dep_freshness: upstream: allowlist predicate for forks; Google API clients judged inside their generation

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

dep_freshness/_tables.py

@@ -195,3 +195,9 @@ ALLOWLIST_FILE: Final = "dependency-freshness.allowlist.yaml"
 SHARED_ALLOWLIST_ENV: Final = "DEP_FRESHNESS_SHARED_ALLOWLIST"
 ALLOWLIST_MAX_DAYS: Final = 90
 TRANSITIVE_PREFIX: Final = "transitive:"
+# A fork's predicate: the entry holds only while the upstream repository's own
+# copy of the same manifest pins the same version, and dies the day upstream
+# bumps. TachiyomiSY cannot take moko-resources 0.27.0 (a 300-file accessor
+# rewrite that breaks every future upstream string) before jobobby04 does.
+UPSTREAM_PREFIX: Final = "upstream:"
+GITHUB_RAW: Final = "https://raw.githubusercontent.com/{repo}/HEAD/{path}"

dep_freshness/allowlist.py

@@ -6,6 +6,9 @@ Two entry classes, and the distinction is the whole point:
   re-evaluated every run and the entry clears itself when upstream moves. It
   never expires on a calendar, because a date nobody can act on turns the gate
   red for a reason no commit can fix.
+* `blocked_by: upstream:<owner>/<repo>` is the fork's predicate: it holds
+  while that repository's copy of the same manifest pins the same version
+  (`upstream.py`), and dies the day upstream bumps.
 * anything else is **discretionary**: it needs `expires`, capped at 90 days,
   and fails once past.
 
@@ -15,13 +18,12 @@ allowlist that rots silently is a suppression, not an exception.
 
 from __future__ import annotations
 
+import os
 from datetime import date, datetime
 from pathlib import Path
 
 import yaml
 
-import os
-
 from dep_freshness._tables import (
     ALLOWLIST_FILE,
     ALLOWLIST_MAX_DAYS,
@@ -79,17 +81,19 @@ def _entry(raw: object, source: Path, position: int) -> Exception_:
         expires=(str(raw["expires"]).strip() if raw.get("expires") else None),
         source=source,
     )
-    if entry.transitive:
+    if entry.predicate:
         if entry.expires:
             raise AllowlistError(
-                f"{where}: a transitive: entry must NOT set expires -- it clears "
+                f"{where}: a predicate entry must NOT set expires -- it clears "
                 "itself when the blocker lifts, and a date nobody can act on "
                 "only turns the gate red for no actionable reason"
             )
-        if not entry.blocker or not all(entry.blocker):
+        if entry.transitive and (not entry.blocker or not all(entry.blocker)):
             raise AllowlistError(
                 f"{where}: blocked_by must read transitive:<package>@<version>"
             )
+        if entry.upstream and len((entry.upstream_repo or "").split("/")) != 2:
+            raise AllowlistError(f"{where}: blocked_by must read upstream:<owner>/<repo>")
         return entry
     if not entry.expires:
         raise AllowlistError(f"{where}: a discretionary entry requires expires")
@@ -98,7 +102,7 @@ def _entry(raw: object, source: Path, position: int) -> Exception_:
 
 def check_expiry(entry: Exception_, today: date | None = None) -> None:
     """Raise if a discretionary entry is past due or reaches too far out."""
-    if entry.transitive or not entry.expires:
+    if entry.predicate or not entry.expires:
         return
     now = today or date.today()
     when = _parse_date(entry.expires, f"{entry.source}: {entry.package}")

dep_freshness/check.py

@@ -27,7 +27,9 @@ from dep_freshness.evaluate import judge
 from dep_freshness.models import Finding, Severity
 from dep_freshness.quarantine import installable_latest
 from dep_freshness.registries import http
+from dep_freshness.registries.http import Offline
 from dep_freshness.resolve import Answer, Resolver
+from dep_freshness.upstream import still_pins
 
 
 def repo_root(start: Path) -> Path:
@@ -45,8 +47,9 @@ def repo_root(start: Path) -> Path:
 
 def _excuse(
     findings: list[Finding], entries, shared: Path | None = None,
-    whole_repo: bool = True,
+    whole_repo: bool = True, root: Path | None = None,
-) -> tuple[list[Finding], list]:
+    degraded: list[str] | None = None,
+) -> tuple[list[Finding], list, dict[str, bool]]:
     """Split findings into (still failing, excused), and flag dead entries.
 
