Reactive nitrogen species (NO_y) are involved in the formation of secondary pollutants, thus following their interconversions is crucial for understanding their impact on air quality. While nitric oxide (NO) and nitrogen dioxide (NO₂), are important contributors to total NO_y, further constituents such as the nitrate radical (NO₃) and dinitrogen pentoxide (N₂O₅), formed from NO₂oxidation, are key intermediates in nocturnal oxidation processes. Even though NO₃ and N₂O₅ affect the NO_y budget in the following day, their role is poorly constrained in isolated measurements. We present the “NOyBOx”, a new instrumental framework combining measurements of NO, NO₂ and NO_y from commercial analyzers with a custom-built incoherent broadband cavity-enhanced absorption spectrometer (IBBCEAS) that measures NO₃ directly and N₂O₅ via a thermal dissociation inlet (TDI) and channel differencing. We describe the design of the IBB-CEAS subsystem, characterize the TDI, cavity optics, transmission losses, and, using a synthetic spectra simulation approach, the bias of ambient NO₂ and water vapor on our concentration retrieval procedure. Under optimal laboratory conditions we find a limit of detection (LOD) of 1.5 and 2.2 pptv (1σ Allan deviation, 15 s) for NO₃ and N₂O₅, respectively. Under field conditions, interference by water vapor and NO₂ worsens these LODs to 3.1 pptv with a total measurement uncertainty (TMU) of 12 % for NO₃, and to 4.4 pptv with a mean TMU of 21 % for N₂O₅. Exemplary results from its first deployment during a field campaign in a temperate forest atop a 40 m tall tower are discussed.