feat(tui): unify session history and context

README.md

@@ -202,7 +202,7 @@ Use `nanobot gateway --background` for the same direct entry point without keepi
 nanobot agent
 ```
 
-This opens the native terminal client with the same configured model, workspace, tools, streaming protocol, and session engine as the WebUI. Use `/sessions` to switch saved conversations or `/new-chat` to preserve this conversation and start another one. The existing nanobot `/new` command keeps its original behavior: it resets the current chat. The client starts a local gateway only when needed and releases it when you exit. Type `exit` or press `Ctrl+C` when you are done. Use `nanobot agent --classic` for the legacy Python prompt.
+This opens the native terminal client with the same configured model, workspace, tools, streaming protocol, and session engine as the WebUI. Use `/sessions` to switch saved conversations, `/new-chat` to preserve this conversation and start another one, or `/context` to inspect the compacted summary and raw message suffix available to the agent. Press `PageUp` at the top to load earlier transcript pages. The next launch returns to your last session unless `--session` selects another one. The existing nanobot `/new` command keeps its original behavior: it resets the current chat. The client starts a local gateway only when needed and releases it when you exit. Type `exit` or press `Ctrl+C` when you are done. Use `nanobot agent --classic` for the legacy Python prompt.
 
 For one request and an immediate exit, use:
 

docs/cli-reference.md

@@ -96,6 +96,11 @@ follow the printed WebUI **Settings → Models** or `nanobot onboard --wizard` r
 | `nanobot agent --no-markdown` | Use the classic prompt and print plain text instead of Markdown |
 | `nanobot agent --logs` | Use the classic prompt and show runtime logs while chatting |
 
+Inside the native TUI, `/sessions` switches saved conversations, `/new-chat` starts another saved
+conversation, and `/context` explains the compacted summary and raw session suffix available to
+the next agent turn. `PageUp` loads older transcript pages when you reach the top. The default
+launch returns to the last attached TUI session; `--session` selects a specific session instead.
+
 ## Session Storage and Rollback
 
 Session JSONL files live under `<config-dir>/sessions/<workspace-id>/`, outside the

nanobot/channels/websocket/tests/test_websocket_channel.py

@@ -4747,6 +4747,36 @@ def test_handle_webui_thread_get_returns_json(tmp_path, monkeypatch) -> None:
     assert body["has_pending_tool_calls"] is False
 
 
+@pytest.mark.asyncio
+async def test_handle_session_context_get_reads_detached_session() -> None:
+    from urllib.parse import quote
+
+    from websockets.datastructures import Headers
+    from websockets.http11 import Request
+
+    from nanobot.session import Session
+
+    session = Session(
+        key="websocket:context-route",
+        messages=[{"role": "user", "content": "hello"}],
+    )
+    manager = MagicMock()
+    manager.read_session_snapshot.return_value = session
+    gateway = _basic_handler(MagicMock(), session_manager=manager)
+    gateway.tokens.api_tokens["tok"] = time.monotonic() + 300.0
+    encoded = quote(session.key, safe="")
+    request = Request(
+        f"/api/sessions/{encoded}/context",
+        Headers([("Authorization", "Bearer tok")]),
+    )
+
+    response = await gateway.http._handle_session_context_get(request, encoded)
+
+    assert response.status_code == 200
+    assert json.loads(response.body.decode())["replay_messages"] == 1
+    manager.read_session_snapshot.assert_called_once_with(session.key)
+
+
 def test_handle_webui_thread_get_reports_registered_turn_as_pending(
     tmp_path,
     monkeypatch,

nanobot/cli/agent.py

@@ -48,7 +48,7 @@ console = Console()
 
 def agent(
     message: str | None = typer.Option(None, "--message", "-m", help="Message to send to the agent"),
-    session_id: str = typer.Option("cli:direct", "--session", "-s", help="Session ID"),
+    session_id: str | None = typer.Option(None, "--session", "-s", help="Session ID"),
     workspace: str | None = typer.Option(None, "--workspace", "-w", help="Workspace directory"),
     config: str | None = typer.Option(None, "--config", "-c", help="Path to config file"),
     markdown: bool = typer.Option(
@@ -111,6 +111,8 @@ def agent(
                 raise typer.Exit(exit_code)
             return
 
+    session_id = session_id or "cli:direct"
+
     try:
         provider = make_provider(runtime_config)
     except ValueError as exc:

nanobot/cli/tui_launcher.py

@@ -48,7 +48,7 @@ def launch_tui(
     *,
     config_path: Path,
     workspace_override: str | None,
-    session_id: str,
+    session_id: str | None,
     theme: str,
 ) -> int:
     """Run the native TUI, owning a local gateway only when one is not running."""
@@ -78,7 +78,9 @@ def launch_tui(
                 "NANOBOT_TUI_THEME": theme,
             }
         )
-        chat_id = _websocket_chat_id(session_id)
+        state_path = config_path.parent / "tui" / "state.json"
+        env["NANOBOT_TUI_STATE_PATH"] = str(state_path)
+        chat_id = _initial_tui_chat_id(session_id, state_path)
         if chat_id:
             env["NANOBOT_TUI_CHAT_ID"] = chat_id
         else:
@@ -328,3 +330,28 @@ def _websocket_chat_id(session_id: str) -> str | None:
     if session_id == "cli:direct":
         return "tui-direct"
     return session_id.split(":", 1)[-1] or None
+
+
+def _initial_tui_chat_id(session_id: str | None, state_path: Path) -> str | None:
+    """Resume the default TUI, while keeping an explicit selector authoritative."""
+    if session_id is not None:
+        return _websocket_chat_id(session_id)
+    return _read_tui_chat_id(state_path) or _websocket_chat_id("cli:direct")
+
+
+def _read_tui_chat_id(path: Path) -> str | None:
+    """Read the last attached chat without making launch depend on optional state."""
+    try:
+        raw_payload: Any = json.loads(path.read_text(encoding="utf-8"))
+    except (OSError, json.JSONDecodeError):
+        return None
+    if not isinstance(raw_payload, dict):
+        return None
+    payload = cast(dict[str, Any], raw_payload)
+    value = payload.get("chat_id")
+    if not isinstance(value, str):
+        return None
+    value = value.strip()
+    if not value or len(value) > 256 or any(character in value for character in "\r\n"):
+        return None
+    return value

nanobot/session/manager.py

@@ -1800,6 +1800,10 @@ class SessionManager:
         """Read a session without populating the cache."""
         return cast(dict[str, Any] | None, self._store.read(key))
 
+    def read_session_snapshot(self, key: str) -> Session | None:
+        """Load a detached session snapshot without populating the runtime cache."""
+        return self._store.load(key)
+
     def read_session_metadata(self, key: str) -> dict[str, Any] | None:
         """Read session metadata without loading the transcript."""
         return cast(dict[str, Any] | None, self._store.read_metadata(key))

nanobot/webui/session_context.py

@@ -0,0 +1,51 @@
+"""Read-only projection of the session material available to the agent."""
+
+from __future__ import annotations
+
+from typing import Any, cast
+
+from nanobot.session.manager import Session
+from nanobot.utils.helpers import estimate_message_tokens, truncate_text
+
+_SUMMARY_PREVIEW_CHARS = 4_000
+
+
+def session_context_payload(session: Session) -> dict[str, Any]:
+    """Return an explainable view of session replay without building a model prompt.
