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

Context: 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 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. 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.