# Notes, lessons and claims > How agents share what they learn through DMN: notes in each project's .dmn folder, your rules, the briefing a session starts with, lessons from fixed errors, past sessions, and file claims. Source: https://getdmn.com/docs/notes/ ## Notes A note is a short markdown file in the project's `.dmn/memories` folder. Agents write them as they learn something worth keeping: why a test is flaky, which file owns a setting, a decision you made. Every agent on the project can read them, whichever vendor it comes from. ```markdown --- name: stripe-webhook-raw-body description: The Stripe webhook must read the raw body before any JSON parsing --- Stripe signs the raw request body. The handler in app/api/stripe/route.ts reads request.text() first; parsing JSON before verifying breaks the signature check. ``` Agents use `dmn memory` or the `memory` tool. You can read and edit the files like any others, or in the Memory view beside the Fleet panel. | Command | What it does | |---|---| | `dmn memory list` | The project's notes | | `dmn memory read ` | One note | | `dmn memory write --content ""` | Write a note, replacing any note at that path | | `dmn memory delete ` | Delete one | Notes sit alongside `CLAUDE.md`, `AGENTS.md` and Claude Code's auto memory rather than replacing them. [Claude Code's memory between sessions](/guides/claude-code-memory-between-sessions/) compares them. ## Your rules A rule is a note you mark with `kind: rule` in its front matter. Rules come first in every briefing, before any agent's notes, so use them for what every agent must know: how you want tests run, what never to touch. ```markdown --- name: no-force-push description: Never force-push; open a new branch instead kind: rule --- ``` ## The briefing *Diagram: What a new session is told, in order. All of it comes from your machine.* A session starts with a briefing built from the project's files. Claude Code gets it from the hook `dmn hook-init` installs, at the start of each session and again after it compacts its context. Codex gets it from its own hook, and agents connected over MCP get it with DMN's server instructions. A note whose code has been deleted, or changed in a commit since the note was written, is flagged, so an old note isn't taken for a current one. ## Lessons When agents in two or more sessions hit the same error and fix it the same way, DMN turns that into a lesson: the error, and a one-line fix. Lessons come from your Claude Code and Codex session logs, read on your machine with recognised secrets removed. - The briefing lists them, so a new session knows them from the start. - In Claude Code, when a command fails and matches a lesson, the hook hands the agent the fix straight away. - `dmn gotchas list` shows them, and `dmn gotchas forget ` stops one for good. The command line calls lessons gotchas. ## Past sessions `dmn memory search ""` searches dated records of earlier sessions: what each was asked, what it ran and what it concluded. Use it when you remember that something was done, but not where. ## Claims Before an agent edits, it can claim the files or folders it's about to change, with a reason and an expiry (30 minutes unless it asks for longer, up to eight hours). Other agents check claims before they edit, and see who holds a file and why. Claims are advisory. They never block a write: they're there so parallel agents can see each other, not to lock anything. Agents use the `lease` tool for them; you don't manage anything.