diff --git a/backend/druks/contrib/review/datastructures.py b/backend/druks/contrib/review/datastructures.py
index 9ea0d7c2..81fae076 100644
--- a/backend/druks/contrib/review/datastructures.py
+++ b/backend/druks/contrib/review/datastructures.py
@@ -45,7 +45,7 @@ def get_summary(self) -> ReviewSummary:
         )
 
     @classmethod
-    def list_summaries(cls) -> list[ReviewSummary]:
+    def list_summaries(cls, account_id: str | None) -> list[ReviewSummary]:
         """The reviews still going or stopped on a failure. A finished one lives on its
         pull request, so it leaves the board as soon as it has something to show there."""
         return [pull_request.get_summary() for pull_request in cls.list_open()]
diff --git a/backend/druks/contrib/ship/models.py b/backend/druks/contrib/ship/models.py
index 20e1727f..9be838e0 100644
--- a/backend/druks/contrib/ship/models.py
+++ b/backend/druks/contrib/ship/models.py
@@ -110,7 +110,7 @@ def get_summary(self) -> "ProjectRepoSummary":
         return ProjectRepoSummary.model_validate(self)
 
     @classmethod
-    def list_summaries(cls) -> list["ProjectRepoSummary"]:
+    def list_summaries(cls, account_id: str | None) -> list["ProjectRepoSummary"]:
         # A repo is registered, not transient, so the board is all of them by name.
         stmt = select(cls).order_by(cls.full_name)
         return [repo.get_summary() for repo in db_session().scalars(stmt)]
@@ -228,7 +228,7 @@ def get_summary(self) -> WorkItemSummary:
         return WorkItemSummary.model_validate(self)
 
     @classmethod
-    def list_summaries(cls) -> list[WorkItemSummary]:
+    def list_summaries(cls, account_id: str | None) -> list[WorkItemSummary]:
         # Where a run stands colours the row; it never decides whether the row is
         # here. The 500 most-recent cover it; paginate if a board outgrows it.
         stmt = (
diff --git a/backend/druks/durable/datastructures.py b/backend/druks/durable/datastructures.py
index 1a8c8970..e58ca941 100644
--- a/backend/druks/durable/datastructures.py
+++ b/backend/druks/durable/datastructures.py
@@ -52,10 +52,12 @@ def get_summary(self) -> "SubjectSummary":
         )
 
     @classmethod
-    def list_summaries(cls) -> "Sequence[SubjectSummary]":
+    def list_summaries(cls, account_id: str | None) -> "Sequence[SubjectSummary]":
         """The subjects on this class's board, newest-movement first, each as its domain
-        summary. Returns a covariant ``Sequence`` so an extension can return a ``list``
-        of its own ``SubjectSummary`` subclass. Required once a workflow declares it."""
+        summary. ``account_id`` is the caller, or None outside a request. A shared
+        board ignores it. Returns a covariant ``Sequence`` so an extension can return
+        a ``list`` of its own ``SubjectSummary`` subclass. Required once a workflow
+        declares it."""
         raise NotImplementedError(
             f"a workflow declares {cls.__name__}, so it needs a list_summaries()"
         )
diff --git a/backend/druks/extensions/base.py b/backend/druks/extensions/base.py
index a45b85bf..24b6f1b3 100644
--- a/backend/druks/extensions/base.py
+++ b/backend/druks/extensions/base.py
@@ -398,10 +398,12 @@ def _get_subject_routes(
         point-in-time read and a ``/stream`` that pushes the whole snapshot on change.
         Mounted at ``/api/<name>/<subject_type>`` for every subject the extension's
         workflows declare. Every read here is keyed by identity, so an extension that
-        keeps no row for its subject gets the same surface as one that does."""
+        keeps no row for its subject gets the same surface as one that does. The board
+        reads pass the caller to ``list_summaries``."""
         from fastapi import APIRouter, HTTPException, status
         from fastapi.responses import StreamingResponse
 
+        from druks.accounts.context import current_account_id
         from druks.api.dependencies import EngineDep
         from druks.database import session_scope
         from druks.durable import reads
@@ -411,14 +413,14 @@ def _get_subject_routes(
         subject_type = subject_class.subject_type
         router = APIRouter(prefix=f"/{subject_type}", tags=[f"{cls.name}:{subject_type}"])
 
-        def board() -> SubjectList:
+        def board(account_id: str | None) -> SubjectList:
             return SubjectList(
                 rows=[
                     SubjectRow(
                         summary=summary,
                         status=reads.get_subject_status(subject_type, summary.id),
                     )
-                    for summary in subject_class.list_summaries()
+                    for summary in subject_class.list_summaries(account_id)
                 ]
             )
 
