2 files changed, 32 insertions, 1 deletions
diff --git a/src/adapters/ws/logic.test.ts b/src/adapters/ws/logic.test.ts
index 546afe1..2784295 100644
--- a/src/adapters/ws/logic.test.ts
+++ b/src/adapters/ws/logic.test.ts
@@ -64,6 +64,29 @@ describe("parseServerMessage", () => {
 		});
 	});
 
+	it("preserves the conversationId echo on a scoped surface message", () => {
+		const data = JSON.stringify({
+			type: "surface",
+			spec: { id: "s1", region: "r", title: "S1", fields: [] },
+			conversationId: "c1",
+		});
+		const result = parseServerMessage(data);
+		expect(result).toEqual({
+			type: "surface",
+			spec: { id: "s1", region: "r", title: "S1", fields: [] },
+			conversationId: "c1",
+		});
+	});
+
+	it("rejects a surface message with a non-string conversationId", () => {
+		const data = JSON.stringify({
+			type: "surface",
+			spec: { id: "s1", region: "r", title: "S1", fields: [] },
+			conversationId: 42,
+		});
+		expect(parseServerMessage(data)).toBeNull();
+	});
+
 	it("parses an update message", () => {
 		const data = JSON.stringify({
 			type: "update",
diff --git a/src/adapters/ws/logic.ts b/src/adapters/ws/logic.ts
index 6592f1b..17e3951 100644
--- a/src/adapters/ws/logic.ts
+++ b/src/adapters/ws/logic.ts
@@ -59,7 +59,15 @@ export function parseServerMessage(data: string): WsServerMessage | null {
 			if (typeof spec.region !== "string") return null;
 			if (typeof spec.title !== "string") return null;
 			if (!Array.isArray(spec.fields)) return null;
-			return { type: "surface", spec: spec as unknown as SurfaceMessage["spec"] };
+			// Preserve the conversationId echo (a conversation-scoped surface's initial
+			// reply carries it) — dropping it would defeat the protocol reducer's
+			// stale-scope filtering on a fast conversation switch.
+			const conversationId = parsed.conversationId;
+			if (conversationId !== undefined && typeof conversationId !== "string") return null;
+			const surfaceSpec = spec as unknown as SurfaceMessage["spec"];
+			return conversationId !== undefined
+				? { type: "surface", spec: surfaceSpec, conversationId }
+				: { type: "surface", spec: surfaceSpec };
 		}
 		case "update": {
 			const update = parsed.update;