+
+    The final prompt also contains workspace instructions, memory, skills, and a
+    model-specific token budget.  This projection deliberately reports only the
+    session-owned part: archived summary plus the replayable raw suffix.
+    """
+    replay = session.get_history(max_messages=0, include_runtime_context=False)
+    raw_summary = session.metadata.get("_last_summary")
+    summary = ""
+    summary_preview = ""
+    summary_at: str | None = None
+    if isinstance(raw_summary, dict):
+        summary_data = cast(dict[str, object], raw_summary)
+        text = summary_data.get("text")
+        last_active = summary_data.get("last_active")
+        if isinstance(text, str):
+            summary = text.strip()
+            summary_preview = truncate_text(summary, _SUMMARY_PREVIEW_CHARS)
+        if isinstance(last_active, str):
+            summary_at = last_active
+
+    replay_tokens = sum(estimate_message_tokens(message) for message in replay)
+    summary_tokens = (
+        estimate_message_tokens({"role": "system", "content": summary}) if summary else 0
+    )
+
+    return {
+        "schema_version": 1,
+        "session_key": session.key,
+        "total_messages": len(session.messages),
+        "archived_messages": min(session.last_consolidated, len(session.messages)),
+        "replay_messages": len(replay),
+        "estimated_replay_tokens": replay_tokens,
+        "estimated_summary_tokens": summary_tokens,
+        "estimated_session_tokens": replay_tokens + summary_tokens,
+        "archived_summary": summary_preview or None,
+        "archived_summary_at": summary_at,
+    }

nanobot/webui/ws_http.py

@@ -97,6 +97,7 @@ from nanobot.webui.session_automations import (
     session_automation_jobs,
     session_automations_payload,
 )
+from nanobot.webui.session_context import session_context_payload
 from nanobot.webui.session_list_index import (
     WEBUI_SESSION_INDEX_INTERNAL_FIELDS,
     indexed_workspace_scope,
@@ -678,6 +679,10 @@ class GatewayHTTPHandler:
         if m:
             return self._handle_webui_thread_get(request, m.group(1))
 
+        m = re.match(r"^/api/sessions/([^/]+)/context$", got)
+        if m:
+            return await self._handle_session_context_get(request, m.group(1))
+
         m = re.match(r"^/api/sessions/([^/]+)/file-preview$", got)
         if m:
             return self._handle_file_preview(request, m.group(1))
@@ -692,6 +697,24 @@ class GatewayHTTPHandler:
 
         return None
 
+    async def _handle_session_context_get(self, request: WsRequest, key: str) -> Response:
+        if not self.check_api_token(request):
+            return _http_error(401, "Unauthorized")
+        decoded_key = _decode_api_key(key)
+        if decoded_key is None:
+            return _http_error(400, "invalid session key")
+        if not _is_websocket_channel_session_key(decoded_key):
+            return _http_error(404, "session not found")
+        if self.session_manager is None:
+            return _http_error(503, "session manager unavailable")
+        session = await asyncio.to_thread(
+            self.session_manager.read_session_snapshot,
+            decoded_key,
+        )
+        if session is None:
+            return _http_error(404, "session not found")
+        return _http_json_response(session_context_payload(session))
+
     async def _handle_sessions_list(self, request: WsRequest) -> Response:
         if not self.check_api_token(request):
             return _http_error(401, "Unauthorized")

tests/cli/test_tui_launcher.py

@@ -10,6 +10,8 @@ from nanobot.cli.tui_launcher import (
     _authenticated_ws_url,
     _download_release_tui,
     _ensure_gateway,
+    _initial_tui_chat_id,
+    _read_tui_chat_id,
     _resolve_tui_command,
     _websocket_chat_id,
 )
@@ -36,6 +38,28 @@ def test_websocket_chat_id(session_id: str, expected: str | None) -> None:
     assert _websocket_chat_id(session_id) == expected
 
 
+def test_tui_chat_state_is_optional_and_validated(tmp_path: Path) -> None:
+    path = tmp_path / "tui" / "state.json"
+    assert _read_tui_chat_id(path) is None
+
+    path.parent.mkdir()
+    path.write_text('{"schema_version": 1, "chat_id": "saved-chat"}', encoding="utf-8")
+    assert _read_tui_chat_id(path) == "saved-chat"
+
+    path.write_text('{"chat_id": "bad\\nchat"}', encoding="utf-8")
+    assert _read_tui_chat_id(path) is None
+
+
+def test_default_tui_resumes_but_explicit_session_wins(tmp_path: Path) -> None:
+    path = tmp_path / "tui" / "state.json"
+    path.parent.mkdir()
+    path.write_text('{"chat_id": "saved-chat"}', encoding="utf-8")
+
+    assert _initial_tui_chat_id(None, path) == "saved-chat"
+    assert _initial_tui_chat_id("cli:direct", path) == "tui-direct"
+    assert _initial_tui_chat_id("websocket:chosen", path) == "chosen"
+
+
 def test_explicit_tui_binary_must_exist(
     monkeypatch: pytest.MonkeyPatch,
     tmp_path: Path,

tests/session/test_session_store.py

@@ -94,6 +94,17 @@ def test_manager_renames_model_preset_in_live_and_persisted_sessions(tmp_path) -
     )
 
 
+def test_read_session_snapshot_does_not_populate_runtime_cache(tmp_path) -> None:
+    stored = Session(key="websocket:context")
+    store = MagicMock(spec=SessionStore)
+    store.load.return_value = stored
+    manager = SessionManager(tmp_path, store=store)
+
+    assert manager.read_session_snapshot(stored.key) is stored
+    assert manager.get_cached(stored.key) is None
+    store.load.assert_called_once_with(stored.key)
+
+
 def test_manager_applies_file_cap_before_store_save(tmp_path) -> None:
     store = MagicMock(spec=SessionStore)
     archiver = MagicMock()

tests/webui/test_session_context.py

@@ -0,0 +1,56 @@
+from nanobot.session import Session
+from nanobot.utils.helpers import estimate_message_tokens
+from nanobot.webui.session_context import session_context_payload
+
+
+def test_session_context_separates_archive_progress_from_replay() -> None:
+    messages = [
+        {"role": "user", "content": "old question"},
+        {"role": "assistant", "content": "old answer"},
+        {"role": "user", "content": "recent question"},
+        {"role": "assistant", "content": "recent answer"},
+    ]
+    session = Session(
+        key="websocket:context",
+        messages=messages,
+        last_consolidated=2,
+        metadata={
+            "_last_summary": {
+                "text": "The archived conversation settled the old question.",
+                "last_active": "2026-08-13T10:00:00Z",
+            }
+        },
+    )
+
+    replay = session.get_history(max_messages=0, include_runtime_context=False)
+    replay_tokens = sum(estimate_message_tokens(message) for message in replay)
+    summary_tokens = estimate_message_tokens(
+        {"role": "system", "content": "The archived conversation settled the old question."}
+    )
+    payload = session_context_payload(session)
+
+    assert payload == {
+        "schema_version": 1,
+        "session_key": "websocket:context",
+        "total_messages": 4,
+        "archived_messages": 2,
+        "replay_messages": len(replay),
+        "estimated_replay_tokens": replay_tokens,
+        "estimated_summary_tokens": summary_tokens,
+        "estimated_session_tokens": replay_tokens + summary_tokens,
+        "archived_summary": "The archived conversation settled the old question.",
+        "archived_summary_at": "2026-08-13T10:00:00Z",
+    }
+
+
+def test_session_context_tolerates_untrusted_summary_metadata() -> None:
+    session = Session(
+        key="websocket:context",
+        messages=[{"role": "user", "content": "hello"}],
+        metadata={"_last_summary": "invalid"},
+    )
+
+    payload = session_context_payload(session)
+
+    assert payload["archived_summary"] is None
+    assert payload["archived_summary_at"] is None

tui/README.md

@@ -18,4 +18,11 @@ to move, `Tab` to complete, and `Esc` to close the menu.
