diff --git a/ansible/roles/anvil/handlers/main.yml b/ansible/roles/anvil/handlers/main.yml
index 805b137..03acc37 100644
--- a/ansible/roles/anvil/handlers/main.yml
+++ b/ansible/roles/anvil/handlers/main.yml
@@ -7,3 +7,6 @@
   ansible.builtin.systemd:
     name: anvil
     state: restarted
+  # Under --check on a fresh host the unit isn't installed yet; flush_handlers would
+  # otherwise fail trying to restart a non-existent service.
+  when: not ansible_check_mode or 'anvil.service' in (ansible_facts.services | default({}))
diff --git a/ansible/roles/anvil/tasks/main.yml b/ansible/roles/anvil/tasks/main.yml
index 5c201ab..2edbacd 100644
--- a/ansible/roles/anvil/tasks/main.yml
+++ b/ansible/roles/anvil/tasks/main.yml
@@ -15,6 +15,23 @@
     create_home: true
     shell: /usr/sbin/nologin
 
+# Under --check the user/apt/Foundry tasks below are no-ops, so on a fresh host the
+# anvil user and Foundry binaries don't exist yet — become_user, cast, and the
+# systemd unit would all hard-fail. Probe real on-host state (read-only, runs in
+# check mode) so those tasks skip in check mode while still previewing drift on an
+# already-provisioned host.
+- name: Probe whether the anvil user already exists on the target
+  ansible.builtin.getent:
+    database: passwd
+    key: "{{ anvil_user }}"
+    fail_key: false
+
+# Service guards below reuse baseline's service_facts; gather here too so the role
+# stays correct when run standalone (e.g. --tags anvil) without baseline first.
+- name: Probe service facts if not already gathered
+  ansible.builtin.service_facts:
+  when: ansible_facts.services is not defined
+
 - name: Install Foundry bootstrap prerequisites
   ansible.builtin.apt:
     name: [curl, git, jq, ca-certificates]
@@ -52,7 +69,11 @@
     executable: /bin/bash
   environment:
     FOUNDRY_DIR: "{{ foundry_dir }}"
-  when: not anvil_bin.stat.exists
+  when:
+    - not anvil_bin.stat.exists
+    # become_user requires the anvil user to exist; --check didn't create it.
+    # fail_key:false stores a missing user as {user: None}, so test the value.
+    - not ansible_check_mode or (getent_passwd | default({})).get(anvil_user)
 
 - name: Ensure /etc/anvil exists
   ansible.builtin.file:
@@ -69,7 +90,10 @@
   register: anvil_env_stat
 
 - name: Generate and install the shared mnemonic
-  when: not anvil_env_stat.stat.exists
+  when:
+    - not anvil_env_stat.stat.exists
+    # cast lives in the Foundry bin; under --check on a fresh host it isn't installed.
+    - not ansible_check_mode or anvil_bin.stat.exists
   block:
     - name: Generate a fresh mnemonic with cast
       ansible.builtin.command:
@@ -135,6 +159,7 @@
     name: anvil
     enabled: true
     state: started
+  when: not ansible_check_mode or 'anvil.service' in (ansible_facts.services | default({}))
 
 - name: Wait for the anvil RPC to answer on loopback
   ansible.builtin.uri:
@@ -155,3 +180,7 @@
     # Assert it's OUR chain, not a stale process on the port answering 200.
     - (anvil_rpc_probe.json.result | default('0x0')) | int(0, 16) == anvil_chain_id
   changed_when: false
+  # Skip entirely in check mode: --check never (re)starts anvil, so this liveness
+  # probe would falsely fail against a stopped-but-provisioned host. It previews no
+  # drift (changed_when:false) — there is nothing to verify in a dry run.
+  when: not ansible_check_mode
diff --git a/ansible/roles/baseline/handlers/main.yml b/ansible/roles/baseline/handlers/main.yml
index 9031d3d..50374a6 100644
--- a/ansible/roles/baseline/handlers/main.yml
+++ b/ansible/roles/baseline/handlers/main.yml
@@ -1,10 +1,16 @@
 ---
+# Both units come from baseline_packages, a no-op under --check, so on a fresh host
+# the unit may not exist when a flush (e.g. anvil's flush_handlers) fires the handler.
+# Guard on real on-host state (service_facts, gathered in tasks/main.yml): run on a
+# provisioned host (drift preview), skip a missing unit in check mode.
 - name: Reload nftables
   ansible.builtin.systemd:
     name: nftables
     state: restarted
+  when: not ansible_check_mode or 'nftables.service' in (ansible_facts.services | default({}))
 
