# Anthropic — Claude Sonnet 4.5

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This file is the record of one model version: what the model registry states
about it, Anthropic's launch post, the first-party posts this record
holds about it, the outlets that reported on those posts, and other companies'
announcements that it runs on their platforms. A model ranks nothing here and
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- This model's page: https://forck.live/models/claude-sonnet-4-5
- Anthropic's page: https://forck.live/company/anthropic
- Every model: https://forck.live/models
- Catalogue: https://forck.live/llms.txt

## Model

- Name: Claude Sonnet 4.5
- Company: Anthropic (anthropic.com)
- Launch post: not held by this record
- Announced: not stated
- Launch source: not stated
- Launch chosen by: not stated
- Released (per models.dev): 2025-09-29
- Listed (per OpenRouter): 2025-09-29
- Open weights: no
- Posts about it: 0
- Outlets named under its posts: 0
- OpenRouter id: anthropic/claude-sonnet-4.5 — https://openrouter.ai/anthropic/claude-sonnet-4.5

## Posts about it

_Anthropic's own posts whose title names Claude Sonnet 4.5, and its launch post, in the record's order: dated newest first, undated last. The record reads the newest 50 first-party posts mentioning the model, every company's together, so a model mentioned more often than that lists the newest of them._

_This record holds no first-party post about Claude Sonnet 4.5 yet._

## Who reported on it

_This record names no outlet that reported on these posts._

## Where it runs

_Other companies' own announcements naming Claude Sonnet 4.5 and Anthropic — each is that company's post, not Anthropic's._

### Vercel — Collaborating with Anthropic on Claude Sonnet 4.5 to power intelligent coding agents

- Company: Vercel (vercel.com)
- Announced: 2025-09-29T13:00:00+00:00
- Category: availability-change
- Coverage: not counted
- Announcement: yes
- Group: announcements
- Source: https://vercel.com/blog/collaborating-with-anthropic-on-claude-sonnet-4-5
- Record: https://forck.live/items/20813-collaborating-with-anthropic-on-claude-sonnet-4-5-to-power-intelligent-coding
- Subject: v0 / AI SDK / AI Gateway

Vercel made Anthropic's Claude Sonnet 4.5 available on its AI Gateway and AI SDK, and released an open-source Coding Agent Platform template that defaults to using the model. Internal evaluations showed the model outperformed its predecessor on Next.js builds, linting, and feature implementation tasks.

### Amp — Now Using Claude Sonnet 4.5

- Company: Amp (ampcode.com)
- Announced: 2025-09-29
- Category: capability-change
- Coverage: not counted
- Announcement: yes
- Group: announcements
- Source: https://ampcode.com/news/claude-sonnet-4-5
- Record: https://forck.live/items/7802-now-using-claude-sonnet-4-5
- Subject: Amp

Amp has switched its primary model to Claude Sonnet 4.5, the latest release from Anthropic. The company reports improvements in coding tasks such as reduced sycophancy, higher success rates for file edits, and improved reasoning during debugging. The switch is automatic for users who update to the latest release of Amp's VS Code extension or CLI.

### Cognition — Rebuilding Devin for Claude Sonnet 4.5: Lessons and Challenges

- Company: Cognition (cognition.com)
- Announced: 2025-09-29
- Category: capability-change
- Coverage: not counted
- Announcement: yes
- Group: announcements
- Source: https://cognition.com/blog/devin-sonnet-4-5-lessons-and-challenges
- Record: https://forck.live/items/7691-rebuilding-devin-for-claude-sonnet-4-5-lessons-and-challenges
- Subject: Devin / SWE

Cognition rebuilt Devin for Claude Sonnet 4.5, resulting in a 2x faster and 12% better performance on Junior Developer Evals. The new version is available in Agent Preview, while the old version remains available. The post details observations about the model's awareness of its context window, note-taking behavior, and parallel tool execution.

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Catalogue: https://forck.live/llms.txt
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