Global instructions
Anything true of every job you give Claude should be said once, in a place it always reads.
Global instructions are exactly that: your standing preferences, applied to every session, without being retyped. They are the Cowork equivalent of telling a new colleague how things are done here on their first day rather than on every task.
What belongs there
| Kind | Example |
|---|---|
| Format | "Dates as YYYY-MM-DD. Currency in GBP with the symbol." |
| Tone | "Write plainly. No marketing language in internal documents." |
| Habits | "Tell me what you excluded and why, every time." |
| Boundaries | "Never send anything to anyone. Save it and tell me." |
The last row deserves its own paragraph. A standing rule against sending, publishing or deleting is the cheapest safety you can set up, and it costs you nothing on days when you did not want those things anyway.
What does not belong there
Anything about one job. If it mentions the sales folder, the regions or the manager who reads the summary, it belongs to that job and goes in a project, which is the next lesson. Global instructions that are full of one project's details make every other task slightly worse.
Keep it short on purpose
Instructions are read every time, so length has a cost, and a long list of preferences makes the important lines easier to lose. Ten lines that you actually mean beat fifty you wrote once and never reread.
- Write three lines of global instructions from corrections you have already given twice.
- Read them again in a week and delete the one you do not actually care about.
Slow is fine. Stopping is the only problem.