Persist stacks to bounded JSONL

desktop/electron/main.cjs

@@ -93,9 +93,28 @@ ipcMain.handle("nav:session-stacks", async (_event, requestedSessionId) => {
     method: "session.stacks",
     params: { sessionId: targetSessionId },
   });
-  return response.result.stacks;
+  return response.result;
 });
 
+ipcMain.handle(
+  "nav:session-stack-availability",
+  async (_event, requestedSessionId) => {
+    if (!backendUrl) {
+      throw new Error("chat session is not ready");
+    }
+    const targetSessionId = requestedSessionId || sessionId;
+    if (!targetSessionId) {
+      throw new Error("chat session is not ready");
+    }
+    const response = await sendRpc({
+      backendUrl,
+      method: "session.stackAvailability",
+      params: { sessionId: targetSessionId },
+    });
+    return response.result;
+  },
+);
+
 ipcMain.handle("nav:switch-session", async (_event, id) => {
   if (!backendUrl) {
     throw new Error("chat session is not ready");

desktop/electron/preload.cjs

@@ -81,6 +81,13 @@ contextBridge.exposeInMainWorld("nav", {
       sessionId == null ? undefined : normalizeSessionId(sessionId),
     );
   },
+  // Advisory scan for whether stack records are currently retained.
+  sessionStackAvailability(sessionId) {
+    return ipcRenderer.invoke(
+      "nav:session-stack-availability",
+      sessionId == null ? undefined : normalizeSessionId(sessionId),
+    );
+  },
   // Switch the active conversation to an existing session.
   switchSession(sessionId) {
     return ipcRenderer.invoke(

desktop/electron/renderer/src/App.jsx

@@ -13,6 +13,7 @@ export default function App() {
   const [modelInfo, setModelInfo] = useState(null);
   const [stopPending, setStopPending] = useState(false);
   const [activeView, setActiveView] = useState("chat");
+  const [stackAvailable, setStackAvailable] = useState(false);
   const [stackRefreshKey, setStackRefreshKey] = useState(0);
   const [newSessionMode, setNewSessionMode] = useState("local");
 
@@ -24,6 +25,7 @@ export default function App() {
   const stopSentForActiveRunRef = useRef(false);
   const stopRequestedRef = useRef(false);
   const nextMessageIdRef = useRef(0);
+  const stackAvailabilityRequestRef = useRef(0);
 
   const setConnectedState = useCallback((isConnected) => {
     connectedRef.current = isConnected;
@@ -69,6 +71,10 @@ export default function App() {
     window.setTimeout(refreshStacks, 120);
   }, [refreshStacks]);
 
+  const markStacksUnavailable = useCallback(() => {
+    setStackAvailable(false);
+  }, []);
+
   const appendMessage = useCallback(
     (role, text) => {
       setMessages((current) => [
@@ -146,6 +152,42 @@ export default function App() {
     }
   }, []);
 
