📊 feat: Surface Message Feedback as Langfuse Scores (#13544)

* feat: surface message feedback (thumbs up/down) as Langfuse scores

When Langfuse tracing is enabled, the message feedback endpoint now posts a
boolean `user-feedback` score (1/0 + tag/comment) to Langfuse for the
assistant message's trace; clearing feedback deletes the score. Fire-and-
forget, so the feedback UX never blocks on Langfuse.

Linking is lookup-free: the run opts into deterministic Langfuse trace ids
(`langfuse.deterministicTraceId`, passed to the agents Run), so the trace id
is sha256(messageId)[:32]. The feedback route recomputes the same id and
scores by it.

- api/server/services/Langfuse.js: POST/DELETE /api/public/scores (env-gated)
- api/server/utils/langfuseTrace.js: traceIdForMessage(messageId)
- api/server/routes/messages.js: fire feedback score after the Mongo write
- packages/api: pass langfuse.deterministicTraceId to the run
- bump @librechat/agents to ^3.2.21 (adds LangfuseConfig.deterministicTraceId)

Closes #13537

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix: match Langfuse trace environment for feedback scores

@librechat/agents passes no environment to its Langfuse tracer, so
@langfuse/otel falls back to LANGFUSE_TRACING_ENVIRONMENT and otherwise to
Langfuse's "default". The score helper instead fell back to NODE_ENV, so a
deployment with only NODE_ENV=production filed scores under "production" while
the trace stayed on "default" — the score never landed on the trace.

Use LANGFUSE_TRACING_ENVIRONMENT only, and omit `environment` when unset so
Langfuse defaults both score and trace to "default".

Addresses Codex review on #13544.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix: don't require LANGFUSE_BASE_URL to post feedback scores

The agent tracer emits traces with just the public/secret keys (defaulting to
Langfuse Cloud, or via the legacy LANGFUSE_BASEURL alias), but the score helper
disabled itself unless LANGFUSE_BASE_URL was set — so an otherwise-traced
deployment silently posted no scores. Resolve the base URL the same way the
tracer does (LANGFUSE_BASE_URL -> LANGFUSE_BASEURL -> Cloud) and gate enablement
on the credentials only.

Addresses Codex review on #13544.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix: only post feedback scores for agent-endpoint messages

The feedback route is shared by all message types, but deterministic Langfuse
trace IDs are only enabled for agent runs. Rating a message from a non-agent
endpoint (with Langfuse configured) posted a user-feedback score for
sha256(messageId) that no trace will ever match, leaving orphan scores.

Gate scoring on isAgentsEndpoint(message.endpoint); `updateMessage` now returns
`endpoint` so the route can check it.

Addresses Codex review on #13544.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix: gate feedback scoring by !isAssistantsEndpoint, not isAgentsEndpoint

The previous gate used isAgentsEndpoint, which only matches the literal
`agents` endpoint. But provider endpoints (anthropic, openai, custom, …) run
through the agents runtime as ephemeral agents and DO emit deterministic
AgentRun traces, so isAgentsEndpoint('anthropic') === false suppressed scoring
for the common case. Only the OpenAI/Azure Assistants endpoints use a separate
runtime with no agent trace, so gate on !isAssistantsEndpoint instead.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* style: sort message method imports

* fix: honor Langfuse tracing gates for feedback scores

* refactor: move Langfuse feedback logic to api package

* fix: support Langfuse host for feedback scores

* test: type Langfuse feedback fetch mock

* chore: compact Langfuse feedback comment

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Co-authored-by: Danny Avila <danny@librechat.ai>

api/server/routes/messages.js

@@ -1,8 +1,13 @@
 const express = require('express');
 const { v4: uuidv4 } = require('uuid');
 const { logger } = require('@librechat/data-schemas');
-const { ContentTypes } = require('librechat-data-provider');
-const { unescapeLaTeX, countTokens } = require('@librechat/api');
+const { ContentTypes, isAssistantsEndpoint } = require('librechat-data-provider');
+const {
+  unescapeLaTeX,
+  countTokens,
+  sendFeedbackScore,
+  traceIdForMessage,
+} = require('@librechat/api');
 const { findAllArtifacts, replaceArtifactContent } = require('~/server/services/Artifacts/update');
 const { requireJwtAuth, validateMessageReq } = require('~/server/middleware');
 const db = require('~/models');
@@ -391,6 +396,14 @@ router.put('/:conversationId/:messageId/feedback', validateMessageReq, async (re
       { context: 'updateFeedback' },
     );
 
+    // Best-effort: Assistants messages do not have deterministic AgentRun traces.
+    if (!isAssistantsEndpoint(updatedMessage.endpoint)) {
+      sendFeedbackScore({
+        traceId: traceIdForMessage(messageId),
+        feedback: updatedMessage.feedback,
+      }).catch((err) => logger.error('[langfuse] feedback score failed:', err));
+    }
+
     res.json({
       messageId,
       conversationId,