Have Claude build a timeline visualizer for agents spawning subagents

Agent Viewer timeline of a main agent and two parallel subagents

@alexander__main started Harvard CS2680 assignment 1 (agent loop). Claude built them an "Agent Viewer" timeline UI that shows the main agent and parallel subagents with model/tool/subagent/error blocks over a ~1m16s run. Screenshot of the viewer is in the post.

Try it yourself

What you get

A timeline UI that shows when the main agent and subagents run model and tool calls.

Tools

Time / cost: Author: built for CS2680 assignment 1

Steps

  1. Export spans with start/end, kind (model/tool/subagent/error) and label.
  2. Ask for a dark timeline with a legend and per-row agents.
  3. Replay one known run and check the blocks match the log.
  4. Keep PII out of labels before sharing screenshots.

Copy-ready prompt

Build a small web "Agent Viewer" timeline from my agent traces. Rows for the main agent and each subagent. Colored blocks for model, tool, subagent and error spans. Show total time, model time, tool time and max concurrent subagents. Dark UI. Do not invent events — only plot the JSON I provide.

Prompt written by AgentPlays, based on @alexander__main’s post. Check the output yourself and approve before anything is sent or bought.

Watch out: Trace UIs can expose prompts and file paths. Redact before sharing.

Proof / source

Self-reported Author's public X post with Agent Viewer screenshot (Oct 14, 2026). Self-reported.

In their words

I've started Harvard's CS2680. Assignment #1: setting up and understanding the agent loop. Here is the visualizer Claude built me for watching agents spawning subagents in parallel, with tool calls, etc.

— @alexander__main on X

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