 
 Use `/sessions` to search and switch persisted conversations without leaving the terminal.
 `/new-chat` preserves the current conversation and starts another one; nanobot's existing `/new`
-command keeps its cross-channel behavior and resets the current chat.
+command keeps its cross-channel behavior and resets the current chat. The next launch returns to
+the last session unless `--session` selects another one. When earlier transcript pages exist,
+press `PageUp` at the top to load them in place.
+
+`/context` explains the session-owned material available for the next agent turn: the compacted
+summary, replayable raw suffix, and an estimated token count. It deliberately does not expose
+private reasoning and does not pretend to be the complete model prompt; workspace instructions,
+memory, and skills are assembled separately by the Python runtime.

tui/src/app.test.ts

@@ -346,9 +346,14 @@ describe("NanobotTui layout", () => {
     setup = await createRenderer({ width: 80, height: 24, screenMode: "alternate-screen" })
     const original = globalThis.fetch
     let resolveFetch: ((response: Response) => void) | undefined
-    globalThis.fetch = (() => new Promise<Response>((resolve) => {
-      resolveFetch = resolve
-    })) as unknown as typeof fetch
+    globalThis.fetch = ((input: string | URL | Request) => {
+      if (String(input).endsWith("/api/webui/sidebar-state")) {
+        return Promise.resolve(new Response(JSON.stringify({})))
+      }
+      return new Promise<Response>((resolve) => {
+        resolveFetch = resolve
+      })
+    }) as typeof fetch
     const sent: string[] = []
     const app = NanobotTui.mount(
       setup.renderer,
@@ -388,9 +393,14 @@ describe("NanobotTui layout", () => {
     setup = await createRenderer({ width: 80, height: 24, screenMode: "alternate-screen" })
     const original = globalThis.fetch
     let resolveFetch: ((response: Response) => void) | undefined
-    globalThis.fetch = (() => new Promise<Response>((resolve) => {
-      resolveFetch = resolve
-    })) as unknown as typeof fetch
+    globalThis.fetch = ((input: string | URL | Request) => {
+      if (String(input).endsWith("/api/webui/sidebar-state")) {
+        return Promise.resolve(new Response(JSON.stringify({})))
+      }
+      return new Promise<Response>((resolve) => {
+        resolveFetch = resolve
+      })
+    }) as typeof fetch
     const app = NanobotTui.mount(
       setup.renderer,
       { ...options, apiUrl: "http://nanobot.test", apiToken: "secret" },
@@ -425,6 +435,107 @@ describe("NanobotTui layout", () => {
     }
   })
 
+  test("explains the session-owned agent context without exposing private reasoning", async () => {
+    setup = await createRenderer({ width: 96, height: 26, screenMode: "alternate-screen" })
+    const original = globalThis.fetch
+    globalThis.fetch = ((input: string | URL | Request) => {
+      expect(String(input)).toContain("/api/sessions/websocket%3Achat/context")
+      return Promise.resolve(new Response(JSON.stringify({
+        total_messages: 24,
+        archived_messages: 16,
+        replay_messages: 10,
+        estimated_replay_tokens: 2048,
+        estimated_summary_tokens: 128,
+        estimated_session_tokens: 2176,
+        archived_summary: "The earlier turns agreed on a release plan.",
+        archived_summary_at: "2026-08-13T10:00:00Z",
+      })))
+    }) as typeof fetch
+    const app = NanobotTui.mount(
+      setup.renderer,
+      { ...options, apiUrl: "http://nanobot.test", apiToken: "secret" },
+      client(),
+      new MockTreeSitterClient({ autoResolveTimeout: 0 }),
+    )
+    app.accept({ event: "attached", chat_id: "chat" })
+    const ui = app as unknown as {
+      composer: TextareaRenderable
+      contextPanel: { visible: boolean }
+    }
+
+    try {
+      ui.composer.setText("/context")
+      ui.composer.submit()
+      await waitUntil(() => ui.contextPanel.visible)
+      await setup.flush()
+      const frame = setup.captureCharFrame()
+
+      expect(frame).toContain("Agent context")
+      expect(frame).toContain("~2.2k session tokens · 10 replay messages · 16 archived · summary active")
+      expect(frame).toContain("The earlier turns agreed on a release plan.")
+      expect(frame).toContain("memory, instructions, and skills are added separately")
+
+      setup.resize(40, 10)
+      await setup.renderOnce()
+      const compact = setup.captureCharFrame()
+      expect(occurrences(compact, "Agent context")).toBe(1)
+      expect(occurrences(compact, "Ask nanobot anything")).toBe(1)
+
+      setup.mockInput.pressEscape()
+      await waitUntil(() => !ui.contextPanel.visible)
+      expect(ui.contextPanel.visible).toBe(false)
+    } finally {
+      globalThis.fetch = original
+    }
+  })
+
+  test("loads earlier transcript pages in place when PageUp reaches the top", async () => {
+    setup = await createRenderer({ width: 80, height: 22, screenMode: "alternate-screen" })
+    const original = globalThis.fetch
+    const requests: string[] = []
+    globalThis.fetch = ((input: string | URL | Request) => {
+      const url = String(input)
+      requests.push(url)
+      const older = url.includes("before=older-page")
+      return Promise.resolve(new Response(JSON.stringify({
+        messages: older
+          ? [
+              { role: "user", content: "oldest question" },
+              { role: "assistant", content: "oldest answer" },
+            ]
+          : [
+              { role: "user", content: "recent question" },
+              { role: "assistant", content: "recent answer" },
+            ],
+        page: older
+          ? { has_more_before: false, before_cursor: null }
+          : { has_more_before: true, before_cursor: "older-page" },
+      })))
+    }) as typeof fetch
+    const app = NanobotTui.mount(
+      setup.renderer,
+      { ...options, apiUrl: "http://nanobot.test", apiToken: "secret", chatId: "chat" },
+      client(),
+      new MockTreeSitterClient({ autoResolveTimeout: 0 }),
+    )
+
+    try {
+      app.accept({ event: "attached", chat_id: "chat" })
+      await waitUntil(() => (app as unknown as { ready: boolean }).ready)
+      setup.mockInput.pressKey("\u001B[5~")
+      await waitUntil(() => requests.length === 2)
+      await waitUntil(() => !(app as unknown as { historyLoadingOlder: boolean }).historyLoadingOlder)
+      await setup.flush()
+      const frame = setup.captureCharFrame()
+
+      expect(frame.indexOf("oldest question")).toBeLessThan(frame.indexOf("recent question"))
+      expect(frame.indexOf("oldest answer")).toBeLessThan(frame.indexOf("recent answer"))
+      expect((app as unknown as { historyHasMore: boolean }).historyHasMore).toBe(false)
+    } finally {
+      globalThis.fetch = original
