diff --git a/AGENTS.md b/AGENTS.md
index a8aff0c..06ad309 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -8,11 +8,16 @@ Six documentation checkers, packaged so that a MkDocs documentation repository
 can pin them and get the identical code in CI and on a developer's machine. The
 checkers were extracted from `hatlabs/halpi2`, where they lived as `scripts/`.
 
-Intended consumers. Neither pins the package yet; both migrations are still
-open, so `hatlabs/halpi2` still runs its own copies under `scripts/`:
+Consumers, all pinning a tag:
 
-- `hatlabs/halpi2` — nine locales, full translation gate
-- `halos-org/docs.halos.fi` — no translations, anchor validation only
+- `hatlabs/halpi2`, `hatlabs/halmet`, `hatlabs/sh-rpi` — nine locales each, full
+  translation gate through `halos-org/shared-workflows`
+- `hatlabs/sh-esp32` — one locale, same gate
+- `halos-org/docs` (docs.halos.fi) — no translations, `check-anchors` only,
+  called directly from its own build job
+
+`halos-org/shared-workflows` calls the CLI by name and by flag, so it is a
+consumer too even though it installs nothing: see `translation-status.yml`.
 
 ## The six commands
 
@@ -32,6 +37,12 @@ Each module lives at `src/halos_docs_tools/<name>.py` and exposes `main()`.
   Where a checker needs them, the path is a CLI option with a default.
 - The translation stamp format — `translated_from` in frontmatter, holding a git
   blob hash — is fixed. Consumers have thousands of pages carrying it.
+- `translation-status --check` fails on `missing`, `unstamped` and `orphaned`
+  wherever they came from, and on `stale` only for pages changed since
+  `--since REF` when that is given. The split is deliberate: the first three are
+  structural, while gating every stale page in the repository makes an
+  English-only edit unmergeable until all its translations land in the same
+  change. Do not quietly widen either half.
 
 ## Distribution
 
diff --git a/README.md b/README.md
index 750f2c8..ba66f23 100644
--- a/README.md
+++ b/README.md
@@ -46,7 +46,7 @@ A workflow branches on these, so they are part of the interface.
 |:---|:---|
 | 0 | the check passed |
 | 1 | the check found problems — broken anchors, unused glossary terms, typography faults, or (with `--check`) translations that are not current |
-| 2 | the check could not run: `check-anchors` was given a site directory holding no built pages |
+| 2 | the check could not run, so a pass would prove nothing: `check-anchors` was given a site directory holding no built pages, or `translation-status` found no configured locales, no source pages, markdown outside every configured locale, or a `--since` ref it could not resolve |
 
 Glossaries and per-language rules stay in the documentation repository. This
 package brings the checkers, not the terminology.
@@ -97,9 +97,30 @@ exits non-zero when any page in any configured locale is anything but
 `current`, and names every entry responsible. Without `--check` the command
 only reports, whatever it finds.
 
-The gate is a property of the repository, not of a pull request's diff, so
 `--only-pages` narrows the report and never the rule.
 
+### Gating on the staleness this change caused
+
+```
+translation-status --check --since origin/main
+```
+
+Whole-repository `--check` has a cost that shows up the first time someone
+fixes a typo: editing one English page marks every translation of it stale, so
+the change cannot go green until all of them land in the same pull request. And
+a page somebody left behind last month fails a pull request that touched no
+documentation at all.
+
+`--since REF` gates on `stale` only for English pages whose content differs
+from `REF`. `missing`, `unstamped` and `orphaned` still fail wherever they came
+from — those are structural, and none of them asks an author for translation
+work their change did not create.
+
+What it passed over is printed, so a green run is not mistaken for a clean
+repository. If `REF` does not resolve — an unknown ref, or a clone too shallow
+to hold it — the command exits 2 rather than forgiving everything it could not
+measure.
+
 One consequence is worth knowing before you meet it: adding a locale to
 `mkdocs.yml` makes every page `missing` in that locale immediately. A new
 locale therefore arrives in a single pull request, together with its pages.
diff --git a/pyproject.toml b/pyproject.toml
index 1984e57..bb958ba 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "halos-docs-tools"
-version = "0.1.0"
+version = "0.2.0"
 description = "Documentation checkers for HaLOS and Hat Labs MkDocs sites"
 readme = "README.md"
 requires-python = ">=3.11"
diff --git a/src/halos_docs_tools/translation_status.py b/src/halos_docs_tools/translation_status.py
index b43cb72..3f85181 100644
--- a/src/halos_docs_tools/translation_status.py
+++ b/src/halos_docs_tools/translation_status.py
@@ -12,8 +12,13 @@
 it report as stale on its own.
 
