Anthropic released Claude Opus 4.8 on May 28, 2026, positioning it as a quality upgrade over Opus 4.7 with no change to pricing, context window, or model class.1 The practical implication for teams already using Opus 4.7 via the direct API: the same budget buys a more capable model, and nothing needs to change in the invoice.
The tier picture changed on June 9, 2026, when Anthropic released Claude Fable 5, a new Mythos-class model that sits above Opus at $10 per million input tokens and $50 per million output: the same rate as Opus 4.8’s fast mode, buying a more capable model rather than a faster one. [Updated June 2026] On June 12, 2026, Anthropic suspended access to both Fable 5 and Mythos 5 worldwide following a US government export-control directive tied to a reported jailbreak; Opus 4.8 and all other models were unaffected. Opus 4.8 therefore remains the highest-capability model currently available. Teams relying on the $5/$25 tier should treat the comparison below as the operative choice until Fable 5 access is restored.
What is Opus 4.8
Opus 4.8 is Anthropic’s Opus-tier flagship, accessible via the API model ID claude-opus-4-8.2 It carries a 1M token context window (200k on Microsoft Foundry), supports up to 128k output tokens (up to 300k via Batch API beta header), and has a knowledge cutoff of January 2026.2
The model ships in two modes. Standard mode bills at $5 per million input tokens and $25 per million output tokens, matching Opus 4.7’s price exactly.1 Fast mode bills at $10 per million input and $50 per million output, delivers roughly 2.5x the throughput, and is according to Anthropic three times cheaper than previous fast modes for the same speed tier.1
How Opus 4.8 compares to Opus 4.7 on benchmarks
Anthropic published head-to-head numbers across seven evaluations.1 The table below covers each one, with competitor figures where published:
| Benchmark | Opus 4.8 | Opus 4.7 | GPT-5.5 | Gemini 3.1 Pro |
|---|---|---|---|---|
| SWE-Bench Pro (agentic coding) | 69.2% | 64.3% | 58.6% | 54.2% |
| Terminal-Bench 2.1 | 74.6% | 66.1% | 78.2% | 70.3% |
| Humanity’s Last Exam, no tools | 49.8% | 46.9% | 41.4% | 44.4% |
| Humanity’s Last Exam, with tools | 57.9% | 54.7% | 52.2% | 51.4% |
| OSWorld-Verified (computer use) | 83.4% | 82.8% | 78.7% | 76.2% |
| GDPval-AA (knowledge work, score) | 1890 | 1753 | 1769 | 1314 |
| Finance Agent v2 | 53.9% | 51.5% | 51.8% | 43.0% |
Two results warrant attention. On SWE-Bench Pro, Opus 4.8’s 69.2% leads every listed competitor by a wide margin; GPT-5.5 reaches 58.6% and Gemini 3.1 Pro 54.2%.1 On Terminal-Bench 2.1, Opus 4.8 scores 74.6% vs. Opus 4.7’s 66.1%, but GPT-5.5 leads this benchmark at 78.2%.1 Opus 4.8 does not top every benchmark.
Anthropic also published an Online-Mind2Web browser agent figure of 84% for Opus 4.8, without a corresponding Opus 4.7 figure in the same release.1
What did not change
Price, context, and output length are identical to Opus 4.7. The standard $5/$25 per million token rate is unchanged.1 The 1M input context window and 128k output limit carry forward.2 Teams that budgeted against Opus 4.7 for agentic workflows can substitute Opus 4.8 without adjusting cost models.
The model class is also unchanged. Opus 4.8 remains the Opus-tier flagship, above Sonnet and Haiku in capability and above both in per-token cost. It was designed to sit below the Fable 5 tier introduced June 9, 2026, but Fable 5 and Mythos 5 were suspended June 12 via US export-control directive — making Opus 4.8 the highest-capability model currently accessible to API callers. Opus 4.8 is not deprecated or replaced.5
Why Anthropic’s quality claims matter for code reliability
Anthropic states Opus 4.8 is four times less likely than Opus 4.7 to allow flaws in code.1 This claim covers the model’s behavior when reviewing or producing code containing potential vulnerabilities, not just its benchmark ranking. In agentic coding contexts, where the model may complete hundreds of file edits in a single session without human review of each change, a fourfold reduction in code-flaw pass-through is a structural shift in how much oversight a safe workflow requires.
Anthropic also describes Opus 4.8 as more likely to flag uncertainties, less likely to make unsupported claims, showing sharper judgment, and able to work independently for longer.1 These properties are relevant to multi-step agentic tasks where the model decides how to proceed without constant human prompting.
What shipped alongside Opus 4.8
Three related items released with or around the Opus 4.8 launch.1
Dynamic workflows (Claude Code research preview): Claude Code can run hundreds of parallel subagents in a single session, enabling workloads that previously required orchestrating separate API calls.
