# MTG Python Deckbuilder v2.5.0

## Summary
- Partner suggestion service and API power Step 2 suggestion chips for partner, background, and Doctor pairings when `ENABLE_PARTNER_SUGGESTIONS` is active.
- Headless runner now honors partner/background inputs behind the `ENABLE_PARTNER_MECHANICS` feature flag and carries regression coverage for dry-run resolution.
- Web builder Step 2 exposes partner/background pairing when `ENABLE_PARTNER_MECHANICS` is active, including live previews and warnings for invalid combinations.
- Quick-start modal mirrors the Step 2 partner/background controls so fast deck builds can choose a secondary commander or background without leaving the modal.
- Partner mechanics UI auto-enables for eligible commanders, renames the secondary picker to “Partner commander,” layers in Partner With defaults with opt-out chips, adds Doctor/Doctor’s Companion pairing, and keeps modal/theme previews in sync.
- Deck exports now surface combined commander metadata across CSV/TXT headers and JSON summaries so dual-command builds stay in sync for downstream tooling.

## Added
- Partner suggestion dataset loader, scoring service (`code/web/services/partner_suggestions.py`), FastAPI endpoint, UI chips, dataset override env (`PARTNER_SUGGESTIONS_DATASET`), auto-regeneration when the dataset is missing, and tests covering dataset flattening plus API responses.
- CLI regression coverage (`code/tests/test_cli_partner_config.py`) verifying partner/background dry-run payloads and `ENABLE_PARTNER_MECHANICS` env gating in the headless runner.
- Web build wizard toggle for partner mechanics with partner/background selectors, auto-pair hints, warnings, and combined color preview behind the feature flag.
- Partner and background selections now render card art previews (with Scryfall links) in the quick-start wizard, Step 2 form, and deck summary so builders can confirm the secondary pick at a glance.
- Quick-start modal now renders shared partner/background controls (reusing `_partner_controls.html`) whenever a commander that supports the mechanic is inspected.
- Background catalog loader (`code/deck_builder/background_loader.py`) with memoized parsing, typed entries, and a generator utility (`python -m code.scripts.generate_background_cards`) plus coverage to ensure only legal backgrounds enter the catalog.
- Shared `CombinedCommander` aggregation and partner/background selection helper wired through deck builds, exports, and partner preview endpoints with accompanying regression tests.
- Script `python -m code.scripts.build_partner_suggestions` materializes commander metadata, theme indexes, and observed pairings into `config/analytics/partner_synergy.json` to seed the partner suggestion engine.
- Partner suggestion scoring helper (`code/deck_builder/suggestions.py`) with mode-specific weights and regression tests ensuring canonical pairings rank highest across partner, background, and Doctor flows.
- Export regression coverage (`code/tests/test_export_commander_metadata.py`) verifies commander metadata is embedded in CSV/TXT headers and summary payloads while preserving existing columns.
- Partner suggestion telemetry emits `partner_suggestions.generated` and `partner_suggestions.selected` logs (via `code/web/services/telemetry.py`) so adoption metrics and dataset diagnostics can be monitored.

## Changed
- Partner controls hydrate suggestion chips on the web builder and quick-start modal, fetching ranked partner/backdrop recommendations while respecting active partner mode and session locks when `ENABLE_PARTNER_SUGGESTIONS=1`.
- Partner suggestion scoring now filters out broad "Legends Matter", "Historics Matter", and Kindred themes when computing overlap or synergy so recommendations emphasize distinctive commander pairings.
- Headless runner parsing now resolves `--secondary-commander` and `--background` inputs (mutually exclusive), applies the shared partner selection helper ahead of deck assembly, and surfaces flag-controlled behavior in exported dry-run payloads.
- Step 2 submission now validates partner inputs, stores combined commander previews/warnings in the session, and clears prior partner state when the toggle is disabled.
- Quick-start `/build/new` submission resolves partner selections, persists the combined commander payload, and re-renders the modal with inline partner errors when inputs conflict.
- Partner controls mount automatically for eligible commanders, replace the manual toggle with a hidden enable flag, rename the select to “Partner commander,” and expose an opt-out chip when Partner With suggests a default.
- Commander catalog metadata now flags Doctors and Doctor’s Companions so selectors present only legal pairings and annotate each option with its role.
- Partner detection now distinguishes the standalone “Partner” keyword from Partner With/Doctor’s Companion/restricted variants, and the web selector filters plain-partner pools to exclude those mechanics while keeping direct Partner With pairings intact.
- Structured partner selection logs now emit `partner_mode_selected` with commander color deltas, capturing colors before and after pairing for diagnostics parity.
- Structured partner selection logs now tag suggestion-driven selections with a `selection_source` attribute to differentiate manual picks from suggestion chip adoption.
- Commander setup now regenerates `background_cards.csv` alongside `commander_cards.csv`, ensuring the background picker stays synchronized after catalog refreshes or fresh installs.
- Setup/tagging auto-refresh now runs the partner suggestion dataset builder so `config/analytics/partner_synergy.json` tracks the latest commander catalog and deck exports without manual scripts.
- CSV/TXT deck exports append commander metadata columns, text headers include partner mode and colors, and summary sidecars embed serialized combined commander details without breaking legacy consumers.
- Partner commander previews in Step 2 and the build summary now mirror the primary commander card layout (including hover metadata and high-res art) so both selections share identical interactions.
- Editorial governance CI stages lightweight catalog fixtures when `EDITORIAL_TEST_USE_FIXTURES=1`, avoiding the need to sync `config/themes/catalog` into source control.

## Fixed
- Regenerated `background_cards.csv` and tightened background detection so the picker only lists true Background enchantments, preventing "Choose a Background" commanders from appearing as illegal partners and restoring background availability when the CSV was missing.
- Restricted partner commanders with dash-based keywords (e.g., Partner - Survivors, Partner - Father & Son) now register as partners and surface their matching group pairings in the web selector.
- Quick-start modal partner previews now merge theme tags with Step 2 so chips stay consistent after commander inspection.
- Step 5 summary and quick-start commander preview now surface merged partner color identity and theme tags so pairings like Halana + Alena display both colors.
- Partner and background builds now inject the secondary commander card automatically, keeping deck libraries, exports, and Step 5 summaries in sync with the chosen pairing.
- Partner With commanders now restrict the dropdown to their canon companion and the preview panel adopts the wizard theme colors for better readability while live-selection previews render immediately.
- Manual partner selections now persist across the wizard and quick-start modal, keeping recommendations and theme chips in sync without needing an extra apply step.
- Background picker now falls back to the commander catalog when `background_cards.csv` is missing so “Choose a Background” commanders remain selectable in the web UI.
- Partner hover previews now respect the secondary commander data so the popup matches the card you’re focusing.
- Step 5 summary and finished deck views now surface the deck’s chosen themes (and commander hover metadata) without flooding the UI with every commander tag.
- Doctor’s Companion commanders now surface only legal Doctor pairings, direct Partner With matches (e.g., Amy & Rory) remain available, and escaped newline text no longer breaks partner detection.
- Partner suggestion refresh now re-attempts dataset generation when triggered from the UI and ensures the builder script loads project packages inside Docker, so missing `partner_synergy.json` files can be recreated without restarting the web app.