sec-default

The security default for organizations. Function hooks give every plugin a say on every event, in chain order, and the plugins a person installs sit in the user tier, beneath the organization's prepend tier and above its append tier. Some of what an organization sets today (its classic hooks, its managed CLAUDE.md and rules, its settings, its MCP allowlist) was never within a person's reach before function hooks; seated outermost, this plugin keeps exactly those out of the user tier's reach and adds no policy of its own. Everything else passes through untouched.

It has three moves and nothing else: continue past the user tier (next.to(e, "append")), refuse a user-tier caller by name ({ deny } when next.origin.tier is user), or pass (next(e)). A subject's provenance is the event's pinned e.provider; policy is read through $.settings.read({ source: "policy" }), one read serving a burst; both fail closed, so an unreadable policy counts as a policy in force.

hooks/register.ts is the module; hooks/policy/ reads the managed settings it decides by.

The rows

event	from the outermost seat
classic.*	Continue past the user tier: the organization's settings hooks see the engine's input and their answer stands.
prompt.section, prompt.context, skill.prompt, attribution.text	Continue past the user tier: managed CLAUDE.md, rules and policy skills reach the model as written. A person's plugins keep prompt.submit and its additive context.
settings.read	Continue past the user tier: no user hook rewrites what any caller reads as settings, this plugin's own policy reads included.
tool.describe, command.describe, agent.offer, agent.spawn	When the subject's pinned e.provider.tier is prepend or append (a policy-installed plugin, the managed folder, a policy MCP server), continue past the user tier; a subject provided by user, builtin or core passes.
tool.register	A caller in prepend or append continues past the user tier. A user-tier caller is refused by name while managed settings hold allowedMcpServers (set at all, empty included); otherwise it passes.
tool.list	The tools of the organization's managed MCP servers are listed as the organization's tiers listed them; every other tool as the user tier left it. With no policy to read, or a refusal from either listing, the organization's listing stands whole.
everything else	Passes: prompt.submit, turn.*, tool.call, tool.check, command.run, command.register, session.*, ui.*, fs.*, http.fetch, process.run, store.*, clock.*, model.*, mcp.call, audio.*, agent.list, engine.create.

What it hooks

classic.*, prompt.section, prompt.context, skill.prompt, attribution.text, settings.read, tool.describe, command.describe, agent.offer, agent.spawn, tool.register, tool.list.

What it calls on $

settings.read. It continues to the append tier with next.to, which only a plugin in a managed tier may do.

Where it is seated

The CLI seats it first in the prepend tier wherever hooks modules load on a machine with managed settings or for a Team or Enterprise organization, unless managed settings define prependPlugins: then that list is the whole prepend tier, and the organization names sec-default@builtin in it at the position it wants, e.g. "prependPlugins": ["acme-guard@acme-tools", "sec-default@builtin"], or leaves it out. It is a plugin folder like any other, but its one move that matters, next.to, is refused outside a managed tier, so loading it with --plugin-dir seats a plugin that can only pass.