diff --git a/packages/db/migrations/0031_buffer_rules.sql b/packages/db/migrations/0031_buffer_rules.sql
new file mode 100644
index 0000000..5bfd90a
--- /dev/null
+++ b/packages/db/migrations/0031_buffer_rules.sql
@@ -0,0 +1,31 @@
+-- Migration: 0031_buffer_rules.sql
+-- Buffer rules CRUD: pet size/coat enums, bufferRules table, services.defaultBufferMinutes
+
+-- ─── Enums ───────────────────────────────────────────────────────────────────
+
+CREATE TYPE "pet_size_category" AS ENUM ('small', 'medium', 'large', 'xlarge');
+CREATE TYPE "coat_type" AS ENUM ('smooth', 'double', 'wire', 'curly', 'long', 'hairless');
+
+-- ─── Alter pets columns to use new enums ─────────────────────────────────────
+
+ALTER TABLE "pets" ALTER COLUMN "coat_type" TYPE "coat_type" USING "coat_type"::text::"coat_type";
+ALTER TABLE "pets" ALTER COLUMN "pet_size_category" TYPE "pet_size_category" USING "pet_size_category"::text::"pet_size_category";
+
+-- ─── Services: add defaultBufferMinutes ───────────────────────────────────────
+
+ALTER TABLE "services" ADD COLUMN "default_buffer_minutes" integer;
+
+-- ─── Buffer Rules table ───────────────────────────────────────────────────────
+
+CREATE TABLE "buffer_rules" (
+  "id" uuid PRIMARY KEY DEFAULT gen_random_uuid(),
+  "service_id" uuid NOT NULL REFERENCES "services"("id") ON DELETE CASCADE,
+  "size_category" "pet_size_category",
+  "coat_type" "coat_type",
+  "buffer_minutes" integer NOT NULL,
+  "created_at" timestamp NOT NULL DEFAULT now(),
+  "updated_at" timestamp NOT NULL DEFAULT now(),
+  CONSTRAINT "uq_buffer_rules_service_size_coat" UNIQUE ("service_id", "size_category", "coat_type")
+);
+
+CREATE INDEX "idx_buffer_rules_service_id" ON "buffer_rules"("service_id");
\ No newline at end of file
diff --git a/packages/db/src/factories.ts b/packages/db/src/factories.ts
index 00de0c4..cac71f7 100644
--- a/packages/db/src/factories.ts
+++ b/packages/db/src/factories.ts
@@ -121,6 +121,7 @@ export function buildService(overrides: Partial<ServiceRow> = {}): ServiceRow {
     description: "A grooming service",
     basePriceCents: 6500,
     durationMinutes: 60,
+    defaultBufferMinutes: null,
     active: true,
     createdAt: new Date("2025-01-01T00:00:00Z"),
     updatedAt: new Date("2025-01-01T00:00:00Z"),
diff --git a/packages/db/src/schema.ts b/packages/db/src/schema.ts
index 7d93afc..7ab60eb 100644
--- a/packages/db/src/schema.ts
+++ b/packages/db/src/schema.ts
@@ -48,6 +48,22 @@ export const clientStatusEnum = pgEnum("client_status", [
   "disabled",
 ]);
 
+export const petSizeCategoryEnum = pgEnum("pet_size_category", [
+  "small",
+  "medium",
+  "large",
+  "xlarge",
+]);
+
+export const coatTypeEnum = pgEnum("coat_type", [
+  "smooth",
+  "double",
+  "wire",
+  "curly",
+  "long",
+  "hairless",
+]);
+
 // ─── Better-Auth Tables ──────────────────────────────────────────────────────
 
 export const user = pgTable("user", {
@@ -142,8 +158,8 @@ export const pets = pgTable(
     cutStyle: text("cut_style"),
     shampooPreference: text("shampoo_preference"),
     specialCareNotes: text("special_care_notes"),
-    coatType: text("coat_type"),
-    petSizeCategory: text("pet_size_category"),
+    coatType: coatTypeEnum("coat_type"),
+    petSizeCategory: petSizeCategoryEnum("pet_size_category"),
     customFields: jsonb("custom_fields").$type<Record<string, string>>().notNull().default({}),
     photoKey: text("photo_key"),
