diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
new file mode 100644
index 0000000..0eb40d9
--- /dev/null
+++ b/.github/workflows/test.yml
@@ -0,0 +1,31 @@
+name: Tests
+
+on:
+  pull_request:
+  push:
+    branches: [master]
+  workflow_dispatch:
+
+jobs:
+  self-tests:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          persist-credentials: false
+
+      # An Arch container for vercmp: version ordering has to be decided by
+      # the same comparator pacman uses on users' machines.
+      - name: Run self-tests
+        run: |
+          docker run --rm \
+            -v "$PWD:/workspace:ro" \
+            -w /workspace \
+            archlinux:base-devel bash -lc '
+              set -euo pipefail
+              pacman -Syu --noconfirm jq
+              ./bin/sync-upstream self-test
+              ./bin/omarchy-pkgs self-test
+            '
diff --git a/README.md b/README.md
index 3530dab..6ba724c 100644
--- a/README.md
+++ b/README.md
@@ -258,8 +258,41 @@ bin/sync-upstream openai-codex-desktop  # Update specific packages
 
 Some vendors publish a release feed of their own that is faster and more precise
 than the AUR packaging of it. Those packages are `source: local` — Omarchy owns
-the PKGBUILD — and provide `.omarchy/upstream.sh`, a hook that reports the newest
-upstream release as JSON on stdout:
+the PKGBUILD — and declare where releases come from in one of two ways.
+
+A vendor shipping tagged GitHub releases with a checksum manifest asset is pure
+data, declared as `upstream` in `.omarchy/package.json` with no code at all:
+
+```json
+"upstream": {
+  "github": "jdx/mise",
+  "checksums": "SHASUMS256.txt",
+  "assets": {
+    "x86_64": "mise-{tag}-linux-x64.tar.xz",
+    "aarch64": "mise-{tag}-linux-arm64.tar.xz"
+  }
+}
+```
+
+`{tag}` and `{pkgver}` interpolate into asset names; a leading `v` on the tag is
+stripped for `pkgver`; drafts and prereleases are ignored. Only the 100 most
+recent releases are considered. The provider fails closed on anything it cannot
+read — an unusable tag, timestamp, or checksum stops the sync rather than being
+skipped.
+
+A package may also declare `"min_release_age": "24h"` (`s`/`m`/`h`/`d` suffix or
+bare seconds) to quarantine fresh releases until maintainers have had time to
+pull a bad or compromised one. The newest release that has cleared the window
+ships, so a fast release cadence cannot starve updates. The window is enforced
+centrally: whatever reports the release must prove its age via `published_at`,
+or the sync fails. A maintainer deliberately shipping inside the window runs
+`BYPASS_MIN_RELEASE_AGE=1 bin/sync-upstream <package>` locally and merges the
+result through a normal PR; scheduled automation never sets the bypass.
+
+A vendor whose feed fits no convention (a Debian package index, a bare
+version.txt) instead provides `.omarchy/upstream.sh`, a hook that reports the
+newest upstream release as JSON on stdout — declaring both an `upstream` block
+and a hook is an error:
 
 ```json
 {
@@ -281,7 +314,11 @@ back cannot walk the repository backwards.
 Hooks should read checksums from whatever manifest the vendor publishes rather
 than downloading the artifacts — see `pkgbuilds/openai-codex-desktop/.omarchy/upstream.sh`,
 which reads OpenAI's Debian package index and never fetches the 750 MB of debs
-it describes.
+it describes. Hooks honoring `min_release_age` receive the window as
+`MIN_RELEASE_AGE_SECONDS` and report `published_at` alongside `pkgver`.
+
+`bin/sync-upstream self-test` runs offline fixture tests over the release
+selection, quarantine backstop, duration parsing, and manifest validation.
 
 ### Sync Rebuild Triggers
 
@@ -462,7 +499,9 @@ Minimal examples:
 
 Fields:
 
-- `source`: `aur` or `local`. A `local` package can still follow an upstream release with an `.omarchy/upstream.sh` hook.
+- `source`: `aur` or `local`. A `local` package can still follow an upstream release, either declaratively via `upstream` or with an `.omarchy/upstream.sh` hook.
+- `upstream`: optional for `local` packages whose vendor ships tagged GitHub releases with a checksum manifest asset. `{ "github": "owner/repo", "checksums": "SHASUMS256.txt", "assets": { "<arch>": "name-{tag}.tar.xz" } }` — see [Sync Upstream Releases](#sync-upstream-releases). Mutually exclusive with `.omarchy/upstream.sh`.
+- `min_release_age`: optional quarantine for upstream releases (`"24h"`, `"2d"`, or bare seconds). The newest release older than the window ships; anything younger waits, and a release whose age cannot be proven fails the sync. Bypass deliberately with `BYPASS_MIN_RELEASE_AGE=1 bin/sync-upstream <package>`.
 - `sync`: optional for AUR packages; defaults to `true`. Set `false` for AUR-origin packages that Omarchy maintains manually.
 - `aur`: optional AUR package name when it differs from the local package directory, usually for split packages.
 - `release_ring`: optional. `fast` means the package is built directly for stable as well as edge. Packages without a ring build in edge and reach stable through tested artifact promotion (`bin/repo migrate`).
diff --git a/bin/sync-upstream b/bin/sync-upstream
index 93e6f0d..a0da5f3 100755
--- a/bin/sync-upstream
+++ b/bin/sync-upstream
@@ -5,6 +5,7 @@ BUILD_ROOT=$(realpath "${BASH_SOURCE[0]%/*}/..")
 source "$BUILD_ROOT/helpers/message-helpers.sh"
 source "$BUILD_ROOT/helpers/paths.sh"
 source "$BUILD_ROOT/helpers/package-metadata.sh"
+source "$BUILD_ROOT/helpers/upstream-github.sh"
 
 TEMP_DIR=$(mktemp -d)
 trap 'rm -rf "$TEMP_DIR"' EXIT
@@ -17,7 +18,10 @@ Usage: $0 [PACKAGE...]
