Multi-rate, multi-format and multi-reach operation of optical transceivers is important, but it is not enough for next generation terabit products. What is still missing to make these products viable is a solution for the flexible control of this enormous capacity at the optical layer and its distribution among a number of independent optical flows. PANTHER aims to provide this solution and develop multi-rate, multi-format, multi-reach and multi-flow terabit transceivers for edge switches and data-center gateways. To this end, PANTHER will combine electro-optic with passive polymers and will develop a novel photonic integration platform with unprecedented potential for high-speed modulation and optical functionality on-chip. It will also rely on the combination of polymers with InP gain chips and photodiode arrays, and on the use of the InP-DHBT platform for driving circuits based on 3-bit power-DACs and high-speed TIA arrays. Using 3D integration techniques, PANTHER will integrate these components in compact system-in-package transceivers capable of operation at rates up to 64 Gbaud, operation with formats up to DP-64-QAM, spectral efficiency up to 10.24 b/s/Hz, capacity using a dual-carrier scheme up to 1.536 Tb/s, and flexibility in the generation and handling of multiple optical flows on-chip. This impressive performance will come with a potential for 55% power consumption reduction and more than 60% cost/bit reduction, taking into account benefits from the material system, the integration concept, the operation at high baud-rates and the possibility for IP traffic offloading. PANTHER will incorporate the transceivers in edge switch and data-center gateway architectures and will evaluate their performance in lab and real-network settings. Finally, PANTHER will develop a thin software layer that will control the operation parameters of the transceivers, pioneering in this way the efforts for extending the SDN hierarchy down to the flexible optical transport.