diff --git a/frontend/src/api/family.ts b/frontend/src/api/family.ts
index 5162b578..45852044 100644
--- a/frontend/src/api/family.ts
+++ b/frontend/src/api/family.ts
@@ -17,12 +17,23 @@ export interface Criterion {
   test: string;
 }
 
+export interface IdeaTopic {
+  id: number;
+  title: string;
+  rulebook_id: number;
+  /** Present on a single idea's read, not on the list. */
+  rules?: { id: number; title: string }[];
+}
+
 export interface FamilyIdea {
   note_id: number;
   status: IdeaStatus;
   applies_when: string;
   canon_version: number;
   topic_id: number | null;
+  /** The rule topic holding the idea's binding norms; null when none is
+   *  linked or the reader does not own its rulebook. */
+  topic: IdeaTopic | null;
   title: string;
   note_type: string;
   is_task: boolean;
diff --git a/frontend/src/views/FamilyView.vue b/frontend/src/views/FamilyView.vue
index 67444c6e..0ca2997f 100644
--- a/frontend/src/views/FamilyView.vue
+++ b/frontend/src/views/FamilyView.vue
@@ -259,6 +259,12 @@ onMounted(load);
               <div v-if="idea.platforms.length" class="fam-platforms">
                 <code v-for="p in idea.platforms" :key="p" class="fam-chip">{{ p }}</code>
               </div>
+              <p v-if="idea.topic" class="fam-muted fam-topic">
+                Binding rules:
+                <router-link
+                  :to="{ path: '/rules', query: { rb: String(idea.topic.rulebook_id), topic: String(idea.topic.id) } }"
+                >{{ idea.topic.title }}</router-link>
+              </p>
             </div>
             <button
               v-if="idea.status !== 'retired'"
@@ -376,6 +382,7 @@ onMounted(load);
 .fam-row-title { display: flex; flex-wrap: wrap; align-items: baseline; gap: 0.25rem 0.5rem; }
 .fam-applies { margin: 0.3rem 0 0; font-size: 0.85rem; color: var(--fs-text-secondary); }
 .fam-platforms { display: flex; flex-wrap: wrap; gap: 0.3rem; margin-top: 0.35rem; }
+.fam-topic { margin: 0.35rem 0 0; }
 .fam-chip {
   font-family: var(--fs-font-mono);
   font-size: 0.72rem;
diff --git a/plugin/.claude-plugin/plugin.json b/plugin/.claude-plugin/plugin.json
index 665e6325..2f7a1d99 100644
--- a/plugin/.claude-plugin/plugin.json
+++ b/plugin/.claude-plugin/plugin.json
@@ -1,7 +1,7 @@
 {
   "name": "scribe",
   "description": "Scribe for Claude Code: connects the scribe MCP server, adds the hooks that deliver live project state and relevant records at the right moment, ships the shared client-neutral Scribe skills (using-scribe, writing-plans, reporting-back, systematic-debugging, verification, brainstorming, reusing-code, shape-accounting, family-canon), and syncs your saved Scribe Processes as skills (/scribe:sync).",
-  "version": "2026.10.06.1726",
+  "version": "2026.10.06.1827",
   "author": {
     "name": "Bryan Van Deusen"
   },
diff --git a/plugin/skills/family-canon/SKILL.md b/plugin/skills/family-canon/SKILL.md
index ff883481..c3e1d62e 100644
--- a/plugin/skills/family-canon/SKILL.md
+++ b/plugin/skills/family-canon/SKILL.md
@@ -33,6 +33,9 @@ wrote what you wrote:
    needs support you can name; **one criterion with no support vetoes it**.
 3. Promote it, or leave it a candidate with the reason. A held candidate is
    precedent too, so the reason is the record — never skip writing it.
+4. If rules already bind the idea — a rule topic written for it — link that
+   topic with `set_family_topic`. The note teaches; the topic's rules bind,
+   and every assessment then reads them beside the idea.
 
