Devin rules and context cost
Project rules in Devin Desktop and Devin CLI load into agent turns when triggered. always_on rules are the most common hidden input tax — full rule text on every message.
On cloud Devin, persistent instructions live in Knowledge and repo AGENTS.md — Session Insights flags misleading Knowledge that wastes ACUs on wrong assumptions.
Hub: Tokenminning in Devin. Queries: devin global rules, rule activation modes.
Activation modes
From Memories & Rules :
| Mode | trigger: | Context cost |
|---|---|---|
| Always On | always_on | Full rule every message |
| Model Decision | model_decision | Description always; body on demand |
| Glob | glob | Only when matching files touched |
| Manual | manual | Only when @rule-name mentioned |
Prefer glob or model_decision over always_on.
Global and enterprise rules
Audit these the same way as project rules:
- Global:
~/.codeium/windsurf/memories/global_rules.md - Enterprise system rules injected for all users
- Workspace cap: 12,000 characters; global cap: 6,000 characters
Devin global rules queries usually mean this stack — trim or convert to glob triggers.
AGENTS.md
Use AGENTS.md for directory-scoped instructions instead of pasting style guides into chat.
- One concern per rule file
- Reference linter configs instead of duplicating style in prose
- Do not duplicate content across rules,
AGENTS.md, and auto-memories - Prefer Rules over Memories for team knowledge (memories are local, not version-controlled)
Knowledge (cloud)
| Mechanism | Scope | Cost pattern |
|---|---|---|
| Knowledge | Org-wide, auto-recalled when relevant | Bad items mislead entire sessions — review Knowledge Usage tab in Session Insights |
| Playbooks | Reusable task prompts | Lower rewrite cost for repeat workflows |
| AGENTS.md (repo) | Directory-scoped | Onboarding guide |
Trim Knowledge like rules: one concern per item, specific triggers, delete stale entries after refactors.
Index bloat
Rules are not the only input source — tune .devinignore / .codeiumignore and Max Workspace Size so retrieval does not attach irrelevant files. See Devin Desktop Ignore .