Documentation / @agentick/kernel / createGuard

Function: createGuard()

Call Signature

createGuard(fn): Middleware

Defined in: kernel/src/guard.ts:69

Create a guard middleware from a predicate function.

The guard runs before the procedure handler:

• If the fn returns true, execution continues.
• If the fn returns false, a GuardError is thrown (using config for the message).
• If the fn throws a GuardError, it propagates directly (full control).

Parameters

fn

GuardFn

Returns

Middleware

Examples

const adminOnly = createGuard(
  (envelope) => envelope.context.user?.roles?.includes("admin") ?? false,
);

const roleGuard = createGuard({
  name: "role-guard",
  guardType: "role",
  reason: (envelope) => `User ${envelope.context.user?.id} lacks required role`,
}, (envelope) => {
  return envelope.context.user?.roles?.includes("admin") ?? false;
});

const roleGuard = createGuard({ name: "role-guard" }, (envelope) => {
  const userRoles = envelope.context.user?.roles ?? [];
  const required = ["admin", "moderator"];
  if (!required.some(r => userRoles.includes(r))) {
    throw GuardError.role(required);
  }
  return true;
});

Call Signature

createGuard(config, fn): Middleware

Defined in: kernel/src/guard.ts:70

Create a guard middleware from a predicate function.

The guard runs before the procedure handler:

• If the fn returns true, execution continues.
• If the fn returns false, a GuardError is thrown (using config for the message).
• If the fn throws a GuardError, it propagates directly (full control).

Parameters

config

GuardConfig

fn

GuardFn

Returns

Middleware

Examples

const adminOnly = createGuard(
  (envelope) => envelope.context.user?.roles?.includes("admin") ?? false,
);

const roleGuard = createGuard({
  name: "role-guard",
  guardType: "role",
  reason: (envelope) => `User ${envelope.context.user?.id} lacks required role`,
}, (envelope) => {
  return envelope.context.user?.roles?.includes("admin") ?? false;
});

const roleGuard = createGuard({ name: "role-guard" }, (envelope) => {
  const userRoles = envelope.context.user?.roles ?? [];
  const required = ["admin", "moderator"];
  if (!required.some(r => userRoles.includes(r))) {
    throw GuardError.role(required);
  }
  return true;
});