diff --git a/ansible/playbooks/day1_deploy_honcho.yml b/ansible/playbooks/day1_deploy_honcho.yml
index 059c608..3768199 100644
--- a/ansible/playbooks/day1_deploy_honcho.yml
+++ b/ansible/playbooks/day1_deploy_honcho.yml
@@ -5,6 +5,9 @@
 # Deploys Honcho + pgvector PostgreSQL on the `lincoln` host. Run AFTER
 # day0_linux_baseline.yml has been applied to the target.
 #
+# expand_root_lv runs first to reclaim any unallocated space left by the
+# Ubuntu autoinstall template (half-disk LV pattern).
+#
 # Usage:
 #   ansible-playbook -i inventory.yml playbooks/day1_deploy_honcho.yml
 # ============================================================================
@@ -14,4 +17,5 @@
   become: true
   gather_facts: true
   roles:
+    - expand_root_lv
     - honcho
diff --git a/ansible/roles/expand_root_lv/README.md b/ansible/roles/expand_root_lv/README.md
new file mode 100644
index 0000000..284ea6f
--- /dev/null
+++ b/ansible/roles/expand_root_lv/README.md
@@ -0,0 +1,63 @@
+# expand-root-lv role
+
+Idempotent role that extends the root LVM logical volume to fill its
+volume group and grows the underlying filesystem (ext4 or xfs).
+
+## Why this role exists
+
+The Ubuntu Server autoinstall template (used by the mk-labs `wed`-baked
+VM templates) provisions the root LV at roughly half the available disk
+size — a longstanding installer default that surprises everyone who
+hasn't been bitten by it before. Every freshly-provisioned VM in mk-labs
+needs this fix-up before it's fully useful.
+
+## Idempotency
+
+- If `vg_free_count == 0`, the `lvextend` step is skipped and the
+  filesystem-grow step is also skipped (nothing to resize against).
+- If the target volume group doesn't exist on the host (e.g. a non-LVM
+  layout), the role exits cleanly via `meta: end_play`.
+- Safe to leave in a day1 deploy playbook so future disk expansions
+  (Proxmox-side disk grow → reboot → run role) are picked up
+  automatically.
+
+## Usage
+
+Standalone:
+
+```yaml
+- hosts: lincoln
+  become: true
+  roles:
+    - expand_root_lv
+```
+
+Or chained ahead of an application role in a day1 playbook:
+
+```yaml
+- hosts: honcho_server
+  become: true
+  roles:
+    - expand_root_lv
+    - honcho
+```
+
+## Defaults
+
+| Variable                          | Default       | Purpose                                           |
+|-----------------------------------|---------------|---------------------------------------------------|
+| `expand_root_lv_vg_name`          | `ubuntu-vg`   | LVM volume group name (Ubuntu installer default). |
+| `expand_root_lv_lv_name`          | `ubuntu-lv`   | LVM logical volume name (Ubuntu installer default). |
+| `expand_root_lv_mountpoint`       | `/`           | Mountpoint of the filesystem to grow.             |
+
+Override these in `host_vars/<host>.yml` for hosts that use a different
+LVM layout. Hosts without LVM are silently no-op'd.
+
+## Limitations
+
+- Does not extend the underlying partition. If the operator grows the
+  Proxmox disk and the partition itself needs to grow before lvextend
+  can claim the new space, run `growpart /dev/sda 3` (or equivalent)
+  first. A future enhancement could automate this via `cloud-utils`'
+  `growpart` package, but it's out of scope for the initial template
+  fix-up case where the partition already covers the whole disk.
diff --git a/ansible/roles/expand_root_lv/defaults/main.yml b/ansible/roles/expand_root_lv/defaults/main.yml
new file mode 100644
index 0000000..222a91d
--- /dev/null
+++ b/ansible/roles/expand_root_lv/defaults/main.yml
@@ -0,0 +1,26 @@
+---
+# ============================================================================
+# expand-root-lv role defaults
+# ============================================================================
+# Extends the root LVM logical volume to fill its volume group, then grows
+# the underlying filesystem to match. Idempotent: when there's no free PE
+# in the VG (i.e. the LV already fills the VG), the lvextend step is a
+# no-op and resize2fs/xfs_growfs simply confirms the filesystem is at
+# capacity.
+#
+# Designed for Ubuntu cloud-image-style installations where the autoinstall
+# template provisions an LV at half the disk size (the Ubuntu Server
+# installer's longstanding default). Run once after VM provisioning to
+# reclaim the unallocated PE; safe to leave in a day1 playbook so future
+# disk expansions are picked up automatically.
+# ============================================================================
+
+# The LV and VG names follow the Ubuntu Server installer's convention.
