diff --git a/agents/gizmoduck/work/queue-271/BUILD.md b/agents/gizmoduck/work/queue-271/BUILD.md
index 14a057044..e85ef1b2a 100644
--- a/agents/gizmoduck/work/queue-271/BUILD.md
+++ b/agents/gizmoduck/work/queue-271/BUILD.md
@@ -29,7 +29,12 @@ Answer, the operation envelope:
   "state": "clearing", "start": null, "refusal": null, "at": "..." }
 ```
 
-- `successor` is bound when the request is accepted, before any asynchronous work.
+- `successor` is bound when the request is accepted, before any asynchronous work. It is a
+  lowercase UUID, `xxxxxxxx-xxxx-8xxx-Vxxx-xxxxxxxxxxxx` with V one of `8`, `9`, `a`, `b` (RFC 9562
+  version 8, variant 10). It's the first 32 hex digits of sha256(business, thread, old session, op)
+  with those two nibbles set. It matches the UUID test every session selector uses
+  (cli/src/thread.mjs:41), so 264a's selectors and deep links take it unchanged (Huey's question,
+  gizmoduck-0274).
 - `state`:
   - `clearing`: accepted. Sends and launches to the old session are fenced, and the drain or stop
     is in progress.
@@ -139,8 +144,9 @@ alone can't show that no child is running.
    - Check owner and grant (the `session.create` path), the revision, and that processing isn't
      halted.
    - Bind the successor before any async work:
-     - The id is deterministic, from a sha256 of (business, thread, old session, op), shaped to
-       `ID_PATTERN` (vocabulary.mjs:199).
+     - The id is deterministic, from a sha256 of (business, thread, old session, op), shaped as a
+       lowercase version 8 UUID (the contract above). 264a's ids are UUIDs, and every selector
+       checks the UUID shape, so draft 2's `ID_PATTERN` shape is replaced.
      - The name is `<old name>-N`, with N the next free number in that thread. If a user already
        made a session called `<old>-N`, the next free N is taken.
      - Both go on the `requested` row, so a repeat of the op returns the same id and name.
diff --git a/packages/bus/schema.sql b/packages/bus/schema.sql
index 59d1c80a5..ada6e8ca9 100644
--- a/packages/bus/schema.sql
+++ b/packages/bus/schema.sql
@@ -478,3 +478,40 @@ CREATE TABLE gitea_grants (
   PRIMARY KEY (business, agent),
   FOREIGN KEY (business, agent) REFERENCES gitea_users(business, agent)
 ) STRICT;
+CREATE TABLE session_ops (
+  seq INTEGER PRIMARY KEY AUTOINCREMENT,
+  at TEXT NOT NULL,
+  business TEXT NOT NULL,
+  thread TEXT NOT NULL REFERENCES threads(id),
+  session TEXT NOT NULL REFERENCES sessions(id),
+  op TEXT NOT NULL,
+  stage TEXT NOT NULL CHECK (stage IN ('requested','drained','uncertain','exited','retired','failed','cancelled','start-held','start-started','start-refused')),
+  attempt INTEGER NOT NULL CHECK (CASE WHEN stage GLOB 'start-*' THEN attempt >= 1 ELSE attempt = 0 END),
+  work_attempt INTEGER CHECK (work_attempt IS NULL OR (stage GLOB 'start-*' AND work_attempt >= 1)),
+  successor TEXT NOT NULL,
+  successor_name TEXT NOT NULL,
+  run TEXT,
+  generation INTEGER CHECK (generation IS NULL OR generation >= 1),
+  digest TEXT,
+  refusal TEXT,
+  UNIQUE (thread, op, stage, attempt)