+    }
+  })
+
   test("survives rapid narrow resizes with long CJK and code", async () => {
     setup = await createRenderer({ width: 100, height: 30, screenMode: "alternate-screen" })
     const app = mount(setup)

tui/src/app.ts

@@ -16,6 +16,7 @@ import {
 import {
   NanobotClient,
   fetchHistory,
+  fetchSessionContext,
   fetchSessions,
   fetchSlashCommands,
   type ConnectionStatus,
@@ -30,7 +31,9 @@ import {
   type TuiCommand,
 } from "./command-menu"
 import { SessionMenu } from "./session-menu"
+import { ContextPanel, type ContextPanelTheme } from "./context-panel"
 import { Transcript, type TranscriptTheme } from "./transcript"
+import { rememberChat } from "./session-state"
 
 interface AppOptions {
   wsUrl: string
@@ -42,6 +45,7 @@ interface AppOptions {
   version: string
   access: string
   theme: "auto" | ThemeMode
+  statePath?: string
 }
 
 interface ChatClient {
@@ -109,6 +113,12 @@ const LOCAL_COMMANDS: TuiCommand[] = [
     description: "Keep this conversation and start another",
     action: "new-chat",
   },
+  {
+    command: "/context",
+    title: "Agent context",
+    description: "Explain what this session contributes to the next prompt",
+    action: "context",
+  },
 ]
 
 function syntaxStyle(palette: Palette): SyntaxStyle {
@@ -157,6 +167,15 @@ function commandMenuTheme(palette: Palette): CommandMenuTheme {
   }
 }
 
+function contextPanelTheme(palette: Palette): ContextPanelTheme {
+  return {
+    text: palette.text,
+    muted: palette.muted,
+    border: palette.border,
+    accent: palette.accent,
+  }
+}
+
 function formatElapsed(milliseconds: number): string {
   const seconds = Math.max(0, Math.floor(milliseconds / 1000))
   if (seconds < 60) return `${seconds}s`
@@ -187,6 +206,7 @@ export class NanobotTui {
   private readonly transcript: Transcript
   private readonly commandMenu: CommandMenu
   private readonly sessionMenu: SessionMenu
+  private readonly contextPanel: ContextPanel
   private readonly client: ChatClient
   private readonly shell: BoxRenderable
   private readonly title: TextRenderable
@@ -203,6 +223,9 @@ export class NanobotTui {
   private finalMessage = ""
   private turnHadAnswer = false
   private historyLoaded = false
+  private historyBeforeCursor: string | null = null
+  private historyHasMore = false
+  private historyLoadingOlder = false
   private attachedOnce = false
   private pendingEvents: InboundEvent[] | null = null
   private hydrationId = 0
@@ -234,6 +257,7 @@ export class NanobotTui {
     this.commandMenu = new CommandMenu(renderer, commandMenuTheme(this.palette))
     this.commandMenu.setCommands([], LOCAL_COMMANDS)
     this.sessionMenu = new SessionMenu(renderer, commandMenuTheme(this.palette))
+    this.contextPanel = new ContextPanel(renderer, contextPanelTheme(this.palette))
     this.client = client || new NanobotClient({
       url: options.wsUrl,
       chatId: options.chatId,
@@ -292,6 +316,7 @@ export class NanobotTui {
         { name: "return", meta: true, action: "newline" },
       ],
       onContentChange: () => {
+        if (this.contextPanel.visible && this.composer.plainText) this.contextPanel.hide()
         this.syncComposerPlaceholder()
         if (this.sessionMenu.visible) this.syncSessionMenu()
         else this.syncCommandMenu()
@@ -335,6 +360,7 @@ export class NanobotTui {
     this.shell.add(this.transcript.root)
     this.shell.add(this.commandMenu.root)
     this.shell.add(this.sessionMenu.root)
+    this.shell.add(this.contextPanel.root)
     this.shell.add(this.title)
     this.shell.add(this.composerFrame)
     this.shell.add(statusRow)
@@ -425,6 +451,7 @@ export class NanobotTui {
     const command = this.commandMenu.resolve(content)
     if (command?.source === "tui") {
       if (command.command.action === "sessions") void this.openSessions()
+      else if (command.command.action === "context") void this.openContext()
       else this.startNewChat()
       return
     }
@@ -464,6 +491,7 @@ export class NanobotTui {
 
   accept(event: InboundEvent): void {
     if (event.event === "attached") {
+      void rememberChat(this.options.statePath, event.chat_id)
       this.commandTurns.clear()
       const restoring = this.attachedOnce
       this.attachedOnce = true
@@ -577,6 +605,10 @@ export class NanobotTui {
   private async prepareChat(chatId: string, restoring: boolean, hydrationId: number): Promise<void> {
     try {
       if (restoring) {
+        this.contextPanel.hide()
+        this.historyBeforeCursor = null
+        this.historyHasMore = false
+        this.historyLoadingOlder = false
         this.transcript.reset({
           model: this.modelName,
           workspace: this.options.workspace,
@@ -588,9 +620,8 @@ export class NanobotTui {
         this.historyLoaded = true
         const history = await fetchHistory(this.options.apiUrl, this.options.apiToken, chatId)
         if (hydrationId !== this.hydrationId) return
-        if (history.truncated) {
-          this.transcript.notice("Earlier messages omitted · open WebUI to load the full history")
-        }
+        this.historyBeforeCursor = history.beforeCursor
+        this.historyHasMore = history.hasMoreBefore
         this.transcript.history(history.messages)
       }
     } catch (error) {
@@ -599,7 +630,9 @@ export class NanobotTui {
     } finally {
       if (hydrationId !== this.hydrationId) return
       this.ready = true
-      if (!this.activeTurn) this.status.content = "Ready"
+      if (!this.activeTurn) {
+        this.status.content = this.historyHasMore ? "Ready · PageUp for earlier history" : "Ready"
+      }
     }
   }
 
@@ -658,6 +691,12 @@ export class NanobotTui {
   }
 
   private handleKey = (key: KeyEvent): void => {
+    if (this.contextPanel.visible && key.name === "escape") {
+      this.contextPanel.hide()
+      this.updateMeta()
+      key.preventDefault()
+      return
+    }
     if (this.sessionLoading && key.name === "escape") {
       this.closeSessions()
       this.status.content = "Ready"
@@ -748,7 +787,10 @@ export class NanobotTui {
     }
     if (key.name === "pageup" || key.name === "pagedown") {
       key.preventDefault()
-      this.transcript.scrollByPage(key.name === "pageup" ? -1 : 1)
+      const pageUp = key.name === "pageup"
+      const wasAtTop = this.transcript.atTop
+      this.transcript.scrollByPage(pageUp ? -1 : 1)
+      if (pageUp && (wasAtTop || this.transcript.atTop)) void this.loadOlderHistory()
       return
     }
     if (key.ctrl && (key.name === "home" || key.name === "end")) {
@@ -791,6 +833,7 @@ export class NanobotTui {
     this.transcript.setTheme(transcriptTheme(this.palette))
     this.commandMenu.setTheme(commandMenuTheme(this.palette))
     this.sessionMenu.setTheme(commandMenuTheme(this.palette))
