diff --git a/.github/workflows/validate.yaml b/.github/workflows/validate.yaml
index 87aaa17..92a2d31 100644
--- a/.github/workflows/validate.yaml
+++ b/.github/workflows/validate.yaml
@@ -12,14 +12,28 @@ jobs:
   validate:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v7
+
+      - uses: actions/checkout@v7
+        with:
+          repository: justgithubaccount/app-poly-gitops-k8s
+          ref: main
+          path: downstream-k8s
 
       - uses: azure/setup-helm@v4
         with:
           version: v3.19.0
 
+      - name: Install validation tools
+        run: |
+          python3 -m pip install --disable-pip-version-check PyYAML==6.0.3
+          curl --fail --location --silent --show-error \
+            https://github.com/yannh/kubeconform/releases/download/v0.7.0/kubeconform-linux-amd64.tar.gz \
+            | tar -xz kubeconform
+          sudo mv kubeconform /usr/local/bin/kubeconform
+
       - name: Chart contract
         run: bash tests/test_chart.sh
 
-      - name: Render standalone chart
-        run: helm template chat-api . --namespace smoke >/dev/null
+      - name: Current GitOps consumer layering
+        run: bash tests/test_downstream.sh downstream-k8s
diff --git a/Chart.yaml b/Chart.yaml
index 54aab3d..9a12a90 100644
--- a/Chart.yaml
+++ b/Chart.yaml
@@ -1,6 +1,6 @@
 apiVersion: v2
 name: chat-api
-description: ai-app (mind)
+description: Helm chart for the FastAPI Chat API service
 type: application
 version: 0.4.1
 appVersion: "1.1.2"
diff --git a/README.md b/README.md
index 2b3d593..eeec456 100644
--- a/README.md
+++ b/README.md
@@ -19,6 +19,17 @@ Real model requests require a secret selected with
 `postgresSecretRefName` or explicit `extraEnv` entries.
 Use an external database when data must survive pod replacement.
 
+`serviceAccount.create=true` creates and selects one ServiceAccount. Set
+`serviceAccount.name` to override its name. With `serviceAccount.create=false`,
+`serviceAccount.name` is required and must identify an existing account.
+
+`createInternalSecret=true` creates a chart-managed Secret for the non-sensitive
+provider URL, model and optional attribution headers, and attaches it to the
+Deployment. It does not store a provider key. `postgres.externalService.enabled`
+only creates the stable `postgres-external` DNS name for an external host; it
+cannot construct credentials or a database name, so `DATABASE_URL` must still be
+provided through `postgresSecretRefName` or `extraEnv`.
+
 ## Getting started
 
 Requirements: Helm 3 and access to a Kubernetes cluster for installation.
@@ -65,6 +76,10 @@ helm upgrade --install chat-api . \
 | `openrouter.defaultModel` | `anthropic/claude-opus-4` | Model identifier |
 | `openrouterSecretRefName` | empty | Existing provider Secret |
 | `postgresSecretRefName` | empty | Existing database Secret |
+| `serviceAccount.create` | `true` | Create a ServiceAccount |
+| `serviceAccount.name` | empty | Created-account override, or required existing account name |
+| `createInternalSecret` | `false` | Create and consume non-sensitive provider configuration |
+| `postgres.externalService.enabled` | `false` | Create an ExternalName Service; does not set `DATABASE_URL` |
 | `ingress.enabled` | `false` | Render an Ingress |
 | `extraEnv` | `[]` | Additional container environment entries |
 
@@ -77,11 +92,13 @@ Ingress options, and the complete value set.
 - `values.yaml` — default values
 - `templates/` — Kubernetes templates
 - `tests/test_chart.sh` — lint and rendered-contract checks
+- `tests/test_downstream.sh` — current GitOps values and chart-pin compatibility
 
 Run the repository check with:
 
 ~~~bash
 bash tests/test_chart.sh
+bash tests/test_downstream.sh ../app-poly-gitops-k8s
 ~~~
 
