Feat/m4 01 log to replay handoff

README.md

@@ -32,7 +32,7 @@ The **Hosted Web App** (internal runtime key `cloud`) is a pure browser SPA that
 | Static SPA over HTTPS | Accounts or login |
 | Web Serial CRSF + MAVLink link (user-granted port only) | Server-side telemetry persistence |
 | Replay and simulation (frontend-only, no upload) | Fleet or project management |
-| Same dashboard UI as desktop/browser dev | Cloud logging or sync |
+| **Download session** — buffer live telemetry in memory; export replay JSONL locally (no upload) | Cloud logging or sync |
 | | Billing or paid tiers |
 
 Self-host the Hosted Web App with `pnpm build:cloud` and serve **`apps/web/dist` from that command only** — not the output of `pnpm build` (desktop/Node stack). A wrong artifact shows the COM port dropdown and spams `WebSocket connection to …/ws failed` because the app is in `web` mode instead of `cloud`. Do not embed the app in a cross-origin iframe without a `Permissions-Policy` that allows `serial` for your origin — Web Serial is blocked by default in embedded contexts.
@@ -61,7 +61,7 @@ Prefer bench testing and disconnected telemetry validation before using the soft
 - **Optional video stream** (MJPEG, etc.) via environment variables; crosshair overlay; when the stream is live, a **Ground Target** panel docks beside the camera feed
 - **Ground target estimation** (desktop) — image-center target with GeoTIFF DEM ray marching, map marker, line-of-sight, and sample-log export (shown next to the camera when video is live)
 - **Preflight health advisory** — sensor and link health checks with configurable thresholds
-- **Session logging** and reset for new flights
+- **Session logging** — desktop and browser dev write JSONL to disk via **Start Log** / **Stop Log**; after stopping, use **Open in Replay** to load the saved log without manual import. The **Hosted Web App** and browser dev also buffer telemetry in memory — **Download session** exports replay JSONL locally, and **Open in Replay** loads the buffer directly (never uploaded). **Reset** clears the in-memory buffer.
 - **Onboarding tour** — first-run walkthrough of link controls, telemetry sidebar, map, camera, and activity log; skip anytime; restart from the **?** button in the top bar (`localStorage` keys `uav-gcs.onboarding.*`)
 - **Replay & Simulation** — frontend-only, read-only telemetry sources that drive the same dashboard without hardware: replay recorded `.jsonl`/`.json` logs (start/pause/seek/step, speed and timing modes) or run deterministic seeded simulations. See [`docs/replay-mode.md`](docs/replay-mode.md) and [`docs/adr/0003-frontend-only-replay-simulation.md`](docs/adr/0003-frontend-only-replay-simulation.md)
 - **Flight Review** — post-flight analysis over a loaded replay log (not simulation): summary stats, findings, colored path, seekable timeline with markers, and five click-to-seek graphs. Open manually from replay controls while in **Replay** mode; shares the replay clock with dashboard scrubbing. Frontend-only — nothing is uploaded. See [`docs/adr/0007-flight-review-replay-analysis-view.md`](docs/adr/0007-flight-review-replay-analysis-view.md)

apps/desktop/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@uav-ground-control-station/desktop",
-  "version": "0.2.43",
+  "version": "0.2.45",
   "private": true,
   "license": "GPL-3.0-only",
   "type": "module",

apps/desktop/src-tauri/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "uav-ground-control-station"
-version = "0.2.43"
+version = "0.2.45"
 description = "Native desktop shell for UAV Ground Control Station"
 authors = ["F. Eber"]
 license = "GPL-3.0-only"

apps/desktop/src-tauri/src/lib.rs

@@ -408,11 +408,35 @@ fn stop_logging(state: State<DesktopState>) -> Result<LoggingStatus, String> {
         writer.flush().map_err(|error| error.to_string())?;
     }
     logging.writer = None;
-    logging.file_path = None;
 
     Ok(logging_status_from_logger(&logging))
 }
 
+#[tauri::command]
+fn read_session_log(path: String, app: AppHandle) -> Result<String, String> {
+    let logs_dir = app
+        .path()
+        .app_log_dir()
+        .unwrap_or_else(|_| PathBuf::from("logs"));
+    let candidate = PathBuf::from(path.trim());
+    let canonical = candidate
+        .canonicalize()
+        .map_err(|_| "Session log file not found.".to_string())?;
+    let logs_canonical = logs_dir
+        .canonicalize()
+        .unwrap_or_else(|_| logs_dir.clone());
+    if !canonical.starts_with(&logs_canonical) {
+        return Err("Session log path is not allowed.".to_string());
+    }
+    let lower = canonical
+        .to_string_lossy()
+        .to_ascii_lowercase();
+    if !lower.ends_with(".jsonl") {
+        return Err("Session log must be a .jsonl file.".to_string());
+    }
+    std::fs::read_to_string(canonical).map_err(|_| "Unable to read session log.".to_string())
+}
+
 #[tauri::command]
 fn load_terrain_model(path: String, state: State<DesktopState>) -> Result<dem::TerrainMetadataResponse, String> {
     let mut dem = state.dem.lock().map_err(lock_error)?;
@@ -514,6 +538,7 @@ pub fn run() {
             get_telemetry,
             start_logging,
             stop_logging,
+            read_session_log,
             logging_status,
             load_terrain_model,
             get_terrain_metadata,

apps/desktop/src-tauri/tauri.conf.json

@@ -1,7 +1,7 @@
 {
   "$schema": "https://schema.tauri.app/config/2",
   "productName": "UAV Ground Control Station",
-  "version": "0.2.43",
+  "version": "0.2.45",
   "identifier": "com.uav.ground-control-station",
   "build": {
     "beforeDevCommand": "pnpm --filter @uav-ground-control-station/web dev",

apps/server/src/buildApp.ts

@@ -98,6 +98,8 @@ export async function buildApp(services?: Partial<AppServices>): Promise<Fastify
 
   app.get("/api/logging/status", async () => logger.status());
 