+    this.contextPanel.setTheme(contextPanelTheme(this.palette))
     this.composerFrame.borderColor = this.palette.border
     this.composer.textColor = this.palette.text
     this.composer.focusedTextColor = this.palette.text
@@ -802,6 +845,7 @@ export class NanobotTui {
 
   private handleResize = (): void => {
     this.resizeComposer()
+    this.contextPanel.resize(this.renderer.height)
     this.title.visible = this.renderer.height >= 14
     this.updateMeta()
   }
@@ -823,6 +867,10 @@ export class NanobotTui {
         : "enter open · esc close"
       return
     }
+    if (this.contextPanel.visible) {
+      this.meta.content = "esc close · pgup/pgdn scroll"
+      return
+    }
     this.meta.content = this.renderer.width >= 112
       ? "enter send · alt+enter newline · pgup/pgdn scroll · ctrl+o tools · ctrl+c stop"
       : this.renderer.width >= 72
@@ -891,6 +939,7 @@ export class NanobotTui {
       return
     }
     this.commandMenu.hide()
+    this.contextPanel.hide()
     this.composer.setText("")
     this.sessionLoading = true
     const loadId = ++this.sessionLoadId
@@ -947,6 +996,7 @@ export class NanobotTui {
     }
     this.commandMenu.hide()
     this.sessionMenu.hide()
+    this.contextPanel.hide()
     this.composer.setText("")
     try {
       this.ready = false
@@ -1019,6 +1069,62 @@ export class NanobotTui {
     this.updateMeta()
   }
 
+  private async openContext(): Promise<void> {
+    this.commandMenu.hide()
+    this.sessionMenu.hide()
+    this.composer.setText("")
+    this.status.content = "Reading agent context…"
+    try {
+      const context = await fetchSessionContext(
+        this.options.apiUrl,
+        this.options.apiToken,
+        this.client.activeChatId,
+      )
+      if (!context) {
+        this.status.content = "Context unavailable · new session or older gateway"
+        return
+      }
+      this.contextPanel.show(context)
+      this.status.content = "Context snapshot"
+      this.updateMeta()
+    } catch (error) {
+      this.status.content = error instanceof Error ? error.message : String(error)
+    }
+  }
+
+  private async loadOlderHistory(): Promise<void> {
+    if (
+      this.historyLoadingOlder
+      || !this.historyHasMore
+      || !this.historyBeforeCursor
+      || !this.client.activeChatId
+    ) return
+    const hydrationId = this.hydrationId
+    const chatId = this.client.activeChatId
+    this.historyLoadingOlder = true
+    this.status.content = "Loading earlier messages…"
+    try {
+      const history = await fetchHistory(
+        this.options.apiUrl,
+        this.options.apiToken,
+        chatId,
+        this.historyBeforeCursor,
+      )
+      if (hydrationId !== this.hydrationId || chatId !== this.client.activeChatId) return
+      await this.transcript.prependHistory(history.messages)
+      this.historyBeforeCursor = history.beforeCursor
+      this.historyHasMore = history.hasMoreBefore
+      this.status.content = history.hasMoreBefore
+        ? `${history.messages.length} earlier messages · PageUp for more`
+        : "Start of session"
+    } catch (error) {
+      if (hydrationId !== this.hydrationId) return
+      this.status.content = error instanceof Error ? error.message : String(error)
+    } finally {
+      if (hydrationId === this.hydrationId) this.historyLoadingOlder = false
+    }
+  }
+
   private async copySelection(text: string): Promise<void> {
     if (!text) return
     try {

tui/src/command-menu.ts

@@ -5,7 +5,7 @@ import { PickerMenu, type PickerMenuTheme } from "./picker-menu"
 
 export type CommandMenuTheme = PickerMenuTheme
 
-export type TuiCommandAction = "sessions" | "new-chat"
+export type TuiCommandAction = "sessions" | "new-chat" | "context"
 
 export interface TuiCommand {
   command: string

tui/src/context-panel.ts

@@ -0,0 +1,116 @@
+import {
+  BoxRenderable,
+  TextAttributes,
+  TextRenderable,
+  type CliRenderer,
+} from "@opentui/core"
+
+import type { SessionContextSnapshot } from "./protocol"
+
+export interface ContextPanelTheme {
+  text: string
+  muted: string
+  border: string
+  accent: string
+}
+
+function tokens(value: number): string {
+  if (value < 1_000) return String(value)
+  const compact = value >= 10_000 ? Math.round(value / 1_000) : Math.round(value / 100) / 10
+  return `${compact}k`
+}
+
+/** Read-only explanation of the session-owned context replayed to the agent. */
+export class ContextPanel {
+  readonly root: BoxRenderable
+  private readonly title: TextRenderable
+  private readonly stats: TextRenderable
+  private readonly summary: TextRenderable
+  private readonly note: TextRenderable
+
+  constructor(renderer: CliRenderer, theme: ContextPanelTheme) {
+    this.root = new BoxRenderable(renderer, {
+      id: "nanobot-tui-context-panel",
+      width: "100%",
+      maxHeight: 12,
+      flexShrink: 0,
+      flexDirection: "column",
+      border: true,
+      borderStyle: "rounded",
+      borderColor: theme.border,
+      paddingLeft: 1,
+      paddingRight: 1,
+      visible: false,
+    })
+    this.title = new TextRenderable(renderer, {
+      id: "nanobot-tui-context-title",
+      content: "Agent context",
+      width: "100%",
+      height: 1,
+      fg: theme.text,
+      attributes: TextAttributes.BOLD,
+    })
+    this.stats = new TextRenderable(renderer, {
+      id: "nanobot-tui-context-stats",
+      content: "",
+      width: "100%",
+      fg: theme.accent,
+      wrapMode: "word",
+    })
+    this.summary = new TextRenderable(renderer, {
+      id: "nanobot-tui-context-summary",
+      content: "",
+      width: "100%",
+      maxHeight: 6,
+      fg: theme.text,
+      wrapMode: "word",
+    })
+    this.note = new TextRenderable(renderer, {
+      id: "nanobot-tui-context-note",
+      content: "Session view only · memory, instructions, and skills are added separately · Esc close",
+      width: "100%",
+      fg: theme.muted,
+      wrapMode: "word",
+    })
+    this.root.add(this.title)
+    this.root.add(this.stats)
+    this.root.add(this.summary)
+    this.root.add(this.note)
+  }
+
+  get visible(): boolean {
+    return this.root.visible
+  }
+
+  show(context: SessionContextSnapshot): void {
+    const archived = context.archivedMessages > 0
+      ? `${context.archivedMessages} archived · summary ${context.archivedSummary ? "active" : "unavailable"}`
+      : "No archived messages"
+    this.stats.content = `~${tokens(context.estimatedSessionTokens)} session tokens · ${context.replayMessages} replay messages · ${archived}`
+    this.summary.content = context.archivedSummary
+      ? `Summary\n${context.archivedSummary}`
+      : "The agent is currently replaying raw session messages; no compacted summary exists yet."
