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+# Phase 19: Reference Item Model & Tags Schema - Context
+
+**Gathered:** 2026-04-05
+**Status:** Ready for planning
+
+<domain>
+## Phase Boundary
+
+Transform collection items from full data copies to reference pointers at global catalog entries. A reference item stores `globalItemId` + personal fields (categoryId, notes, purchasePriceCents, imageFilename, quantity); base data (brand, model, weight, MSRP, image, description) comes from the linked global item. Add a tag system so global items can be tagged for discovery and filtering. Update thread candidates to support `globalItemId`. Update thread resolution to create reference items with auto-link.
+
+</domain>
+
+<decisions>
+## Implementation Decisions
+
+### Reference Item Model
+- **D-01:** Add `globalItemId` (nullable FK → globalItems) directly to the `items` table. When set, the item is a "reference item" — base data comes from the global item.
+- **D-02:** Remove the `itemGlobalLinks` junction table entirely. It was a 1:1 relationship — a direct FK on items is simpler. Migrate existing link data first.
+- **D-03:** Personal fields on items remain: `categoryId`, `notes`, `imageFilename`, `imageSourceUrl`, `quantity`. Add `purchasePriceCents` (nullable integer) for what the user actually paid.
+- **D-04:** For reference items, `name`, `weightGrams`, `priceCents` on the items row are kept NULL or empty. The service layer merges global data when returning items.
+- **D-05:** Standalone items (no `globalItemId`) continue to work as before — fully self-contained with all fields populated. This is the "manual entry" path.
+
+### Merged Data Strategy
+- **D-06:** Service layer handles merging transparently. `getAllItems()` and `getItem()` join on globalItems when `globalItemId` is set, returning a unified shape. Clients see one type — no need to distinguish reference vs standalone.
+- **D-07:** API response shape stays the same as current Item type. Global data fills in name, weight, price, etc. for reference items. Personal overrides (if any exist) take precedence — but initially only the fields listed in D-03 are personal.
+- **D-08:** `productUrl` on reference items: comes from the global item's future `productUrl` field if added, otherwise NULL. For now, reference items may not have a product URL unless the global item has one. (Not critical — users can add to notes.)
+
+### Thread Candidates
+- **D-09:** Add `globalItemId` (nullable FK → globalItems) to `threadCandidates` table. Candidates added from catalog have this set.
+- **D-10:** Candidates with `globalItemId` display global item data (brand + model as name, weight, price, image). Personal candidate fields (notes, pros, cons, status) remain on the candidate row.
+- **D-11:** Candidates without `globalItemId` work as before (fully manual data).
+
+### Thread Resolution
+- **D-12:** When resolving a thread where the winning candidate has `globalItemId`, create a reference item: set `items.globalItemId` = candidate's `globalItemId`, copy only personal fields (categoryId, notes, imageFilename). Don't copy name/weight/price — those come from global item.
+- **D-13:** When resolving a candidate WITHOUT `globalItemId`, behavior stays the same as today — full data copy.
+
+### Tag System
+- **D-14:** New `tags` table: `id` (serial), `name` (text, unique, not null), `createdAt` (timestamp).
+- **D-15:** New `globalItemTags` join table: `globalItemId` (FK), `tagId` (FK), composite primary key. Many-to-many.
+- **D-16:** Tags are flat — no type column (gear-type, activity, property, etc.) for now. Keep it simple. Type categorization can be added later.
+- **D-17:** Seed initial tag set via script covering common bikepacking/outdoor gear categories: handlebar-bag, framebag, saddlebag, tent, bivy, tarp, sleeping-bag, sleeping-pad, stove, cookware, headlamp, waterproof, ultralight, budget, premium, etc.
+- **D-18:** Global item search extends to support tag filtering: `GET /api/global-items?q=...&tags=handlebar-bag,waterproof` returns items matching ALL specified tags.
