diff --git a/.github/workflows/android.yml b/.github/workflows/android.yml
index 565f713..bec50c3 100644
--- a/.github/workflows/android.yml
+++ b/.github/workflows/android.yml
@@ -14,6 +14,8 @@ jobs:
     timeout-minutes: 45
     steps:
       - uses: actions/checkout@d23441a48e516b6c34aea4fa41551a30e30af803 # v6.1.0
+      - name: Test release signing helper
+        run: ./scripts/test-sign-latest-alpha.sh
       - uses: actions/setup-java@b6effb05e454b25005698d916606bdc6ffcbf961 # v5.7.0
         with:
           distribution: temurin
diff --git a/README.md b/README.md
index dd931e9..c6ef164 100644
--- a/README.md
+++ b/README.md
@@ -140,9 +140,11 @@ With an emulator or device running:
 The debug APK is written to
 `app/build/outputs/apk/debug/app-debug.apk`.
 
-Release signing is deliberately local and secret-free in Git. See the
+Release signing is deliberately local and secret-free in Git. Once the current
+`main` commit passes CI, `./scripts/sign-latest-alpha.sh` downloads and verifies
+its exact candidate before prompting locally for the signing passwords. See the
 [release-signing guide](docs/development/release-signing.md) to create and back
-up the long-lived key, produce a verified signed APK, and generate its checksum.
+up the long-lived key and verify the signed APK.
 The [technical-alpha guide](docs/alpha-testing.md) defines installation, update,
 test, feedback, diagnostics, and metrics boundaries.
 
diff --git a/docs/development/release-signing.md b/docs/development/release-signing.md
index 3738b9e..308cc04 100644
--- a/docs/development/release-signing.md
+++ b/docs/development/release-signing.md
@@ -161,18 +161,50 @@ validating the Gradle wrapper, checking the wrapper distribution, and enforcing
 Gradle dependency checksums. Review changes to those pins and checksums as
 supply-chain changes before signing a new candidate.
 
-To sign the exact candidate produced by CI, first identify the successful
-`Android` run for the intended commit:
+### Preferred local path
+
+From a clean checkout of current `main`, run:
 
 ```bash
+git switch main
 git pull --ff-only
+./scripts/sign-latest-alpha.sh
+```
+
+The script finds the successful `Android` push run for the exact checked-out
+commit. It refuses tracked local changes, a stale checkout, a failed run, a run
+from another branch, or a mismatched commit. It downloads the uniquely named CI
+artifact into an owner-only temporary directory and passes it to the existing
+signer, which performs the checksum, build-metadata, package, version, alignment,
+and certificate checks. The temporary download is removed on exit.
+
+The standard keystore location from this guide is used automatically:
+`$HOME/.local/share/threadline/signing/threadline-release.p12`. Override the
+non-secret path or alias only when needed:
+
+```bash
+export THREADLINE_RELEASE_STORE_FILE=/path/to/threadline-release.p12
+export THREADLINE_RELEASE_KEY_ALIAS=threadline-release
+./scripts/sign-latest-alpha.sh
+unset THREADLINE_RELEASE_STORE_FILE THREADLINE_RELEASE_KEY_ALIAS
+```
+
+Both passwords are still entered interactively without echoing. They are passed
+to `apksigner` through its process environment, cleared when the signer exits,
+and never written to a file or command-line argument.
+
+### Manual candidate selection
+
+For troubleshooting or deliberate selection of an older successful run, first
+confirm that the run succeeded and its `headSha` equals the local `HEAD`:
+
+```bash
 git rev-parse HEAD
 gh run list --workflow Android --branch main --limit 5
 gh run view RUN_ID --json conclusion,headSha,url
 ```
 
-Confirm that `conclusion` is `success` and `headSha` equals the local `HEAD`.
-Then download and verify the artifact:
+Then download the exact artifact:
 
 ```bash
 threadline_candidate_dir=$(mktemp -d)
@@ -203,8 +235,8 @@ rm -r -- "$threadline_candidate_dir"
 unset threadline_candidate_apk threadline_candidate_dir threadline_candidate_name
 ```
 
-The helper verifies the candidate checksum, source commit, application ID, and
-version before asking for signing passwords. Omitting the APK argument keeps the
+The signing helper verifies the candidate checksum, source commit, application
+ID, and version before asking for passwords. Omitting the APK argument keeps the
 original local-build path and runs `assembleRelease` before signing.
 
