diff --git a/Makefile b/Makefile
index 393fe5f..379fe52 100644
--- a/Makefile
+++ b/Makefile
@@ -10,6 +10,7 @@ validate: test manifests shellcheck
 test:
 	ruby -Itest test/release_manifest_test.rb
 	ruby -Itest test/release_notes_test.rb
+	ruby -Itest test/web_ui_pin_test.rb
 
 manifests:
 	ruby script/manifest validate examples/release.yml
@@ -18,6 +19,7 @@ manifests:
 
 shellcheck:
 	bash -n scripts/*.sh
+	ruby -c script/verify-web-ui-pin
 
 actionlint:
 	go run github.com/rhysd/actionlint/cmd/actionlint@v1.7.7
diff --git a/README.md b/README.md
index a347274..f377270 100644
--- a/README.md
+++ b/README.md
@@ -34,8 +34,11 @@ suite Release record. It performs no Rust or Flutter compilation.
 1. Copy `examples/release.yml` to `releases/YYYY.MM.PATCH.yml`.
 2. Set each component to a full 40-character commit SHA.
 3. Set versions and tags to the metadata already committed at those SHAs.
-4. Commit the manifest directly to `main` and wait for `Validate release manifests`.
-5. Approve the `release` Environment when approval is configured.
+4. Confirm the server commit's `synctv-web-ui/web-ui.production.toml` pins the same App
+   repository and commit as the manifest. Its production `revision` must equal
+   that full commit SHA.
+5. Commit the manifest directly to `main` and wait for `Validate release manifests`.
+6. Approve the `release` Environment when approval is configured.
 
 Run the same validation locally:
 
diff --git a/docs/runbook.md b/docs/runbook.md
index d12af4c..c94d6ad 100644
--- a/docs/runbook.md
+++ b/docs/runbook.md
@@ -2,7 +2,9 @@
 
 ## Normal release
 
-1. Prepare final version commits in both component repositories.
+1. Prepare final version commits in both component repositories. The server's
+   `synctv-web-ui/web-ui.production.toml` must pin the final App commit in both `revision`
+   and `commit`.
 2. Add one `releases/YYYY.MM.PATCH.yml` manifest and commit it directly to `main`.
 3. Review the `Validate release manifests` result.
 4. Approve the `release` Environment when approval is configured.
diff --git a/lib/web_ui_pin.rb b/lib/web_ui_pin.rb
new file mode 100644
index 0000000..cfd1d91
--- /dev/null
+++ b/lib/web_ui_pin.rb
@@ -0,0 +1,66 @@
+# frozen_string_literal: true
+
+require "json"
+
+class WebUiPin
+  REQUIRED_KEYS = %w[kind repository revision commit].freeze
+  GITHUB_REPOSITORY = %r{\A(?:https://github\.com/|ssh://git@github\.com/|git@github\.com:)([A-Za-z0-9_.-]+/[A-Za-z0-9_.-]+?)(?:\.git)?\z}
+  COMMIT = /\A[0-9a-f]{40}\z/
+
+  def self.verify!(path, expected_repository:, expected_commit:)
+    source = parse_source(File.read(path, encoding: "UTF-8"))
+    missing = REQUIRED_KEYS - source.keys
+    raise ArgumentError, "Web UI source is missing #{missing.join(", ")}" unless missing.empty?
+    raise ArgumentError, "Web UI source kind must be git" unless source.fetch("kind") == "git"
+
+    repository = github_repository(source.fetch("repository"))
+    unless repository == expected_repository
+      raise ArgumentError, "Web UI repository #{repository} differs from #{expected_repository}"
+    end
+
+    commit = source.fetch("commit")
+    raise ArgumentError, "Web UI commit must be a full lowercase SHA" unless COMMIT.match?(commit)
+    revision = source.fetch("revision")
+    unless revision == commit
+      raise ArgumentError, "Web UI production revision must equal its pinned commit"
+    end
+    return true if commit == expected_commit
+
+    raise ArgumentError, "Web UI commit #{commit} differs from #{expected_commit}"
+  end
+
+  def self.parse_source(text)
+    current_table = nil
+    source = {}
+    text.each_line.with_index(1) do |raw_line, line_number|
+      line = raw_line.strip
+      next if line.empty? || line.start_with?("#")
+
+      if (table = line.match(/\A\[([A-Za-z0-9_.-]+)\]\z/))
+        current_table = table[1]
+        next
+      end
+      next unless current_table == "source"
+
+      assignment = line.match(/\A([A-Za-z0-9-]+)\s*=\s*("(?:[^"\\]|\\.)*")\s*(?:#.*)?\z/)
+      raise ArgumentError, "invalid Web UI source value on line #{line_number}" unless assignment
+
+      key = assignment[1]
+      raise ArgumentError, "duplicate Web UI source key #{key}" if source.key?(key)
+
+      source[key] = JSON.parse(assignment[2])
+    end
+    raise ArgumentError, "Web UI configuration is missing [source]" if source.empty?
+
+    source
+  end
+
+  def self.github_repository(value)
+    match = GITHUB_REPOSITORY.match(value)
+    raise ArgumentError, "Web UI repository must be a GitHub repository URL" unless match
+
+    match[1]
+  end
+
+  private_class_method :parse_source, :github_repository
+end
diff --git a/script/verify-web-ui-pin b/script/verify-web-ui-pin
new file mode 100644
index 0000000..241923b
--- /dev/null
+++ b/script/verify-web-ui-pin
@@ -0,0 +1,17 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+require_relative "../lib/web_ui_pin"
+
+begin
+  config = ARGV.fetch(0) { abort "usage: verify-web-ui-pin CONFIG REPOSITORY COMMIT" }
+  repository = ARGV.fetch(1) { abort "usage: verify-web-ui-pin CONFIG REPOSITORY COMMIT" }
+  commit = ARGV.fetch(2) { abort "usage: verify-web-ui-pin CONFIG REPOSITORY COMMIT" }
+  abort "usage: verify-web-ui-pin CONFIG REPOSITORY COMMIT" unless ARGV.length == 3
+
+  WebUiPin.verify!(config, expected_repository: repository, expected_commit: commit)
+  puts "Web UI pins #{repository}@#{commit}."
+rescue ArgumentError => error
+  warn error.message
+  exit 1
+end
diff --git a/scripts/preflight.sh b/scripts/preflight.sh
index f2ced13..939e44a 100755
--- a/scripts/preflight.sh
+++ b/scripts/preflight.sh
@@ -54,8 +54,11 @@ download_file "$BACKEND_REPOSITORY" "$BACKEND_COMMIT" docs/package-lock.json "$t
 download_file "$BACKEND_REPOSITORY" "$BACKEND_COMMIT" docs/src/lib/project.ts "$tmp_dir/project.ts"
 download_file "$BACKEND_REPOSITORY" "$BACKEND_COMMIT" docker-compose.yml "$tmp_dir/docker-compose.yml"
 download_file "$BACKEND_REPOSITORY" "$BACKEND_COMMIT" helm/synctv/README.md "$tmp_dir/helm-readme.md"
+download_file "$BACKEND_REPOSITORY" "$BACKEND_COMMIT" synctv-web-ui/web-ui.production.toml "$tmp_dir/web-ui.production.toml"
 download_file "$APP_REPOSITORY" "$APP_COMMIT" pubspec.yaml "$tmp_dir/pubspec.yaml"
 
