diff --git a/src/components/DiffCard.tsx b/src/components/DiffCard.tsx
index 841b804..24f6a58 100644
--- a/src/components/DiffCard.tsx
+++ b/src/components/DiffCard.tsx
@@ -9,10 +9,20 @@ export type DiffData = CanonicalDiffData;
 export interface DiffCardProps {
 	/** The diff data to visualize. */
 	diff: DiffData;
-	/** Called when the user accepts the change. */
-	onAccept?: (diffId: string) => void;
-	/** Called when the user rejects the change. */
-	onReject?: (diffId: string) => void;
+	/**
+	 * Called when the user accepts the change.
+	 *
+	 * Receives the pending-action id (`diff.actionId`, falling back to
+	 * the deprecated `diff.diffId` for older payloads).
+	 */
+	onAccept?: (actionId: string) => void;
+	/**
+	 * Called when the user rejects the change.
+	 *
+	 * Receives the pending-action id (`diff.actionId`, falling back to
+	 * the deprecated `diff.diffId` for older payloads).
+	 */
+	onReject?: (actionId: string) => void;
 	/** Whether the accept/reject action is in progress. */
 	loading?: boolean;
 	/** Additional CSS class name. */
@@ -32,13 +42,14 @@ type DiffCardStatus = 'pending' | 'accepted' | 'rejected';
  * ```tsx
  * <DiffCard
  *   diff={{
- *     diffId: 'abc123',
+ *     actionId: 'abc123',
+ *     diffId: 'abc123', // kept for back-compat; same value as actionId
  *     diffType: 'edit',
  *     originalContent: 'Hello world',
  *     replacementContent: 'Hello universe',
  *   }}
- *   onAccept={(id) => apiFetch({ path: `/resolve/${id}`, method: 'POST', data: { action: 'accept' } })}
- *   onReject={(id) => apiFetch({ path: `/resolve/${id}`, method: 'POST', data: { action: 'reject' } })}
+ *   onAccept={(id) => apiFetch({ path: '/actions/resolve', method: 'POST', data: { action_id: id, decision: 'accepted' } })}
+ *   onReject={(id) => apiFetch({ path: '/actions/resolve', method: 'POST', data: { action_id: id, decision: 'rejected' } })}
  * />
  * ```
  */
@@ -58,14 +69,19 @@ export function DiffCard({
 		className,
 	].filter(Boolean).join(' ');
 
+	// Prefer `actionId` (canonical since v0.11). Fall back to `diffId`
+	// for payloads produced by older parsers or consumers that still
+	// construct `CanonicalDiffData` by hand without setting `actionId`.
+	const resolvedId = diff.actionId || diff.diffId;
+
 	const handleAccept = () => {
 		setStatus('accepted');
-		onAccept?.(diff.diffId);
+		onAccept?.(resolvedId);
 	};
 
 	const handleReject = () => {
 		setStatus('rejected');
-		onReject?.(diff.diffId);
+		onReject?.(resolvedId);
 	};
 
 	const diffHtml = renderDiff(diff);
diff --git a/src/diff.ts b/src/diff.ts
index 3457101..29c30ec 100644
--- a/src/diff.ts
+++ b/src/diff.ts
@@ -14,6 +14,25 @@ export interface CanonicalDiffEditorData {
 }
 
 export interface CanonicalDiffData {
+	/**
+	 * Pending-action id the backend assigned when staging this preview.
+	 *
+	 * This is the canonical field as of v0.11 — it aligns with the
+	 * unified "pending action" primitive on the server side (any tool
+	 * invocation can be staged + previewed + resolved through the same
+	 * /actions/resolve endpoint, not just content diffs).
+	 */
+	actionId: string;
+	/**
+	 * Back-compat alias for `actionId`.
+	 *
+	 * Always populated with the same value as `actionId`. Kept so
+	 * consumers that wired against the v0.7–v0.10 `diffId` field keep
+	 * working through one more major version. New code should read
+	 * `actionId`.
+	 *
+	 * @deprecated Use `actionId`.
+	 */
 	diffId: string;
 	diffType: CanonicalDiffType;
 	originalContent: string;
@@ -74,13 +93,23 @@ export function parseCanonicalDiff( value: unknown ): CanonicalDiffData | null {
 	const container = isRecord( value.data ) ? value.data : value;
 	const rawDiff = isRecord( container.diff ) ? container.diff : container;
 
-	const diffId = typeof rawDiff.diffId === 'string'
-		? rawDiff.diffId
-		: typeof rawDiff.diff_id === 'string'
-			? rawDiff.diff_id
-			: typeof container.diff_id === 'string'
-				? container.diff_id
-				: '';
+	// Resolve the pending-action id. Prefer the canonical `actionId`
+	// (server unified on pending-action vocabulary in mid-2026) and
+	// fall back to the historical `diffId` / `diff_id` shapes so
+	// older backends and stored payloads keep rendering.
+	const resolvedId = typeof rawDiff.actionId === 'string'
+		? rawDiff.actionId
+		: typeof rawDiff.action_id === 'string'
+			? rawDiff.action_id
+			: typeof container.action_id === 'string'
+				? container.action_id
+				: typeof rawDiff.diffId === 'string'
+					? rawDiff.diffId
+					: typeof rawDiff.diff_id === 'string'
+						? rawDiff.diff_id
+						: typeof container.diff_id === 'string'
+							? container.diff_id
+							: '';
 
 	const diffType = rawDiff.diffType === 'replace' || rawDiff.diffType === 'insert'
 		? rawDiff.diffType
@@ -102,7 +131,7 @@ export function parseCanonicalDiff( value: unknown ): CanonicalDiffData | null {
 			? rawDiff.replacement_content
 			: '';
 
-	if ( ! diffId && ! originalContent && ! replacementContent ) {
+	if ( ! resolvedId && ! originalContent && ! replacementContent ) {
 		return null;
 	}
 
@@ -129,7 +158,8 @@ export function parseCanonicalDiff( value: unknown ): CanonicalDiffData | null {
 		: undefined;
 
 	return {
-		diffId,
+		actionId: resolvedId,
+		diffId: resolvedId,
 		diffType,
 		originalContent,
 		replacementContent,