# Stage: trim

## Purpose

Produce a final-trimmed transcript. By default, the stage generates bounds and
applies a bounds-driven trim.

## Inputs

- `transcripts/final.json`

## Outputs

- `transcripts/final.trimmed.json` (or configured trim output path)
- when trim enabled: `artifacts/session_bounds.json`

## Key Behavior

When `trim.enabled=true`:
- runs Scriptorium bounds artifact generation;
- optionally runs render-debug output generation;
- validates bounds payload against transcript;
- derives keep selector;
- either copies unchanged transcript or runs Seriatim trim;
- validates trimmed transcript and materializes bounds output.

When `trim.enabled=false`:
- copies normalized transcript to trimmed output.

## Invariants

- normalized transcript is required input.
- bounds output exists only in enabled trim path.
- render-debug output is diagnostic and not a declared stage output.

## Related Contracts And Tests

- [Scriptorium](../integrations/scriptorium.md) owns bounds generation and
  debug-render subprocess behavior.
- [Seriatim](../integrations/seriatim.md) owns transcript trimming behavior.
- [Configuration](../config.md#pipeline) owns trim fields and defaults.
- Implementation and tests: `internal/stage/trim.go`,
  `internal/stage/trim_test.go`