 A milestone closing on a platform project hints without recording anything:
 ask whether what it built is something every project on the platform will
diff --git a/src/scribe/mcp/server.py b/src/scribe/mcp/server.py
index 43d3637f..9edc3aa1 100644
--- a/src/scribe/mcp/server.py
+++ b/src/scribe/mcp/server.py
@@ -196,7 +196,7 @@ _WRITE_TOOLS = frozenset({
     "undo_family_decision",
     # family canon — the adoption ledger
     "revise_family_idea", "assess_family_adoption", "resolve_family_conflict",
-    "set_family_references",
+    "set_family_references", "set_family_topic",
     "bind_repo", "unbind_repo",
     # snippets, processes, the shape ledger
     "create_snippet", "update_snippet", "delete_snippet", "verify_snippet",
diff --git a/src/scribe/mcp/tools/family.py b/src/scribe/mcp/tools/family.py
index da157c85..30e25e2d 100644
--- a/src/scribe/mcp/tools/family.py
+++ b/src/scribe/mcp/tools/family.py
@@ -372,12 +372,31 @@ async def set_family_references(note_id: int, snippet_ids: list[int]) -> dict:
     return {"references": refs}
 
 
+async def set_family_topic(note_id: int, topic_id: int) -> dict:
+    """Link a family idea to the rule topic that holds its binding norms — the
+    rules every project on its platforms follows. The note says when the idea
+    applies and why; the topic's rules say what must hold. One idea per topic.
+    get_family_idea and get_family_adoption then list those rules, so an
+    assessment judges against them.
+
+    Use it when an idea already has rules written for it, or when you write
+    rules that exist to carry one idea. The version does not move: linking
+    changes where the norms are found, not what they say.
+
+    Args:
+        note_id: the family idea.
+        topic_id: a topic in a rulebook you own (list_rulebooks,
+            list_topics). 0 unlinks.
+    """
+    return await family_svc.set_topic(current_user_id(), note_id, topic_id)
+
+
 def register(mcp) -> None:
     for fn in (
         list_family_ideas, get_family_idea, propose_family_idea,
         promote_family_idea, retire_family_idea, undo_family_decision,
         list_family_decisions, revise_family_idea, get_family_adoption,
         list_family_adoptions, assess_family_adoption, resolve_family_conflict,
-        set_family_references,
+        set_family_references, set_family_topic,
     ):
         mcp.tool(name=fn.__name__)(fn)
diff --git a/src/scribe/models/family.py b/src/scribe/models/family.py
index bdd2d5ae..d89bba83 100644
--- a/src/scribe/models/family.py
+++ b/src/scribe/models/family.py
@@ -23,8 +23,9 @@ The tables, and the one job each does:
 - `family_ideas` — a note's family state: candidate, canon or retired, its
   applicability test, its canon version, its linked rule topic.
 - `family_idea_platforms` — the platforms an idea is for. The ONLY scope
-  source: a linked topic takes its scope from here rather than carrying its
-  own, so the two can never disagree.
+  source: a linked topic carries no platforms of its own, so the two can
+  never disagree. The scope decides which projects owe the idea an answer;
+  the topic's rules still reach a session by ordinary rule retrieval.
 - `family_idea_references` — the reference implementations.
 - `family_adoptions` — one row per (project, idea): the project's answer.
 - `family_decisions` — the append-only log of every promotion and every
@@ -165,8 +166,9 @@ class FamilyIdea(Base, TimestampMixin):
     comparing the two numbers, never stored as a flag that could go stale.
 
     `topic_id` is the rule topic holding the idea's binding norms, if it has
-    any (the note↔topic link #3236 asked for). The topic takes its scope from
-    this idea; it never carries platforms of its own.
+    any (the note↔topic link #3236 asked for), set by `set_topic`. The topic
+    never carries platforms of its own; the idea's readouts list its rules,
+    so an assessment judges a project against them.
     """
 
     __tablename__ = "family_ideas"
diff --git a/src/scribe/services/family.py b/src/scribe/services/family.py
index 946bef2f..0f328802 100644
--- a/src/scribe/services/family.py
+++ b/src/scribe/services/family.py
@@ -52,7 +52,9 @@ from scribe.models.family import (
 )
 from scribe.models.note import Note
 from scribe.models.project import Project
+from scribe.models.rulebook import Rule
 from scribe.services import access
+from scribe.services import rulebooks as rulebooks_svc
 
 logger = logging.getLogger(__name__)
 
@@ -140,6 +142,26 @@ async def _platform_slugs(session, note_id: int) -> list[str]:
     return list(rows.scalars().all())
 