 
 Update packages that track an upstream vendor release feed instead of the AUR.
 
-A package opts in by providing pkgbuilds/<package>/.omarchy/upstream.sh, a hook
+A package whose upstream ships tagged GitHub releases with a checksum manifest
+opts in declaratively, via "upstream" in .omarchy/package.json (see
+helpers/upstream-github.sh for the schema); no code needed. Anything with a
+bespoke feed provides pkgbuilds/<package>/.omarchy/upstream.sh instead, a hook
 that reports the newest upstream release as JSON on stdout:
 
   {
@@ -31,11 +35,25 @@ the unsuffixed sha256sums array. An empty object ({}) reports no update.
 When the reported version is newer than the checked-in one, pkgver and the
 listed checksum arrays are rewritten and pkgrel is reset to 1.
 
+A package may declare "min_release_age" in .omarchy/package.json ("24h", "2d",
+or bare seconds) to quarantine fresh releases until maintainers have had time
+to pull a bad or compromised one. The window is exported to the hook as
+MIN_RELEASE_AGE_SECONDS so it can select the newest release that has already
+cleared it, and enforced here as a backstop: the hook must then report
+"published_at" (ISO 8601), and a release younger than the window is treated
+as no update. A maintainer shipping an emergency update inside the window
+runs: BYPASS_MIN_RELEASE_AGE=1 $0 <package>. Scheduled automation never sets
+the bypass, so the resulting change still goes through a reviewed PR.
+
 Arguments:
   PACKAGE    One or more package names to update (optional)
 
+Commands:
+  self-test  Run the offline fixture tests for release selection, the
+             quarantine backstop, and metadata parsing
+
 Examples:
-  $0                          # Update every package with an upstream hook
+  $0                          # Update every package with an upstream source
   $0 openai-codex-desktop     # Update specific packages
 EOF
 }
@@ -143,6 +161,26 @@ set_pkgbuild_array() {
   mv "$rewritten" "$pkgbuild"
 }
 
+# Backstop verdict for a reported release against min_release_age. Returns 0
+# when old enough (or no policy is set, or the bypass is deliberate), 1 when
+# the release is younger than the window, 2 when the report carries no usable
+# published_at and the age cannot be established at all.
+release_age_status() {
+  local release="$1" min_age="$2"
+  (( min_age > 0 )) || return 0
+  [[ "${BYPASS_MIN_RELEASE_AGE:-}" != "1" ]] || return 0
+  local published_at published_epoch
+  published_at=$(jq -r '.published_at // empty' <<<"$release")
+  # Strict ISO 8601 before GNU date sees it: date also accepts relative
+  # expressions like "2 days ago", which would let a buggy hook fabricate an
+  # age instead of failing closed.
+  if [[ ! "$published_at" =~ ^[0-9]{4}-[0-9]{2}-[0-9]{2}T[0-9]{2}:[0-9]{2}:[0-9]{2}(\.[0-9]+)?(Z|[+-][0-9]{2}:?[0-9]{2})$ ]] \
+      || ! published_epoch=$(date --date="$published_at" +%s 2>/dev/null); then
+    return 2
+  fi
+  (( $(date +%s) - published_epoch >= min_age )) || return 1
+}
+
 # pacman's own comparator, because nothing else agrees with it at the corners:
 # sort -V calls 1.0a newer than 1.0, vercmp calls it older, and pacman is what
 # decides whether a published package is an upgrade.
@@ -170,6 +208,7 @@ validate_release() {
     and (.sha256sums | to_entries | all(
       .value | type == "array" and length > 0 and all(test("\\A[0-9a-f]{64}\\z"))
     ))
+    and (if has("published_at") then (.published_at | type == "string" and length > 0) else true end)
   ' <<<"$release" >/dev/null
 }
 
@@ -293,21 +332,57 @@ sync_package() {
     return 0
   fi
 
-  if [[ ! -f "$hook" ]]; then
+  local github_repo has_upstream=false
+  github_repo=$(package_upstream_github_repo "$package_dir")
+  if package_has_upstream_provider "$package_dir"; then
+    has_upstream=true
+  fi
+
+  # A present-but-unusable declaration fails loudly; treating it like "no
+  # upstream source" would silently drop the package from scheduled runs.
+  if [[ "$has_upstream" == true && -z "$github_repo" ]]; then
+    print_error "Package $package has an unusable upstream declaration (needs a github owner/repo)"
+    ((++FAILED))
+    return 0
+  fi
+
+  if [[ -n "$github_repo" && -f "$hook" ]]; then
+    print_error "Package $package declares both upstream.github and an upstream.sh hook; keep exactly one"
+    ((++FAILED))
+    return 0
+  fi
+
+  if [[ -z "$github_repo" && ! -f "$hook" ]]; then
     if [[ "$SPECIFIC_MODE" == true ]]; then
-      print_error "Package $package is missing .omarchy/upstream.sh"
+      print_error "Package $package has neither an upstream declaration nor .omarchy/upstream.sh"
       ((++FAILED))
     else
-      print_info "Skipping $package: no upstream hook"
+      print_info "Skipping $package: no upstream source"
       ((++SKIPPED))
     fi
     return 0
   fi
 
+  local min_age
+  if ! min_age=$(package_min_release_age_seconds "$package_dir"); then
+    print_error "Invalid min_release_age in $package_dir/.omarchy/package.json"
+    ((++FAILED))
+    return 0
+  fi
+
   print_info "Checking $package for upstream releases..."
