diff --git a/web/src/app.css b/web/src/app.css
index caf9ef0..6eaf533 100644
--- a/web/src/app.css
+++ b/web/src/app.css
@@ -1056,3 +1056,16 @@ table.tbl a.rowlink:hover {
     padding: 12px 14px;
   }
 }
+
+.tbl .chk-col {
+  width: 32px;
+  text-align: center;
+  padding-right: 0;
+}
+.tbl .chk-col input[type='checkbox'] {
+  cursor: pointer;
+}
+.tbl .chk-col input[type='checkbox']:disabled {
+  cursor: not-allowed;
+  opacity: 0.4;
+}
diff --git a/web/src/pages/TaskDetail.tsx b/web/src/pages/TaskDetail.tsx
index a5291d6..1ce3f64 100644
--- a/web/src/pages/TaskDetail.tsx
+++ b/web/src/pages/TaskDetail.tsx
@@ -90,6 +90,7 @@ export function TaskDetail({ id }: { id: number }) {
   const [live, setLive] = useState<Record<number, LiveProgress>>({})
   const [showRuns, setShowRuns] = useState(false)
   const [errorsFor, setErrorsFor] = useState<{ id: number; src_login: string } | null>(null)
+  const [selected, setSelected] = useState<Set<number>>(new Set())
   const fileInputRef = useRef<HTMLInputElement>(null)
 
   function reload() {
@@ -332,7 +333,8 @@ export function TaskDetail({ id }: { id: number }) {
     setBusy('run')
     setError(null)
     try {
-      await runTask(id)
+      const ids = accounts.filter((a) => selected.has(a.id)).map((a) => a.id)
+      await runTask(id, ids.length ? ids : undefined)
     } catch (err) {
       setError(err instanceof Error ? err.message : 'Failed to start run')
     } finally {
@@ -366,7 +368,33 @@ export function TaskDetail({ id }: { id: number }) {
   }
 
   const { task, accounts } = data
-  const allTested = accounts.length > 0 && accounts.every((a) => a.test_src_status === 'ok' && a.test_dst_status === 'ok')
+  const isRunning = task.status === 'running'
+  // A row is selectable only when both connection tests pass and no run is live.
+  const selectableIds = accounts
+    .filter((a) => a.test_src_status === 'ok' && a.test_dst_status === 'ok')
+    .map((a) => a.id)
+  const selectableSet = new Set(selectableIds)
+  // Effective set: the checked accounts, or all accounts when nothing is checked.
+  const effectiveSelected = accounts.filter((a) => selected.has(a.id))
+  const runSet = effectiveSelected.length > 0 ? effectiveSelected : accounts
+  const runReady =
+    runSet.length > 0 && runSet.every((a) => a.test_src_status === 'ok' && a.test_dst_status === 'ok')
+  const allSelectableChecked =
+    selectableIds.length > 0 && selectableIds.every((id) => selected.has(id))
+  const someSelectableChecked = selectableIds.some((id) => selected.has(id))
+
+  function toggleOne(accId: number, checked: boolean) {
+    setSelected((prev) => {
+      const next = new Set(prev)
+      if (checked) next.add(accId)
+      else next.delete(accId)
+      return next
+    })
+  }
+
+  function toggleAll(checked: boolean) {
+    setSelected(checked ? new Set(selectableIds) : new Set())
+  }
   // Prefer live (WS) copied/skipped over the DB values, which only advance per
   // folder — so the summary moves in real time during a large folder.
   const totals = accounts.reduce(
@@ -418,10 +446,20 @@ export function TaskDetail({ id }: { id: number }) {
           <button className="btn" onClick={onTest} disabled={busy !== null || accounts.length === 0}>
             {busy === 'test' ? 'Testing…' : 'Test connections'}
           </button>
-          <button className="btn btn-primary" onClick={onRun} disabled={busy !== null || !allTested || task.status === 'running'}>
-            {busy === 'run' ? 'Starting…' : 'Run migration'}
+          <button className="btn btn-primary" onClick={onRun} disabled={busy !== null || !runReady || isRunning}>
+            {busy === 'run'
+              ? 'Starting…'
+              : effectiveSelected.length > 0
+                ? `Run selected (${effectiveSelected.length})`
+                : 'Run migration'}
           </button>
-          {!allTested && accounts.length > 0 && <span className="hint">run unlocks once every account tests OK on both sides</span>}
+          {!runReady && accounts.length > 0 && (
+            <span className="hint">
+              {effectiveSelected.length > 0
+                ? 'selected accounts must pass both connection tests'
+                : 'run unlocks once every account tests OK on both sides'}
+            </span>
+          )}
         </div>
         <div className="sched-row">
           <label htmlFor="sched">Schedule</label>
@@ -540,6 +578,18 @@ export function TaskDetail({ id }: { id: number }) {
           <table className="tbl">
             <thead>
               <tr>
+                <th className="chk-col">
+                  <input
+                    type="checkbox"
+                    aria-label="Select all accounts"
+                    checked={allSelectableChecked}
+                    ref={(el) => {
+                      if (el) el.indeterminate = !allSelectableChecked && someSelectableChecked
+                    }}
+                    disabled={isRunning || selectableIds.length === 0}
+                    onChange={(e) => toggleAll(e.target.checked)}
+                  />
+                </th>
                 <th>Account</th>
                 <th>Src test</th>
                 <th>Dst test</th>
@@ -554,11 +604,20 @@ export function TaskDetail({ id }: { id: number }) {
             <tbody>
               {accounts.length === 0 ? (
                 <tr className="empty-row">
-                  <td colSpan={9}>no accounts yet — add one or import a CSV above</td>
+                  <td colSpan={10}>no accounts yet — add one or import a CSV above</td>
                 </tr>
               ) : (
                 accounts.map((a) => (
                   <tr key={a.id}>
+                    <td className="chk-col">
+                      <input
+                        type="checkbox"
+                        aria-label={`Select ${a.src_login}`}
+                        checked={selected.has(a.id)}
+                        disabled={isRunning || !selectableSet.has(a.id)}
+                        onChange={(e) => toggleOne(a.id, e.target.checked)}
+                      />
+                    </td>
                     <td>
                       <div className="acct-ident">
                         <span>{a.src_login}</span>