/**
 * `registerSystemOfUse` — runtime extension point for the E9 system-of-use
 * taxonomy (T11751 · AC1).
 *
 * ## Why a runtime registry
 *
 * {@link BUILTIN_SYSTEMS_OF_USE} is the static, closed-axis registry of the
 * well-known systems (orchestration tiers + roles + aux subsystems). Plugins,
 * extensions, and downstream packages need to declare NEW systems-of-use (e.g.
 * a `tool:my-search` or a bespoke `aux`-like subsystem) and give each a default
 * provider/model binding — WITHOUT editing the contracts SSoT.
 *
 * `registerSystemOfUse(key, displayName, defaults)` adds such a system to a
 * process-level registry. The registered default binding is consulted by the
 * single E9 resolution chokepoint (`resolveLLMForSystem` → `resolveLLMForRole`)
 * **strictly BELOW user config** — after `llm.systems[key]`, `llm.default`, and
 * `llm.defaultProfile` — so the user ALWAYS wins (AC1). A registered default
 * only supplies a binding when the user has configured nothing for that key.
 *
 * ## Import-time purity
 *
 * This module performs NO registration at import time — the registry starts
 * empty and is populated only by explicit `registerSystemOfUse(...)` calls. It
 * holds no I/O, no config reads, and no side effects on load (so importing it
 * is always safe). It is the runtime half intentionally split out of the
 * type-only `@cleocode/contracts` (Gate 10).
 *
 * @module llm/system-of-use-registry
 * @task T11751
 * @epic T11745
 */
import { type RegisteredSystemOfUse, type SystemOfUseDefaults, type SystemOfUseKind, type SystemOfUsePickerEntry } from '@cleocode/contracts';
import { formatSystemKey } from './system-key.js';
/**
 * A registered system-of-use whose `defaults` carry neither a `profile` nor a
 * complete `provider`+`model` tuple is structurally incomplete: it can declare
 * presence in the picker but cannot supply a resolution binding. Such a default
 * is skipped at resolution time (the chain falls through) — never an error.
 *
 * @param defaults - The candidate default binding.
 * @returns `true` when the default can actually bind a provider/model.
 * @task T11751
 */
export declare function isResolvableSystemDefault(defaults: SystemOfUseDefaults): boolean;
/**
 * Register a new system-of-use with a default provider/model binding (AC1).
 *
 * The registration is merged UNDER user config: the resolver consults
 * `defaults` only when the user has configured nothing more specific for `key`
 * (no `llm.systems[key]`, no `llm.default`, no `llm.defaultProfile`). Re-calling
 * with the same `key` REPLACES the prior registration (last-write-wins) so a
 * package can update its own default idempotently.
 *
 * `key` MAY be a flat label (e.g. `'sentient'`) or an open-axis encoded key
 * (`'tool:web-search'`). Passing a structured `SystemOfUse` descriptor is also
 * supported via {@link registerSystemOfUseDescriptor}.
 *
 * @param key         - Encoded system-of-use key (non-empty).
 * @param displayName - Human-readable name for the picker surface (non-empty).
 * @param defaults    - Default binding consulted strictly below user config.
 * @returns The stored {@link RegisteredSystemOfUse} record.
 * @throws {RangeError} When `key` or `displayName` is empty.
 * @task T11751
 * @epic T11745
 */
export declare function registerSystemOfUse(key: string, displayName: string, defaults: SystemOfUseDefaults): RegisteredSystemOfUse;
/**
 * Register a system-of-use from a structured {@link SystemOfUse} descriptor,
 * encoding it to its canonical string key via {@link formatSystemKey}.
 *
 * Convenience wrapper over {@link registerSystemOfUse} for callers that already
 * hold a `{ kind, id }` descriptor (e.g. plugin-declared tools/skills).
 *
 * @param system      - The structured descriptor to register.
 * @param displayName - Human-readable name for the picker surface.
 * @param defaults    - Default binding consulted strictly below user config.
 * @returns The stored {@link RegisteredSystemOfUse} record.
 * @task T11751
 */
export declare function registerSystemOfUseDescriptor(system: Parameters<typeof formatSystemKey>[0], displayName: string, defaults: SystemOfUseDefaults): RegisteredSystemOfUse;
/**
 * Look up the runtime-registered default binding for an encoded system key.
 *
 * Returns `undefined` when no system is registered under `key` OR when its
 * default is structurally incomplete (so the resolver falls through). This is
 * the read surface the E9 resolver calls AFTER exhausting all user-config tiers.
 *
 * @param key - Encoded system-of-use key (may be undefined — returns undefined).
 * @returns The resolvable {@link SystemOfUseDefaults}, or `undefined`.
 * @task T11751
 */
export declare function getRegisteredSystemDefault(key: string | undefined): SystemOfUseDefaults | undefined;
/**
 * Enumerate every system-of-use for the TUI / Studio profile picker (AC2):
 * the static {@link BUILTIN_SYSTEMS_OF_USE} table followed by every
 * runtime-registered system, de-duplicated by key (a registration for a builtin
 * key overrides the builtin entry — "user/runtime wins" for the picker label).
 *
 * Each entry carries its encoded `key`, a `displayName`, the discriminant
 * `kind`, and its `source` (`'builtin'` | `'registered'`) so the picker can
 * render and group them. Registered entries also surface their `defaults`.
 *
 * @param kind - Optional kind filter — when set, only that axis is returned.
 * @returns The merged, ordered picker entries.
 * @task T11751
 * @epic T11745
 */
export declare function listSystemsOfUse(kind?: SystemOfUseKind): SystemOfUsePickerEntry[];
/**
 * Clear all runtime registrations.
 *
 * Intended for test isolation — production code never needs to un-register a
 * system. Builtins are unaffected (they live in the contracts SSoT, not here).
 *
 * @internal
 * @task T11751
 */
export declare function clearRegisteredSystemsOfUse(): void;
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