2026-09-22T00:00:00.000ZAnthropic · NewsFor builders

Introducing Claude Opus 5.5

Opus 5.5 performs at the level of Claude Fable 5.1 on most work and costs 40% less to run than Opus 5.

Why it matters

Anthropic published a model update. If you use a hosted chat, read the source before you assume your usual model changed.

What you can do

Claude Fable 5.1 is on the cloud board. List cost is $10 in and $50 out per million tokens.

For builders

Try Claude Fable 5.1. Copy the OpenRouter call.

Copy

curl https://openrouter.ai/api/v1/chat/completions \
  -H "Authorization: Bearer $OPENROUTER_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model":"anthropic/claude-fable-5.1","messages":[{"role":"user","content":"Hello"}]}'

Open the source

See Claude Fable 5.1 See Claude Opus 5.5 Plan a job from this

Introducing Claude Opus 5.5

Updated just now

Opus 5.5 performs at the level of Claude Fable 5.1 on most work and costs 40% less to run than Opus 5.

Why it matters

Anthropic published a model update. If you use a hosted chat, read the source before you assume your usual model changed.

What you can do

Claude Fable 5.1 is on the cloud board. List cost is $10 in and $50 out per million tokens.

For builders

Try Claude Fable 5.1. Copy the OpenRouter call.

Copy

curl https://openrouter.ai/api/v1/chat/completions \
  -H "Authorization: Bearer $OPENROUTER_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model":"anthropic/claude-fable-5.1","messages":[{"role":"user","content":"Hello"}]}'

Open the source

See Claude Fable 5.1 See Claude Opus 5.5 Plan a job from this

Introducing Claude Opus 5.5

Why it matters

What you can do

For builders

Copy

Tags

Introducing Claude Opus 5.5

Why it matters

What you can do

For builders

Copy

Tags