# Run trace

A React component in [Beamline](https://beamline.io/)'s [AI & agents](https://beamline.io/components/ai) category. Live demo: https://beamline.io/components/run-trace

One agent run as a waterfall: every step (model calls, tools, retrieval, checks, sub-agents) nested under the step that started it, each a bar on a shared time axis, with retries as separate attempts on the same bar, tokens and cost per step and for the run; while it runs the bars grow live, and choosing a step shows its timing, attempts, input and output beside the trace.

## Use it for

- Debugging or reviewing an agent run: what ran, in what order, what waited on what, what failed and was retried, and what it cost.
- An observability page for model and tool calls (spans from your tracing).

## Not for

- A single tool call in a conversation ([tool-call](https://beamline.io/components/tool-call)).
- The agent's thinking in words ([reasoning](https://beamline.io/components/reasoning)).
- Background jobs a person follows ([task-rows](https://beamline.io/components/task-rows)).
- The designed workflow before it runs ([flowchart](https://beamline.io/components/flowchart)).

## Anatomy

- header: the run's status (a glyph and a word), total time, how many steps and how many failed, tokens in and out, cost
- axis: time marks across the lane (0, 2 s, 4 s…), a line at now while running
- row: indent and a chevron for steps with children, the kind's glyph (model, tool, retrieval, check, agent, wait), the name and the model; the bar on the lane from start to end in the kind's colour; failed attempts before it as hatched segments with a gap; the duration at the end
- selected step: the row ringed and a detail panel (beside the trace when wide, under it when narrow): name, kind, start and duration, attempts with their errors, tokens and cost, input and output
- running step: the bar's open end grows with time and carries a soft edge; the duration counts

## Variants

- **density**: compact, default

## States

- running (live)
- succeeded
- failed (the failing step and its parents are marked)
- retried
- cancelled
- collapsed
- selected
- empty (no steps yet)

## Keyboard

- The trace is a tree grid with one tab stop: ↑/↓ move between visible steps, → opens a step or goes to its first child, ← closes it or goes to its parent
- Home/End go to the first and last step; Enter or Space shows the step's detail
- Escape clears the selection

## Motion

New steps grow into the list and the rows below slide down (useFlip). While the run is live the open bars grow on a clock that runs only while something is running and the trace is on screen, then stops. Opening and closing a step folds its children. The detail cross-fades to the chosen step. Reduced motion: bars jump to their length each tick of the clock; nothing slides.

## Props

| Prop | Type | Default | Description |
| --- | --- | --- | --- |
| `spans` (required) | `TraceSpan[]` | — |  |
| `now` | `number` | — | ms since the run started, for live bars; omit to let the trace keep its own clock while a span is running. |
| `title` | `ReactNode` | — | The run's name (the request it answered). |
| `selected / defaultSelected / onSelectedChange` | `string \| null` | — |  |
| `expanded / defaultExpanded / onExpandedChange` | `string[]` | — | Open steps. Default: every step. |
| `density` | `"compact" \| "default"` | — |  |
| `currency` | `string` | — | Cost symbol. Default "$". |
| `className / classNames / style / ref` | `root` | — |  |

## Built from

- spinner

## Dependencies

`lucide-react`

## Import

```tsx
import { RunTrace } from "@/components/run-trace/run-trace";
```

## Get it

Run trace is part of Beamline: 200+ components and 50+ complete screens for React that your coding agent (Claude Code, Codex, Cursor or any MCP client) installs into your app through Beamline's MCP server, as a ready-built package or as plain React source you can change. $49 launch price, one payment, no subscription, lifetime updates, one licence for your whole team. [Get Beamline](https://beamline.io/checkout?pack=complete) · [Connect your agent](https://beamline.io/connect)

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