Timeline / Gantt Builder from a Task Sheet

The problem this kills

You keep the plan in a spreadsheet because that's where the team actually works. But the moment a stakeholder asks "so when does this finish?" or "what's blocking the launch?", the spreadsheet falls apart. Columns of dates don't tell a story. You end up rebuilding the same picture by hand in slides, or paying for desktop PM software with a seat for everyone who only ever wants to look.

Worse, the dates lie. Someone changed a start date and never pushed the downstream tasks. Two tasks depend on each other in a loop nobody noticed. An end date sits before its start date. The plan looks fine until the day it doesn't.

This tool reads the sheet you already keep, checks it for the errors that quietly wreck schedules, recomputes dates from your dependencies, and draws the timeline for you - so the picture is always true and always one click to share.

What you'll build

A private web app where you:

• Import your task sheet (Google Sheet or CSV) - task, start, end, owner, dependency, and milestone flag.
• Validate it automatically - circular dependencies, end-before-start, and unknown dependency references are flagged before anything renders.
• Recompute the schedule - dates roll forward from dependencies so the timeline reflects reality, not stale typing.
• See the timeline - a clean Gantt view with milestones marked and the critical path highlighted (the chain of tasks that decides your finish date).
• Approve as PM - you review the computed schedule and any auto-resolved conflicts and click approve. Nothing is published or snapshotted until you do.
• Share and snapshot - publish a read-only shareable view, save a dated baseline snapshot to compare against later, and export the resolved schedule as CSV.

What's inside the Implementation Plan

• It starts by interviewing you about your business. Before a single line is built, the plan has the AI agent ask you how you run projects today, what your sheet's columns are really named, how you write task IDs, what your typical and peak task counts are, your working-week and holiday rules, and your messiest edge cases. It reflects a short tailored spec back to you for a thumbs-up - so you get a tool shaped to your plans, not a generic template.
• A clear definition of done, the exact accounts to set up, and the full stack.
• An architecture diagram in plain ASCII so you can see how the pieces fit.
• The build broken into copy-paste steps. Each step ends with a ready-to-paste prompt - the first one applies your interview answers to the data model and validations.
• A verification checklist and a no-API CSV fallback so the tool is fully buildable today, even if you never connect it to another system.

The governance it includes (this is the point)

This isn't a toy that anyone can scribble in. The plan builds in real controls from the start:

• Login so only your team can open the tool.
• Row-level security so each organization only ever sees its own projects and tasks.
• A complete audit trail - who imported, who edited, who approved, and exactly when.
• A hard human-in-the-loop approval gate - the tool drafts the recomputed schedule and flags conflicts; a person (the PM) reviews and approves before anything is published or a baseline is saved.
• Duplicate guards - tasks dedupe on task ID, and the same sheet can't be imported twice into the same snapshot by accident.

Who it's for

Project managers, coordinators, and team leads who already run their plans in spreadsheets but keep getting asked for a clean visual - the kind a stakeholder, an exec, or a client can read in five seconds. If you can keep a task list in a sheet, you can build and run this.

You've got this - paste the first prompt and let the agent interview you.