+) STRICT;
+CREATE TABLE message_cancels (
+  seq INTEGER PRIMARY KEY AUTOINCREMENT,
+  at TEXT NOT NULL,
+  message TEXT NOT NULL UNIQUE REFERENCES messages(id),
+  session TEXT NOT NULL REFERENCES sessions(id),
+  op TEXT NOT NULL
+) STRICT;
+CREATE INDEX session_ops_session ON session_ops (session, seq);
+CREATE TRIGGER session_ops_no_update BEFORE UPDATE ON session_ops BEGIN SELECT RAISE(ABORT, 'session_ops is append-only'); END;
+CREATE TRIGGER session_ops_no_delete BEFORE DELETE ON session_ops BEGIN SELECT RAISE(ABORT, 'session_ops is append-only'); END;
+CREATE TRIGGER session_ops_no_replace BEFORE INSERT ON session_ops WHEN EXISTS (SELECT 1 FROM session_ops WHERE seq = NEW.seq) BEGIN SELECT RAISE(ABORT, 'session_ops is append-only'); END;
+CREATE TRIGGER session_ops_one_open BEFORE INSERT ON session_ops
+  WHEN NEW.stage = 'requested' AND EXISTS (SELECT 1 FROM session_ops o WHERE o.session = NEW.session
+    AND o.seq = (SELECT max(seq) FROM session_ops WHERE thread = o.thread AND op = o.op)
+    AND o.stage IN ('requested','drained','uncertain','exited'))
+  BEGIN SELECT RAISE(ABORT, 'session has an open clear'); END;
+CREATE TRIGGER message_cancels_no_update BEFORE UPDATE ON message_cancels BEGIN SELECT RAISE(ABORT, 'message_cancels is append-only'); END;
+CREATE TRIGGER message_cancels_no_delete BEFORE DELETE ON message_cancels BEGIN SELECT RAISE(ABORT, 'message_cancels is append-only'); END;
+CREATE TRIGGER message_cancels_no_replace BEFORE INSERT ON message_cancels WHEN EXISTS (SELECT 1 FROM message_cancels WHERE seq = NEW.seq) BEGIN SELECT RAISE(ABORT, 'message_cancels is append-only'); END;
diff --git a/packages/bus/src/migrations/3l-3m.sql b/packages/bus/src/migrations/3l-3m.sql
new file mode 100644
index 000000000..a4fd9da8b
--- /dev/null
+++ b/packages/bus/src/migrations/3l-3m.sql
@@ -0,0 +1,40 @@
+-- Row 271 (264d, #1776, T1 item 7 D7/D8): clear context. session_ops is the clear journal, one row
+-- per stage, and message_cancels holds a receipt for each message a clear cancelled. Only new
+-- tables, an index and their triggers.
+CREATE TABLE session_ops (
+  seq INTEGER PRIMARY KEY AUTOINCREMENT,
+  at TEXT NOT NULL,
+  business TEXT NOT NULL,
+  thread TEXT NOT NULL REFERENCES threads(id),
+  session TEXT NOT NULL REFERENCES sessions(id),
+  op TEXT NOT NULL,
+  stage TEXT NOT NULL CHECK (stage IN ('requested','drained','uncertain','exited','retired','failed','cancelled','start-held','start-started','start-refused')),
+  attempt INTEGER NOT NULL CHECK (CASE WHEN stage GLOB 'start-*' THEN attempt >= 1 ELSE attempt = 0 END),
+  work_attempt INTEGER CHECK (work_attempt IS NULL OR (stage GLOB 'start-*' AND work_attempt >= 1)),
+  successor TEXT NOT NULL,
+  successor_name TEXT NOT NULL,
+  run TEXT,
+  generation INTEGER CHECK (generation IS NULL OR generation >= 1),
+  digest TEXT,
+  refusal TEXT,
+  UNIQUE (thread, op, stage, attempt)
+) STRICT;
+CREATE TABLE message_cancels (
+  seq INTEGER PRIMARY KEY AUTOINCREMENT,
+  at TEXT NOT NULL,
+  message TEXT NOT NULL UNIQUE REFERENCES messages(id),
