Industry

Claude Opus 5: what actually changed, and who should switch

Claude Opus 5 shipped July 24, 2026 at $5 per million input tokens and $25 per million output — the same price as Opus 4.8, and exactly half of Claude Fable 5. It is now the default model on Claude Max and the strongest model available on Claude Pro, and it is live on the Claude API, Amazon Bedrock, Google Cloud and Microsoft Foundry. Opus 4.8 stays available everywhere. If you use Claude Code daily, the short version is: switch, then spend twenty minutes cleaning up your prompts, because Opus 5 changes some defaults you have probably been relying on without noticing.

Pricing, side by side

The dashes are gaps in the published comparison, not zeros — Anthropic's pricing page documents caching and context tiers per model family, and the Fable 5 rows we can't source we've left blank rather than guessed. If you want the cost of a specific workload rather than a rate card, the cost calculator takes tokens per session and gives you a monthly number.

Two pricing details matter more than the headline. The minimum cacheable prompt dropping from 1,024 to 512 tokens means short system prompts that silently failed to cache on Opus 4.8 now cache with no code change at all. And 1M context being both the default and the maximum, with no long-context surcharge, removes the tier-jump math that made big-repo sessions hard to budget.

The effort ladder, correctly described

Launch coverage in the mainstream press framed Opus 5 around a new "low, medium, high" toggle that trades cost against capability. That is the claude.ai consumer surface, and it undersells what developers actually get. The API and Claude Code expose five effort levels — low, medium, high, xhigh and max — with high as the default.

Effort is also not new. It has existed since Opus 4.5 and is available on Fable 5, Sonnet 5, Sonnet 4.6, and the Opus 4.6/4.7/4.8 line. The five-level ladder is not new either — xhigh arrived with Opus 4.7, so 4.7 and 4.8 already expose all five. What is genuinely new is Anthropic's claim that Opus 5 "converts additional effort into better results more reliably than any earlier Opus model." That reliability is the part worth testing on your own work: on earlier models, cranking effort often bought thinking tokens without buying a better answer.

One caveat that bites in agent loops: effort controls thinking volume, not response length. Turning effort down does not reliably produce shorter visible output. If you want terse answers, say so in the prompt.

Fast mode: 2.5x throughput at 2x price

Fast mode is a separate lever. On Opus 5 and Opus 4.8 it delivers up to 2.5x higher output tokens per second, billed at $10/$50 per million — precisely double the standard rate. The arithmetic works out in your favour on throughput per dollar, but only for the right workload.

The constraints are real. It is a research preview, so access is limited. It is Claude API only, not Bedrock, Google Cloud, or Microsoft Foundry. It needs the fast-mode-2026-02-01 beta header plus speed: "fast". And the gain is in output tokens per second, not time to first token — so a long refactor generation feels dramatically faster and a one-line answer feels identical.

The benchmarks, with the right attribution

The most defensible result is ARC-AGI-3, because ARC Prize administered it rather than taking Anthropic's word. Opus 5 at high effort scored 30.16% (reported as 30.2%), an ARC Prize Verified result dated July 24. The previous high was GPT-5.6 Sol at roughly 7.8%; Opus 4.8 at high effort scored about 1.5%. ARC Prize also noted Opus 5 cleared five Public Demo environments no model had previously beaten. On the older benchmarks at max effort, also verified: 97.5% on ARC-AGI-1 and 90.4% on ARC-AGI-2 semi-private.

A roughly 4x jump over the prior best on an independently administered reasoning benchmark is the single most interesting number of this launch. It is also a reasoning benchmark, not a coding one, and ARC results have historically transferred to real work unevenly.

On coding, Anthropic's own claims are mostly qualitative. Its announcement says Opus 5 "surpasses all other models" on Frontier-Bench and "more than doubles Opus 4.8's performance at a lower cost per task." The specific figures circulating — roughly 43% for Opus 5, 33.7% for Fable 5, 18.7% for Opus 4.8 — appear only as chart images on that page, so every numeric citation traces to a third party reading a chart. Treat them as vendor-reported and chart-derived. Reports also disagree about which effort level produced the Opus 5 figure, and we have seen no effort attribution from Anthropic, so don't attach one.