 
   local release
-  if ! release=$(cd "$package_dir" && PACKAGE_NAME="$package" bash .omarchy/upstream.sh); then
+  if [[ -n "$github_repo" ]]; then
+    if ! release=$(github_upstream_release "$package_dir" "$min_age"); then
+      print_error "GitHub release provider failed for $package"
+      ((++FAILED))
+      return 0
+    fi
+  elif ! release=$(cd "$package_dir" && PACKAGE_NAME="$package" \
+      MIN_RELEASE_AGE_SECONDS="$min_age" \
+      BYPASS_MIN_RELEASE_AGE="${BYPASS_MIN_RELEASE_AGE:-}" \
+      bash .omarchy/upstream.sh); then
     print_error "Upstream hook failed for $package"
     ((++FAILED))
     return 0
@@ -331,6 +406,24 @@ sync_package() {
     return 0
   fi
 
+  # Backstop for min_release_age: the selection already honors the window,
+  # but a provider or hook bug must not be able to ship a release younger
+  # than the policy.
+  local age_status=0
+  release_age_status "$release" "$min_age" || age_status=$?
+  case "$age_status" in
+    1)
+      print_warning "  Reported release is inside the ${min_age}s minimum release age; leaving it alone"
+      ((++SKIPPED))
+      return 0
+      ;;
+    2)
+      print_error "min_release_age is set for $package but its source reported no usable published_at; refusing an unverifiable release"
+      ((++FAILED))
+      return 0
+      ;;
+  esac
+
   local pkgver current_pkgver
   pkgver=$(jq -r '.pkgver' <<<"$release")
   current_pkgver=$(get_pkgver "$package_dir")
@@ -363,6 +456,233 @@ sync_package() {
   ((++UPDATED))
 }
 
+# Offline fixture tests: the network fetches in helpers/upstream-github.sh
+# are swapped for fixture readers, everything else runs the production code
+# paths. Covers release selection (fallback past quarantined releases,
+# draft/prerelease filtering, bypass, unchanged version), failure paths
+# (unusable tags/timestamps, missing checksums), checksum template mapping
+# for both architectures, the min_release_age backstop, the duration parser,
+# and manifest validation.
+cmd_self_test() {
+  local failures=0
+
+  check() {
+    local desc="$1" expected="$2" got="$3"
+    if [[ "$expected" == "$got" ]]; then
+      echo "  ok: $desc"
+    else
+      echo "  FAIL: $desc (expected '$expected', got '$got')"
+      failures=$((failures + 1))
+    fi
+  }
+
+  local pkg="$TEMP_DIR/selftest-pkg"
+  mkdir -p "$pkg/.omarchy"
+  printf 'pkgver=1.0.0\npkgrel=1\n' > "$pkg/PKGBUILD"
+  cat > "$pkg/.omarchy/package.json" <<'EOF'
+{
+  "source": "local",
+  "min_release_age": "24h",
+  "upstream": {
+    "github": "example/tool",
+    "checksums": "SHASUMS256.txt",
+    "assets": {
+      "x86_64": "tool-{tag}-x64.tar.xz",
+      "aarch64": "tool-v{pkgver}-arm64.tar.xz"
+    }
+  }
+}
+EOF
+
+  local young old2d old3d
+  young=$(date -u -d '1 hour ago' +%Y-%m-%dT%H:%M:%SZ)
+  old2d=$(date -u -d '2 days ago' +%Y-%m-%dT%H:%M:%SZ)
+  old3d=$(date -u -d '3 days ago' +%Y-%m-%dT%H:%M:%SZ)
+
+  # v2.0.0 is inside the 24h window; v1.9.9/v1.9.8 are a prerelease and a
+  # draft that would outrank v1.9.0 if the filters failed.
+  local sum_x19 sum_a19 sum_x20 sum_a20
+  sum_x19=$(printf 'a%.0s' {1..64})
+  sum_a19=$(printf 'b%.0s' {1..64})
+  sum_x20=$(printf 'c%.0s' {1..64})
+  sum_a20=$(printf 'd%.0s' {1..64})
+
+  FIXTURE_RELEASES=$(jq -n --arg young "$young" --arg old2 "$old2d" --arg old3 "$old3d" '[
+    {tag_name: "v2.0.0", published_at: $young, draft: false, prerelease: false},
+    {tag_name: "v1.9.9", published_at: $old2,  draft: false, prerelease: true},
+    {tag_name: "v1.9.8", published_at: $old2,  draft: true,  prerelease: false},
+    {tag_name: "v1.9.0", published_at: $old2,  draft: false, prerelease: false},
+    {tag_name: "v1.8.0", published_at: $old3,  draft: false, prerelease: false}
+  ]')
+  FIXTURE_CHECKSUMS=$(printf '%s\n' \
+    "$sum_x19  ./tool-v1.9.0-x64.tar.xz" \
+    "$sum_a19  tool-v1.9.0-arm64.tar.xz" \
+    "$sum_x20  *tool-v2.0.0-x64.tar.xz" \
+    "$sum_a20  tool-v2.0.0-arm64.tar.xz")
+
+  github_fetch_releases() { printf '%s' "$FIXTURE_RELEASES"; }
+  github_fetch_checksums() { printf '%s\n' "$FIXTURE_CHECKSUMS"; }
+
+  echo "Release selection:"
+  local out
+  out=$(github_upstream_release "$pkg" 86400 2>/dev/null) || out="<error>"
+  check "quarantine falls back past the young v2.0.0" "1.9.0" "$(jq -r '.pkgver // "<none>"' <<<"$out")"
+  check "selected release reports its published_at" "$old2d" "$(jq -r '.published_at // "<none>"' <<<"$out")"