+
+### Migration
+- **D-19:** Migration script: for each row in `itemGlobalLinks`, set `items.globalItemId = itemGlobalLinks.globalItemId`, then drop `itemGlobalLinks` table.
+- **D-20:** Existing items that had links keep their current name/weight/price data populated (not nulled out) — the service layer prefers global data for reference items, but having the old data as fallback is safe during transition.
+
+### Claude's Discretion
+- Exact seed tag list content and count
+- SQL migration ordering (add columns, migrate data, drop old table)
+- Whether to update MCP tools in this phase or defer
+- Test helper updates for new schema
+- Whether global item search uses AND or OR for multiple tags (recommendation: AND — intersection filtering)
+
+</decisions>
+
+<canonical_refs>
+## Canonical References
+
+**Downstream agents MUST read these before planning or implementing.**
+
+### Design Spec
+- `docs/superpowers/specs/2026-04-05-catalog-driven-gear-flow-design.md` — Full catalog-driven gear flow vision. Phase 19 implements the data model foundation described here.
+
+### Schema
+- `src/db/schema.ts` — Current schema. Add globalItemId to items and threadCandidates, add tags + globalItemTags tables, remove itemGlobalLinks.
+
+### Services (must be updated for merged data)
+- `src/server/services/item.service.ts` — Item CRUD — must join globalItems for reference items
+- `src/server/services/global-item.service.ts` — Global item search — add tag filtering, remove linkItemToGlobal/unlinkItemFromGlobal (replaced by direct FK)
+- `src/server/services/thread.service.ts` — resolveThread() at line 293 — must create reference items when candidate has globalItemId
+
+### Routes
+- `src/server/routes/items.ts` — Item routes — link/unlink endpoints removed (replaced by globalItemId on item)
+- `src/server/routes/global-items.ts` — Add tag filtering to search
+
+### Client (linking UI removed)
+- `src/client/components/LinkToGlobalItem.tsx` — Remove or repurpose (direct linking replaced by add-from-catalog flow in Phase 21)
+
+### Tests
+- `tests/services/global-item.service.test.ts` — Update for removed link/unlink, add tag tests
+- `tests/services/thread.service.test.ts` — Update resolve tests for reference item creation
+- `tests/helpers/db.ts` — Update for new schema (tags, globalItemTags, items.globalItemId)
+
+### Requirements
+- `.planning/REQUIREMENTS.md` — CATFLOW-03, CATFLOW-04, CATFLOW-05, CATFLOW-06, TAG-01, TAG-02
+
+</canonical_refs>
+
+<code_context>
+## Existing Code Insights
+
+### Reusable Assets
+- `globalItems` table already exists with brand, model, category, weight, price, image, description
+- `global-item.service.ts` has searchGlobalItems() with ILIKE — extend with tag filtering
+- `thread.service.ts` resolveThread() — modify step 4 (item creation) for reference items
+- `seed-global-items.ts` — extend seed script to also seed tags and assign them
+
+### Established Patterns
+- Service DI pattern: `(db: Db, userId: number, ...)` — consistent across all services
+- Drizzle ORM with pg-core — use same patterns for new tables
+- Zod schemas in `src/shared/schemas.ts` — update for new fields
+- Types inferred from Zod + Drizzle in `src/shared/types.ts`
+
+### Integration Points
+- `src/db/schema.ts` — Add tables, add columns, remove itemGlobalLinks
+- `src/server/index.ts` — No new route groups needed (existing global-items routes extended)
+- `tests/helpers/db.ts` — Must include new tables in test migrations
+- `src/db/seed-global-items.ts` — Extend to seed tags
+
+</code_context>
+
+<specifics>
+## Specific Ideas
+
+- The reference model is the foundation for future crowd-sourced data: purchase prices (what users actually paid), real-world weights (vs manufacturer claims), and geographic price intelligence. The `purchasePriceCents` field is the first step.
+- Catalog submission system (manual item → submit → admin review → convert to reference) is deferred but the data model should make this possible later.
