---
summary: "Exec approvals, allowlists, and sandbox escape prompts"
read_when:
  - Configuring exec approvals or allowlists
  - Implementing exec approval UX in the macOS app
  - Reviewing sandbox escape prompts and implications
title: "Exec Approvals"
---

# Exec approvals

Exec approvals are the **companion app / node host guardrail** for letting a
sandboxed agent run commands on a real host (`gateway` or `node`). Think of it
like a safety interlock: commands are allowed only when policy + allowlist +
optional user approval all agree.

Exec approvals are **in addition** to tool policy and elevated gating, unless
elevated is set to `full`, which skips approvals.

Effective policy is the **stricter** of `tools.exec.*` and approvals defaults.
If an approvals field is omitted, the `tools.exec` value is used.

If the companion app UI is **not available**, any request that requires a prompt is
resolved by the **ask fallback** (default: deny).

## Where it applies

Exec approvals are enforced locally on the execution host:

- **gateway host** → `fased` process on the gateway machine
- **node host** → node runner (macOS companion app or headless node host)

Trust model note:

- Gateway-authenticated callers are trusted operators for that Gateway.
- Paired nodes extend that trusted operator capability onto the node host.
- Exec approvals reduce accidental execution risk, but are not a per-user auth boundary.

macOS split:

- **node host service** forwards `system.run` to the **macOS app** over local IPC.
- **macOS app** enforces approvals + executes the command in UI context.

## Settings and storage

Approvals live in a local JSON file on the execution host:

`~/.fased/exec-approvals.json`

Example schema:

```json
{
  "version": 1,
  "socket": {
    "path": "~/.fased/exec-approvals.sock",
    "token": "base64url-token"
  },
  "defaults": {
    "security": "deny",
    "ask": "on-miss",
    "askFallback": "deny",
    "autoAllowSkills": false
  },
  "agents": {
    "main": {
      "security": "allowlist",
      "ask": "on-miss",
      "askFallback": "deny",
      "autoAllowSkills": true,
      "allowlist": [
        {
          "id": "B0C8C0B3-2C2D-4F8A-9A3C-5A4B3C2D1E0F",
          "pattern": "~/Projects/**/bin/rg",
          "lastUsedAt": 1737150000000,
          "lastUsedCommand": "rg -n TODO",
          "lastResolvedPath": "/Users/user/Projects/.../bin/rg"
        }
      ]
    }
  }
}
```

## Policy knobs

### Security (`exec.security`)

- **deny**: block all host exec requests.
- **allowlist**: allow only allowlisted commands.
- **full**: allow everything (equivalent to elevated).

### Ask (`exec.ask`)

- **off**: never prompt.
- **on-miss**: prompt only when allowlist does not match.
- **always**: prompt on every command.

### Ask fallback (`askFallback`)

If a prompt is required but no UI is reachable, fallback decides:

- **deny**: block.
- **allowlist**: allow only if allowlist matches.
- **full**: allow.

## Allowlist (per agent)

Allowlists are **per agent**. If multiple agents exist, switch which agent you’re
editing in the macOS app. Patterns are **case-insensitive glob matches**.
Patterns should resolve to **binary paths** (basename-only entries are ignored).
Legacy `agents.default` entries are migrated to `agents.main` on load.

Examples:

- `~/Projects/**/bin/peekaboo`
- `~/.local/bin/*`
- `/opt/homebrew/bin/rg`

Each allowlist entry tracks:

- **id** stable UUID used for UI identity (optional)
- **last used** timestamp
- **last used command**
- **last resolved path**

## Auto-allow skill CLIs

When **Auto-allow skill CLIs** is enabled, executables referenced by known skills
are treated as allowlisted on nodes (macOS node or headless node host). This uses
`skills.bins` over the Gateway RPC to fetch the skill bin list. Disable this if
you want strict manual allowlists.

Important trust notes:

- This is an **implicit convenience allowlist**, separate from manual path
  allowlist entries.
- It is intended for trusted operator environments where Gateway and node are in
  the same trust boundary.
- If you require strict explicit trust, keep `autoAllowSkills: false` and use manual path allowlist entries only.

## Safe bins (stdin-only)

`tools.exec.safeBins` defines a small list of **stdin-only** binaries (for example `jq`)
that can run in allowlist mode **without** explicit allowlist entries. Safe bins reject
positional file args and path-like tokens, so they can only operate on the incoming stream.
Treat this as a narrow fast-path for stream filters, not a general trust list.
Do **not** add interpreter or runtime binaries to `safeBins`, including
`python3`, `node`, `ruby`, `bash`, `sh`, or `zsh`.