+  check "x86_64 checksum via {tag} template and ./ prefix" "$sum_x19" "$(jq -r '.sha256sums.x86_64[0] // "<none>"' <<<"$out")"
+  check "aarch64 checksum via {pkgver} template" "$sum_a19" "$(jq -r '.sha256sums.aarch64[0] // "<none>"' <<<"$out")"
+
+  out=$(github_upstream_release "$pkg" 0 2>/dev/null) || out="<error>"
+  check "no policy selects the newest stable release" "2.0.0" "$(jq -r '.pkgver // "<none>"' <<<"$out")"
+  check "prerelease v1.9.9 and draft v1.9.8 are never selected" "" "$(jq -r 'select(.pkgver == "1.9.9" or .pkgver == "1.9.8") | .pkgver' <<<"$out")"
+
+  out=$(BYPASS_MIN_RELEASE_AGE=1 github_upstream_release "$pkg" 86400 2>/dev/null) || out="<error>"
+  check "bypass lifts the quarantine" "2.0.0" "$(jq -r '.pkgver // "<none>"' <<<"$out")"
+  check "x86_64 checksum via * binary-mode prefix" "$sum_x20" "$(jq -r '.sha256sums.x86_64[0] // "<none>"' <<<"$out")"
+
+  out=$(github_upstream_release "$pkg" 8640000 2>/dev/null) || out="<error>"
+  check "everything quarantined reports no update" "{}" "$(jq -c . <<<"$out")"
+
+  printf 'pkgver=1.9.0\npkgrel=1\n' > "$pkg/PKGBUILD"
+  out=$(github_upstream_release "$pkg" 86400 2>/dev/null) || out="<error>"
+  check "already checked in reports no update" "{}" "$(jq -c . <<<"$out")"
+  printf 'pkgver=1.0.0\npkgrel=1\n' > "$pkg/PKGBUILD"
+
+  echo "Failure paths:"
+  local rc
+  FIXTURE_RELEASES=$(jq -n '[{tag_name: "v1.9.0", published_at: "not-a-date", draft: false, prerelease: false}]')
+  rc=0; github_upstream_release "$pkg" 86400 >/dev/null 2>&1 || rc=$?
+  check "invalid published_at fails the sync" "1" "$rc"
+
+  FIXTURE_RELEASES=$(jq -n --arg old "$old2d" '[{tag_name: "release 1.9!", published_at: $old, draft: false, prerelease: false}]')
+  rc=0; github_upstream_release "$pkg" 86400 >/dev/null 2>&1 || rc=$?
+  check "unusable tag fails the sync" "1" "$rc"
+
+  FIXTURE_RELEASES=$(jq -n --arg old "$old2d" '[{tag_name: "v1.9.0", published_at: $old, draft: false, prerelease: false}]')
+  FIXTURE_CHECKSUMS="$sum_x19  ./tool-v1.9.0-x64.tar.xz"
+  rc=0; github_upstream_release "$pkg" 86400 >/dev/null 2>&1 || rc=$?
+  check "missing aarch64 checksum fails the sync" "1" "$rc"
+
+  echo "Quarantine backstop:"
+  local rel st
+  rel=$(jq -n --arg p "$old2d" '{pkgver: "1.9.0", published_at: $p, sha256sums: {}}')
+  st=0; release_age_status "$rel" 86400 || st=$?
+  check "old enough passes" "0" "$st"
+  rel=$(jq -n --arg p "$young" '{pkgver: "2.0.0", published_at: $p, sha256sums: {}}')
+  st=0; release_age_status "$rel" 86400 || st=$?
+  check "too young is held" "1" "$st"
+  st=0; release_age_status "$rel" 0 || st=$?
+  check "no policy passes anything" "0" "$st"
+  st=0; BYPASS_MIN_RELEASE_AGE=1 release_age_status "$rel" 86400 || st=$?
+  check "deliberate bypass passes" "0" "$st"
+  rel=$(jq -n '{pkgver: "2.0.0", sha256sums: {}}')
+  st=0; release_age_status "$rel" 86400 || st=$?
+  check "missing published_at is unprovable" "2" "$st"
+  rel=$(jq -n '{pkgver: "2.0.0", published_at: "2 days ago", sha256sums: {}}')
+  st=0; release_age_status "$rel" 86400 || st=$?
+  check "relative-date expression is unprovable, not an age" "2" "$st"
+  rel=$(jq -n --arg p "$(date -u -d '2 days ago' +%Y-%m-%dT%H:%M:%S+00:00)" '{pkgver: "1.9.0", published_at: $p, sha256sums: {}}')
+  st=0; release_age_status "$rel" 86400 || st=$?
+  check "numeric-offset ISO timestamp passes" "0" "$st"
+
+  echo "Duration parser:"
+  local agepkg="$TEMP_DIR/selftest-age"
+  mkdir -p "$agepkg/.omarchy"
+  check_age() {
+    local json_value="$1" expected="$2" got
+    jq -n "{source: \"local\", min_release_age: $json_value}" > "$agepkg/.omarchy/package.json"
+    got=$(package_min_release_age_seconds "$agepkg") || got="<reject>"
+    check "min_release_age $json_value" "$expected" "$got"
+  }
+  check_age '"24h"' 86400
+  check_age '"90m"' 5400
+  check_age '"2d"' 172800
+  check_age '3600' 3600
+  check_age '"600s"' 600
+  check_age '"010h"' 36000
+  check_age '"abc"' "<reject>"
+  check_age '"24hh"' "<reject>"
+  check_age 'false' "<reject>"
+  check_age '""' "<reject>"
+  check_age '"9999999999"' "<reject>"
+
+  echo "Manifest validation:"
+  printf 'pkgver=1.0.0\n' > "$agepkg/PKGBUILD"
+  local vst
+  echo '{"source": "local", "upstream": false}' > "$agepkg/.omarchy/package.json"
+  vst=0; validate_package_metadata "$agepkg" >/dev/null || vst=$?
