Cursor Agent Mode: Multi-File Refactors That Survive CI Gates

Cursor Agent Mode will happily rewrite twelve packages in one breath. That is the feature and the liability. The unfair advantage is not “let the agent cook” — it is constraining multi-file edits so every intermediate tree still typechecks, every CI gate that would run on main still passes on the agent branch, and a partial refactor can be quarantined or reverted without archaeology.

⚡ TL;DR: Scope Agent Mode with project rules + path allowlists; force plan → patch → verify loops tied to the same pnpm/turbo tasks CI uses; quarantine unfinished symbols behind feature flags or adapters; never merge a half-migrated public API. Treat agent branches like release candidates: targeted typecheck, affected tests, lint boundaries, and a one-command rollback. Pair with Cursor Rules for TypeScript Monorepos so the agent already knows your package law.

Plan with an explicit blast radius

Before any write, make the agent declare files, public API changes, and the verify commands. Reject plans that touch generated code, lockfiles without reason, or infra without a human.

// scripts/agent-plan-gate.ts — reject unbounded refactors
export type AgentPlan = {
  intent: string;
  files: string[];
  publicApiTouches: string[]; // package entrypoints
  verify: string[];           // exact CI-equivalent commands
  rollback: "git revert" | "feature-flag" | "adapter";
};

const FORBIDDEN = [
  /^pnpm-lock\.yaml$/,
  /\/generated\//,
  /\.github\/workflows\//,
  /infra\//,
];

export function assertSafePlan(plan: AgentPlan) {
  // ❌ Never: "refactor auth across monorepo" with empty file list
  if (!plan.files.length) throw new Error("empty_blast_radius");

  for (const f of plan.files) {
    if (FORBIDDEN.some((re) => re.test(f))) {
      throw new Error(`forbidden_path:${f}`);
    }
  }

  // ✅ Require verify cmds that mirror CI (turbo filter, not full monorepo)
  const hasTypecheck = plan.verify.some((c) => /typecheck|tsc/.test(c));
  const hasTest = plan.verify.some((c) => /test|vitest|jest/.test(c));
  if (!hasTypecheck || !hasTest) throw new Error("missing_ci_equivalent_verify");

  if (plan.publicApiTouches.length && plan.rollback === "git revert") {
    // Public API breaks need adapters or flags, not hope
    throw new Error("public_api_needs_adapter_or_flag");
  }
}

Encode the same constraints in .cursor/rules so Agent Mode never invents a second workflow. See also AI Code Review Bots: IAM, Secrets, and Least-Privilege Pipelines for how review bots should treat agent PRs as untrusted until gates pass.

Patch in layers, not one mega-diff

Multi-file survival means stacked, reviewable commits: types → implementation → callers → delete dead paths. One commit that both renames a symbol and deletes the old export is how you strand teammates mid-rebase.

# ✅ Layered agent workflow (illustrative)
pnpm turbo run typecheck --filter=@acme/auth...
pnpm turbo run test --filter=@acme/auth...

# ❌ Mega-diff anti-pattern
# agent edits 40 files, one commit, "fix CI later"

# .github/workflows/agent-pr.yml — same gates as main, scoped
name: agent-pr
on:
  pull_request:
    types: [opened, synchronize, labeled]
jobs:
  affected:
    if: contains(github.event.pull_request.labels.*.name, 'agent-refactor')
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with: { fetch-depth: 0 }
      - run: corepack enable && pnpm i --frozen-lockfile
      - name: Affected graph
        run: pnpm turbo run typecheck test lint --filter=...[origin/main]
      - name: Boundary lint
        run: pnpm eslint --max-warnings=0 $(git diff --name-only origin/main...HEAD -- '*.ts' '*.tsx')

Quarantine partial refactors

When the agent finishes half a migration, do not leave dual APIs forever. Introduce an adapter or @deprecated shim with a kill date, or flip a flag so callers stay stable.

// packages/auth/src/session.ts
/** @deprecated Remove after 2026-10-01 — use getSessionV2 */
export function getSession(req: Request): Session {
  // ✅ Temporary bridge — logs so you can count remaining callers
  metrics.increment("auth.session.v1_shim");
  return toV1(getSessionV2(req));
}

export function getSessionV2(req: Request): SessionV2 {
  return readSessionFromCookie(req);
}

// ❌ Wrong quarantine: silent dual paths with no metric, no deadline
export const getSession = process.env.NEW ? getSessionV2 : getSessionLegacy;

Roll back before main

Agent branches should be one command from clean. Prefer git revert of the merge commit for completed landings; for incomplete work, reset the branch and keep the plan artifact in the PR description.

# ✅ Safe rollback of a landed agent merge
git revert -m 1 <merge_sha>
pnpm turbo run typecheck test --filter=...[origin/main]

# ❌ Dangerous
git reset --hard origin/main  # on a shared agent branch others pull
git push --force

For cloud-side agents that can mutate infra, wrap tool execution the same way you would for Bedrock — see LLM Coding Agents on AWS: Safe Tool Sandboxes with Lambda and Amazon Bedrock Agents: Tool Use, Memory, and Production Guardrails.

CI gates the agent must never skip

Map every agent verify step to a named CI job. If CI uses Turborepo affected filters, the agent must too. If CI bans any, the agent must not silence with as unknown as.

Closing checklist

✅ Dos
– ✅ Force written blast radius + verify commands before writes
– ✅ Stack commits: types → impl → callers → delete
– ✅ Quarantine with metrics and kill dates
– ✅ Label agent PRs and run affected CI identical to main
– ✅ Keep one-command rollback rehearsed

❌ Don’ts
– ❌ Don’t let Agent Mode touch generated/, lockfiles, or workflows unattended
– ❌ Don’t merge dual public APIs without adapters
– ❌ Don’t accept eslint-disable or any as “temporary”
– ❌ Don’t force-push shared agent branches
– ❌ Don’t skip boundary lint because “types pass”

Related reading

• Cursor Rules for TypeScript Monorepos: Make AI Edits Stick
• LLM Coding Agents on AWS: Safe Tool Sandboxes with Lambda
• AI Code Review Bots: IAM, Secrets, and Least-Privilege Pipelines
• Amazon Bedrock Agents: Tool Use, Memory, and Production Guardrails

Last updated on September 11, 2026