Add SessionStart hook to provision Erlang/Elixir/SWI-Prolog in cloud sessions - #6
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…sessions Cloud sessions start from a bare Ubuntu VM with none of the toolchain mix.exs and mise.toml expect, so mix test could not run there. The hook installs Erlang and SWI-Prolog via apt (archive.ubuntu.com is on the default network allowlist), unpacks a precompiled Elixir release from a GitHub release asset (github.com is also allowlisted), and installs Hex + rebar3 by building them from source via GitHub rather than mix's usual local.hex/local.rebar, which hit builds.hex.pm — not allowlisted by default. It then runs mix deps.get/compile so the project is ready when Claude starts working. That step still needs repo.hex.pm reachable to fetch this project's actual dependencies (req, jason, bandit, ...); if the environment's network access doesn't include it, the hook logs what's missing and exits 0 rather than failing the session. No-op outside CLAUDE_CODE_REMOTE, so local dev (mise-managed toolchain per README.md) is untouched.
The session now starts immediately while the toolchain installs in the background, instead of blocking on the ~1 minute install. Trade-off: a tool call that runs before the hook finishes won't have elixir/mix/swipl on PATH or the project's deps compiled yet.
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Cloud sessions start from a bare Ubuntu VM with none of the toolchain mix.exs
and mise.toml expect, so mix test could not run there. The hook installs
Erlang and SWI-Prolog via apt (archive.ubuntu.com is on the default network
allowlist), unpacks a precompiled Elixir release from a GitHub release asset
(github.com is also allowlisted), and installs Hex + rebar3 by building them
from source via GitHub rather than mix's usual local.hex/local.rebar, which
hit builds.hex.pm — not allowlisted by default.
It then runs mix deps.get/compile so the project is ready when Claude starts
working. That step still needs repo.hex.pm reachable to fetch this project's
actual dependencies (req, jason, bandit, ...); if the environment's network
access doesn't include it, the hook logs what's missing and exits 0 rather
than failing the session.
No-op outside CLAUDE_CODE_REMOTE, so local dev (mise-managed toolchain per
README.md) is untouched.