Deployment testing for coding agents

Know what happens before you deploy,
on a disposable production twin.

Give your coding agent a production twin through MCP. Test migrations, user flows, and load on masked data, then use the findings to fix the change before you ship.

Isolated TwinYour stack, isolatedfor each change.
Safe StateMasked Postgres.Relationships intact.
Side-Effect FirewallTest payments and mail.Contain external calls.
LoadYour traffic mix.Against the new build.
Migration SafetyLocks, rewrites, plans.Before you deploy.

See Antifailure catch a costly migration.

Follow a schema change from pull request to rehearsal. See the lock it holds, the finding it produces, and the environment being removed.

A copy of production, same size and shape
Your change runs there first
Then the copy deletes itself

Migration Safety
Isolated Twin
Safety properties
Load
Side-Effect Firewall

Catch the migration that stalls your app. Your agent can rehearse it before you deploy.

AntifailureMigration rehearsal

Recorded orders demo

023_widen_total_cents.sqlSQL

1ALTER TABLE orders

2 ALTER COLUMN total_cents

3 TYPE bigint;

While this lock is held

read ordersmust wait

write ordersmust wait

Antifailure finding

Table rewrite

This change makes reads and writes wait.

The type change rewrites the orders table under an ACCESS EXCLUSIVE lock. Reads and writes to orders wait until PostgreSQL releases it.

Affected table: orders
Lock type: ACCESS EXCLUSIVE

Inspect measured evidence

orders: ≥10.5s
orders_pkey: ≥5.0s
orders_customer_id_idx: ≥2.2s

Sampled lower bounds on the demo database.

What the agent receives

The MCP result carries the finding, measured lock, and evidence. Your agent has something concrete to fix before merge.

Returned to your coding agent through MCPrehearse_migration_safety → get_rehearsal_run

Original finding from a recorded demo rehearsal. The lock duration is a sampled lower bound; the revised plan is illustrative and has not been measured here.

Compare both migration outcomes

Original migration

The type change rewrites orders under an ACCESS EXCLUSIVE lock. Reads and writes wait while it is held. The recorded demo measured a lock on orders for at least 10.5 seconds.

Agent's proposed revision

Add a new bigint column, backfill in batches, cut over reads and writes, and remove the old column later. This is a proposal, not a passing result. Rehearse the revision before merge.

Your stack. Your data shape. One isolated run. Give each change its own environment, then remove it when testing ends.

Environments

An isolated copy of your app for each change.

antifailure/demo-orders

Environment	Branch	State
demo-orders-default-side-eff-e3aa26	Branch: default (side-effect baseline)#1	Torn down
demo-orders-default-27b977	Branch: default#1	Torn down
demo-orders-drop-the-per-mer-faeda1	Branch: drop-the-per-merchant-scope-on-order-reads	Failed

Antifailure console, adapted for this preview. Selected demo environments.

Isolated networking
Each twin has its own network. Gateway policies control which external services it can reach.
Safe credentials
Use test credentials and route payments, messages, and other external calls through your test policies.
Cleanup proof
Review the teardown record to see which tracked resources were removed.

Make the call with evidence. Review what ran, what failed, and how to reproduce it.

Fail closed.

Unknown destinations are denied inside the twin, and an unverified golden cannot be branched.

Traffic shaped like production's.

The route mix out of your own access log, with the worst regression first.

Pass or fail, with evidence.

A gate on the pull request carrying the rows and the trace behind it.

Test the routes your users rely on. Replay your production traffic mix against the new build.

Your Code Editor

// The application. Antifailure needs no import in it.
export default async function handler(req, res) {
  const subs = await db.query(
    "select * from subscriptions where account_id = $1",
    [req.accountId],
  );

  res.status(200).json(subs);
}

Getting started with Antifailure···

Three commands. af init reads the repository and writes the manifest, af up builds the twin around a branch of the golden, af test runs the workflows and returns verdicts with evidence. With a production database, af golden refresh once before af up.

terminal$ af init
$ af up
$ af test
# verdicts, with evidence

Try for yourself, start proving a change before it ships.

ExampleExample project using the Antifailure CLI.

Test payments without charging customers. Check emails without sending them to users.

AntifailureSide-effect firewall

Interactive policy example

Outbound requestinside the twin

Your application tries to reach

api.stripe.com

POST/v1/charges

amount 49.00 USD

The request reaches the twin's egress policy before it can leave.

Policy decision

Mock

Checkout completes. Nobody gets charged.

The app receives a simulated payment response from the local pack. The real processor never receives this test charge.

Test receiptSimulated

$49.00real charge: none

Your agent sees the policy decision and observed counts through inspect_egress_firewall.

Back to your agent as a structured resultPolicy · observed decisions · findings

Illustrative policy decisions, not live customer telemetry. If the decision log cannot be read, Antifailure returns INCONCLUSIVE rather than claiming zero effects.

Compare all three policy outcomes

Payment mocked

A POST to api.stripe.com receives a local simulated response. The test checkout continues without a real processor charge.

Email captured

A POST to api.sendgrid.com is retained in the test inbox. The message can be inspected without sending it to a customer.

Production API blocked

A POST to the unlisted api.prod.internal host matches no rule. The default block policy refuses it before it can touch the live service.

Built for your infrastructure

Realistic tests.
A clear boundary.

Keep production data in your cloud while your team reviews results in the control plane.

Explore the data boundary →

01
Mask data in your infrastructure
Replace customer details and credentials before a test environment uses the database. A signed attestation records the masking checks.
02
Control external calls
Choose sandboxes, mocks, or captured messages for each integration. The gateway blocks destinations you have not configured.
03
Track the environment to teardown
Every created resource is recorded in a journal. Cleanup uses that record to remove the environment and report the outcome.

Antifailure + your coding agent

Test the change.
Then make the call.

See Antifailure rehearse a change from your stack. Review the findings, then decide what to ship.

Request a demo Connect your agent

Know what happens before you deploy, on a disposable production twin.