+  app.get("/api/logging/read", { preHandler: guardControlRoute }, async () => logger.readStoppedLog());
+
   app.get("/ws", { websocket: true }, (socket) => {
     hub.add(socket, latestTelemetry, serial.getStatus());
   });

apps/server/src/services/loggerService.ts

@@ -1,4 +1,5 @@
-import { createWriteStream, existsSync, mkdirSync, type WriteStream } from "node:fs";
+import { createWriteStream, existsSync, mkdirSync, readFileSync, type WriteStream } from "node:fs";
+import { basename } from "node:path";
 import { join } from "node:path";
 import { fileURLToPath } from "node:url";
 import { REPLAY_LOG_SCHEMA_VERSION, type LoggingStatus, type TelemetryState } from "@uav-ground-control-station/shared";
@@ -29,10 +30,20 @@ export class LoggerService {
   stop(): LoggingStatus {
     this.stream?.end();
     this.stream = null;
-    this.filePath = null;
     return this.status();
   }
 
+  readStoppedLog(): { text: string; fileName: string } {
+    if (!this.filePath) {
+      throw new Error("No session log file available.");
+    }
+
+    return {
+      text: readFileSync(this.filePath, "utf8"),
+      fileName: basename(this.filePath)
+    };
+  }
+
   status(): LoggingStatus {
     return {
       active: this.stream !== null,

apps/web/src/App.tsx

@@ -38,12 +38,18 @@ export function App() {
     linkConnection,
     wsConnected,
     runtimeMode,
+    browserSessionExportEnabled,
+    sessionSnapshot,
     refreshPorts,
     connect,
     disconnect,
     resetSession,
     startLogging,
     stopLogging,
+    downloadSession,
+    canOpenLogInReplay,
+    logReplayHandoffError,
+    openStoppedLogInReplay,
     clearLogs,
     activeSourceMode,
     setSourceMode,
@@ -170,6 +176,12 @@ export function App() {
           onReset={resetAll}
           onStartLogging={startLogging}
           onStopLogging={stopLogging}
+          onDownloadSession={downloadSession}
+          sessionExportEnabled={browserSessionExportEnabled}
+          sessionEventCount={sessionSnapshot.eventCount}
+          canOpenLogInReplay={canOpenLogInReplay}
+          logReplayHandoffError={logReplayHandoffError}
+          onOpenLogInReplay={openStoppedLogInReplay}
           onRestartTour={() => setTourRestartToken((token) => token + 1)}
           linkIssues={linkIssues}
         />

apps/web/src/components/Topbar.tsx

@@ -34,6 +34,12 @@ interface TopbarProps {
   onReset: () => Promise<void>;
   onStartLogging: () => Promise<void>;
   onStopLogging: () => Promise<void>;
+  onDownloadSession?: () => void;
+  sessionEventCount?: number;
+  sessionExportEnabled?: boolean;
+  canOpenLogInReplay?: boolean;
+  logReplayHandoffError?: string | null;
+  onOpenLogInReplay?: () => Promise<void>;
   onRestartTour: () => void;
   linkIssues?: LinkIssue[];
 }
@@ -59,6 +65,12 @@ export function Topbar({
   onReset,
   onStartLogging,
   onStopLogging,
+  onDownloadSession,
+  sessionEventCount = 0,
+  sessionExportEnabled = false,
+  canOpenLogInReplay = false,
+  logReplayHandoffError = null,
+  onOpenLogInReplay,
   onRestartTour,
   linkIssues = []
 }: TopbarProps) {
@@ -227,6 +239,21 @@ export function Topbar({
               Reset
             </button>
 
+            {sessionExportEnabled && (
+              <button
+                className="btn-secondary whitespace-nowrap border-cyan-300/30 text-cyan-100"
+                disabled={busy || sessionEventCount === 0}
+                title={
+                  sessionEventCount === 0
+                    ? "Connect and receive telemetry to build a downloadable session."
+                    : "Download replay JSONL to your device. Nothing is uploaded."
+                }
+                onClick={() => onDownloadSession?.()}
+              >
+                Download session
+              </button>
+            )}
+
             {!isCloud &&
               (loggingStatus.active ? (
                 <button
@@ -284,6 +311,32 @@ export function Topbar({
           ))}
         </div>
       )}
+
+      {activeSourceMode === "live" && canOpenLogInReplay && onOpenLogInReplay && (
+        <div className="mt-2 flex flex-wrap items-center justify-between gap-2 rounded-lg border border-amber-400/35 bg-amber-950/70 px-3 py-2 text-xs text-amber-100">
+          <div className="leading-snug">
+            {loggingStatus.filePath && !loggingStatus.active
+              ? "Session log saved to disk."
+              : "Session buffer is ready for replay."}
+            {" "}
+            Open it in Replay to scrub the flight without re-importing a file. Flight Review stays manual.
+          </div>
+          <button
+            type="button"
+            className="btn-secondary shrink-0 whitespace-nowrap border-amber-300/40 text-amber-50"
+            disabled={busy}
+            onClick={() => run(onOpenLogInReplay)}
+          >
+            Open in Replay
+          </button>
+        </div>
+      )}
+
+      {logReplayHandoffError && (
+        <div className="mt-2 rounded-lg border border-red-400/30 bg-red-950/90 px-3 py-2 text-xs text-red-100">
+          {logReplayHandoffError}
+        </div>
+      )}
     </header>
   );
 }