diff --git a/crates/daemon/assets/index.html b/crates/daemon/assets/index.html
index ffefbd8d..a94a14aa 100644
--- a/crates/daemon/assets/index.html
+++ b/crates/daemon/assets/index.html
@@ -3859,7 +3859,7 @@
                 aria-label="new session">+ new session</button>
       </div>
       <span class="session-list-sr-label">sessions</span>
-      <aside class="session-list" id="sessionList">
+      <aside class="session-list" id="sessionList" role="tree" aria-label="sessions">
         <div class="empty">connecting…</div>
       </aside>
       <!--
@@ -7600,7 +7600,12 @@ <h2 id="serviceViewTitle"></h2>
 
 function focusListRow(row) {
   if (!row) return;
-  row.setAttribute("tabindex", "-1");
+  // Roving tabindex: the row that holds the list caret is the list's single
+  // Tab stop, so leaving and re-Tabbing returns to where the user was.
+  for (const other of listFocusRows()) {
+    if (other !== row) other.setAttribute("tabindex", "-1");
+  }
+  row.setAttribute("tabindex", "0");
   row.focus();
   row.scrollIntoView({ block: "nearest" });
 }
@@ -7612,6 +7617,24 @@ <h2 id="serviceViewTitle"></h2>
     : null;
 }
 
+/** Keep exactly one list row in the tab order (issue #1075): the row that
+ *  holds the list caret when focus is inside the list, else the selected
+ *  row, else the first row. Tab from outside therefore reaches the list
+ *  exactly once, and the arrow keys take over from there. Runs after every
+ *  re-render because rebuilt rows come back without a tabindex. */
+function syncListTabStops() {
+  const rows = listFocusRows();
+  if (!rows.length) return;
+  const focused = listFocusedRow();
+  const entry =
+    (focused && rows.includes(focused) ? focused : null) ||
+    sessionListEl.querySelector(".item.active") ||
+    rows[0];
+  for (const row of rows) {
+    row.setAttribute("tabindex", row === entry ? "0" : "-1");
+  }
+}
+
 /** Re-find a list row after a re-render and put the caret back on it. */
 function refocusListRow(rowKey, isService = false) {
   if (!rowKey) return;
@@ -7935,8 +7958,70 @@ <h2 id="serviceViewTitle"></h2>
   });
 }
 
-/** Build a row descriptor: a stable key plus the outer class and inner
- *  HTML. renderSessions() diffs class and inner separately so a pure
+/** Annotate the flat `orderedItems()` list with tree coordinates for
+ *  aria-level / aria-posinset / aria-setsize. Items arrive in DFS order;
+ *  a sibling run is a maximal stretch of rows at one depth uninterrupted
+ *  by a shallower row — the same grouping the indentation shows visually.
+ *  (Group headers, services, and the operator carry no `depth` and count
+ *  as depth 0.) */
+function annotateTreePositions(items) {
+  const stack = []; // stack[d] = the sibling run currently open at depth d
+  const settle = (downTo) => {
+    while (stack.length > downTo) {
+      const run = stack.pop();
+      run.forEach((it, i) => {
+        it.posinset = i + 1;
+        it.setsize = run.length;
+      });
+    }
+  };
+  for (const it of items) {
+    const depth = it.depth ?? 0;
+    settle(depth + 1);
+    while (stack.length <= depth) stack.push([]);
+    stack[depth].push(it);
+    it.level = depth + 1;
+  }
+  settle(0);
+  return items;
+}
+
+/** The row attributes renderSessions() owns. Listed exhaustively so a row
+ *  that changes shape across renders (e.g. loses its children and with them
+ *  aria-expanded) has the stale attribute removed, not left behind. */
+const ROW_ARIA_ATTRS = Object.freeze([
+  "role",
+  "aria-selected",
+  "aria-expanded",
+  "aria-level",
+  "aria-posinset",
+  "aria-setsize",
+]);
+
+function rowTreePositionAria(item) {
+  const aria = {};
+  if (item.level) aria["aria-level"] = String(item.level);
+  if (item.posinset) aria["aria-posinset"] = String(item.posinset);
+  if (item.setsize) aria["aria-setsize"] = String(item.setsize);
+  return aria;
+}
+
+function applyRowAria(node, aria) {
+  for (const name of ROW_ARIA_ATTRS) {
+    const v = aria ? aria[name] : undefined;
+    if (v == null) node.removeAttribute(name);
+    else node.setAttribute(name, v);
+  }
+}
+
+function rowAriaSignature(aria) {
+  return ROW_ARIA_ATTRS.map((name) => (aria && aria[name]) ?? "").join("|");
+}
+
+/** Build a row descriptor: a stable key plus the outer class, inner HTML,
+ *  and ARIA attributes (issue #1075: the list is a `tree` — groups nest
+ *  sessions, sessions nest subagents/forks — so rows are `treeitem`s).
