feat(ai): switch xiaomi default to api billing, add per-region token plan providers (#4112)

Built-in `xiaomi` provider now targets the API billing endpoint (https://api.xiaomimimo.com/anthropic) — a single stable URL for keys issued at platform.xiaomimimo.com. The Token Plan endpoints are exposed as three sibling providers, each with its own env var:

- xiaomi-token-plan-cn: XIAOMI_TOKEN_PLAN_CN_API_KEY
- xiaomi-token-plan-ams: XIAOMI_TOKEN_PLAN_AMS_API_KEY
- xiaomi-token-plan-sgp: XIAOMI_TOKEN_PLAN_SGP_API_KEY

BREAKING CHANGE: users who previously set XIAOMI_API_KEY against the Token Plan AMS endpoint must move to xiaomi-token-plan-ams and set XIAOMI_TOKEN_PLAN_AMS_API_KEY. This also resolves the 401 reported by on #4005, where a platform.xiaomimimo.com key fails against the Token Plan endpoint.

closes #4082

packages/coding-agent/src/cli/args.ts

@@ -320,7 +320,10 @@ ${chalk.bold("Environment Variables:")}
   CLOUDFLARE_API_KEY               - Cloudflare API token (Workers AI and AI Gateway)
   CLOUDFLARE_ACCOUNT_ID            - Cloudflare account id (required for both)
   CLOUDFLARE_GATEWAY_ID            - Cloudflare AI Gateway slug (required for AI Gateway)
-  XIAOMI_API_KEY                   - Xiaomi MiMo Token Plan API key
+  XIAOMI_API_KEY                   - Xiaomi MiMo API key (api.xiaomimimo.com billing)
+  XIAOMI_TOKEN_PLAN_CN_API_KEY     - Xiaomi MiMo Token Plan API key (China region)
+  XIAOMI_TOKEN_PLAN_AMS_API_KEY    - Xiaomi MiMo Token Plan API key (Amsterdam region)
+  XIAOMI_TOKEN_PLAN_SGP_API_KEY    - Xiaomi MiMo Token Plan API key (Singapore region)
   AWS_PROFILE                      - AWS profile for Amazon Bedrock
   AWS_ACCESS_KEY_ID                - AWS access key for Amazon Bedrock
   AWS_SECRET_ACCESS_KEY            - AWS secret key for Amazon Bedrock

packages/coding-agent/src/core/model-resolver.ts

@@ -40,6 +40,9 @@ export const defaultModelPerProvider: Record<KnownProvider, string> = {
 	"cloudflare-workers-ai": "@cf/moonshotai/kimi-k2.6",
 	"cloudflare-ai-gateway": "workers-ai/@cf/moonshotai/kimi-k2.6",
 	xiaomi: "mimo-v2.5-pro",
+	"xiaomi-token-plan-cn": "mimo-v2.5-pro",
+	"xiaomi-token-plan-ams": "mimo-v2.5-pro",
+	"xiaomi-token-plan-sgp": "mimo-v2.5-pro",
 };
 
 export interface ScopedModel {

packages/coding-agent/src/core/provider-display-names.ts

@@ -24,5 +24,8 @@ export const BUILT_IN_PROVIDER_DISPLAY_NAMES: Record<string, string> = {
 	"vercel-ai-gateway": "Vercel AI Gateway",
 	xai: "xAI",
 	zai: "ZAI",
-	xiaomi: "Xiaomi MiMo Token Plan",
+	xiaomi: "Xiaomi MiMo",
+	"xiaomi-token-plan-cn": "Xiaomi MiMo Token Plan (China)",
+	"xiaomi-token-plan-ams": "Xiaomi MiMo Token Plan (Amsterdam)",
+	"xiaomi-token-plan-sgp": "Xiaomi MiMo Token Plan (Singapore)",
 };