# 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
- Models affected: Claude Sonnet 4.5, Sonnet 3.6

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.

## Evidence

Verbatim from https://cognition.com/blog/devin-sonnet-4-5-lessons-and-challenges:

> We rebuilt Devin for Claude Sonnet 4.5. The new version is 2x faster, 12% better on our Junior Developer Evals, and it's available now in Agent Preview.

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Record: https://forck.live/items/7691-rebuilding-devin-for-claude-sonnet-4-5-lessons-and-challenges
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