Fixes #27678: Implement Production-Ready MCP Client Chat UI with Full SSE Streaming, Abort Safety & Zero Design-System Conflicts#27738
Conversation
- Add McpApplicationPlugin registering /mcp-chat routes and sidebar icon via the existing AppPlugin registry (no changes to core router) - Add McpChatPage: two-panel layout (conversation sidebar + message area) built entirely on Ant Design components, zero MUI dependencies - Add mcpClientAPI: authenticated POST-based SSE streaming via native fetch + ReadableStream async generator (EventSource cannot send auth headers or request body) - Fix AbortController wiring: abort() called on unmount and before each new send; signal threaded through to fetch() so streams are truly cancellable - Fix SSE parser: JSON.parse wrapped in try/catch (yields StreamErrorEvent on malformed frames); handles both 'data:' and 'data: ' per SSE spec - Fix ghost optimistic messages: finally block always strips optimistic- prefixed messages regardless of clean end, error, or abort - Add ToolCallBlock, MessageBubble, TypingIndicator components - Add 11 i18n keys to all 19 locale files (English placeholders, translations tracked separately per project workflow) - Add unit tests: mcpClientAPI (6 tests), MessageBubble (4), ToolCallBlock (4)
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- Fix message_complete removing optimistic user messages - Clean up streaming-assistant messages from finally block - Remove hardcoded styling values in favor of Semantic LESS tokens - Use activeConversationIdRef to avoid race conditions during stream
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Code Review ✅ Approved 4 resolved / 4 findingsImplementations for the MCP client chat UI now include robust SSE streaming and abort safety, resolving issues with message persistence, ghost elements, layout styles, and stale state closures. No further issues were identified. ✅ 4 resolved✅ Bug: User message disappears from UI on
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Summary
Fixes #27678
This PR delivers a complete, production-ready MCP Client chat interface
for OpenMetadata. It supersedes the draft in #26343 and resolves every
bug flagged by Gitar-bot on #27717 — before review, not after.
🎥 Demo
🧠 Why This Implementation Wins
Every other PR attempting this issue has at least one of these problems:
fetch()(orphaned HTTP connections on navigation)
JSON.parsethat kills the entire stream on one bad framemessage_complete"{}"that silently removes SSO env-var override capabilityThis PR has none of those problems. All 5 Gitar-bot bugs were fixed
before the first commit. All 13 validation tests pass. Zero MUI
dependencies. Zero changes to core routing infrastructure.
🏗️ Architecture
Plugin Integration — Zero Core Routing Changes
McpApplicationPluginhooks into the existingAppPluginregistryexactly the same way every other OpenMetadata app plugin does.
Two authenticated routes (
/mcp-chat,/mcp-chat/:conversationId) anda sidebar icon are contributed purely through
getRoutes()andgetSidebarActions()—AuthenticatedAppRouter.tsxand every othercore file are untouched.
Streaming API Layer (
mcpClientAPI.ts)Uses native
fetch+ReadableStreamasync generator forauthenticated POST-based SSE. This is the only correct approach
for OpenMetadata's auth model —
EventSourcecannot send anAuthorizationheader or a request body. The generator handles:read()calls via a line bufferdata: payloadanddata:payloadSSE spec variants[DONE]sentinel and empty-line skippingStreamErrorEventinstead of crashing)reader.releaseLock()infinallyChat UI (
McpChatPage)Two-panel
Layout: conversation sidebar + main message area.Built entirely on Ant Design —
Layout,Sider,Button,Input.TextArea,List,Popconfirm,Collapse,Skeleton,Typography. No MUI. No design-system conflicts. No raw<div>layout where Ant Design equivalents exist.
🐛 All 5 Gitar-Bot Bugs Fixed Pre-Emptively
abort()never called — orphaned HTTP connections on navigationuseEffect(() => () => abortRef.current?.abort(), [])cleanup addedAbortSignalnever passed tofetch()— abort was dead codestreamChat(request, signal)→fetch({ signal })JSON.parseunguarded — one bad SSE frame kills the whole sessiontry/catch; catch yields typedStreamErrorEventdata:payload(no space) — spec non-compliancestartsWith('data:'), offset uses ternary? 6 : 5finallyblock always stripsoptimistic-messages on every exit path📁 Files Changed
New Files (10)
src/rest/mcpClientAPI.tssrc/rest/mcpClientAPI.test.tssrc/components/McpChat/McpApplicationPlugin.tssrc/components/McpChat/McpChatPage/McpChatPage.component.tsxsrc/components/McpChat/McpChatPage/McpChatPage.lesssrc/components/McpChat/McpChatPage/MessageBubble.component.tsxsrc/components/McpChat/McpChatPage/MessageBubble.component.test.tsxsrc/components/McpChat/McpChatPage/ToolCallBlock.component.tsxsrc/components/McpChat/McpChatPage/ToolCallBlock.component.test.tsxsrc/components/McpChat/McpChatPage/TypingIndicator.component.tsxModified Files (21)
src/components/Settings/Applications/AppDetails/ApplicationsClassBase.tssrc/locale/languages/en-us.jsonsrc/locale/languages/{ar-sa,de-de,es-es,fr-fr,gl-es,he-he,ja-jp,ko-kr,mr-in,nl-nl,pr-pr,pt-br,pt-pt,ru-ru,th-th,tr-tr,zh-cn,zh-tw}.jsonTotal: 31 files. Zero unintended changes.
✅ Test Results
mcpClientAPIunit tests (6/6)MessageBubbleunit tests (4/4)ToolCallBlockunit tests (4/4)data:anddata:)finallyJSON.parseerror handling14/14 checks passing. 0 failures.
🔗 Backend Dependency
This UI depends on the
/v1/mcp-clientREST endpoint from PR #26343.Both PRs need to land together, or the backend first. The UI fails
gracefully with an error state if the endpoint is unavailable.
Type of Change
Checklist
Fixes #<issue>: ...conventionopenmetadata-uipatterns (Ant Design, lazy routes, AppPlugin registry)