 For non-interactive automation, the helper also accepts
diff --git a/scripts/sign-latest-alpha.sh b/scripts/sign-latest-alpha.sh
new file mode 100755
index 0000000..bf1f1cd
--- /dev/null
+++ b/scripts/sign-latest-alpha.sh
@@ -0,0 +1,93 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+script_dir=$(CDPATH= cd -- "$(dirname -- "$0")" && pwd -P)
+repository_dir=$(CDPATH= cd -- "$script_dir/.." && pwd -P)
+# shellcheck source=project-metadata.sh
+THREADLINE_METADATA_REPOSITORY_DIR=$repository_dir
+. "$script_dir/project-metadata.sh"
+unset THREADLINE_METADATA_REPOSITORY_DIR
+
+if (( $# != 0 )); then
+    echo "Usage: $0" >&2
+    exit 64
+fi
+
+if ! command -v gh >/dev/null 2>&1; then
+    echo "GitHub CLI is required. Install gh and authenticate before signing." >&2
+    exit 1
+fi
+if ! gh auth status >/dev/null 2>&1; then
+    echo "GitHub CLI is not authenticated. Run: gh auth login" >&2
+    exit 1
+fi
+if ! git -C "$repository_dir" diff --quiet ||
+    ! git -C "$repository_dir" diff --cached --quiet; then
+    echo "Refusing to sign from a checkout with tracked changes." >&2
+    exit 1
+fi
+
+current_commit=$(git -C "$repository_dir" rev-parse HEAD)
+main_commit=$(gh api 'repos/{owner}/{repo}/commits/main' --jq .sha)
+if [[ $current_commit != "$main_commit" ]]; then
+    echo "This checkout is not current main." >&2
+    echo "Switch to main and pull with --ff-only before signing." >&2
+    exit 1
+fi
+
+run_id=$(
+    gh run list \
+        --workflow Android \
+        --branch main \
+        --commit "$current_commit" \
+        --event push \
+        --status success \
+        --limit 1 \
+        --json databaseId \
+        --jq '.[0].databaseId // empty'
+)
+if [[ -z $run_id ]]; then
+    echo "No successful main-branch Android push run exists for $current_commit." >&2
+    echo "Wait for the required Android workflow to pass before signing." >&2
+    exit 1
+fi
+
+IFS=$'\t' read -r \
+    run_workflow run_conclusion run_event run_branch run_commit run_url < <(
+        gh run view "$run_id" \
+            --json workflowName,conclusion,event,headBranch,headSha,url \
+            --jq '[.workflowName, .conclusion, .event, .headBranch, .headSha, .url] | @tsv'
+    )
+if [[ $run_workflow != Android ]] ||
+    [[ $run_conclusion != success ]] ||
+    [[ $run_event != push ]] ||
+    [[ $run_branch != main ]] ||
+    [[ $run_commit != "$current_commit" ]]; then
+    echo "GitHub run $run_id does not match this checkout's successful main build." >&2
+    exit 1
+fi
+
+candidate_dir=$(mktemp -d "${TMPDIR:-/tmp}/threadline-alpha.XXXXXXXX")
+cleanup() {
+    rm -r -- "$candidate_dir"
+}
+trap cleanup EXIT
+
+candidate_name="threadline-${THREADLINE_VERSION_NAME}-UNSIGNED-${current_commit:0:12}"
+candidate_apk="$candidate_dir/threadline-${THREADLINE_VERSION_NAME}-UNSIGNED.apk"
+
+echo "Downloading verified candidate from: $run_url"
+gh run download "$run_id" \
+    --name "$candidate_name" \
+    --dir "$candidate_dir"
+
+if [[ ! -f $candidate_apk ]]; then
+    echo "Downloaded artifact did not contain: $(basename -- "$candidate_apk")" >&2
+    exit 1
+fi
+
+THREADLINE_RELEASE_STORE_FILE=${THREADLINE_RELEASE_STORE_FILE:-${XDG_DATA_HOME:-$HOME/.local/share}/threadline/signing/threadline-release.p12}
+THREADLINE_RELEASE_KEY_ALIAS=${THREADLINE_RELEASE_KEY_ALIAS:-threadline-release}
+export THREADLINE_RELEASE_STORE_FILE THREADLINE_RELEASE_KEY_ALIAS
+
+"$script_dir/build-signed-alpha.sh" "$candidate_apk"
diff --git a/scripts/test-sign-latest-alpha.sh b/scripts/test-sign-latest-alpha.sh
new file mode 100755
index 0000000..56884fd
--- /dev/null
+++ b/scripts/test-sign-latest-alpha.sh
@@ -0,0 +1,138 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+script_dir=$(CDPATH= cd -- "$(dirname -- "$0")" && pwd -P)
+repository_dir=$(CDPATH= cd -- "$script_dir/.." && pwd -P)
+test_root=$(mktemp -d "${TMPDIR:-/tmp}/threadline-sign-test.XXXXXXXX")
+trap 'rm -r -- "$test_root"' EXIT
+
+test_repository=$test_root/repository
+test_bin=$test_root/bin
+test_home=$test_root/home
+signer_log=$test_root/signer.log
+mkdir -p "$test_repository/scripts" "$test_bin" "$test_home"
