Validation errors and how to fix them

Logic Builder checks the structure of your flow before it treats the run as valid.

That is helpful, because most failures come from flow shape problems, not from mysterious bugs.

The most important validation rules

The current builder expects:

• exactly one Start block
• a Start block that connects to a next step
• every Decision block to have a question
• every Decision block to connect both Yes and No branches
• every block to belong to the main reachable path
• at least one reachable End block
• no reachable branch that stops without a valid next block or end

What “exactly one Start” really means

You cannot build a valid learner flow with:

• zero starts
• two different starts

If you copied ideas around the canvas and accidentally left another start block behind, remove the extra one before doing anything else.

What happens with disconnected blocks

If a block sits on the canvas without becoming part of the real path, validation can fail.

That usually means one of two things:

• the block has no incoming connection
• the block belongs to a separate mini-flow that never joins the main path

The fix is not always “delete it.” Sometimes the right fix is simply connecting it to the intended path.

Decision-specific fixes

Decision nodes are stricter than other nodes.

A valid decision should have:

• a clear yes/no question
• a Yes connection
• a No connection

If only one branch is connected, the flow may still look understandable to you, but it is incomplete to the simulation system.

Dead-end branches

A path can still fail validation even if it starts correctly.

This happens when:

• one branch reaches no next block
• one branch never reaches an End
• one reachable path simply stops

In practice, that means each meaningful branch needs a believable way to finish.

Good repair sequence

When validation blocks a run:

1. count your Start blocks
2. inspect each Decision question
3. verify both Yes and No paths are connected
4. check whether every visible block is connected to the main path
5. confirm that at least one reachable End exists
6. look for any branch that still has nowhere valid to go

This is faster than randomly redrawing parts of the flow.

Best learner habit

Save a simple valid version before turning one path into a more complex branching tree.

That way, if validation starts failing later, you can compare the current broken version with a known-good one.