     A `transitive:` entry clears itself the moment its dependency is no longer
@@ -68,6 +71,7 @@ def _excuse(
     """
     by_label = {f"{e.ecosystem}:{e.package}": e for e in entries}
     used: set[str] = set()
+    blocking: dict[str, bool] = {}
     failing: list[Finding] = []
     excused: list[Finding] = []
     for finding in findings:
@@ -76,9 +80,18 @@ def _excuse(
             used.add(finding.label)  # the entry applies here, even if it
             # does not excuse this particular pin -- that is a stale pin to
             # fix, not allowlist rot to delete.
+            blocking[finding.label] = True
         if entry is None or not _covers(entry, finding):
             failing.append(finding)
             continue
+        if entry.upstream and not _upstream_holds(entry, finding, root, degraded):
+            blocking[finding.label] = False
+            failing.append(Finding(
+                finding.dep, finding.severity, finding.latest,
+                f"{entry.upstream_repo} no longer pins {entry.pinned}: drop the "
+                "allowlist entry and take the bump",
+            ))
+            continue
         excused.append(Finding(
             finding.dep, finding.severity, finding.latest, finding.detail,
             excused=entry.reason,
@@ -89,7 +102,17 @@ def _excuse(
         and f"{e.ecosystem}:{e.package}" not in used
         and (shared is None or e.source != shared)
     ]
-    return failing, dead
+    return failing, dead, blocking
+
+
+def _upstream_holds(entry, finding: Finding, root, degraded) -> bool:
+    """Offline, an `upstream:` entry is trusted and the run is marked degraded."""
+    try:
+        return still_pins(entry, finding, root or Path.cwd())
+    except Offline as exc:
+        if degraded is not None:
+            degraded.append(f"{entry.blocked_by} unverified: {exc}")
+        return True
 
 
 def _covers(entry, finding: Finding) -> bool:
@@ -187,13 +210,11 @@ def main(argv: list[str] | None = None) -> int:
     resolver = Resolver(refresh=args.refresh)
     findings = collect(_targets(args, root), resolver)
     shared = shared_path()
-    failing, dead = _excuse(
+    failing, dead, still_blocking = _excuse(
         findings, entries,
         shared=None if root == shared.parent else shared,
-        whole_repo=args.all,
+        whole_repo=args.all, root=root, degraded=resolver.degraded,
     )
-
-    still_blocking = {f.label: True for f in findings}
     report.exceptions_block(entries, still_blocking)
 
     unknown = [f for f in failing if f.severity is Severity.UNKNOWN]

dep_freshness/evaluate.py

@@ -19,7 +19,7 @@ from dep_freshness._tables import GITCOMMIT, MATRIX, TOOLCHAIN
 from dep_freshness.constraints import lower_bound, satisfies
 from dep_freshness.models import Dep, Finding, Severity
 from dep_freshness.resolve import Answer
-from dep_freshness.versions import behind
+from dep_freshness.versions import behind, google_api_key
 
 # What JitPack accepts as a version, and what a bump pastes into the catalog.
 _SHORT_SHA = 10
@@ -46,6 +46,24 @@ def _commit(dep: Dep, heads: str) -> Finding | None:
     )
 
