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fix(mcp): match language model by provider+model, fall back when displayName absent #1153

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fix(mcp): match language model by provider+model, fall back when displayName absent #1153

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37d8793
fix(mcp): match language model by provider+model with precise error m…
Apr 26, 2026
2ce84cd
fix(mcp): actionable error when all ambiguous candidates lack display…
Apr 26, 2026
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29 changes: 25 additions & 4 deletions packages/web/src/features/mcp/askCodebase.ts
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Original file line number Diff line number Diff line change
@@ -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 } from "@/features/chat/utils";
import { ErrorCode } from "@/lib/errorCodes";
import { ServiceError, ServiceErrorException } from "@/lib/serviceError";
import { withOptionalAuth } from "@/middleware/withAuth";
Expand Down Expand Up @@ -57,14 +57,35 @@ export const askCodebase = (params: AskCodebaseParams): Promise<AskCodebaseResul

let languageModelConfig = configuredModels[0];
if (requestedLanguageModel) {
const matchingModel = configuredModels.find(
(m) => getLanguageModelKey(m) === getLanguageModelKey(requestedLanguageModel)
const candidates = configuredModels.filter(
(m) => m.provider === requestedLanguageModel.provider &&
m.model === requestedLanguageModel.model
);
const displayNameProvided = requestedLanguageModel.displayName !== undefined;
const matchingModel = displayNameProvided
? candidates.find((m) => m.displayName === requestedLanguageModel.displayName)
: candidates.length === 1 ? candidates[0] : undefined;
Comment on lines +60 to +67
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@coderabbitai coderabbitai Bot Apr 26, 2026

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⚠️ Potential issue | 🟠 Major

🧩 Analysis chain

🏁 Script executed:

#!/bin/bash
# Inspect the chat route and its request schema to see if the same key-based
# match has the same displayName-undefined failure mode.
fd -t f 'route.ts' packages/web/src/app/api | xargs rg -nP -C5 'getLanguageModelKey'
rg -nP -C3 'languageModel\s*[:?]' packages/web/src/app/api/\(server\)/chat
rg -nP -C3 'displayName' packages/web/src/app/api/\(server\)/chat

Repository: sourcebot-dev/sourcebot

Length of output: 4415

🏁 Script executed:

# First, let's understand what getLanguageModelKey does
rg -nP -A10 'function getLanguageModelKey|export.*getLanguageModelKey|const getLanguageModelKey' packages/web/src/features/chat/utils.ts

Repository: sourcebot-dev/sourcebot

Length of output: 629

🏁 Script executed:

# Check the full schema definition for languageModel in the chat request
rg -nP -A20 'additionalChatRequestParamsSchema' packages/web/src/features/chat/types.ts

Repository: sourcebot-dev/sourcebot

Length of output: 342

🏁 Script executed:

# Look at the languageModelInfoSchema to understand displayName handling
rg -nP -B5 -A15 'languageModelInfoSchema' packages/web/src/features/chat/types.ts

Repository: sourcebot-dev/sourcebot

Length of output: 1251

🏁 Script executed:

# Compare the MCP request schema for askCodebase
rg -nP -B5 -A15 'languageModel' packages/web/src/features/mcp/types.ts | head -60

Repository: sourcebot-dev/sourcebot

Length of output: 49

🏁 Script executed:

# Look at the actual MCP askCodebase.ts around lines 60-67 to see the fix
cat -n packages/web/src/features/mcp/askCodebase.ts | sed -n '50,80p'

Repository: sourcebot-dev/sourcebot

Length of output: 2263

🏁 Script executed:

# Check if there are other routes/API handlers using getLanguageModelKey with similar pattern
rg -nP 'getLanguageModelKey' packages/web/src --type ts --type tsx -B3 -A3

Repository: sourcebot-dev/sourcebot

Length of output: 95

🏁 Script executed:

# Look for any tests or comments explaining the bug that was fixed
rg -nP 'displayName|getLanguageModelKey' packages/web/src/features/chat/utils.ts -B5 -A5 | head -40

Repository: sourcebot-dev/sourcebot

Length of output: 1070

Chat route has the same bug and needs the same fix.

The chat route at packages/web/src/app/api/(server)/chat/route.ts:70 uses getLanguageModelKey(model) === getLanguageModelKey(languageModel) which breaks when displayName is undefined and multiple configured models share the same provider/model. Since getLanguageModelKey includes displayName in the key (${provider}-${model}-${displayName}), an undefined value creates a key like "provider-model-undefined" that never matches any configured model, causing a 400 error.

The MCP fix at lines 64-67 explicitly handles this by checking if displayName is provided and only accepting a single candidate when it's not. The chat route should be updated to use the same logic.

🤖 Prompt for AI Agents 
Verify each finding against the current code and only fix it if needed.

In `@packages/web/src/features/mcp/askCodebase.ts` around lines 60 - 67, The chat
route currently compares models using getLanguageModelKey(languageModel) which
fails when displayName is undefined; update the matching logic in the chat route
(where configuredModels, languageModel, and getLanguageModelKey are used) to
mirror the MCP fix: filter configuredModels by provider and model to produce
candidates, check if displayName is provided on languageModel, and if so find
the candidate with the same displayName, otherwise only accept a match when
candidates.length === 1; replace the current getLanguageModelKey equality check
with this displayName-aware candidate selection to avoid `"...-undefined"`
mismatches.

if (!matchingModel) {
const available = candidates
.map((m) => m.displayName)
.filter((n): n is string => n !== undefined)
.map((n) => `"${n}"`)
.join(', ');
let message: string;
if (candidates.length === 0) {
message = `Language model '${requestedLanguageModel.provider}/${requestedLanguageModel.model}' is not configured.`;
} else if (displayNameProvided) {
message = `Language model '${requestedLanguageModel.provider}/${requestedLanguageModel.model}' is configured but displayName '${requestedLanguageModel.displayName}' was not found.`
+ (available ? ` Available: ${available}.` : '');
} else {
message = available
? `Multiple configurations found for '${requestedLanguageModel.provider}/${requestedLanguageModel.model}'. Provide a displayName to disambiguate. Available: ${available}.`
: `Multiple configurations found for '${requestedLanguageModel.provider}/${requestedLanguageModel.model}' but none define a displayName. Add a unique displayName to each configuration entry to enable disambiguation.`;
}
return {
statusCode: StatusCodes.BAD_REQUEST,
errorCode: ErrorCode.INVALID_REQUEST_BODY,
message: `Language model '${requestedLanguageModel.provider}/${requestedLanguageModel.model}' is not configured.`,
message,
} satisfies ServiceError;
}
languageModelConfig = matchingModel;
Expand Down
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