+    this.root.visible = true
+  }
+
+  hide(): void {
+    this.root.visible = false
+  }
+
+  resize(terminalHeight: number): void {
+    const compact = terminalHeight < 14
+    const medium = terminalHeight < 20
+    this.summary.visible = !compact
+    this.summary.maxHeight = medium ? 2 : 6
+    this.note.visible = !medium
+    this.root.maxHeight = compact ? 4 : medium ? 6 : 12
+  }
+
+  setTheme(theme: ContextPanelTheme): void {
+    this.root.borderColor = theme.border
+    this.title.fg = theme.text
+    this.stats.fg = theme.accent
+    this.summary.fg = theme.text
+    this.note.fg = theme.muted
+  }
+}

tui/src/index.ts

@@ -22,6 +22,7 @@ const options: AppOptions = {
   version: process.env.NANOBOT_TUI_VERSION?.trim() || "dev",
   access: process.env.NANOBOT_TUI_ACCESS?.trim() || "workspace access",
   theme: themePreference(),
+  statePath: process.env.NANOBOT_TUI_STATE_PATH?.trim() || undefined,
 }
 
 let app: NanobotTui | undefined

tui/src/protocol.test.ts

@@ -3,6 +3,7 @@ import { describe, expect, test } from "bun:test"
 import {
   NanobotClient,
   fetchHistory,
+  fetchSessionContext,
   fetchSessions,
   fetchSlashCommands,
   type InboundEvent,
@@ -177,24 +178,28 @@ describe("gateway protocol", () => {
 
   test("reports when the bounded history snapshot omits earlier turns", async () => {
     const original = globalThis.fetch
-    globalThis.fetch = (() => Promise.resolve(new Response(JSON.stringify({
-      messages: [
-        { role: "user", content: "hello" },
-        {
-          role: "tool",
-          kind: "trace",
-          content: "read_file",
-          traces: ["read_file"],
-          toolEvents: [{ phase: "end", call_id: "read-1", name: "read_file" }],
-        },
-        { role: "assistant", kind: "reasoning", content: "private thought" },
-        { role: "assistant", content: "hi" },
-      ],
-      page: { has_more_before: true },
-    })))) as unknown as typeof fetch
+    let requested = ""
+    globalThis.fetch = ((input: string | URL | Request) => {
+      requested = String(input)
+      return Promise.resolve(new Response(JSON.stringify({
+        messages: [
+          { role: "user", content: "hello" },
+          {
+            role: "tool",
+            kind: "trace",
+            content: "read_file",
+            traces: ["read_file"],
+            toolEvents: [{ phase: "end", call_id: "read-1", name: "read_file" }],
+          },
+          { role: "assistant", kind: "reasoning", content: "private thought" },
+          { role: "assistant", content: "hi" },
+        ],
+        page: { has_more_before: true, before_cursor: "older-1" },
+      })))
+    }) as typeof fetch
 
     try {
-      const history = await fetchHistory("http://nanobot.test", "token", "chat")
+      const history = await fetchHistory("http://nanobot.test", "token", "chat", "newer-page")
       expect(history).toEqual({
         messages: [
           { role: "user", content: "hello" },
@@ -205,7 +210,38 @@ describe("gateway protocol", () => {
           },
           { role: "assistant", content: "hi" },
         ],
-        truncated: true,
+        hasMoreBefore: true,
+        beforeCursor: "older-1",
+      })
+      expect(requested).toContain("before=newer-page")
+    } finally {
+      globalThis.fetch = original
+    }
+  })
+
+  test("loads the explainable session context projection", async () => {
+    const original = globalThis.fetch
+    globalThis.fetch = (() => Promise.resolve(new Response(JSON.stringify({
+      total_messages: 24,
+      archived_messages: 16,
+      replay_messages: 10,
+      estimated_replay_tokens: 2048,
+      estimated_summary_tokens: 128,
+      estimated_session_tokens: 2176,
+      archived_summary: "Older work was compacted.",
+      archived_summary_at: "2026-08-13T10:00:00Z",
+    })))) as unknown as typeof fetch
+
+    try {
+      expect(await fetchSessionContext("http://nanobot.test", "secret", "chat")).toEqual({
+        totalMessages: 24,
+        archivedMessages: 16,
+        replayMessages: 10,
+        estimatedReplayTokens: 2048,
+        estimatedSummaryTokens: 128,
+        estimatedSessionTokens: 2176,
+        archivedSummary: "Older work was compacted.",
+        archivedSummaryAt: "2026-08-13T10:00:00Z",
       })
     } finally {
       globalThis.fetch = original
@@ -267,29 +303,41 @@ describe("gateway protocol", () => {
 
   test("loads and normalizes WebUI sessions", async () => {
     const original = globalThis.fetch
-    globalThis.fetch = (() => Promise.resolve(new Response(JSON.stringify({
-      sessions: [
-        {
-          key: "websocket:chat-1",
-          title: "Release plan",
-          preview: "Prepare the release",
-          created_at: "2026-08-12T10:00:00Z",
-          updated_at: "2026-08-13T10:00:00Z",
-          run_started_at: 123,
-        },
-        { key: "cli:direct", title: "Not a WebUI session" },
-        { key: 42 },
-      ],
-    })))) as unknown as typeof fetch
+    globalThis.fetch = ((input: string | URL | Request) => {
+      const url = String(input)
+      if (url.endsWith("/api/webui/sidebar-state")) {
+        return Promise.resolve(new Response(JSON.stringify({
+          pinned_keys: ["websocket:chat-1"],
+          archived_keys: [],
+          title_overrides: { "websocket:chat-1": "Pinned release" },
+        })))
+      }
+      return Promise.resolve(new Response(JSON.stringify({
+        sessions: [
+          {
+            key: "websocket:chat-1",
+            title: "Release plan",
+            preview: "Prepare the release",
+            created_at: "2026-08-12T10:00:00Z",
+            updated_at: "2026-08-13T10:00:00Z",
+            run_started_at: 123,
+          },
+          { key: "cli:direct", title: "Not a WebUI session" },
+          { key: 42 },
+        ],
+      })))
+    }) as typeof fetch
 
     try {
       expect(await fetchSessions("http://nanobot.test", "secret")).toEqual([{
         chatId: "chat-1",
-        title: "Release plan",
+        title: "Pinned release",
         preview: "Prepare the release",
         createdAt: "2026-08-12T10:00:00Z",
         updatedAt: "2026-08-13T10:00:00Z",
         runStartedAt: 123,
+        pinned: true,
+        archived: false,
       }])
     } finally {
       globalThis.fetch = original

tui/src/protocol.ts

@@ -84,7 +84,19 @@ export interface HistoryMessage {
 
 export interface HistorySnapshot {
   messages: HistoryMessage[]
-  truncated: boolean
+  hasMoreBefore: boolean
+  beforeCursor: string | null
+}
+
+export interface SessionContextSnapshot {
+  totalMessages: number
+  archivedMessages: number
+  replayMessages: number
+  estimatedReplayTokens: number
+  estimatedSummaryTokens: number
+  estimatedSessionTokens: number
+  archivedSummary: string | null
+  archivedSummaryAt: string | null
 }
 
 export interface SlashCommand {
@@ -110,6 +122,8 @@ export interface SessionSummary {
   createdAt: string | null
   updatedAt: string | null
   runStartedAt: number | null
+  pinned: boolean
+  archived: boolean
 }
 
 const SLASH_COMMAND_LIFECYCLES = new Set([
@@ -220,17 +234,24 @@ export async function fetchHistory(
   apiUrl: string,
   apiToken: string,
   chatId: string,
+  beforeCursor?: string | null,
 ): Promise<HistorySnapshot> {
-  if (!apiUrl || !apiToken) return { messages: [], truncated: false }
+  if (!apiUrl || !apiToken) {
+    return { messages: [], hasMoreBefore: false, beforeCursor: null }
+  }
   const key = encodeURIComponent(`websocket:${chatId}`)
-  const response = await fetch(`${apiUrl}/api/sessions/${key}/webui-thread?limit=120&direction=latest`, {
+  const params = new URLSearchParams({ limit: "120", direction: "latest" })
+  if (beforeCursor) params.set("before", beforeCursor)