 
+def _generation(dep: Dep, pin, latest: str) -> Finding | None:
+    """A Google API client is judged inside its own generation only."""
+    gen, rank = pin
+    for candidate in latest.split():
+        key = google_api_key(candidate)
+        if key is None or key[0] != gen:
+            continue
+        if key[1] > rank:
+            return Finding(dep, Severity.STALE, candidate)
+        return None
+    return Finding(
+        dep,
+        Severity.UNKNOWN,
+        None,
+        detail=f"the registry has no {gen} generation of this client any more",
+    )
+
+
 def _toolchain(dep: Dep, latest: str) -> Finding | None:
     if dep.pinned:
         if behind(dep.pinned, latest):
@@ -112,6 +130,9 @@ def judge(dep: Dep, answer: Answer) -> Finding | None:
         return _toolchain(dep, latest)
     if dep.ecosystem == GITCOMMIT:
         return _commit(dep, latest)
+    pin = google_api_key(dep.pinned or "")
+    if pin is not None:
+        return _generation(dep, pin, latest)
 
     if dep.peer:
         # A peerDependency declares what a CONSUMER may bring, so exact-pinning

dep_freshness/models.py

@@ -76,11 +76,32 @@ class Exception_:
 
     @property
     def transitive(self) -> bool:
-        """True when this is a predicate entry that never expires on a date."""
+        """True when a named transitive dependency is what holds the pin."""
         from dep_freshness._tables import TRANSITIVE_PREFIX
 
         return self.blocked_by.startswith(TRANSITIVE_PREFIX)
 
+    @property
+    def upstream(self) -> bool:
+        """True when the fork's upstream still pinning this version holds it."""
+        from dep_freshness._tables import UPSTREAM_PREFIX
+
+        return self.blocked_by.startswith(UPSTREAM_PREFIX)
+
+    @property
+    def predicate(self) -> bool:
+        """True for either self-clearing class; False means a calendar expiry."""
+        return self.transitive or self.upstream
+
+    @property
+    def upstream_repo(self) -> str | None:
+        """`owner/repo` of the upstream an `upstream:` entry names."""
+        from dep_freshness._tables import UPSTREAM_PREFIX
+
+        if not self.upstream:
+            return None
+        return self.blocked_by[len(UPSTREAM_PREFIX):].strip()
+
     @property
     def blocker(self) -> tuple[str, str] | None:
         """`(package, version)` this entry claims is holding the pin back."""

dep_freshness/registries/maven.py

@@ -13,7 +13,9 @@ layer.
 through `newest_stable` like every other ecosystem. Only when NO repository
 has a stable release at all does the newest pre-release become the reference
 (`versions.reference`), which is how `androidx.biometric:biometric-ktx`,
-alpha-only since 2021, gets a checkable answer.
+alpha-only since 2021, gets a checkable answer. Google's API clients
+(`v3-rev20260901-2.0.0`) are neither: for those the answer is the newest
+revision of every generation, and the judge picks the pin's own.
 """
 
 from __future__ import annotations
@@ -22,7 +24,7 @@ from xml.etree import ElementTree
 
 from dep_freshness._tables import MAVEN_REPOS
 from dep_freshness.registries.http import get_text
-from dep_freshness.versions import newest_stable, reference
+from dep_freshness.versions import newest_per_generation, newest_stable, reference
 
 
 def metadata_url(repo: str, name: str) -> str | None:
@@ -60,4 +62,4 @@ def latest(name: str) -> str | None:
         if stable is not None:
             return stable
         seen.extend(versions)
-    return reference(seen)
+    return reference(seen) or newest_per_generation(seen)

dep_freshness/report.py

@@ -7,13 +7,14 @@ allowlist is that every not-latest pin stays visible.
 
 from __future__ import annotations
 
-from datetime import date, datetime
 import json
-from pathlib import Path
 import sys
+from datetime import date, datetime
+from pathlib import Path
 
 from dep_freshness.models import Exception_, Finding, Severity
 
+
 def _err(stream):
     """Resolve stderr at call time.
 
