diff --git a/hive-c0re/assets/app.js b/hive-c0re/assets/app.js
index 5c97489..c367693 100644
--- a/hive-c0re/assets/app.js
+++ b/hive-c0re/assets/app.js
@@ -164,6 +164,21 @@
     if (!(f instanceof HTMLFormElement) || !f.hasAttribute('data-async')) return;
     e.preventDefault();
     if (f.dataset.confirm && !confirm(f.dataset.confirm)) return;
+    if (f.dataset.prompt) {
+      const ans = prompt(f.dataset.prompt, '');
+      if (ans === null) return;  // operator hit Cancel
+      // Drop into a hidden input named after `data-prompt-field` (or
+      // 'note' by default) so the value rides along on the POST.
+      const field = f.dataset.promptField || 'note';
+      let input = f.querySelector(`input[name="${field}"]`);
+      if (!input) {
+        input = document.createElement('input');
+        input.type = 'hidden';
+        input.name = field;
+        f.append(input);
+      }
+      input.value = ans;
+    }
     const btn = f.querySelector('button[type="submit"], button:not([type]), .btn-inline');
     const original = btn ? btn.innerHTML : '';
     if (btn) { btn.disabled = true; btn.innerHTML = '<span class="spinner">◐</span>'; }
@@ -616,11 +631,21 @@
             'new sub-agent — container will be created on approve'),
         );
       }
+      // Deny prompts the operator for an optional reason; the
+      // submit handler stashes it into a hidden `note` input that
+      // rides along on the POST and is surfaced to the manager via
+      // HelperEvent::ApprovalResolved { note }.
+      const denyForm = el('form', {
+        method: 'POST', action: '/deny/' + a.id,
+        class: 'inline', 'data-async': '',
+        'data-prompt': 'reason for denying (optional, sent to manager):',
+      });
+      denyForm.append(el('button', { type: 'submit', class: 'btn btn-deny' }, 'DENY'));
       row.append(
         ' ',
         form('/approve/' + a.id, 'btn-approve', '◆ APPR0VE'),
         ' ',
-        form('/deny/' + a.id, 'btn-deny', 'DENY'),
+        denyForm,
       );
       li.append(row);
       if (a.diff_html) {
diff --git a/hive-c0re/src/actions.rs b/hive-c0re/src/actions.rs
index 1b54efc..00318fd 100644
--- a/hive-c0re/src/actions.rs
+++ b/hive-c0re/src/actions.rs
@@ -178,17 +178,17 @@ pub async fn destroy(coord: &Coordinator, name: &str, purge: bool) -> Result<()>
     Ok(())
 }
 
-pub fn deny(coord: &Coordinator, id: i64) -> Result<()> {
+pub fn deny(coord: &Coordinator, id: i64, note: Option<&str>) -> Result<()> {
     let approval = coord.approvals.get(id)?;
-    coord.approvals.mark_denied(id)?;
-    tracing::info!(%id, "approval denied");
+    coord.approvals.mark_denied(id, note)?;
+    tracing::info!(%id, note, "approval denied");
     if let Some(a) = approval {
         coord.notify_manager(&HelperEvent::ApprovalResolved {
             id: a.id,
             agent: a.agent,
             commit_ref: a.commit_ref,
             status: ApprovalStatus::Denied,
-            note: None,
+            note: note.map(String::from),
         });
     }
     Ok(())
diff --git a/hive-c0re/src/approvals.rs b/hive-c0re/src/approvals.rs
index d3e659b..fbc06ab 100644
--- a/hive-c0re/src/approvals.rs
+++ b/hive-c0re/src/approvals.rs
@@ -142,12 +142,12 @@ impl Approvals {
         })
     }
 
-    pub fn mark_denied(&self, id: i64) -> Result<()> {
+    pub fn mark_denied(&self, id: i64, note: Option<&str>) -> Result<()> {
         let conn = self.conn.lock().unwrap();
         let affected = conn.execute(
-            "UPDATE approvals SET status = 'denied', resolved_at = ?1
-               WHERE id = ?2 AND status = 'pending'",
-            params![now_unix(), id],
+            "UPDATE approvals SET status = 'denied', resolved_at = ?1, note = ?2
+               WHERE id = ?3 AND status = 'pending'",
+            params![now_unix(), note, id],
         )?;
         if affected == 0 {
             bail!("approval {id} not pending");
diff --git a/hive-c0re/src/dashboard.rs b/hive-c0re/src/dashboard.rs
index 46657a7..ceaafa1 100644
--- a/hive-c0re/src/dashboard.rs
+++ b/hive-c0re/src/dashboard.rs
@@ -410,8 +410,23 @@ async fn post_approve(State(state): State<AppState>, AxumPath(id): AxumPath<i64>
     }
 }
 
-async fn post_deny(State(state): State<AppState>, AxumPath(id): AxumPath<i64>) -> Response {
-    match actions::deny(&state.coord, id) {
+#[derive(Deserialize, Default)]
+struct DenyForm {
+    #[serde(default)]
+    note: Option<String>,
+}
+
+async fn post_deny(
+    State(state): State<AppState>,
+    AxumPath(id): AxumPath<i64>,
+    Form(form): Form<DenyForm>,
+) -> Response {
+    let note = form
+        .note
+        .as_deref()
+        .map(str::trim)
+        .filter(|s| !s.is_empty());
+    match actions::deny(&state.coord, id, note) {
         Ok(()) => Redirect::to("/").into_response(),
         Err(e) => error_response(&format!("deny {id} failed: {e:#}")),
     }
diff --git a/hive-c0re/src/server.rs b/hive-c0re/src/server.rs
index 9ce4df1..80f3551 100644
--- a/hive-c0re/src/server.rs
+++ b/hive-c0re/src/server.rs
@@ -144,7 +144,7 @@ async fn dispatch(req: &HostRequest, coord: Arc<Coordinator>) -> HostResponse {
                 HostResponse::success()
             }
             HostRequest::Deny { id } => {
-                actions::deny(&coord, *id)?;
+                actions::deny(&coord, *id, None)?;
                 HostResponse::success()
             }
         })