Timeline

Renders interactive Gantt-style timelines and roadmaps in the browser using vis-timeline from context-supplied phases, milestones, and tasks.

Workflow

1. Extract items and groups — identify tasks/phases (items) and workstreams/swimlanes (groups) from context. See TEMPLATE.md for data shapes.
2. Convert all dates to ISO strings — translate every vague time reference ("month 1-3", "Q2", "next sprint") to "YYYY-MM-DD" format. Default base date is today. See TEMPLATE.md for conversion patterns.
3. Assign group colors — give each group a className and matching CSS color class. See TEMPLATE.md for the color class system.
4. Write the HTML file — write a complete self-contained file to /tmp/timeline.html using the vis-timeline template. See TEMPLATE.md for the full template.
5. Render in browser — follow _shared/chrome-devtools-render.md to open /tmp/timeline.html, wait for render, screenshot, and fix-and-reload if needed. wait_for a group label string that appears after vis-timeline renders. See TROUBLESHOOTING.md for timeline-specific fixes.

Self-review checklist

Before delivering, verify ALL:

• Screenshot shows all group swimlane labels in the left panel
• Screenshot shows colored item bars spanning correct date ranges
• No items are invisible or rendering as unstyled plain text (CSS CDN loaded)
• Timeline container has explicit pixel height — vis-timeline did not collapse to 0px
• All start/end values in items array are ISO date strings "YYYY-MM-DD", not relative strings
• Every item has a group property matching a group id
• stack: false is present in timeline options
• Dark theme CSS overrides are present and text is readable on dark background
• wait_for was called before take_screenshot

Golden rules

Hard rules. Never violate these.

1. Never use relative date strings. Always convert vague references ("month 1", "Q3", "next sprint") to explicit ISO date strings "YYYY-MM-DD" before passing to vis-timeline. Relative strings will throw a parse error or render at wrong positions.
2. Always set explicit pixel height on the container div. vis-timeline collapses to 0px without it. Use height: 500px; width: 100%; at minimum.
3. Always include the CSS CDN link tag. Without the vis-timeline CSS CDN, items render as unstyled plain text with no bar shape or color.
4. Use stack: true when items within a group overlap in time; use stack: false only when items are guaranteed non-overlapping. stack: false causes overlapping items in the same group to render on top of each other, hiding all but the topmost. Default to stack: true for safety.
5. Always assign every item to a group. Ungrouped items pile into a single unlabelled row, defeating swimlane separation.
6. Always call wait_for on a group label string before screenshotting. The group label only appears after vis-timeline fully renders; screenshotting before it appears captures a blank or partially-rendered page.
7. Always use new_page for first open. Use mcp__chrome-devtools__new_page with url: file:///tmp/timeline.html. Use navigate_page with type: reload only for subsequent fixes.

Reference files