10 common BPMN mistakes and how to fix them

By Emilis Mikalajūnas · Published July 8, 2026

Most BPMN mistakes come down to a handful of rule-breaks: wrong flow types, unbalanced gateways, and missing events. None are hard to fix once you know them. Here are the ten that trip people up most, with the rule for each.

1. Solid arrows between pools

Mistake: drawing a sequence flow (solid arrow) from one pool to another. Fix: communication between pools uses a message flow (dashed arrow). Sequence flows stay inside one pool.

2. Splitting without merging

Mistake: a gateway splits the flow into branches that never come back together. Fix: balance every split with a matching join of the same type. A parallel split (+) needs a parallel join; otherwise branches never synchronise.

3. Unlabelled decision branches

Mistake: an exclusive gateway with two outgoing arrows and no conditions on them. Fix: label each branch ("approved" / "rejected") and set a default path so the flow can't get stuck.

4. Making gateways do the work

Mistake: writing the decision logic inside the gateway ("Manager reviews and approves"). Fix: the work happens in a task before the gateway ("Review request"); the gateway only routes based on the result. Gateways never do anything.

5. Missing end events

Mistake: flows that just stop, with no end event. Fix: every path should reach an explicit end event. It signals the process is complete and makes the diagram valid.

6. Too many start events (or none)

Mistake: several start events with unclear triggers, or no start event at all. Fix: usually one clear start event per process, typed by its trigger (message, timer). If genuinely multiple triggers start it, be explicit about each.

7. Mixing levels of detail

Mistake: one task says "Handle order" while another says "Click the confirm button." Fix: keep tasks at a consistent granularity. Hide detail in a sub-process rather than mixing coarse and fine steps on one diagram.

8. Using the wrong task type

Mistake: every activity is a plain task. Fix: distinguish user tasks (a person), service tasks (a system), and manual tasks (offline) where it aids understanding. See the symbol reference.

9. Modelling exceptions on the happy path

Mistake: cramming every error and timeout into the main flow, making it unreadable. Fix: use boundary events (a timer or error event on the edge of a task) to handle interruptions off to the side, keeping the main path clean.

10. Spaghetti layout

Mistake: crossing flows, arrows going right-to-left, no clear direction. Fix: lay the process out left-to-right, minimise crossings, and align elements. Readability is part of correctness.

The shortcut: let the rules be enforced for you

Every mistake above is a rule an experienced modeller internalises — or that a good tool enforces automatically. BPMN Studio generates diagrams that follow these rules (balanced gateways, correct flow types, end events, left-to-right auto-layout) from a plain-English description, so beginners get valid BPMN without memorising the rulebook first. Then compare the result against this list to learn why it's built that way. Next: how to create a BPMN diagram and gateways explained.