diff --git a/.gitignore b/.gitignore
index ad80b11..1106bb2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,5 @@
 .vscode/
+.opencode/
 
 config.pkl
 
diff --git a/.mise.toml b/.mise.toml
index f1b9820..12465d1 100644
--- a/.mise.toml
+++ b/.mise.toml
@@ -29,6 +29,11 @@ description = "Render tfvars and show what would change"
 dir = "{{ config_root }}/ansible"
 run = "ansible-playbook deploy.yml --tags=render,init,plan"
 
+[tasks.undeploy-mobile]
+description = "Tear down constructor-mobile Terraform resources"
+dir = "{{ config_root }}/ansible"
+run = "ansible-playbook undeploy-mobile.yml"
+
 [settings]
 lockfile = true
 experimental = true
diff --git a/ansible/deploy.yml b/ansible/deploy.yml
index 403d81e..4745ece 100644
--- a/ansible/deploy.yml
+++ b/ansible/deploy.yml
@@ -20,12 +20,14 @@
       loop_control:
         loop_var: project
         label: "{{ project.name }}"
+      when: project.name != mobile_project or (mobile_enabled | bool)
       tags: [sync, upstream]
 
     - import_tasks: tasks/03-bootstrap-ba.yml
       tags: [bootstrap, build, ba]
 
     - import_tasks: tasks/03b-bootstrap-mobile.yml
+      when: mobile_enabled | bool
       tags: [bootstrap, build, mobile]
 
     # background-agents must be initialized/applied before constructor-mobile.
@@ -43,10 +45,13 @@
     # constructor-mobile consumes the BA control-plane URL, so keep all mobile
     # Terraform work after BA readiness is verified.
     - import_tasks: tasks/06-capture-ba-outputs.yml
+      when: mobile_enabled | bool
       tags: [mobile, capture, terraform]
 
     - import_tasks: tasks/06a-terraform-init-mobile.yml
+      when: mobile_enabled | bool
       tags: [mobile, init, terraform]
 
     - import_tasks: tasks/06b-terraform-apply-mobile.yml
+      when: mobile_enabled | bool
       tags: [mobile, apply]
diff --git a/ansible/group_vars/all.yml b/ansible/group_vars/all.yml
index c7131c7..d229aef 100644
--- a/ansible/group_vars/all.yml
+++ b/ansible/group_vars/all.yml
@@ -9,6 +9,7 @@ config_render_root: "{{ config_root }}/render"
 deploy_dir: "{{ repo_root }}/deploy"
 inputs_json: "{{ deploy_dir }}/inputs.json"
 mobile_inputs_json: "{{ deploy_dir }}/mobile-inputs.json"
+mobile_enabled: false
 state_json: "{{ deploy_dir }}/state.json"
 projects_json: "{{ deploy_dir }}/projects.json"
 
diff --git a/ansible/tasks/01-render-config.yml b/ansible/tasks/01-render-config.yml
index b7d02be..d66fdce 100644
--- a/ansible/tasks/01-render-config.yml
+++ b/ansible/tasks/01-render-config.yml
@@ -19,3 +19,11 @@
   loop_control:
     label: "{{ item.dst | basename }}"
   changed_when: true
+
+- name: Load rendered mobile settings
+  ansible.builtin.set_fact:
+    mobile_config: "{{ lookup('file', mobile_inputs_json) | from_json }}"
+
+- name: Set mobile provisioning flag
+  ansible.builtin.set_fact:
+    mobile_enabled: "{{ mobile_config.enabled | default(false) | bool }}"
diff --git a/ansible/tasks/04-terraform-init-stack.yml b/ansible/tasks/04-terraform-init-stack.yml
index 277e008..eadc0c0 100644
--- a/ansible/tasks/04-terraform-init-stack.yml
+++ b/ansible/tasks/04-terraform-init-stack.yml
@@ -9,7 +9,7 @@
     dest: "{{ terraform_stack_tf_dir }}/{{ terraform_var_file }}"
     mode: "0600"
     content: |
-      {% for key, value in (terraform_inputs | combine(terraform_stack_extra_tfvars | default({}))).items() %}
+      {% for key, value in (terraform_inputs | dict2items | rejectattr('key', 'equalto', 'enabled') | items2dict | combine(terraform_stack_extra_tfvars | default({}))).items() %}
       {% if value is string and '\n' in value %}
       {{ key }} = <<-EOF
       {{ value }}
diff --git a/ansible/tasks/06-capture-ba-outputs.yml b/ansible/tasks/06-capture-ba-outputs.yml
index 9076b53..f4f111d 100644
--- a/ansible/tasks/06-capture-ba-outputs.yml
+++ b/ansible/tasks/06-capture-ba-outputs.yml
@@ -1,8 +1,6 @@
 ---
-- name: Load b-a inputs (for deterministic URL construction)
-  ansible.builtin.set_fact:
-    ba_inputs: "{{ lookup('file', inputs_json) | from_json }}"
-    tf_state: "{{ lookup('file', state_json) | from_json }}"
+- name: Compute b-a URLs
+  ansible.builtin.import_tasks: 06-compute-ba-urls.yml
 
