/**
 * Conservative, fail-CLOSED structural value equality — the SINGLE canonical
 * implementation shared by the two determinism-critical equality gates of the
 * Claims runtime. Both gates need the IDENTICAL notion of "are these two values
 * provably the same proposition, or do they CONTRADICT?", so the helper lives
 * here ONCE rather than being duplicated per gate (a one-sided edit to two
 * verbatim copies would silently diverge two determinism-critical decisions):
 *
 *   - **P2 `SAME_TYPE_VALUE_CONFLICT`** (`./consistency.ts`): does a
 *     same-`(subject, type)` pair assert the SAME value (an idempotent duplicate
 *     read) or CONTRADICT (→ ESCALATE)?
 *   - **H3 same-key ledger conflict** (`./evidence-ledger.ts`): does a second
 *     write to an evidence key DISAGREE with the first (→ `UNKNOWN`) or is it an
 *     idempotent re-read?
 *
 * **INTERNAL to `@adjudicate/core`.** This module is deliberately NOT added to
 * the `claims/index.ts` barrel (no `export * from "./value-equality.js"`), so it
 * is never re-exported from the package entry — the frozen public API surface
 * stays byte-identical (§Q "do not widen the frozen public API"). Sharing a
 * PRIVATE module between two in-package consumers does not widen the API; only a
 * barrel re-export would. Pure & self-contained — no clock/RNG/IO, no
 * kernel-downstream import (§R kernel purity: `adjudicate → claustrum →
 * ibatexas`, never backward).
 */
/**
 * Is `o` a PLAIN object — i.e. one whose prototype is `Object.prototype` or
 * `null` (an object literal / `Object.create(null)`)? A `Date`/`Map`/`Set`/class
 * instance is NOT plain (its prototype is some other constructor's). Used by
 * `sameValue` to refuse structural comparison of exotics it cannot safely equate.
 */
export declare function isPlainObject(o: object): boolean;
/**
 * CONSERVATIVE, fail-CLOSED structural equality for two values — returns `true`
 * ONLY when the two values are PROVABLY equal (primitives via `Object.is`; arrays
 * and PLAIN objects compared structurally, recursively); it returns `false`
 * whenever equality cannot be established. Failing to `false` is the SAFE
 * direction for BOTH gates: an un-equatable pair is treated as a CONTRADICTION
 * (P2 `SAME_TYPE_VALUE_CONFLICT` → ESCALATE; H3 same-key conflict → `UNKNOWN`),
 * never silently rendered as a duplicate / missed conflict.
 *
 * NaN is treated as equal-to-NaN here (`Object.is` already does this) — a re-read
 * of a NaN-valued field is not a conflict. `+0` and `-0` are treated as the SAME
 * value (an idempotent re-read, not a contradiction). `canonicalJson` is
 * deliberately NOT used here (it throws on `NaN`).
 *
 * **Non-plain objects are REJECTED (R1 conservative fail-closed):** a
 * `Date`/`Map`/`Set`/class instance that is not reference-identical (`Object.is`
 * already short-circuited that) returns `false`, because own-enumerable-key
 * compare would FALSELY equate distinct exotics — e.g. two different `Date`s each
 * expose zero own enumerable keys, so a naive own-key compare returns `true` and
 * MISSES the conflict. Rejecting them surfaces the conflict.
 */
export declare function sameValue(a: unknown, b: unknown): boolean;
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