The goal of this layer is not to make bidder mutations look durable. The goal is to make the current truth model explicit in code:

• canonicalRead remains the visible source for auction detail/list reads
• bidder mutations remain UI-FIRST and compatibility-backed
• session overlays remain explicit
• the future durable mutation seam remains visible and intentionally separate

VERIFIED module structure

Top-level entry:

• apps/web/src/portal/components/AuctionDetailClient.tsx

Controller / view-model layer:

• apps/web/src/portal/components/auctionDetail/useAuctionDetailController.tsx
• apps/web/src/portal/components/auctionDetail/useAuctionSessionOverlays.ts
• apps/web/src/portal/components/auctionDetail/useAuctionBidderIdentity.ts
• apps/web/src/portal/components/auctionDetail/compatibilityActionAdapter.ts

Presentation modules from Sprint 04:

• apps/web/src/portal/components/auctionDetail/AuctionReadPresentation.tsx
• apps/web/src/portal/components/auctionDetail/AuctionDeliveryOptionsPanel.tsx
• apps/web/src/portal/components/auctionDetail/AuctionBidActionCluster.tsx
• apps/web/src/portal/components/auctionDetail/AuctionBuyNowAction.tsx
• apps/web/src/portal/components/auctionDetail/AuctionFulfillmentPanel.tsx
• apps/web/src/portal/components/auctionDetail/AuctionCompatibilityNotice.tsx

Related cross-sprint boundaries:

• apps/web/src/ui/auctions/canonicalRead/portalReadBoundary.ts
• apps/web/src/ui/auctions/compatibility/sessionAuctionMutationPort.ts
• apps/web/src/ui/auctions/futureDurable/auctionMutationPort.ts
• apps/web/src/ui/auctions/session/bidOverlay.ts
• apps/web/src/ui/auctions/session/fulfillmentOverlay.ts
• apps/web/src/ui/auctions/session/transportSelectionOverlay.ts

Responsibility ownership

AuctionDetailClient.tsx

Status: MIXED, but intentionally thin after Sprint 05.

Owns:

• assembly of the page-level cards
• wiring controller outputs into presentation components
• no direct session storage reads
• no direct bidder mutation persistence logic

It is now a shell/orchestrator entry point, not the place where eligibility, overlay merge, or compatibility write logic is implemented.

useAuctionDetailController.tsx

Status: UI-FIRST controller/view-model layer.

Owns:

• derived auction detail view-model construction
• action availability and gating decisions
• bid guidance / buy-now state shaping
• delivery option render-state shaping
• fulfillment state shaping
• degraded-state normalization for the action surface
• compatibility-backed action handler wiring

It is intentionally the place where current truth is concentrated:

• reads come in through detail
• session overlays are merged in
• compatibility mutation calls are issued explicitly
• future durable mutation is not silently implied

useAuctionSessionOverlays.ts

Status: UI-FIRST.

Owns:

• hydration guard for client-only overlay use
• subscription to session-backed bid overlays
• subscription to session-backed buy-now state
• subscription to session-backed transport pre-commit selection
• subscription to session-backed fulfillment intent

This is the explicit session/local merge layer for the detail controller.

useAuctionBidderIdentity.ts

Status: MIXED.

Owns:

• current-session user resolution via useCurrentUser()
• stakeholder-context fetch via getMyStakeholderContext()
• manual dev bidder override handling when enabled
• bidder identity normalization for the action surface

This hook keeps session/account/stakeholder identity shaping out of the visual detail component.

compatibilityActionAdapter.ts

Status: UI-FIRST.

Owns:

• explicit adapter from detail controller to the compatibility mutation port

It currently maps to:

• apps/web/src/ui/auctions/compatibility/sessionAuctionMutationPort.ts

This is intentionally named as compatibility, not service, gateway, or API mutation.

What moved out of AuctionDetailClient

Sprint 05 extracted these responsibilities from the top-level component:

• session overlay subscription and hydration handling
• bidder identity resolution and stakeholder-context usage
• compatibility-backed action wiring
• large derived state and view-model construction
• top-level action gating and participation normalization

This means new engineers and future AI agents no longer need to read a single giant client component to find:

• where bid overlays come from
• how bidder identity is chosen
• where Buy Now or bid submission is wired
• how delivery and fulfillment action states are computed

What still remains intentionally centralized

Inside useAuctionDetailController.tsx:

• top-level derived controller state
• action handlers that coordinate multiple view-model concerns
• cross-panel logic where bid/buy/delivery/fulfillment need the same derived state

Inside AuctionDetailClient.tsx:

• page-level composition
• card ordering and top-level render branches

This centralization is intentional for now. Splitting further before a real durable mutation path exists would risk scattering the same UI-first truth across too many modules.

Truth model after Sprint 05

Canonical read

Status: REAL / MIXED depending on upstream source, unchanged by this sprint.

• auction detail/list reads still come through the canonical read boundary
• this sprint did not invent a new read source

Compatibility mutation

Status: UI-FIRST.

• bid submit
• Buy Now
• transport pre-commit selection
• fulfillment advancement

These still flow through the compatibility adapter to the session-backed mutation port.

Session overlays

Status: UI-FIRST.

• bid overlays
• buy-now overlays
• transport selection overlays
• fulfillment intent overlays

These remain explicit and isolated under ui/auctions/session/*.

Future durable mutation seam

Status: SHELL.

The durable seam still exists under:

• apps/web/src/ui/auctions/futureDurable/auctionMutationPort.ts

Sprint 05 did not implement it. The controller boundary now makes the eventual swap point much clearer.

What future durable mutation work should attach to

When a real bidder mutation backend is implemented later, the intended change point is:

1. keep AuctionDetailClient.tsx unchanged or nearly unchanged
2. keep presentation modules unchanged
3. replace the compatibility adapter wiring inside:
   • apps/web/src/portal/components/auctionDetail/compatibilityActionAdapter.ts
4. optionally update useAuctionSessionOverlays.ts if durable optimistic/revalidation behavior replaces session overlays

That is the main value of this sprint: the swap point is now explicit instead of buried inside a very large UI component.