fix(xl-ai): preserve error messages in ClientSideTransport stream

.claude/skills/github-issues/SKILL.md

@@ -0,0 +1,18 @@
+---
+name: github-issues
+description: Scan the BlockNote GitHub repository for issues and PRs relevant to the current task. Use when starting work on a new feature, bug fix, or other code modification.
+---
+
+This skill searches the BlockNote GitHub repository for existing issues and PRs that are relevant to the task at hand.
+
+# When to use
+
+Use this skill when prompted to write a new feature, fix a bug, or make some other modification to the code. It should be invoked before writing any code to surface relevant context from the project's issue tracker.
+
+# Steps
+
+1. Use the GitHub CLI (`gh`) to search for issues and PRs in the repository that are relevant to the user's task. Search both open and closed issues/PRs using relevant keywords.
+2. Summarize the findings:
+   - If nothing relevant is found, report that and proceed with the task.
+   - If relevant issues or PRs are found, present a summary and prompt the user on next steps before writing code.
+3. Once the task is completed, remind the user of the relevant issues and PRs found during this initial investigation so they can be referenced or closed as appropriate.

AGENTS.md

@@ -2,16 +2,6 @@
 
 BlockNote is a block-based rich text editor for the web. It's designed as a batteries-included product that offers a solid user experience with minimal setup. However, it also offers extensibility via plugins and custom block types.
 
-# Issue Context
-
-When prompted to write a new feature, fix a bug, or make some other modification to the code, the project repository on GitHub should be scanned for issues and PRs which are relevant to the task at hand. Before writing any code, a summary of these should be given. If nothing relevant is found, the task can be started immediately. Otherwise, the user should be prompted on next steps.
-
-This should only be done for new conversations. If GitHub was already scanned in the same conversation, it does not need to be scanned again.
-
-Once the task is done and the feature is completed, bug is fixed, etc, the user should be reminded of the relevant issues and PRs found in the initial investigation.
-
-The GitHub CLI should be used to browse issues and PRs.
-
 # Common Commands
 
 All commands below are listed under `package.json` in the project root. See `vite.config.ts` for relevant configuration settings.

packages/xl-ai/src/streamTool/vercelAiSdk/clientside/ClientSideTransport.ts

@@ -95,7 +95,10 @@ export class ClientSideTransport<
       // activeTools: ["applyDocumentOperations"],
     });
 
-    return ret.toUIMessageStream();
+    return ret.toUIMessageStream({
+      onError: (error) =>
+        error instanceof Error ? error.message : String(error),
+    });
   }
 
   async sendMessages({