@@ -58,7 +59,7 @@ def exceptions_block(
     print(f"\n⚠️  DEPENDENCY EXCEPTION IN USE — {len(entries)} active", file=stream)
     for entry in entries:
         print(f"  {entry.package} {entry.pinned} ({entry.ecosystem})", file=stream)
-        if entry.transitive:
+        if entry.predicate:
             state = "still blocking" if still_blocking.get(
                 f"{entry.ecosystem}:{entry.package}", True) else "CLEARED"
             print(f"    blocked_by: {entry.blocked_by}  [{state}]", file=stream)
@@ -76,7 +77,7 @@ def machine_lines(entries: list[Exception_]) -> list[str]:
         head = (f"[DEP-EXCEPTION] {entry.ecosystem}:{entry.package} {entry.pinned}")
         if entry.latest_known:
             head += f" < {entry.latest_known}"
-        if entry.transitive:
+        if entry.predicate:
             out.append(f"{head} blocked_by={entry.blocked_by} [still blocking]")
         else:
             left = _days_left(entry.expires or "")
@@ -107,7 +108,7 @@ def violations(findings: list[Finding], root: Path, stream=None) -> None:
             )
             if finding.detail:
                 print(f"        {finding.detail}", file=stream)
-        print("", file=stream)
+        print(file=stream)
     print(
         "Bump them to latest stable, or record an exception in "
         "dependency-freshness.allowlist.yaml with reason + blocked_by.",

dep_freshness/tests/test_google_api.py

@@ -0,0 +1,74 @@
+"""Google API clients: `v3-rev20260901-2.0.0` is ordered inside its generation.
+
+The fail-green case: read loosely, every `v3-rev...` is "3", and a 2019 pin
+compares equal to a 2026 revision. The fail-red case: `v2-...-2.0.0` read as
+newer than `v3-...-1.25.0` because 2.0.0 > 1.25.0.
+"""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+from dep_freshness.evaluate import judge
+from dep_freshness.models import Dep, Severity
+from dep_freshness.registries import maven
+from dep_freshness.resolve import Answer
+from dep_freshness.tests.test_gradle_registry import CENTRAL, metadata
+from dep_freshness.versions import exact_pin, google_api_key, newest_per_generation
+
+V3_OLD = "v3-rev197-1.25.0"
+V3_NEW = "v3-rev20260901-2.0.0"
+V2 = "v2-rev20220709-2.0.0"
+
+
+def test_the_key_is_generation_then_library_then_revision():
+    assert google_api_key(V3_NEW)[0] == "v3"
+    assert google_api_key(V3_NEW)[1] > google_api_key(V3_OLD)[1]
+    assert google_api_key("v3-rev20260901-1.9.0")[1] < google_api_key(V3_OLD)[1]
+    assert google_api_key("2.0.0") is None
+    assert google_api_key("v3-rev197") is None
+
+
+def test_newest_per_generation_keeps_every_generation():
+    assert (
+        newest_per_generation([V3_OLD, V2, V3_NEW, "junk", None, ""])
+        == f"{V2} {V3_NEW}"
+    )
+    assert newest_per_generation(["1.0.0"]) is None
+    # An older revision met AFTER the newest must not displace it.
+    assert newest_per_generation([V3_NEW, V3_OLD]) == V3_NEW
+
+
+def test_the_pin_keeps_its_generation_prefix():
+    assert exact_pin(V3_OLD) == V3_OLD
+
+
+def test_the_registry_answers_per_generation_when_nothing_else_parses(monkeypatch):
+    name = "com.google.apis:google-api-services-drive"
+    table = {maven.metadata_url(CENTRAL, name): metadata(V3_OLD, V2, V3_NEW)}
+    monkeypatch.setattr(maven, "get_text", lambda url, *a, **k: table.get(url))
+    assert maven.latest(name) == f"{V2} {V3_NEW}"
+
+
+def dep(pinned: str = V3_OLD) -> Dep:
+    return Dep(
+        ecosystem="maven",
+        name="com.google.apis:google-api-services-drive",
+        constraint=pinned,
+        path=Path("libs.versions.toml"),
+        line=1,
+        pinned=pinned,
+    )
+
+
+def test_a_pin_is_judged_inside_its_own_generation_only():
+    finding = judge(dep(), Answer(f"{V2} {V3_NEW}"))
+    assert finding.severity is Severity.STALE
+    assert finding.latest == V3_NEW
+    assert judge(dep(V3_NEW), Answer(f"{V2} {V3_NEW}")) is None
+
+
+def test_a_generation_the_registry_dropped_is_unknown_not_a_pass():
+    finding = judge(dep(), Answer(V2))
+    assert finding.severity is Severity.UNKNOWN
+    assert "v3 generation" in finding.detail

