Claude Opus 4.8
Legacy (still served)
Superseded by Claude Opus 5.5. Status per Anthropic docs on 2026-09-30: active/legacy, retirement not sooner than 2027-05-28.
by Anthropic. Released 2026-05-28.
| API ID | claude-opus-4-8 (Bedrock anthropic.claude-opus-4-8) |
| Context / output | 1M tokens / 128K (300K on Batches API with beta header) |
| Thinking | adaptive (default effort high) |
| Knowledge cutoff | Jan 2026 |
| Platforms | Claude API, Bedrock, Google Cloud, Microsoft Foundry, Claude Platform on AWS |
Shares the current tokenizer introduced with Opus 4.7 (1M tokens is about 555k words); non-default temperature/top_p/top_k are rejected on Claude 4.7 and later. Opus 4.8 is also the model that Fable 5’s safety classifiers route declined requests to, and the replacement Anthropic named for retired Opus 4 and Opus 4.1.
Earlier: Opus 4.7, Opus 4.6. See anthropic-claude for the full lineup.
Merged from laptop copy (2026-10-01)
Video-coverage notes from the owner’s earlier version of this note (laptop copy; claims come from channel summaries, not vendor docs, so treat as unverified):
| Date | Event |
|---|---|
| 2026-05-24 | Leaks alongside Sonnet 4.8 and Mythos 1 |
| 2026-07 | Widely available; noted as “acting like Opus 5” in capability |
| 2026-08 | Displaced in benchmark coverage by Qwen 3.8 Max, Muse Spark 1.2, Ornith 1.5 |
Opus 4.8 became the de-facto reference point for “frontier” during summer 2026, the model open-weight releases measured themselves against. Coverage is dominated not by Anthropic’s own launch material but by challengers claiming to match or beat it, usually at far lower cost: Qwen 3.8 Max, Muse Spark 1.2 (Meta), DeepSeek V4 Flash via OpenCode, and Ornith 1.5. By August 2026 matching Opus 4.8 was table stakes for open-weight models, and the differentiator had shifted to price and local runnability.
Part of the Claude Opus 4 series; see also Claude Fable 5.
Sources
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https://platform.claude.com/docs/en/models/opus-4-8/overview (accessed 2026-09-30)
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https://platform.claude.com/docs/en/about-claude/models/overview (accessed 2026-09-30)
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https://platform.claude.com/docs/en/about-claude/model-deprecations (accessed 2026-09-30)