WE HAIL MR. CARTER'S DECISION not to start producing the B-1 bomber. And what is more, we like the way he seems to have made it - setting aside his campaign pronouncements against the plane and weighing it on the current merits. We find the decision itself sensible. Old faithful B-52s can stand off enemy territory and fire cruise missiles, pilotless drones that weren't in the picture when work on the B-1 began. This obviates the need for B-1s, at upwards of $100 million a copy, with which to penetrate enemy defenses. The familiar strategic "triad" (land and sea-based missiles, and bombers) is unimpaired.

But let rejoicing be restrained. It is bracing to see a production decision on a costly new weapon rendered by considered judgment rather than by the "mad momentum" of arms building. But there can be no guarantee that the money will be permanently saved or that the Soviet-American strategic relationship will become more stable.

For the B-1's demise is the cruise missile's debut. Strategists like the cruise for being cheap, accurate and versatile - and because we're way ahead in its development. Arms controllers fear it for being cheap, accurate and versatile - and hard to count and verify. The short-range air-launched cruise missile that Mr. Carter plans to put on the B-52 is evidently not on the SALT table. But the services are champing to build other kinds of cruise missiles, including long-range, land-based ones. By doing one, you lower restraints against others. Already we're arguing with the Russians over whether bombers equipped with cruises should be counted against the sub-ceiling contemplated for multiwarhead launchers. It has got to be easier to resolve such arguments before the weapons in question are deployed.

The saga of the B-1 decision illustrates nothing so much as the difficulty of making wise decisions about weapons of great cost, high technology, long lead time, ambiguous strategic implication and extreme political volatility. But several lessons are there to be learned. First, Mr. Carter was right to reject the argument that his campaign opposition to the plane made his presidential decision a test of credibility; it was a test of judgment. Second, the Congress was wise last year to leave the production decision to the November victor. But we find it curious in this light that Mr. Carter should have let the House proceed this week to a B-1 vote - production of five plane was approved.

Exit B-1. Enter cruise, to stage center. That's where attention must now turn.