If a command can evaluate code, execute subcommands, or read files by design,
prefer explicit allowlist entries and keep approval prompts enabled.
Custom safe bins must define an explicit profile in `tools.exec.safeBinProfiles.<bin>`.
Validation is deterministic from argv shape only (no host filesystem existence checks), which
prevents file-existence oracle behavior from allow/deny differences.
File-oriented options are denied for default safe bins (for example `sort -o`, `sort --output`,
`sort --files0-from`, `sort --compress-program`, `sort --random-source`,
`sort --temporary-directory`/`-T`, `wc --files0-from`, `jq -f/--from-file`,
`grep -f/--file`).
Safe bins also enforce explicit per-binary flag policy for options that break stdin-only
behavior (for example `sort -o/--output/--compress-program` and grep recursive flags).
Long options are validated fail-closed in safe-bin mode: unknown flags and ambiguous
abbreviations are rejected.
Denied flags by safe-bin profile:

- `grep`: `--dereference-recursive`, `--directories`, `--exclude-from`, `--file`, `--recursive`, `-R`, `-d`, `-f`, `-r`
- `jq`: `--argfile`, `--from-file`, `--library-path`, `--rawfile`, `--slurpfile`, `-L`, `-f`
- `sort`: `--compress-program`, `--files0-from`, `--output`, `--random-source`, `--temporary-directory`, `-T`, `-o`
- `wc`: `--files0-from`

Safe bins also force argv tokens to be treated as **literal text** at execution time (no globbing
and no `$VARS` expansion) for stdin-only segments, so patterns like `*` or `$HOME/...` cannot be
used to smuggle file reads.
Safe bins must also resolve from trusted binary directories (system defaults plus optional
`tools.exec.safeBinTrustedDirs`). `PATH` entries are never auto-trusted.
Default trusted safe-bin directories are intentionally minimal: `/bin`, `/usr/bin`.
If your safe-bin executable lives in package-manager/user paths (for example
`/opt/homebrew/bin`, `/usr/local/bin`, `/opt/local/bin`, `/snap/bin`), add them explicitly
to `tools.exec.safeBinTrustedDirs`.
Shell chaining and redirections are not auto-allowed in allowlist mode.

Shell chaining (`&&`, `||`, `;`) is allowed when every top-level segment satisfies the allowlist
(including safe bins or skill auto-allow). Redirections remain unsupported in allowlist mode.
Command substitution (`$()` / backticks) is rejected during allowlist parsing, including inside
double quotes; use single quotes if you need literal `$()` text.
On macOS companion-app approvals, raw shell text containing shell control or expansion syntax
(`&&`, `||`, `;`, `|`, `` ` ``, `$`, `<`, `>`, `(`, `)`) is treated as an allowlist miss unless
the shell binary itself is allowlisted.
For shell wrappers (`bash|sh|zsh ... -c/-lc`), request-scoped env overrides are reduced to a
small explicit allowlist (`TERM`, `LANG`, `LC_*`, `COLORTERM`, `NO_COLOR`, `FORCE_COLOR`).
For allow-always decisions in allowlist mode, known dispatch wrappers
(`env`, `nice`, `nohup`, `stdbuf`, `timeout`) persist inner executable paths instead of wrapper
paths. Shell multiplexers (`busybox`, `toybox`) are also unwrapped for shell applets (`sh`, `ash`,
etc.) so inner executables are persisted instead of multiplexer binaries. If a wrapper or
multiplexer cannot be safely unwrapped, no allowlist entry is persisted automatically.

Default safe bins: `jq`, `cut`, `uniq`, `head`, `tail`, `tr`, `wc`.

`grep` and `sort` are not in the default list. If you opt in, keep explicit allowlist entries for
their non-stdin workflows.
For `grep` in safe-bin mode, provide the pattern with `-e`/`--regexp`; positional pattern form is
rejected so file operands cannot be smuggled as ambiguous positionals.

### Safe bins versus allowlist

- Goal:
  - `tools.exec.safeBins`: auto-allow narrow stdin filters.
  - Allowlist: explicitly trust specific executables.
- Match type:
  - `tools.exec.safeBins`: executable name + safe-bin argv policy.
  - Allowlist: resolved executable path glob pattern.
- Argument scope:
  - `tools.exec.safeBins`: restricted by safe-bin profile and literal-token
    rules.
  - Allowlist: path match only; arguments are otherwise your responsibility.
- Typical examples:
  - `tools.exec.safeBins`: `jq`, `head`, `tail`, `wc`.
  - Allowlist: `python3`, `node`, `ffmpeg`, custom CLIs.
- Best use:
  - `tools.exec.safeBins`: low-risk text transforms in pipelines.
  - Allowlist: any tool with broader behavior or side effects.

