Reduce AI costs: switch tagging to gpt-4o-mini, add custom base URL support

- Change AI tagging to use AI_MODELS.QUICK (gpt-4o-mini) instead of gpt-4o for
  10-15x cost reduction on classification tasks
- Add openai_base_url system setting for OpenAI-compatible providers
  (OpenRouter, Groq, Together AI, local models)
- Reset OpenAI client singleton when API key, base URL, or model changes
- Add base URL field to AI settings form with provider examples

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/components/settings/ai-settings-form.tsx

@@ -36,6 +36,7 @@ const formSchema = z.object({
   ai_model: z.string(),
   ai_send_descriptions: z.boolean(),
   openai_api_key: z.string().optional(),
+  openai_base_url: z.string().optional(),
 })
 
 type FormValues = z.infer<typeof formSchema>
@@ -47,6 +48,7 @@ interface AISettingsFormProps {
     ai_model?: string
     ai_send_descriptions?: string
     openai_api_key?: string
+    openai_base_url?: string
   }
 }
 
@@ -61,6 +63,7 @@ export function AISettingsForm({ settings }: AISettingsFormProps) {
       ai_model: settings.ai_model || 'gpt-4o',
       ai_send_descriptions: settings.ai_send_descriptions === 'true',
       openai_api_key: '',
+      openai_base_url: settings.openai_base_url || '',
     },
   })
 
@@ -113,6 +116,9 @@ export function AISettingsForm({ settings }: AISettingsFormProps) {
       settingsToUpdate.push({ key: 'openai_api_key', value: data.openai_api_key })
     }
 
+    // Save base URL (empty string clears it)
+    settingsToUpdate.push({ key: 'openai_base_url', value: data.openai_base_url?.trim() || '' })
+
     updateSettings.mutate({ settings: settingsToUpdate })
   }
 
@@ -208,6 +214,27 @@ export function AISettingsForm({ settings }: AISettingsFormProps) {
           )}
         />
 
+        <FormField
+          control={form.control}
+          name="openai_base_url"
+          render={({ field }) => (
+            <FormItem>
+              <FormLabel>API Base URL (Optional)</FormLabel>
+              <FormControl>
+                <Input
+                  placeholder="https://api.openai.com/v1"
+                  {...field}
+                />
+              </FormControl>
+              <FormDescription>
+                Custom base URL for OpenAI-compatible providers. Leave blank for OpenAI.
+                Use <code className="text-xs bg-muted px-1 rounded">https://openrouter.ai/api/v1</code> for OpenRouter (access Claude, Gemini, Llama, etc.)
+              </FormDescription>
+              <FormMessage />
+            </FormItem>
+          )}
+        />
+
         <FormField
           control={form.control}
           name="ai_model"

src/components/settings/settings-content.tsx

@@ -84,6 +84,7 @@ export function SettingsContent({ initialSettings, isSuperAdmin = true }: Settin
     'ai_model',
     'ai_send_descriptions',
     'openai_api_key',
+    'openai_base_url',
   ])
 
   const brandingSettings = getSettingsByKeys([

src/lib/openai.ts

@@ -187,7 +187,25 @@ async function getOpenAIApiKey(): Promise<string | null> {
 }
 
 /**
- * Create OpenAI client instance
+ * Get custom base URL for OpenAI-compatible providers.
+ * Supports OpenRouter, Together AI, Groq, local models, etc.
+ * Set via Settings → AI or OPENAI_BASE_URL env var.
+ */
+async function getBaseURL(): Promise<string | undefined> {
+  try {
+    const setting = await prisma.systemSettings.findUnique({
+      where: { key: 'openai_base_url' },
+    })
+    return setting?.value || process.env.OPENAI_BASE_URL || undefined
+  } catch {
+    return process.env.OPENAI_BASE_URL || undefined
+  }
+}
+
+/**
+ * Create OpenAI client instance.
+ * Supports custom baseURL for OpenAI-compatible providers
+ * (OpenRouter, Groq, Together AI, local models, etc.)
  */
 async function createOpenAIClient(): Promise<OpenAI | null> {
   const apiKey = await getOpenAIApiKey()
@@ -197,8 +215,15 @@ async function createOpenAIClient(): Promise<OpenAI | null> {
     return null
   }
 
+  const baseURL = await getBaseURL()
+
+  if (baseURL) {
+    console.log(`[OpenAI] Using custom base URL: ${baseURL}`)
+  }
+
   return new OpenAI({
     apiKey,
+    ...(baseURL ? { baseURL } : {}),
   })
 }
 
@@ -221,6 +246,15 @@ export async function getOpenAI(): Promise<OpenAI | null> {
   return client
 }
 
+/**
+ * Reset the OpenAI client singleton (e.g., after settings change).
+ * Next call to getOpenAI() will create a fresh client.
+ */
+export function resetOpenAIClient(): void {
+  globalForOpenAI.openai = undefined
+  globalForOpenAI.openaiInitialized = false
+}
+
 /**
  * Check if OpenAI is configured and available
  */

src/server/routers/settings.ts

@@ -201,6 +201,12 @@ export const settingsRouter = router({
         clearStorageProviderCache()
       }
 
+      // Reset OpenAI client if API key or base URL changed
+      if (input.settings.some((s) => s.key === 'openai_api_key' || s.key === 'openai_base_url' || s.key === 'ai_model')) {
+        const { resetOpenAIClient } = await import('@/lib/openai')
+        resetOpenAIClient()
+      }
+
       // Audit log
       await logAudit({
         prisma: ctx.prisma,

src/server/services/ai-tagging.ts

@@ -16,7 +16,7 @@
  */
 
 import { prisma } from '@/lib/prisma'
-import { getOpenAI, getConfiguredModel, buildCompletionParams } from '@/lib/openai'
+import { getOpenAI, getConfiguredModel, buildCompletionParams, AI_MODELS } from '@/lib/openai'
 import { logAIUsage, extractTokenUsage } from '@/server/utils/ai-usage'
 import { classifyAIError, createParseError, logAIError } from './ai-errors'
 import {
@@ -178,7 +178,8 @@ async function getAISuggestions(
     return { suggestions: [], tokensUsed: 0 }
   }
 
-  const model = await getConfiguredModel()
+  // Use QUICK model — tag classification is simple, doesn't need expensive reasoning
+  const model = await getConfiguredModel(AI_MODELS.QUICK)
 
   // Build compact tag list for prompt
   const tagList = availableTags.map((t) => ({
@@ -294,7 +295,8 @@ async function getAISuggestionsBatch(
     return { suggestionsMap: new Map(), tokensUsed: 0 }
   }
 
-  const model = await getConfiguredModel()
+  // Use QUICK model — tag classification is simple, doesn't need expensive reasoning
+  const model = await getConfiguredModel(AI_MODELS.QUICK)
   const suggestionsMap = new Map<string, TagSuggestion[]>()
 
   // Build compact tag list (sent once for entire batch)