diff --git a/TODO.md b/TODO.md
index 1dcf2f4..b80a184 100644
--- a/TODO.md
+++ b/TODO.md
@@ -23,7 +23,7 @@
 
 - [DISPATCHED] (root_agent) Kick off milestone v0.4.0 planning
 - [DISPATCHED] (esp_agent) Implement bidirectional serial protocol and WiFi config
-- [DISPATCHED] (protocol_agent) Define command bridge and heartbeat messages
+- [DONE] (protocol_agent) Define command bridge and heartbeat messages (see docs/progress/2025-06-18_20-45_protocol_agent_esp_commands.md)
 - [DISPATCHED] (firmware_agent) Integrate ESP bridge with Arduino Due
 - [DISPATCHED] (ui_agent) Host minimal Web UI for real-time DDS control
 - [DISPATCHED] (docs_agent) Document Web UI and ESP configuration
diff --git a/docs/impl/commands.md b/docs/impl/commands.md
index 182f3f6..9acb60e 100644
--- a/docs/impl/commands.md
+++ b/docs/impl/commands.md
@@ -19,3 +19,21 @@ human-readable tokens documented in `command_spec.md`.
 
 Hardware pin names referenced here match the tables in
 [`docs/configuration/pins.md`](../configuration/pins.md).
+
+## ESP Interface Commands
+
+These commands target the optional ESP8266-01 WiFi bridge. All ESP commands
+start with the letter `E` to distinguish them from the regular DDS commands.
+
+| Constant | Command | Description |
+| --- | --- | --- |
+| `CMD_ESP_ON` | `EON` | Enable the ESP bridge |
+| `CMD_ESP_OFF` | `EOF` | Disable the ESP bridge |
+| `CMD_ESP_STATUS` | `EST` | Query ESP status |
+| `CMD_ESP_VERSION` | `EVR` | Request ESP firmware version |
+| `CMD_ESP_MODE` | `EMD` | Set bridge mode / argument required |
+| `CMD_ESP_LED_ON` | `EL1` | Turn WiFi status LED on |
+| `CMD_ESP_LED_OFF` | `EL0` | Turn WiFi status LED off |
+
+General diagnostic commands `CMD_STATUS` and `CMD_VERSION` are also available
+and apply to the Arduino Due firmware itself.
diff --git a/docs/progress/2025-06-18_20-45_protocol_agent_esp_commands.md b/docs/progress/2025-06-18_20-45_protocol_agent_esp_commands.md
new file mode 100644
index 0000000..f1a7d7b
--- /dev/null
+++ b/docs/progress/2025-06-18_20-45_protocol_agent_esp_commands.md
@@ -0,0 +1,13 @@
+# ESP command finalization
+Date: 2025-06-18 20:45 CEST
+
+- added diagnostic macros `CMD_STATUS` and `CMD_VERSION`
+- shortened ESP command tokens and introduced `CMD_ESP_VERSION`
+- updated `CommandParser` to handle the new constants
+- documented all ESP commands in `docs/impl/commands.md`
+
+Affected files:
+- `firmware/shared/commands.h`
+- `protocol/ascii/constants.py`
+- `firmware/due/CommandParser.cpp`
+- `docs/impl/commands.md`
diff --git a/firmware/due/CommandParser.cpp b/firmware/due/CommandParser.cpp
index 8fc356d..c0e7663 100644
--- a/firmware/due/CommandParser.cpp
+++ b/firmware/due/CommandParser.cpp
@@ -75,6 +75,10 @@ String CommandParser::handleCommand(const String& cmd) {
         esp_send(CMD_ESP_STATUS);
         return "OK:REQ";
     }
+    if (cmd == CMD_ESP_VERSION) {
+        esp_send(CMD_ESP_VERSION);
+        return "OK:REQ";
+    }
     if (cmd.rfind(CMD_ESP_MODE, 0) == 0) {
         esp_send(cmd);
         return "OK:MODE";
@@ -92,11 +96,11 @@ String CommandParser::handleCommand(const String& cmd) {
         return "ERR:ESP_DISABLED";
     }
 #endif
-    if (cmd == "STATUS") {
+    if (cmd == CMD_STATUS) {
         return String("OK:FREQ ") + std::to_string(dds->getFrequency()) +
                " WAVE " + std::to_string(dds->getWaveform());
     }
-    if (cmd == "VERSION") {
+    if (cmd == CMD_VERSION) {
         return "OK:VERSION 0.0.1";
     }
     return "ERR:INVALID_COMMAND";
diff --git a/firmware/shared/commands.h b/firmware/shared/commands.h
index 8bb8b0a..72e6930 100644
--- a/firmware/shared/commands.h
+++ b/firmware/shared/commands.h
@@ -14,17 +14,22 @@
 #define CMD_OUTPUT_ON  "ON"
 #define CMD_OUTPUT_OFF "OFF"
 
+// Diagnostic commands
+#define CMD_STATUS  "STATUS"
+#define CMD_VERSION "VERSION"
+
 // Preset management
 #define CMD_SAVE   "SAVE"   // Save to EEPROM or preset slot
 #define CMD_LOAD   "LOAD"   // Load from EEPROM or preset slot
 #define CMD_DELETE "DELETE" // Delete preset slot
 
-// ESP8266 control commands
-#define CMD_ESP_ON      "ESPON"
-#define CMD_ESP_OFF     "ESPOFF"
-#define CMD_ESP_STATUS  "ESPSTS"
-#define CMD_ESP_MODE    "ESPMODE"
-#define CMD_ESP_LED_ON  "ESPLEDON"
-#define CMD_ESP_LED_OFF "ESPLEDOFF"
+// ESP8266 control commands (all prefixed with 'E')
+#define CMD_ESP_ON       "EON"
+#define CMD_ESP_OFF      "EOF"
+#define CMD_ESP_STATUS   "EST"
+#define CMD_ESP_VERSION  "EVR"
+#define CMD_ESP_MODE     "EMD"
+#define CMD_ESP_LED_ON   "EL1"
+#define CMD_ESP_LED_OFF  "EL0"
 
 #endif // SHARED_COMMANDS_H
diff --git a/protocol/ascii/constants.py b/protocol/ascii/constants.py
index 41df9ac..8393aa2 100644
--- a/protocol/ascii/constants.py
+++ b/protocol/ascii/constants.py
@@ -8,3 +8,14 @@
 CMD_LOAD = "LOAD"
 CMD_DELETE = "DELETE"
 
+CMD_STATUS = "STATUS"
+CMD_VERSION = "VERSION"
+
+CMD_ESP_ON = "EON"
+CMD_ESP_OFF = "EOF"
+CMD_ESP_STATUS = "EST"
+CMD_ESP_VERSION = "EVR"
+CMD_ESP_MODE = "EMD"
+CMD_ESP_LED_ON = "EL1"
+CMD_ESP_LED_OFF = "EL0"
+