aspex simulate - Aspex

aspex simulate --remove-server playwright
aspex simulate --restrict-filesystem filesystem=~/projects/acme
aspex simulate --deny-network '*'
aspex simulate --remove-tool desktop-commander.start_process

simulate clones your environment in memory, applies a hypothetical change, recomputes capabilities and attack paths through the same pipeline as a real scan, and compares before with after. Your configuration is never touched; the last line of every run says so.

What you can change

Flag	Effect
`--remove-server NAME`	drop a configured server
`--restrict-filesystem [SERVER=]ROOT[,ROOT]`	replace a filesystem server’s allowed roots (omit `SERVER=` for every filesystem server)
`--deny-network [SERVER\|*]`	remove network egress, as an allowlist of nothing would
`--remove-tool SERVER.TOOL`	drop one tool from a live tool list
`--remove-hook EVENT`	remove lifecycle hooks for an event
`--remove-skill NAME`	remove a skill

Flags are repeatable and combine, so you can evaluate a whole hardening change at once.

Output

$ aspex simulate --restrict-filesystem filesystem=~/projects/acme

  ◆  Security impact simulation
     • restrict filesystem to ~/projects/acme

  BEFORE   blast radius HIGH   6 attack path(s)
  AFTER    blast radius MEDIUM 2 attack path(s)

  REMOVED ATTACK PATHS
     ✓ Potential sensitive data exfiltration path  CRITICAL · filesystem + playwright
     ✓ Potential persistent agent compromise path  CRITICAL · filesystem + brave-search

  SEVERITY CHANGED
     ~ Potential sensitive data exfiltration path (filesystem + github): HIGH → MEDIUM

  Capability changes
     ~ filesystem  roots /Users/you → /Users/you/projects/acme

  No configuration was modified.

--json emits the versioned aspex-simulate/v1 schema: before/after environments, capability deltas, and attack paths added and removed.

Where simulation shows up elsewhere

aspex explain "…" ends every YES answer with the controls that break the path, each simulated so you see which one removes it on its own.
aspex tighten runs each recommendation through the simulator and shows its security impact next to the functional impact.
aspex inspect <command|path> simulates adding a server you have not installed yet.
aspex mcp exposes aspex_simulate_change so your coding agent can check a proposed .mcp.json before it writes it.

All four share this one engine, so the numbers agree everywhere.