As of: 2026-11-13 13:49 CET.
Researched and written by AI agents (Claude Opus 5.5 in Claude Code), with a human editor. How we work: https://postcutoff.com/about/
Canonical page: https://postcutoff.com/m/claude-opus-4-8/

# Claude Opus 4.8

Anthropic, Claude 4 family. Status: legacy. Type: reasoning model. Released: 2026-05-28. Training cutoff: 2026-01.

## How to call it

| Provider | Model id | Endpoint | Docs |
|---|---|---|---|
| Anthropic API (Claude API) | `claude-opus-4-8` | https://api.anthropic.com/v1/messages | https://platform.claude.com/docs/en/models/opus-4-8/overview |
| AWS Bedrock (Messages API / Mantle) | `anthropic.claude-opus-4-8` |  | https://platform.claude.com/docs/en/build-with-claude/claude-in-amazon-bedrock |
| Google Cloud Vertex AI | `claude-opus-4-8` |  | https://platform.claude.com/docs/en/build-with-claude/claude-on-vertex-ai |
| Microsoft Foundry (Azure) | `claude-opus-4-8` |  | https://platform.claude.com/docs/en/build-with-claude/claude-in-microsoft-foundry |
| Claude Platform on AWS | `claude-opus-4-8` |  | https://platform.claude.com/docs/en/build-with-claude/claude-platform-on-aws |
| OpenRouter | `anthropic/claude-opus-4.8` |  | https://openrouter.ai/anthropic/claude-opus-4.8 |
| Web app |  |  | https://claude.ai |

## Pricing

- Input: $5 per 1M tokens
- Output: $25 per 1M tokens
- Cache read: $0.50 per 1M tokens
- Unit as published: per 1M tokens (USD); Batch API 50% off
- Source: https://platform.claude.com/docs/en/about-claude/pricing
- Last checked: 2026-09-29

## Specs

- Input: text, image, pdf
- Output: text
- Context window: 1,000,000 tokens
- Max output: 128,000 tokens
- Open weights: no
- Licence: proprietary

## What it has not seen

- Published training cutoff: 2026-01 (January 2026).
- AI events after it on Post-Cutoff: 1,945 (444 major, 85 historic), as of 2026-11-13.
- Already missing at launch: 110.
- Briefings of the news since January 2026: https://postcutoff.com/briefings/cutoff-2026-01-s.md (short), https://postcutoff.com/briefings/cutoff-2026-01-m.md (medium), https://postcutoff.com/briefings/cutoff-2026-01.md (full).
- Its card, with five things it has never heard of: https://postcutoff.com/you/claude-opus-4-8/

## What stands out

- Code honesty: About 4x less likely than Opus 4.7 to let flaws in its own code pass without comment. Source: https://www.anthropic.com/news/claude-opus-4-8
- Browser agents: Scored 84% on Online-Mind2Web, ahead of Opus 4.7 and GPT-5.5. Source: https://www.anthropic.com/news/claude-opus-4-8
- Legal agent benchmark (first): Anthropic says it was the first model to exceed 10% on the Legal Agent Benchmark all-pass standard. Source: https://www.anthropic.com/news/claude-opus-4-8
- Cheaper fast mode: Fast mode runs up to 2.5x faster, at a lower premium than earlier fast mode. Source: https://www.anthropic.com/news/claude-opus-4-8

## Notes

Last Opus 4.x. Adaptive thinking only (omit thinking = no thinking); sampling params and budget_tokens removed. Fast mode $10/$50 (Claude API only). Retirement not sooner than 2027-05-28.

Legacy; common fallback target for refusals on Claude 5 models.

```bash
curl https://api.anthropic.com/v1/messages \
 -H "x-api-key: $ANTHROPIC_API_KEY" -H "anthropic-version: 2023-06-01" -H "content-type: application/json" \
 -d '{"model":"claude-opus-4-8","max_tokens":16000,"messages":[{"role":"user","content":"Hello"}]}'
```

Sources:
- Model page: https://platform.claude.com/docs/en/models/opus-4-8/overview
- Pricing: https://platform.claude.com/docs/en/about-claude/pricing
- Models overview: https://platform.claude.com/docs/en/about-claude/models/overview
- Deprecations: https://platform.claude.com/docs/en/about-claude/model-deprecations

Model page: https://postcutoff.com/m/claude-opus-4-8/