+  const refreshStackAvailability = useCallback(
+    async (sessionId, options = {}) => {
+      if (!window.nav) {
+        return;
+      }
+      const targetSessionId = sessionId ?? activeSessionIdRef.current;
+      if (!targetSessionId) {
+        setStackAvailable(false);
+        return;
+      }
+      const requestId = stackAvailabilityRequestRef.current + 1;
+      stackAvailabilityRequestRef.current = requestId;
+      if (options.reset) {
+        setStackAvailable(false);
+      }
+      try {
+        const availability =
+          await window.nav.sessionStackAvailability(targetSessionId);
+        if (
+          requestId === stackAvailabilityRequestRef.current &&
+          targetSessionId === activeSessionIdRef.current
+        ) {
+          setStackAvailable(availability?.available === true);
+        }
+      } catch {
+        if (
+          requestId === stackAvailabilityRequestRef.current &&
+          targetSessionId === activeSessionIdRef.current
+        ) {
+          setStackAvailable(false);
+        }
+      }
+    },
+    [],
+  );
+
   const renderBackendStatus = useCallback(
     (status) => {
       switch (status.state) {
@@ -215,10 +257,12 @@ export default function App() {
       setRunningState(false);
       refreshSessions();
       refreshModelInfo(status.sessionId);
+      refreshStackAvailability(status.sessionId, { reset: true });
     },
     [
       refreshModelInfo,
       refreshSessions,
+      refreshStackAvailability,
       renderBackendStatus,
       setActiveSession,
       setConnectedState,
@@ -277,6 +321,7 @@ export default function App() {
           setStopRequested(false);
           refreshSessions();
           refreshModelInfo();
+          refreshStackAvailability();
           refreshStacksAfterTerminalEvent();
           break;
         case "run.failed":
@@ -286,6 +331,7 @@ export default function App() {
           setStopRequested(false);
           refreshSessions();
           refreshModelInfo();
+          refreshStackAvailability();
           refreshStacksAfterTerminalEvent();
           break;
         default:
@@ -296,6 +342,7 @@ export default function App() {
       appendMessage,
       refreshModelInfo,
       refreshSessions,
+      refreshStackAvailability,
       refreshStacks,
       refreshStacksAfterTerminalEvent,
       setRunningState,
@@ -310,10 +357,17 @@ export default function App() {
   const activateCreatedSession = useCallback(
     async (sessionId) => {
       setActiveSession(sessionId);
+      setStackAvailable(false);
       await refreshSessions();
       refreshModelInfo(sessionId);
+      refreshStackAvailability(sessionId, { reset: true });
     },
-    [refreshModelInfo, refreshSessions, setActiveSession],
+    [
+      refreshModelInfo,
+      refreshSessions,
+      refreshStackAvailability,
+      setActiveSession,
+    ],
   );
 
   const selectSession = useCallback(
@@ -328,16 +382,26 @@ export default function App() {
 
       const previousSessionId = activeSessionIdRef.current;
       clearTranscript();
+      setActiveView("chat");
+      setStackAvailable(false);
       setActiveSession(sessionId);
       try {
         await window.nav.switchSession(sessionId);
         refreshModelInfo(sessionId);
+        refreshStackAvailability(sessionId, { reset: true });
       } catch (error) {
         setActiveSession(previousSessionId);
+        refreshStackAvailability(previousSessionId, { reset: true });
         appendMessage("error", `Could not open session: ${error.message}`);
       }
     },
-    [appendMessage, clearTranscript, refreshModelInfo, setActiveSession],
+    [
+      appendMessage,
+      clearTranscript,
+      refreshModelInfo,
+      refreshStackAvailability,
+      setActiveSession,
+    ],
   );
 
   const startNewChatInProject = useCallback(
@@ -427,11 +491,13 @@ export default function App() {
           activeView={activeView}
           connected={connected}
           sessionId={activeSessionId}
+          showStacks={stackAvailable}
           onSelectView={setActiveView}
         />
         {activeView === "stacks" ? (
           <StacksPage
             key={`${activeSessionId ?? "none"}-${stackRefreshKey}`}
+            onUnavailable={markStacksUnavailable}
             sessionId={activeSessionId}
           />
         ) : (
@@ -454,7 +520,13 @@ export default function App() {
   );
 }
 
-function SessionToolbar({ activeView, connected, sessionId, onSelectView }) {
+function SessionToolbar({
+  activeView,
+  connected,
+  sessionId,
+  showStacks,
+  onSelectView,
+}) {
   return (
     <header className="session-toolbar">
       <div className="session-toolbar-title">
@@ -472,15 +544,17 @@ function SessionToolbar({ activeView, connected, sessionId, onSelectView }) {
         >
           Chat
         </button>
-        <button
-          type="button"
-          className="session-view-tab"
-          aria-current={activeView === "stacks" ? "page" : undefined}
-          disabled={!connected || !sessionId}
-          onClick={() => onSelectView("stacks")}
-        >
-          Stacks
-        </button>
+        {showStacks ? (
+          <button
+            type="button"
+            className="session-view-tab"
+            aria-current={activeView === "stacks" ? "page" : undefined}
+            disabled={!connected || !sessionId}
+            onClick={() => onSelectView("stacks")}
+          >
+            Stacks
+          </button>
+        ) : null}
       </nav>
     </header>
   );

desktop/electron/renderer/src/components/StacksPage.jsx

@@ -1,24 +1,32 @@
 import { useEffect, useMemo, useState } from "react";
 