 Reports by default. With --check it also fails: any page that is not current,
-in any configured locale, exits non-zero. That is a property of the repository,
-so the gate ignores --only-pages, which narrows the report and not the rule.
+in any configured locale, exits non-zero. --only-pages narrows the report and
+never the rule.
+
+--since REF narrows the rule, and only for stale: it fails on the pages this
+change made stale rather than on every stale page in the repository. Missing,
+unstamped and orphaned stay absolute. Without it, editing one English page
+cannot go green until every translation of it lands in the same change.
 """
 
 from __future__ import annotations
@@ -282,6 +287,53 @@ def render_comment(entries: list[Entry]) -> str:
     )
 
 
+def changed_sources(ref: str, default: str) -> set[str] | None:
+    """English pages differing from `ref`, relative to the language directory.
+
+    None when the diff could not be computed -- an unknown ref, or a clone too
+    shallow to contain it. The caller must not read that as "nothing changed":
+    a gate that forgives every stale page because it could not tell which ones
+    this change touched forgives the whole repository.
+    """
+    root = DOCS / default
+    result = subprocess.run(
+        ["git", "diff", "--name-only", ref, "--", str(root)],
+        capture_output=True,
+        text=True,
+    )
+    if result.returncode != 0:
+        return None
+    changed = set()
+    for line in result.stdout.splitlines():
+        try:
+            changed.add(str(Path(line).relative_to(root)))
+        except ValueError:
+            continue
+    return changed
+
+
+def render_excused(excused: list[Entry], ref: str) -> str:
+    """Say what the gate passed over, so a green run is not read as a clean one."""
+    pages = sorted({e.page for e in excused})
+    translations = f"{len(excused)} stale translation" + (
+        "s" if len(excused) > 1 else ""
+    )
+    of_pages = f"{len(pages)} page" + ("s" if len(pages) > 1 else "")
+    out = [
+        "",
+        f"{translations} of {of_pages} were already stale at {ref} and were "
+        "not gated on:",
+        "",
+    ]
+    out += [f"  {page}" for page in pages]
+    out += [
+        "",
+        "They are still in the report above, and still block whichever change "
+        "edits their English source next.",
+    ]
+    return "\n".join(out)
+
+
 def render_failure(behind: list[Entry]) -> str:
     """Name every entry the gate is failing on.
 
@@ -331,8 +383,22 @@ def main(argv: list[str] | None = None) -> int:
         help="exit non-zero when any translation is stale, missing, unstamped "
         "or orphaned, across the whole repository",
     )
+    parser.add_argument(
+        "--since",
+        metavar="REF",
+        help="gate on stale translations only for English pages that changed "
+        "since REF. Missing, unstamped and orphaned still fail whatever "
+        "change introduced them",
+    )
     args = parser.parse_args(argv)
 