+ *  renderSessions() diffs class, inner, and aria separately so a pure
  *  selection change (class only) never rebuilds a row's status element. */
 function sessionRowDescriptor(item) {
   const depthClass = " depth-" + Math.min(item.depth ?? 0, 4);
@@ -7947,6 +8032,11 @@ <h2 id="serviceViewTitle"></h2>
       datasetKey: "archivedSection",
       datasetVal: item.section,
       className: "archived-row" + depthClass,
+      aria: {
+        role: "treeitem",
+        "aria-expanded": item.expanded ? "true" : "false",
+        ...rowTreePositionAria(item),
+      },
       inner:
         `<span class="archived-glyph">${glyph}</span>` +
         `<span class="archived-label">${item.count} archived</span>`,
@@ -7960,6 +8050,11 @@ <h2 id="serviceViewTitle"></h2>
       datasetKey: "groupId",
       datasetVal: g.id,
       className: "group-header",
+      aria: {
+        role: "treeitem",
+        "aria-expanded": g.collapsed ? "false" : "true",
+        ...rowTreePositionAria(item),
+      },
       inner:
         `<span class="group-glyph">${glyph}</span>` +
         `<span class="group-name">${escape(g.name || "(unnamed)")}</span>` +
@@ -7976,6 +8071,11 @@ <h2 id="serviceViewTitle"></h2>
       datasetKey: "serviceName",
       datasetVal: service.name,
       className: "item is-service" + active + paused,
+      aria: {
+        role: "treeitem",
+        "aria-selected": active ? "true" : "false",
+        ...rowTreePositionAria(item),
+      },
       inner:
         `<div class="title-row">` +
         `<span class="disclosure"></span>` +
@@ -7996,6 +8096,11 @@ <h2 id="serviceViewTitle"></h2>
       datasetKey: "id",
       datasetVal: s.id,
       className: "item is-operator" + active,
+      aria: {
+        role: "treeitem",
+        "aria-selected": active ? "true" : "false",
+        ...rowTreePositionAria(item),
+      },
       inner:
         `<div class="title-row">` +
         `<span class="disclosure"></span>` +
@@ -8027,6 +8132,16 @@ <h2 id="serviceViewTitle"></h2>
     key: "s:" + s.id,
     datasetKey: "id",
     datasetVal: s.id,
+    aria: {
+      role: "treeitem",
+      "aria-selected": active ? "true" : "false",
+      // Only rows that actually have children advertise expandability; a
+      // leaf with aria-expanded would announce as a collapsed empty branch.
