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CI fails now and then with "socket ... has insecure permissions 0o755". It hit run_embedded_exits_on_cancel on #14 and synchronous_startup_explicit_path_uses_parent_as_sandbox_root on #13. The socket gets its mode from the umask at bind time, and the umask is process-wide. synchronous_startup and four socket tests each did umask(077) / bind / umask(old) with no lock, and cargo test runs them on parallel threads. If one thread restores 022 between another thread's swap and its bind, that socket comes out 0755. The post-bind check then rightly refuses it. The swap now lives in bind_owner_only, behind a static mutex, and synchronous_startup and the tests both go through it. The lock is in production code, not a test-only mutex, so the integration test binaries that call synchronous_startup in parallel are covered too. The real daemon binds before any other thread exists, so it never waits on the lock. Stress run of `daemon::` lib tests, 200 iterations at 16 threads: 5 failures before, 0 after.
The daemon's socket, PID file and proxy CA certificate sit in the sandbox root, which the agent and every tool can write, and they clutter the repo. Separately, a single checked-in airlock.toml forces personal choices like where GH_TOKEN comes from into the shared file. The proposal moves runtime files to a per-user 0700 directory, layers a global and a gitignored local config over the repo file, and gates the repo and local files behind byte-exact approval (`airlock trust`) with a diff on refusal. It records each design choice with the rejected alternatives, and compares the trust model with `mise trust`.
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A review of the proposal against the code found gaps that would keep it from delivering its stated goals, or from working at all: project files give the agent deferred code execution outside the sandbox, approval does not cover the programs the config runs, the repo layer can reach personal secrets, any daemon is reachable from any sandbox, and the socket location is not stable (Linux agent env lacks XDG_RUNTIME_DIR, macOS $TMPDIR varies per shell). Record them as blocking items with a proposed direction each, list the non-blocking follow-ups, and capture one-daemon-per-user with session tokens as an open question. The Seatbelt rule-order check moves out of "to verify": sandbox-exec confirms the last matching rule wins, so the deny must be emitted after every allow.
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Design proposal only, no code: docs/runtime-and-config-design.md.
What it proposes
airlock.sock,airlock.pidandairlock-ca.pemout of the project into$XDG_RUNTIME_DIR/airlock/<id>/(Linux) or$TMPDIR/airlock/<id>/(macOS). The directory is per-user, mode 0700, and not writable from any sandbox. On macOS the proposal adds a Seatbelt deny rule, because the baseline grants all of$TMPDIR.~/.config/airlock/airlock.toml< repoairlock.toml< localairlock.local.toml.airlock trust. When they don't, startup refuses and prints an escaped diff. The global file is not approved; it is protected by where it lives.[env]or.envrc.airlock listasks the daemon instead of reading config files.--no-configbecomes--no-project-config(global layer only).trust,daemon start/stop/restartandrunrefuse inside the sandbox.The Decisions section lists each choice with the alternatives it rejected, and there is a comparison with
mise trust.🤖 Generated with Claude Code