Devin Desktop (Windsurf) rules: where it lives and how tools read it

Devin Desktop, the new name for Windsurf since 2026-06-02, reads rule files from .devin/rules/ and still accepts .windsurf/rules/ and the legacy .windsurfrules. Each rule's trigger decides whether it is always on, matched by glob, chosen by the model or called manually.

Where it lives

• Workspace: .devin/rules/*.md (preferred) or .windsurf/rules/*.md (fallback).
• Legacy single file: .windsurfrules at the workspace root, still read.
• Global: ~/.codeium/windsurf/memories/global_rules.md, always on.
• AGENTS.md in any directory.
• System (Enterprise): /Library/Application Support/Devin/rules/*.md, /etc/devin/rules/*.md or C:\ProgramData\Devin\rules\*.md.

Format

Markdown; workspace rules start with YAML frontmatter. trigger is always_on, model_decision, glob or manual, with globs for glob rules and description for model_decision. global_rules.md is capped at 6,000 characters and each workspace rule file at 12,000.

Frontmatter keys: triggerglobsdescription

---
trigger: glob
globs: **/*.test.ts
---

# Test files

- Use Vitest and import describe, it and expect explicitly.
- Test one behaviour per case and name it in plain English.
- Mock network calls with the helpers in test/mocks/.
- Never call real payment APIs from a test.

Precedence and merging

.devin/ takes precedence over .windsurf/. System rules merge with workspace and global rules without overriding them, and global_rules.md and the root AGENTS.md are always on. Rules are discovered in the workspace, its subdirectories and parent directories up to the git root.

Tools that read it

Tips

• Create new rules in .devin/rules/; keep .windsurf/rules/ only for older installs.
• Use trigger: model_decision with a clear description for guidance the agent should pull in only when relevant.
• Auto-generated Memories apply only to the legacy Cascade agent, not to Devin Local, which is now the default.

Other instruction files