[Feature] Server-side multi-provider/model support (#583)

* [Feature] Server side multi-pvorider/model support

* copilot suggesition implemented

* feat: improve model selector UI and auto-select default server model

- Replace emoji headers with Lucide icons (Monitor, User)
- Fix transition-all to explicit properties per web guidelines
- Use CSS padding instead of hardcoded space indentation
- Add ModelSelectorSectionHeader component for section headers
- Replace Star icon with "default" text label
- Style Configure button with muted text color
- Auto-select default server model when page loads
- Support AI_MODELS_CONFIG env var for cloud deployments
- Support custom apiKeyEnv/baseUrlEnv per provider config

* docs: update server-side multi-model configuration documentation

- Add AI_MODELS_CONFIG env var option for cloud deployments
- Document apiKeyEnv and baseUrlEnv fields for custom env var names
- Document default field for auto-selecting default model
- Remove deprecated version field from examples
- Add field reference table for clarity

---------

Co-authored-by: dayuan.jiang <jdy.toh@gmail.com>

lib/server-model-config.ts

@@ -0,0 +1,151 @@
+import fs from "fs/promises"
+import path from "path"
+import { z } from "zod"
+import type { ProviderName } from "@/lib/types/model-config"
+import { PROVIDER_INFO } from "@/lib/types/model-config"
+
+export const ProviderNameSchema: z.ZodType<ProviderName> = z
+    .string()
+    .refine((val): val is ProviderName => val in PROVIDER_INFO, {
+        message: "Invalid provider name",
+    })
+
+export const ServerProviderSchema = z.object({
+    name: z.string().min(1),
+    provider: ProviderNameSchema,
+    models: z.array(z.string().min(1)),
+    // Optional: custom environment variable name for API key
+    // e.g., "OPENAI_API_KEY_TEAM_A" instead of default "OPENAI_API_KEY"
+    apiKeyEnv: z.string().min(1).optional(),
+    // Optional: custom environment variable name for base URL
+    baseUrlEnv: z.string().min(1).optional(),
+    // Optional: mark the first model in this provider as the default
+    default: z.boolean().optional(),
+})
+
+export const ServerModelsConfigSchema = z.object({
+    providers: z.array(ServerProviderSchema),
+})
+
+export type ServerProviderConfig = z.infer<typeof ServerProviderSchema>
+export type ServerModelsConfig = z.infer<typeof ServerModelsConfigSchema>
+
+export interface FlattenedServerModel {
+    id: string // "server:<slugified-name>:<modelId>" - name ensures uniqueness for multiple API keys per provider
+    modelId: string
+    provider: ProviderName
+    providerLabel: string
+    isDefault: boolean
+    // Custom env var names for credentials (optional)
+    apiKeyEnv?: string
+    baseUrlEnv?: string
+}
+
+/**
+ * Convert provider name to URL-safe slug for use in model ID
+ * e.g., "OpenAI Production" → "openai-production"
+ */
+function slugify(name: string): string {
+    return name
+        .toLowerCase()
+        .replace(/[^a-z0-9]+/g, "-")
+        .replace(/^-|-$/g, "")
+}
+
+function getConfigPath(): string {
+    const custom = process.env.AI_MODELS_CONFIG_PATH
+    if (custom && custom.trim().length > 0) return custom
+    return path.join(process.cwd(), "ai-models.json")
+}
+
+export async function loadRawServerModelsConfig(): Promise<ServerModelsConfig | null> {
+    // Priority 1: AI_MODELS_CONFIG env var (JSON string) - for cloud deployments
+    const envConfig = process.env.AI_MODELS_CONFIG
+    if (envConfig && envConfig.trim().length > 0) {
+        try {
+            const json = JSON.parse(envConfig)
+            return ServerModelsConfigSchema.parse(json)
+        } catch (err) {
+            console.error(
+                "[server-model-config] Failed to parse AI_MODELS_CONFIG:",
+                err,
+            )
+            return null
+        }
+    }
+
+    // Priority 2: ai-models.json file
+    const configPath = getConfigPath()
+    try {
+        const jsonStr = await fs.readFile(configPath, "utf8")
+        const json = JSON.parse(jsonStr)
+        return ServerModelsConfigSchema.parse(json)
+    } catch (err: any) {
+        if (err?.code === "ENOENT") {
+            return null
+        }
+        console.error(
+            "[server-model-config] Failed to load ai-models.json:",
+            err,
+        )
+        return null
+    }
+}
+
+export async function loadFlattenedServerModels(): Promise<
+    FlattenedServerModel[]
+> {
+    const cfg = await loadRawServerModelsConfig()
+    if (!cfg) return []
+
+    const defaultProvider = process.env.AI_PROVIDER as ProviderName | undefined
+    const defaultModelId = process.env.AI_MODEL
+
+    const flattened: FlattenedServerModel[] = []
+
+    for (const p of cfg.providers) {
+        const providerLabel =
+            p.name || PROVIDER_INFO[p.provider]?.label || p.provider
+
+        // Use slugified name for unique ID (supports multiple API keys per provider)
+        const nameSlug = slugify(p.name)
+
+        for (const modelId of p.models) {
+            const id = `server:${nameSlug}:${modelId}`
+
+            // Default model priority:
+            // 1. From ai-models.json: first model of provider with default: true
+            // 2. From env vars: AI_MODEL matches (legacy behavior)
+            const isDefault =
+                (p.default === true && modelId === p.models[0]) ||
+                (!!defaultModelId &&
+                    modelId === defaultModelId &&
+                    (!defaultProvider || defaultProvider === p.provider))
+
+            flattened.push({
+                id,
+                modelId,
+                provider: p.provider,
+                providerLabel,
+                isDefault,
+                apiKeyEnv: p.apiKeyEnv,
+                baseUrlEnv: p.baseUrlEnv,
+            })
+        }
+    }
+
+    return flattened
+}
+
+/**
+ * Find a server model by its ID (format: "server:<slugified-name>:<modelId>")
+ * Returns the model config including apiKeyEnv/baseUrlEnv if configured
+ */
+export async function findServerModelById(
+    modelId: string,
+): Promise<FlattenedServerModel | null> {
+    if (!modelId.startsWith("server:")) return null
+
+    const models = await loadFlattenedServerModels()
+    return models.find((m) => m.id === modelId) || null
+}