diff --git a/Makefile b/Makefile
index 60a7c98..deb9acd 100644
--- a/Makefile
+++ b/Makefile
@@ -143,6 +143,17 @@ provision-custodian-agent-host: ## Deploy custodian agent key to one host: make
 	cd ansible && ansible-playbook playbooks/custodian-agent.yaml -u $(SSH_USER) \
 	  --limit "$(HOST)"
 
+bootstrap-ssh-ca: ## Deploy OpenBao SSH CA trust + auth_principals: make bootstrap-ssh-ca SSH_CA_PUBKEY=/path/to/ca_user.pub
+	@test -n "$(SSH_CA_PUBKEY)" || (echo "Usage: make bootstrap-ssh-ca SSH_CA_PUBKEY=/path/to/ca_user.pub [HOST=Railiance01]"; exit 1)
+	cd ansible && ansible-playbook playbooks/bootstrap-ssh-ca.yaml -u $(SSH_USER) \
+	  -e ssh_ca_pubkey_path="$(SSH_CA_PUBKEY)" \
+	  $(if $(HOST),--limit "$(HOST)",)
+
+bootstrap-ssh-ca-host: ## Deploy SSH CA trust to one host: make bootstrap-ssh-ca-host HOST=Railiance01 SSH_CA_PUBKEY=...
+	@test -n "$(HOST)" && test -n "$(SSH_CA_PUBKEY)" || \
+	  (echo "Usage: make bootstrap-ssh-ca-host HOST=Railiance01 SSH_CA_PUBKEY=/path/to/ca_user.pub"; exit 1)
+	$(MAKE) bootstrap-ssh-ca SSH_CA_PUBKEY="$(SSH_CA_PUBKEY)" HOST="$(HOST)"
+
 # ---- Orchestration ----
 apply: tf-fmt tf-apply ansible-bootstrap ## Provision via Terraform then converge via Ansible
 
diff --git a/ansible/inventory/ssh_principals.yaml b/ansible/inventory/ssh_principals.yaml
new file mode 100644
index 0000000..8b6c087
--- /dev/null
+++ b/ansible/inventory/ssh_principals.yaml
@@ -0,0 +1,19 @@
+# Central SSH certificate principals inventory — synced with ops-warden actor
+# principals (wiki/ActorInventoryPatterns.md). Public data only.
+
+ssh_principals:
+  CoulombCore:
+    users:
+      tegwick:
+        - agt-task-bridge
+        - agt-interhub-bootstrap
+        - adm-full
+        - atm-backup-daily
+
+  Railiance01:
+    users:
+      tegwick:
+        - agt-task-bridge
+        - agt-interhub-bootstrap
+        - adm-full
+        - atm-backup-daily
diff --git a/ansible/playbooks/bootstrap-ssh-ca.yaml b/ansible/playbooks/bootstrap-ssh-ca.yaml
new file mode 100644
index 0000000..efccfb9
--- /dev/null
+++ b/ansible/playbooks/bootstrap-ssh-ca.yaml
@@ -0,0 +1,19 @@
+---
+# Deploy OpenBao SSH user CA trust and per-user auth_principals.
+#
+# Prerequisite: railiance-platform openbao-configure-ssh (exports CA pubkey).
+#
+#   cd ~/railiance-platform
+#   OPENBAO_TOKEN_FILE=~/.local/openbao/platform-admin.token \
+#     OPENBAO_SSH_CA_PUBKEY_OUT=/tmp/openbao-ssh-ca.pub \
+#     make openbao-configure-ssh
+#
+#   cd ~/railiance-infra
+#   make bootstrap-ssh-ca SSH_CA_PUBKEY=/tmp/openbao-ssh-ca.pub
+
+- hosts: all
+  become: true
+  vars_files:
+    - ../inventory/ssh_principals.yaml
+  roles:
+    - role: ssh_ca_host
diff --git a/ansible/roles/ssh_ca_host/handlers/main.yml b/ansible/roles/ssh_ca_host/handlers/main.yml
new file mode 100644
index 0000000..cad74d8
--- /dev/null
+++ b/ansible/roles/ssh_ca_host/handlers/main.yml
@@ -0,0 +1,5 @@
+---
+- name: Restart sshd
+  ansible.builtin.service:
+    name: ssh
+    state: restarted
diff --git a/ansible/roles/ssh_ca_host/tasks/main.yml b/ansible/roles/ssh_ca_host/tasks/main.yml
new file mode 100644
index 0000000..daae6ef
--- /dev/null
+++ b/ansible/roles/ssh_ca_host/tasks/main.yml
@@ -0,0 +1,85 @@
+---
+- name: Require SSH CA public key path
+  ansible.builtin.assert:
+    that:
+      - ssh_ca_pubkey_path is defined
+      - ssh_ca_pubkey_path | length > 0
+    fail_msg: >-
+      Set ssh_ca_pubkey_path to the OpenBao SSH CA public key file
+      (from railiance-platform openbao-configure-ssh).
+
+- name: Stat SSH CA public key source
+  ansible.builtin.stat:
+    path: "{{ ssh_ca_pubkey_path }}"
+  delegate_to: localhost
+  become: false
+  register: ssh_ca_pubkey_stat
+
+- name: Fail when SSH CA public key is missing
+  ansible.builtin.fail:
+    msg: "SSH CA public key not found on controller: {{ ssh_ca_pubkey_path }}"
+  when: not ssh_ca_pubkey_stat.stat.exists
+
+- name: Ensure SSH CA directory exists
+  ansible.builtin.file:
+    path: /etc/ssh/ca
+    state: directory
+    owner: root
+    group: root
+    mode: "0755"
+
+- name: Install SSH user CA public key
+  ansible.builtin.copy:
+    src: "{{ ssh_ca_pubkey_path }}"
+    dest: /etc/ssh/ca/ca_user.pub
+    owner: root
+    group: root
+    mode: "0644"
+  notify: Restart sshd
+
+- name: Configure SSH certificate trust
+  ansible.builtin.copy:
+    dest: /etc/ssh/sshd_config.d/20-ssh-ca.conf
+    owner: root
+    group: root
+    mode: "0644"
+    content: |
+      TrustedUserCAKeys /etc/ssh/ca/ca_user.pub
+      AuthorizedPrincipalsFile /etc/ssh/auth_principals/%u
+  notify: Restart sshd
+
+- name: Ensure auth_principals directory exists
+  ansible.builtin.file:
+    path: /etc/ssh/auth_principals
+    state: directory
+    owner: root
+    group: root
+    mode: "0755"
+
+- name: Resolve principals for this host
+  ansible.builtin.set_fact:
+    ssh_ca_host_principals: >-
+      {{
+        (ssh_principals[inventory_hostname].users
+         if ssh_principals is defined
+            and inventory_hostname in ssh_principals
+         else {})
+      }}
+
+- name: Deploy auth_principals files per user
+  ansible.builtin.copy:
+    dest: "/etc/ssh/auth_principals/{{ item.key }}"
+    owner: root
+    group: root
+    mode: "0644"
+    content: "{{ item.value | join('\n') }}\n"
+  loop: "{{ ssh_ca_host_principals | dict2items }}"
+  when: ssh_ca_host_principals | length > 0
+  notify: Restart sshd
+
+- name: Warn when no principals configured for host
+  ansible.builtin.debug:
+    msg: >-
+      No principals in ssh_principals.yaml for {{ inventory_hostname }} —
+      CA trust installed; add users under hosts.<name>.users to enable cert login.
+  when: ssh_ca_host_principals | length == 0