feat: support attached images for all providers

server/shared/utils.ts

@@ -1239,3 +1239,24 @@ export async function extractFirstValidJsonlData<T>(
   return null;
 }
 
+// ---------------------------
+//----------------- CLI PROMPT ARGUMENT UTILITIES ------------
+/**
+ * Makes a prompt safe to pass as one CLI argument to `.cmd`-shimmed tools on
+ * Windows (cursor-agent, gemini, opencode installed via npm-style shims).
+ *
+ * cmd.exe cannot carry newlines inside an argument: everything after the
+ * first newline is silently dropped before the target CLI ever sees it, which
+ * truncates multi-line prompts and any appended `<images_input>` block.
+ * Collapsing newline runs to single spaces loses formatting but never loses
+ * content, so runtimes should call this on win32 right before spawning.
+ *
+ * Used by the cursor, gemini, and opencode spawn runtimes.
+ */
+export function flattenPromptForWindowsShell(prompt: string): string {
+  if (process.platform !== 'win32' || typeof prompt !== 'string') {
+    return prompt;
+  }
+  return prompt.replace(/\s*\r?\n\s*/g, ' ').trim();
+}
+