editing-cordis-compositions

# Editing Cordis compositions Every capability in this harness is a plugin row in a `cordis.yml`. There is no separate configuration language: changing what an agent can do means changing which rows are composed for it. ## Off-limits **Never edit, delete, or overwrite a preset that ships with the deployment** — the `agent-presets` directory beside the deployment's own config, which supplies `standard`, `code`, `minimal`, and `cordis`. Never escalate the sandbox to reach it, even when a change there looks quicker. An upgrade overwrites that install, and corrupting `cordis` disables preset authoring itself. Reading a shipped composition is the intended way to start; writing to one is not, and neither is editing the host composition to work around a preset limitation. To change what a shipped preset does, copy it and edit the copy. Locally authored presets under the user root are yours to create, edit, and delete. ## Decide the plane first Two planes, and the choice is not about how "agent-related" something feels — it is about whether the thing must be shared. **Host composition.** The registries themselves (`tools`, `systemPrompt`, `agents`, `agent-loop`, `sessions`), anything crossing sessions (persistence, session query, storage, settings, credentials, telemetry), the sandbox and approval stack, the model route, and the subagent registry with its spawn/fork backends. One instance for the process. **Agent preset.** What one session contributes to those registries: its...