fix(decopilot): include prompt arguments in catalog and skip re-reading applied prompts (#2771)

* fix(decopilot): include prompt arguments in catalog and skip re-reading applied prompts

The prompt catalog now surfaces argument metadata (name, required) so the
LLM knows which arguments to pass when calling read_prompt. The workflow
prompt also instructs the LLM to skip read_prompt when a prompt was already
expanded inline via the mention UI, preventing the MCP -32602 error.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix(decopilot): strengthen warning to not re-read already-loaded prompts

The previous instruction was too subtle — the LLM still called read_prompt
for prompts already in context. Made the warning more prominent with
MUST NOT and WARNING formatting to ensure the LLM skips the redundant call.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: tlgimenes

apps/mesh/src/api/routes/decopilot/constants.ts

@@ -43,7 +43,12 @@ Follow this workflow for every request:
 3. **Plan** — for multi-step tasks (3+ tool calls), outline the steps
    and wait for user confirmation. For simple tasks, act immediately.
 4. **Learn skills** — check <available-prompts> for a matching prompt.
-   If one exists, load it with read_prompt and follow its steps.
+   **WARNING: If a prompt's content already appears anywhere in the
+   conversation history (e.g. applied via /promptName in the UI), you
+   MUST NOT call read_prompt for it — the content is already loaded.
+   Follow its instructions directly.** Only call read_prompt for prompts
+   whose content is NOT yet in the conversation, passing any required
+   arguments listed in <available-prompts>.
 5. **Execute** — enable the tools you need, then carry out the plan.
 6. **If not possible** — explain why, suggest what connection the user
    could add, and offer a partial workaround if one exists.

apps/mesh/src/api/routes/decopilot/stream-core.ts

@@ -844,13 +844,26 @@ function escapeXmlAttr(s: string): string {
  */
 async function buildPromptCatalog(client: {
   listPrompts(): Promise<{
-    prompts: Array<{ name: string; description?: string }>;
+    prompts: Array<{
+      name: string;
+      description?: string;
+      arguments?: Array<{ name: string; required?: boolean }>;
+    }>;
   }>;
 }): Promise<string | null> {
   const { prompts } = await client.listPrompts();
   if (prompts.length === 0) return null;
 
-  const lines = prompts.map((p) => `${p.name}|${p.description ?? ""}`);
+  const lines = prompts.map((p) => {
+    let line = `${p.name}|${p.description ?? ""}`;
+    if (p.arguments && p.arguments.length > 0) {
+      const args = p.arguments
+        .map((a) => (a.required ? `${a.name} (required)` : a.name))
+        .join(", ");
+      line += `|args: ${args}`;
+    }
+    return line;
+  });
 
   return `\n\n<available-prompts>\n${lines.join("\n")}\n</available-prompts>`;
 }