Link to host plant, California Goldenbush (Ericameria ericoides) observation: https://www.inaturalist.org/observations/208027635

Rosette-Bud Gall Midge (Rhopalomyia ericameriae) This midge induces rosette bud galls with flaring and slightly recurved bracts on California Goldenbush and Palmer’s Goldenbush. At first the leafy bracts are erect, but they recurve and turn brown with age. These galls measure 7 mm long by 5 mm wide and are green when fresh. Bracts are 1–2 mm wide. Larvae develop during the spring and early summer.
Midges are small, two-winged flies. Midge larvae pupate inside the galls. Adults emerge in April to oviposite in new buds.

Plant Galls of the Western United States: a photographic guide to 536 species of plant galls found west of the Rockies, with 400+ color images and plates, Ronald A. Russo, April 2021. (Available on Amazon), p. 259, pl. 445.

Gallformers: https://www.gallformers.org/gall/2288
"Rhopalomyia ericameriae, Family: Cecidomyiidae | Genus: Rhopalomyia
Hosts: Ericameria ericoides, Ericameria nauseosa, Ericameria palmeri
Detachable: detachable
Color: brown, gray, yellow, green
Texture: leafy
Shape: rosette
Location: bud"

Gallformers shows 2 possible (insect) galls that occur on Mock Heather (as of 4/18/24): https://www.gallformers.org/id?hostOrTaxon=Ericameria+ericoides&type=host&detachable=&alignment=&cells=&color=&locations=&season=&shape=&textures=&walls=&form=&undescribed=false

I.D. Galls. Select "Identify" and type the host name: https://www.gallformers.org/id

Galls. https://www.inaturalist.org/projects/galls-of-california/journal/44203-where-to-learn-more-about-galls

Fusiform galls on Vachellia caven in nearby Cordoba, Argentina was created by "unknown" insect per https://www.scielo.sa.cr/scielo.php?script=sci_arttext&pid=S0034-77442018000301135

Note dozens of exit hole on single gall. Probably a wasp?