Forecast change explainability (RM-007)

When comparing two forecast runs, AccuPredix explains why a series changed using deterministic rules — no LLM.

Where to find it

Compare → Compare runs — pick two completed runs in the same workspace. On Growth+ plans, the Why did it change? card appears below the forecast overlay.

What it considers

Driver	Source
Model change	best_model in series summary
External indicators	LightGBM feature importance + indicator month-on-month change
Seasonality	High lag12 feature weight
More history	n_obs increased between runs
Cold-start graduation	is_cold_start cleared
Trend shift	trend_label changed

API

GET /runs/{current}/compare/{prior}/forecast-explain?unique_id=&min_delta_pct=5

Returns plain-language narrative and ranked drivers per series.

Tier

Growth and Agency (forecast_explain feature).