+    if args.since and not (args.check or args.comment):
+        print(
+            "--since narrows what counts as a gate failure, so it needs "
+            "--check or --comment. The plain report shows everything by design."
+        )
+        return 2
+
     default, languages = configured_languages()
     if not languages:
         print("No translation languages configured.")
@@ -341,8 +407,29 @@ def main(argv: list[str] | None = None) -> int:
         return 2 if args.check else 0
 
     entries = collect(default, languages, want_diff=args.diff or args.comment)
+
+    # Resolved before anything is rendered. The comment body is the verdict, so
+    # it has to be built from what the gate will actually fail on -- naming a
+    # page the run passed on sends its author to translate something nobody
+    # asked them for.
+    excused: list[Entry] = []
+    if args.since:
+        changed = changed_sources(args.since, default)
+        if changed is None:
+            print(
+                f"\nCannot diff against '{args.since}'. The gate was asked to "
+                "fail only on what this change made stale, and it cannot tell "
+                "what that is.\n\nCheck the ref exists in this clone -- a "
+                "shallow checkout is the usual cause."
+            )
+            return 2
+        excused = [e for e in entries if e.state == "stale" and e.page not in changed]
+    spared = {(e.language, e.page) for e in excused}
+
     if args.comment:
-        print(render_comment(entries))
+        print(
+            render_comment([e for e in entries if (e.language, e.page) not in spared])
+        )
     elif args.format == "markdown":
         only = set(args.only_pages) if args.only_pages else None
         print(render_markdown(entries, only))
@@ -374,7 +461,17 @@ def main(argv: list[str] | None = None) -> int:
             )
             return 2
 