+  check "upstream: false is rejected" "1" "$vst"
+  echo '{"source": "local", "upstream": {"github": "example/tool"}}' > "$agepkg/.omarchy/package.json"
+  vst=0; validate_package_metadata "$agepkg" >/dev/null || vst=$?
+  check "upstream without checksums/assets is rejected" "1" "$vst"
+  cp "$pkg/.omarchy/package.json" "$agepkg/.omarchy/package.json"
+  vst=0; validate_package_metadata "$agepkg" >/dev/null || vst=$?
+  check "the real declaration shape is accepted" "0" "$vst"
+
+  # End to end over the real mise-bin package: its checked-in metadata and
+  # PKGBUILD, the full sync_package path (selection, validation, backstop,
+  # rewrite, read-back verification), with only the two network fetches
+  # replaced by mise-shaped fixtures.
+  echo "End-to-end sync_package with the checked-in mise-bin metadata:"
+  local e2e_root="$TEMP_DIR/e2e-pkgbuilds"
+  mkdir -p "$e2e_root"
+  cp -a "$BUILD_ROOT/pkgbuilds/mise-bin" "$e2e_root/mise-bin"
+
+  # Fixture versions extend the checked-in pkgver so they stay newer no
+  # matter what version the real package is at when the test runs.
+  local mise_current mise_aged mise_fresh mise_x64 mise_a64
+  mise_current=$(grep -m1 '^pkgver=' "$e2e_root/mise-bin/PKGBUILD" | cut -d= -f2- | tr -d "\"'")
+  mise_aged="${mise_current}.90"
+  mise_fresh="${mise_current}.91"
+  mise_x64=$(printf 'e%.0s' {1..64})
+  mise_a64=$(printf 'f%.0s' {1..64})
+  FIXTURE_RELEASES=$(jq -n --arg young "$young" --arg old2 "$old2d" \
+    --arg aged "v$mise_aged" --arg fresh "v$mise_fresh" '[
+    {tag_name: $fresh, published_at: $young, draft: false, prerelease: false},
+    {tag_name: $aged,  published_at: $old2,  draft: false, prerelease: false}
+  ]')
+  FIXTURE_CHECKSUMS=$(printf '%s\n' \
+    "$mise_x64  ./mise-v$mise_aged-linux-x64.tar.xz" \
+    "$mise_a64  ./mise-v$mise_aged-linux-arm64.tar.xz")
+
+  local prev_updated=$UPDATED prev_failed=$FAILED
+  PKGBUILDS_DIR="$e2e_root" sync_package mise-bin >/dev/null 2>&1 || true
+  check "sync_package updates without failures" "updated=1 failed=0" \
+    "updated=$((UPDATED - prev_updated)) failed=$((FAILED - prev_failed))"
+  check "the 24h manifest policy holds v$mise_fresh and ships v$mise_aged" "$mise_aged" \
+    "$(grep -m1 '^pkgver=' "$e2e_root/mise-bin/PKGBUILD" | cut -d= -f2-)"
+  check "pkgrel resets to 1" "1" \
+    "$(grep -m1 '^pkgrel=' "$e2e_root/mise-bin/PKGBUILD" | cut -d= -f2-)"
+  check "x86_64 checksum lands in the PKGBUILD" "sha256sums_x86_64=('$mise_x64')" \
+    "$(grep -m1 '^sha256sums_x86_64=' "$e2e_root/mise-bin/PKGBUILD")"
+  check "aarch64 checksum lands in the PKGBUILD" "sha256sums_aarch64=('$mise_a64')" \
+    "$(grep -m1 '^sha256sums_aarch64=' "$e2e_root/mise-bin/PKGBUILD")"
+
+  # A malformed declaration must fail the run loudly, and still be discovered.
+  local badpkg="$e2e_root/selftest-broken"
+  mkdir -p "$badpkg/.omarchy"
+  printf 'pkgver=1.0.0\npkgrel=1\n' > "$badpkg/PKGBUILD"
+  echo '{"source": "local", "upstream": false}' > "$badpkg/.omarchy/package.json"
+  check "malformed upstream stays discoverable for scheduled runs" "yes" \
+    "$(PKGBUILDS_DIR="$e2e_root" packages_for_upstream_sync | grep -qx selftest-broken && echo yes || echo no)"
+  prev_failed=$FAILED
+  PKGBUILDS_DIR="$e2e_root" sync_package selftest-broken >/dev/null 2>&1 || true
+  check "malformed upstream fails the sync instead of skipping" "1" "$((FAILED - prev_failed))"
+  FAILED=0
+
+  echo ""
+  if [[ "$failures" -eq 0 ]]; then
+    print_success "Self-test passed"
+  else
+    print_error "$failures self-test failure(s)"
+    exit 1
+  fi
+}
+
+if [[ ${#SPECIFIC_PACKAGES[@]} -gt 0 && "${SPECIFIC_PACKAGES[0]}" == "self-test" ]]; then
+  cmd_self_test
+  exit 0
+fi
+
 if [[ ${#SPECIFIC_PACKAGES[@]} -gt 0 ]]; then
   SPECIFIC_MODE=true
   for package in "${SPECIFIC_PACKAGES[@]}"; do
diff --git a/helpers/package-metadata.sh b/helpers/package-metadata.sh
index 83ed37a..f73cc19 100644
--- a/helpers/package-metadata.sh
+++ b/helpers/package-metadata.sh
@@ -12,6 +12,8 @@
 #   { "source": "aur", "pkgrel": { "suffix": 1, "offset": 1 } }
 #   { "source": "aur", "rebuild_on": ["qt6-base"] }
 #   { "source": "local" }
+#   { "source": "local", "min_release_age": "24h" }
+#   { "source": "local", "upstream": { "github": "owner/repo", "checksums": "SHASUMS256.txt", "assets": { "x86_64": "name-{tag}-x64.tar.xz" } } }
