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

# Diff

> Compare two persisted runs side-by-side — status, output, journal head.

# Diff

`cmd/crewship/cmd_diff.go` takes two existing run IDs, fetches their state plus the last assistant message of each linked chat, and renders a terse before/after view. Distinct from `eval compare`, which re-runs an eval scenario on two tiers — `diff` works strictly on what already happened.

Use cases:

* "Did v2 of my routine actually fix the bug?" → diff before/after
* "What changed between Friday's prod run and Monday's regression?"
* "Did the agent give two different answers to the same prompt?"

Both runs are fetched in parallel; partial failures surface as `run-a <id>: <err>` or `run-b <id>: <err>`.

## `crewship diff <run-a> <run-b>`

| Flag     | Type | Default | Effect                                                                                    |
| -------- | ---- | ------- | ----------------------------------------------------------------------------------------- |
| `--full` | bool | `false` | Show full assistant output. Without it, each side is truncated to 1 KiB with an ellipsis. |

### Examples

```bash theme={null}
crewship diff r_abc r_def
crewship diff r_abc r_def --full
crewship diff r_abc r_def --format json     # both RunDetails + a_text/b_text in one object
```

### Output

Side-by-side headers (agent, status, started, finished) with status colours (green/red/yellow), then a minimal line-by-line diff of the assistant output:

```
Run A  r_abc
  agent  : viktor
  status : COMPLETED
  ...

Run B  r_def
  agent  : viktor
  status : FAILED
  ...

── Output diff ──
  Reviewed 3 files.
- All checks pass.
+ Linter warnings on src/auth.go:42.
```

The diff is intentionally not Myers — for run comparison users want the gist, not patch-applicable hunks.

## See also

* [`crewship eval compare`](/cli/eval) — re-run an eval scenario on two model tiers.
* [`crewship history`](/cli/history) — find the two run IDs.
* [`crewship explain <run-id>`](/cli/explain) — explain what one run did, with journal context.