fix: deprecate ai provider seeding env config (#25854)

Environment variables used to configure AI Gateway providers are now deprecated, and we need to reflect this as such.

cli/server.go

@@ -2979,6 +2979,11 @@ func parseExternalAuthProvidersFromEnv(prefix string, environ []string) ([]coder
 	return providers, nil
 }
 
+const (
+	aiGatewayProviderEnvPrefix = "CODER_AI_GATEWAY_PROVIDER_"
+	aiBridgeProviderEnvPrefix  = "CODER_AIBRIDGE_PROVIDER_"
+)
+
 // ReadAIProvidersFromEnv parses CODER_AI_GATEWAY_PROVIDER_<N>_<KEY>
 // environment variables into a slice of AIProviderConfig.
 // Deprecated alias env vars with the CODER_AIBRIDGE_PROVIDER_<N>_<KEY>
@@ -2986,16 +2991,22 @@ func parseExternalAuthProvidersFromEnv(prefix string, environ []string) ([]coder
 //
 // This follows the same indexed pattern as ReadExternalAuthProvidersFromEnv.
 func ReadAIProvidersFromEnv(logger slog.Logger, environ []string) ([]codersdk.AIProviderConfig, error) {
-	providers, err := readAIProvidersForPrefix(logger, environ, "CODER_AIBRIDGE_PROVIDER_")
+	providers, err := readAIProvidersForPrefix(logger, environ, aiBridgeProviderEnvPrefix)
 	if err != nil {
 		return nil, err
 	}
-	gatewayProviders, err := readAIProvidersForPrefix(logger, environ, "CODER_AI_GATEWAY_PROVIDER_")
+	gatewayProviders, err := readAIProvidersForPrefix(logger, environ, aiGatewayProviderEnvPrefix)
 	if err != nil {
 		return nil, err
 	}
 	if len(providers) > 0 && len(gatewayProviders) > 0 {
-		return nil, xerrors.New("cannot mix CODER_AIBRIDGE_PROVIDER_* and CODER_AI_GATEWAY_PROVIDER_* environment variables, please consolidate onto CODER_AI_GATEWAY_PROVIDER_*")
+		return nil, xerrors.Errorf("cannot mix %s* and %s* environment variables, please consolidate onto %s*", aiBridgeProviderEnvPrefix, aiGatewayProviderEnvPrefix, aiGatewayProviderEnvPrefix)
+	}
+	var activePrefix string
+	if len(providers) > 0 {
+		activePrefix = aiBridgeProviderEnvPrefix
+	} else if len(gatewayProviders) > 0 {
+		activePrefix = aiGatewayProviderEnvPrefix
 	}
 	providers = append(providers, gatewayProviders...)
 
@@ -3077,9 +3088,27 @@ func ReadAIProvidersFromEnv(logger slog.Logger, environ []string) ([]codersdk.AI
 		names[p.Name] = i
 	}
 
+	warnIfAIProvidersConfiguredFromEnv(context.Background(), logger, activePrefix, providers)
+
 	return providers, nil
 }
 
+func warnIfAIProvidersConfiguredFromEnv(ctx context.Context, logger slog.Logger, prefix string, providers []codersdk.AIProviderConfig) {
+	if len(providers) == 0 {
+		return
+	}
+
+	if prefix == "" {
+		return
+	}
+
+	logger.Warn(ctx,
+		"ai provider environment variables are deprecated for provider management and only seed provider configuration at startup",
+		slog.F("env_prefix", prefix),
+		slog.F("replacement", "Manage AI Providers from the Coder UI or HTTP API."),
+	)
+}
+
 // readAIProvidersForPrefix parses provider env vars under a single
 // indexed prefix (e.g. CODER_AI_GATEWAY_PROVIDER_) into a slice of
 // AIProviderConfig. Per-field syntax errors and unknown keys are