 #
 # bin/sync-aur also writes upstream_commit for AUR-backed packages, and
 # bin/sync-rebuilds writes rebuilt_against for packages declaring rebuild_on.
@@ -78,6 +80,43 @@ package_is_fast_ring() {
   [[ "$(package_release_ring "$pkgdir")" == "fast" ]]
 }
 
+# Quarantine window for upstream releases, in seconds. Accepts a bare number
+# of seconds or a number suffixed s/m/h/d ("24h", "2d"). Unset means 0 (no
+# hold); an unparseable value -- including a non-string/non-number JSON type
+# like false -- returns 1 so callers fail closed instead of silently dropping
+# the hold. At most 9 digits: enough for three decades in seconds, and small
+# enough that no suffix multiplication can overflow 64-bit arithmetic.
+package_min_release_age_seconds() {
+  local pkgdir="$1" metadata raw
+  metadata=$(metadata_file_for_dir "$pkgdir")
+  if [[ ! -f "$metadata" ]]; then
+    echo 0
+    return 0
+  fi
+  # A present-but-empty value maps to "unparseable", not to "absent": only a
+  # missing key means no hold, so '"min_release_age": ""' cannot silently
+  # disable the quarantine.
+  raw=$(jq -r '
+    if has("min_release_age") | not then ""
+    elif (.min_release_age | type) == "string" or (.min_release_age | type) == "number" then
+      .min_release_age | tostring | if . == "" then "unparseable" else . end
+    else "unparseable" end
+  ' "$metadata")
+  if [[ -z "$raw" ]]; then
+    echo 0
+    return 0
+  fi
+  [[ "$raw" =~ ^([0-9]{1,9})([smhd]?)$ ]] || return 1
+  # Forced base 10: bash arithmetic would otherwise read "010" as octal.
+  local n=$((10#${BASH_REMATCH[1]}))
+  case "${BASH_REMATCH[2]}" in
+    ""|s) echo "$n" ;;
+    m) echo $((n * 60)) ;;
+    h) echo $((n * 3600)) ;;
+    d) echo $((n * 86400)) ;;
+  esac
+}
+
 package_build_skipped() {
   local pkgdir="$1"
   local metadata skip_build
@@ -142,9 +181,18 @@ package_has_upstream_hook() {
   [[ -f "$pkgdir/.omarchy/upstream.sh" ]]
 }
 
+package_has_upstream_provider() {
+  local pkgdir="$1" metadata
+  metadata=$(metadata_file_for_dir "$pkgdir")
+  [[ -f "$metadata" ]] || return 1
+  # Any upstream key counts, valid or not: a malformed declaration must reach
+  # bin/sync-upstream and fail loudly there, not vanish from discovery.
+  jq -e 'has("upstream")' "$metadata" >/dev/null
+}
+
 packages_for_upstream_sync() {
   package_dirs | while IFS= read -r pkgdir; do
-    if package_has_upstream_hook "$pkgdir"; then
+    if package_has_upstream_hook "$pkgdir" || package_has_upstream_provider "$pkgdir"; then
       basename "$pkgdir"
     fi
   done
@@ -313,6 +361,28 @@ validate_package_metadata() {
     *) echo "invalid release_ring for $(basename "$pkgdir"): $ring"; return 1 ;;
   esac
 
+  if ! package_min_release_age_seconds "$pkgdir" >/dev/null; then
+    echo "invalid min_release_age for $(basename "$pkgdir"): must be a number with optional s/m/h/d suffix"
+    return 1
+  fi
+
+  # `has` rather than `// {}`: jq's // treats false as absent, which would
+  # let "upstream": false slip through as an empty declaration.
+  if ! jq -e '
+    if has("upstream") | not then true
+    elif (.upstream | type) != "object" then false
+    else .upstream |
+      ((.github // "") | type == "string" and test("\\A[A-Za-z0-9_.-]+/[A-Za-z0-9_.-]+\\z"))
+      and ((.checksums // "") | type == "string" and length > 0)
+      and ((.assets // {}) | type == "object" and length > 0 and (to_entries | all(
+        (.key | test("\\A[a-z0-9_]+\\z")) and (.value | type == "string" and length > 0)
+      )))
+    end
+  ' "$metadata" >/dev/null; then
+    echo "invalid upstream for $(basename "$pkgdir"): needs github owner/repo, checksums asset name, and an assets arch->name map"
+    return 1
+  fi
+
   pkgrel_type=$(jq -r 'if has("pkgrel") then .pkgrel | type else "missing" end' "$metadata")
   case "$pkgrel_type" in
     object|missing) ;;
diff --git a/helpers/upstream-github.sh b/helpers/upstream-github.sh
new file mode 100644
index 0000000..e37e6ab
--- /dev/null
+++ b/helpers/upstream-github.sh
@@ -0,0 +1,161 @@
+# GitHub-releases upstream provider for bin/sync-upstream.
