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+# Auto-detect Upload Port Fix Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Fix auto-detect upload port failure when active log output interferes with ID? response detection.
+
+**Architecture:** Two-part fix — script-side filtering continues reading until ID match, firmware-side serial mute pauses all output during ID? response.
+
+**Tech Stack:** Python 3 + pyserial (script), ESP32-S3 + Arduino + ESP-IDF logging (firmware)
+
+---
+
+## File Structure
+
+| File | Action | Purpose |
+|------|--------|---------|
+| `tools/pio_upload_port.py` | Modify | Filter ID responses in query_id() |
+| `src/main.cpp` | Modify | Add serial mute for server |
+| `src/client.cpp` | Modify | Add serial mute for client |
+
+---
+
+### Task 1: Script-side ID filtering
+
+**Files:**
+- Modify: `tools/pio_upload_port.py:46-61`
+
+- [ ] **Step 1: Update query_id() to filter for ID response**
+
+Replace lines 46-61 in `tools/pio_upload_port.py`:
+
+```python
+def query_id(port, timeout=5):
+    try:
+        ser = serial.Serial(port, 115200, timeout=0.5)
+        time.sleep(0.1)
+        ser.reset_input_buffer()
+        ser.write(b"ID?\n")
+        deadline = time.time() + timeout
+        while time.time() < deadline:
+            line = ser.readline().decode("utf-8", errors="ignore").strip()
+            if "SylDa_Server" in line or "SylDa_Client" in line:
+                ser.close()
+                return line
+        ser.close()
+    except (serial.SerialException, OSError):
+        pass
+    return None
+```
+
+- [ ] **Step 2: Commit**
+
+```bash
+git add tools/pio_upload_port.py
+git commit -m "fix(script): filter ID response in query_id()"
+```
+
+---
+
+### Task 2: Server firmware serial mute
+
+**Files:**
+- Modify: `src/main.cpp`
+
+- [ ] **Step 1: Add serialMuted flag and mute helper**
+
+After line 17 (`static const char *TAG = "server";`), add:
+
+```cpp
+static bool serialMuted = false;
+
+static void muteSerial() {
+    serialMuted = true;
+    esp_log_level_set("*", ESP_LOG_NONE);
+}
+
+static void unmuteSerial() {
+    serialMuted = false;
+    esp_log_level_set("*", CONFIG_LOG_DEFAULT_LEVEL);
+}
+```
+
+- [ ] **Step 2: Update ID? handler to use mute**
+
+Replace lines 591-592:
+
+```cpp
+            } else if (serialBuf == "ID?") {
+                Serial.flush();
+                muteSerial();
+                Serial.println("SylDa_Server");
+                delay(50);
+                unmuteSerial();
+```
+
+- [ ] **Step 3: Commit**
+
+```bash
+git add src/main.cpp
+git commit -m "fix(server): add serial mute during ID? response"
+```
+
+---
+
+### Task 3: Client firmware serial mute
+
+**Files:**
+- Modify: `src/client.cpp`
+
+- [ ] **Step 1: Add serialMuted flag and mute helper**
+
+After line 15 (`static const char *TAG = "client";`), add:
+
+```cpp
+static bool serialMuted = false;
+
+static void muteSerial() {
+    serialMuted = true;
+    esp_log_level_set("*", ESP_LOG_NONE);
+}
+
+static void unmuteSerial() {
+    serialMuted = false;
+    esp_log_level_set("*", CONFIG_LOG_DEFAULT_LEVEL);
+}
+```
+
+- [ ] **Step 2: Update ID? handler to use mute**
+
+Replace lines 425-426:
+
+```cpp
+            } else if (serialBuf == "ID?") {
+                Serial.flush();
+                muteSerial();
+                Serial.println("SylDa_Client");
+                delay(50);
+                unmuteSerial();
+```
+
+- [ ] **Step 3: Commit**
+
+```bash
+git add src/client.cpp
+git commit -m "fix(client): add serial mute during ID? response"
+```
+
+---
+
+### Task 4: Build and verify
+
+- [ ] **Step 1: Build both environments**
+
+```bash
+pio run -e s3lite-server
+pio run -e s3lite-client
+```
+
+Expected: Both compile without errors.
+
+- [ ] **Step 2: Verify firmware version bump**
+
+Check `version.txt` exists with correct format.
+
+- [ ] **Step 3: Push branch**
+
+```bash
+git push -u origin fix/issue-16-auto-detect-port
+```
+
+---
+
+## Testing Checklist
+
+After implementation, test with actual hardware:
+
+1. Connect both server and client via USB
+2. Run `pio run -e s3lite-client -t upload` — should auto-detect client
+3. Run `pio run -e s3lite-server -t upload` — should auto-detect server
+4. Verify log output resumes after upload completes
+5. Test during active ECDH handshake (worst case)