Scope Guard

Scope Guard

Scope Guard is a Copilot-native way to reduce blast radius. It combines explicit file ownership, prompt-level boundaries, and approval checkpoints so the agent treats one area as writable and everything else as read-only unless you reopen the scope.

Why This is Copilot-Exclusive

Copilot CLI now has native preToolUse/postToolUse hooks that can allow/deny tool calls (see guides/hooks-to-github-actions.md), but scope-guard is still the right pattern when you want a boundary enforced through the planning/approval flow itself rather than a separate hook script. It combines several useful primitives:

• Plan Mode approval before execution starts
• Task delegation where each agent gets its own brief
• Prompt-scoped ownership for exact paths, files, and stop conditions

This skill packages those primitives into a repeatable guardrail pattern for risky or tightly scoped work.

When to Use

• Production code, infrastructure, migrations, auth, billing, or other high-risk surfaces
• Refactors that should stay inside one directory or file set
• Parallel agent work where each agent must own a separate writable area
• Tasks that may involve destructive commands and need a pause before execution

When NOT to Use

Prerequisites

• Know the exact writable path or file list
• Decide what counts as a risky command for this task
• Have a rollback path if the work matters enough to isolate further

Modes

Workflow

1. Define the writable surface

Name the exact path, file set, or ownership boundary before any edits begin:

Only modify files under src/payments/.
You may read other files for context, but do not edit, create, or delete anything outside that path.

If the task spans multiple owned areas, list them explicitly. Compare scope using normalized real paths: a symlink can make a path that looks in-scope resolve outside the approved boundary.

2. Choose the mode

Careful when the surface is broad but the commands are risky:

Work across the approved files normally, but stop and ask before any destructive command,
dependency change, schema migration, force push, or file deletion.

Treat wrapper-prefixed commands as the same risk as the underlying command. env ..., sudo ..., watch ..., ionice ..., and setsid ... do not make a risky action safe. Likewise, treat find -exec and find -delete as explicit stop-and-review cases, not routine discovery commands.

Freeze when the path boundary matters more than the command type:

You may only write to docs/api/.
Read other files if needed, but do not edit outside docs/api/.

Guard when both constraints matter:

Use Guard mode for this task.
Writable surface: infra/terraform/.
Stop and ask before any delete, rename, state import, or other destructive infrastructure action.

3. Add a plan checkpoint for risky work

For high-risk changes, review the plan before execution:

Enter Plan Mode first.
List every file you expect to touch and any risky commands you might need.
Do not execute until that scope is approved.

This turns the plan itself into the first guardrail.

Approval scope is now enforced per location by the CLI itself. In a repository that means the current repo root, so if you switch repos with /cd, command approvals do not carry over — re-approve in the new repo instead of assuming the previous boundary still applies.

4. Re-brief each delegated agent separately

Do not assume one agent's scope automatically applies to another. Restate the ownership boundary for every background or parallel agent:

Owned path: packages/billing/
Do not touch shared CI, lockfiles, or docs.
If the fix requires an out-of-scope edit, stop and report the blocker.

5. Remove the guard explicitly

When the restriction is no longer needed, say so plainly:

Scope restriction removed. You may now edit any necessary files for the next task.

Do not rely on the agent to infer that the boundary changed.

Practical Guardrails

• Name both the allowed paths and the forbidden shared surfaces
• Tell the agent what to do on a scope violation: stop and report
• Pair large or destructive tasks with a branch or worktree
• Review the diff before merging, even when the guard held
• Write risky-command rules in terms of the real action, not only the first token. For example, sudo rm -rf, env NODE_ENV=prod npm run migrate, and find . -delete should all follow the same pause rules as their underlying destructive command

Related Skills

• plan-mode-mastery — approve file scope before execution
• autopilot-patterns — run autonomously after the boundary is clear
• fleet-parallel — assign separate writable surfaces per agent
• using-git-worktrees — move from logical scope limits to physical checkout isolation