row 206 (193b2, #1704): sage-2818 rulings, only a human principal matches a share

#readable returns false for an agent session, so a `*` share no longer shows a user's message
in an agent's trail. New tests: a sharee's session.list refuses (Q1), and an agent bound to the
shared thread, a chief run and the tester match no share (Q2). BUILD.md records the Q1
follow-up, Q2-Q4 and the live --migrate as Mos's go under Q173. README names the agent rule.

agents/launchpad/work/queue-206/BUILD.md

@@ -10,10 +10,15 @@ sections 4.3, 5.2-5.6 and 8. Reviewer: Duckworth. Assignment: sage-2789.
 - 206 chains on 275 (193b1b, viewer verbs and board refusals), which Morgana is building. I rebase
   onto Morgana's 275 sha when it comes, and onto 253's landing under a new branch name.
 - At this base a user binds only with a collaborator grant (`#userGrants`, USER_LEVEL). Viewer
-  sessions arrive with 275, so the viewer column of design 4.3 is not testable here. On the 275
+  sessions arrive with 275, so the viewer column of design 4.3 is not testable here (sage-2818
+  Q4: the viewer column waits on the 275 rebase; 275 moves once more for Duckworth's B1,
+  duckworth-0166). On the 275
   rebase, USER_VERBS and the viewer gate merge with the three share verbs, and the share verbs
   must refuse a viewer (design 4.3: share, unshare and shares are "refused" for viewers).
 
+- The live `--migrate` (3l→3m on the running bus) is not part of this build. It is Mos's go under
+  Q173, with a backup first and a STATE report after (mos-1310 item 4).
+
 ## What changed
 
 - Schema 3l→3m. `thread_shares` as design 5.2, its index and three append-only triggers, in
@@ -41,16 +46,27 @@ sections 4.3, 5.2-5.6 and 8. Reviewer: Duckworth. Assignment: sage-2789.
 
 1. Label 3l→3m, not 3i-3j (design) or 3l (brief title). 264a took 3k-3l, and labels go by
    landing order (sage-2789).
-2. A share covers every session of the thread. The 264a comment on `session.list` says "there
-   are no shares (Q7)"; I left `session.list` owner-only, so a sharee reads any session it can
-   name but can't list them. Flagged for a ruling: either a sharee gets `session.list`, or the
-   Console names the sessions some other way.
-3. A reader session matches shares as the business human. Design 4.3 says reader sessions "stay
-   owner-only", and 5.5 says "messages in other users' unshared threads hidden" for human, reader
-   and tester. I read that as: the reader sees what the owner sees, shares to the owner included.
-4. Design 5.6's "30 s timer" and `access.reload` have no path at this base: runtime.mjs:263
-   passes `access: () => loadAccess(file, context)`, read on every request. The tests cover the
-   per-request read (removed, expired, out of scope and unreadable), which is the stricter case.
+2. A share covers every session of the thread, and `session.list` stays owner-only (sage-2818
+   Q1, from Sage's Q7 ruling, agents/sage/work/queue-264/RULINGS.md:72-77). broker.mjs keeps its
+   "no shares (Q7)" refusal: a sharee reads any session it can name but can't list them. A test
+   holds the refusal (human `thread-not-owned`, reader `read-only`, user `access-refused`).
+   **Follow-up**, bound to whichever of row 193 or the share wiring lands second: wire the sharee's
+   `session.list`. The bar is T1 sessions line 7 and REQ-USER-4 (candidate PRD 1509c7cc5,
+   docs/prd/mosaic-stack.md:1027-1052): read-only, and it needs current grants, the thread
+   owner's included.
+3. A reader session matches shares as the business human (sage-2818 Q2: accepted, for the human
+   principal only). Design 4.3 says reader sessions "stay owner-only", and 5.5 says "messages in
+   other users' unshared threads hidden" for human, reader and tester. The reader sees what the
+   owner sees, shares to the owner included. Q2 also found a gap in the first tip (16b9c6df6): an
+   agent session has no owner, but it matched a `*` share, so a shared user message showed in an
+   agent's trail. `#readable` now returns false unless the session is the business human, a
+   reader or a user. A test binds an assistant run to the shared thread and a chief run with no
+   thread, and checks that neither (nor the tester) sees the message after a `*` share and a share
+   to the owner.
+4. Access is read per request (sage-2818 Q3). Design 5.6's "30 s timer" and `access.reload` have
+   no path at this base: runtime.mjs:263 passes `access: () => loadAccess(file, context)`, read on
+   every request. The tests cover the per-request read (removed, expired, out of scope and
+   unreadable), which is the stricter case.
 5. Rule 3 asks the owner's grant for any level, like rule 2 (design: "still has a live grant
    covering t"). A user owner lowered to viewer keeps the thread readable to its sharees.
 6. An unshare checks no coverage, so an owner can end a share whose target lost its grant.
@@ -60,10 +76,11 @@ sections 4.3, 5.2-5.6 and 8. Reviewer: Duckworth. Assignment: sage-2789.
 
 ## Tests
 
-New: tests/thread-shares.test.mjs, 13 tests: the read flow and the write refusals, `*`, rule 2,
+New: tests/thread-shares.test.mjs, 15 tests: the read flow and the write refusals, `*`, rule 2,
 rule 3 (with trail for human and reader), latest-row state, share-not-covered, target checks,
 lost owner coverage, tester and reader refusals (18 `action.refused` events, no rows), trail and
-replies, sessions, the 3l→3m migration and the 3l engine's refusal of a 3m store.
+replies, sessions, the sharee's `session.list` refusal (Q1), agents and the tester matching no
+share (Q2), the 3l→3m migration and the 3l engine's refusal of a 3m store.
 
