FOR TODAY'S report from the urban plus-ca-change department, we take you to Friendship Heights on the District-Maryland line. Here, where Western and Wisconsin Avenues struggle to intersect, a generation has grown up with the trenches and fences that are the trademarks of a complex under permanent construction. Yet another dispute is threatening to delay completion of a critical piece of this planning puzzle.

Three decades ago, you may recall, this area way little more that the end of a trolly line, a gateway to the city or, if you were heading the other way, to the green spaces of Montgomery County. Then came Woodward & Lothrop and next the Chevy Chase Shopping Center, followed by more little stores, parking lots, plans for a subway stop and proposals to convert Friendship Heights into an important commercial hub.

For years, the official planning agencies on either side of the border stood inconclusively by. Then citizens rushed in where planners feared to tread, organizing one of the biggest neighborhood coalitions of the day to push for a plant that would try to balance growth against the amenities homeowners were enjoying. By the mid-1970s, a District- montgomery County task force had produced an agreement covering new commercial development, traffic plans and the location of the entrances to the subway.

Now there is a dispute over the fine points of urban design for a 13-story office, retail and bus complex at the site. Montgomery County officials did approve the developers' original application. But then as the result of a court suit filed by civic groups, the developers were required to reduce the retail space somewhat and resubmit their design. Now that they have, staff members at the planning board say that by cutting the shop space in half, the developers would reduce the mall's ability to draw people in to make use of the "public amenity" of the entire project. The planners also say this scaling down will rob Metro passengers coming up the escalators of a true sense of arrival at a grand entrance.

What kind of game is being played here? Even a charter member of the no-growth-at-all school would acknowledge that constant million-dollar changes in the rules are unfair. There comes a point where agreements reached must be adhered to. That point is surely here.