fix: allow empty CLI env values

cli/__tests__/cli.test.ts

@@ -123,6 +123,26 @@ describe("CLI Tests", () => {
       expect(envVars.API_KEY).toBe("abc123=xyz789==");
     });
 
+    it("should accept empty environment variable values", async () => {
+      const { command, args } = getTestMcpServerCommand();
+      const result = await runCli([
+        command,
+        ...args,
+        "-e",
+        "EMPTY_ENV=",
+        "--cli",
+        "--method",
+        "resources/read",
+        "--uri",
+        "test://env",
+      ]);
+
+      expectCliSuccess(result);
+      const json = expectValidJson(result);
+      const envVars = JSON.parse(json.contents[0].text);
+      expect(envVars.EMPTY_ENV).toBe("");
+    });
+
     it("should handle environment variable with base64-encoded value", async () => {
       const { command, args } = getTestMcpServerCommand();
       const result = await runCli([

cli/src/cli.ts

@@ -205,17 +205,24 @@ function parseKeyValuePair(
   value: string,
   previous: Record<string, string> = {},
 ): Record<string, string> {
-  const parts = value.split("=");
-  const key = parts[0];
-  const val = parts.slice(1).join("=");
+  const equalsIndex = value.indexOf("=");
 
-  if (val === undefined || val === "") {
+  if (equalsIndex === -1) {
     throw new Error(
       `Invalid parameter format: ${value}. Use key=value format.`,
     );
   }
 
-  return { ...previous, [key as string]: val };
+  const key = value.slice(0, equalsIndex);
+  const val = value.slice(equalsIndex + 1);
+
+  if (key === "") {
+    throw new Error(
+      `Invalid parameter format: ${value}. Use key=value format.`,
+    );
+  }
+
+  return { ...previous, [key]: val };
 }
 
 function parseHeaderPair(