 Pins moved 3l→3m: account-, chief-of-staff, comment-, gitea-, grant-, name-, spec-, usage- and
 thread-migration, sessions, schema (23 tables, 89 triggers) and user-principal (USER_VERBS).
@@ -91,6 +108,9 @@ test must fail on an assertion; a thrown error or a refusal before the assertion
   to user:carol must refuse).
 - M9. In `thread.share`/`thread.unshare`, replace `this.#thread(s, a.thread)` with
   `this.#threadRow(s, a.thread)`. Killed by the first test (bob's share of A to `*` must refuse).
+- Q2 probe (not a design mutant). In `#readable`, delete the human-principal line
+  (`if (!s.human && !s.reader && !s.user) return false;`). Killed by "only a human principal
+  matches a share" (the agent's trail shows the message after the `*` share).
 
 ## Run limits
 

packages/bus/README.md

@@ -301,7 +301,10 @@ A session may read a thread it doesn't own only when all four hold (row 193 desi
 3. a thread owned by a user is still covered by that user's grant;
 4. neither the caller nor the owner is the tester.
 
-A reader session reads as the business human. The check runs on every request against the
+Only a human principal matches a share: the business human, a reader session as that human, or
+a user. An agent session matches none, `*` included, even when it is bound to the thread.
+A reader session reads as the business human. A sharee can't call `session.list` on the
+thread; it stays owner-only until row 193's share wiring. The check runs on every request against the
 access document the broker reads then, so a removed, expired or unreadable grant or an
 unshare ends reads on the next request. Only `thread.messages` admits a sharee; `thread.open`,
 `thread.send` and the share verbs refuse it `thread-not-owned`. `trail` and `replies` show a

packages/bus/src/broker.mjs

@@ -817,9 +817,12 @@ export class Broker {
   }
   // Row 206 (193b2, design 5.4): may a session read thread `t` it doesn't own? Rule 4 first: a
   // tester's thread is never shared, and a tester is never a share's target and holds no grant. A
-  // reader session is the owner's board view, so it reads what is shared with the owner.
+  // reader session is the owner's board view, so it reads what is shared with the owner. Only a
+  // human principal (the business human, a reader as that human, a user) matches a share: an agent
+  // session, even one bound to the thread, matches none, `*` included (sage-2818 Q2).
   #readable(s, t) {
     if (s.tester || t.owner === 'tester') return false;
+    if (!s.human && !s.reader && !s.user) return false;
     const me = s.reader ? this.#business(s.business).human : this.#owner(s);
     // Rule 1: a share in force to the caller or to everyone.
     if (!this.#shared(t.id, me) && !this.#shared(t.id, '*')) return false;

packages/bus/tests/thread-shares.test.mjs

@@ -304,6 +304,40 @@ test('a share covers every session of the thread', (t) => {
   assert.equal(code('bob', 'thread.messages', { thread: H, session: S }), 'thread-not-owned');
 });
 
+test('a sharee can\'t list the thread\'s sessions: session.list stays owner-only (Q7, sage-2818 Q1)', (t) => {
+  const { call, code, A, H } = setup(t);
+  call('alice', 'thread.share', { thread: A, to: 'jason' });
+  call('human', 'thread.share', { thread: H, to: '*' });
+  assert.equal(code('human', 'session.list', { thread: A }), 'thread-not-owned');
+  assert.equal(code('reader', 'session.list', { thread: A }), 'read-only');
+  for (const who of ['alice', 'bob']) assert.equal(code(who, 'session.list', { thread: H }), 'access-refused', who);
+  // The owners still list their own.
+  assert.equal(call('human', 'session.list', { thread: H }).length, 1);
+});
+
+test('only a human principal matches a share: an agent bound to the thread and the tester match none (sage-2818 Q2)', (t) => {
+  const { b, caps, call, code, A, H, sent } = setup(t);
+  // The assistant run serving alice's thread, and a chief run with no thread.
+  caps.agent = b.bindLaunch({ business: 'demo', role: 'assistant', run: 'assistant-run', harness: 'pi', thread: A });
+  caps.chief = b.bindLaunch({ business: 'demo', role: 'chief', run: 'chief-run', harness: 'pi' });
+  for (const who of ['agent', 'chief']) call(who, 'role.claim');
+  const seen = (who) => call(who, 'trail', { subject: sent }).some((r) => r.table === 'messages' && r.id === sent);
+  for (const who of ['agent', 'chief', 'tester']) assert.equal(seen(who), false, `${who} before`);
+  call('alice', 'thread.share', { thread: A, to: '*' });
+  call('alice', 'thread.share', { thread: A, to: 'jason' });
+  // The human principals now read it; the agents and the tester see what they saw before.
+  for (const who of ['human', 'reader']) assert.equal(seen(who), true, who);
+  for (const who of ['agent', 'chief', 'tester']) assert.equal(seen(who), false, `${who} after`);
+  for (const who of ['agent', 'chief']) {
+    assert.equal(code(who, 'thread.messages', { thread: A }), 'human-required', who);
+    assert.equal(code(who, 'replies', { id: sent }), 'human-required', who);
+  }
+  assert.equal(code('tester', 'thread.messages', { thread: A }), 'thread-not-owned');
+  assert.equal(code('tester', 'replies', { id: sent }), 'message-not-found');
+  call('human', 'thread.share', { thread: H, to: '*' });
+  assert.equal(code('tester', 'thread.messages', { thread: H }), 'thread-not-owned');
+});
+
 // The 3l→3m step. A 3l store from fixtures/schema-3l.sql, with one row in each thread table.
 const AT = '2026-10-22T00:00:00.000Z';
 const ddl3l = readFileSync(here('./fixtures/schema-3l.sql'), 'utf8');