Gantt / Roadmap Skill

A list of tasks doesn't show what runs in parallel, what blocks what, or where the crunch is. A Gantt chart does. This skill turns a plan into a Mermaid Gantt chart with phases (sections), dated tasks, dependencies, and milestones — a real schedule, not a wish list. Because the output carries real dates, the playground can also export it straight to a calendar (.ics).

Required Inputs

Ask for these only if they aren't already provided:

• The work — phases and tasks to schedule.
• Timing — a start date, and durations or end dates (or relative ordering you can date from the start).
• Dependencies — what must finish before what can start.
• Milestones — the dated checkpoints (kickoff, beta, GA, launch).

If exact dates aren't given, anchor to a start date and lay tasks out by stated duration/order; flag the dates as planning estimates.

Output Format

Project] — roadmap

One line on the time span and goal.

mermaid
gantt
    title [Project] roadmap
    dateFormat YYYY-MM-DD
    axisFormat %b %d
    section Discovery
        Research            :done,    r1, 2026-07-01, 10d
        Spec sign-off       :milestone, m1, 2026-07-15, 0d
    section Build
        Core build          :active,  b1, after m1, 20d
        Integrations        :         b2, after b1, 10d
    section Launch
        Beta                :milestone, m2, 2026-08-25, 0d
        GA                  :milestone, m3, 2026-09-10, 0d

Critical path — the chain of dependent tasks that sets the end date.

Risks / buffers — where the schedule is tight, what could slip, where buffer exists.

Assumptions — any dates you estimated rather than were given.

Mermaid Rules (so it renders)

• Start with gantt, then title, dateFormat YYYY-MM-DD, optional axisFormat.
• Group with section Name. Task line: Label : [status,] id, start, duration (e.g. :active, b1, 2026-07-01, 20d).
• Dependencies use after <id> as the start. Milestones use the milestone tag with 0d.
• Use real ISO dates (YYYY-MM-DD) so the calendar (.ics) export works.

Quality Checks

• ] Tasks are grouped into phases (sections) and have real start dates/durations
• ] Dependencies use after so the schedule reflects what blocks what
• ] Milestones are marked as milestones, not full-width bars
• ] The critical path is identified, with risks/buffers noted
• ] The Mermaid block renders, and dates are ISO so .ics export works

Anti-Patterns

• ] Do not list tasks with no dates or durations — that's a checklist, not a timeline
• ] Do not ignore dependencies — overlapping things that can't overlap is a fake plan
• ] Do not draw milestones as long bars — they're points in time
• ] Do not use ambiguous date formats — stick to YYYY-MM-DD
• ] Do not present estimated dates as commitments — flag assumptions

Based On

Project scheduling (Gantt charts, critical path, milestones, dependencies), expressed as renderable Mermaid.