diff --git a/server/brewpi.py b/server/brewpi.py
index 32f36e4..30ef0d2 100755
--- a/server/brewpi.py
+++ b/server/brewpi.py
@@ -131,7 +131,9 @@ if __name__ == '__main__':
 	# Records every Sud run's measured data and forecast to their own
 	# JSON files under logs/, for later offline analysis - see
 	# tasks/sud_log.py.
-	taskmgr.add(SudLogTask(sud, tc, heater, heater_task, sud_task, DT_TASK))
+	sud_log_task = SudLogTask(sud, tc, heater, heater_task, sud_task, DT_TASK, config=config)
+	sud_task.set_on_plant_params(sud_log_task.log_plant_params)
+	taskmgr.add(sud_log_task)
 
 	# Continuous server-session log - records from startup to shutdown
 	# regardless of Sud state; written to logs/log_{date_time}.json on exit.
diff --git a/tasks/sud.py b/tasks/sud.py
index 6c86e64..38083cc 100644
--- a/tasks/sud.py
+++ b/tasks/sud.py
@@ -111,8 +111,14 @@ class SudTask(ATask):
 		# when the current step has temperature=None (inherits from a prior step).
 		self._paused_temp_soll = None
 		self._on_end = None
+		self._on_plant_params = None
 		msg_handler.set_recv_handler(self.recv)
 
+	def set_on_plant_params(self, callback):
+		"""Register a callback invoked whenever apply_plant_params() fires,
+		so external observers (e.g. SudLogTask) can record each change."""
+		self._on_plant_params = callback
+
 	def apply_plant_params(self, grain_mass, water_mass):
 		"""Keeps the real plant's and the controller's internal model's
 		plant params in sync with this Sud's own doc - L/Td come straight
@@ -129,6 +135,8 @@ class SudTask(ATask):
 		params = self.sud.derive_plant_params(grain_mass, water_mass)
 		self.pot.set_plant_params(params)
 		self.tc.set_model_plant_params(params)
+		if self._on_plant_params:
+			self._on_plant_params(self.sud.elapsed, params)
 
 	def apply_stirrer(self, phase):
 		stirrer_cfg = phase.get('stirrer', {})
diff --git a/tasks/sud_log.py b/tasks/sud_log.py
index cc76ae2..40ddf27 100644
--- a/tasks/sud_log.py
+++ b/tasks/sud_log.py
@@ -43,7 +43,7 @@ class SudLogTask(ATask):
 	and the real controller keeps actively driving toward its target
 	throughout WAIT_USER too)."""
 
-	def __init__(self, sud: Sud, tc: APid, heater: AHeater, heater_task, sud_task, interval, path='./logs'):
+	def __init__(self, sud: Sud, tc: APid, heater: AHeater, heater_task, sud_task, interval, path='./logs', config=None):
 		ATask.__init__(self, interval)
 		self.sud = sud
 		self.tc = tc
@@ -51,8 +51,12 @@ class SudLogTask(ATask):
 		self.heater_task = heater_task
 		self.sud_task = sud_task
 		self.path = path
+		self.config = config
 		# None while no run is in progress - see on_sud_state_changed().
 		self._samples = None
+		# Plant param changes during a run: [{t, params}, ...] - recorded
+		# whenever apply_plant_params() fires (once per step transition).
+		self._param_events = None
 		# Identifies this run's pair of files (log_<run_id>_<name>.json
 		# and forecast_<run_id>_<name>.json) - fixed at the moment the run
 		# starts, not when it's written out, so the name reflects when
@@ -67,21 +71,37 @@ class SudLogTask(ATask):
 		was_running = self._samples is not None
 		if self._is_running(state) and not was_running:
 			self._samples = []
+			self._param_events = []
 			self._run_id = time.strftime("%Y%m%dT%H%M%S", time.localtime())
 		elif not self._is_running(state) and was_running:
 			self._write()
 			self._samples = None
+			self._param_events = None
 			self._run_id = None
 
+	def log_plant_params(self, elapsed, params):
+		"""Called by SudTask.apply_plant_params() on every step transition
+		so the log captures which plant params were active at each point
+		in the run."""
+		if self._param_events is not None:
+			self._param_events.append({'t': elapsed, 'params': params})
+
 	def _write(self):
 		if not self._samples:
 			return
 		os.makedirs(self.path, exist_ok=True)
 		name_part = _safe_filename_part(self.sud.name)
 
+		log_data = {'Name': self.sud.name}
+		if self.config is not None:
+			log_data['Config'] = self.config
+		if self._param_events:
+			log_data['PlantParams'] = self._param_events
+		log_data['Samples'] = self._samples
+
 		samples_filename = "log_{}_{}.json".format(self._run_id, name_part)
 		with open(os.path.join(self.path, samples_filename), "w") as f:
-			json.dump({'Name': self.sud.name, 'Samples': self._samples}, f, indent='\t')
+			json.dump(log_data, f, indent='\t')
 		print("Sud log: wrote {} samples to {}".format(len(self._samples), samples_filename))
 
 		forecast_filename = "forecast_{}_{}.json".format(self._run_id, name_part)