Claude Opus 5.5 Fast
claude-opus-5-5-fastclaude-opus-5.5-fastopus-5-5-fast- ⚡ Same Opus 5.5 model served with a faster inference configuration
- 📏 Full 1M-token context window, up to 128K output tokens
- 🧠 Adaptive thinking that cannot be fully disabled on 5.5
- 👁️ Vision plus text inputs, text output
- 🔧 Tool calling and structured outputs supported
- 🎯 Built for long-running agentic coding and knowledge work
- 🏢 Anthropic's Opus line; Fast is an opt-in serving mode
- 🆕 Successor to the Opus 5 Fast serving tier in the same family
Anthropic PBC is an American artificial intelligence company headquartered in San Francisco. Structured as a public benefit corporation, the lab develops large language models under the Claude name, with a research emphasis on building reliable, steerable, and safety-focused AI…
Explore 16 more models by Anthropic →Claude Opus 5.5 Fast is a speed-optimized serving tier for Anthropic's Opus 5.5 model rather than a separate model. Anthropic's platform documentation describes fast mode as the same model with a faster inference configuration, with no change to intelligence or capabilities; on the Claude API it is enabled through a speed setting together with a fast-mode beta header.
It exposes the same specification as Claude Opus 5.5: a 1M-token context window served by default with no beta header, up to 128K output tokens (300K via a Batch API beta), vision, tool calling, and adaptive thinking that cannot be turned off.
Against its direct predecessor, Claude Opus 5 Fast, any capability change is inherited from the base generation rather than from the serving tier itself, since both tiers simply run the corresponding Opus model on a faster path. Anthropic's migration guide is aimed at users moving from Claude Opus 5 and notes behavioural differences to account for, and it also documents that Claude Opus 4.7 rejects fast-mode requests entirely.
Practically, the Fast tier suits latency-sensitive interactive coding and agent loops where wall-clock time matters more than per-token efficiency; for batch or throughput-driven workloads, the standard Opus 5.5 endpoint is the more natural default, as are lighter siblings such as Claude Sonnet 5 or Claude Fable 5.1 where full Opus-class reasoning is not required.
This About section is AI-generated from public sources via VeniceStats + Venice inference, with no human editing. It may contain inaccuracies.
| Seller | Reputation↓ | Routing | Input $/M | Cached $/M | Output $/M | Categories | API |
|---|---|---|---|---|---|---|---|
| ▲ Apex Ant 0x73b4…e736 | 71.90 | #1 | $4.80 | $0.24 | $24.00 | chat,agents,coding,reasoning,vision,multimodal,long-context,premium,fast | openai-chat-completions |
| D5V1N2 0xd5e7…7be0 | 67.45 | #2 | $9.20 | $0.50 | $46.00 | chat,coding,agent,reasoning,vision,fast,large-context,frontier,claude,router,fallback | openai-chat-completions |
| Fire Ant 🔥🐜 0xbe05…bc5d | 50.00 | gated | $7.7723 | $0.3886 | $38.8613 | — | — |
"Best price" and the seller table are live AntSeed catalog data (advertised $/1M tokens — or $ per generated image for unit-billed image models — not settled amounts). Reputation = buyer trust score (0-100, the AntSeed SDK's own formula). "Routing" = the SDK's default buyer routing (what the VPR desktop app ships with): a trust ≥ 60 gate on the effective reputation, then cheapest-first among routable sellers; live failover state (per-peer cooldowns) is buyer-side runtime and not included. Model knowledge (TLDR, provider, About) via the VeniceStats enrichment layer. Advertised catalog, not the model used in any specific purchase. "Usage on AntSeed" counts only settlements whose buyers share the per-model split on-chain (metadata v2/v3, opt-in), so every usage figure is a lower bound.