> ## Documentation Index
> Fetch the complete documentation index at: https://docs.mutagent.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Trace viewer

> /trace — a read-only viewer over your session logs: list sessions, open one, walk its trajectory. Available in every mode.

`/trace` opens a viewer over the session logs on your machine — Helix sessions and, where present,
plain Pi and Claude Code sessions too. Pick a session and walk it: step by step, or as a waterfall
of real durations. It is read-only — nothing in it re-runs, steers, deletes, or writes to
a session file — which is what makes it safe to open on a live run. It works in every mode.

```bash theme={null}
helix        # then type: /trace
```

<Note>
  Looking for where **Evaluate** reads its evidence? That's [Traces](/helix/traces) — a different
  thing that shares the name.
</Note>

<Frame caption="Where /trace opens: every session on the machine, one row each — project, harness, model, duration, turns and sub-agents.">
  <img src="https://mintcdn.com/architech/HQbLuNnglP7czETc/images/helix/trace-sessions.png?fit=max&auto=format&n=HQbLuNnglP7czETc&q=85&s=e5f53b8bcf88f287aee2fbd567e8e585" alt="The trace viewer's session list: a header counting ten indexed sessions across one harness, then ten rows spanning three projects — checkout-api, pricing-engine and docs-site — each row carrying the session id, harness, model, start time, a duration ranging from 2.6 seconds to 6 minutes 30, a turn count, and a sub-agent count on the two sessions that dispatched any." width="2780" height="930" data-path="images/helix/trace-sessions.png" />
</Frame>

<Frame caption="The waterfall: four sub-agents dispatched in parallel, each lane a real duration — what ran long, what waited on what.">
  <img src="https://mintcdn.com/architech/HQbLuNnglP7czETc/images/helix/trace-waterfall.png?fit=max&auto=format&n=HQbLuNnglP7czETc&q=85&s=5da8673893af3a287b23c015e651aaf3" alt="The trace viewer's waterfall screen for a demo session: a header with spans, turns, model wait and idle time, a time axis from 0s to 2m31s, four Agent dispatch spans, four long parallel sub-agent lanes of different lengths, and the assistant message spans between them." width="2698" height="1172" data-path="images/helix/trace-waterfall.png" />
</Frame>

## Screens

| Screen               | Shows                                                                                                                                                                                                                      |
| -------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Sessions**         | Every session across every harness that writes logs, one row each: harness, model, duration, turns, context used, sub-agent count. Press `2` for **lanes** — every session as a bar aligned at t=0 — and `1` to come back. |
| **Trajectory** (`1`) | The selected session step by step — messages, tool calls, sub-agent dispatches. What your agents *did*, not what they said they did.                                                                                       |
| **Waterfall** (`2`)  | The same session as timed spans, with real per-step durations — what ran long, what waited on what.                                                                                                                        |
| **Inspect**          | One span in full; `←`/`→` (or `h`/`l`) step to the previous / next span without leaving.                                                                                                                                   |

<Frame caption="The trajectory: the same session step by step — dispatches, sub-agent rows, and per-step tokens, cost and timing.">
  <img src="https://mintcdn.com/architech/HQbLuNnglP7czETc/images/helix/trace-trajectory.png?fit=max&auto=format&n=HQbLuNnglP7czETc&q=85&s=33a7fd32f1d0eaadf36bce7f18462242" alt="The trace viewer's trajectory screen: numbered rows for user, assistant, tool and sub-agent entries with token counts, cost and relative timestamps, including four Agent dispatch rows and their four sub-agent children." width="2698" height="1588" data-path="images/helix/trace-trajectory.png" />
</Frame>

## Keys

| Key               | Does                                                                            |
| ----------------- | ------------------------------------------------------------------------------- |
| `↑` `↓` · `j` `k` | Move. `PgUp`/`PgDn` jump ten; `g`/`G` top / bottom.                             |
| `Enter`           | Open the selected session or span.                                              |
| `→` · `←`         | On Sessions: fold a session's sub-agent children out and back.                  |
| `1` · `2`         | Swap between the dense view and the timing view of whatever you are looking at. |
| `Esc`             | Back one level (on Sessions, clears the filter first). Never quits.             |
| `?`               | Key help.                                                                       |
| `q`               | Close the viewer.                                                               |