diff --git a/packages/opencode/src/mcp/index.ts b/packages/opencode/src/mcp/index.ts
index 0a3137c0ec..fe71802388 100644
--- a/packages/opencode/src/mcp/index.ts
+++ b/packages/opencode/src/mcp/index.ts
@@ -114,6 +114,11 @@ function isMcpConfigured(entry: McpEntry): entry is ConfigMCP.Info {
 
 const sanitize = (s: string) => s.replace(/[^a-zA-Z0-9_-]/g, "_")
 
+function remoteURL(key: string, value: string) {
+  if (URL.canParse(value)) return new URL(value)
+  log.warn("invalid remote mcp url", { key })
+}
+
 // Convert MCP tool definition to AI SDK Tool type
 function convertMcpTool(mcpTool: MCPToolDef, client: MCPClient, timeout?: number): Tool {
   const inputSchema = mcpTool.inputSchema
@@ -267,6 +272,13 @@ export const layer = Layer.effect(
     ) {
       const oauthDisabled = mcp.oauth === false
       const oauthConfig = typeof mcp.oauth === "object" ? mcp.oauth : undefined
+      const url = remoteURL(key, mcp.url)
+      if (!url) {
+        return {
+          client: undefined as MCPClient | undefined,
+          status: { status: "failed" as const, error: `Invalid MCP URL for "${key}"` },
+        }
+      }
       let authProvider: McpOAuthProvider | undefined
 
       if (!oauthDisabled) {
@@ -291,14 +303,14 @@ export const layer = Layer.effect(
       const transports: Array<{ name: string; transport: TransportWithAuth }> = [
         {
           name: "StreamableHTTP",
-          transport: new StreamableHTTPClientTransport(new URL(mcp.url), {
+          transport: new StreamableHTTPClientTransport(url, {
             authProvider,
             requestInit: mcp.headers ? { headers: mcp.headers } : undefined,
           }),
         },
         {
           name: "SSE",
-          transport: new SSEClientTransport(new URL(mcp.url), {
+          transport: new SSEClientTransport(url, {
             authProvider,
             requestInit: mcp.headers ? { headers: mcp.headers } : undefined,
           }),
@@ -722,6 +734,8 @@ export const layer = Layer.effect(
       if (!mcpConfig) throw new Error(`MCP server ${mcpName} not found or disabled`)
       if (mcpConfig.type !== "remote") throw new Error(`MCP server ${mcpName} is not a remote server`)
       if (mcpConfig.oauth === false) throw new Error(`MCP server ${mcpName} has OAuth explicitly disabled`)
+      const url = remoteURL(mcpName, mcpConfig.url)
+      if (!url) throw new Error(`Invalid MCP URL for "${mcpName}"`)
 
       // OAuth config is optional - if not provided, we'll use auto-discovery
       const oauthConfig = typeof mcpConfig.oauth === "object" ? mcpConfig.oauth : undefined
@@ -751,7 +765,7 @@ export const layer = Layer.effect(
         auth,
       )
 
-      const transport = new StreamableHTTPClientTransport(new URL(mcpConfig.url), { authProvider })
+      const transport = new StreamableHTTPClientTransport(url, { authProvider })
 
       return yield* Effect.tryPromise({
         try: () => {