diff --git a/web/oss/src/components/SharedDrawers/SessionDrawer/components/SessionDrawerContent.tsx b/web/oss/src/components/SharedDrawers/SessionDrawer/components/SessionDrawerContent.tsx
index 2bb7320975..606c3c05b5 100644
--- a/web/oss/src/components/SharedDrawers/SessionDrawer/components/SessionDrawerContent.tsx
+++ b/web/oss/src/components/SharedDrawers/SessionDrawer/components/SessionDrawerContent.tsx
@@ -23,7 +23,10 @@ interface TraceDrawerContentProps {
 }
 
 const SessionDrawerContent = ({onClose, onToggleWidth, isExpanded}: TraceDrawerContentProps) => {
-    const [selected, setSelected] = useState<string>("")
+    // Default-select the "Session" root node so the tree opens with a selection
+    // instead of nothing highlighted. The root node's key is always "root", and
+    // selecting it is a no-op in handleSelect (it early-returns for "root").
+    const [selected, setSelected] = useState<string>("root")
     const {isLoading} = useSessionDrawer()
     if (isLoading) {
         return (
diff --git a/web/oss/src/components/pages/observability/components/SessionsTable/components/Cells/SessionIdCell.tsx b/web/oss/src/components/pages/observability/components/SessionsTable/components/Cells/SessionIdCell.tsx
index 0fcd143913..be8dc956e3 100644
--- a/web/oss/src/components/pages/observability/components/SessionsTable/components/Cells/SessionIdCell.tsx
+++ b/web/oss/src/components/pages/observability/components/SessionsTable/components/Cells/SessionIdCell.tsx
@@ -4,7 +4,10 @@ import {Tag} from "antd"
 export const SessionIdCell = ({sessionId}: {sessionId: string}) => {
     return (
         <TooltipWithCopyAction copyText={sessionId || ""} title="Copy session id">
-            <Tag className="font-mono bg-[var(--ag-c-0517290F)] w-fit truncate" bordered={false}>
+            <Tag
+                className="font-mono bg-[var(--ag-c-0517290F)] max-w-full truncate inline-block align-middle"
+                bordered={false}
+            >
                 # {sessionId}
             </Tag>
         </TooltipWithCopyAction>
diff --git a/web/oss/src/components/pages/observability/components/SessionsTable/index.tsx b/web/oss/src/components/pages/observability/components/SessionsTable/index.tsx
index 0d15650646..188b362b27 100644
--- a/web/oss/src/components/pages/observability/components/SessionsTable/index.tsx
+++ b/web/oss/src/components/pages/observability/components/SessionsTable/index.tsx
@@ -2,7 +2,7 @@ import {useCallback, useEffect, useMemo, useState} from "react"
 
 import {InfiniteVirtualTableFeatureShell} from "@agenta/ui/table"
 import type {TableFeaturePagination, TableScopeConfig} from "@agenta/ui/table"
-import {useAtomValue, useSetAtom} from "jotai"
+import {useAtomValue, useSetAtom, useStore} from "jotai"
 import dynamic from "next/dynamic"
 
 import {SessionDrawer} from "@/oss/components/SharedDrawers/SessionDrawer"
@@ -49,6 +49,14 @@ const SessionsTable: React.FC = () => {
         resetSessionPages,
     } = useSessions()
 
+    // The per-session cells (Traces count, First input, metrics, …) read their
+    // data from page-level atoms keyed by session id (e.g. `sessionsSpansAtom`).
+    // Without this, the table mounts its rows inside an isolated Jotai store
+    // (`useIsolatedStore` when no `store` is passed), where those atoms are empty
+    // — so every cell renders 0/"-" even though the data is loaded in the page
+    // store. Sharing the page store lets the cells resolve the real data.
+    const store = useStore()
+
     const isNewUser = useAtomValue(isNewUserAtom)
     const onboardingStorageUserId = useAtomValue(onboardingStorageUserIdAtom)
     const openDrawer = useSetAtom(openSessionDrawerWithUrlAtom)
@@ -111,7 +119,7 @@ const SessionsTable: React.FC = () => {
     const isEmptyState = sessionIds.length === 0 && !isLoading
 
     return (
-        <div className="flex flex-col gap-6">
+        <div className="flex flex-col h-full gap-2 min-h-0">
             <ObservabilityHeader
                 columns={columns}
                 componentType="sessions"
@@ -128,11 +136,11 @@ const SessionsTable: React.FC = () => {
                 <EmptySessions showOnboarding={showOnboarding} />
             ) : (
                 <InfiniteVirtualTableFeatureShell<SessionRow>
+                    store={store}
                     tableScope={tableScope}
                     columns={columns}
                     rowKey="session_id"
                     pagination={pagination}
-                    autoHeight={false}
                     resizableColumns
                     enableExport={false}
                     useSettingsDropdown={false}
diff --git a/web/oss/src/state/newObservability/atoms/queries.ts b/web/oss/src/state/newObservability/atoms/queries.ts
index 29b74ee98c..c63e3c1d85 100644
--- a/web/oss/src/state/newObservability/atoms/queries.ts
+++ b/web/oss/src/state/newObservability/atoms/queries.ts
@@ -509,15 +509,18 @@ export const sessionTraceCountAtomFamily = atomFamily((sessionId: string) =>
     }),
 )
 
-// Sorted traces are required for time-based metrics (Start/End/Duration)
-// We memoize this to avoid re-sorting for every time-related cell
+// Sorted traces are required for time-based metrics (Start/End/Duration) and for
+// the First input / Last output cells. Sort by `start_time` (falling back to
+// `created_at`) to match the Session drawer's tree ordering
+// (SessionTree sorts its "Trace N" nodes by start_time). Sorting by a different
+// key here made the table's first/last trace diverge from the drawer's.
 const sessionSortedTracesAtomFamily = atomFamily((sessionId: string) =>
     atom((get) => {
         const traces = get(sessionTracesAtomFamily(sessionId))
         if (!traces.length) return []
-        return [...traces].sort(
-            (a, b) => new Date(a.created_at || 0).getTime() - new Date(b.created_at || 0).getTime(),
-        )
+        const sortKey = (t: (typeof traces)[number]) =>
+            new Date(t.start_time || t.created_at || 0).getTime()
+        return [...traces].sort((a, b) => sortKey(a) - sortKey(b))
     }),
 )