fix: strip markdown code fences from LLM JSON responses (fixes #959)

src/lib/models/providers/ollama/ollamaLLM.ts

@@ -12,6 +12,7 @@ import { parse } from 'partial-json';
 import crypto from 'crypto';
 import { Message } from '@/lib/types';
 import { repairJson } from '@toolsycc/json-repair';
+import { stripMarkdownFences } from '@/lib/utils/parseJson';
 
 type OllamaConfig = {
   baseURL: string;
@@ -249,7 +250,7 @@ class OllamaLLM extends BaseLLM<OllamaConfig> {
       recievedObj += chunk.message.content;
 
       try {
-        yield parse(recievedObj) as T;
+        yield parse(stripMarkdownFences(recievedObj)) as T;
       } catch (err) {
         console.log('Error parsing partial object from Ollama:', err);
         yield {} as T;

src/lib/models/providers/openai/openaiLLM.ts

@@ -19,6 +19,7 @@ import {
 } from 'openai/resources/index.mjs';
 import { Message } from '@/lib/types';
 import { repairJson } from '@toolsycc/json-repair';
+import { safeParseJson, stripMarkdownFences } from '@/lib/utils/parseJson';
 
 type OpenAIConfig = {
   apiKey: string;
@@ -110,7 +111,7 @@ class OpenAILLM extends BaseLLM<OpenAIConfig> {
                 return {
                   name: tc.function.name,
                   id: tc.id,
-                  arguments: JSON.parse(tc.function.arguments),
+                  arguments: safeParseJson(tc.function.arguments),
                 };
               }
             })
@@ -256,14 +257,14 @@ class OpenAILLM extends BaseLLM<OpenAIConfig> {
         recievedObj += chunk.delta;
 
         try {
-          yield parse(recievedObj) as T;
+          yield parse(stripMarkdownFences(recievedObj)) as T;
         } catch (err) {
           console.log('Error parsing partial object from OpenAI:', err);
           yield {} as T;
         }
       } else if (chunk.type === 'response.output_text.done' && chunk.text) {
         try {
-          yield parse(chunk.text) as T;
+          yield parse(stripMarkdownFences(chunk.text)) as T;
         } catch (err) {
           throw new Error(`Error parsing response from OpenAI: ${err}`);
         }

src/lib/utils/parseJson.ts

@@ -0,0 +1,21 @@
+/**
+ * Strips markdown code fences that some LLM providers (Claude, models via
+ * LiteLLM/OpenRouter) wrap around JSON output.
+ *
+ * Handles ```json ... ```, ``` ... ```, and raw JSON (no-op).
+ */
+export function stripMarkdownFences(text: string): string {
+  return text
+    .trim()
+    .replace(/^```(?:json)?\s*/i, '')
+    .replace(/\s*```$/, '')
+    .trim();
+}
+
+/**
+ * Strips markdown code fences from LLM output before JSON.parse.
+ * Fixes issue #959: Claude/LiteLLM models wrap JSON in markdown blocks.
+ */
+export function safeParseJson<T>(text: string): T {
+  return JSON.parse(stripMarkdownFences(text)) as T;
+}