Fix: Handle network errors in instruction fetch gracefully

Wrap the fetch() call in fetchLatestInstructions with a try-catch block
to handle transport-level errors (DNS failure, connection refused,
network timeout) that cause fetch to throw rather than returning a
Response object.

Previously, these errors would propagate unhandled through getInstructions
and newMcpServer, causing the entire MCP server to fail to handle
requests in HTTP mode, or preventing server startup in stdio mode.

Now, network errors are caught and logged, and the server falls back to
the default instructions, matching the existing behavior for HTTP-level
errors (!response.ok).

Author: cursoragent

packages/mcp-server/src/instructions.ts

@@ -37,33 +37,43 @@ export async function getInstructions(stainlessApiKey: string | undefined): Prom
   return fetchedInstructions;
 }
 
-async function fetchLatestInstructions(stainlessApiKey: string | undefined): Promise<string> {
-  // Setting the stainless API key is optional, but may be required
-  // to authenticate requests to the Stainless API.
-  const response = await fetch(
-    readEnv('CODE_MODE_INSTRUCTIONS_URL') ?? 'https://api.stainless.com/api/ai/instructions/dedalus-sdk',
-    {
-      method: 'GET',
-      headers: { ...(stainlessApiKey && { Authorization: stainlessApiKey }) },
-    },
-  );
+const DEFAULT_INSTRUCTIONS = `
+  This is the dedalus-sdk MCP server. You will use Code Mode to help the user perform
+  actions. You can use search_docs tool to learn about how to take action with this server. Then,
+  you will write TypeScript code using the execute tool take action. It is CRITICAL that you be
+  thoughtful and deliberate when executing code. Always try to entirely solve the problem in code
+  block: it can be as long as you need to get the job done!
+`;
 
+async function fetchLatestInstructions(stainlessApiKey: string | undefined): Promise<string> {
   let instructions: string | undefined;
-  if (!response.ok) {
-    console.warn(
-      'Warning: failed to retrieve MCP server instructions. Proceeding with default instructions...',
+
+  try {
+    // Setting the stainless API key is optional, but may be required
+    // to authenticate requests to the Stainless API.
+    const response = await fetch(
+      readEnv('CODE_MODE_INSTRUCTIONS_URL') ?? 'https://api.stainless.com/api/ai/instructions/dedalus-sdk',
+      {
+        method: 'GET',
+        headers: { ...(stainlessApiKey && { Authorization: stainlessApiKey }) },
+      },
     );
 
-    instructions = `
-      This is the dedalus-sdk MCP server. You will use Code Mode to help the user perform
-      actions. You can use search_docs tool to learn about how to take action with this server. Then,
-      you will write TypeScript code using the execute tool take action. It is CRITICAL that you be
-      thoughtful and deliberate when executing code. Always try to entirely solve the problem in code
-      block: it can be as long as you need to get the job done!
-    `;
+    if (!response.ok) {
+      console.warn(
+        'Warning: failed to retrieve MCP server instructions. Proceeding with default instructions...',
+      );
+      instructions = DEFAULT_INSTRUCTIONS;
+    } else {
+      instructions = ((await response.json()) as { instructions: string }).instructions;
+    }
+  } catch (error) {
+    console.warn(
+      'Warning: network error while fetching MCP server instructions. Proceeding with default instructions...',
+      error,
+    );
+    instructions = DEFAULT_INSTRUCTIONS;
   }
-
-  instructions ??= ((await response.json()) as { instructions: string }).instructions;
   instructions = `
     If needed, you can get the current time by executing Date.now().