 - name: Restart fail2ban
   ansible.builtin.systemd:
     name: fail2ban
     state: restarted
+  when: not ansible_check_mode or 'fail2ban.service' in (ansible_facts.services | default({}))
diff --git a/ansible/roles/baseline/tasks/main.yml b/ansible/roles/baseline/tasks/main.yml
index 2af4d8e..a1b6386 100644
--- a/ansible/roles/baseline/tasks/main.yml
+++ b/ansible/roles/baseline/tasks/main.yml
@@ -9,6 +9,14 @@
     update_cache: true
     cache_valid_time: 3600
 
+# Under --check the install above is a no-op, so packaged units (fail2ban, chrony,
+# nftables) may not exist yet on a fresh host and a systemd enable/start would
+# hard-fail ("Could not find the requested service"). Probe real on-host state
+# (read-only, runs in check mode) so the service tasks below can skip a missing
+# unit in check mode while still previewing drift on an already-provisioned host.
+- name: Probe which service units already exist on the target
+  ansible.builtin.service_facts:
+
 # --- Admin account (must exist + have a key BEFORE ssh_hardening locks root) ---
 # Resolve the user and key set from the control machine when left empty; explicit
 # values always win. Lookups run on the control node — that's the operator's box.
@@ -87,12 +95,27 @@
     shell: /bin/bash
     create_home: true
 
+# authorized_key resolves the user's ~/.ssh to write the key, so the account must
+# already exist. Under --check the create task above is a no-op, so on a not-yet-
+# provisioned host the user is absent and the module hard-fails ("Either user must
+# exist or you must provide full path to key file in check mode"). Probe real
+# on-host state (read-only, runs in check mode) and skip the key install only when
+# check mode meets a missing user; real runs and check runs on a provisioned host
+# (where drift is worth previewing) always proceed.
+- name: Probe whether the admin user already exists on the target
+  ansible.builtin.getent:
+    database: passwd
+    key: "{{ ssh_admin_user_effective }}"
+    fail_key: false
+
 - name: Install admin authorized keys
   ansible.posix.authorized_key:
     user: "{{ ssh_admin_user_effective }}"
     key: "{{ item }}"
     state: present
   loop: "{{ ssh_admin_keys }}"
+  # fail_key:false stores a missing user as {user: None}, so test the value, not `in`.
+  when: not ansible_check_mode or (getent_passwd | default({})).get(ssh_admin_user_effective)
 
 # --- Firewall: default-deny inbound, SSH only ---------------------------------
 - name: Install nftables ruleset
@@ -110,6 +133,7 @@
     name: nftables
     enabled: true
     state: started
+  when: not ansible_check_mode or 'nftables.service' in (ansible_facts.services | default({}))
 
 # --- Automatic security patches ----------------------------------------------
 - name: Enable unattended-upgrades
@@ -140,6 +164,7 @@
     name: fail2ban
     enabled: true
     state: started
+  when: not ansible_check_mode or 'fail2ban.service' in (ansible_facts.services | default({}))
 
 # --- Time sync ----------------------------------------------------------------
 - name: Enable and start chrony
@@ -147,6 +172,7 @@
     name: chrony
     enabled: true
     state: started
+  when: not ansible_check_mode or 'chrony.service' in (ansible_facts.services | default({}))
 