+ruby script/verify-web-ui-pin "$tmp_dir/web-ui.production.toml" "$APP_REPOSITORY" "$APP_COMMIT"
+
 cargo_version="$(ruby -e '
   text = File.read(ARGV.fetch(0))
   section = text[/^\[workspace\.package\]\s*$.*?(?=^\[|\z)/m] or abort "workspace.package is missing"
diff --git a/test/web_ui_pin_test.rb b/test/web_ui_pin_test.rb
new file mode 100644
index 0000000..2f4da50
--- /dev/null
+++ b/test/web_ui_pin_test.rb
@@ -0,0 +1,103 @@
+# frozen_string_literal: true
+
+require "minitest/autorun"
+require "tempfile"
+require_relative "../lib/web_ui_pin"
+
+class WebUiPinTest < Minitest::Test
+  COMMIT = "b" * 40
+
+  def verify(source, repository: "synctv-org/synctv-app", commit: COMMIT)
+    file = Tempfile.new(["web-ui", ".toml"])
+    file.write("schema-version = 1\n\n[source]\n#{source}")
+    file.close
+    WebUiPin.verify!(file.path, expected_repository: repository, expected_commit: commit)
+  ensure
+    file&.unlink
+  end
+
+  def test_accepts_matching_https_pin
+    assert verify(<<~TOML)
+      kind = "git"
+      repository = "https://github.com/synctv-org/synctv-app.git"
+      revision = "#{COMMIT}"
+      commit = "#{COMMIT}"
+    TOML
+  end
+
+  def test_accepts_matching_ssh_pin
+    assert verify(<<~TOML)
+      kind = "git"
+      repository = "git@github.com:synctv-org/synctv-app.git"
+      revision = "#{COMMIT}"
+      commit = "#{COMMIT}"
+    TOML
+  end
+
+  def test_rejects_a_floating_production_revision
+    error = assert_raises(ArgumentError) do
+      verify(<<~TOML)
+        kind = "git"
+        repository = "https://github.com/synctv-org/synctv-app.git"
+        revision = "refs/tags/v1.2.3"
+        commit = "#{COMMIT}"
+      TOML
+    end
+
+    assert_includes error.message, "revision must equal its pinned commit"
+  end
+
+  def test_rejects_non_git_source
+    error = assert_raises(ArgumentError) do
+      verify(<<~TOML)
+        kind = "dist"
+        repository = "https://github.com/synctv-org/synctv-app.git"
+        revision = "#{COMMIT}"
+        commit = "#{COMMIT}"
+      TOML
+    end
+
+    assert_includes error.message, "kind must be git"
+  end
+
+  def test_rejects_repository_mismatch
+    error = assert_raises(ArgumentError) do
+      verify(<<~TOML)
+        kind = "git"
+        repository = "https://github.com/other/app.git"
+        revision = "#{COMMIT}"
+        commit = "#{COMMIT}"
+      TOML
+    end
+
+    assert_includes error.message, "differs from synctv-org/synctv-app"
+  end
+
+  def test_rejects_commit_mismatch
+    mismatched_commit = "a" * 40
+    error = assert_raises(ArgumentError) do
+      verify(<<~TOML)
+        kind = "git"
+        repository = "https://github.com/synctv-org/synctv-app.git"
+        revision = "#{mismatched_commit}"
+        commit = "#{mismatched_commit}"
+      TOML
+    end
+
+    assert_includes error.message, "differs from #{COMMIT}"
+  end
+
+  def test_rejects_duplicate_source_keys
+    error = assert_raises(ArgumentError) do
+      verify(<<~TOML)
+        kind = "git"
+        kind = "git"
+        repository = "https://github.com/synctv-org/synctv-app.git"
+        revision = "#{COMMIT}"
+        commit = "#{COMMIT}"
+      TOML
+    end
+
+    assert_includes error.message, "duplicate Web UI source key kind"
+  end
+end