Buyer guide · agentic harnesses
How to roll out an agentic harness without losing review discipline
A staged rollout pattern for teams that want speed without turning generated patches into unowned production risk.
Who this is for: Engineering managers, platform teams, and tech leads rolling out agentic coding assistants to a team of five or more without weakening branch protection, review gates, or security posture.
What actually matters
- Pilot scope: start with low-risk repos (internal tools, docs, test-heavy services) before production-critical paths.
- Branch protections and required reviewers stay on — agents are accelerators, not merge authorities.
- One portable project-memory file (AGENTS.md) prevents instruction drift when multiple harnesses read different configs.
- MCP and shell access need an allowlist reviewed by security before any server reaches shared repos.
- Parallel agents require git worktrees or dedicated branches so two sessions do not overwrite the same files.
- Measure accepted patch rate, review minutes, retries, and spend — not raw autocomplete volume.
ACE recommendation
Start with a small repository test set, keep branch protections intact, publish one AGENTS.md source of truth, restrict MCP to a short allowlist, and ship the review checklist with the tool choice.
Set up the shortlist
Useful comparisons
How to run this decision
- 01Select two pilot repositories with good test coverage and active human reviewers.
- 02Publish AGENTS.md with test commands, forbidden paths, branch policy, and secret-handling rules.
- 03Restrict MCP to a short org allowlist; document approval flow for new server requests.
- 04Run a two-week pilot with explicit tasks (fix bug, add test, small refactor) and log outcomes per developer.
- 05Ship a review checklist alongside the tool: plan, tool log, diff, tests, rollback path before merge.
- 06Expand seat count only after pilot metrics show net time savings without rising defect escape rate.
Common pitfalls
- Org-wide rollout on day one without a pilot repo or success criteria.
- Disabling branch protection because “the agent runs tests.”
- Letting every developer install arbitrary MCP servers without security review.
- Running two agents on the same branch without worktrees — duplicate edits and lost work follow.
- Treating instruction files as optional; harnesses without context produce confident wrong patches.
Ask before you buy
- What repository tasks are safe for a first pilot?
- Which commands require explicit approval or a human pair?
- What will you measure: accepted patch rate, review time, retries, or spend?
- Where does project memory live so Cursor rules / CLAUDE.md / AGENTS.md stay portable?
- How will parallel agents use git worktrees without colliding on the same branch?
- Which MCP servers are allowed, and who reviews tool trust / folder access before install?
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