+      ...(item.hasChildren
+        ? { "aria-expanded": item.childrenExpanded ? "true" : "false" }
+        : null),
+      ...rowTreePositionAria(item),
+    },
     className:
       "item" + depthClass + active +
       (s.kind === "subagent" ? " is-subagent" : "") +
@@ -8057,7 +8172,7 @@ <h2 id="serviceViewTitle"></h2>
   }
   bindSessionListClicks();
   bindSessionListDrag();
-  const items = orderedItems();
+  const items = annotateTreePositions(orderedItems());
   if (!items.length) {
     const only = sessionListEl.firstElementChild;
     if (!only || sessionListEl.children.length !== 1 || !only.classList.contains("empty")) {
@@ -8100,11 +8215,17 @@ <h2 id="serviceViewTitle"></h2>
       node.innerHTML = d.inner;
       node.__isig = d.inner;
     }
+    const asig = rowAriaSignature(d.aria);
+    if (node.__asig !== asig) {
+      applyRowAria(node, d.aria);
+      node.__asig = asig;
+    }
     const ref = prev ? prev.nextSibling : sessionListEl.firstChild;
     if (ref !== node) sessionListEl.insertBefore(node, ref);
     prev = node;
   }
   for (const node of existing.values()) node.remove();
+  syncListTabStops();
   if (state.currentServiceName) renderServiceView();
   refreshSessionActions();
   renderLineageSection();
@@ -18960,14 +19081,15 @@ <h2 id="serviceViewTitle"></h2>
     return;
   }
   if (!isSessionListVisible()) setSessionListVisible(true);
+  // Enter through the roving Tab stop, i.e. wherever the list caret last
+  // was — the same row a Tab press would land on. (The old query looked
+  // for `.item.selected`, a class no row ever carries, so entry always
+  // fell back to the first session row.)
   const selected =
-    sessionListEl.querySelector(".item.selected") || sessionListEl.querySelector(".item[data-id]");
-  if (selected) {
-    selected.setAttribute("tabindex", "-1");
-    selected.focus();
-  } else {
-    sessionListEl.focus();
-  }
+    sessionListEl.querySelector('[tabindex="0"]') ||
+    sessionListEl.querySelector(".item.active") ||
+    sessionListEl.querySelector(".item[data-id]");
+  if (selected) focusListRow(selected);
 }
 
 /**
diff --git a/crates/e2e/tests/web_smoke.rs b/crates/e2e/tests/web_smoke.rs
index a5418c25..f5609904 100644
--- a/crates/e2e/tests/web_smoke.rs
+++ b/crates/e2e/tests/web_smoke.rs
@@ -3040,6 +3040,131 @@ async fn web_client_loads_and_websocket_connects() {
         "visible row text should not spell out the status: {status_icons:?}"
     );
 
+    // Issue #1075: the session list is an ARIA tree — rows are treeitems
+    // carrying selection, expansion, and tree-coordinate state, and exactly
+    // one row (the selected one) is the list's Tab entry point.
+    let list_aria: serde_json::Value = page
+        .evaluate(
+            r#"
+            (() => {
+              const saved = {
+                currentId: state.currentId,
+                sessions: state.sessions,
+                groups: state.groups,
+                services: state.services,
+              };
+              try {
+                state.currentId = 's-child';
+                state.services = [{ name: 'proxy', harness: 'shell', position: 0 }];
+                state.groups = [
+                  { id: 'g-open', name: 'Open', collapsed: false, position: 0 },
+                  { id: 'g-shut', name: 'Shut', collapsed: true, position: 1 },
+                ];
+                state.sessions = [
+                  { id: 's-parent', title: 'Parent', harness: 'shell', state: 'running', kind: 'user', position: 0 },
+                  { id: 's-child', title: 'Child', harness: 'smith', state: 'running', kind: 'subagent', parent_session_id: 's-parent', position: 0 },
+                  { id: 's-solo', title: 'Solo', harness: 'shell', state: 'running', kind: 'user', position: 1 },
+                  { id: 's-member', title: 'Member', harness: 'shell', state: 'running', kind: 'user', group_id: 'g-open', position: 0 },
+                ];
+                renderSessions();
+                const list = document.getElementById('sessionList');
+                const attrsOf = (el) => el ? {
+                  role: el.getAttribute('role'),