 ## Related repositories
diff --git a/templates/_helpers.tpl b/templates/_helpers.tpl
index 4111f21..d2925ed 100644
--- a/templates/_helpers.tpl
+++ b/templates/_helpers.tpl
@@ -19,6 +19,14 @@
 {{- default .Release.Namespace .Values.namespace -}}
 {{- end }}
 
+{{- define "chat-api.serviceAccountName" -}}
+{{- if .Values.serviceAccount.create -}}
+{{- default (include "chat-api.fullname" .) .Values.serviceAccount.name -}}
+{{- else -}}
+{{- required "serviceAccount.name is required when serviceAccount.create=false" .Values.serviceAccount.name -}}
+{{- end -}}
+{{- end }}
+
 {{- define "chat-api.chart" -}}
 {{- printf "%s-%s" .Chart.Name .Chart.Version | replace "+" "_" | trunc 63 | trimSuffix "-" }}
 {{- end }}
diff --git a/templates/deployment.yaml b/templates/deployment.yaml
index a024ae6..93ea5b1 100644
--- a/templates/deployment.yaml
+++ b/templates/deployment.yaml
@@ -17,7 +17,7 @@ spec:
       annotations:
         openrouter.model: {{ .Values.openrouter.defaultModel | quote }}
     spec:
-      serviceAccountName: {{ include "chat-api.fullname" . }}
+      serviceAccountName: {{ include "chat-api.serviceAccountName" . }}
       containers:
         - name: chat-api
           image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
@@ -69,8 +69,12 @@ spec:
             {{- toYaml . | nindent 12 }}
             {{- end }}
 
-          {{- if or .Values.openrouterSecretRefName .Values.postgresSecretRefName }}
+          {{- if or .Values.createInternalSecret .Values.openrouterSecretRefName .Values.postgresSecretRefName }}
           envFrom:
+            {{- if .Values.createInternalSecret }}
+            - secretRef:
+                name: {{ include "chat-api.fullname" . }}-config
+            {{- end }}
             {{- if .Values.openrouterSecretRefName }}
             - secretRef:
                 name: {{ .Values.openrouterSecretRefName }}
diff --git a/templates/ingress.yaml b/templates/ingress.yaml
index ac3853b..8d1cdc1 100644
--- a/templates/ingress.yaml
+++ b/templates/ingress.yaml
@@ -13,7 +13,7 @@ metadata:
 spec:
   ingressClassName: {{ .Values.ingress.className | default "nginx" }}
   rules:
-    - host: {{ .Values.ingress.host | quote }}
+    - host: {{ required "ingress.host is required when ingress.enabled=true" .Values.ingress.host | quote }}
       http:
         paths:
           - path: {{ .Values.ingress.path | default "/" | quote }}
diff --git a/templates/pg-service.yaml b/templates/pg-service.yaml
index 921bf39..3308b09 100644
--- a/templates/pg-service.yaml
+++ b/templates/pg-service.yaml
@@ -9,7 +9,7 @@ metadata:
     component: database
 spec:
   type: ExternalName
-  externalName: {{ .Values.postgres.externalService.host }}
+  externalName: {{ required "postgres.externalService.host is required when postgres.externalService.enabled=true" .Values.postgres.externalService.host }}
   ports:
   - port: {{ .Values.postgres.externalService.port }}
     targetPort: {{ .Values.postgres.externalService.port }}
diff --git a/templates/serviceaccount.yaml b/templates/serviceaccount.yaml
index fe68d27..5eab9ad 100644
--- a/templates/serviceaccount.yaml
+++ b/templates/serviceaccount.yaml
@@ -2,7 +2,7 @@
 apiVersion: v1
 kind: ServiceAccount
 metadata:
-  name: {{ include "chat-api.fullname" . }}
+  name: {{ include "chat-api.serviceAccountName" . }}
   namespace: {{ include "chat-api.namespace" . }}
   labels:
     {{- include "chat-api.labels" . | nindent 4 }}
diff --git a/tests/test_chart.sh b/tests/test_chart.sh
index bc3b629..8c04861 100755
--- a/tests/test_chart.sh
+++ b/tests/test_chart.sh
@@ -2,14 +2,104 @@
 set -euo pipefail
 
