diff --git a/README.md b/README.md
index e674be3..add9590 100644
--- a/README.md
+++ b/README.md
@@ -4,8 +4,8 @@ Installs the [Seriatim](https://gitea.maximumdirect.net/eric/seriatim)
 transcript processor from source. The role supports Ubuntu 26.04 on `amd64`
 and `arm64` hosts and is independently usable outside the D&D pipeline role.
 
-The role manages its build dependencies and a root-owned source checkout. At
-this point binary installation is added by subsequent implementation work.
+The role manages its build dependencies and a root-owned source checkout,
+builds a native static executable, validates it, and safely installs it.
 
 ## Requirements
 
@@ -49,6 +49,29 @@ provided independently through the managed host's Git configuration or SSH
 environment; this role does not manage credentials or accept unknown host
 keys.
 
+## Build and installation behavior
+
+Builds run from the selected checkout with `GOWORK=off`,
+`GOTOOLCHAIN=local`, `CGO_ENABLED=0`, the configured ordered build flags, and
+the upstream version-injection linker flags. The resulting executable is
+staged and must report the exact configured version before it atomically
+replaces `seriatim_binary_path`. It is installed as `root:root` mode `0755`.
+
+The role records readable inputs, their SHA-256 fingerprint, and the installed
+binary checksum beneath `seriatim_build_state_dir`. A source commit, compiler
+identity, Go path, version, flags, linker flags, package, or fixed environment
+change triggers a rebuild. Missing or corrupt state, a modified binary, or an
+incorrect installed version also triggers rebuilding. Failed compilation or
+staged validation leaves the previous installed binary and successful state
+untouched.
+
+For example, development from a branch must identify both source and output:
+
+```yaml
+seriatim_source_ref: feature/example
+seriatim_build_version: v1.5.0-dev
+```
+
 ## Static validation
 
 ```sh
diff --git a/tasks/build.yml b/tasks/build.yml
new file mode 100644
index 0000000..289976e
--- /dev/null
+++ b/tasks/build.yml
@@ -0,0 +1,189 @@
+---
+- name: Construct canonical Seriatim build inputs
+  ansible.builtin.set_fact:
+    seriatim_build_inputs: >-
+      {{ {
+           'source_commit': seriatim_source_commit,
+           'go_version': seriatim_go_version_result.stdout,
+           'go_binary': seriatim_go_binary,
+           'build_version': seriatim_build_version,
+           'build_flags': seriatim_go_build_flags,
+           'ldflags': seriatim_go_ldflags,
+           'package': seriatim_go_package,
+           'environment': {
+             'GOWORK': 'off',
+             'GOTOOLCHAIN': 'local',
+             'CGO_ENABLED': '0'
+           }
+         } | to_nice_json(indent=2, sort_keys=true) }}
+
+- name: Calculate desired Seriatim build fingerprint
+  ansible.builtin.set_fact:
+    seriatim_desired_fingerprint: "{{ seriatim_build_inputs | hash('sha256') }}"
+    seriatim_stored_fingerprint: ""
+    seriatim_stored_checksum: ""
+
+- name: Inspect installed Seriatim binary
+  ansible.builtin.stat:
+    path: "{{ seriatim_binary_path }}"
+    checksum_algorithm: sha256
+  register: seriatim_installed_binary_stat
+
+- name: Inspect Seriatim build input state
+  ansible.builtin.stat:
+    path: "{{ seriatim_build_state_dir }}/build-inputs.json"
+  register: seriatim_build_inputs_state_stat
+
+- name: Inspect Seriatim fingerprint state
+  ansible.builtin.stat:
+    path: "{{ seriatim_build_state_dir }}/fingerprint.sha256"
+  register: seriatim_fingerprint_state_stat
+
+- name: Inspect Seriatim checksum state
+  ansible.builtin.stat:
+    path: "{{ seriatim_build_state_dir }}/binary.sha256"
+  register: seriatim_checksum_state_stat
+
+- name: Read stored Seriatim fingerprint
+  ansible.builtin.slurp:
+    src: "{{ seriatim_build_state_dir }}/fingerprint.sha256"
+  register: seriatim_stored_fingerprint_result
+  when: seriatim_fingerprint_state_stat.stat.exists
+
+- name: Read stored Seriatim checksum
+  ansible.builtin.slurp:
+    src: "{{ seriatim_build_state_dir }}/binary.sha256"
+  register: seriatim_stored_checksum_result
+  when: seriatim_checksum_state_stat.stat.exists
+
+- name: Record stored Seriatim state values
+  ansible.builtin.set_fact:
+    seriatim_stored_fingerprint: >-
+      {{ seriatim_stored_fingerprint_result.content | b64decode | trim }}
+    seriatim_stored_checksum: >-
+      {{ seriatim_stored_checksum_result.content | b64decode | trim }}
+  when:
+    - seriatim_fingerprint_state_stat.stat.exists
+    - seriatim_checksum_state_stat.stat.exists
+
+- name: Read installed Seriatim version
