feat(rules)!: retire the always-on tier — every rule arrives by retrieval (#394)

Milestone 394, steps 5-8. Operator: "remove the always on rule functionality
as the goal was to not have it at all since it didn't seem to work as
expected."

Unconditional preload had three failures the retrieval arms do not. It could
not be MEASURED — a resident rule is in the context whether or not it
mattered, so nothing distinguished "this governed the act" from "this was
scenery", and it was the one surface structurally exempt from the scoreboard
judging every other. It was SUMMARISED AWAY by compaction while the session
went on believing it held the rules. And it CROWDED OUT the few rules that
applied with the thirty that did not.

WHAT GOES

Schema (0100): rules.tier + ck_rules_tier, rule_versions.tier,
rulebooks.always_on, and project_rulebook_exclusions — a table recording a
project's opt-out of something that no longer binds it unasked.

Tools: list_always_on_rules, exclude_always_on_rulebook,
include_always_on_rulebook. Service: the same three plus rules_etag_for,
_valid_tier and the whole etag family. The SessionStart preload and the
write-path staleness arm go with them: nothing is resident, so nothing can
have drifted since a session loaded it.

THREE CALLS WORTH REVIEWING

enter_project got NARROWER, not wider. Its filter was `always_on OR
area-tagged`; dropping the tier arm leaves the deterministic half, so a
project with no canonical-tagged Systems gets no bulk rules and reaches them
by retrieval instead. Dropping the whole clause would have made that payload
bigger than the preload this milestone deletes.

Backups import tolerantly. A pre-394 archive carries tier, always_on and the
retired inception choice; none is read, and the exclusion key is DROPPED
rather than remapped, because restoring it would write data that
validate_inception now rejects as unknown.

The migration is irreversible in the way that matters and says so: downgrade
recreates the columns at their defaults and cannot restore which rules were
always-on. A value invented to fill a hole is not a measurement.

THE INSTRUCTION SURFACES SAY THE HARDER THING

Deleting "call list_always_on_rules()" is easy; replacing it is not, because
the new model asks a session to trust something it cannot see. All three
surfaces now say a session holds nothing, that rules arrive when work matches
them, and — the half that got dangerous — that "no rule arrived" means
"nothing matched", never "there is no rule". Under residency an empty session
was rare and suspicious; it is now the ordinary state of most turns, so
reading it as permission is wrong on nearly every turn rather than
occasionally. That is #3720's defect at session scale.

test_instruction_surfaces_agree is repointed rather than retired: its two
halves collapsed into one instruction, and it gains a guard that every
surface states what absence means. _INSTRUCTIONS is back at 1999/2000 —
the inception clause paid for the longer HOW line.

UI (rule 27, and the opportunity step 8 named)

The tier selector is gone, and what replaces it is the point: `when_to_apply`
is now the field that decides whether a rule is ever seen, so the editor
marks it required, warns while it is empty, and both rule lists badge a
trigger-less rule "never surfaces". A rule without one is not quiet, it is
unreachable.

TESTS

Two files deleted outright — test_rules_etag.py and test_inception_rules.py
tested subsystems that no longer exist. Elsewhere obsolete cases were removed
and the rest repointed. One deserves naming: the wiring test asserted the act
arms pass no `tier`, which had become an assertion that could not fail. It is
repointed onto `kind`, which does still exist and where the same claim is
live — a preference must reach a write exactly as a rule does.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011cPyzNnegXHr5iRMzzy5KJ