dep_freshness/tests/test_upstream.py

@@ -0,0 +1,160 @@
+"""The `upstream:` predicate: an entry holds while the fork's upstream agrees.
+
+The rot case is the one that matters: the day upstream bumps, the entry must
+die loudly rather than keep excusing a pin nobody is waiting on any more.
+"""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+import pytest
+
+from dep_freshness import upstream
+from dep_freshness.allowlist import AllowlistError, load
+from dep_freshness.models import Dep, Exception_, Finding, Severity
+from dep_freshness.registries.http import Offline
+from dep_freshness.report import exceptions_block, machine_lines
+from dep_freshness.tests.conftest import ALLOWLIST, STALE_PUBSPEC, write
+
+UPSTREAM_ENTRY = """\
+exceptions:
+  - ecosystem: pub
+    package: http
+    pinned: "1.5.0"
+    reason: "the project we fork from is still on 1.5.0"
+    blocked_by: "upstream:someone/demo"
+"""
+
+
+def entry(**kwargs) -> Exception_:
+    base = {
+        "ecosystem": "pub",
+        "package": "http",
+        "pinned": "1.5.0",
+        "reason": "r",
+        "blocked_by": "upstream:someone/demo",
+    }
+    return Exception_(**{**base, **kwargs})
+
+
+def finding(root: Path, path: str = "pubspec.yaml") -> Finding:
+    dep = Dep(
+        ecosystem="pub",
+        name="http",
+        constraint="1.5.0",
+        path=root / path,
+        line=5,
+        pinned="1.5.0",
+    )
+    return Finding(dep, Severity.STALE, "1.6.0")
+
+
+@pytest.fixture
+def raw(monkeypatch):
+    """Canned bodies per raw.githubusercontent URL; anything else is a 404."""
+    table: dict[str, str] = {}
+    monkeypatch.setattr(upstream, "get_text", lambda url, *a, **k: table.get(url))
+    return table
+
+
+URL = "https://raw.githubusercontent.com/someone/demo/HEAD/pubspec.yaml"
+
+
+def test_the_upstream_manifest_is_fetched_at_the_same_relative_path(raw, tmp_path):
+    raw[URL] = STALE_PUBSPEC
+    assert upstream.upstream_pin(entry(), finding(tmp_path), tmp_path) == "1.5.0"
+    assert upstream.still_pins(entry(), finding(tmp_path), tmp_path)
+
+
+def test_upstream_having_moved_on_clears_the_entry(raw, tmp_path):
+    raw[URL] = STALE_PUBSPEC.replace("1.5.0", "1.6.0")
+    assert not upstream.still_pins(entry(), finding(tmp_path), tmp_path)
+
+
+def test_no_upstream_manifest_or_no_such_package_is_no_pin(raw, tmp_path):
+    assert upstream.upstream_pin(entry(), finding(tmp_path), tmp_path) is None
+    raw[URL] = "name: demo\ndependencies:\n  other: 1.0.0\n"
+    assert upstream.upstream_pin(entry(), finding(tmp_path), tmp_path) is None
+
+
+def test_a_manifest_outside_the_repo_is_no_pin(raw, tmp_path):
+    outside = finding(tmp_path.parent, "elsewhere/pubspec.yaml")
+    assert upstream.upstream_pin(entry(), outside, tmp_path / "repo") is None
