Rihanna is staying solid by A$AP Rocky's side as he faces the heat in his assault trial in Los Angeles ... taking the rapper for dinner again at one of their favorite spots to end the day.

We spotted RiRi and Rocky trying to keep a low profile last night as they left Wally's in Beverly Hills -- a celebrity hotspot frequented by the "Umbrella" singer in the past.

As they made a speedy exit together, Rihanna and Rocky didn't utter a word about the ongoing trial ... hopping into a black SUV and taking off into the night.

It's clear the performers, who've been together over 4 years and share 2 children, are putting up a united front as Rocky faces off against former friend A$AP Relli in court.

TMZ broke the story ... Rihanna always planned to attend her man's trial in order to support him, showing up first on Wednesday, then making a second appearance Thursday.

She sat in the gallery both days between Rocky's mother and sister ... occasionally pulling focus with her couture courtroom looks.

Rocky currently faces 2 felony charges of assault with a semiautomatic weapon ... over claims he pulled a gun on Relli and opened fire on him back in 2021. He rejected a plea deal from the prosecution last week ... with his lawyer, Joe Tacopina, telling TMZ they shot down the offer as Rocky has always "maintained his innocence."

Despite everything, A$AP kept his cool as he strolled into court for day 5 of his trial, rocking a cream suit with a brown tie.

If convicted, Rihanna's partner faces up to 24 years in prison ... though he doesn't seem too concerned as they keep going out to dinner in style this week.