diff --git a/packages/coding-agent/src/lsp/mux/server.ts b/packages/coding-agent/src/lsp/mux/server.ts
index 6afb08c24..3297e1c36 100644
--- a/packages/coding-agent/src/lsp/mux/server.ts
+++ b/packages/coding-agent/src/lsp/mux/server.ts
@@ -643,21 +643,23 @@ export class LspMuxServer {
 		this.#sessions.delete(session);
 		const server = session.server;
 		if (server) {
-			server.sessions.delete(session);
+			let cleanup: Promise<void> | undefined;
 			for (const uri of session.openUris) {
 				server.documents.delete(uri);
-				await this.#writeServer(server, {
+				cleanup = this.#writeServer(server, {
 					jsonrpc: "2.0",
 					method: "textDocument/didClose",
 					params: { textDocument: { uri } },
 				});
 			}
+			await cleanup;
 			for (const [muxId, pending] of server.pending) {
 				if (pending.session !== session) continue;
 				pending.drop = true;
 				await this.#writeServer(server, { jsonrpc: "2.0", method: "$/cancelRequest", params: { id: muxId } });
 			}
 			server.initializeWaiters.delete(session);
+			server.sessions.delete(session);
 			if (server.sessions.size === 0 && !server.stopping) {
 				server.lingerTimer = setTimeout(() => {
 					if (server.sessions.size === 0) void this.#stopServer(server);
diff --git a/packages/coding-agent/test/lsp-mux.test.ts b/packages/coding-agent/test/lsp-mux.test.ts
index a8dc7438e..90d9c1cc3 100644
--- a/packages/coding-agent/test/lsp-mux.test.ts
+++ b/packages/coding-agent/test/lsp-mux.test.ts
@@ -365,21 +365,31 @@ describe("LspMuxServer", () => {
 	);
 
 	it.skipIf(process.platform === "win32")(
-		"closes orphaned documents before reusing an idle server",
+		"finishes orphan document closes before reusing a server",
 		async () => {
 			const first = await link();
 			await initialize(first.client);
-			const uri = "file:///orphan.ts";
-			first.client.notify("textDocument/didOpen", {
-				textDocument: { uri, languageId: "typescript", version: 1, text: "orphan" },
-			});
-			await pollUntil(async () => (await state(first.client)).didOpen[uri] === 1, "orphan didOpen");
+			const uris = Array.from({ length: 128 }, (_, index) => `file:///orphan-${index}.ts`);
+			for (const uri of uris) {
+				first.client.notify("textDocument/didOpen", {
+					textDocument: { uri, languageId: "typescript", version: 1, text: "orphan" },
+				});
+			}
+			await first.client.request("test/echo", { barrier: true });
+			const firstClosed = first.client.waitForClose();
 			first.client.destroy();
-			await pollUntil(() => Promise.resolve(server.sessionCount === 0), "orphan session close");
+			await firstClosed;
 
 			const second = await link();
 			expect(second.connected.spawned).toBe(false);
-			await pollUntil(async () => (await state(second.client)).didClose.includes(uri), "orphan didClose");
+			const uri = uris.at(-1);
+			expect(uri).toBeDefined();
+			await initialize(second.client);
+			second.client.notify("textDocument/didOpen", {
+				textDocument: { uri, languageId: "typescript", version: 1, text: "replacement" },
+			});
+			await second.client.request("test/echo", { barrier: true });
+			expect(await second.client.request<string | null>("test/documentText", { uri })).toBe("replacement");
 		},
 		10_000,
 	);