@@ -435,14 +437,17 @@ async def subject_response(subject_id: str) -> SubjectResponse | None:
 
         @router.get("", response_model=SubjectList, response_model_by_alias=True)
         async def list_subjects() -> SubjectList:
-            return board()
+            return board(current_account_id.get())
 
         # ``/stream`` before ``/{subject_id}`` so the literal path wins over the id matcher.
         @router.get("/stream", response_class=StreamingResponse)
         async def stream_board(engine: EngineDep) -> StreamingResponse:
+            # The generator polls after the request context ends. Capture the caller here.
+            account_id = current_account_id.get()
+
             async def snapshot() -> SubjectList:
                 with session_scope(engine):
-                    return board()
+                    return board(account_id)
 
             return StreamingResponse(
                 stream(snapshot), media_type="text/event-stream", headers=SSE_HEADERS
diff --git a/backend/druks/models.py b/backend/druks/models.py
index a345e3b2..8b098a86 100644
--- a/backend/druks/models.py
+++ b/backend/druks/models.py
@@ -94,10 +94,12 @@ def get_summary(self) -> "SubjectSummary":
         )
 
     @classmethod
-    def list_summaries(cls) -> "Sequence[SubjectSummary]":
+    def list_summaries(cls, account_id: str | None) -> "Sequence[SubjectSummary]":
         """The rows on this class's board, newest-movement first, each as its domain
-        summary. Returns a covariant ``Sequence`` so an extension can return a ``list``
-        of its own ``SubjectSummary`` subclass. Required once a workflow declares it."""
+        summary. ``account_id`` is the caller, or None outside a request. A shared
+        board ignores it. Returns a covariant ``Sequence`` so an extension can return
+        a ``list`` of its own ``SubjectSummary`` subclass. Required once a workflow
+        declares it."""
         raise NotImplementedError(
             f"a workflow declares {cls.__name__}, so it needs a list_summaries()"
         )
diff --git a/backend/tests/druks-field_notes/druks_field_notes/models.py b/backend/tests/druks-field_notes/druks_field_notes/models.py
index 4c2fadea..2e4cdd90 100644
--- a/backend/tests/druks-field_notes/druks_field_notes/models.py
+++ b/backend/tests/druks-field_notes/druks_field_notes/models.py
@@ -42,7 +42,7 @@ def get_summary(self) -> NoteSummary:
         return NoteSummary.model_validate(self)
 
     @classmethod
-    def list_summaries(cls) -> list[NoteSummary]:
+    def list_summaries(cls, account_id: str | None) -> list[NoteSummary]:
         # How many the board shows is an operator knob, so it lives on the extension.
         from druks_field_notes.extension import FieldNotes
 
diff --git a/backend/tests/druks-field_notes/tests/test_extension.py b/backend/tests/druks-field_notes/tests/test_extension.py
index a6721ae2..708c8a14 100644
--- a/backend/tests/druks-field_notes/tests/test_extension.py
+++ b/backend/tests/druks-field_notes/tests/test_extension.py
@@ -9,7 +9,7 @@ def test_the_board_honors_the_board_size(druks_db):
     newest = Note.create(body="second")
     FieldNotes.override_setting("board_size", 1)
 
-    summaries = Note.list_summaries()
+    summaries = Note.list_summaries(None)
 
     assert [summary.id for summary in summaries] == [str(newest.id)]
     assert summaries[0].body == "second"
diff --git a/backend/tests/ship/test_build_board_membership.py b/backend/tests/ship/test_build_board_membership.py
index 3e3a2749..f5736458 100644
--- a/backend/tests/ship/test_build_board_membership.py
+++ b/backend/tests/ship/test_build_board_membership.py
@@ -9,7 +9,7 @@
 
 def _board_ids(druks_db):
     druks_db.expire_all()
-    return {row.id for row in WorkItem.list_summaries()}
+    return {row.id for row in WorkItem.list_summaries(None)}
 
 
 def _resolve(item, *, merged=True, at=None):
diff --git a/backend/tests/ship/test_lane_reactions.py b/backend/tests/ship/test_lane_reactions.py
index 7cf75936..9124f192 100644
--- a/backend/tests/ship/test_lane_reactions.py
+++ b/backend/tests/ship/test_lane_reactions.py
@@ -45,7 +45,7 @@ async def test_cancelled_build_settles_the_item(druks_db):
     assert refreshed.resolution == "closed"
     assert refreshed.resolved_at
     druks_db.expire_all()
-    assert str(item.id) not in {summary.id for summary in WorkItem.list_summaries()}
+    assert str(item.id) not in {summary.id for summary in WorkItem.list_summaries(None)}
 