 # --- DevSec hardening (LAST: ssh_hardening disables root + password auth) ------
 - name: Apply DevSec OS hardening
diff --git a/ansible/roles/caddy/handlers/main.yml b/ansible/roles/caddy/handlers/main.yml
index 6d9afe1..873f60b 100644
--- a/ansible/roles/caddy/handlers/main.yml
+++ b/ansible/roles/caddy/handlers/main.yml
@@ -5,3 +5,6 @@
   ansible.builtin.systemd:
     name: caddy
     state: restarted
+  # Under --check on a fresh host the unit isn't installed yet; flush_handlers would
+  # otherwise fail trying to restart a non-existent service.
+  when: not ansible_check_mode or 'caddy.service' in (ansible_facts.services | default({}))
diff --git a/ansible/roles/caddy/tasks/add_user.yml b/ansible/roles/caddy/tasks/add_user.yml
index 57902b9..5421d22 100644
--- a/ansible/roles/caddy/tasks/add_user.yml
+++ b/ansible/roles/caddy/tasks/add_user.yml
@@ -20,7 +20,14 @@
   failed_when: false
 
 - name: Mint '{{ caddy_target_user }}'
-  when: caddy_user_check.rc != 0
+  # Never mint in check mode: minting needs the caddy binary (hash-password, which
+  # auto-skips under --check), writes the TSV, and reveals a password — all mutating
+  # side effects a dry run must not perform. Gating on ansible_check_mode first also
+  # means caddy_user_check.rc — undefined when the existence-check command auto-skips
+  # under --check — is never the deciding factor; default it so it can't error.
+  when:
+    - not ansible_check_mode
+    - caddy_user_check.rc | default(1) != 0
   block:
     - name: Generate a random password
       ansible.builtin.set_fact:
diff --git a/ansible/roles/caddy/tasks/main.yml b/ansible/roles/caddy/tasks/main.yml
index 7d2b952..b00429f 100644
--- a/ansible/roles/caddy/tasks/main.yml
+++ b/ansible/roles/caddy/tasks/main.yml
@@ -25,11 +25,28 @@
 
 # Rebuild the Caddyfile import block from the TSV registry. Idempotent: identical
 # registry -> identical content -> no change -> no restart.
+# Under --check the user-mint tasks don't write (the existence probe is a command
+# that auto-skips; the lineinfile registry write is a no-op), so on a fresh host the
+# TSV registry is never created and the slurp below would fail (file not found).
+# Probe for it (read-only, runs in check mode); the slurp/render skip in check mode
+# when it's absent, but still preview drift on an already-provisioned host.
+- name: Check whether the basic-auth registry exists
+  ansible.builtin.stat:
+    path: "{{ caddy_users_tsv }}"
+  register: caddy_tsv_stat
+
+# Service guards below reuse baseline's service_facts; gather here too so the role
+# stays correct when run standalone (e.g. --tags caddy) without baseline first.
+- name: Probe service facts if not already gathered
+  ansible.builtin.service_facts:
+  when: ansible_facts.services is not defined
+
 - name: Read the basic-auth user registry
   ansible.builtin.slurp:
     src: "{{ caddy_users_tsv }}"
   register: caddy_tsv_raw
   no_log: true
+  when: not ansible_check_mode or caddy_tsv_stat.stat.exists
 
 - name: Render the basic_auth import file from the registry
   ansible.builtin.copy:
@@ -49,6 +66,8 @@
       }
   no_log: true
   notify: Restart caddy
+  # caddy_tsv_raw is only defined when the slurp above ran (skipped in check mode).
+  when: not ansible_check_mode or caddy_tsv_stat.stat.exists
 
 - name: Install the Caddyfile
   ansible.builtin.template:
@@ -59,12 +78,15 @@
     mode: "0644"
     validate: "caddy validate --adapter caddyfile --config %s"
   notify: Restart caddy
+  # validate shells out to the caddy binary, absent under --check on a fresh host.
+  when: not ansible_check_mode or 'caddy.service' in (ansible_facts.services | default({}))
 
 - name: Enable and start caddy
   ansible.builtin.systemd:
     name: caddy
     enabled: true
     state: started
+  when: not ansible_check_mode or 'caddy.service' in (ansible_facts.services | default({}))
 
 - name: Apply caddy config changes now
   ansible.builtin.meta: flush_handlers