Add a Research-Backed Timeline Event with Astro and YAML

TL;DR

An interactive timeline is only as useful as the evidence behind each event. In this tutorial, you will add a new milestone to The History of AI-Assisted Development, a public MIT-licensed Astro site. The workflow is deliberately small: edit one YAML collection, attach a primary source, run the repository's build checks, and inspect the generated page.

The same pattern works for release histories, standards timelines, migration guides, and other documentation sites where the data should remain easy to review.

Prerequisites

You need:

• Node.js installed on your machine
• pnpm 9.15.0, matching the repository's packageManager field
• Git
• A primary source for the milestone you want to document

The repository currently declares version 1.0.0 and uses Astro 5, React 19, Tailwind CSS 4, Mermaid 11, and TypeScript 5. The exact dependency versions are resolved by pnpm-lock.yaml, so use the lockfile when installing.

Clone the project and install its locked dependencies:

git clone https://github.com/paladini/history-of-ai-assisted-development.git
cd history-of-ai-assisted-development
pnpm install --frozen-lockfile

Find the timeline data

The repository keeps timeline events in content/timeline/events.yaml. The rendering code consumes this collection and turns the records into the interactive timeline. You do not need to edit an Astro component for a normal event.

The project also documents the content contract in CONTENT_GUIDE.md. Every event requires a unique identifier, an ISO date, one of the supported era IDs, a title, a two or three sentence summary, a category, and at least one Tier 1 source.

The source policy is important. A primary announcement, official repository, or authoritative survey is stronger than a secondary article repeating the same claim. If you only have an approximate date, use the first day of the month and say that the date is approximate in the summary.

Add one event

Open content/timeline/events.yaml and add a record with the existing indentation style. Here is a complete example for an event that can be verified against the official Model Context Protocol repository. The date and era are part of the site's content model, while the source URL gives a reader a path to the underlying evidence.

- id: mcp-open-source-release
  date: 2024-11-25
  era: protocols-standards
  title: "Model Context Protocol is released as an open standard"
  summary: "Anthropic publishes the Model Context Protocol as an open standard for connecting AI applications to external tools and data sources. The release gives developers a documented protocol boundary instead of relying only on provider-specific integrations."
  category: protocol
  sources:
    - label: "Model Context Protocol repository"
      url: "https://github.com/modelcontextprotocol"

Before saving, check each field:

• id is unique and uses lowercase kebab case.
• date uses YYYY-MM-DD.
• era exactly matches one of the six IDs in the content guide.
• category is one of tool, protocol, concept, culture, or data.
• summary explains what happened without claiming more than the source supports.
• sources contains at least one usable URL.

The example is a data change, not an invitation to copy a historical claim blindly. Read the linked source yourself and adjust the wording if its scope, date, or terminology differs.

Validate the result locally

The repository provides a verification script that installs dependencies, runs the build, and checks that the static output exists. Run it after editing the YAML:

pnpm build:verify

For a direct production build, run:

pnpm build

The build should finish successfully and generate the static site in dist/. The project currently builds the home page, about page, data page, and glossary routes. The timeline is part of the home page, so a successful build confirms that the collection was parsed and the page was generated.

To inspect the result in a local browser, start Astro's development server:

pnpm dev

Then open the local URL printed by Astro. Use the timeline controls to locate the new event and verify the visible title, date, era, summary, category, and source link.

Why this workflow works

The data and presentation have separate responsibilities. YAML makes the historical record readable in a pull request, while Astro components handle layout and interaction. That separation keeps a content correction small and reduces the chance of breaking the interface while adding research.

The source list also makes review concrete. A reviewer can check whether the event date is supported, whether the summary distinguishes a protocol from a product, and whether the chosen era is reasonable. A link is not proof by itself, but a visible source gives the reviewer something specific to evaluate.

The locked install matters too. pnpm install --frozen-lockfile prevents the local dependency graph from silently changing while you validate the content. This is especially useful for a static site with several client-side visualization packages, because a content edit should be tested against the same dependency resolution used by the repository.

Common failure modes

The build reports malformed YAML

Check indentation, quoting, and list markers. YAML treats indentation as structure. A missing space after - or an inconsistent nesting level can prevent the content collection from loading.

The event does not appear

Confirm that the record is in content/timeline/events.yaml, not a similarly named file. Check that its era value exactly matches the documented IDs and that the date is a valid ISO date. Then restart the development server if its content watcher did not reload the file.

The source is weak or ambiguous

Replace a search result or commentary article with the original announcement, official repository, specification, or survey. If the original source does not establish the exact date, make the date approximate and say so. Do not fill gaps with confident prose.

The page builds but the claim is still wrong

Build validation checks structure and rendering. It does not fact-check dates, assess source quality, or detect a misleading summary. Historical review remains a human responsibility, supported by the source policy and pull request discussion.

Limitations and security boundaries

This workflow produces a static site. It does not create a database, authenticate users, or fetch remote sources during the build. The source links are references for readers; they are not automatically verified by the repository's build command.

The example uses public URLs and contains no credentials. Keep tokens, private research notes, and unpublished material out of events.yaml and the repository. A public timeline should describe public evidence only. Review external links before merging because a link can lead to content that changes after the event is recorded.

FAQ

Do I need to know Astro?

No. For a normal milestone, the documented YAML record is enough. Astro knowledge becomes useful when changing the timeline layout, adding filters, or modifying the generated pages.

Can an event have multiple sources?

Yes. Add more entries under sources when independent primary sources clarify different parts of the claim. Keep the summary concise and make each source relevant.

Does pnpm build verify links?

It verifies the site's build, but you should not treat that as proof that every external URL is reachable or authoritative. Check important links separately during review.

Can I add a new era?

Not through an event record alone. Era IDs are part of the site's model and the content guide. A new era may require coordinated changes to data, types, and presentation, so open a focused change that documents the design decision.

Takeaway

A research-backed timeline entry can be a small, reviewable change: one YAML record, one or more primary sources, and a reproducible build. The valuable habit is not merely knowing the syntax. It is preserving the chain from a historical claim to evidence that another person can inspect.

What is the most useful validation you would add next: automated link checks, a schema-level date validator, or a review report for events missing Tier 1 sources?

AI assistance disclosure

AI assistance was used to help organize and edit this tutorial. The repository documentation, current package metadata, source policy, and build commands were checked against the public project before publication. The historical example should still be reviewed against its linked primary source.