feat(copilot): add Google Gemini and Mistral as BYOK providers

Both providers wired into the BYOK browser-direct path:
- Google Gemini 2.5 Flash / 2.5 Pro via @ai-sdk/google
- Mistral Small / Large via @ai-sdk/mistral

Picker labels added in all 23 locale files. Demo-proxy path
(DEMO_MODELS + language_model.ts) is intentionally untouched —
adding Gemini/Mistral there is a separate operator decision
since it requires keys in SHARED_API_KEYS and recurring cost.

Author: bendersej

copilot/package-lock.json

@@ -22,6 +22,8 @@
   "dependencies": {
     "@ai-sdk/anthropic": "^3.0.71",
     "@ai-sdk/deepseek": "^2.0.29",
+    "@ai-sdk/google": "^3.0.65",
+    "@ai-sdk/mistral": "^3.0.31",
     "@ai-sdk/openai": "^3.0.53",
     "@ai-sdk/react": "^3.0.170",
     "@aws-sdk/client-s3": "^3.1034.0",

copilot/package.json

@@ -1,5 +1,7 @@
 import { createAnthropic } from '@ai-sdk/anthropic'
 import { createDeepSeek } from '@ai-sdk/deepseek'
+import { createGoogleGenerativeAI } from '@ai-sdk/google'
+import { createMistral } from '@ai-sdk/mistral'
 import { createOpenAI } from '@ai-sdk/openai'
 import type { ByokConfig } from './providers'
 
@@ -25,6 +27,14 @@ export const buildBrowserModel = (config: ByokConfig) => {
       const deepseek = createDeepSeek({ apiKey: config.apiKey })
       return deepseek(config.model)
     }
+    case 'google': {
+      const google = createGoogleGenerativeAI({ apiKey: config.apiKey })
+      return google(config.model)
+    }
+    case 'mistral': {
+      const mistral = createMistral({ apiKey: config.apiKey })
+      return mistral(config.model)
+    }
     case 'custom':
       return buildCustomModel(config)
     default:

copilot/src/lib/byok/model.ts

@@ -1,6 +1,6 @@
 import { z } from 'zod'
 
-export type ByokProviderId = 'openai' | 'anthropic' | 'deepseek' | 'custom'
+export type ByokProviderId = 'openai' | 'anthropic' | 'deepseek' | 'google' | 'mistral' | 'custom'
 type UnsupportedProviderId = 'azure' | 'bedrock'
 
 export type ByokModel = {
@@ -43,7 +43,7 @@ const CustomInstructionsSchema: z.ZodType<CustomInstructions> = z.object({
 // this schema.
 export const ByokConfigSchema: z.ZodType<ByokConfig> = z.discriminatedUnion('provider', [
   z.object({
-    provider: z.enum(['openai', 'anthropic', 'deepseek']),
+    provider: z.enum(['openai', 'anthropic', 'deepseek', 'google', 'mistral']),
     model: z.string().min(1),
     apiKey: z.string(),
     customInstructions: CustomInstructionsSchema.nullable(),
@@ -146,6 +146,46 @@ export const PROVIDER_ENTRIES: ProviderEntry[] = [
       },
     ],
   },
+  {
+    id: 'google',
+    kind: 'catalog',
+    labelKey: 'chat.modelPicker.providerGoogle',
+    supported: true,
+    models: [
+      {
+        id: 'gemini-2.5-flash',
+        label: 'Gemini 2.5 Flash',
+        description: 'Fast and inexpensive. Fine for most form-filling.',
+        recommended: true,
+      },
+      {
+        id: 'gemini-2.5-pro',
+        label: 'Gemini 2.5 Pro',
+        description: 'Higher reasoning for tricky forms',
+        recommended: false,
+      },
+    ],
+  },
+  {
+    id: 'mistral',
+    kind: 'catalog',
+    labelKey: 'chat.modelPicker.providerMistral',
+    supported: true,
+    models: [
+      {
+        id: 'mistral-small-latest',
+        label: 'Mistral Small',
+        description: 'Fast and inexpensive. Fine for most form-filling.',
+        recommended: true,
+      },
+      {
+        id: 'mistral-large-latest',
+        label: 'Mistral Large',
+        description: 'Higher reasoning for tricky forms',
+        recommended: false,
+      },
+    ],
+  },
   {
     id: 'custom',
     kind: 'custom',

copilot/src/lib/byok/providers.ts

@@ -93,6 +93,8 @@
       "providerOpenai": "OpenAI",
       "providerAnthropic": "Anthropic",
       "providerDeepseek": "DeepSeek",
+      "providerGoogle": "Google Gemini",
+      "providerMistral": "Mistral",
       "providerCustom": "نقطة نهاية مخصصة",
       "providerAzure": "Azure OpenAI",
       "providerBedrock": "AWS Bedrock",

copilot/src/locales/ar.json

@@ -93,6 +93,8 @@
       "providerOpenai": "OpenAI",
       "providerAnthropic": "Anthropic",
       "providerDeepseek": "DeepSeek",
+      "providerGoogle": "Google Gemini",
+      "providerMistral": "Mistral",
       "providerCustom": "Vlastní endpoint",
       "providerAzure": "Azure OpenAI",
       "providerBedrock": "AWS Bedrock",

copilot/src/locales/cs.json

@@ -93,6 +93,8 @@
       "providerOpenai": "OpenAI",
       "providerAnthropic": "Anthropic",
       "providerDeepseek": "DeepSeek",
+      "providerGoogle": "Google Gemini",
+      "providerMistral": "Mistral",
       "providerCustom": "Brugerdefineret endpoint",
       "providerAzure": "Azure OpenAI",
       "providerBedrock": "AWS Bedrock",

copilot/src/locales/da.json

@@ -93,6 +93,8 @@
       "providerOpenai": "OpenAI",
       "providerAnthropic": "Anthropic",
       "providerDeepseek": "DeepSeek",
+      "providerGoogle": "Google Gemini",
+      "providerMistral": "Mistral",
       "providerCustom": "Benutzerdefinierter Endpunkt",
       "providerAzure": "Azure OpenAI",
       "providerBedrock": "AWS Bedrock",

copilot/src/locales/de.json

@@ -93,6 +93,8 @@
       "providerOpenai": "OpenAI",
       "providerAnthropic": "Anthropic",
       "providerDeepseek": "DeepSeek",
+      "providerGoogle": "Google Gemini",
+      "providerMistral": "Mistral",
       "providerCustom": "Προσαρμοσμένο endpoint",
       "providerAzure": "Azure OpenAI",
       "providerBedrock": "AWS Bedrock",

copilot/src/locales/el.json

@@ -94,6 +94,8 @@
       "providerOpenai": "OpenAI",
       "providerAnthropic": "Anthropic",
       "providerDeepseek": "DeepSeek",
+      "providerGoogle": "Google Gemini",
+      "providerMistral": "Mistral",
       "providerCustom": "Custom endpoint",
       "providerAzure": "Azure OpenAI",
       "providerBedrock": "AWS Bedrock",