diff --git a/packages/coding-agent/src/modes/controllers/mcp-command-controller.ts b/packages/coding-agent/src/modes/controllers/mcp-command-controller.ts
index 8f26e9740..cfbef3400 100644
--- a/packages/coding-agent/src/modes/controllers/mcp-command-controller.ts
+++ b/packages/coding-agent/src/modes/controllers/mcp-command-controller.ts
@@ -597,6 +597,11 @@ export class MCPCommandController {
 		const resolvedClientSecret = clientSecret.trim() || undefined;
 
 		const manualInput = this.ctx.oauthManualInput;
+		if (manualInput.hasPending() && manualInput.pendingProviderId !== MCP_MANUAL_INPUT_PROVIDER_ID) {
+			throw new Error(
+				`OAuth login already in progress for ${manualInput.pendingProviderId}. Complete or cancel it before starting MCP OAuth.`,
+			);
+		}
 		const oauthTimeout = new AbortController();
 		try {
 			// Create OAuth flow
@@ -652,8 +657,15 @@ export class MCPCommandController {
 					onProgress: (message: string) => {
 						this.ctx.present([new Spacer(1), new Text(theme.fg("muted", message), 1, 0)]);
 					},
-					onManualCodeInput: () => manualInput.waitForInput(MCP_MANUAL_INPUT_PROVIDER_ID),
-					signal: oauthTimeout.signal,
+					onManualCodeInput: () => {
+						const pendingInput = manualInput.tryWaitForInput(MCP_MANUAL_INPUT_PROVIDER_ID);
+						if (!pendingInput) {
+							throw new Error(
+								`OAuth login already in progress for ${manualInput.pendingProviderId}. Complete or cancel it before starting MCP OAuth.`,
+							);
+						}
+						return pendingInput;
+					},
 				},
 			);
 
diff --git a/packages/coding-agent/src/modes/oauth-manual-input.ts b/packages/coding-agent/src/modes/oauth-manual-input.ts
index aa0d0b1b8..4591fcb1d 100644
--- a/packages/coding-agent/src/modes/oauth-manual-input.ts
+++ b/packages/coding-agent/src/modes/oauth-manual-input.ts
@@ -17,6 +17,11 @@ export class OAuthManualInputManager {
 		return promise;
 	}
 
+	tryWaitForInput(providerId: string): Promise<string> | undefined {
+		if (this.#pending) return undefined;
+		return this.waitForInput(providerId);
+	}
+
 	submit(input: string): boolean {
 		if (!this.#pending) return false;
 		const { resolve } = this.#pending;
diff --git a/packages/coding-agent/test/oauth-manual-input.test.ts b/packages/coding-agent/test/oauth-manual-input.test.ts
index 164a61934..89dcc2653 100644
--- a/packages/coding-agent/test/oauth-manual-input.test.ts
+++ b/packages/coding-agent/test/oauth-manual-input.test.ts
@@ -13,6 +13,17 @@ describe("OAuthManualInputManager", () => {
 		expect(manager.hasPending()).toBe(false);
 	});
 
+	it("does not replace pending input when using tryWaitForInput", async () => {
+		const manager = new OAuthManualInputManager();
+		const first = manager.waitForInput("openai-codex");
+
+		expect(manager.tryWaitForInput("mcp")).toBeUndefined();
+		expect(manager.pendingProviderId).toBe("openai-codex");
+
+		expect(manager.submit("callback-url")).toBe(true);
+		expect(await first).toBe("callback-url");
+	});
+
 	it("returns false when no pending input", () => {
 		const manager = new OAuthManualInputManager();