Session Watcher never attaches on Windows 11 with R 4.6.1 + Radian 0.6.16 (.vsc.attach not found, "R: (not attached)") #1723

{
    "r.rterm.windows": "C:\\Users\\davellb\\AppData\\Local\\Python\\pythoncore-3.14-64\\Scripts\\radian.exe",
    "r.rterm.option": [
        "--no-save",
        "--no-restore"
    ],
    "r.bracketedPaste": true,
    "r.sessionWatcher": true,
    "r.alwaysUseActiveTerminal": true
}

What works

R terminal starts normally
Radian starts correctly
Code execution works
Plotting works
languageserver works
httpgd works
Objects exist in the R session

Example:

example <- 123
ls()

[1] "example"

What does not work

The session never becomes attached.
The status bar always remains
R: (not attached)
The Global Environment pane stays empty.

Clicking the status bar executes

.vsc.attach()

which returns

Error in .vsc.attach() :
    could not find function ".vsc.attach"
Diagnostics

The VS Code environment variables are present.

Sys.getenv("TERM_PROGRAM")

returns

vscode
interactive()

returns

TRUE
Sys.getenv("VSCODE_INIT_R")

points to

C:\\Users\\davellb\\.vscode\\extensions\\reditorsupport.r-2.8.8\\R\\session\\init.R

The startup hook appears to be installed correctly.

identical(.First.sys, base::.First.sys)

returns

FALSE

Printing .First.sys shows the VS Code replacement function, including

exports$.vsc.attach()

However,

search()

never contains

tools:vscode

and

exists(".vsc.attach")

returns

FALSE
Additional information

I also created

C:\Users\<user>\.Rprofile

containing

if (interactive() && Sys.getenv("RSTUDIO") == "") {
    source(file.path(
        Sys.getenv("USERPROFILE"),
        ".vscode-R",
        "init.R"
    ))
}

The file is sourced successfully, but the behavior does not change.

It appears that .First.sys is successfully replaced, but the Session Watcher never completes initialization and .vsc.attach is never exported.