Potential path issue with Quarto Preview in Positron

[nclJoshCowley]

Not sure if this should be an issue as it could be a problem with my setup, but my Quarto preview is no longer working in Positron but seems to work when calling Quarto from CLI (git bash) or RStudio.

Consider this simple Quarto document (test.qmd)

---
title: "Untitled"
format: html
---

## Quarto

Lorem Ipsum

When I try to Quarto render or preview (via the Terminal window or Preview button), I get the following in Positron only:

$ quarto render test.qmd
ERROR: The filename, directory name, or volume label syntax is incorrect. (os error 123): stat 'C:\Program Files\R\R-4.6.ind'

Stack trace:
    at Object.statSync (ext:deno_fs/30_fs.js:415:3)
    at existsSync2 (file:///C:/Users/cowlj/AppData/Local/Programs/Quarto/bin/quarto.js:2120:23)
    at rBinaryPath (file:///C:/Users/cowlj/AppData/Local/Programs/Quarto/bin/quarto.js:29240:9)
    at quartoEnvironmentParams (file:///C:/Users/cowlj/AppData/Local/Programs/Quarto/bin/quarto.js:88736:24)
    at filterParamsJson (file:///C:/Users/cowlj/AppData/Local/Programs/Quarto/bin/quarto.js:88729:33)
    at eventLoopTick (ext:core/01_core.js:178:7)
    at async runPandoc (file:///C:/Users/cowlj/AppData/Local/Programs/Quarto/bin/quarto.js:113903:22)
    at async renderPandoc (file:///C:/Users/cowlj/AppData/Local/Programs/Quarto/bin/quarto.js:115285:24)
    at async Object.onRender (file:///C:/Users/cowlj/AppData/Local/Programs/Quarto/bin/quarto.js:123976:30)
    at async renderFileInternal (file:///C:/Users/cowlj/AppData/Local/Programs/Quarto/bin/quarto.js:123953:9)
Error occurred during cleanup: PermissionDenied: Access is denied. (os error 5)

I have just updated R to see if there was an interpreter issue but the error remains the same, previous error started with

ERROR: The filename, directory name, or volume label syntax is incorrect. (os error 123): stat 'C:\R\R-4.4.ind'

As mentioned above, this works fine in RStudio or Git bash, not sure what to make of the error.

Has anyone else had similar issues or see something I'm missing?
Any help would be appreciated.

---

System details:

Positron and OS details:

Positron Version: 2026.08.1 (user setup) build 2
Code - OSS Version: 1.124.0
Commit: 48dc4ce
Date: 2026-08-09T13:35:16-06:00
Electron: 42.2.0
Chromium: 148.0.7778.97
Node.js: 24.15.0
V8: 14.8.178.14-electron.0
OS: Windows_NT x64 10.0.26100

Session details:

Using R 4.6.1 in the default location (C:\Program Files\R\R-4.6.1), on Windows 11.

[jmcphers]

It sounds like QUARTO_R may be set incorrectly.

• Can you check the value of your QUARTO_R environment variable in your terminal?
• Can you share the results of running the command Terminal: Show Environment Contributions? (with a Terminal open; will generate a Markdown report)
• Does unsetting it give you a different behavior?

[nclJoshCowley]

See Julia's comment, but for the sake of completeness:

• QUARTO_R is C:\Program Files\R\R-4.6.ind in Git Bash Terminal
• Looks fine in Terminal: Show Environment Contributions?:

  ## Extension: positron.positron-r
  
  - `PATH=C:\Program Files\R\R-4.6.1\bin\x64;${env:PATH}`
  - `QUARTO_R=C:\Program Files\R\R-4.6.1\bin\x64`
  

• Unsetting (or setting to the correct path without .ind) means Quarto render works fine.

[juliasilge]

I have a theory, if you are up for checking something out! I see C:\Program Files\R\R-4.6.ind in your error, which looks like your R path (C:\Program Files\R\R-4.6.1\bin\x64) after a shell decoded the backslashes as escape characters. \b becomes a backspace, and \x64 becomes the letter d. Positron sets QUARTO_R for the terminal, so a mangled value there explains why Quarto cannot find R.

In a Git Bash terminal in Positron, please run:

printf '%s\n' "$QUARTO_R" | cat -v

The cat -v part matters. Without it, the terminal renders the backspace and hides the evidence. If my theory is correct, the output contains a literal ^H:

C:\Program Files\R\R-4.6.1^Hind

Another, if you have time, would be to open a PowerShell terminal in Positron and run quarto render test.qmd there. I expect it to work, because PowerShell does not decode the value.

[nclJoshCowley]

Correct on all counts.

• Git bash line renders ^H within the line exactly as mentioned (C:\Program Files\R\R-4.6.1^Hind),
• Running quarto render test.qmd in Powershell works fine.

As for next steps, not sure where the mangling is happening but is it worth opening an issue? Is there a way to fix this in the interim?

[juliasilge]

It is definitely worth an issue, yep! I opened #15638 for us to explore options for how to fix this.

Thank you for the report! 🙌

[nclJoshCowley]

Thanks for the support, happy to help 😄