+  const response = await fetch(`${apiUrl}/api/sessions/${key}/webui-thread?${params}`, {
     headers: { Authorization: `Bearer ${apiToken}` },
   })
-  if (response.status === 404) return { messages: [], truncated: false }
+  if (response.status === 404) {
+    return { messages: [], hasMoreBefore: false, beforeCursor: null }
+  }
   if (!response.ok) throw new Error(`history request failed: HTTP ${response.status}`)
   const payload = (await response.json()) as {
     messages?: Array<Record<string, unknown>>
-    page?: { has_more_before?: boolean }
+    page?: { has_more_before?: boolean; before_cursor?: string }
   }
   const messages: HistoryMessage[] = (payload.messages || []).flatMap((message) => {
     const role = message.role
@@ -258,7 +279,41 @@ export async function fetchHistory(
     }
     return [{ role: role as HistoryMessage["role"], content }]
   })
-  return { messages, truncated: payload.page?.has_more_before === true }
+  return {
+    messages,
+    hasMoreBefore: payload.page?.has_more_before === true,
+    beforeCursor: typeof payload.page?.before_cursor === "string"
+      ? payload.page.before_cursor
+      : null,
+  }
+}
+
+export async function fetchSessionContext(
+  apiUrl: string,
+  apiToken: string,
+  chatId: string,
+): Promise<SessionContextSnapshot | null> {
+  if (!apiUrl || !apiToken) return null
+  const key = encodeURIComponent(`websocket:${chatId}`)
+  const response = await fetch(`${apiUrl}/api/sessions/${key}/context`, {
+    headers: { Authorization: `Bearer ${apiToken}` },
+  })
+  if (response.status === 404) return null
+  if (!response.ok) throw new Error(`context request failed: HTTP ${response.status}`)
+  const value = await response.json() as Record<string, unknown>
+  const number = (key: string) => typeof value[key] === "number" ? value[key] as number : 0
+  return {
+    totalMessages: number("total_messages"),
+    archivedMessages: number("archived_messages"),
+    replayMessages: number("replay_messages"),
+    estimatedReplayTokens: number("estimated_replay_tokens"),
+    estimatedSummaryTokens: number("estimated_summary_tokens"),
+    estimatedSessionTokens: number("estimated_session_tokens"),
+    archivedSummary: typeof value.archived_summary === "string" ? value.archived_summary : null,
+    archivedSummaryAt: typeof value.archived_summary_at === "string"
+      ? value.archived_summary_at
+      : null,
+  }
 }
 
 export async function fetchSlashCommands(
@@ -294,24 +349,43 @@ export async function fetchSessions(
   apiToken: string,
 ): Promise<SessionSummary[]> {
   if (!apiUrl || !apiToken) return []
-  const response = await fetch(`${apiUrl}/api/sessions`, {
-    headers: { Authorization: `Bearer ${apiToken}` },
-  })
+  const headers = { Authorization: `Bearer ${apiToken}` }
+  const [response, sidebarResponse] = await Promise.all([
+    fetch(`${apiUrl}/api/sessions`, { headers }),
+    fetch(`${apiUrl}/api/webui/sidebar-state`, { headers }).catch(() => null),
+  ])
   if (!response.ok) throw new Error(`session request failed: HTTP ${response.status}`)
   const payload = await response.json() as { sessions?: unknown[] }
+  let sidebar: Record<string, unknown> = {}
+  if (sidebarResponse?.ok) {
+    try {
+      const value: unknown = await sidebarResponse.json()
+      if (isRecord(value)) sidebar = value
+    } catch {
+      // Session navigation remains available against older or damaged sidebar state.
+    }
+  }
+  const pinned = new Set(Array.isArray(sidebar.pinned_keys) ? sidebar.pinned_keys : [])
+  const archived = new Set(Array.isArray(sidebar.archived_keys) ? sidebar.archived_keys : [])
+  const titles = isRecord(sidebar.title_overrides) ? sidebar.title_overrides : {}
   return (payload.sessions || []).flatMap((value) => {
     if (!isRecord(value) || typeof value.key !== "string" || !value.key.startsWith("websocket:")) {
       return []
     }
     const chatId = value.key.slice("websocket:".length)
     if (!chatId) return []
+    const titleOverride = titles[value.key]
     return [{
       chatId,
-      title: typeof value.title === "string" ? value.title : "",
+      title: typeof titleOverride === "string"
+        ? titleOverride
+        : typeof value.title === "string" ? value.title : "",
       preview: typeof value.preview === "string" ? value.preview : "",
       createdAt: typeof value.created_at === "string" ? value.created_at : null,
       updatedAt: typeof value.updated_at === "string" ? value.updated_at : null,
       runStartedAt: typeof value.run_started_at === "number" ? value.run_started_at : null,
+      pinned: pinned.has(value.key),
+      archived: archived.has(value.key),
     }]
   })
 }

tui/src/session-menu.test.ts

@@ -12,6 +12,8 @@ const sessions: SessionSummary[] = [
     createdAt: "2026-08-12T10:00:00Z",
     updatedAt: "2026-08-13T10:00:00Z",
     runStartedAt: null,
+    pinned: true,
+    archived: false,
   },
   {
     chatId: "two",
@@ -20,6 +22,8 @@ const sessions: SessionSummary[] = [
     createdAt: "2026-08-11T10:00:00Z",
     updatedAt: "2026-08-12T10:00:00Z",
     runStartedAt: null,
+    pinned: false,
+    archived: false,
   },
 ]
 

tui/src/session-menu.ts

@@ -35,7 +35,8 @@ export class SessionMenu {
         const detail = [age, preview && preview !== sessionLabel(session) ? preview : ""]
           .filter(Boolean)
           .join(" · ")
-        return `${session.active ? "● " : ""}${sessionLabel(session)}${detail ? `  ${detail}` : ""}`
+        const marker = session.active ? "● " : session.pinned ? "◆ " : session.archived ? "◇ " : ""
+        return `${marker}${sessionLabel(session)}${detail ? `  ${detail}` : ""}`
       },
       emptyText: "No matching sessions",
     })
@@ -49,7 +50,11 @@ export class SessionMenu {
   open(sessions: SessionSummary[], currentChatId: string, limit: number): void {
     const rows = sessions
       .map((session) => ({ ...session, active: session.chatId === currentChatId }))
-      .sort((left, right) => Number(right.active) - Number(left.active))
+      .sort((left, right) => {
+        return Number(right.active) - Number(left.active)
+          || Number(right.pinned) - Number(left.pinned)
+          || Number(left.archived) - Number(right.archived)
+      })
     this.picker.show(rows, "", limit)
   }
 

tui/src/session-state.test.ts

@@ -0,0 +1,27 @@
+import { afterEach, describe, expect, test } from "bun:test"
+import { mkdtemp, readFile, rm } from "node:fs/promises"
+import { tmpdir } from "node:os"
+import { join } from "node:path"
+
+import { rememberChat } from "./session-state"
+
+describe("TUI session state", () => {
+  let directory = ""
+
+  afterEach(async () => {
+    if (directory) await rm(directory, { recursive: true, force: true })
+    directory = ""
+  })
+
+  test("atomically remembers the last attached gateway chat", async () => {
+    directory = await mkdtemp(join(tmpdir(), "nanobot-tui-state-"))
+    const path = join(directory, "nested", "state.json")
+
+    await rememberChat(path, "chat-123")
+
+    expect(JSON.parse(await readFile(path, "utf8"))).toEqual({
+      schema_version: 1,
+      chat_id: "chat-123",
+    })
+  })
+})

tui/src/session-state.ts

@@ -0,0 +1,23 @@
+import { mkdir, rename, rm } from "node:fs/promises"
+import { dirname } from "node:path"
+
+export async function rememberChat(path: string | undefined, chatId: string): Promise<void> {
+  if (!path || !chatId) return
+  const temporary = `${path}.tmp-${process.pid}`
+  try {
+    await mkdir(dirname(path), { recursive: true })
+    const content = `${JSON.stringify({ schema_version: 1, chat_id: chatId })}\n`
+    await Bun.write(temporary, content)
+    try {
+      await rename(temporary, path)
+    } catch {
+      // Windows cannot always atomically replace an existing destination.