+- Weight override on personal items is deferred — not critical for now.
+
+</specifics>
+
+<deferred>
+## Deferred Ideas
+
+- Catalog submission system — manual items submitted for admin review, approved items convert to references (saved in memory)
+- Crowd-sourced purchase price intelligence — aggregate what users paid, show market prices vs MSRP (saved in memory)
+- Crowd-sourced weight intelligence — user-submitted actual weights vs manufacturer claims (saved in memory)
+- Admin tag management UI — manage tags via settings, not just seed script
+- Tag type categorization — gear-type, activity, property, mounting as tag types
+- Personal weight override field on items
+
+</deferred>
+
+---
+
+*Phase: 19-reference-item-model-tags-schema*
+*Context gathered: 2026-04-05*
diff --git a/.planning/phases/19-reference-item-model-tags-schema/19-DISCUSSION-LOG.md b/.planning/phases/19-reference-item-model-tags-schema/19-DISCUSSION-LOG.md
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+# Phase 19: Reference Item Model & Tags Schema - Discussion Log
+
+> **Audit trail only.** Do not use as input to planning, research, or execution agents.
+> Decisions are captured in CONTEXT.md — this log preserves the alternatives considered.
+
+**Date:** 2026-04-05
+**Phase:** 19-reference-item-model-tags-schema
+**Areas discussed:** Reference item structure, Merged data strategy, Tag data model, Migration path
+**Mode:** Auto (--auto flag) — all areas selected, recommended defaults chosen
+
+---
+
+## Reference Item Structure
+
+| Option | Description | Selected |
+|--------|-------------|----------|
+| Add globalItemId to items, remove itemGlobalLinks | Direct FK on items table, drop junction table | ✓ |
+| Keep itemGlobalLinks alongside globalItemId | Both mechanisms coexist | |
+| Keep only itemGlobalLinks | No schema change to items | |
+
+**User's choice:** Add globalItemId to items, remove itemGlobalLinks
+**Notes:** [auto] 1:1 relationship doesn't need a junction table. Direct FK is simpler. Migration moves existing link data first.
+
+---
+
+## Merged Data Strategy
+
+| Option | Description | Selected |
+|--------|-------------|----------|
+| Same Item shape — services merge transparently | Client sees one type, services handle joins | ✓ |
+| Separate ReferenceItem type | Different response shape for reference items | |
+| Client-side merge | API returns raw, client resolves | |
+
+**User's choice:** Same Item shape — services merge transparently
+**Notes:** [auto] No client-side changes needed for existing views. Service layer joins global data when globalItemId is set.
+
+---
+
+## Tag Data Model
+
+| Option | Description | Selected |
+|--------|-------------|----------|
+| Separate tables, flat | tags + global_item_tags tables, no type column | ✓ |
+| Separate tables, typed | tags + global_item_tags, tags have type column | |
+| JSON column on globalItems | tags as JSON array, no separate tables | |
+
+**User's choice:** Separate tables, flat
+**Notes:** [auto] Proper querying, many-to-many, type categorization can be added later.
+
+---
+
+## Migration Path
+
+| Option | Description | Selected |
+|--------|-------------|----------|
+| Migrate links, keep old data as fallback | Set globalItemId from links, don't null out item fields | ✓ |
+| Migrate links, null out duplicated fields | Clean break, reference items have no local data | |
+| No migration, only new items use references | Existing items stay as copies forever | |
+
+**User's choice:** Migrate links, keep old data as fallback
+**Notes:** [auto] Safe transition — old data remains as fallback while service layer prefers global data.
+
+---
+
+## Claude's Discretion
+
+- Seed tag list content
+- SQL migration ordering
+- MCP tool updates timing
+- Tag filtering logic (AND vs OR)
+
+## Deferred Ideas
+
+- Catalog submission system (admin review workflow)
+- Price intelligence aggregation
+- Weight intelligence aggregation
+- Admin tag management UI
+- Tag type categorization
+- Personal weight override