diff --git a/src/server/services/thread.service.ts b/src/server/services/thread.service.ts
new file mode 100644
index 0000000..6362480
--- /dev/null
+++ b/src/server/services/thread.service.ts
@@ -0,0 +1,217 @@
+import { eq, desc, sql } from "drizzle-orm";
+import { threads, threadCandidates, items, categories } from "../../db/schema.ts";
+import { db as prodDb } from "../../db/index.ts";
+import type { CreateThread, UpdateThread, CreateCandidate } from "../../shared/types.ts";
+
+type Db = typeof prodDb;
+
+export function createThread(db: Db = prodDb, data: CreateThread) {
+  return db
+    .insert(threads)
+    .values({ name: data.name })
+    .returning()
+    .get();
+}
+
+export function getAllThreads(db: Db = prodDb, includeResolved = false) {
+  const query = db
+    .select({
+      id: threads.id,
+      name: threads.name,
+      status: threads.status,
+      resolvedCandidateId: threads.resolvedCandidateId,
+      createdAt: threads.createdAt,
+      updatedAt: threads.updatedAt,
+      candidateCount: sql<number>`(
+        SELECT COUNT(*) FROM thread_candidates
+        WHERE thread_candidates.thread_id = threads.id
+      )`.as("candidate_count"),
+      minPriceCents: sql<number | null>`(
+        SELECT MIN(price_cents) FROM thread_candidates
+        WHERE thread_candidates.thread_id = threads.id
+      )`.as("min_price_cents"),
+      maxPriceCents: sql<number | null>`(
+        SELECT MAX(price_cents) FROM thread_candidates
+        WHERE thread_candidates.thread_id = threads.id
+      )`.as("max_price_cents"),
+    })
+    .from(threads)
+    .orderBy(desc(threads.createdAt));
+
+  if (!includeResolved) {
+    return query.where(eq(threads.status, "active")).all();
+  }
+  return query.all();
+}
+
+export function getThreadWithCandidates(db: Db = prodDb, threadId: number) {
+  const thread = db.select().from(threads)
+    .where(eq(threads.id, threadId)).get();
+  if (!thread) return null;
+
+  const candidateList = db
+    .select({
+      id: threadCandidates.id,
+      threadId: threadCandidates.threadId,
+      name: threadCandidates.name,
+      weightGrams: threadCandidates.weightGrams,
+      priceCents: threadCandidates.priceCents,
+      categoryId: threadCandidates.categoryId,
+      notes: threadCandidates.notes,
+      productUrl: threadCandidates.productUrl,
+      imageFilename: threadCandidates.imageFilename,
+      createdAt: threadCandidates.createdAt,
+      updatedAt: threadCandidates.updatedAt,
+      categoryName: categories.name,
+      categoryEmoji: categories.emoji,
+    })
+    .from(threadCandidates)
+    .innerJoin(categories, eq(threadCandidates.categoryId, categories.id))
+    .where(eq(threadCandidates.threadId, threadId))
+    .all();
+
+  return { ...thread, candidates: candidateList };
+}
+
+export function updateThread(db: Db = prodDb, threadId: number, data: Partial<{ name: string }>) {
+  const existing = db.select({ id: threads.id }).from(threads)
+    .where(eq(threads.id, threadId)).get();
+  if (!existing) return null;
+
+  return db
+    .update(threads)
+    .set({ ...data, updatedAt: new Date() })
+    .where(eq(threads.id, threadId))
+    .returning()
+    .get();
+}
+
+export function deleteThread(db: Db = prodDb, threadId: number) {
+  const thread = db.select().from(threads)
+    .where(eq(threads.id, threadId)).get();
+  if (!thread) return null;
+
+  // Collect candidate image filenames for cleanup
+  const candidatesWithImages = db
+    .select({ imageFilename: threadCandidates.imageFilename })
+    .from(threadCandidates)
+    .where(eq(threadCandidates.threadId, threadId))
+    .all()
+    .filter((c) => c.imageFilename != null);
+
+  db.delete(threads).where(eq(threads.id, threadId)).run();
+
+  return { ...thread, candidateImages: candidatesWithImages.map((c) => c.imageFilename!) };
+}
+
+export function createCandidate(
+  db: Db = prodDb,
+  threadId: number,
+  data: Partial<CreateCandidate> & { name: string; categoryId: number; imageFilename?: string },
+) {
+  return db
+    .insert(threadCandidates)
+    .values({
+      threadId,
+      name: data.name,
+      weightGrams: data.weightGrams ?? null,
+      priceCents: data.priceCents ?? null,
+      categoryId: data.categoryId,
+      notes: data.notes ?? null,
+      productUrl: data.productUrl ?? null,
+      imageFilename: data.imageFilename ?? null,
+    })
+    .returning()
+    .get();
+}
+
+export function updateCandidate(
+  db: Db = prodDb,
+  candidateId: number,
+  data: Partial<{
+    name: string;
+    weightGrams: number;
+    priceCents: number;
+    categoryId: number;
+    notes: string;
+    productUrl: string;
+    imageFilename: string;
+  }>,
+) {
+  const existing = db.select({ id: threadCandidates.id }).from(threadCandidates)
+    .where(eq(threadCandidates.id, candidateId)).get();
+  if (!existing) return null;
+
+  return db
+    .update(threadCandidates)
+    .set({ ...data, updatedAt: new Date() })
+    .where(eq(threadCandidates.id, candidateId))
+    .returning()
+    .get();
+}
+
+export function deleteCandidate(db: Db = prodDb, candidateId: number) {
+  const candidate = db.select().from(threadCandidates)
+    .where(eq(threadCandidates.id, candidateId)).get();
+  if (!candidate) return null;
+
+  db.delete(threadCandidates).where(eq(threadCandidates.id, candidateId)).run();
+  return candidate;
+}
+
+export function resolveThread(
+  db: Db = prodDb,
+  threadId: number,
+  candidateId: number,
+): { success: boolean; item?: any; error?: string } {
+  return db.transaction((tx) => {
+    // 1. Check thread is active
+    const thread = tx.select().from(threads)
+      .where(eq(threads.id, threadId)).get();
+    if (!thread || thread.status !== "active") {
+      return { success: false, error: "Thread not active" };
+    }
+
+    // 2. Get the candidate data
+    const candidate = tx.select().from(threadCandidates)
+      .where(eq(threadCandidates.id, candidateId)).get();
+    if (!candidate) {
+      return { success: false, error: "Candidate not found" };
+    }
+    if (candidate.threadId !== threadId) {
+      return { success: false, error: "Candidate not in thread" };
+    }
+
+    // 3. Verify categoryId still exists, fallback to Uncategorized (id=1)
+    const category = tx.select({ id: categories.id }).from(categories)
+      .where(eq(categories.id, candidate.categoryId)).get();
+    const safeCategoryId = category ? candidate.categoryId : 1;
+
+    // 4. Create collection item from candidate data
+    const newItem = tx
+      .insert(items)
+      .values({
+        name: candidate.name,
+        weightGrams: candidate.weightGrams,
+        priceCents: candidate.priceCents,
+        categoryId: safeCategoryId,
+        notes: candidate.notes,
+        productUrl: candidate.productUrl,
+        imageFilename: candidate.imageFilename,
+      })
+      .returning()
+      .get();
+
+    // 5. Archive the thread
+    tx.update(threads)
+      .set({
+        status: "resolved",
+        resolvedCandidateId: candidateId,
+        updatedAt: new Date(),
+      })
+      .where(eq(threads.id, threadId))
+      .run();
+
+    return { success: true, item: newItem };
+  });
+}