 
 @pytest.mark.parametrize(("merged", "resolution"), [(True, "merged"), (False, "closed")])
@@ -79,7 +79,7 @@ async def test_failed_build_remains_unresolved_on_the_board(druks_db):
     refreshed = WorkItem.get(item.id)
     assert (refreshed.resolution, refreshed.resolved_at) == (None, None)
     druks_db.expire_all()
-    assert str(item.id) in {summary.id for summary in WorkItem.list_summaries()}
+    assert str(item.id) in {summary.id for summary in WorkItem.list_summaries(None)}
 
 
 async def test_build_lifecycle_reaches_the_tracker(druks_db, monkeypatch):
diff --git a/backend/tests/ship/test_webhooks_pull_request.py b/backend/tests/ship/test_webhooks_pull_request.py
index d6a8604c..ff506022 100644
--- a/backend/tests/ship/test_webhooks_pull_request.py
+++ b/backend/tests/ship/test_webhooks_pull_request.py
@@ -202,7 +202,7 @@ async def test_a_merge_after_a_failed_build_still_settles_the_item(druks_db, tmp
 
     item = WorkItem.get(work_item_id)
     assert item.resolution == "merged"
-    assert item.id not in {summary.id for summary in WorkItem.list_summaries()}
+    assert item.id not in {summary.id for summary in WorkItem.list_summaries(None)}
     assert [row.id for row in WorkItem.list_handoff()] == [item.id]
 
 
diff --git a/backend/tests/test_extension_appless_load.py b/backend/tests/test_extension_appless_load.py
index 93396215..e9e9d090 100644
--- a/backend/tests/test_extension_appless_load.py
+++ b/backend/tests/test_extension_appless_load.py
@@ -43,7 +43,7 @@ class ProbeItem(StoredSubject):
             __tablename__ = "probe_items"
 
             @classmethod
-            def list_summaries(cls) -> list[SubjectSummary]:
+            def list_summaries(cls, account_id: str | None) -> list[SubjectSummary]:
                 return []
     """,
     "routes.py": """
@@ -215,11 +215,11 @@ def test_surfaces_are_enumerable_from_the_loaded_extension(installed):
     assert f"{_PACKAGE}.subscribers" in capability_modules
 
     settings_model = extension.settings_model
-    assert settings_model is not None
+    assert settings_model
     assert list(settings_model.model_fields) == ["budget"]
 
     package_dir = extension.package_dir()
-    assert package_dir is not None
+    assert package_dir
     assert extension.migrations_dir() == package_dir / "migrations"
 
 
diff --git a/backend/tests/test_extensions.py b/backend/tests/test_extensions.py
index 63f67fae..8e0875c6 100644
--- a/backend/tests/test_extensions.py
+++ b/backend/tests/test_extensions.py
@@ -14,7 +14,7 @@ class Widget(Subject):
     in a real extension; these stand in for that."""
 
     @classmethod
-    def list_summaries(cls) -> list:
+    def list_summaries(cls, account_id: str | None) -> list:
         return []
 
 
@@ -246,7 +246,7 @@ def workflows(cls):
 def test_a_concrete_inherited_list_summaries_satisfies_the_contract_without_calling_it():
     class Concrete(Subject):
         @classmethod
-        def list_summaries(cls) -> list:
+        def list_summaries(cls, account_id: str | None) -> list:
             raise AssertionError("validation must not call list_summaries()")
 
     class Inheritor(Concrete):
diff --git a/backend/tests/test_generic_subjects.py b/backend/tests/test_generic_subjects.py
index 7757223b..3b1005fd 100644
--- a/backend/tests/test_generic_subjects.py
+++ b/backend/tests/test_generic_subjects.py
@@ -1,6 +1,7 @@
 from pathlib import Path
 
 import pytest
+from druks.accounts.context import current_account_id
 from druks.database import db_session
 from druks.durable import AgentCall, Run
 from druks.durable.datastructures import Subject
@@ -29,7 +30,7 @@ def get_summary(self) -> _ThingSummary:
         return _ThingSummary(id=self.id, label=self.label, title=TITLES[self.id])
 
     @classmethod
-    def list_summaries(cls) -> list[_ThingSummary]:
+    def list_summaries(cls, account_id: str | None) -> list[_ThingSummary]:
         return [thing.get_summary() for thing in db_session().scalars(select(cls))]
 