     photoUploadedAt: timestamp("photo_uploaded_at"),
@@ -160,11 +176,34 @@ export const services = pgTable("services", {
   description: text("description"),
   basePriceCents: integer("base_price_cents").notNull(),
   durationMinutes: integer("duration_minutes").notNull(),
+  defaultBufferMinutes: integer("default_buffer_minutes"),
   active: boolean("active").notNull().default(true),
   createdAt: timestamp("created_at").notNull().defaultNow(),
   updatedAt: timestamp("updated_at").notNull().defaultNow(),
 });
 
+export const bufferRules = pgTable(
+  "buffer_rules",
+  {
+    id: uuid("id").primaryKey().defaultRandom(),
+    serviceId: uuid("service_id")
+      .notNull()
+      .references(() => services.id, { onDelete: "cascade" }),
+    sizeCategory: petSizeCategoryEnum("size_category"),
+    coatType: coatTypeEnum("coat_type"),
+    bufferMinutes: integer("buffer_minutes").notNull(),
+    createdAt: timestamp("created_at").notNull().defaultNow(),
+    updatedAt: timestamp("updated_at").notNull().defaultNow(),
+  },
+  (t) => [
+    unique("uq_buffer_rules_service_size_coat").on(
+      t.serviceId,
+      t.sizeCategory,
+      t.coatType
+    ),
+  ]
+);
+
 export const staff = pgTable("staff", {
   id: uuid("id").primaryKey().defaultRandom(),
   name: text("name").notNull(),
diff --git a/src/index.ts b/src/index.ts
index 1ed08f2..6acee60 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -19,6 +19,7 @@ import { impersonationRouter } from "./routes/impersonation.js";
 import { settingsRouter } from "./routes/settings.js";
 import { authProviderRouter } from "./routes/authProvider.js";
 import { searchRouter } from "./routes/search.js";
+import { bufferRulesRouter } from "./routes/buffer-rules.js";
 import { getObject } from "./lib/s3.js";
 import { calendarRouter } from "./routes/calendar.js";
 import { setupRouter } from "./routes/setup.js";
@@ -269,6 +270,7 @@ api.route("/admin/settings", settingsRouter);
 api.route("/admin/auth-provider", authProviderRouter);
 api.route("/admin/seed", adminSeedRouter);
 api.route("/search", searchRouter);
+api.route("/buffer-rules", bufferRulesRouter);
 
 const port = Number(process.env.PORT ?? 3000);
 await initAuth();
diff --git a/src/routes/book.ts b/src/routes/book.ts
index 5b9fd27..828c11c 100644
--- a/src/routes/book.ts
+++ b/src/routes/book.ts
@@ -193,8 +193,8 @@ bookRouter.post(
         name: body.petName,
         species: body.petSpecies,
         breed: body.petBreed ?? null,
-        coatType: body.petCoatType ?? null,
-        petSizeCategory: body.petSizeCategory ?? null,
+        coatType: (body.petCoatType ?? null) as "smooth" | "double" | "wire" | "curly" | "long" | "hairless" | null,
+        petSizeCategory: (body.petSizeCategory ?? null) as "small" | "medium" | "large" | "xlarge" | null,
       })
       .returning();
     const pet = petInserted[0];
diff --git a/src/routes/buffer-rules.ts b/src/routes/buffer-rules.ts
new file mode 100644
index 0000000..fb3ff2b
--- /dev/null
+++ b/src/routes/buffer-rules.ts
@@ -0,0 +1,128 @@
+import { Hono } from "hono";
+import { zValidator } from "@hono/zod-validator";
+import { z } from "zod/v3";
+import {
+  and,
+  eq,
+  isNull,
+  getDb,
+  bufferRules,
+  services,
+} from "@groombook/db";
+import type { AppEnv } from "../middleware/rbac.js";
+import { requireRole } from "../middleware/rbac.js";
+
+export const bufferRulesRouter = new Hono<AppEnv>();