 repo_root="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+tmp_dir="$(mktemp -d)"
+trap 'rm -rf "${tmp_dir}"' EXIT
+
+render() {
+  helm template chat-api "${repo_root}" --namespace smoke "$@"
+}
+
+assert_yaml_resources() {
+  python3 - "$1" <<'PY'
+import pathlib
+import sys
+
+import yaml
+
+documents = list(yaml.safe_load_all(pathlib.Path(sys.argv[1]).read_text()))
+resources = [document for document in documents if document is not None]
+assert resources, "render did not contain Kubernetes resources"
+for resource in resources:
+    assert isinstance(resource, dict), resource
+    assert resource.get("apiVersion"), resource
+    assert resource.get("kind"), resource
+    assert isinstance(resource.get("metadata"), dict), resource
+    assert resource["metadata"].get("name"), resource
+PY
+}
 
 helm lint "${repo_root}"
-rendered="$(helm template chat-api "${repo_root}" --namespace smoke)"
 
-grep -q 'namespace: smoke' <<<"${rendered}"
-grep -q 'image: "ghcr.io/justgithubaccount/app-poly-gitops-fastapi:1.1.2"' <<<"${rendered}"
-! grep -q 'secretRef:' <<<"${rendered}"
-! grep -q 'command:' <<<"${rendered}"
+default_render="${tmp_dir}/default.yaml"
+render > "${default_render}"
+assert_yaml_resources "${default_render}"
+test "$(sha256sum "${default_render}" | cut -d' ' -f1)" = \
+  "eccee8f126eec4287d1ccf664414f73632b70a6dfa46357b8c31f7d54e96637f"
+grep -q 'namespace: smoke' "${default_render}"
+grep -q 'image: "ghcr.io/justgithubaccount/app-poly-gitops-fastapi:1.1.2"' "${default_render}"
+! grep -q 'secretRef:' "${default_render}"
+! grep -q 'command:' "${default_render}"
+! grep -q '^kind: Ingress$' "${default_render}"
+
+created_sa="${tmp_dir}/created-sa.yaml"
+render --set serviceAccount.name=existing-compatible-name > "${created_sa}"
+test "$(grep -c '^kind: ServiceAccount$' "${created_sa}")" -eq 1
+grep -q 'name: existing-compatible-name' "${created_sa}"
+grep -q 'serviceAccountName: existing-compatible-name' "${created_sa}"
+
+existing_sa="${tmp_dir}/existing-sa.yaml"
+render --set serviceAccount.create=false --set serviceAccount.name=precreated-chat-api > "${existing_sa}"
+! grep -q '^kind: ServiceAccount$' "${existing_sa}"
+grep -q 'serviceAccountName: precreated-chat-api' "${existing_sa}"
+
+if render --set serviceAccount.create=false --set-string serviceAccount.name= \
+  > "${tmp_dir}/invalid-sa.yaml" 2> "${tmp_dir}/invalid-sa.err"; then
+  echo "serviceAccount.create=false without serviceAccount.name unexpectedly rendered" >&2
+  exit 1
+fi
+grep -q 'serviceAccount.name is required' "${tmp_dir}/invalid-sa.err"
+
+internal_secret="${tmp_dir}/internal-secret.yaml"
+render --set createInternalSecret=true > "${internal_secret}"
+grep -q '^kind: Secret$' "${internal_secret}"
+grep -A3 'envFrom:' "${internal_secret}" | grep -q 'name: chat-api-config'
+
+external_postgres="${tmp_dir}/external-postgres.yaml"
+render \
+  --set postgres.externalService.enabled=true \
+  --set postgres.externalService.host=db.example.internal \
+  > "${external_postgres}"
+grep -q '^kind: Service$' "${external_postgres}"
+grep -q 'externalName: db.example.internal' "${external_postgres}"
+! grep -q 'name: DATABASE_URL' "${external_postgres}"
+if render --set postgres.externalService.enabled=true \
+  > "${tmp_dir}/invalid-postgres.yaml" 2> "${tmp_dir}/invalid-postgres.err"; then
+  echo "external Postgres service without a host unexpectedly rendered" >&2
+  exit 1
+fi
+grep -q 'postgres.externalService.host is required' "${tmp_dir}/invalid-postgres.err"
+
+ingress="${tmp_dir}/ingress.yaml"
+render \
+  --set namespace=application \
+  --set ingress.enabled=true \
+  --set ingress.host=chat.example.test \
+  > "${ingress}"
+grep -q '^kind: Ingress$' "${ingress}"
+grep -A5 '^kind: Ingress$' "${ingress}" | grep -q 'namespace: application'
+grep -q 'host: "chat.example.test"' "${ingress}"
+if render --set ingress.enabled=true \
+  > "${tmp_dir}/invalid-ingress.yaml" 2> "${tmp_dir}/invalid-ingress.err"; then
+  echo "enabled ingress without a host unexpectedly rendered" >&2
+  exit 1
+fi
+grep -q 'ingress.host is required' "${tmp_dir}/invalid-ingress.err"
+
+for manifest in "${default_render}" "${created_sa}" "${existing_sa}" \
+  "${internal_secret}" "${external_postgres}" "${ingress}"; do
+  assert_yaml_resources "${manifest}"
+  kubeconform -strict -summary -ignore-missing-schemas "${manifest}"
+done
 
