Dear Committee members, In Proposal #612 https://github.com/ghc-proposals/ghc-proposals/pull/612, David Binder suggests changing the semantics from `-fhpc` to auto-ingest existing .tix files for accumulation, towards _not_ auto-ingesting them and instead overwriting the .tix file with the coverage of the latest run. I agree with his assessment that the current behaviour easily leads to unexpected surprises. He suggests adding a flag --read-tix-file= to control this behaviour and defaulting that to _no_, with a grace and deprecation period prior informing the user that the currently accumulating feature will change in a future GHC release. Adding the flag to control this behaviour is fairly uncontroversial I hope, however I'd like you to. Weight in on the default. Should we change the default behaviour, or only add the flag? I'd recommend changing the default to --read-tix-file=no after a deprecation period. Best, Moritz