Managing experiment lifecycle

This skill covers experiment state transitions — what each action does, when to use it, and how it affects variant assignment and analysis.

State diagram

draft ──launch──▶ running ──end──▶ stopped ──archive──▶ archived
                    │   ▲              │
                  pause resume    ship_variant
                    │   │         (also ends if running)
                    ▼   │
                  paused (flag inactive, still "running" status)

Any non-draft state ──reset──▶ draft

Actions and their implications

For each action, the two key questions:

1. Who sees what variant? (user perspective)
2. Who is in my analysis? (statistical perspective)

Launch (experiment-launch)

Transitions draft → running. Activates the feature flag and sets start_date.

• Preconditions: must be in draft, flag needs ≥2 variants with "control" first
• Pre-launch checklist: has at least one metric? Variants correct? Flag implemented in code?
• Variants: users start being bucketed into variants based on the configured split
• Analysis: data collection begins from start_date

No request body needed.

Pause (experiment-pause)

Deactivates the feature flag. Users fall back to the default experience (typically control).

• Preconditions: must be running and not already paused
• Variants: flag is not returned by /decide — no new exposure events recorded
• Analysis: no new data while paused, but existing data is preserved. Experiment stays "running".

No request body. Use experiment-resume to reactivate.

Resume (experiment-resume)

Reactivates the feature flag after a pause. Users are re-bucketed deterministically into the same variants.

• Preconditions: must be paused
• Variants: same assignment as before pause — deterministic bucketing
• Analysis: exposure tracking resumes

No request body.

End (experiment-end)

Sets end_date and transitions to stopped. The feature flag is NOT modified.

• Preconditions: must be running (launched, not already stopped)
• Variants: users continue seeing assigned variants (flag stays active)
• Analysis: results frozen to data up to end_date

Optional body: conclusion ("won", "lost", "inconclusive", "stopped_early", "invalid") and conclusion_comment.

Use this when you want to freeze results without changing what users see.

Ship variant (experiment-ship-variant)

Rewrites the feature flag so the selected variant is served to 100% of users.

• Preconditions: must be launched (running or stopped). Cannot ship from draft.
• Variants: ALL users see the shipped variant. The flag is rewritten with a catch-all group.
• Analysis: if still running, the experiment is also ended (end_date set)

Always confirm with the user before shipping — this permanently rewrites the feature flag.

Required: variant_key (e.g. "test"). Optional: conclusion, conclusion_comment.

Returns 409 if an approval policy requires review before the flag change.

Archive (experiment-archive)

Hides a stopped experiment from the default list view.

• Preconditions: must be stopped (end_date set)
• Variants: no change — flag is unaffected
• Analysis: no change — results remain accessible

No request body. Can be restored by setting archived=false via experiment-update.

Reset (experiment-reset)

Returns an experiment to draft state. Clears start_date, end_date, conclusion, and archived.

• Preconditions: must not already be in draft
• Variants: flag is left unchanged — users continue seeing assigned variants
• Analysis: previously collected data still exists but won't be included in results unless start_date is adjusted after re-launch

No request body.

Duplicate (experiment-duplicate)

Creates a copy as a new draft with fresh dates and no results.

Important: always provide a unique feature_flag_key different from the original. If the same key is used, both experiments share a flag — changes to one affect both.

Optional: custom name (defaults to "Original Name (Copy)").

Decision framework

Situation	Action	Tool
Draft ready, flag implemented, metrics set	Launch	experiment-launch
Clear winner, significant results	Ship the winning variant	experiment-ship-variant
No significant difference after sufficient time	End as inconclusive	experiment-end
Something wrong, need to stop exposure temporarily	Pause	experiment-pause
Resume after pause	Resume	experiment-resume
Experiment ended, ready to clean up	Archive	experiment-archive
Need to start over with same config	Reset to draft	experiment-reset
Want a similar experiment with a fresh start	Duplicate	experiment-duplicate

Resolving experiments

All lifecycle actions require an experiment ID. If you don't have one, load the finding-experiments skill to resolve the user's reference (name, description, "latest", etc.) to a concrete ID before proceeding.

Error handling

Error message	Meaning
"Experiment has already been launched."	Can't launch a non-draft experiment
"Experiment has not been launched yet."	Can't end/pause/ship a draft
"Experiment has already ended."	Can't end/pause a stopped experiment
"Experiment is already paused."	Use resume instead
"Experiment is not paused."	It's already active
"Experiment is already in draft state."	Nothing to reset
"Experiment is already archived."	Already done

When you get a 400, explain the situation to the user rather than retrying.