 - name: Verify background-agents has been deployed
   ansible.builtin.command:
@@ -19,15 +17,6 @@
     'cloudflare_worker' not in ba_state_list.stdout or
     'cloudflare_workers_deployment' not in ba_state_list.stdout
 
-- name: Compute b-a control plane host
-  ansible.builtin.set_fact:
-    ba_control_plane_host: "open-inspect-control-plane-{{ ba_inputs.deployment_name }}.{{ ba_inputs.cloudflare_worker_subdomain }}.workers.dev"
-
-- name: Derive b-a URLs from host
-  ansible.builtin.set_fact:
-    ba_control_plane_url: "https://{{ ba_control_plane_host }}"
-    ba_ws_url: "wss://{{ ba_control_plane_host }}"
-
 - name: Confirm captured values
   ansible.builtin.debug:
     msg:
diff --git a/ansible/tasks/06-compute-ba-urls.yml b/ansible/tasks/06-compute-ba-urls.yml
new file mode 100644
index 0000000..09b24e2
--- /dev/null
+++ b/ansible/tasks/06-compute-ba-urls.yml
@@ -0,0 +1,14 @@
+---
+- name: Load b-a inputs and state
+  ansible.builtin.set_fact:
+    ba_inputs: "{{ lookup('file', inputs_json) | from_json }}"
+    tf_state: "{{ lookup('file', state_json) | from_json }}"
+
+- name: Compute b-a control plane host
+  ansible.builtin.set_fact:
+    ba_control_plane_host: "open-inspect-control-plane-{{ ba_inputs.deployment_name }}.{{ ba_inputs.cloudflare_worker_subdomain }}.workers.dev"
+
+- name: Derive b-a URLs from host
+  ansible.builtin.set_fact:
+    ba_control_plane_url: "https://{{ ba_control_plane_host }}"
+    ba_ws_url: "wss://{{ ba_control_plane_host }}"
diff --git a/ansible/tasks/07-terraform-destroy-mobile.yml b/ansible/tasks/07-terraform-destroy-mobile.yml
new file mode 100644
index 0000000..c9786df
--- /dev/null
+++ b/ansible/tasks/07-terraform-destroy-mobile.yml
@@ -0,0 +1,19 @@
+---
+- name: Define mobile terraform environment
+  ansible.builtin.set_fact:
+    mobile_tf_env:
+      AWS_ACCESS_KEY_ID: "{{ tf_state.access_key }}"
+      AWS_SECRET_ACCESS_KEY: "{{ tf_state.secret_key }}"
+      AWS_REGION: "{{ tf_state.region }}"
+
+- name: Terraform destroy (mobile)
+  ansible.builtin.command:
+    cmd: "terraform destroy {{ terraform_apply_args }}"
+    chdir: "{{ mobile_tf_dir }}"
+  environment: "{{ mobile_tf_env }}"
+  register: mobile_destroy
+  changed_when: "'Destroy complete' in mobile_destroy.stdout"
+
+- name: Destroy summary
+  ansible.builtin.debug:
+    msg: "constructor-mobile teardown finished"
diff --git a/ansible/undeploy-mobile.yml b/ansible/undeploy-mobile.yml
new file mode 100644
index 0000000..26d0823
--- /dev/null
+++ b/ansible/undeploy-mobile.yml
@@ -0,0 +1,32 @@
+---
+- name: Undeploy constructor-mobile stack
+  hosts: local
+  connection: local
+  gather_facts: false
+
+  tasks:
+    - import_tasks: tasks/00-preflight.yml
+      tags: [preflight]
+
+    - import_tasks: tasks/01-render-config.yml
+      tags: [render, config]
+
+    - name: Sync constructor-mobile project
+      ansible.builtin.include_tasks:
+        file: tasks/02-sync-upstream.yml
+        apply:
+          tags: [sync, upstream, mobile]
+      loop: "{{ projects | selectattr('name', 'equalto', mobile_project) }}"
+      loop_control:
+        loop_var: project
+        label: "{{ project.name }}"
+      tags: [sync, upstream, mobile]
+
+    - import_tasks: tasks/06-compute-ba-urls.yml
+      tags: [mobile, terraform]
+
+    - import_tasks: tasks/06a-terraform-init-mobile.yml
+      tags: [mobile, init, terraform]
+
+    - import_tasks: tasks/07-terraform-destroy-mobile.yml
+      tags: [mobile, destroy]
diff --git a/config.example.pkl b/config.example.pkl
index db35dee..8294f6a 100644
--- a/config.example.pkl
+++ b/config.example.pkl
@@ -126,12 +126,16 @@ deployment {
 }
 