 workflow="${repo_root}/.github/workflows/validate.yaml"
 test -f "${workflow}"
diff --git a/tests/test_downstream.sh b/tests/test_downstream.sh
new file mode 100644
index 0000000..d483f74
--- /dev/null
+++ b/tests/test_downstream.sh
@@ -0,0 +1,17 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+repo_root="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+k8s_repo="${1:?usage: tests/test_downstream.sh /path/to/app-poly-gitops-k8s}"
+application="${k8s_repo}/tenants/product-team/apps/chat/base/application.yaml"
+values="${k8s_repo}/tenants/product-team/apps/chat/overlays/dev/values.yaml"
+
+test -f "${application}"
+test -f "${values}"
+grep -q 'repoURL: https://github.com/justgithubaccount/app-poly-gitops-helm' "${application}"
+grep -q 'targetRevision: v0.4.1' "${application}"
+
+rendered="$(helm template chat-api "${repo_root}" --namespace product-team -f "${values}")"
+grep -q 'namespace: product-team' <<<"${rendered}"
+grep -q 'image: "ghcr.io/justgithubaccount/app-poly-gitops-fastapi:1.1.2"' <<<"${rendered}"
+grep -q 'serviceAccountName: chat-api' <<<"${rendered}"
diff --git a/values.yaml b/values.yaml
index f3fab3b..1bb0690 100644
--- a/values.yaml
+++ b/values.yaml
@@ -29,6 +29,7 @@ livenessProbe:
 serviceAccount:
   create: true
   annotations: {}
+  # Required when create=false. When create=true, empty uses the chart fullname.
   name: ""
 
 env:
@@ -54,6 +55,8 @@ postgresSecretRefName: ""
 
 postgres:
   externalService:
+    # Creates only an ExternalName Service. Supply DATABASE_URL separately with
+    # postgresSecretRefName or extraEnv; credentials are intentionally not built here.
     enabled: false
     host: ""
     port: 5432
@@ -69,4 +72,6 @@ ingress:
 # Additional container environment entries, including Secret key mappings.
 extraEnv: []
 
+# Creates and consumes a chart-managed Secret for non-sensitive provider config.
+# Provider credentials still belong in openrouterSecretRefName or extraEnv.
 createInternalSecret: false