Configuration location:

- `safeBins` comes from config: `tools.exec.safeBins` or per-agent
  `agents.list[].tools.exec.safeBins`.
- `safeBinTrustedDirs` comes from config: `tools.exec.safeBinTrustedDirs` or
  per-agent `agents.list[].tools.exec.safeBinTrustedDirs`.
- `safeBinProfiles` comes from config: `tools.exec.safeBinProfiles` or
  per-agent `agents.list[].tools.exec.safeBinProfiles`. Per-agent profile keys
  override global keys.
- allowlist entries live in host-local `~/.fased/exec-approvals.json` under
  `agents.<id>.allowlist`, or via Control UI / `fased approvals allowlist ...`.
- `fased security audit` warns with
  `tools.exec.safe_bins_interpreter_unprofiled` when interpreter/runtime bins
  appear in `safeBins` without explicit profiles.
- `fased doctor --fix` can scaffold missing custom `safeBinProfiles.<bin>`
  entries as `{}`. Review and tighten afterward. Interpreter/runtime bins are
  not auto-scaffolded.

Custom profile example:

```json5
{
  tools: {
    exec: {
      safeBins: ["jq", "myfilter"],
      safeBinProfiles: {
        myfilter: {
          minPositional: 0,
          maxPositional: 0,
          allowedValueFlags: ["-n", "--limit"],
          deniedFlags: ["-f", "--file", "-c", "--command"],
        },
      },
    },
  },
}
```

## Control UI editing

Use the **Control UI → Nodes → Exec approvals** card to edit defaults, per‑agent
overrides, and allowlists. Pick a scope (Defaults or an agent), tweak the policy,
add/remove allowlist patterns, then **Save**. The UI shows **last used** metadata
per pattern so you can keep the list tidy.

The target selector chooses **Gateway** (local approvals) or a **Node**. Nodes
must advertise `system.execApprovals.get/set` (macOS app or headless node host).
If a node does not advertise exec approvals yet, edit its local
`~/.fased/exec-approvals.json` directly.

CLI: `fased approvals` supports gateway or node editing. See
[Approvals CLI](/cli/approvals).

## Approval flow

When a prompt is required, the gateway broadcasts `exec.approval.requested` to
operator clients. The Control UI and macOS app resolve it via
`exec.approval.resolve`, then the gateway forwards the approved request to the
node host.

When approvals are required, the exec tool returns immediately with an approval
id. Use that id to correlate later system events (`Exec finished` /
`Exec denied`). If no decision arrives before the timeout, the request is
treated as an approval timeout and surfaced as a denial reason.

The confirmation dialog includes:

- command + args
- cwd
- agent id
- resolved executable path
- host + policy metadata

Actions:

- **Allow once** → run now
- **Always allow** → add to allowlist + run
- **Deny** → block

## Approval forwarding to chat channels

You can forward exec approval prompts to any chat channel, including plugin
channels, and approve them with `/approve`. This uses the normal outbound
delivery pipeline.

Config:

```json5
{
  approvals: {
    exec: {
      enabled: true,
      mode: "session", // "session" | "targets" | "both"
      agentFilter: ["main"],
      sessionFilter: ["discord"], // substring or regex
      targets: [
        { channel: "slack", to: "U12345678" },
        { channel: "telegram", to: "123456789" },
      ],
    },
  },
}
```

Reply in chat:

```
/approve <id> allow-once
/approve <id> allow-always
/approve <id> deny
```

### macOS IPC flow

```
Gateway -> Node Service (WS)
                 |  IPC (UDS + token + HMAC + TTL)
                 v
             Mac App (UI + approvals + system.run)
```

Security notes:

- Unix socket mode `0600`, token stored in `exec-approvals.json`.
- Same-UID peer check.
- Challenge/response (nonce + HMAC token + request hash) + short TTL.

## System events

Exec lifecycle is surfaced as system messages:

- `Exec running` (only if the command exceeds the running notice threshold)
- `Exec finished`
- `Exec denied`

These are posted to the agent’s session after the node reports the event.
Gateway-host exec approvals emit the same lifecycle events when the command
finishes, and optionally when running longer than the threshold.
Approval-gated execs reuse the approval id as the `runId` in these messages for easy correlation.

## Implications

- **full** is powerful; prefer allowlists when possible.
- **ask** keeps you in the loop while still allowing fast approvals.
- Per-agent allowlists prevent one agent’s approvals from leaking into others.
- Approvals only apply to host exec requests from **authorized senders**.
  Unauthorized senders cannot issue `/exec`.
- `/exec security=full` is a session-level convenience for authorized operators
  and skips approvals by design.
  To hard-block host exec, set approvals security to `deny` or deny the `exec` tool via tool policy.

Related:

- [Exec tool](/tools/exec)
- [Elevated mode](/tools/elevated)
- [Skills](/tools/skills)
