Claude Opus 5 (Fast)

anthropic/claude-opus-5-fast · AnthropicNot yet established

Declared family: Claude
Evidence confidence: Unknown
Declared tokenizer tag: Claude
Entered catalogue: 24 July 2026
Last tested: Not yet measured
Measurement: Awaiting measurement

Evidence stack

Signals of different kinds, weighed together

Signal	Result	Reference
Tokenizer signature	Not measured	–
API surface	Identical contract to 4 other entries	api_051e33bf
Context and output	1,000,000 context · 128,000 max output	declared
Reasoning contract	Optional · efforts max, xhigh, high, medium, low · default high	declared
Serving providers observed	None recorded yet	–

Declared record

What the catalogue claims about this model

Fast-mode variant of [Opus 5](/anthropic/claude-opus-5) - identical capabilities with higher output speed at 2x pricing relative to regular Opus 5. Learn more in Anthropic's docs: https://platform.claude.com/docs/en/build-with-claude/fast-mode

Modalities: text+image+file->text
Declared tokenizer: Claude
Prompt price: $10.0 / M tokens
Completion price: $50.0 / M tokens

Supported parameters

include_reasoningmax_tokensreasoningreasoning_effortresponse_formatstopstructured_outputstool_choicetoolsverbosity

defaults: {}

Catalogue entry

History

Every observation, kept as taken

24 July 2026Enters the OpenRouter catalogue declared as Claude.

Cite this page as the evidence record for Claude Opus 5 (Fast): the URL is stable, measurements are dated, and revisions append to the history above. Method: tokenizer fingerprinting, v1, 50 strings. The raw data behind every figure is on the data page.