diff --git a/infra/env/prod/main.tf b/infra/env/prod/main.tf
index ac7fc1b..9b99ad5 100644
--- a/infra/env/prod/main.tf
+++ b/infra/env/prod/main.tf
@@ -70,6 +70,23 @@ module "sluice" {
   extra_providers               = var.extra_providers
   enable_router_shim            = var.enable_router_shim
   router_shim_tokenutil_package = var.router_shim_tokenutil_package
+
+  custom_domains = var.custom_domains
+}
+
+# Adopt the out-of-band custom-domain binding for sluice.phoenixvc.tech,
+# created 2026-07-03 via `az containerapp hostname add` + `az containerapp
+# hostname bind --validation-method CNAME` (Azure-managed certificate
+# mc-pvc-prod-sluic-sluice-phoenixvc-1673). The first apply after this lands
+# should report "1 to import, 0 to add/change/destroy" for this resource;
+# once the binding is in state the block is a no-op and may be removed.
+#
+# Note: the static segment is `containerApps` (capital A) — the azurerm v4
+# ID parser is case-sensitive and rejects the all-lowercase form that
+# `az containerapp show --query id` returns.
+import {
+  to = module.sluice.azurerm_container_app_custom_domain.custom["sluice.phoenixvc.tech"]
+  id = "/subscriptions/bb4e3882-2079-4bab-8974-611bc0b8bb58/resourceGroups/pvc-prod-sluice-rg/providers/Microsoft.App/containerApps/pvc-prod-sluice-ca/customDomainName/sluice.phoenixvc.tech"
 }
 
 module "state_service" {
diff --git a/infra/env/prod/terraform.tfvars b/infra/env/prod/terraform.tfvars
index ba8cff5..3d9922c 100644
--- a/infra/env/prod/terraform.tfvars
+++ b/infra/env/prod/terraform.tfvars
@@ -65,3 +65,9 @@ enable_litellm_db = true
 #   # Phase 3 — Kimi K2 direct Moonshot path (optional; Groq path uses GROQ_API_KEY above)
 #   moonshot   = { api_key = "sk-...",    env_name = "MOONSHOT_API_KEY" }
 # }
+
+# Custom domain for the gateway. DNS (CNAME + asuid TXT) lives in the
+# org-owned phoenixvc.tech zone in `mys-global-shared-rg` (a different
+# subscription than sluice) and is intentionally not managed by this stack.
+# The Azure-managed certificate was bound out-of-band on 2026-07-03.
+custom_domains = ["sluice.phoenixvc.tech"]
diff --git a/infra/env/prod/variables.tf b/infra/env/prod/variables.tf
index 5791dea..9b63f39 100644
--- a/infra/env/prod/variables.tf
+++ b/infra/env/prod/variables.tf
@@ -329,3 +329,9 @@ variable "extra_providers" {
   default     = {}
   sensitive   = true
 }
+
+variable "custom_domains" {
+  type        = list(string)
+  description = "Pre-verified custom hostnames to bind to the gateway Container App. Each hostname must already have DNS in place (CNAME + asuid TXT in the owning zone) and an Azure-managed certificate provisioned out-of-band via `az containerapp hostname add` + `az containerapp hostname bind` before being listed here."
+  default     = []
+}
diff --git a/infra/modules/sluice_aca/main.tf b/infra/modules/sluice_aca/main.tf
index b45f301..57fe5d8 100644
--- a/infra/modules/sluice_aca/main.tf
+++ b/infra/modules/sluice_aca/main.tf
@@ -1017,3 +1017,26 @@ resource "azurerm_container_app" "ca" {
     }
   }
 }
+
+# Custom domain bindings (e.g. sluice.phoenixvc.tech).
+#
+# DNS is intentionally NOT managed here: the CNAME + `asuid.<host>` TXT
+# records for phoenixvc.tech live in the org-owned DNS zone in
+# `mys-global-shared-rg` (a different subscription / ownership boundary than
+# sluice). Records must exist — and the Azure-managed certificate must be
+# provisioned via `az containerapp hostname add` + `az containerapp hostname
+# bind --validation-method CNAME` — before a hostname is added to
+# var.custom_domains.
+resource "azurerm_container_app_custom_domain" "custom" {
+  for_each         = toset(var.custom_domains)
+  name             = each.value
+  container_app_id = azurerm_container_app.ca.id
+
+  # Azure-managed certificate: provisioned out-of-band by
+  # `az containerapp hostname bind`. azurerm cannot manage managed
+  # certs directly; per provider docs these attributes must be
+  # ignored or every plan tries to unbind the certificate.
+  lifecycle {
+    ignore_changes = [certificate_binding_type, container_app_environment_certificate_id]
+  }
+}
diff --git a/infra/modules/sluice_aca/outputs.tf b/infra/modules/sluice_aca/outputs.tf
index ada712e..d300da1 100644
--- a/infra/modules/sluice_aca/outputs.tf
+++ b/infra/modules/sluice_aca/outputs.tf
@@ -44,3 +44,8 @@ output "application_insights_name" {
   description = "Application Insights resource name. Retrieve connection string from Key Vault secret 'appinsights-connection-string'."
   value       = azurerm_application_insights.ai.name
 }
+
+output "custom_domain_fqdns" {
+  description = "Custom hostnames bound to the gateway Container App (empty when none configured)."
+  value       = [for d in azurerm_container_app_custom_domain.custom : d.name]
+}
diff --git a/infra/modules/sluice_aca/variables.tf b/infra/modules/sluice_aca/variables.tf
index 32d1b91..8f8cd29 100644
--- a/infra/modules/sluice_aca/variables.tf
+++ b/infra/modules/sluice_aca/variables.tf
@@ -316,3 +316,11 @@ variable "otel_service_name" {
   description = "OpenTelemetry service name for tracing."
   default     = "ai-gateway"
 }
+
+# Custom domain bindings — see the azurerm_container_app_custom_domain
+# resource in main.tf for the out-of-band provisioning contract.
+variable "custom_domains" {
+  type        = list(string)
+  description = "Pre-verified custom hostnames to bind to the gateway Container App. Each hostname must already have DNS in place (CNAME + asuid TXT in the owning zone) and an Azure-managed certificate provisioned out-of-band via `az containerapp hostname add` + `az containerapp hostname bind` before being listed here."
+  default     = []
+}