In stable version of `comint.el' could type next command to inferior process while the previous one executes and outputs data, and type RET / `comint-send-input'. When the previous command completed, the next command would be passed to process, and it would start executing it. With `comint.el' revision 1.18 of 2006/07/11 23:45:46 +0 can no longer do that. Reproducing as follows. In `shell' mode buffer send command: (while:;do echo .;sleep 1;done) Then run `end-of-buffer', append the next command: (while:;do echo ,;sleep 1;done) Type RET. Kill the shell child process printing `.'. With stable `comint' shell would start `,'. With latest one it does nothing, have to type one more RET to start the command typing `,'. Piggybacking commands like that is extremely useful with lengthy jobs like compilation of large packages that for various reasons must be done in sequence, not in the same time.