+#
+# A package whose upstream ships tagged GitHub releases with a checksum
+# manifest asset needs no upstream.sh hook: the whole feed is data, declared
+# in .omarchy/package.json --
+#
+#   "upstream": {
+#     "github": "jdx/mise",
+#     "checksums": "SHASUMS256.txt",
+#     "assets": {
+#       "x86_64": "mise-{tag}-linux-x64.tar.xz",
+#       "aarch64": "mise-{tag}-linux-arm64.tar.xz"
+#     }
+#   }
+#
+# {tag} and {pkgver} interpolate into asset names; tags may carry a leading
+# "v", which is stripped for pkgver. Drafts and prereleases are ignored. The
+# provider emits the same JSON contract as an upstream.sh hook, so
+# bin/sync-upstream's validation and min_release_age backstop apply
+# unchanged; a feed that fits no convention keeps a bespoke upstream.sh.
+
+package_upstream_github_repo() {
+  local pkgdir="$1"
+  # `objects` drops a non-object upstream value (validation rejects those
+  # separately) instead of erroring the jq pipeline.
+  package_metadata_value "$pkgdir" '(.upstream? | objects | .github)' ""
+}
+
+# Fetches sit behind functions so the self-test can replace them with fixture
+# readers; everything below the fetch is deterministic and testable offline.
+# Only the 100 most recent releases are considered -- a bounded search, not
+# pagination. Quarantined releases report no update and wait for the next
+# run; a page with no stable release at all (drafts and prereleases only)
+# fails the sync instead, because a provider-tracked feed suddenly shipping
+# nothing stable is an anomaly worth a loud error, not a silent skip.
+github_fetch_releases() {
+  local repo="$1"
+  curl -fsSL "https://api.github.com/repos/$repo/releases?per_page=100"
+}
+
+github_fetch_checksums() {
+  local repo="$1" tag="$2" asset="$3"
+  curl -fsSL "https://github.com/$repo/releases/download/$tag/$asset"
+}
+
+# Emits the newest qualifying release as hook-contract JSON. min_release_age
+# is honored during selection (newest release older than the window wins,
+# even when a younger one exists) and BYPASS_MIN_RELEASE_AGE=1 lifts it.
+# Unusable tags or timestamps anywhere in the feed fail the sync rather than
+# being skipped: a feed this provider cannot fully read is a feed it should
+# not silently choose from.
+github_upstream_release() {
+  local package_dir="$1" min_age="${2:-0}"
+  local metadata repo checksums_name
+  metadata=$(metadata_file_for_dir "$package_dir")
+
+  repo=$(jq -r '(.upstream? | objects | .github) // ""' "$metadata")
+  if [[ ! "$repo" =~ ^[A-Za-z0-9_.-]+/[A-Za-z0-9_.-]+$ ]]; then
+    echo "invalid upstream.github repository: '${repo:-<empty>}'" >&2
+    return 1
+  fi
+  checksums_name=$(jq -r '(.upstream? | objects | .checksums) // ""' "$metadata")
+  if [[ -z "$checksums_name" ]]; then
+    echo "upstream.checksums names the checksum manifest asset and is required" >&2
+    return 1
+  fi
+  local arches
+  mapfile -t arches < <(jq -r '(.upstream? | objects | .assets) // {} | keys[]' "$metadata")
+  if [[ ${#arches[@]} -eq 0 ]]; then
+    echo "upstream.assets must map at least one architecture to an asset name" >&2
+    return 1
+  fi
+
+  local releases now
+  now=$(date +%s)
+  if ! releases=$(github_fetch_releases "$repo"); then
+    echo "could not fetch the release feed for $repo" >&2
+    return 1
+  fi
+
+  local candidates=0 best_tag="" best_pkgver="" best_published_at=""
+  local tag published_at pkgver published_epoch
+  while IFS=$'\t' read -r tag published_at; do
+    if [[ ! "$tag" =~ ^v?([A-Za-z0-9._+]+)$ ]]; then
+      echo "$repo release has an unusable tag: ${tag:-<empty>}" >&2
+      return 1
+    fi
+    pkgver=${BASH_REMATCH[1]}
+
+    if [[ -z "$published_at" ]] || ! published_epoch=$(date --date="$published_at" +%s 2>/dev/null); then
+      echo "$repo release $tag has an invalid published_at: ${published_at:-<empty>}" >&2
+      return 1
+    fi
+    candidates=$((candidates + 1))
+
+    if (( now - published_epoch < min_age )); then
+      if [[ "${BYPASS_MIN_RELEASE_AGE:-}" == "1" ]]; then
+        echo "Bypassing release-age gate for $repo $tag" >&2
+      else
+        continue
+      fi
+    fi
+
+    if [[ -z "$best_pkgver" ]] || [[ "$(vercmp "$pkgver" "$best_pkgver")" -gt 0 ]]; then
+      best_tag=$tag
+      best_pkgver=$pkgver
+      best_published_at=$published_at
+    fi
+  # `// ""` rather than `// empty`: empty would drop the field and shift the
+  # columns, so a malformed row could masquerade as a different one instead
+  # of tripping the per-field checks above.
+  done < <(jq -r '.[] | select((.draft or .prerelease) | not) | [.tag_name // "", .published_at // ""] | @tsv' <<<"$releases")
+
+  if (( candidates == 0 )); then
+    echo "no stable releases found in the feed for $repo" >&2
+    return 1
+  fi
+  if [[ -z "$best_tag" ]]; then
+    echo "every recent $repo release is still inside the release-age quarantine; skipping" >&2
+    echo '{}'
+    return 0
+  fi
+
+  # Already checked in: report no update instead of re-fetching checksums.
