swirl package gets stuck in an asynchronous loop (delayed evaluation) in R Console

[076lin]

Describe the problem

When using the swirl package in the default Positron R Console, the package's interactive evaluation becomes desynchronized with the user's input. When a user types the correct answer, Ark evaluates and prints the result, but swirl does not register the submission immediately. It drops back to a blank > prompt. The user must type something else to force swirl to react, which then causes swirl to evaluate incorrectly and throw a "Try again" message, creating an inescapable loop.

Steps to reproduce

1. Start the Positron R console.
2. Load swirl: library(swirl) and run swirl().
3. Select a course (e.g., Lesson 6: Subsetting Vectors).
4. Wait for a prompt that requires variable inspection, such as: Type x to view its contents.
5. Type x and press Enter.

Expected behavior

swirl should immediately evaluate x, I thought it validate via its readline() hooks, and print the success message to move on to the next step.

Actual behavior

1. User types x and presses Enter.
2. Ark correctly prints the contents of the vector x.
3. The issue: The console returns to the standard > prompt doing nothing. swirl does not respond.
4. The user has to type something else.
5. Only then does swirl react, throwing the failure message: "Nice try, but that's not exactly what I was hoping for. Try again." followed by printing x's contents again.
6. Crucial detail on utility functions: Interestingly, if the user types a swirl utility function like info() to force a reaction, Ark successfully executes the function (e.g., successfully printing the info menu), but swirl's delayed validation hook triggers out-of-sync right after it, throwing the "Try again" error anyway. The user is stuck in this loop.

Additional Context & Possible Root Cause

• This delayed/desynced evaluation issue does not occur when running native R.exe directly within Positron's integrated Terminal. It only happens in the console.
• Maybe relate to readline issues: Since swirl relies heavily on R's readline() to capture user input, this might related to Ark's incomplete implementation of readline and standard input handling. This shares the same root cause as the issues discussed in Readline shortcuts behave differently in the Console and Terminal panes #1953, Request: ctrl-n and ctrl-p as aliases for up and down when the console is focused #6635, and Support readline shortcuts ctrl-n and ctrl-p as aliases for up and down #6650. The REPL state machine seems to drop or misroute inputs when an interactive package pauses the console.
• OS: Windows
• Positron Version: 2026.02.1
• R Version: R version 4.3.1 (2023-06-16 ucrt)

[testlabauto]

Thank you for the detailed report @076lin! I was able to reproduce the problem exactly as you described.

I have created an issue from this discussion: #12192

We will get a fix prioritized during the next triage.