Effort control: Users can choose how much effort Claude applies to a task. The default is high on all surfaces.2
Claude Mythos Preview: An invitation-only research preview for defensive cybersecurity, associated with Project Glasswing.2 Claude Mythos 5, released June 9, 2026, now fills this role for Glasswing partners.
What Opus 4.8 costs relative to the alternatives
At standard API rates, the cost comparison is straightforward:
| Model | Input (per M tokens) | Output (per M tokens) | Context |
|---|---|---|---|
| Claude Fable 5 | $10.00 | $50.00 | 1M |
| Opus 4.8 (standard) | $5.00 | $25.00 | 1M |
| Opus 4.8 (fast mode) | $10.00 | $50.00 | 1M |
| Opus 4.7 | $5.00 | $25.00 | 1M |
| Sonnet 4.6 | $3.00 | $15.00 | 1M |
| Haiku 4.5 | $1.00 | $5.00 | 200k |
Fable 5 and Mythos 5 are listed for reference; both were suspended June 12, 2026 following a US export-control directive. Access to all other rows above is unaffected. [Updated June 2026]
Standard Opus 4.8 and Opus 4.7 are priced identically.1 Fast mode doubles the input cost and doubles the output cost in exchange for roughly 2.5x throughput. Whether that tradeoff makes sense depends on whether your workflow is latency-bound or cost-bound. For batch jobs that can queue overnight, standard mode preserves the same cost floor as Opus 4.7. For real-time agentic loops where turn latency matters, fast mode costs twice as much per token but completes each turn in less than half the time.
The fast mode price also deserves context: Anthropic calls it three times cheaper than it was for previous models at equivalent speed.1 Teams that evaluated earlier fast tiers and rejected them on cost grounds should re-check the current numbers. Note that Claude Fable 5 carries the same $10/$50 per-token rate as Opus 4.8 fast mode but delivers the Mythos-class capability tier rather than higher throughput.5 Fable 5 access was suspended June 12, 2026; until it is restored, the fast mode’s $10/$50 rate remains the only path to that price point — at Opus-tier capability rather than Mythos-tier.
Frequently Asked Questions
Does Opus 4.8 replace Opus 4.7, or do both remain available?
Anthropic has not announced a deprecation timeline for Opus 4.7. Both model IDs remain callable via the API. Opus 4.1 retires August 5, 2026; Opus 4.7, 4.6, and 4.5 remain listed as active legacy models. Teams should check the models overview page for current status.2
Is there a published SWE-bench Verified figure for Opus 4.8?
No. Anthropic’s Opus 4.8 release uses SWE-Bench Pro (69.2%) as its headline coding benchmark. There is no published SWE-bench Verified figure for Opus 4.8 in the release materials.1
How does the 1M context window change on Microsoft Foundry?
On Microsoft Foundry, the context window is 200k tokens rather than 1M.2 The reduction applies only to the Foundry deployment path; direct Anthropic API access retains the full 1M context.
What does the Batch API beta header extend for output tokens?
The standard max output is 128k tokens. With the Batch API beta header, output can extend up to 300k tokens per request.2 This applies to batch workloads, not synchronous API calls.
Where does Opus 4.8 rank on Terminal-Bench 2.1 vs. competitors?
Opus 4.8 scores 74.6% on Terminal-Bench 2.1, above Opus 4.7 (66.1%) and Gemini 3.1 Pro (70.3%), but below GPT-5.5 (78.2%).1 GPT-5.5 leads this particular benchmark.
What happened to Claude Fable 5 and Mythos 5 three days after launch?
On June 12, 2026 — three days after launch — Anthropic disabled both Fable 5 and Mythos 5 for all customers worldwide following a US Commerce Department export-control directive.6 The directive prohibited foreign nationals from accessing either model. Anthropic stated it believed the government’s concern — a narrow potential jailbreak involving asking the model to review a codebase for vulnerabilities — did not represent a serious risk, and described the technique as identifying only a small number of previously known, minor vulnerabilities. Anthropic said it was working to restore access.
The practical effect for teams evaluating Opus 4.8 against a higher-capability tier: that higher tier is currently unavailable. Opus 4.8 is the highest-capability Claude model currently accessible via API. The broader implications of the Fable 5 and Mythos 5 access suspension — including who retains Glasswing access and under what conditions — are covered in a separate analysis.
Does the Fable 5 suspension affect Opus 4.8 access or pricing?
No. Anthropic explicitly stated that access to all other models, including Opus 4.8, Sonnet 4.6, and Haiku 4.5, remains unaffected by the directive. Pricing and API availability for Opus 4.8 are unchanged. Teams using Opus 4.8 do not need to take any action.
How does Opus 4.8’s fast mode relate to the Claude Code fast mode?
Claude Code’s fast mode, which routes work through Opus 4.8, is a distinct product from the API’s fast-mode billing tier. For a detailed breakdown of what the Claude Code fast mode enables and whether the 6× price step over standard usage is justified for different workflow types, see Claude Code fast mode: is the 6× pricing worth it.