+
+
+def test_offline_propagates_from_the_transport(monkeypatch, tmp_path):
+    def down(*_a, **_k):
+        raise Offline("down")
+
+    monkeypatch.setattr(upstream, "get_text", down)
+    with pytest.raises(Offline):
+        upstream.still_pins(entry(), finding(tmp_path), tmp_path)
+
+
+def test_an_upstream_entry_parses_and_may_not_carry_an_expiry(tmp_path):
+    write(tmp_path, ALLOWLIST, UPSTREAM_ENTRY)
+    parsed = load(tmp_path)[0]
+    assert parsed.upstream and parsed.predicate and not parsed.transitive
+    assert parsed.upstream_repo == "someone/demo"
+    assert parsed.blocker is None
+    write(tmp_path, ALLOWLIST, UPSTREAM_ENTRY + '    expires: "2099-01-01"\n')
+    with pytest.raises(AllowlistError, match="must NOT set expires"):
+        load(tmp_path)
+
+
+def test_an_upstream_entry_must_name_owner_slash_repo(tmp_path):
+    write(tmp_path, ALLOWLIST, UPSTREAM_ENTRY.replace("someone/demo", "demo"))
+    with pytest.raises(AllowlistError, match="upstream:<owner>/<repo>"):
+        load(tmp_path)
+
+
+def test_the_report_treats_it_as_a_predicate(capsys):
+    exceptions_block([entry()], {"pub:http": False})
+    assert "CLEARED" in capsys.readouterr().err
+    assert "[still blocking]" in machine_lines([entry()])[0]
+
+
+def test_end_to_end_the_entry_excuses_while_upstream_agrees(repo, run, raw):
+    raw[URL] = STALE_PUBSPEC
+    write(repo, "pubspec.yaml", STALE_PUBSPEC)
+    write(repo, ALLOWLIST, UPSTREAM_ENTRY)
+    assert run("--all", "--strict") == 0
+
+
+def test_end_to_end_upstream_moving_on_fails_the_pin(repo, run, raw, capsys):
+    raw[URL] = STALE_PUBSPEC.replace("1.5.0", "1.6.0")
+    write(repo, "pubspec.yaml", STALE_PUBSPEC)
+    write(repo, ALLOWLIST, UPSTREAM_ENTRY)
+    assert run("--all", "--strict") == 1
+    err = capsys.readouterr().err
+    assert "no longer pins 1.5.0" in err
+    assert "CLEARED" in err
+
+
+def test_end_to_end_offline_trusts_the_entry_but_degrades(
+    repo, run, monkeypatch, capsys
+):
+    def down(*_a, **_k):
+        raise Offline("down")
+
+    monkeypatch.setattr(upstream, "get_text", down)
+    write(repo, "pubspec.yaml", STALE_PUBSPEC)
+    write(repo, ALLOWLIST, UPSTREAM_ENTRY)
+    assert run("--all") == 0
+    assert "upstream:someone/demo unverified" in capsys.readouterr().err
+    assert run("--all", "--strict") == 3
+
+
+def test_a_transitive_entry_has_no_upstream_repo():
+    assert entry(blocked_by="transitive:x@1.0.0").upstream_repo is None
+
+
+def test_offline_without_a_degraded_list_still_trusts_the_entry(monkeypatch, tmp_path):
+    from dep_freshness.check import _upstream_holds
+
+    def down(*_a, **_k):
+        raise Offline("down")
+
+    monkeypatch.setattr(upstream, "get_text", down)
+    assert _upstream_holds(entry(), finding(tmp_path), tmp_path, None)

