Setting ‘lazy-highlight-initial-delay’ to 0 (which should be a reasonable default on a modern machine) causes some flickering in the search buffer, and a lot of flickering in the echo are when ‘isearch-lazy-count’ is on. The attached patch addresses these problems. It also makes the desired effect of setting ‘lazy-highlight-initial-delay’ to 0 the default, even though that variable is unchanged. Flicker in the search buffer happens because the highlighting of matches happens after typing just one letter, and there are potentially many of those. It is fixed by adding a new variable, ‘lazy-highlight-delay-max-chars’. Lazy highlighting kicks in immediately if the search string is longer than that number. I set the default value to 2, but maybe 1 is even better. Flicker in the echo area happens even with the default value of ‘lazy-highlight-initial-delay’, if less pronouncedly, and is due to too frequent updates to the echo area message. This is solved by keeping the lazy count in the echo area of out of date for the fraction of a second where the lazy stuff is waiting to kick in. Please let me know if this works well and can be merged. Best, Augusto