fix(rules): planning reads list rules by id and title instead of restating them (#4081)

start_planning on project 2 replied with 92,645 characters, 65k of them
applicable_rules. Milestone 414 made a project's listing every global rule
tagged to an area it works in (before, the rules of subscribed rulebooks, and
project 2 subscribed to none), and the non-brief rules_payload sent each as a
full rule_brief. get_milestone, get_project and get_task carried the same.

Every rules_payload form now lists: id, title, the topic a global rule sits in,
and `via` for a co_surfaces partner. get_rule reads one in full, and retrieval
delivers them in full when work matches — the reasoning #4045 applied to the
handshake. A test pins 81 full-length rules under 6k characters.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01821k5B3Ysecp9fNYs92Kuy

src/scribe/services/rulebooks.py

@@ -1112,36 +1112,46 @@ def rules_payload(
     (`plugin_context`) — computes a marker and shows nobody anything, and
     counting it would put rules in the denominator that no agent ever saw.
 
+    EVERY FORM LISTS, NONE RESTATES. Rules reach a session in full by
+    retrieval, so these payloads say which constraints exist — id and title,
+    the topic a global rule sits in, `via` for a co_surfaces partner — and
+    get_rule reads one. Planning reads carried the full rule_brief until a
+    project's listing grew to every global rule tagged to its areas
+    (milestone 414) and start_planning replied with 92k characters (#4081),
+    the shape #4045 had just removed from the handshake.
+
     `brief` is the session handshake's form (#4045): the project's own rules
-    as id and title, nothing else. Rules reach a session in full by
-    retrieval, so the handshake lists which of the project's constraints exist
-    rather than restating them; get_rule reads one. Only what is shown is
-    recorded as surfaced.
+    only. Only what is shown is recorded as surfaced.
     """
+    project_rules = [_rule_line(r) for r in applicable.get("project_rules", [])]
     if brief:
-        project_rules = [
-            {"id": r["id"], "title": r["title"]}
-            for r in applicable.get("project_rules", [])
-        ]
         record_rule_surfaced(
             user_id=user_id, rule_ids=[r["id"] for r in project_rules], source=source,
         )
         return {"project_rules": project_rules}
+    rules = [_rule_line(r) for r in applicable.get("rules", [])]
     record_rule_surfaced(
         user_id=user_id,
-        rule_ids=(
-            [r["id"] for r in applicable.get("rules", [])]
-            + [r["id"] for r in applicable.get("project_rules", [])]
-        ),
+        rule_ids=[r["id"] for r in rules] + [r["id"] for r in project_rules],
         source=source,
     )
     return {
-        "applicable_rules": applicable["rules"],
+        "applicable_rules": rules,
         "applicable_rules_truncated": applicable["truncated"],
-        "project_rules": applicable.get("project_rules", []),
+        "project_rules": project_rules,
     }
 
 
+def _rule_line(brief: dict) -> dict:
+    """One rule as a listing names it: enough to recognise it and fetch it.
+    Keys a row does not carry are left out rather than sent empty (#2483)."""
+    line = {"id": brief["id"], "title": brief["title"]}
+    for key in ("topic_title", "via"):
+        if brief.get(key):
+            line[key] = brief[key]
+    return line
+
+
 # ── The staleness marker (milestone 323 step 5) ────────────────────────
 #
 # WHAT THIS CAN AND CANNOT SEE. An etag catches a rule that MOVED after a

tests/test_milestone_summary_brief.py

@@ -193,3 +193,28 @@ async def test_list_milestones_lists_every_milestone_without_plans():
         out = await list_milestones(project_id=5)
     assert len(out["milestones"]) == 30
     assert all("body" not in m for m in out["milestones"])
+
+
+def test_a_planning_read_lists_rules_without_restating_them():
+    """#4081: a project's listing is every global rule tagged to its areas, so
+    the full rule_brief of each put start_planning at 92k characters. Planning
+    reads name the rules; get_rule reads one."""
+    from scribe.services.rulebooks import rules_payload
+
+    applicable = {
+        "rules": [{"id": i, "title": f"r{i}", "statement": PLAN, "when_to_apply": PLAN,
+                   "topic_title": "git", "relations": [{"note": PLAN}]} for i in range(50)]
+                 + [{"id": 900, "title": "partner", "statement": PLAN, "via": "co_surfaces"}],
+        "project_rules": [{"id": 100 + i, "title": f"pr{i}", "statement": PLAN}
+                          for i in range(30)],
+        "truncated": True,
+    }
+    with patch("scribe.services.rulebooks.record_rule_surfaced") as surfaced:
+        out = rules_payload(applicable, user_id=7, source="start_planning")
+
+    assert out["applicable_rules"][0] == {"id": 0, "title": "r0", "topic_title": "git"}
+    assert out["applicable_rules"][-1] == {"id": 900, "title": "partner", "via": "co_surfaces"}
+    assert out["project_rules"][0] == {"id": 100, "title": "pr0"}
+    assert out["applicable_rules_truncated"] is True
+    assert len(surfaced.call_args.kwargs["rule_ids"]) == 81
+    assert len(json.dumps(out)) < 6_000, len(json.dumps(out))