Tachyon's TUI sometimes does not work on the first try

[sobolevn]

Bug report

I am trying out the new profile's TUI and this happens:

2025-12-21.11.16.05.mov

When I first run the command, it shows either nothing or just a black screen. The second run always (?) works correctly.

Since I am on macos, I have to use sudo to run the profiler. And the first sudo run requires the password. Maybe that's related?

My env:

• vscode's terminal
• macos
• zsh

CC @pablogsal

Linked PRs

• gh-143040: Exit taychon live mode gracefully and display profiled script errors #143101

[yihong0618]

it happens to me once, but it happens in VS Code terminal

[pablogsal]

Will take a look soon

[pablogsal]

@sobolevn can you confirm if this also happens to you in a non-vscode terminal ?

[pablogsal]

Also in the video you are nesting two --live instances so that is also a possible cause. Does this happen also if you don't do that?

[pablogsal]

Hummm, looking at your invocation I am noticing is just wrong. You are calling the profiler with:

sudo -E SAMPLING_LIVE_TRACE=/tmp/live_trace.log ./python.exe -m profiling.sampling run -d 99999 --live -m test test_gc -F SAMPLING_LIVE_TRACE=/tmp/live_trace.log ./python.exe -m profiling.sampling run -d 99999 --live -m test test_gc -F

but that's not how you are supposed to nest them: the second call should NOT use ./python.exe. What's happening here is that the program is failing to even start. Maybe we should make this into "the live TUI doesn't;t properly report starting errors"

[pablogsal]

It you launch this with sudo -E SAMPLING_LIVE_TRACE=/tmp/live_trace.log ./python.exe -m profiling.sampling run -d 99999 --live -m test test_gc it should work

[pablogsal]

I have tried sudo -E SAMPLING_LIVE_TRACE=/tmp/live_trace.log ./python.exe -m profiling.sampling run -d 99999 --live -m test test_gc in the exact same environment as you report (macOS + vsCode terminal + zsh) and cannot reproduce

[pablogsal]

Ok I am 100% sure the problem here is that the program is crashing with an exception or something else before it can start. The UX is horrible because the user gets no feedback and you cannot see the exception :(