+  ansible.builtin.command:
+    argv:
+      - "{{ seriatim_binary_path }}"
+      - --version
+  register: seriatim_installed_version_result
+  changed_when: false
+  failed_when: false
+  when: seriatim_installed_binary_stat.stat.exists
+
+- name: Decide whether Seriatim requires rebuilding
+  ansible.builtin.set_fact:
+    seriatim_build_required: >-
+      {{ not seriatim_installed_binary_stat.stat.exists
+         or not seriatim_build_inputs_state_stat.stat.exists
+         or not seriatim_fingerprint_state_stat.stat.exists
+         or not seriatim_checksum_state_stat.stat.exists
+         or seriatim_stored_fingerprint != seriatim_desired_fingerprint
+         or seriatim_stored_checksum != (seriatim_installed_binary_stat.stat.checksum | default(''))
+         or (seriatim_installed_version_result.rc | default(1)) != 0
+         or (seriatim_installed_version_result.stdout | default('')) != 'seriatim version ' ~ seriatim_build_version }}
+
+- name: Build, validate, and install Seriatim
+  when: seriatim_build_required
+  block:
+    - name: Create temporary Seriatim build directory
+      ansible.builtin.tempfile:
+        state: directory
+        prefix: ansible-seriatim-build-
+      register: seriatim_build_tempdir
+
+    - name: Build staged Seriatim binary
+      ansible.builtin.command:
+        argv: >-
+          {{ [seriatim_go_binary, 'build']
+             + seriatim_go_build_flags
+             + ['-ldflags', seriatim_go_ldflags,
+                '-o', seriatim_build_tempdir.path ~ '/seriatim',
+                seriatim_go_package] }}
+        chdir: "{{ seriatim_source_dir }}"
+      environment:
+        GOWORK: "off"
+        GOTOOLCHAIN: local
+        CGO_ENABLED: "0"
+      changed_when: true
+
+    - name: Validate staged Seriatim binary
+      ansible.builtin.command:
+        argv:
+          - "{{ seriatim_build_tempdir.path }}/seriatim"
+          - --version
+      register: seriatim_staged_version_result
+      changed_when: false
+      failed_when: >-
+        seriatim_staged_version_result.rc != 0 or
+        seriatim_staged_version_result.stdout != 'seriatim version ' ~ seriatim_build_version
+
+    - name: Install validated Seriatim binary
+      ansible.builtin.copy:
+        src: "{{ seriatim_build_tempdir.path }}/seriatim"
+        dest: "{{ seriatim_binary_path }}"
+        remote_src: true
+        owner: root
+        group: root
+        mode: "0755"
+
+    - name: Validate installed Seriatim binary
+      ansible.builtin.command:
+        argv:
+          - "{{ seriatim_binary_path }}"
+          - --version
+      register: seriatim_new_installed_version_result
+      changed_when: false
+      failed_when: >-
+        seriatim_new_installed_version_result.rc != 0 or
+        seriatim_new_installed_version_result.stdout != 'seriatim version ' ~ seriatim_build_version
+
+    - name: Calculate installed Seriatim checksum
+      ansible.builtin.stat:
+        path: "{{ seriatim_binary_path }}"
+        checksum_algorithm: sha256
+      register: seriatim_new_binary_stat
+
+    - name: Create Seriatim build state directory
+      ansible.builtin.file:
+        path: "{{ seriatim_build_state_dir }}"
+        state: directory
+        owner: root
+        group: root
+        mode: "0755"
+
+    - name: Record Seriatim build inputs
+      ansible.builtin.copy:
+        content: "{{ seriatim_build_inputs }}\n"
+        dest: "{{ seriatim_build_state_dir }}/build-inputs.json"
+        owner: root
+        group: root
+        mode: "0644"
+
+    - name: Record Seriatim build fingerprint
+      ansible.builtin.copy:
+        content: "{{ seriatim_desired_fingerprint }}\n"
+        dest: "{{ seriatim_build_state_dir }}/fingerprint.sha256"
+        owner: root
+        group: root
+        mode: "0644"
+
+    - name: Record installed Seriatim checksum
+      ansible.builtin.copy:
+        content: "{{ seriatim_new_binary_stat.stat.checksum }}\n"
+        dest: "{{ seriatim_build_state_dir }}/binary.sha256"
+        owner: root
+        group: root
+        mode: "0644"
+
+  always:
+    - name: Remove temporary Seriatim build directory
+      ansible.builtin.file:
+        path: "{{ seriatim_build_tempdir.path }}"
+        state: absent
+      when: seriatim_build_tempdir.path is defined
diff --git a/tasks/main.yml b/tasks/main.yml
index 328a2b7..fe3f3be 100644
--- a/tasks/main.yml
+++ b/tasks/main.yml
@@ -7,3 +7,6 @@
 
 - name: Manage Seriatim source checkout
   ansible.builtin.import_tasks: source.yml
+
+- name: Build and install Seriatim
+  ansible.builtin.import_tasks: build.yml