-export default function StacksPage({ sessionId }) {
+export default function StacksPage({ onUnavailable, sessionId }) {
   const [stacks, setStacks] = useState([]);
   const [loading, setLoading] = useState(false);
   const [error, setError] = useState(null);
+  const [unavailableReason, setUnavailableReason] = useState(null);
 
   useEffect(() => {
     let alive = true;
     if (!sessionId || !window.nav) {
       setStacks([]);
+      setUnavailableReason(null);
       return undefined;
     }
 
     setLoading(true);
     setError(null);
+    setUnavailableReason(null);
     window.nav
       .sessionStacks(sessionId)
-      .then((nextStacks) => {
+      .then((result) => {
         if (alive) {
-          setStacks(Array.isArray(nextStacks) ? nextStacks : []);
+          const nextStacks = Array.isArray(result?.stacks) ? result.stacks : [];
+          setStacks(nextStacks);
+          setUnavailableReason(result?.unavailableReason ?? null);
+          if (nextStacks.length === 0 && result?.unavailableReason) {
+            onUnavailable?.(result.unavailableReason);
+          }
         }
       })
       .catch((fetchError) => {
@@ -35,7 +43,7 @@ export default function StacksPage({ sessionId }) {
     return () => {
       alive = false;
     };
-  }, [sessionId]);
+  }, [onUnavailable, sessionId]);
 
   const orderedStacks = useMemo(
     () => [...stacks].sort((left, right) => left.sequence - right.sequence),
@@ -74,7 +82,7 @@ export default function StacksPage({ sessionId }) {
       </div>
 
       {orderedStacks.length === 0 ? (
-        <EmptyStacks text="No model calls captured for this live session yet" />
+        <EmptyStacks text={emptyStackText(unavailableReason)} />
       ) : (
         <ol className="stack-call-list">
           {orderedStacks.map((stack) => (
@@ -154,6 +162,19 @@ function EmptyStacks({ text }) {
   return <div className="stacks-empty">{text}</div>;
 }
 
+function emptyStackText(reason) {
+  switch (reason) {
+    case "trimmed_or_missing":
+      return "Stack records for this session were no longer available. The stack log is capped at 800MB, so older records may have been trimmed.";
+    case "stack_store_unavailable":
+      return "Stack storage is unavailable for this backend run.";
+    case "stack_store_error":
+      return "Stack records could not be read from the local stack log.";
+    default:
+      return "No model calls captured for this live session yet";
+  }
+}
+
 function defaultOpen(layer) {
   return [
     "system_prompt",

desktop/electron/renderer/window.d.ts

@@ -44,8 +44,8 @@ declare global {
         thinking?: string | null;
         tokenUsage?: { used: number; contextWindow: number } | null;
       }>;
-      sessionStacks(sessionId?: string): Promise<
-        Array<{
+      sessionStacks(sessionId?: string): Promise<{
+        stacks: Array<{
           id: string;
           runId: string;
           sequence: number;
@@ -61,8 +61,12 @@ declare global {
             text?: string;
             json?: unknown;
           }>;
-        }>
-      >;
+        }>;
+        unavailableReason?: string;
+      }>;
+      sessionStackAvailability(sessionId?: string): Promise<{
+        available: boolean;
+      }>;
       switchSession(sessionId: string): Promise<void>;
       newSession(
         workspaceRoot?: string | null,