Scenarios & what-if analysis.

#1. What a scenario is

A scenario carries per-node duration overrides on top of the baseline. Everything else — resources, calendars, decision probabilities, costs, distributions, topology — is inherited unchanged.

Selecting a scenario in the Scenarios tab runs deterministic CPM against the modified project. Useful when:

• You want to compare layouts — force a parallel pair sequential, swap a chain’s order — without disturbing the working project.
• You want optimistic and pessimistic estimates as named alternatives, not as a single edit you’ll have to undo.
• You want to trial expediting a single activity as a quick what-if — a lightweight alternative to full crash modelling (see Cost modelling · Activity crashing).

Scenarios run a single CPM each, not a Monte Carlo. The Simulate tab is where stochastic forecasts live; the Scenarios tab is where point-estimate variations live.

#2. Creating a scenario

The Scenarios tab opens with Baseline pre-selected in the left panel — that’s the unmodified working project. Click + New to add a scenario. It’s created with an auto-incrementing name (“Scenario 1”, “Scenario 2”, …); rename in place, hover for the trash icon to remove.

A project can hold up to 1,000 scenarios. Names don’t have to be unique, but you’ll want them to be — the comparison panel identifies a scenario by name alone.

#3. Per-node duration overrides

With a scenario selected, the right panel shows two regions: Comparison on top, Duration overrides below.

Each override is one row: the node name, the baseline duration struck through, and the new duration as an editable input plus unit selector. To add an override, pick a node from the Add node override dropdown (it lists nodes you haven’t overridden yet) and click Add. The dropdown copies the baseline duration in as the starting value so you only change what you actually want to change.

Override only the durations you want to vary. Anything you don’t override flows through from the baseline unchanged.

#4. Baseline vs scenario comparison

The Comparison panel at the top of the scenario view runs deterministic CPM on both the baseline and the scenario and lays them out side-by-side.

• Project end date. Baseline date, scenario date, and the working-day delta. Negative deltas (scenario finishes earlier) tint green; positive deltas (scenario finishes later) tint red.
• Critical path. Both paths shown as ordered chips. When the path changes, a banner flags it — the longest path through the network is now different, even if the calendar-day delta is small.
• Override summary. Each overridden node listed with its before-and-after duration. Quick orientation for what’s actually different.

The numbers are deterministic CPM — single-point estimates run through the calendar and dependency network. They don’t reflect distributions or Monte Carlo variance. For a P80-vs-P80 comparison, apply the overrides to the working project and re-run Monte Carlo from the Simulate tab.

#5. Limitations

Scenarios override durations only. The following are inherited from the baseline and can’t currently be varied per scenario:

• Distributions. Activities keep their baseline distribution.
• Resource assignments. Same resources, same counts, same per-resource calendars.
• Working calendars. Project calendar and per-resource calendars are inherited verbatim.
• Decision-node probabilities. Pass probabilities and failure delays are inherited.
• Costs. Resource rates, fixed costs, and crash-option selection are inherited.
• Topology. Edges, sub-system membership, and loop wrapping are inherited — scenarios vary numbers, not shape.

To compare layouts that differ structurally (different edges, different sub-system membership, different loop wrapping), branch the project file: save baseline, save-as the variant, edit, and compare via two open tabs.