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+# RuView Troubleshooting Guide
+
+Known issues and fixes from the rebase-to-upstream branch (upstream #301).
+
+---
+
+## 1. Node not appearing in /api/v1/nodes
+
+**Symptom:** ESP32-S3 node associates with WiFi, LED blinks, but no CSI frames arrive at the server. Node missing from `/api/v1/spatial/nodes`.
+
+**Root cause:** After USB flash, the node enters a limping state where WiFi associates but the UDP CSI sender silently fails. The SoftAP + mDNS stack initializes but the CSI callback never fires.
+
+**Fix:** Power cycle the node (unplug USB, wait 2s, replug). If that doesn't work, send DTR reset via serial: `python -m serial.tools.miniterm --dtr 0 COMx 115200` then Ctrl+C.
+
+**Prevention:** Firmware 0.8.0+ includes a watchdog that detects zero CSI frames for 30s and triggers a software reset automatically. Nodes 1-10 are still on old firmware and lack this recovery (OTA-vs-BLE chicken-and-egg; see issue #6).
+
+---
+
+## 2. Person count stuck at 1
+
+**Symptom:** `estimated_persons` always returns 1 regardless of how many people are in the room.
+
+**Root cause (ADR-044):** Eight converging bugs:
+1. `score_to_person_count` had a ceiling of 3
+2. `fuse_multi_node_features` used `.max()` instead of sum — N identical readings collapsed to 1
+3. Four `.max(1)` clamps forced minimum count to 1 even when absent
+4. `field_model.estimate_occupancy` capped at `.min(3)`
+5. Normalization saturated (dividing by hardcoded thresholds instead of adaptive p95)
+6. No field model auto-calibration — eigenvalue path never activated
+7. Vitals-path clamps were asymmetric
+8. Tomography produced one blob (CC=1) so dedup gave wrong count
+
+**Fix applied (Waves 1-3):**
+- Wave 1 (`9cc5f604`): ceiling 3→10, `.max()` → sum/3 aggregation, softened `.max(1)` clamps
+- Wave 2 (`306f1262`): RollingP95 adaptive normalization, field_model 30s auto-calibration, vitals clamp symmetry
+- Wave 3 (`c3df375a`+`0d4bfb09`+`6ac70ddf`): CC flood-fill infrastructure, lambda 0.1→5.0, threshold 0.01→0.15, CC>1 gate
+
+**Current state:** `estimated_persons` = 6-8 for 5 bodies (3 humans + 2 dogs). Overcounts because the sum/3 dedup factor is a guess. Tomography still produces one blob (CC=1), so the CC path doesn't activate. Runtime-configurable lambda would help tune without redeployment.
+
+---
+
+## 3. Heart rate / breathing rate jitter
+
+**Symptom:** HR and BR readings jump wildly between frames. BR CV was 23.3%, HR CV was 12.9%.
+
+**Root cause (ADR-045):** 11 ESP32 nodes each compute independent vitals. The server used last-write-wins — whichever node's UDP packet arrived last overwrote the global vitals. At ~20 fps per node, this meant vitals randomly interleaved from different vantage points every 50ms.
+
+**Fix applied (`46fbc061`):** Best-node selection. Each node's vitals are smoothed independently via median filter + EMA. The node with the highest combined `breathing_confidence + heartbeat_confidence` is selected as authoritative. Result: BR CV 23.3% → 12.6%, HR CV 12.9% → 11.6%.
+
+**Known limitation:** The `wifi-densepose-vitals` crate has a superior 4-stage pipeline (bandpass → Hilbert envelope → autocorrelation → peak detection) but is not yet wired into the sensing server. The current `VitalSignDetector` uses a simpler FFT approach with 4 BPM frequency resolution.
+
+---
+
+## 4. Signal quality shows 50% always
+
+**Symptom:** The dashboard signal quality gauge was always stuck at ~50%.
+
+**Root cause:** Signal quality was a hardcoded placeholder value, not derived from actual CSI data.
+
+**Fix applied:** ADR-044 Wave 2 replaced the fake gauge with RollingP95 adaptive normalization. The UI honesty pass (`b2070ab4`) added beta tags to unvalidated metrics, replaced the fake gauge with per-node pill indicators, and surfaced the actual per-node signal data.
+
+---
+
+## 5. Dashboard freezes every 2-4 seconds
+
+**Symptom:** The spatial view and dashboard would freeze, then reconnect, creating a visible stutter every 2-4 seconds.
+
+**Root cause:** The WebSocket broadcast channel's `recv()` returned `Err(Lagged)` when a client fell behind. The server treated this as a fatal error and dropped the connection. The client immediately reconnected, creating a connect/disconnect cycle.
+
+**Fix applied (`581daf4f`):**
+- Server: `Lagged` error → `continue` (skip missed frames instead of disconnecting)
+- Server: 30s ping/pong keepalive to prevent Caddy proxy idle timeouts
+- Result: 154 frames over 8 seconds sustained, zero disconnects
+
+---
+
+## 6. OTA update crashes at 59%
+
+**Symptom:** OTA firmware update via `/api/v1/firmware/download` progresses to ~59% then the node crashes with `StoreProhibited` on Core 1.
+
+**Root cause:** NimBLE BLE advertising/scanning runs on Core 1. During OTA, the HTTP client also runs on Core 1. BLE and OTA compete for stack space, and the BLE scan callback triggers a memory access violation during the OTA write.
+
+**Fix:**
+1. Stop NimBLE advertising and scanning before calling `esp_https_ota_begin()`
+2. Increase httpd stack from 4KB to 8KB (`CONFIG_HTTPD_MAX_REQ_HDR_LEN` and task stack)
+3. Resume BLE after OTA completes or fails
+
+**Caveat:** Nodes running old firmware (1-10) can't receive this fix via OTA because the crash happens during the OTA itself. These nodes must be USB-flashed with firmware 0.8.0+ first, then future OTA updates will work. Node 11 was USB-flashed with the watchdog firmware and can receive OTA updates.
+
+---
+
+## 7. Can't SSH to babycube via LAN
+
+**Symptom:** `ssh thyhack@10.0.10.10` hangs at banner exchange. Ping works, TCP port 22 is open, but SSH never completes the handshake.
+
+**Workaround:** Use the Tailscale IP instead:
+```
+ssh thyhack@100.90.238.87
+```
+
+**Not the cause:** CrowdSec. The 10.0.0.0/8 range is whitelisted in CrowdSec (`cscli decisions list` shows no active decisions for LAN IPs). The banner hang occurs before any authentication attempt, so it's not a firewall block.
+
+**Suspected cause:** Unknown. Possibly MTU/fragmentation issue on the LAN segment, or a network stack bug in the babycube's NIC driver. The Tailscale overlay network (WireGuard UDP) bypasses whatever is causing the LAN TCP issue.
+
+---
+
+## 8. Right USB-C port doesn't work on some ESP32-S3 boards
+
+**Symptom:** Plugging into the right USB-C port (when facing the board with USB-C toward you) shows no serial device on the host.
+
+**Fix:** Use the left USB-C port. On most ESP32-S3-DevKitC boards, the left port is the USB-to-UART bridge (CP2102/CH340) used for flashing and serial monitor. The right port is the native USB (USB-JTAG) which requires different drivers and isn't used by the RuView firmware.