You'll noticeTier: how much it should matter to you
1Useful: my rating, 1 to 5
1Signal: worth watching, 1 to 5
PermissionsArea: what it touches
ImprovementsKind: in v2.1.309,
ImprovementsSection of the release
Unclear It is not stated which kinds of file read this blocking applies to.
What
On Linux, special paths under /proc and /dev give access to a running program's details. Claude Code now treats these as blocked reads:
/proc/self/cwd, /proc/self/fd, /proc/self/environ, /proc/self/cmdline and similar paths such as auxv, maps and smaps
/dev/fd and /dev/stdin
/proc/*/root
It follows working-folder links to their real location before checking.
Why
These paths can expose secrets, such as environment variables holding passwords or tokens, without naming the real file. Blocking them closes that indirect way round read restrictions.
How sure we are
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubtIt is not stated which kinds of file read this blocking applies to.
Anthropic's release notes agreeFixed Read reporting "File does not exist" for PDF page ranges in Linux sandboxes that share the parent's /proc