-        behind = [e for e in entries if e.state != "current"]
+        behind = [
+            e
+            for e in entries
+            if e.state != "current" and (e.language, e.page) not in spared
+        ]
+
+        # Not in comment mode: there stdout is the comment body, and what the
+        # gate spared belongs in the report rather than in a verdict.
+        if excused and not args.comment:
+            print(render_excused(excused, args.since))
+
         if behind:
             print(render_failure(behind))
             return 1
diff --git a/tests/test_translation_gate_since.py b/tests/test_translation_gate_since.py
new file mode 100644
index 0000000..4051bd1
--- /dev/null
+++ b/tests/test_translation_gate_since.py
@@ -0,0 +1,140 @@
+"""--since: gate on the staleness this change caused, not the repository's.
+
+Without it the gate reads the whole repository, so one edit to an English page
+cannot go green without every translation of it in the same change, and a page
+someone left behind last month reddens a pull request that touched no
+documentation at all.
+
+--since narrows *stale* to the English pages that changed against a ref.
+missing, unstamped and orphaned stay absolute: they are structural, and none of
+them asks the author for translation work their change did not create.
+"""
+
+from __future__ import annotations
+
+from conftest import DocsRepo
+
+from halos_docs_tools import translation_status
+
+
+def run(*argv: str) -> int:
+    return translation_status.main(list(argv))
+
+
+def test_a_page_this_change_did_not_touch_does_not_fail(docs_repo: DocsRepo):
+    docs_repo.source("other.md")
+    docs_repo.translation("fi", "other.md")
+    docs_repo.translation("sv", "other.md")
+    base = docs_repo.commit()
+
+    # Someone else's page went stale earlier; this change edits nothing.
+    docs_repo.source("other.md", "# Title\n\nEdited without translating.\n")
+    docs_repo.commit()
+    stale_base = docs_repo.git("rev-parse", "HEAD")
+
+    docs_repo.write("unrelated.txt", "not documentation\n")
+
+    assert run("--check") == 1
+    assert run("--check", "--since", stale_base) == 0
+    assert base  # the earlier state is what stale_base was measured against
+
+
+def test_a_page_this_change_edited_still_fails(docs_repo: DocsRepo):
+    base = docs_repo.commit()
+    docs_repo.source("index.md", "# Title\n\nEdited in this change.\n")
+
+    assert run("--check", "--since", base) == 1
+
+
+def test_a_missing_translation_fails_however_old(docs_repo: DocsRepo):
+    docs_repo.source("lonely.md")
+    base = docs_repo.commit()
+    docs_repo.write("unrelated.txt", "not documentation\n")
+
+    assert run("--check", "--since", base) == 1
+
+
+def test_an_unstamped_translation_fails_however_old(docs_repo: DocsRepo):
+    docs_repo.translation("fi", "index.md", stamp=None)
+    base = docs_repo.commit()
+    docs_repo.write("unrelated.txt", "not documentation\n")
+
+    assert run("--check", "--since", base) == 1
+
+
+def test_an_orphaned_translation_fails_however_old(docs_repo: DocsRepo):
+    # An orphan has no English source left, so it cannot be stamped from one.
+    docs_repo.translation("fi", "gone.md", stamp="0" * 40)
+    base = docs_repo.commit()
+    docs_repo.write("unrelated.txt", "not documentation\n")
+
+    assert run("--check", "--since", base) == 1
+
+
+def test_what_was_not_gated_on_is_stated(docs_repo: DocsRepo, capsys):
+    docs_repo.source("other.md")
+    docs_repo.translation("fi", "other.md")
+    docs_repo.translation("sv", "other.md")
+    docs_repo.source("other.md", "# Title\n\nEdited without translating.\n")
+    base = docs_repo.commit()
+
+    assert run("--check", "--since", base) == 0
+    out = capsys.readouterr().out
+    assert "other.md" in out
+    # A green run that quietly forgave two stale translations reads exactly
+    # like a repository with none.
+    assert "2" in out and "not gated on" in out
+
+
+def test_a_ref_that_does_not_resolve_is_not_a_pass(docs_repo: DocsRepo, capsys):
+    docs_repo.source("index.md", "# Title\n\nEdited in this change.\n")
+
+    assert run("--check", "--since", "no-such-ref") == 2
+    assert "no-such-ref" in capsys.readouterr().out
+
+
+def test_since_on_a_plain_report_is_refused(docs_repo: DocsRepo, capsys):
+    # The report shows everything by design, so --since would change nothing.
+    # Silently inert is worse: the caller believes it scoped something.
+    assert run("--since", "HEAD") == 2
+    out = capsys.readouterr().out
+    assert "--check" in out and "--comment" in out
+
+
+def test_the_comment_omits_what_the_gate_excused(docs_repo: DocsRepo, capsys):
+    """The comment body is the verdict, so it must agree with the verdict.
+
+    render_comment covers every entry the gate fails on. Under --since the gate
+    fails on fewer, and a comment naming a page the run passed on sends its
+    author to translate something nobody asked them for.
+    """
+    docs_repo.source("stale-already.md")
+    docs_repo.translation("fi", "stale-already.md")
+    docs_repo.translation("sv", "stale-already.md")
+    docs_repo.source("stale-already.md", "# Title\n\nEdited without translating.\n")
+    base = docs_repo.commit()
+
+    assert run("--comment", "--check", "--since", base) == 0
+    body = capsys.readouterr().out
+    assert "stale-already.md" not in body
+    assert "not gated on" not in body
+
+
+def test_the_comment_can_be_scoped_without_gating(docs_repo: DocsRepo, capsys):
+    """The workflow's comment step wants the scope, not the exit status."""
+    docs_repo.source("stale-already.md")
+    docs_repo.translation("fi", "stale-already.md")
+    docs_repo.translation("sv", "stale-already.md")
+    docs_repo.source("stale-already.md", "# Title\n\nEdited without translating.\n")
+    base = docs_repo.commit()
+
+    assert run("--comment", "--since", base) == 0
+    assert "stale-already.md" not in capsys.readouterr().out
+
+
+def test_the_comment_still_names_what_this_change_broke(docs_repo: DocsRepo, capsys):
+    base = docs_repo.commit()
+    docs_repo.source("index.md", "# Title\n\nEdited in this change.\n")
+
+    assert run("--comment", "--check", "--since", base) == 1
+    assert "index.md" in capsys.readouterr().out
diff --git a/uv.lock b/uv.lock
index 584f1f3..e73ba25 100644
--- a/uv.lock
+++ b/uv.lock
@@ -13,7 +13,7 @@ wheels = [
 
 [[package]]
 name = "halos-docs-tools"
-version = "0.1.0"
+version = "0.2.0"
 source = { editable = "." }
 dependencies = [
     { name = "pyyaml" },