 mobile {
+  // Set true to provision constructor-mobile during `mise run deploy`.
+  enabled = false
+
   // Defaults are fine; uncomment to customize
   // nameSuffix = "prod"
   // customDomain = "gateway.example.com"
   // pushCron = new Listing { "*/2 * * * *" }
 
-  appJwtSigningKey = "REPLACE_ME_base64_from_openssl_rand_base64_32" // openssl rand -base64 32
+  // Required only when enabled = true.
+  // appJwtSigningKey = "REPLACE_ME_base64_from_openssl_rand_base64_32" // openssl rand -base64 32
 }
 
 // ─── Optional per-project overrides ───────────────────────────────────
diff --git a/config/render/mobile-inputs.pkl b/config/render/mobile-inputs.pkl
index c23679c..50b404d 100644
--- a/config/render/mobile-inputs.pkl
+++ b/config/render/mobile-inputs.pkl
@@ -13,7 +13,11 @@ import "../../config.pkl" as c
 local m = c.mobile
 local d = c.deployment
 
+local defaultAppJwtSigningKey = "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA="
+
 local baseFields = new Mapping {
+  ["enabled"] = m.enabled
+
   // Cloudflare (reused from b-a's config)
   ["cloudflare_account_id"] = d.cloudflare.accountId
   ["cloudflare_api_token"]  = d.cloudflare.apiToken
@@ -30,7 +34,7 @@ local baseFields = new Mapping {
   ["github_oauth_client_secret"] = d.github.app.clientSecret
 
   // Mobile-only secret
-  ["app_jwt_signing_key"] = m.appJwtSigningKey
+  ["app_jwt_signing_key"] = if (m.appJwtSigningKey != null) m.appJwtSigningKey else defaultAppJwtSigningKey
 
   // Shared secret: must match b-a's value
   ["internal_callback_secret"] = d.security.internalCallbackSecret
diff --git a/config/schema/Root.pkl b/config/schema/Root.pkl
index 2e67619..442185b 100644
--- a/config/schema/Root.pkl
+++ b/config/schema/Root.pkl
@@ -9,7 +9,7 @@ import "../defaults/projects.pkl" as ProjectDefaults
 projects: Mapping<String, Project.Project> = ProjectDefaults.projects
 
 deployment: Deployment.Deployment
-mobile: Mobile.Mobile
+mobile: Mobile.Mobile = new {}
 state: State.State
 
 local sandboxError: String? =
@@ -43,6 +43,11 @@ local githubBotError: String? =
     "github.bot is enabled but webhookSecret or username is missing"
   else null
 
+local mobileError: String? =
+  if (mobile.enabled && mobile.appJwtSigningKey == null)
+    "mobile is enabled but appJwtSigningKey is missing"
+  else null
+
 hidden unsupportedTweakcnThemeProjects: Listing<String> = new Listing {
   for (key, value in projects.toMap()) {
     when (key != "background-agents" && value.tweakcnThemeUrl != null) {
@@ -63,6 +68,7 @@ hidden _errors: List<String?> = List(
   webError,
   accessControlError,
   githubBotError,
+  mobileError,
   tweakcnThemeError
 )
 
diff --git a/config/schema/mobile/Mobile.pkl b/config/schema/mobile/Mobile.pkl
index 40c0dc4..c48b294 100644
--- a/config/schema/mobile/Mobile.pkl
+++ b/config/schema/mobile/Mobile.pkl
@@ -6,6 +6,9 @@ typealias Base64_32 = String(
 )
 
 class Mobile {
+  /// Set true to provision constructor-mobile during deploy.
+  enabled: Boolean = false
+
   /// Suffix for resource names (e.g. "prod", "staging")
   nameSuffix: String(length > 0) = "prod"
 
@@ -23,5 +26,5 @@ class Mobile {
 
   /// Gateway-owned key used to sign short-lived app-session JWTs.
   /// Generate: openssl rand -base64 32
-  appJwtSigningKey: Base64_32
+  appJwtSigningKey: Base64_32? = null
 }