From aa4fc0140a189f0ccfe97cd6b6bc23328c62ed33 Mon Sep 17 00:00:00 2001
From: Ritwij Aryan Parmar <ritwij.aryan.parmar@gmail.com>
Date: Tue, 26 May 2026 01:10:19 -0400
Subject: [PATCH] fix(web): match MCP language models by identity

---
 packages/web/src/features/chat/utils.test.ts | 27 +++++++++++++++++++-
 packages/web/src/features/chat/utils.ts      | 11 ++++++++
 packages/web/src/features/mcp/askCodebase.ts |  4 +--
 3 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/packages/web/src/features/chat/utils.test.ts b/packages/web/src/features/chat/utils.test.ts
index 26359d2a9..5663de75a 100644
--- a/packages/web/src/features/chat/utils.test.ts
+++ b/packages/web/src/features/chat/utils.test.ts
@@ -1,5 +1,5 @@
 import { expect, test, vi } from 'vitest'
-import { fileReferenceToString, getAnswerPartFromAssistantMessage, groupMessageIntoSteps, repairReferences } from './utils'
+import { fileReferenceToString, getAnswerPartFromAssistantMessage, groupMessageIntoSteps, isSameLanguageModelIdentity, repairReferences } from './utils'
 import { FILE_REFERENCE_REGEX, ANSWER_TAG } from './constants';
 import { SBChatMessage, SBChatMessagePart } from './types';
 
@@ -44,6 +44,31 @@ test('fileReferenceToString matches FILE_REFERENCE_REGEX', () => {
     }))).toBe(true);
 });
 
+test('isSameLanguageModelIdentity ignores displayName', () => {
+    expect(isSameLanguageModelIdentity(
+        {
+            provider: 'anthropic',
+            model: 'claude-opus-4-7',
+            displayName: 'Claude Opus 4.7 (slow, highest quality)',
+        },
+        {
+            provider: 'anthropic',
+            model: 'claude-opus-4-7',
+        },
+    )).toBe(true);
+
+    expect(isSameLanguageModelIdentity(
+        {
+            provider: 'anthropic',
+            model: 'claude-opus-4-7',
+        },
+        {
+            provider: 'anthropic',
+            model: 'claude-sonnet-4-6',
+        },
+    )).toBe(false);
+});
+
 test('groupMessageIntoSteps returns an empty array when there are no parts', () => {
     const parts: SBChatMessagePart[] = []
 
diff --git a/packages/web/src/features/chat/utils.ts b/packages/web/src/features/chat/utils.ts
index 38dd784fd..026443f1e 100644
--- a/packages/web/src/features/chat/utils.ts
+++ b/packages/web/src/features/chat/utils.ts
@@ -371,6 +371,17 @@ export const getLanguageModelKey = (model: LanguageModelInfo) => {
     return `${model.provider}-${model.model}-${model.displayName}`;
 }
 
+/**
+ * Checks whether two language model infos refer to the same configured model.
+ *
+ * Unlike getLanguageModelKey, this intentionally ignores displayName because
+ * MCP clients can select models using only the externally visible provider and
+ * model fields.
+ */
+export const isSameLanguageModelIdentity = (a: LanguageModelInfo, b: LanguageModelInfo) => {
+    return a.provider === b.provider && a.model === b.model;
+}
+
 /**
  * Given a file reference and a list of file sources, attempts to resolve the file source that the reference points to.
  */
diff --git a/packages/web/src/features/mcp/askCodebase.ts b/packages/web/src/features/mcp/askCodebase.ts
index 810010bcc..2678e00bf 100644
--- a/packages/web/src/features/mcp/askCodebase.ts
+++ b/packages/web/src/features/mcp/askCodebase.ts
@@ -1,7 +1,7 @@
 import { sew } from "@/middleware/sew";
 import { getConfiguredLanguageModels, getAISDKLanguageModelAndOptions, generateChatNameFromMessage, updateChatMessages } from "@/features/chat/utils.server";
 import { LanguageModelInfo, SBChatMessage, SearchScope } from "@/features/chat/types";
-import { convertLLMOutputToPortableMarkdown, getAnswerPartFromAssistantMessage, getLanguageModelKey } from "@/features/chat/utils";
+import { convertLLMOutputToPortableMarkdown, getAnswerPartFromAssistantMessage, isSameLanguageModelIdentity } from "@/features/chat/utils";
 import { ErrorCode } from "@/lib/errorCodes";
 import { ServiceError, ServiceErrorException } from "@/lib/serviceError";
 import { withOptionalAuth } from "@/middleware/withAuth";
@@ -58,7 +58,7 @@ export const askCodebase = (params: AskCodebaseParams): Promise<AskCodebaseResul
             let languageModelConfig = configuredModels[0];
             if (requestedLanguageModel) {
                 const matchingModel = configuredModels.find(
-                    (m) => getLanguageModelKey(m) === getLanguageModelKey(requestedLanguageModel)
+                    (m) => isSameLanguageModelIdentity(m, requestedLanguageModel)
                 );
                 if (!matchingModel) {
                     return {