User-facing permission presets through ctx.permission (PermissionService). Each configured name bundles sandbox/mode with approval/policy; the defaults are workspace-write (workspace-write + ask) and danger-full-access (danger-full-access + never). UI adapters may expose the table as one selector, while sandbox execution and approval continue to consume their own knobs.

set(session, name) records a changed selection in a log-only permission/preset event, then calls each knob's setter only when its effective value changes. The selection event precedes the knob events and preserves user intent when presets share a bundle; a net-zero selection appends nothing. current(events) prefers a still-matching recorded selection, then the first matching table entry, and otherwise returns custom. Clients may display custom as the current value, but cannot select it.

The service requires a confining ctx.bash executor and ctx.approval. A table entry named custom throws at load; composition defaults outside the table instead make a zero-event session derive custom. See the sandbox switching design.

Model Experience

Indirectly, through dsh-user-approval and dsh-tool-bash, which render the approval-policy prompt, switch notice, and sandboxed tool outcomes selected by this service's knob events; permission/preset itself is log-only.

KV Cache effect

No direct invalidation; the named consumer owns any request-prefix changes.

Known Limitations and Deferred Work

No shipped composition currently mounts the service — the ACP bridge was its only selector before ACP became automation-only; the preset table is kept for the interactive front door that next exposes a runtime policy switch.
Only two mechanism knobs are bundled — presets select sandbox mode and approval policy; an agent/profile choice is not part of PresetSpec yet.
custom is derived-only — callers can switch away from an unmatched knob combination but cannot target or persist a named custom preset through this service.
The preset table is process-level — configuration is fixed for the plugin lifetime; changing available presets requires reloading the plugin.