tests/test_mcp_tool_rulebooks.py

@@ -225,7 +225,9 @@ def test_register_attaches_every_tool():
     # 26 through milestone 307, +2 for the staleness sweep (milestone 312),
     # +1 for a rule's edit history (milestone 323), +2 for preferences
     # (milestone 399).
-    assert len(mcp.names) == 31
+    # 28 since milestone 394 took list_always_on_rules and the two
+    # always-on exclusion tools with the tier they served.
+    assert len(mcp.names) == 28
     # spot-check a few names
     assert "list_rulebooks" in mcp.names
     assert "create_rule" in mcp.names
@@ -236,10 +238,6 @@ def test_register_attaches_every_tool():
     assert "create_preference" in mcp.names
     assert "update_preference" in mcp.names
     assert "subscribe_project_to_rulebook" in mcp.names
-    assert "list_always_on_rules" in mcp.names
-    # milestone 297: a project's opt-out of a whole always-on rulebook
-    assert "exclude_always_on_rulebook" in mcp.names
-    assert "include_always_on_rulebook" in mcp.names
     assert "create_project_rule" in mcp.names
     assert "suppress_rule_for_project" in mcp.names
     # milestone 312: the sweep, and the stamp that answers it
@@ -252,57 +250,12 @@ def test_register_attaches_every_tool():
     assert "unsuppress_topic_for_project" in mcp.names
 
 
-@pytest.mark.asyncio
-async def test_list_always_on_rules_returns_empty_when_no_always_on_rulebooks():
-    with patch(
-        "scribe.mcp.tools.rulebooks.rulebooks_svc.list_always_on_rules",
-        AsyncMock(return_value=[]),
-    ):
-        from scribe.mcp.tools.rulebooks import list_always_on_rules
-        out = await list_always_on_rules()
-    # An install with no always-on rulebooks still gets a marker (milestone
-    # 323): "no rules" is a STATE, and a payload that omitted the key would
-    # make the write path read every session on a fresh install as a change.
-    assert out == {"rules": [], "total": 0, "rules_etag": "empty|0"}
 
 
-@pytest.mark.asyncio
-async def test_list_always_on_rules_projects_each_rule():
-    rules = [fake_rule(id=100, title="r", statement="s", topic_id=10), fake_rule(id=101, title="r", statement="s", topic_id=10)]
-    with patch(
-        "scribe.mcp.tools.rulebooks.rulebooks_svc.list_always_on_rules",
-        AsyncMock(return_value=rules),
-    ):
-        from scribe.mcp.tools.rulebooks import list_always_on_rules
-        out = await list_always_on_rules()
-    assert out["total"] == 2
-    assert {r["id"] for r in out["rules"]} == {100, 101}
-    assert all("topic_id" in r for r in out["rules"])
 
 
-@pytest.mark.asyncio
-async def test_update_rulebook_forwards_always_on_when_set():
-    rb = fake_rulebook(id=1, title="t")
-    mock = AsyncMock(return_value=rb)
-    with patch("scribe.mcp.tools.rulebooks.rulebooks_svc.update_rulebook", mock):
-        from scribe.mcp.tools.rulebooks import update_rulebook
-        await update_rulebook(rulebook_id=1, always_on=True)
-    kwargs = mock.call_args.kwargs
-    assert kwargs.get("always_on") is True
-    assert "title" not in kwargs
-    assert "description" not in kwargs
 
 
-@pytest.mark.asyncio
-async def test_update_rulebook_omits_always_on_when_none():
-    rb = fake_rulebook(id=1, title="t")
-    mock = AsyncMock(return_value=rb)
-    with patch("scribe.mcp.tools.rulebooks.rulebooks_svc.update_rulebook", mock):
-        from scribe.mcp.tools.rulebooks import update_rulebook
-        await update_rulebook(rulebook_id=1, title="new title")
-    kwargs = mock.call_args.kwargs
-    assert "always_on" not in kwargs
-    assert kwargs["title"] == "new title"
 
 
 @pytest.mark.asyncio
@@ -454,7 +407,7 @@ def _fake_version(**over):
         "id": 5, "rule_id": 100, "user_id": 1,
         "title": "The runner has no bash", "statement": "Use sh.",
         "why": "the image ships no bash", "how_to_apply": None,
-        "when_to_apply": None, "tier": "always_on",
+        "when_to_apply": None,
         "verify_with": "read the workflow's shell setting",
         "expires_when": None,
         "created_at": datetime(2026, 8, 29, tzinfo=timezone.utc),