 
+async def _topic(session, user_id: int, topic_id: int | None, *, rules: bool) -> dict | None:
+    """The rule topic holding an idea's binding norms, for a reader. Rulebooks
+    belong to their owner, so a topic the reader does not own reads as no
+    topic."""
+    if not topic_id:
+        return None
+    topic = await rulebooks_svc.get_topic(topic_id, user_id)
+    if topic is None:
+        return None
+    out = {"id": topic.id, "title": topic.title, "rulebook_id": topic.rulebook_id}
+    if rules:
+        out["rules"] = [
+            {"id": r.id, "title": r.title} for r in (await session.execute(
+                select(Rule).where(Rule.topic_id == topic.id, Rule.deleted_at.is_(None))
+                .order_by(Rule.order_index.asc(), Rule.id.asc())
+            )).scalars().all()
+        ]
+    return out
+
+
 async def _snapshot(session, idea: FamilyIdea | None) -> dict | None:
     """The idea's state, as a decision's before/after. Slugs, never ids: an id
     inside JSON cannot be remapped by a restore (the #3182 trap)."""
@@ -187,6 +209,7 @@ async def get_idea(user_id: int, note_id: int) -> dict | None:
             "is_task": note.is_task,
             "project_id": note.project_id,
             "platforms": await _platform_slugs(session, note_id),
+            "topic": await _topic(session, user_id, idea.topic_id, rules=True),
             "adoptions": counts,
             "decisions": [_decision_dict(d) for d in decisions],
             "undoable_decision_id": _undoable_id(decisions),
@@ -226,6 +249,7 @@ async def list_ideas(
                 "is_task": note_status is not None,
                 "project_id": project_id,
                 "platforms": await _platform_slugs(session, idea.note_id),
+                "topic": await _topic(session, user_id, idea.topic_id, rules=False),
             })
             out.append(d)
     return out
@@ -677,6 +701,42 @@ async def revise(
                 "ledger_rows_opened": opened, "ledger_rows_closed": closed}
 
 
+async def set_topic(user_id: int, note_id: int, topic_id: int) -> dict:
+    """Link an idea to the rule topic holding its binding norms, or unlink it
+    with topic_id 0. The note carries the idea; the topic carries the rules a
+    project on its platforms must follow. One idea per topic, since a topic's
+    norms belong to one standard.
+
+    Not a change of substance, so the version does not move: the norms were
+    rules before the link and are the same rules after it. Re-linking is the
+    undo, as with the references."""
+    if not await access.can_write_note(user_id, note_id):
+        raise ValueError(f"note {note_id} not found or no write access")
+    async with async_session() as session:
+        idea = await session.get(FamilyIdea, note_id)
+        if idea is None:
+            raise ValueError(f"#{note_id} is not a family idea")
+        if topic_id:
+            if await rulebooks_svc.get_topic(topic_id, user_id) is None:
+                raise ValueError(f"topic {topic_id} not found in a rulebook you own")
+            holder = (await session.execute(
+                select(FamilyIdea.note_id, Note.title)
+                .join(Note, Note.id == FamilyIdea.note_id)
+                .where(FamilyIdea.topic_id == topic_id, FamilyIdea.note_id != note_id)
+            )).first()
+            if holder is not None:
+                raise ValueError(
+                    f"topic {topic_id} already carries the norms of #{holder[0]} "
+                    f"“{holder[1]}” — unlink it there first, or merge the two ideas"
+                )
+        idea.topic_id = topic_id or None
+        idea.updated_at = _now()
+        await session.commit()
+        out = idea.to_dict()
+        out["topic"] = await _topic(session, user_id, idea.topic_id, rules=True)
+        return out
+
+
 async def _existing_decision_ids(ids: list[int]) -> list[int]:
     ids = [int(i) for i in ids if i]
     if not ids:
diff --git a/tests/test_family_adoption.py b/tests/test_family_adoption.py
index 585872ef..ca38201b 100644
--- a/tests/test_family_adoption.py
+++ b/tests/test_family_adoption.py
@@ -181,6 +181,6 @@ def test_the_outcomes_the_agent_is_told_are_the_ones_enforced():
 def test_every_adoption_tool_is_classified():
     reads = {"get_family_adoption", "list_family_adoptions"}
     writes = {"assess_family_adoption", "resolve_family_conflict", "revise_family_idea",
-              "set_family_references"}
+              "set_family_references", "set_family_topic"}
     assert reads <= _READ_ONLY_TOOLS
     assert writes <= _WRITE_TOOLS
diff --git a/tests/test_integration_family_promotion.py b/tests/test_integration_family_promotion.py
index 5665dcf5..31cddbb4 100644
--- a/tests/test_integration_family_promotion.py
+++ b/tests/test_integration_family_promotion.py
@@ -11,6 +11,7 @@ test here (`_no_meaning`); the repeat tests stub it to one hit, to pin what
 the trigger does WITH a hit. The ranking itself is the shared semantic
 search, tested where that lives.
 """
+import uuid
 from unittest.mock import AsyncMock, patch
 
