Buying SJC-IAH-BWI. Inexplicably for years this flight has operated with a through flight number, but change of equipment and gate at IAH. Found a cheap L fare, but wanted to book as two separate segments to maximize the chance of a CPU on one leg if both not available. Multi-city booking offered me only a more expensive T fare, not the cheaper L fare offered in the through flight. Checked individual legs, and sure enough, segment one was L=4, but segment 2 L=0, even thought a through L fare was offered when booked without multi-segment. OK, I realize, married segment issue.

On a whim before buying the higher two segment fare, I called res and asked them to try to book it. Agent says, sorry, L only available on segment one, that's why you're getting the higher T fare. Same as I deduced. Some small voice in my head said "well, push a little farther". So, I asked, "please book it as two segments anyway, and see what it fares to." Surprise -- it fares to the cheap L fare, giving L on both segments, even though both res and I see L=0 on second segment.

What's happening here??