n8n Reliability Lab

THE OPERATIONAL PROBLEM

A connected workflow can still have no failure contract.

Automation briefs often name tools without defining what happens to invalid input, duplicate delivery, transient failure, exhausted retries, or consequential writes. This lab makes those decisions explicit before credentials or integration nodes are introduced.

CONTROL PATH

Route first. Add side effects last.

1. 01
   Fixture

   Create five deterministic cases that exercise ready, duplicate, retry, and review outcomes.

2. 02
   Validate

   Reject missing required fields before a downstream action can be planned.

3. 03
   Route

   Suppress an in-run duplicate, bound retry planning, and promote exhausted or invalid work to review.

4. 04
   Verify

   Fail closed unless all seven outcome and safety invariants match the expected distribution.

VERIFICATION EVIDENCE

What was actually checked.

• 7 runtime invariants passThe final n8n node checks counts, duplicate effects, side effects, external actions, and execution capability.
• 5 fixtures are deterministicThe verified outcome distribution is ready / duplicate / retry / review = 1 / 1 / 1 / 2.
• A mutation guard fails closedThe independent Node test changes the expected distribution and confirms the final invariant node throws.
• Real local n8n executionThe workflow was imported and executed in n8n 2.26.8 on Node.js 24.14.0 using JavaScript Code nodes.
• Zero external actionsNo HTTP request, webhook, credential, external write, or message is present or executed.