+  local current_pkgver
+  current_pkgver=$(grep -m1 '^pkgver=' "$package_dir/PKGBUILD" | cut -d= -f2- | tr -d "\"'")
+  if [[ "$best_pkgver" == "$current_pkgver" ]]; then
+    echo '{}'
+    return 0
+  fi
+
+  local checksums
+  if ! checksums=$(github_fetch_checksums "$repo" "$best_tag" "$checksums_name"); then
+    echo "could not fetch $checksums_name for $repo $best_tag" >&2
+    return 1
+  fi
+
+  local jq_args=(--arg pkgver "$best_pkgver" --arg published_at "$best_published_at")
+  local jq_filter='{pkgver: $pkgver, published_at: $published_at, sha256sums: {}}'
+  local arch template filename checksum
+  for arch in "${arches[@]}"; do
+    if [[ ! "$arch" =~ ^[a-z0-9_]+$ ]]; then
+      echo "invalid architecture key in upstream.assets: '$arch'" >&2
+      return 1
+    fi
+    template=$(jq -r --arg arch "$arch" '.upstream.assets[$arch]' "$metadata")
+    filename=${template//\{pkgver\}/$best_pkgver}
+    filename=${filename//\{tag\}/$best_tag}
+    # Manifest lines are "<sha256>  <name>", with the name sometimes prefixed
+    # "./" (sha256sum of a local path) or "*" (binary-mode marker).
+    checksum=$(awk -v f="$filename" '$2 == f || $2 == "./" f || $2 == "*" f { print $1; exit }' <<<"$checksums")
+    if [[ ! "$checksum" =~ ^[0-9a-f]{64}$ ]]; then
+      echo "no valid checksum for $filename in $repo $best_tag $checksums_name" >&2
+      return 1
+    fi
+    jq_args+=(--arg "sum_$arch" "$checksum")
+    jq_filter+=" | .sha256sums[\"$arch\"] = [\$sum_$arch]"
+  done
+
+  jq -n "${jq_args[@]}" "$jq_filter"
+}
diff --git a/pkgbuilds/mise-bin/.omarchy/package.json b/pkgbuilds/mise-bin/.omarchy/package.json
index db153c3..f90090e 100644
--- a/pkgbuilds/mise-bin/.omarchy/package.json
+++ b/pkgbuilds/mise-bin/.omarchy/package.json
@@ -1,4 +1,13 @@
 {
   "source": "local",
-  "release_ring": "fast"
+  "release_ring": "fast",
+  "min_release_age": "24h",
+  "upstream": {
+    "github": "jdx/mise",
+    "checksums": "SHASUMS256.txt",
+    "assets": {
+      "x86_64": "mise-{tag}-linux-x64.tar.xz",
+      "aarch64": "mise-{tag}-linux-arm64.tar.xz"
+    }
+  }
 }
diff --git a/pkgbuilds/mise-bin/.omarchy/upstream.sh b/pkgbuilds/mise-bin/.omarchy/upstream.sh
deleted file mode 100644
index 365063d..0000000
--- a/pkgbuilds/mise-bin/.omarchy/upstream.sh
+++ /dev/null
@@ -1,56 +0,0 @@
-#!/bin/bash
-set -euo pipefail
-
-repo="jdx/mise"
-release=$(curl -fsSL "https://api.github.com/repos/$repo/releases/latest")
-tag=$(jq -r '.tag_name // empty' <<<"$release")
-published_at=$(jq -r '.published_at // empty' <<<"$release")
-
-if [[ ! "$tag" =~ ^v([A-Za-z0-9._+]+)$ ]]; then
-  echo "Latest mise release has an invalid tag: ${tag:-<empty>}" >&2
-  exit 1
-fi
-
-if [[ -z "$published_at" ]] || ! published_epoch=$(date --date="$published_at" +%s); then
-  echo "Latest mise release has an invalid published_at: ${published_at:-<empty>}" >&2
-  exit 1
-fi
-
-# Keep a compromised mise release from reaching Omarchy before there has been
-# a full day for maintainers and the community to notice and pull it.
-minimum_release_age_seconds=$((24 * 60 * 60))
-now=$(date +%s)
-if (( now - published_epoch < minimum_release_age_seconds )); then
-  if [[ "${MISE_BIN_BYPASS_RELEASE_AGE:-}" == "1" ]]; then
-    echo "Bypassing mise release-age gate for $tag" >&2
-  else
-    echo '{}'
-    exit 0
-  fi
-fi
-
-pkgver=${BASH_REMATCH[1]}
-checksums=$(curl -fsSL \
-  "https://github.com/$repo/releases/download/$tag/SHASUMS256.txt")
-
-checksum_for() {
-  local filename=$1
-  local checksum
-  checksum=$(awk -v filename="./$filename" '$2 == filename { print $1 }' <<<"$checksums")
-
-  if [[ ! "$checksum" =~ ^[0-9a-f]{64}$ ]]; then
-    echo "No valid checksum found for $filename in $tag" >&2
-    exit 1
-  fi
-
-  echo "$checksum"
-}
-
-x86_64=$(checksum_for "mise-v${pkgver}-linux-x64.tar.xz")
-aarch64=$(checksum_for "mise-v${pkgver}-linux-arm64.tar.xz")
-
-jq -n \
-  --arg pkgver "$pkgver" \
-  --arg x86_64 "$x86_64" \
-  --arg aarch64 "$aarch64" \
-  '{pkgver: $pkgver, sha256sums: {x86_64: [$x86_64], aarch64: [$aarch64]}}'