diff --git a/codex-rs/message-board/src/local.rs b/codex-rs/message-board/src/local.rs
index 6d580e6fa6..4e8bf86177 100644
--- a/codex-rs/message-board/src/local.rs
+++ b/codex-rs/message-board/src/local.rs
@@ -52,6 +52,7 @@ mod paging;
 mod pool;
 mod queries;
 pub(crate) mod setup;
+mod subscriptions;
 
 #[cfg(test)]
 #[path = "local/pools_tests.rs"]
@@ -422,27 +423,8 @@ impl LocalAgentMessageBoard {
             .map(Uuid::parse_str)
             .transpose()
             .map_err(storage_error)?;
-        // Keep active subscriptions readable by older binaries. Opt-outs only
-        // prevent implicit subscription when this agent participates again.
-        let statements = match request.change {
-            SubscriptionChange::Subscribe => [
-                "DELETE FROM subscription_opt_outs WHERE board=? AND target=? AND agent=?",
-                "INSERT OR IGNORE INTO subscriptions(board,target,agent) VALUES(?,?,?)",
-            ],
-            SubscriptionChange::Unsubscribe => [
-                "DELETE FROM subscriptions WHERE board=? AND target=? AND agent=?",
-                "INSERT OR IGNORE INTO subscription_opt_outs(board,target,agent) VALUES(?,?,?)",
-            ],
-        };
-        for statement in statements {
-            sqlx::query(statement)
-                .bind(self.identity.to_string())
-                .bind(target_key(&request.target)?)
-                .bind(target_agent.to_string())
-                .execute(&mut *tx)
-                .await
-                .map_err(storage_error)?;
-        }
+        self.change_subscription(&mut tx, &request.target, target_agent, request.change)
+            .await?;
         tx.commit().await.map_err(storage_error)?;
         Ok(SubscriptionState {
             channel_name: channel,
diff --git a/codex-rs/message-board/src/local/subscriptions.rs b/codex-rs/message-board/src/local/subscriptions.rs
new file mode 100644
index 0000000000..74ff80d9a9
--- /dev/null
+++ b/codex-rs/message-board/src/local/subscriptions.rs
@@ -0,0 +1,95 @@
+//! Atomic replacement and discovery of a caller's own channel subscriptions.
+//! Thread subscriptions and other agents are unaffected; no notifications are emitted.
+
+use super::LocalAgentMessageBoard;
+use super::connection::Access;
+use super::invalid;
+use super::storage_error;
+use super::target_key;
+use super::validate_channel;
+use crate::SubscriptionChange;
+use crate::SubscriptionTarget;
+use codex_protocol::ThreadId;
+use codex_protocol::error::Result;
+use sqlx::Sqlite;
+use sqlx::Transaction;
+use std::collections::BTreeMap;
+
+impl LocalAgentMessageBoard {
+    /// Atomically replaces the caller's membership in the supplied channels.
+    /// Channels outside this set keep their subscriptions and opt-outs.
+    /// A read-only live connection permits this self-only operation; a fixed view does not.
+    pub async fn set_subscriptions(
+        &self,
+        caller: ThreadId,
+        channels: &BTreeMap<&str, SubscriptionChange>,
+    ) -> Result<()> {
+        if self.mode.view().is_some() {
+            Access::ReadOnly.require_write(self.identity, "board.manage_subscriptions")?;
+        }
+        self.host.agent_path(caller).await?;
+        for channel in channels.keys() {
+            validate_channel(channel)?;
+        }
+        let names =
+            serde_json::to_string(&channels.keys().collect::<Vec<_>>()).map_err(storage_error)?;
+        let mut tx = self.begin_write().await?;
+        let membership = sqlx::query_as::<_, (String, bool)>(
+            "SELECT c.name, EXISTS(
+                SELECT 1 FROM subscriptions AS s WHERE s.board=c.board
+                AND s.target=json_object('Channel',c.name) AND s.agent=?
+             ) FROM channels AS c WHERE c.board=? AND c.name IN (SELECT value FROM json_each(?))",
+        )
+        .bind(caller.to_string())
+        .bind(self.identity.to_string())
+        .bind(names)
+        .fetch_all(&mut *tx)
+        .await
+        .map_err(storage_error)?;
+        if membership.len() != channels.len() {
+            return Err(invalid("channel not found in this board"));
+        }
+        for (name, subscribed) in membership {
+            let change = channels[name.as_str()];
+            if subscribed == (change == SubscriptionChange::Subscribe) {
+                continue;
+            }
+            self.change_subscription(&mut tx, &SubscriptionTarget::Channel(name), caller, change)
+                .await?;
+        }
+        tx.commit().await.map_err(storage_error)
+    }
+
+    /// Update explicit membership and its matching implicit-subscription opt-out atomically.
