feat(archivist): link the wiki page in the capture reply

stacklets/docs/bot/archivist.py

@@ -66,7 +66,7 @@
 )
 from stack import media, resolve_model
 from stack.email_message import defang_links
-from stack.links import go_docs, go_topic, public
+from stack.links import go_capture, go_docs, go_topic, public
 from stack.ai.client import (
     ModelCapabilities,
 )
@@ -2444,7 +2444,7 @@ async def _reply_for_capture(
                 self.t,
                 source_title_hint=o.source_title_hint,
                 classification=o.classification,
-                link=o.display_link,
+                link=self._capture_link(o) or o.display_link,
                 transcript=o.transcript,
                 todo_link=self._todo_link(o),
             )
@@ -2462,6 +2462,30 @@ async def _reply_for_capture(
         )
         await self._answer(room_id, reply, reply_to, metadata=metadata)
 
+    def _capture_link(self, o: CaptureOutcome) -> str:
+        """A `/go/capture/<id>` link to the page this capture became.
+
+        The footer used to carry the source: the URL that was pasted, or
+        a placeholder for typed text. That is the message directly above
+        the reply in the room, so it told the sender nothing they did not
+        have, while the one new thing -- where it was filed -- was not
+        there at all. The page itself carries the source, so nothing is
+        lost by pointing at the page instead.
+
+        Keyed by capture id rather than vault path because the path moves
+        on its own: a capture re-scopes when a second person joins the
+        room, a topic gets renamed, a correction rewrites the title. The
+        resolver looks the id up in the tree it serves.
+
+        "" when there is nothing to link -- no home base yet, or a
+        capture that never reached the mirror and so has no page. The
+        caller falls back to the source footer.
+        """
+        capture_id = ((o.envelope or {}).get("data") or {}).get("capture_id")
+        if not capture_id:
+            return ""
+        return public(go_capture(str(capture_id)), self.link_base_url)
+
     def _todo_link(self, o: CaptureOutcome) -> str:
         """A `/go/topic/<scope>/todo` link when a topic capture produced todos.
 

tests/unit/stacklets/test_archivist_routing.py

@@ -30,6 +30,7 @@
 sys.path.insert(0, str(_REPO_ROOT / "stacklets" / "docs" / "bot"))
 
 import voice  # noqa: E402
+from capture_pipeline import CaptureOutcome  # noqa: E402
 from archivist import ArchivistBot  # noqa: E402
 
 
@@ -1122,3 +1123,55 @@ async def test_a_capture_still_files_when_there_is_nowhere_to_keep_it(
 
         assert calls[0]["kept_media"] is None
         assert calls[0]["file_data"] == b"%PDF-1.4 anmeldung"
+
+
+class TestTheReplyPointsAtThePage:
+    """What the "saved" message links to.
+
+    The footer used to be the source: the URL that was pasted, or a
+    placeholder for typed text. That is the message directly above the
+    reply in the room, so it repeated what the sender already had and
+    left out the only new fact, which is where the capture was filed.
+    """
+
+    def _outcome(self, capture_id="$abc:server"):
+        data = {"vault_path": "family/camping/notes/2026/09/x.md"}
+        if capture_id:
+            data["capture_id"] = capture_id
+        return CaptureOutcome(
+            status="captured",
+            classification={"title": "Boiler service"},
+            display_link="https://example.org/boiler",
+            envelope={"type": "capture.filed", "data": data},
+        )
+
+    def test_the_link_addresses_the_capture_by_id(self, tmp_path, monkeypatch):
+        """Not by vault path: a capture re-scopes when a second person
+        joins the room, a topic gets renamed, a correction rewrites the
+        title. The id is assigned once and never rewritten."""
+        monkeypatch.setenv("LINK_BASE_URL", "https://home.example.org/go")
+        bot = _build_bot(tmp_path)
+
+        link = bot._capture_link(self._outcome())
+
+        assert link == "https://home.example.org/go/capture/%24abc%3Aserver"
+
+    def test_a_capture_that_never_landed_has_nothing_to_link(
+        self, tmp_path, monkeypatch,
+    ):
+        """No mirror, no page. The caller falls back to the source."""
+        monkeypatch.setenv("LINK_BASE_URL", "https://home.example.org/go")
+        bot = _build_bot(tmp_path)
+
+        assert bot._capture_link(self._outcome(capture_id=None)) == ""
+
+    def test_no_home_base_means_no_link_rather_than_a_broken_one(
+        self, tmp_path, monkeypatch,
+    ):
+        """Core renders LINK_BASE_URL; until it has, the namespace is not
+        reachable and posting a URL into it would be a dead link."""
+        monkeypatch.delenv("LINK_BASE_URL", raising=False)
+        bot = _build_bot(tmp_path)
+
+        assert bot._capture_link(self._outcome()) == ""
+