+  session TEXT NOT NULL REFERENCES sessions(id),
+  op TEXT NOT NULL
+) STRICT;
+CREATE INDEX session_ops_session ON session_ops (session, seq);
+CREATE TRIGGER session_ops_no_update BEFORE UPDATE ON session_ops BEGIN SELECT RAISE(ABORT, 'session_ops is append-only'); END;
+CREATE TRIGGER session_ops_no_delete BEFORE DELETE ON session_ops BEGIN SELECT RAISE(ABORT, 'session_ops is append-only'); END;
+CREATE TRIGGER session_ops_no_replace BEFORE INSERT ON session_ops WHEN EXISTS (SELECT 1 FROM session_ops WHERE seq = NEW.seq) BEGIN SELECT RAISE(ABORT, 'session_ops is append-only'); END;
+CREATE TRIGGER session_ops_one_open BEFORE INSERT ON session_ops
+  WHEN NEW.stage = 'requested' AND EXISTS (SELECT 1 FROM session_ops o WHERE o.session = NEW.session
+    AND o.seq = (SELECT max(seq) FROM session_ops WHERE thread = o.thread AND op = o.op)
+    AND o.stage IN ('requested','drained','uncertain','exited'))
+  BEGIN SELECT RAISE(ABORT, 'session has an open clear'); END;
+CREATE TRIGGER message_cancels_no_update BEFORE UPDATE ON message_cancels BEGIN SELECT RAISE(ABORT, 'message_cancels is append-only'); END;
+CREATE TRIGGER message_cancels_no_delete BEFORE DELETE ON message_cancels BEGIN SELECT RAISE(ABORT, 'message_cancels is append-only'); END;
+CREATE TRIGGER message_cancels_no_replace BEFORE INSERT ON message_cancels WHEN EXISTS (SELECT 1 FROM message_cancels WHERE seq = NEW.seq) BEGIN SELECT RAISE(ABORT, 'message_cancels is append-only'); END;
diff --git a/packages/bus/src/store.mjs b/packages/bus/src/store.mjs
index cad4c4272..8ce7fc7fe 100644
--- a/packages/bus/src/store.mjs
+++ b/packages/bus/src/store.mjs
@@ -13,8 +13,8 @@ import { join, isAbsolute } from 'node:path';
 import { createHash } from 'node:crypto';
 
 const ddl = readFileSync(new URL('../schema.sql', import.meta.url), 'utf8');
-export const SCHEMA_SHA256 = 'cd68512212ce8bf8f5631138b2e63a340fa7b940088430649bb7784af7df162a';
-export const SCHEMA_VERSION = '3l';
+export const SCHEMA_SHA256 = '129a76db0fe9973cdea5a87f274941b4111c86730fba8a0cbe16e61a534525d0';
+export const SCHEMA_VERSION = '3m';
 // Ordered, named offline steps. New schema changes append a step and keep prior DDL pinned.
 const legacyDDL = readFileSync(new URL('./migrations/3b.sql', import.meta.url), 'utf8');
 const LEGACY_SHA256 = '179ffe356d4ff19a49b5ebad39b6c6bfd7771deb8e1b7c55b5e746f039d69e65';
@@ -72,6 +72,11 @@ const migrations = [{
   from: '3k',
   to: '3l',
   sql: readFileSync(new URL('./migrations/3k-3l.sql', import.meta.url), 'utf8'),
+}, {
+  // Row 271 (#1776): clear context. The clear journal and the cancelled-message receipts. Only new tables.
+  from: '3l',
+  to: '3m',
+  sql: readFileSync(new URL('./migrations/3l-3m.sql', import.meta.url), 'utf8'),
 }];
 const timedTables = [
   'events',
@@ -89,6 +94,8 @@ const timedTables = [
   'thread_opens',
   'instance_names',
   'usage_records',
+  'session_ops',
+  'message_cancels',
 ];
 const hex = (value) => createHash('sha256').update(value).digest('hex');
 if (hex(ddl) !== SCHEMA_SHA256) throw Error('schema-source-mismatch');