Files
fusion/plugins/fusion-plugin-acp-runtime
gsxdsm de3156e4ad fix(ci): per-package timing files, acp flake timeout, 4040-guard marker
- ci-test-shard: timing outputFile is now RELATIVE — one pnpm invocation
  fans out to several packages whose vitests all received the same
  absolute path, so every package overwrote the same timings file (last
  writer wins). Each package now writes <pkgDir>/.timings/; discovery
  (discoverWorkspaceTimingFiles) and the CI artifact globs scan the tree
- acp event-bridge-bounds: 20s timeout on the CPU-bound plan-flood test
  (timed out at default 5s under loaded CI shard, passes in isolation)
- acp process-manager: port-4040-allowlist marker for its doc comments
  (main-side; local guard flagged it after merging main)
2026-06-03 20:34:51 -07:00
..

@fusion-plugin-examples/acp-runtime

A Fusion runtime plugin that drives any external Agent Client Protocol (ACP) agent over JSON-RPC/stdio. One integration unlocks every ACP-compatible agent (Gemini CLI, the Claude Code ACP adapter, and any future agent that speaks the protocol) through the standard protocol instead of a bespoke per-CLI integration.

Selected via runtimeId: "acp". Installed on demand (experimental) — see the Fusion plugin catalog (fn plugin install fusion-plugin-acp-runtime).

Security posture

The ACP agent is an untrusted subprocess that calls back into Fusion for permissions and filesystem access. This plugin enforces a defense-in-depth floor:

  • Per-category permission gating. Each session/request_permission is classified by tool kind into a Fusion action category and checked against the live permission policy — never a preset shortcut. allow_once only (never a persisted blanket grant). Unmappable kinds and missing policy default-deny.
  • Unrestricted-risk acknowledgement (acpAllowUnrestricted). Because the shipped default policy is unrestricted (allow-all), a blanket allow on a sensitive category is escalated to approval unless the user explicitly sets acpAllowUnrestricted: true. Prefer running the ACP runtime under an approval-required policy.
  • Filesystem jail. fs/read_text_file / fs/write_text_file are opt-in (acpFsRead / acpFsWrite, writes default OFF), confined to the session cwd by a real symlink-resolving jail (realpath + O_NOFOLLOW), with a deny-list for secrets (.env, *.pem, …) and git internals (.git/**). Writes are gated through the file_write_delete permission category.
  • Untrusted-input bounds. Streamed output is sanitized (ANSI/control strip) and bounded (per-turn + per-chunk caps; bounded tool-call correlation map).
  • Subprocess isolation. The agent env is built from an allow-list (acpEnvAllowList) — inherited process.env is not forwarded.

Not sandboxed in v1: the agent's own process/network syscalls run with Fusion's user privileges (OS-level sandboxing is recommended future work).

Settings

Key Default Meaning
acpBinaryPath acp-agent Agent binary to spawn
acpArgs [] Args that launch the agent in ACP/stdio mode (e.g. ["--acp"])
acpModel — Optional model identifier reported via describeModel
acpFsRead false Advertise/register fs/read_text_file
acpFsWrite false Advertise/register fs/write_text_file (gated)
acpEnvAllowList [] Env var names forwarded to the agent subprocess
acpAllowUnrestricted false Acknowledge the untrusted-agent risk under an allow-all policy

Upstream / third-party integration evidence

Per AGENTS.md (External-integration evidence):

See docs/acp-contract.md for the launch/readiness contract and failure taxonomy.