Peformance issues within container using VSCode terminal

[ndunnett]

Platform: Docker container using the ubuntu:noble base image
Terminal software: VSCode inbuilt terminal

I'm building a toy shell and have experienced poor performance in terms of latency when using reedline to handle inputs for the REPL. For example, there is delay and flickering when entering/deleting characters, and you can make the cursor overrun the buffer into the prompt by holding backspace.

Just to clarify, this is only an issue when I use it within a container in the VSCode terminal. If I build and run on my host machine, or if I docker exec -it into the container from iTerm2 or Windows Terminal, there is no problem. The problem also persists when built in release mode. I've also used rustyline and my own naive implementation using crossterm and they do not exhibit the same behaviour with all else being equal.

Steps to reproduce

I've written a minimal REPL using reedline to reproduce.

1. Clone the repo
2. Open in VSCode as a devcontainer and open the inbuilt terminal
3. cargo run --release in the repo directory
4. Type into the prompt and use backspace, the behaviour should be obvious

Apologies if this is a bit vague, I can do a screen recording later if this isn't clear enough. I really want to use reedline as it has all the features that I want to use, so I'd love to get to the bottom of this - I'm just not really sure where to start.