It would be useful to be able to search logs across containers (within and between builds), especially given the frequent increase in the standard number of jobs per build in CircleCI 2.0. In instances of (for example) repeated but inconsistent errors, the current method involves navigating to separate pages/container tabs, then searching within the page at a browser level (which may require expanding collapsed sections).
Increasing discoverability of test failures within builds (including the error and where it occurred within the build) helps developers pinpoint and resolve them.
At a more macro level, even filtering by job title or branch (or failures!) would be an excellent way to zoom in on errors. The current method involves a lot of human pattern-matching, a notoriously error-prone process.