+      await Bun.write(path, content)
+      await rm(temporary, { force: true })
+    }
+  } catch {
+    // Session navigation must keep working when this optional convenience file
+    // is read-only, on a network volume, or removed during shutdown.
+    await rm(temporary, { force: true }).catch(() => {})
+  }
+}

tui/src/transcript.ts

@@ -144,6 +144,38 @@ export class Transcript {
     this.finishActivity()
   }
 
+  async prependHistory(messages: HistoryMessage[]): Promise<void> {
+    if (messages.length === 0) return
+    const previousTop = this.root.scrollTop
+    const previousHeight = this.root.scrollHeight
+    let index = 1 // Keep the launch header first.
+    for (const message of messages) {
+      if (message.role === "user") {
+        this.writeRole("›", message.content, "user", index++)
+      } else if (message.role === "assistant") {
+        this.writeMarkdown(message.content, false, index++)
+      } else {
+        const activity = this.createActivity(index++)
+        const events: ToolProgressEvent[] = message.fileEdits?.length
+          ? message.fileEdits.map((edit) => ({
+              call_id: `file:${edit.call_id || edit.path || "unknown"}`,
+              phase: edit.status === "error" ? "error" : edit.phase,
+              name: edit.path ? `${edit.tool || "edit"} ${edit.path}` : "edit file",
+              arguments: edit.error || formatDiffStat(edit),
+            }))
+          : message.toolEvents || []
+        this.updateActivity(activity, message.content, events)
+      }
+    }
+    this.renderer.requestRender()
+    await this.renderer.idle()
+    this.root.scrollTop = previousTop + Math.max(0, this.root.scrollHeight - previousHeight)
+  }
+
+  get atTop(): boolean {
+    return this.root.scrollTop <= 0
+  }
+
   user(content: string): void {
     this.finishActivity()
     this.writeRole("›", content, "user")
@@ -192,23 +224,9 @@ export class Transcript {
   }
 
   progress(content: string, events: ToolProgressEvent[] = []): string {
-    const lines = events.length > 0
-      ? events.map(formatToolEvent).filter(Boolean)
-      : content.split("\n").map(cleanProgress).filter(Boolean)
-    if (lines.length === 0) return ""
+    if (events.length === 0 && !content.split("\n").some((line) => cleanProgress(line))) return ""
     if (!this.activity) this.activity = this.createActivity()
-    for (const [index, line] of lines.entries()) {
-      const key = events[index]?.call_id ? `tool:${events[index]?.call_id}` : undefined
-      const existing = key ? this.activity.keys.get(key) : undefined
-      if (existing !== undefined) {
-        this.activity.lines[existing] = line
-      } else if (line !== this.activity.lines.at(-1)) {
-        if (key) this.activity.keys.set(key, this.activity.lines.length)
-        this.activity.lines.push(line)
-      }
-    }
-    this.renderActivity(this.activity)
-    return lines.at(-1) || ""
+    return this.updateActivity(this.activity, content, events)
   }
 
   fileEdits(edits: FileEditEvent[]): string {
@@ -263,7 +281,7 @@ export class Transcript {
     })
   }
 
-  private createActivity(): Activity {
+  private createActivity(index?: number): Activity {
     const row = this.createRow("activity")
     const text = new TextRenderable(this.renderer, {
       id: this.id("agent-activity"),
@@ -273,7 +291,7 @@ export class Transcript {
       fg: this.theme.muted,
     })
     row.add(text)
-    this.root.add(row)
+    this.root.add(row, index)
     this.styledText.push({ renderable: text, tone: "muted" })
     this.wrote = true
     const activity = { text, lines: [], keys: new Map(), expanded: false }
@@ -281,6 +299,28 @@ export class Transcript {
     return activity
   }
 
+  private updateActivity(
+    activity: Activity,
+    content: string,
+    events: ToolProgressEvent[] = [],
+  ): string {
+    const lines = events.length > 0
+      ? events.map(formatToolEvent).filter(Boolean)
+      : content.split("\n").map(cleanProgress).filter(Boolean)
+    for (const [index, line] of lines.entries()) {
+      const key = events[index]?.call_id ? `tool:${events[index]?.call_id}` : undefined
+      const existing = key ? activity.keys.get(key) : undefined
+      if (existing !== undefined) {
+        activity.lines[existing] = line
+      } else if (line !== activity.lines.at(-1)) {
+        if (key) activity.keys.set(key, activity.lines.length)
+        activity.lines.push(line)
+      }
+    }
+    this.renderActivity(activity)
+    return lines.at(-1) || ""
+  }
+
   private renderActivity(activity: Activity): void {
     if (activity.expanded || activity.lines.length <= ACTIVITY_PREVIEW_LINES) {
       activity.text.content = activity.lines.join("\n")
@@ -313,6 +353,7 @@ export class Transcript {
     marker: string,
     content: string,
     tone: "muted" | "error" | "user",
+    index?: number,
   ): void {
     const row = this.createRow(tone === "user" ? "user" : "notice", "row")
     const prefix = this.createText(marker, tone, true, "role-marker")
@@ -324,7 +365,7 @@ export class Transcript {
     text.flexGrow = 1
     row.add(prefix)
     row.add(text)
-    this.root.add(row)
+    this.root.add(row, index)
     this.wrote = true
   }
 
@@ -344,18 +385,18 @@ export class Transcript {
     return markdown
   }
 
-  private writeMarkdown(content: string, streaming: boolean): void {
-    this.writeAssistant(this.createMarkdown(content, streaming))
+  private writeMarkdown(content: string, streaming: boolean, index?: number): void {
+    this.writeAssistant(this.createMarkdown(content, streaming), index)
   }
 
-  private writeAssistant(markdown: MarkdownRenderable): BoxRenderable {
+  private writeAssistant(markdown: MarkdownRenderable, index?: number): BoxRenderable {
     const row = this.createRow("assistant", "row")
     const prefix = this.createText("•", "assistant", false, "role-marker")
     prefix.width = 2
     prefix.flexShrink = 0
     row.add(prefix)
     row.add(markdown)
-    this.root.add(row)
+    this.root.add(row, index)
     this.wrote = true
     return row
   }