ui : fix MCP image attachments not displayed in tool block (#25789) (#28089)

* ui : fix MCP image attachments not displayed in tool block (#25789)

Fixes regression from #25450 where ChatMessageAgenticContent passed
message.extra instead of section.toolResultExtras to tool blocks,
leaving tool images invisible. Also fixes TOOL_RESULT_JSON_OPEN_REGEX
which misclassified "[Attachment saved: ...]" as JSON.

Fixes #25789

Assisted-by: Muse Spark

* Addressed PR comments: 1.- Removed ·?? mesage?extra· as it has no case left to cover 2.- Added ·[\· to cover the case of ·[[1, 2], [3, 4]]· case suggested in the PR comment 3.- Added unit test for covering up this regex case

* ui : fix MCP image attachments not displayed in tool block (ggml-org#25789) - Addressed lint error on regex (redundant \)

tools/ui/src/lib/components/app/chat/ChatMessages/ChatMessageAgenticContent.svelte

@@ -194,7 +194,7 @@
 		/>
 	{:else if section.type === AgenticSectionType.TOOL_CALL || section.type === AgenticSectionType.TOOL_CALL_PENDING || section.type === AgenticSectionType.TOOL_CALL_STREAMING}
 		<ChatMessageToolCallBlock
-			attachments={message?.extra}
+			attachments={section.toolResultExtras}
 			isExecuting={section.toolCallId !== undefined &&
 				section.toolCallId === currentlyExecutingToolCallId}
 			{isStreaming}

tools/ui/src/lib/constants/agentic.constants.ts

@@ -2,8 +2,11 @@ import type { AgenticConfig } from '$lib/types/agentic';
 
 export const ATTACHMENT_SAVED_REGEX = /\[Attachment saved: ([^\]]+)\]/;
 
-// JSON detection: trimmed content opens with an object or array literal.
-export const TOOL_RESULT_JSON_OPEN_REGEX = /^[[{]/;
+// JSON detection: an attachment placeholder also starts with `[`, but is
+// plain text (`[Attachment saved: ...]`), not an array literal. Require the
+// first array value (or the closing bracket for an empty array) to look like
+// a valid JSON token before attempting JSON.parse.
+export const TOOL_RESULT_JSON_OPEN_REGEX = /^(?:\{|\[\s*(?:[[\]"{\-0-9]|true|false|null))/;
 
 // Search-summary wire format used by file-glob and grep tools:
 //   <matches>

tools/ui/tests/unit/classify-tool-result.test.ts

@@ -37,6 +37,10 @@ describe('classifyToolResult', () => {
 			expect(classifyToolResult('["a", "b", "c"]')).toBe('json');
 		});
 
+		it('classifies a nested JSON array', () => {
+			expect(classifyToolResult('[[1, 2], [3, 4]]')).toBe('json');
+		});
+
 		it('classifies a pretty-printed JSON object', () => {
 			expect(classifyToolResult('{\n  "key": "value"\n}')).toBe('json');
 		});