Wales ended their season on a low note as Romania won their Bucharest friendly 2-1.
Romania led through Florian Coman's tidy finish before substitute David Brooks - who had only been on the pitch for two minutes - equalised with a sweet left-foot volley after being picked out at the far post by Daniel James.
Wales had chances to turn around the contest completely, but Adrian Rus restored Romania's lead 10 minutes from time.
Wales are still without a friendly away victory since November 2008 when current manager Craig Bellamy scored the winner in Denmark.
"Disappointing," was Wales manager Bellamy's post-match assessment.
"There were some good bits, but there were some negatives as well. We need to be better.
"I felt we didn't create the opportunity enough to get into the final third and create consistent chances."
Substitute Koumas was denied an equaliser late on by Rus' goal-line intervention when a pass to the unmarked Cameron Congreve might have been the better option.
It means Wales, who suffered World Cup play-off despair on penalties in March, remain winless in 2026.
Bellamy said: "We had one or two exceptional chances of course, but we were too deep in the build-up, and that's not what we look for.
"We want to break lines and be attacking the defence on a regular basis.
"I just thought we were slow moving the ball at times which didn't help us, so I'm disappointed.
"I feel that if we want to improve, these are the areas we need to improve on. That excites me as well because I do like the team, I like how we play.
"If we are better in certain areas that's going to allow us to be able to compete with the top teams on a regular basis.
"That's where we want to be and we're going to be tested now on that in the Nations A League. It's going to test everything about us."
Wales return to action in September in a Nations League group that includes Denmark, Norway and Portugal.
The Dragons' opening game will be a trip to Portugal on September 24.