dep_freshness/upstream.py

@@ -0,0 +1,48 @@
+"""The `upstream:` predicate: does the fork's upstream still pin this version?
+
+A fork cannot always take a release before the project it tracks does --
+moko-resources 0.27.0 rewrites every string accessor across 300 files of
+TachiyomiSY and would break each future upstream commit that adds a string.
+"Wait for upstream" is the honest reason, and it is checkable: fetch the
+upstream repository's copy of the SAME manifest, parse it with the same
+parser, and compare the pin. Equal means the entry holds; different means
+upstream moved and the entry is dead, which exits 2 like every other rotten
+allowlist entry.
+"""
+
+from __future__ import annotations
+
+import tempfile
+from pathlib import Path
+
+from dep_freshness._tables import GITHUB_RAW
+from dep_freshness.discover import parse_manifest
+from dep_freshness.models import Exception_, Finding
+from dep_freshness.registries.http import get_text
+
+
+def upstream_pin(entry: Exception_, finding: Finding, root: Path) -> str | None:
+    """What `entry.upstream_repo` pins for this package in the same manifest.
+
+    None when upstream has no such manifest or does not declare the package;
+    `Offline` propagates from the transport so the caller can degrade.
+    """
+    try:
+        relative = finding.dep.path.resolve().relative_to(root.resolve())
+    except ValueError:
+        return None
+    body = get_text(GITHUB_RAW.format(repo=entry.upstream_repo, path=relative.as_posix()))
+    if body is None:
+        return None
+    with tempfile.TemporaryDirectory() as scratch:
+        copy = Path(scratch) / finding.dep.path.name
+        copy.write_text(body, encoding="utf-8")
+        for dep in parse_manifest(copy):
+            if dep.ecosystem == finding.dep.ecosystem and dep.name == finding.dep.name:
+                return dep.pinned or dep.constraint
+    return None
+
+
+def still_pins(entry: Exception_, finding: Finding, root: Path) -> bool:
+    """True while upstream pins exactly the version the entry excuses."""
+    return upstream_pin(entry, finding, root) == entry.pinned

dep_freshness/versions.py

@@ -73,6 +73,8 @@ def is_prerelease(raw: str) -> bool:
 
 
 def _canonical(raw: str) -> str:
+    if GOOGLE_API.match(raw.strip()):
+        return raw.strip()  # the leading `v` is the API generation, not noise
     prefix, tail = split_tag_prefix(raw)
     return prefix + tail.lstrip("v")
 
@@ -112,6 +114,35 @@ def reference(candidates) -> str | None:
     return newest_stable(candidates) or _newest(candidates, prereleases=True)
 
 
+# Google's API clients: `v3-rev20260901-2.0.0` is generation v3 of the API,
+# revision 20260901 of the discovery document, built on library 2.0.0. No
+# ordering across generations exists (v2 and v3 are different APIs), so the
+# registry answers with the newest revision of EVERY generation and the
+# judge picks the pin's own.
+GOOGLE_API = re.compile(r"^(?P<gen>v\d+)-rev(?P<rev>\d+)-(?P<lib>\d+(?:\.\d+)*)$")
+
+
+def google_api_key(raw: str) -> tuple[str, tuple[Version, int]] | None:
+    """`("v3", (Version("2.0.0"), 20260901))` for a Google API client version."""
+    match = GOOGLE_API.match(raw.strip())
+    if not match:
+        return None
+    return (match.group("gen"), (Version(match.group("lib")), int(match.group("rev"))))
+
+
+def newest_per_generation(candidates) -> str | None:
+    """Space-joined newest Google API client per generation, or None."""
+    best: dict[str, tuple[tuple[Version, int], str]] = {}
+    for raw in candidates:
+        key = google_api_key(raw or "")
+        if key is None:
+            continue
+        gen, rank = key
+        if gen not in best or rank > best[gen][0]:
+            best[gen] = (rank, raw.strip())
+    return " ".join(best[gen][1] for gen in sorted(best)) or None
+
+
 def behind(pinned: str, latest: str) -> bool:
     """True when `pinned` is strictly older than `latest`.