Claude Sonnet 5.5

anthropic/claude-sonnet-5-5 is Anthropic's successor to Claude Sonnet 5 for well-scoped everyday work — building features, fixing bugs, drafting and review. It keeps Sonnet 5's $2 / $10 per million input / output rates and 1M-token context window, adds 128K max output, and runs adaptive thinking on by default at high effort. Bring your own Anthropic key, or route through OpenRouter or Cline BYOK — your key, your quota.

• App code — Vercel AI SDK or OpenAI SDK.
• Coding agent — anyr claude / anyr opencode / anyr codex (playbook).
• No code — playground.

Moving from Claude Sonnet 5? Five behavior changes affect existing code — up-front thinking between tool calls, forced tool use, thinking blocks tied to the producing model, and text between tool calls arriving inside thinking blocks. Start with Anthropic's migration guide.

Try it in the Vercel AI SDK. createAnyRouter() reads ANYROUTER_API_KEY:

import { createAnyRouter } from "@anyr/ai-sdk-provider"
import { generateText } from "ai"

const anyrouter = createAnyRouter()

const { text } = await generateText({
  model: anyrouter("anthropic/claude-sonnet-5-5"),
  prompt: "Summarize this diff in three bullets.",
})
console.log(text)

Or launch a coding agent through the anyr CLI:

curl -fsSL https://anyrouter.dev/setup.sh | bash
anyr login
anyr claude --model "anthropic/claude-sonnet-5-5"

More: AI SDK · OpenAI SDK · coding agents.