Current diagnostic velocity resolution limits our ability to search for exoplanets within the habitable zone. We propose a new capability (Crossfading-EDI or X-EDI) that will boost optical spectrograph stability and spectral resolution, enabling 100x-1000x more sensitivity for the exoplanet search. This technique for increasing the stability of any dispersive (grating or prism) spectrograph to unwanted wavelength drifts has been simulated on real data and shown to produce a 1000x or more stability improvement, by use of an interferometer using *pairs* of overlapping delays placed in series with the disperser, rather than singly-used delays. This combines fringe shifts having opposite phase reaction, to cancel drift. This technique, “Crossfading Externally Dispersed Interferometry” (X-EDI) builds upon an earlier singly- delayed Doppler technique (EDI) demonstrated on a variety of telescopes including the 5-meter Hale telescope at Mt. Palomar. The single-delay EDI technique already affords a significant stability enhancement to a spectrograph, and has been used by others to discover exoplanets in 2006 and 2016. We expect that improving EDI technique further by the use of crossfading pairs of delays will dramatically improve the instrumental noise floor due to spectrograph focal point drifts or detector pixel misplacement, which can limit the detection of small exoplanets over long (months or years) time scales. The X-EDI has been simulated on EDI data on a ThAr lamp line measured at the Hale telescope*. A simulated drift insult was applied. The observed reaction to the line position drift was reduced 1000x. All spectrographs suffer drift insults of various kinds, and the X-EDI technique reduces the reaction to these by moving the fine wavelength determination from the dispersive spectrograph to the interferometer, which uses the symmetry of delay pairs to eliminate drift. This technique can greatly improve spectral precision and stability for (1) Doppler radial velocimetry, and (2) direct planet imaging using adaptive optics (such as the Gemini Planet Imager) that feeds a low resolution integral field multi-object spectrograph. *David J. Erskine, J. Astr. Tele. Instrum. Sys., 7(2):025006, June 2021. Prepared by LLNL under Contract DE- AC52-07NA27344.