+    pub(super) async fn change_subscription(
+        &self,
+        tx: &mut Transaction<'_, Sqlite>,
+        target: &SubscriptionTarget,
+        agent: ThreadId,
+        change: SubscriptionChange,
+    ) -> Result<()> {
+        let board = self.identity.to_string();
+        let target = target_key(target)?;
+        let agent = agent.to_string();
+        let statements = match change {
+            SubscriptionChange::Subscribe => [
+                "DELETE FROM subscription_opt_outs WHERE board=? AND target=? AND agent=?",
+                "INSERT OR IGNORE INTO subscriptions(board,target,agent) VALUES(?,?,?)",
+            ],
+            SubscriptionChange::Unsubscribe => [
+                "DELETE FROM subscriptions WHERE board=? AND target=? AND agent=?",
+                "INSERT OR IGNORE INTO subscription_opt_outs(board,target,agent) VALUES(?,?,?)",
+            ],
+        };
+        for statement in statements {
+            sqlx::query(statement)
+                .bind(&board)
+                .bind(&target)
+                .bind(&agent)
+                .execute(&mut **tx)
+                .await
+                .map_err(storage_error)?;
+        }
+        Ok(())
+    }
+}
diff --git a/codex-rs/message-board/tests/local_board.rs b/codex-rs/message-board/tests/local_board.rs
index 4b1d8b6f09..e273f7c2e8 100644
--- a/codex-rs/message-board/tests/local_board.rs
+++ b/codex-rs/message-board/tests/local_board.rs
@@ -1939,6 +1939,89 @@ async fn silent_appends_preserve_evidence_and_explicit_subscriptions()
     Ok(())
 }
 
+#[tokio::test]
+async fn bulk_subscriptions_are_atomic_and_scoped_to_the_caller_and_supplied_channels() -> Result<()>
+{
+    use SubscriptionChange::Subscribe;
+    use SubscriptionChange::Unsubscribe;
+    use std::collections::BTreeMap;
+
+    let dir = tempfile::tempdir()?;
+    let sqlite = SqliteConfig::new_for_testing(dir.path().to_path_buf().try_into().unwrap());
+    let owner = ThreadId::new();
+    let reviewer = ThreadId::new();
+    let host = Arc::new(Host {
+        clock: AtomicI64::default(),
+        fail_clock: AtomicBool::default(),
+        agent_path_calls: AtomicUsize::default(),
+        members: [
+            (owner, AgentPath::root()),
+            (reviewer, AgentPath::root().join("reviewer").unwrap()),
+        ]
+        .into(),
+        active: AtomicBool::new(true),
+        fail_notifications: AtomicBool::default(),
+        notifications: Mutex::default(),
+    });
+    let board = LocalBoard::new(sqlite, owner.into());
+    let writer = board.read_write().open(host.clone()).await?;
+    let reader = board.read_only().open(host.clone()).await?;
+    for name in ["build", "release"] {
+        writer
+            .create_channel(
+                owner,
+                CreateChannelRequest {
+                    channel_name: name.into(),
+                    description: None,
+                    subscription: Subscribe,
+                },
+            )
+            .await?;
+    }
+    reader
+        .set_subscriptions(
+            reviewer,
+            &BTreeMap::from([("build", Subscribe), ("release", Subscribe)]),
+        )
+        .await?;
+    let both = vec!["build".to_owned(), "release".to_owned()];
+    assert!(
+        reader
+            .set_subscriptions(
+                reviewer,
+                &BTreeMap::from([("build", Unsubscribe), ("missing", Subscribe)])
+            )
+            .await
+            .is_err()
+    );
+    assert_eq!(
+        reader
+            .subscribed_channels(reviewer, PageRequest::default())
+            .await?
+            .results,
+        both
+    );
+    reader
+        .set_subscriptions(reviewer, &BTreeMap::from([("build", Unsubscribe)]))
+        .await?;
+    assert_eq!(
+        reader
+            .subscribed_channels(reviewer, PageRequest::default())
+            .await?
+            .results,
+        vec!["release".to_owned()]
+    );
+    assert_eq!(
+        reader
+            .subscribed_channels(owner, PageRequest::default())
+            .await?
+            .results,
+        both
+    );
+    assert!(host.notifications.lock().unwrap().is_empty());
+    Ok(())
+}
+
 #[tokio::test]
 async fn local_board_setup_survives_reopen() -> Result<()> {
     use serde_json::json;