nightshift/docs/devlog/phase18.md

Phase 18 Devlog: Prompt and Pipeline Experiments

Implemented

• Added optional experiment.label and experiment.prompt_variant config fields.
• Snapshotted agent prompt files into runs/<run-id>/prompts/.
• Wrote run-metadata.md with project, experiment, agent backend, model, command, and prompt metadata.
• Included experiment metadata in final task reports and run summaries.
• Added tests for experiment config loading and prompt/metadata artifact creation.

Decisions Made

• Experiment metadata is descriptive only and does not alter execution semantics.
• Prompt snapshots are per-run, not per-task, because agent definitions are run-level configuration.

Notes

• This creates enough metadata to compare prompt/backend runs from artifacts without adding a database.