+                  selected: el.getAttribute('aria-selected'),
+                  expanded: el.getAttribute('aria-expanded'),
+                  level: el.getAttribute('aria-level'),
+                  pos: el.getAttribute('aria-posinset'),
+                  size: el.getAttribute('aria-setsize'),
+                  tab: el.getAttribute('tabindex'),
+                } : null;
+                return {
+                  listRole: list.getAttribute('role'),
+                  listLabel: list.getAttribute('aria-label'),
+                  service: attrsOf(list.querySelector('[data-service-name="proxy"]')),
+                  parent: attrsOf(list.querySelector('[data-id="s-parent"]')),
+                  child: attrsOf(list.querySelector('[data-id="s-child"]')),
+                  solo: attrsOf(list.querySelector('[data-id="s-solo"]')),
+                  openGroup: attrsOf(list.querySelector('[data-group-id="g-open"]')),
+                  shutGroup: attrsOf(list.querySelector('[data-group-id="g-shut"]')),
+                  member: attrsOf(list.querySelector('[data-id="s-member"]')),
+                  tabStops: list.querySelectorAll('[tabindex="0"]').length,
+                  entryId: list.querySelector('[tabindex="0"]')?.dataset.id || '',
+                };
+              } finally {
+                state.currentId = saved.currentId;
+                state.sessions = saved.sessions;
+                state.groups = saved.groups;
+                state.services = saved.services;
+                renderSessions();
+              }
+            })()
+            "#,
+        )
+        .await
+        .expect("evaluate session list aria")
+        .into_value::<serde_json::Value>()
+        .expect("json object");
+    assert_eq!(list_aria["listRole"], "tree");
+    assert_eq!(list_aria["listLabel"], "sessions");
+    // Top level (level 1) is service + two top sessions + two group headers.
+    assert_eq!(
+        list_aria["service"],
+        serde_json::json!({
+            "role": "treeitem", "selected": "false", "expanded": null,
+            "level": "1", "pos": "1", "size": "5", "tab": "-1"
+        }),
+        "service row aria: {list_aria:?}"
+    );
+    assert_eq!(
+        list_aria["parent"],
+        serde_json::json!({
+            "role": "treeitem", "selected": "false", "expanded": "true",
+            "level": "1", "pos": "2", "size": "5", "tab": "-1"
+        }),
+        "session with expanded subagent children: {list_aria:?}"
+    );
+    // The selected subagent row: nested one level down, selected, and the
+    // list's single Tab stop.
+    assert_eq!(
+        list_aria["child"],
+        serde_json::json!({
+            "role": "treeitem", "selected": "true", "expanded": null,
+            "level": "2", "pos": "1", "size": "1", "tab": "0"
+        }),
+        "selected subagent row aria: {list_aria:?}"
+    );
+    assert_eq!(
+        list_aria["solo"]["expanded"],
+        serde_json::Value::Null,
+        "a leaf session must not advertise expandability: {list_aria:?}"
+    );
+    assert_eq!(
+        list_aria["openGroup"],
+        serde_json::json!({
+            "role": "treeitem", "selected": null, "expanded": "true",
+            "level": "1", "pos": "4", "size": "5", "tab": "-1"
+        }),
+        "expanded group header aria: {list_aria:?}"
+    );
+    assert_eq!(
+        list_aria["shutGroup"]["expanded"],
+        "false",
+        "collapsed group header must announce collapsed: {list_aria:?}"
+    );
+    assert_eq!(
+        list_aria["member"],
+        serde_json::json!({
+            "role": "treeitem", "selected": "false", "expanded": null,
+            "level": "2", "pos": "1", "size": "1", "tab": "-1"
+        }),
+        "group member row aria: {list_aria:?}"
+    );
+    assert_eq!(
+        list_aria["tabStops"], 1,
+        "exactly one row is the roving Tab entry point: {list_aria:?}"
+    );
+    assert_eq!(list_aria["entryId"], "s-child");
+
     // Issue #75: pasted image/file clipboard items and very large text
     // are uploaded to the daemon as session attachments, and the prompt
     // receives a compact [#file:...] reference instead of raw bytes/text.