship with always-on thinking — the largest open-weight model ever released and the closest Chinese challenger to the Western frontier.
You need fast responses or predictable output costs — always-on thinking burns tokens.
The first Chinese model to genuinely crowd the Western frontier — #4 on aggregate intelligence ahead of Opus 4.8. The always-on thinking makes it slow and output-heavy, so cost per task runs above the sticker price. A serious Opus-class alternative if latency isn't critical.
Released July 16, 2026; open weights July 26. Cache-hit input $0.30/1M. Subscriptions: Adagio (free) to Vivace $199/mo; full 1M context only on Allegro ($99) and up. New signups paused July 19 near GPU capacity, reopening in batches.
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Claude Fable 5.1 is the strongest overall alternative. It scores 100/100 on coding (Claude Mythos 5.1: 100/100) and costs $10/1M input vs $10/1M. New frontier leader — better than Fable 5 on every published benchmark, and cheaper to run.
Claude Opus 4.8 at $5/1M input — 50% cheaper than Claude Mythos 5.1's $10/1M. It scores 100/100 on coding, so expect a quality step down on the hardest tasks.
Yes — Kimi K3 is the strongest open-weight replacement for Claude Mythos 5.1, scoring 96/100 on coding against Claude Mythos 5.1's 100/100. You can self-host it or run it through hosted APIs at $3/1M input (Claude Mythos 5.1 costs $10/1M), with no per-seat subscription. Self-hosting trades the licence saving for infrastructure you have to run, so it pays off at sustained volume rather than for occasional use.
Claude Fable 5.1 — same provider, same API surface, $10/1M input vs $10/1M. New frontier leader — better than Fable 5 on every published benchmark, and cheaper to run.
The highest published agentic-coding score anywhere — 60.9% on Terminal-Bench 4.0 — but you almost certainly cannot get it.