Anthropic's other launch claims are worth quoting exactly because they are unusually specific about cost rather than score: on CursorBench 3.2 at max effort Opus 5 "performs within 0.5% of Fable 5's peak score, but at half the cost per task"; on Zapier AutomationBench its pass rate is "around 1.5x the next-best model for the same cost per task"; on OSWorld 2.0 it surpasses Fable 5's best result "at just over a third of the cost." All three are vendor-reported.

You may see a 96.0% SWE-bench Verified figure attributed to Opus 5. It is widely repeated in secondary coverage, but it does not appear on Anthropic's announcement page or in the docs we checked. Third-party reporting, not a vendor claim.

What changes in daily Claude Code use

Three defaults flipped, and all three will quietly change your sessions.

• Thinking is on by default. On Opus 4.8, a request with no thinking field ran without thinking; the identical request on Opus 5 runs adaptive thinking. Because max_tokens is a hard cap on thinking plus response text combined, workloads that ran thinking-off with a tight max_tokens can now truncate mid-answer. Raise the cap.
• thinking: {"type": "disabled"} is only valid at effort high or below. Combine it with xhigh or max and you get a 400. Opus 4.8 accepted that pairing. The check runs per request, not per conversation.
• Opus 5 delegates to subagents more readily than Opus 4.8 — the opposite direction from 4.8, which needed nudging to delegate at all. Any "delegate more" guidance in your project instructions should come out, and a spawn cap should go in. Worth a pass over your CLAUDE.md before you switch.

Two behavioural regressions to watch. Opus 5's default responses and written deliverables run longer than Opus 4.8's, and as noted, lowering effort won't fix that — prompt for length. And it verifies its own work unprompted, so carried-over "double-check your answer" instructions cause visible over-verification. Delete them.

On the plumbing side: max output is 128k, and the knowledge cutoff is May 2026 — four months newer than Fable 5's January 2026, which matters if you work with fast-moving libraries. Opus 5 also gets its own rate-limit bucket, separate from the combined pool shared by Opus 4.8, 4.7, 4.6 and 4.5, with Fast mode carrying dedicated limits on top. In practice that means switching to Opus 5 gives you headroom you didn't have — useful context if you've been running into usage limits.

When Fable 5 is still worth double the price

Anthropic's own framing answers this more honestly than most marketing does: Opus 5 lands within 0.5% of Fable 5's peak on CursorBench at max effort. Within 0.5% is not ahead. If your work is dominated by a small number of genuinely hard calls where the top half-percent decides whether you lose an afternoon, Fable 5 still holds the peak on at least that benchmark, and the price math can justify it. Fable 5 is also the model to keep if you've already tuned prompts and workflows around its behaviour and can't afford a migration window.

For everything else — long agent runs, repo-wide refactors, anything where cost per task compounds across hundreds of turns — halving the input and output rate while gaining a newer cutoff, a bigger default context, cheaper caching and a separate rate-limit bucket is a straightforward win. The same logic that made cheaper challengers interesting applies here, only now the cheaper option is from the same lab.

And the honest answer stays what it always is: benchmarks don't run on your repo. Give both models the same five real tasks from your git history and blind-score the output. That takes an hour and beats every chart on this page.

Frequently asked questions

Where Backgrind fits

Backgrind is not a model and not an agent — it's a desktop overlay for macOS and Windows that PTY-wraps the CLI you already run (Claude Code, Cursor, Codex) or a hosted model, floats over any app including borderless-fullscreen games, and pings you only when the agent needs a decision or finishes. That makes a model migration cheap to evaluate: put Opus 5 in one tab and Opus 4.8 or Fable 5 in another, fire the same task at both, and read the results when they land instead of watching two terminals. In BYO-CLI mode your agent's content never touches our servers — the overlay renders and forwards, nothing more. Live mode adds phone and browser control when you're away from the desk.

Sources

Launch and qualitative claims: Anthropic — Introducing Claude Opus 5. Defaults, breaking changes and limits: What's new in Claude Opus 5, Models overview and Rate limits. Pricing: Claude API pricing. Effort levels: Effort. Fast mode: Fast mode. ARC results: ARC Prize — Claude Opus 5 verified results. Frontier-Bench numbers are vendor-reported by Anthropic and published only as chart images; the numeric values here come from third parties reading those charts.