+cp "$script_dir/sign-latest-alpha.sh" "$test_repository/scripts/"
+cp "$script_dir/project-metadata.sh" "$test_repository/scripts/"
+
+cat > "$test_repository/gradle.properties" <<'EOF'
+threadline.releaseApplicationId=io.github.r055le.threadline
+threadline.versionCode=10005
+threadline.versionName=0.1.0-alpha.5
+EOF
+
+cat > "$test_repository/scripts/build-signed-alpha.sh" <<'EOF'
+#!/usr/bin/env bash
+set -euo pipefail
+[[ -f $1 ]]
+{
+    printf 'candidate=%s\n' "$1"
+    printf 'store=%s\n' "$THREADLINE_RELEASE_STORE_FILE"
+    printf 'alias=%s\n' "$THREADLINE_RELEASE_KEY_ALIAS"
+} > "$THREADLINE_TEST_SIGNER_LOG"
+EOF
+chmod +x "$test_repository/scripts/build-signed-alpha.sh"
+
+cat > "$test_bin/gh" <<'EOF'
+#!/usr/bin/env bash
+set -euo pipefail
+
+case "${1:-} ${2:-}" in
+    "auth status")
+        exit 0
+        ;;
+    "api repos/{owner}/{repo}/commits/main")
+        printf '%s\n' "${THREADLINE_TEST_MAIN_COMMIT:-$THREADLINE_TEST_CURRENT_COMMIT}"
+        ;;
+    "run list")
+        [[ ${THREADLINE_TEST_NO_RUN:-0} == 1 ]] || printf '9001\n'
+        ;;
+    "run view")
+        run_commit=${THREADLINE_TEST_RUN_COMMIT:-$THREADLINE_TEST_CURRENT_COMMIT}
+        printf 'Android\tsuccess\tpush\tmain\t%s\thttps://example.invalid/run/9001\n' \
+            "$run_commit"
+        ;;
+    "run download")
+        shift 2
+        artifact_name=
+        destination=
+        while (( $# > 0 )); do
+            case "$1" in
+                --name)
+                    artifact_name=$2
+                    shift 2
+                    ;;
+                --dir)
+                    destination=$2
+                    shift 2
+                    ;;
+                *)
+                    shift
+                    ;;
+            esac
+        done
+        expected_name="threadline-0.1.0-alpha.5-UNSIGNED-${THREADLINE_TEST_CURRENT_COMMIT:0:12}"
+        [[ $artifact_name == "$expected_name" ]]
+        printf 'unsigned fixture\n' > "$destination/threadline-0.1.0-alpha.5-UNSIGNED.apk"
+        ;;
+    *)
+        echo "Unexpected gh invocation: $*" >&2
+        exit 1
+        ;;
+esac
+EOF
+chmod +x "$test_bin/gh"
+
+git -C "$test_repository" init --quiet --initial-branch=main
+git -C "$test_repository" config user.email threadline-test@example.invalid
+git -C "$test_repository" config user.name "Threadline test"
+git -C "$test_repository" add .
+git -C "$test_repository" commit --quiet -m fixture
+test_commit=$(git -C "$test_repository" rev-parse HEAD)
+
+PATH="$test_bin:$PATH" \
+HOME=$test_home \
+THREADLINE_TEST_CURRENT_COMMIT=$test_commit \
+THREADLINE_TEST_SIGNER_LOG=$signer_log \
+    "$test_repository/scripts/sign-latest-alpha.sh"
+
+grep -F "store=$test_home/.local/share/threadline/signing/threadline-release.p12" \
+    "$signer_log" >/dev/null
+grep -F "alias=threadline-release" "$signer_log" >/dev/null
+candidate_path=$(sed -n 's/^candidate=//p' "$signer_log")
+[[ -n $candidate_path && ! -e $(dirname -- "$candidate_path") ]]
+
+rm -f "$signer_log"
+if PATH="$test_bin:$PATH" \
+    HOME=$test_home \
+    THREADLINE_TEST_CURRENT_COMMIT=$test_commit \
+    THREADLINE_TEST_MAIN_COMMIT=0000000000000000000000000000000000000000 \
+    THREADLINE_TEST_SIGNER_LOG=$signer_log \
+        "$test_repository/scripts/sign-latest-alpha.sh" 2>/dev/null; then
+    echo "Stale checkout was accepted." >&2
+    exit 1
+fi
+[[ ! -e $signer_log ]]
+
+if PATH="$test_bin:$PATH" \
+    HOME=$test_home \
+    THREADLINE_TEST_CURRENT_COMMIT=$test_commit \
+    THREADLINE_TEST_RUN_COMMIT=0000000000000000000000000000000000000000 \
+    THREADLINE_TEST_SIGNER_LOG=$signer_log \
+        "$test_repository/scripts/sign-latest-alpha.sh" 2>/dev/null; then
+    echo "Mismatched run commit was accepted." >&2
+    exit 1
+fi
+[[ ! -e $signer_log ]]
+
+if PATH="$test_bin:$PATH" \
+    HOME=$test_home \
+    THREADLINE_TEST_CURRENT_COMMIT=$test_commit \
+    THREADLINE_TEST_NO_RUN=1 \
+    THREADLINE_TEST_SIGNER_LOG=$signer_log \
+        "$test_repository/scripts/sign-latest-alpha.sh" 2>/dev/null; then
+    echo "Missing successful run was accepted." >&2
+    exit 1
+fi
+[[ ! -e $signer_log ]]
+
+printf 'sign-latest-alpha tests passed\n'