 import pytest
@@ -24,6 +25,7 @@ from scribe.models.family import (
 from scribe.models.milestone import Milestone
 from scribe.models.note import Note
 from scribe.models.project import Project
+from scribe.models.rulebook import Rule, Rulebook, RulebookTopic
 from scribe.models.user import User
 from scribe.services import family as family_svc
 from tests.helpers import ensure_user
@@ -291,3 +293,86 @@ async def test_a_milestone_closing_on_a_platform_asks_and_one_off_platform_does_
     assert hint and "Android app" in hint
     assert await family_svc.milestone_trigger(family["owner"], off_platform) is None
     assert await family_svc.milestone_is_open(family["owner"], on_platform.id) is True
+
+
+# --- the note↔topic link ----------------------------------------------------------
+
+@pytest_asyncio.fixture
+async def topics(family):
+    """A topic of the owner's with two rules, a second empty one, and one in
+    the outsider's rulebook. Titles carry a nonce: rulebooks are not purged
+    with the notes, and a topic's title is unique within its rulebook."""
+    nonce = uuid.uuid4().hex[:8]
+    async with async_session() as s:
+        mine = Rulebook(owner_user_id=family["owner"], title=f"family norms {nonce}")
+        theirs = Rulebook(owner_user_id=family["outsider"], title=f"their norms {nonce}")
+        s.add_all([mine, theirs])
+        await s.flush()
+        norms = RulebookTopic(rulebook_id=mine.id, title="distribution")
+        spare = RulebookTopic(rulebook_id=mine.id, title="spare")
+        foreign = RulebookTopic(rulebook_id=theirs.id, title="theirs")
+        s.add_all([norms, spare, foreign])
+        await s.flush()
+        s.add_all([
+            Rule(topic_id=norms.id, title="One release key", statement="Sign with one key.",
+                 order_index=0),
+            Rule(topic_id=norms.id, title="No debug signer", statement="Check the signer.",
+                 order_index=1),
+        ])
+        await s.commit()
+        return {"norms": norms.id, "spare": spare.id, "foreign": foreign.id,
+                "rulebook": mine.id}
+
+
+async def test_an_idea_links_to_its_topic_and_its_reads_name_the_rules(family, topics):
+    await _promote(family)
+    out = await family_svc.set_topic(family["owner"], family["note"], topics["norms"])
+    assert out["topic_id"] == topics["norms"]
+    assert [r["title"] for r in out["topic"]["rules"]] == ["One release key", "No debug signer"]
+    # Where the norms are found is not what they say: the version holds.
+    assert out["canon_version"] == 1
+
+    idea = await family_svc.get_idea(family["owner"], family["note"])
+    assert idea["topic"]["rulebook_id"] == topics["rulebook"]
+    assert len(idea["topic"]["rules"]) == 2
+    [listed] = [i for i in await family_svc.list_ideas(family["owner"])
+                if i["note_id"] == family["note"]]
+    assert listed["topic"] == {"id": topics["norms"], "title": "distribution",
+                               "rulebook_id": topics["rulebook"]}
+
+
+async def test_zero_unlinks_the_topic(family, topics):
+    await _promote(family)
+    await family_svc.set_topic(family["owner"], family["note"], topics["norms"])
+    out = await family_svc.set_topic(family["owner"], family["note"], 0)
+    assert out["topic_id"] is None and out["topic"] is None
+
+
+async def test_a_topic_outside_the_callers_rulebooks_is_refused(family, topics):
+    await _promote(family)
+    with pytest.raises(ValueError, match="rulebook you own"):
+        await family_svc.set_topic(family["owner"], family["note"], topics["foreign"])
+    assert (await _idea(family["note"])).topic_id is None
+
+
+async def test_one_topic_carries_one_ideas_norms(family, topics):
+    await _promote(family)
+    await family_svc.set_topic(family["owner"], family["note"], topics["norms"])
+    async with async_session() as s:
+        other = Note(user_id=family["owner"], project_id=family["b"], title="Another idea",
+                     body="something else every Android app needs")
+        s.add(other)
+        await s.flush()
+        s.add(FamilyIdea(note_id=other.id, status="candidate"))
+        await s.commit()
+        other_id = other.id
+    with pytest.raises(ValueError, match="already carries the norms"):
+        await family_svc.set_topic(family["owner"], other_id, topics["norms"])
+    # Re-linking the same idea to its own topic is not a conflict.
+    await family_svc.set_topic(family["owner"], family["note"], topics["norms"])
+
+
+async def test_someone_who_cannot_write_the_idea_cannot_link_it(family, topics):
+    await _promote(family)
+    with pytest.raises(ValueError, match="no write access"):
+        await family_svc.set_topic(family["outsider"], family["note"], topics["spare"])