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Sweep 22 Oct 2026 · 04:32Z Build v2.1.308 527 read Stable v2.1.308 Latest v2.1.308 Next v2.1.308 Feeds RSS JSON llms.txt llms-full.txt Unofficial
Home / Reference / Settings keys

sandbox.failIfUnavailable

setting never mined documented JSON

A Claude Code settings key, read out of the shipped bundle. No mined inventory carries it: everything below comes from what this site has written about it.

Refuse to start when the sandbox can't, instead of running unsandboxed

Anthropic's own wording. Read off All settings, captured 2026-10-22.

First seen — never in a mined build
Last seen — never in a mined build
Builds0 / 149on this box, as of v2.1.308
Written about v2.1.83 first named in a changelog, 24 Mar 2026

In the changelogs

8

Releases whose published page names sandbox.failIfUnavailable.

  1. v2.1.305
    On Windows, the sandbox's local connection setting is fixed when the sandbox is installed

    On Windows, changing sandbox.network.allowLocalBinding now needs /sandbox install and a restart, and Claude Code warns when they disagree

    found in this entry's text

  2. v2.1.285
    Claude Code can refuse to run without the sandbox in more cases

    Refusing to run when the sandbox is unavailable can now be triggered by another condition as well as sandbox.failIfUnavailable

    found in this entry's text, named in this entry

  3. v2.1.283
    A bad sandbox setting no longer switches off the whole sandbox block

    Invalid sandbox settings are now handled one field at a time, falling back to the restrictive value instead of the whole block being ignored

    found in this entry's text

  4. v2.1.251
    Eval runs that grant a shell tool now refuse to run without a sandbox

    Eval runs with a shell tool refuse to start without a sandbox, and hide your credential files.

    found in this entry's text

  5. v2.1.251
    Sandbox shell errors are merged into one readable message

    Repeated sandbox shell errors collapse into one readable message.

    named in this entry, found in this entry's text

  6. v2.1.248
    Claude Code can refuse to start when the sandbox is unavailable

    Set sandbox.failIfUnavailable to make Claude Code exit instead of running without a sandbox.

    named in this entry, found in this entry's text

  7. v2.1.91
  8. v2.1.83
    sandbox.failIfUnavailable Setting

    found in this entry's text

First cited

2

The earliest release whose published evidence quoted sandbox.failIfUnavailable was v2.1.248, 27 Aug 2026. That is the oldest release this project wrote about it, so it is a floor on the name's age and not the release that introduced it. It is not a presence reading: which builds carried the name is the table below.

ReleaseDateThe span that was quoted
v2.1.24827 Aug 2026sandbox.failIfUnavailable is set - refusing to start without a working sandbox.
v2.1.25128 Aug 2026Set sandbox.failIfUnavailable=false

Presence across releases

0

The miner has never read a build containing this name. It is here because a changelog entry of ours names it, which is evidence that it existed and not evidence of which releases carried it. The inventory starts at v2.1.138 and everything older than that was never mined.

Read out of the published npm bundle release by release, and out of Anthropic's own documentation as this site captured it. Nothing on this page is a description anybody here wrote about what the settings key does. All settings keys.

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