Date: 201709
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Light: Daylight
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Situational Awareness
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural FAR; Flight Deck / Cabin / Aircraft Event Other / Unknown
Detector: Person Flight Crew
When detected: Aircraft In Service At Gate
Result: General None Reported / Taken
Contributing factors: Company Policy; Procedure
Primary problem: Ambiguous

Narrative: The FO (First Officer) and I arrived into the Gate; and were running late due to up-line ATC delays. The FO proceeded to our gate; and I stopped on my way to get some food. When I arrived at the aircraft; I was surprised that all 175 Passengers had already been boarded. I was told that we had a Company Pilot jump seating and he had been on board when they were boarding. When I began to unpack my things; I realized that I had left my iPad at the last aircraft. I ran up the jet bridge and informed the Agent that I had to run back and get my iPad. When I returned a few minutes later; the Agent shut the door and followed me down the jet bridge. Within a minute of sitting down to start my preflight duties; the Agent shut the aircraft door. I had not even started my preflight duties; nor had I signed the Release. The FO said we needed to reopen the door because he had not done his walk around yet. We opened the door prior to his pulling the jet bridge back and I spoke with him; informing that it was going to be 10-15 minutes before we were ready. It was obvious to me that he was in a hurry to get us out. We finally completed our preflight duties; signed the paperwork and pushed back.Later; during the flight; I was told by both the jump seater and the FA's (Flight Attendants) that the Agent had begun boarding with no pilot monitoring the aircraft and no power on the aircraft other than the ground service bus. One of the FA's informed the Agent they could not board without us and went so far as to show him the bulletin in her manual. He told the FA's that there is a new procedure and they could now board without the Pilots. So when the jump seater boarded and popped his head into the cockpit to check in with us; the Crew; (we had not arrived yet) he witnessed another Agent or CSA trying to start the APU and get power on the aircraft. At that point; the jump seater took over; powered up and babysat the aircraft until my FO arrived.I spoke with the inbound Captain; and he was told by his Agent (different from ours) that the through Passengers had been deplaned and was not getting back on. Therefore; this Captain elected to terminate the aircraft rather than run the new procedure of leaving the aircraft powered.I have several concerns about what transpired. First; the Agent has a very new Employee number and was being supervised by either another Agent or a Supervisor. It was obvious that he was under a tremendous pressure to close the door and get us going. I was definitely feeling like I was being rushed. Of course; I set the tone and the pace and the FO and I were making sure we were not hurrying through our preflight and checklists. Closing the door and pulling the jet bridge back before I had even settled in; much less checking with me; the Captain; to see if I am ok with closing the door; is completely unacceptable. It seems our Agents are under so much pressure to close the door that is compromising Safety.  I was told by the Supervisor that they only had to verify the count with the 'A' before closing the door. It should be standard operating procedures to check with the Captain before closing the main cabin door. My second concern is that we obviously have OPS Personnel misinterpreting this new procedure of 'Aircraft on Gate Services without Pilots' or their procedure is wrong. They are not allowed to board without the aircraft powered AND being monitored by an operating Flight Deck Crew Member. Third; I am concerned that the Agents are under so much pressure that they are not LISTENING and heeding the information given to them by the FA's. If the FA's say they can't board; then DON'T do it. My FA's had very serious concerns. The intercom system does not work when the aircraft is not powered. If they need to order an evacuation or if they have other Passenger Safety concerns; there was no way to make a PA or communicate with each other via the interphone. The other concern was that the lavatories did not work;so the Passengers could not use them until power was restored to the aircraft.




Synopsis: The Pilot of a Boeing 737 reported that passengers were boarded prior to the flight crew arriving.