macOS Bash sandbox fails with spawn sandbox-exec ENOENT

[wbbb040610-ui]

OS: macOS
Node: v24.19.0
dsh: 0.1.0-rc.7

The Bash tool previously worked and could read/write files.

Now every Bash command fails with:
BashError: spawn sandbox-exec ENOENT

On the host macOS:

• /usr/bin/sandbox-exec exists
• which sandbox-exec returns /usr/bin/sandbox-exec
• Node spawn("sandbox-exec") succeeds
• Node spawn("/usr/bin/sandbox-exec") also succeeds

I also tested the dsh-sandbox-local Seatbelt implementation.
Changing the executable to /usr/bin/sandbox-exec still results in:
spawn /usr/bin/sandbox-exec ENOENT

This appears to be an issue with the Bash sandbox execution environment.

[denial123789]

I documented this as a provider-startup boundary rather than a file denial: host command -v sandbox-exec and direct Node spawns can succeed while the Harness Seatbelt provider still returns spawn ... ENOENT. The safe order is to preserve the failed call, capture bare vs absolute executable probes and provider path, then keep an unavailable backend fail-closed; do not silently retry the original effect with Full Access.

Independent SandBase handbook: https://sandbaseai.github.io/deepseek-harness-handbook/sandbox-denied-vs-unavailable.html#when-macos-says-spawn-sandbox-exec-enoent