Make Router vs If-Else: when branches converge and when they dont

TL;DR

Picking the wrong one silently dr [official Make skills repo, real gotcha]: use the wrong branching tool and bundles go down the wrong path silently. If-Else + Merge: use when branches are mutually exclusive and converge.

Steps

1. [official Make skills repo, real gotcha]: use the wrong branching tool and bundles go down the wrong path silently.
2. If-Else + Merge: use when branches are mutually exclusive and converge. Only one branch fires per bundle, then both rejoin the same downstream modules. Example: if the alert came from Slack, send a Slack reply; else send WhatsApp; then update the row in both cases.
3. Router: use when branches are independent endpoints or several can be true at once. Each route runs its own chain. Router routes cannot merge back into one flow afterward.
4. Rule of thumb: "exactly one of these, then continue together" is If-Else; "any number of these, each doing its own thing" is Router. When agents generate blueprints, getting this wrong is the most common structural bug in scenario JSON.

When to use

You are seeing this: If-Else + Merge is for mutually exclusive branches that converge (only one fires per bundle, downstream modules shared). Use this skill when you run into "Make Router vs If-Else: when branches converge and when they dont".

When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

Web, official Make skills repo (github.com/integromat/make-skills, CLAUDE.md patterns): Router vs If-Else is a real design decision. If-Else + Merge is for mutually exclusive branches that converge (only one fires per bundle, downstream modules shared). Router is for independent endpoints where multiple routes can fire at once, and router routes cannot merge back. Picking the wrong one silently drops or duplicates work.

Verified resolution: [official Make skills repo, real gotcha]: use the wrong branching tool and bundles go down the wrong path silently.

If-Else + Merge: use when branches are mutually exclusive and converge. Only one branch fires per bundle, then both rejoin the same downstream modules. Example: if the alert came from Slack, send a Slack reply; else send WhatsApp; then update the row in both cases.

Router: use when branches are independent endpoints or several can be true at once. Each route runs its own chain. Router routes cannot merge back into one flow afterward.

Rule of thumb: "exactly one of these, then continue together" is If-Else; "any number of these, each doing its own thing" is Router. When agents generate blueprints, getting this wrong is the most common structural bug in scenario JSON.

Source: https://github.com/integromat/make-skills/blob/HEAD/CLAUDE.md