 
@@ -47,10 +48,22 @@ def get_summary(self) -> _ThingSummary:
         return _ThingSummary(id=self.id, label=self.label, title=self.id.rpartition("#")[2])
 
     @classmethod
-    def list_summaries(cls) -> list[_ThingSummary]:
+    def list_summaries(cls, account_id: str | None) -> list[_ThingSummary]:
         return [ticket.get_summary() for ticket in cls.list_open()]
 
 
+CALLERS: list[str | None] = []
+
+
+class Inbox(Subject):
+    """A board scoped by who is asking."""
+
+    @classmethod
+    def list_summaries(cls, account_id: str | None) -> list[_ThingSummary]:
+        CALLERS.append(account_id)
+        return []
+
+
 class _ThingExtension(Extension):
     name = "faketest"
 
@@ -66,7 +79,7 @@ def _seed_run(
     input_gate=None,
     failure=None,
 ):
-    if state == "parked" and input_gate is None:
+    if state == "parked" and not input_gate:
         input_gate = "review"
     run = Run(
         id=str(uuid7()),
@@ -229,6 +242,27 @@ def test_list_returns_every_subject_with_status(client: TestClient, druks_db):
     assert rows["2"]["status"]["state"] == "scheduled"
 
 
+async def test_the_board_and_its_stream_hand_the_caller_to_list_summaries(druks_db):
+    # The route reads the caller at handler entry and passes it down as data.
+    # The stream keeps that caller after the request context ends.
+    endpoints = {
+        route.path: route.endpoint for route in _ThingExtension._get_subject_routes(Inbox).routes
+    }
+
+    CALLERS.clear()
+    token = current_account_id.set("acct-7")
+    try:
+        await endpoints["/inbox"]()
+        response = await endpoints["/inbox/stream"](engine=druks_db.get_bind())
+    finally:
+        current_account_id.reset(token)
+    assert CALLERS == ["acct-7"]
+
+    await anext(response.body_iterator)
+    await response.body_iterator.aclose()
+    assert CALLERS == ["acct-7", "acct-7"]
+
+
 def test_unknown_subject_is_404(client: TestClient, druks_db):
     assert client.get("/api/faketest/thing/nope").status_code == 404
     # An id the subject could never wear misses the same way, row or no row.
diff --git a/docs/writing-an-extension.md b/docs/writing-an-extension.md
index 058be4c3..d74a41c9 100644
--- a/docs/writing-an-extension.md
+++ b/docs/writing-an-extension.md
@@ -459,7 +459,7 @@ class Repository(StoredSubject):
         return self.full_name
 
     @classmethod
-    def list_summaries(cls) -> list[SubjectSummary]:
+    def list_summaries(cls, account_id: str | None) -> list[SubjectSummary]:
         return [repository.get_summary() for repository in cls.list_open()]
 ```
 
@@ -489,7 +489,7 @@ from druks.workflows import Subject
 
 class PullRequest(Subject):
     @classmethod
-    def list_summaries(cls) -> list[SubjectSummary]:
+    def list_summaries(cls, account_id: str | None) -> list[SubjectSummary]:
         return [pull_request.get_summary() for pull_request in cls.list_open()]
 ```
 
@@ -498,8 +498,12 @@ Any id names one of these, so a detail read always answers. Override
 `owner/repo#7` is a pull request, `nonsense` is a 404.
 
 Each subject a workflow declares must implement `list_summaries()`. The board
-reads it. Druks checks this at load. If the method is missing, the extension
-does not load. The error names the extension, the subject, and the method.
+reads it and passes the caller. `account_id` is the signed-in account, or None
+outside a request. Use it to scope the rows when each operator has their own
+board. Ignore it when every operator shares one board. A model method never
+reads request context. Druks checks the method at load. If it is missing, the
+extension does not load. The error names the extension, the subject, and the
+method.
 
 Druks serves the same `/api/night_watch/repository` surface either way: a board,
 a page for one, and a live stream of either, mounted for every subject your
@@ -848,7 +852,7 @@ for connection in NightWatch.acme.list_for_account(account_id):
 
 `account_id` is the caller: `self.account_id` in a run body,
 `current_account_id.get()` in a route, the handler's argument in a
-subscriber. `NightWatch.acme.get(connection_id)` returns one connection
+subscriber, the platform's argument in `list_summaries`. `NightWatch.acme.get(connection_id)` returns one connection
 when your own row stored its id. Each connection carries `id`, `scopes`, `identity` — the
 provider's facts for the sign-in — `account_id` — the druks account that
 signed it in — and `connected_at`. The handle serves