+# Override per-host if your template differs.
+expand_root_lv_vg_name: ubuntu-vg
+expand_root_lv_lv_name: ubuntu-lv
+
+# Mount point we expect to be backed by the target LV. Used purely for
+# the resize2fs / xfs_growfs decision — the role inspects this path's
+# filesystem type and dispatches to the correct grow command.
+expand_root_lv_mountpoint: /
diff --git a/ansible/roles/expand_root_lv/meta/main.yml b/ansible/roles/expand_root_lv/meta/main.yml
new file mode 100644
index 0000000..e425d7b
--- /dev/null
+++ b/ansible/roles/expand_root_lv/meta/main.yml
@@ -0,0 +1,23 @@
+---
+galaxy_info:
+  role_name: expand_root_lv
+  author: JARVIS
+  description: >-
+    Idempotent role that extends the root LVM logical volume to fill its
+    volume group and grows the underlying filesystem (ext4 or xfs). Fixes
+    the half-disk LV that the Ubuntu Server autoinstall template ships
+    with by default.
+  license: MIT
+  min_ansible_version: "2.14"
+  platforms:
+    - name: Ubuntu
+      versions:
+        - noble
+        - jammy
+  galaxy_tags:
+    - lvm
+    - cloud-init
+    - homelab
+    - storage
+
+dependencies: []
diff --git a/ansible/roles/expand_root_lv/tasks/main.yml b/ansible/roles/expand_root_lv/tasks/main.yml
new file mode 100644
index 0000000..65d5858
--- /dev/null
+++ b/ansible/roles/expand_root_lv/tasks/main.yml
@@ -0,0 +1,70 @@
+---
+# ============================================================================
+# expand-root-lv / main
+# ----------------------------------------------------------------------------
+# 1. Confirm the target VG exists (skip role cleanly on non-LVM hosts).
+# 2. Read free physical-extent count for the VG.
+# 3. Extend the LV to +100%FREE only when free_pe > 0.
+# 4. Grow the filesystem on the mountpoint (ext4 -> resize2fs, xfs -> xfs_growfs).
+# Each step is idempotent and skips when there's nothing to do.
+# ============================================================================
+
+- name: Gather LVM facts
+  ansible.builtin.command:
+    cmd: "vgs --noheadings --nosuffix --units b -o vg_name,vg_free_count {{ expand_root_lv_vg_name }}"
+  register: vg_info
+  changed_when: false
+  failed_when: false
+
+- name: Skip role when target VG is absent
+  ansible.builtin.meta: end_play
+  when: vg_info.rc != 0
+
+- name: Parse free PE count
+  ansible.builtin.set_fact:
+    expand_root_lv_free_pe: "{{ (vg_info.stdout.split() | last | int) if vg_info.stdout | length > 0 else 0 }}"
+
+- name: Extend LV to fill VG (only if free PE > 0)
+  ansible.builtin.command:
+    cmd: "lvextend -l +100%FREE /dev/{{ expand_root_lv_vg_name }}/{{ expand_root_lv_lv_name }}"
+  register: lvextend_result
+  when: expand_root_lv_free_pe | int > 0
+  changed_when: lvextend_result.rc == 0
+
+- name: Detect filesystem type at mountpoint
+  ansible.builtin.command:
+    cmd: "findmnt {{ expand_root_lv_mountpoint }} -no FSTYPE"
+  register: fstype_result
+  changed_when: false
+
+- name: Set filesystem type fact
+  ansible.builtin.set_fact:
+    expand_root_lv_fstype: "{{ fstype_result.stdout | trim }}"
+
+- name: Grow ext4 filesystem
+  ansible.builtin.command:
+    cmd: "resize2fs /dev/{{ expand_root_lv_vg_name }}/{{ expand_root_lv_lv_name }}"
+  register: resize_result
+  when:
+    - expand_root_lv_fstype == "ext4"
+    - lvextend_result.changed | default(false)
+  changed_when: resize_result.rc == 0
+
+- name: Grow xfs filesystem
+  ansible.builtin.command:
+    cmd: "xfs_growfs {{ expand_root_lv_mountpoint }}"
+  register: xfs_result
+  when:
+    - expand_root_lv_fstype == "xfs"
+    - lvextend_result.changed | default(false)
+  changed_when: xfs_result.rc == 0
+
+- name: Report current root size
+  ansible.builtin.command:
+    cmd: "df -h {{ expand_root_lv_mountpoint }}"
+  register: df_result
+  changed_when: false
+
+- name: Show post-resize disk usage
+  ansible.builtin.debug:
+    msg: "{{ df_result.stdout_lines }}"