+
+// Apply manager role guard to all routes
+bufferRulesRouter.use("*", requireRole("manager"));
+
+const createBufferRuleSchema = z.object({
+  serviceId: z.string().uuid(),
+  sizeCategory: z.enum(["small", "medium", "large", "xlarge"]).optional(),
+  coatType: z.enum(["smooth", "double", "wire", "curly", "long", "hairless"]).optional(),
+  bufferMinutes: z.number().int().positive(),
+});
+
+const updateBufferRuleSchema = z.object({
+  bufferMinutes: z.number().int().positive(),
+});
+
+bufferRulesRouter.get("/", async (c) => {
+  const db = getDb();
+  const serviceId = c.req.query("serviceId");
+
+  const conditions = [];
+  if (serviceId) conditions.push(eq(bufferRules.serviceId, serviceId));
+
+  const rows = await db
+    .select({
+      id: bufferRules.id,
+      serviceId: bufferRules.serviceId,
+      serviceName: services.name,
+      sizeCategory: bufferRules.sizeCategory,
+      coatType: bufferRules.coatType,
+      bufferMinutes: bufferRules.bufferMinutes,
+      createdAt: bufferRules.createdAt,
+      updatedAt: bufferRules.updatedAt,
+    })
+    .from(bufferRules)
+    .leftJoin(services, eq(bufferRules.serviceId, services.id))
+    .where(conditions.length > 0 ? and(...conditions) : undefined);
+
+  return c.json(rows);
+});
+
+bufferRulesRouter.post(
+  "/",
+  zValidator("json", createBufferRuleSchema),
+  async (c) => {
+    const db = getDb();
+    const body = c.req.valid("json");
+
+    // Validate serviceId exists
+    const [svc] = await db
+      .select({ id: services.id })
+      .from(services)
+      .where(eq(services.id, body.serviceId))
+      .limit(1);
+    if (!svc) return c.json({ error: "Service not found" }, 404);
+
+    // Check for duplicate — sizeCategory/coatType are nullable, use isNull for null check
+    const conditions = [eq(bufferRules.serviceId, body.serviceId)];
+    if (body.sizeCategory) {
+      conditions.push(eq(bufferRules.sizeCategory, body.sizeCategory));
+    } else {
+      conditions.push(isNull(bufferRules.sizeCategory));
+    }
+    if (body.coatType) {
+      conditions.push(eq(bufferRules.coatType, body.coatType));
+    } else {
+      conditions.push(isNull(bufferRules.coatType));
+    }
+    const [existing] = await db
+      .select({ id: bufferRules.id })
+      .from(bufferRules)
+      .where(and(...conditions))
+      .limit(1);
+    if (existing) return c.json({ error: "Duplicate rule for this service and attributes" }, 409);
+
+    const [row] = await db
+      .insert(bufferRules)
+      .values({
+        serviceId: body.serviceId,
+        sizeCategory: body.sizeCategory,
+        coatType: body.coatType,
+        bufferMinutes: body.bufferMinutes,
+      })
+      .returning();
+
+    return c.json(row, 201);
+  }
+);
+
+bufferRulesRouter.patch(
+  "/:id",
+  zValidator("json", updateBufferRuleSchema),
+  async (c) => {
+    const db = getDb();
+    const body = c.req.valid("json");
+    const [row] = await db
+      .update(bufferRules)
+      .set({ bufferMinutes: body.bufferMinutes, updatedAt: new Date() })
+      .where(eq(bufferRules.id, c.req.param("id")))
+      .returning();
+    if (!row) return c.json({ error: "Not found" }, 404);
+    return c.json(row);
+  }
+);
+
+bufferRulesRouter.delete("/:id", async (c) => {
+  const db = getDb();
+  const [row] = await db
+    .delete(bufferRules)
+    .where(eq(bufferRules.id, c.req.param("id")))
+    .returning();
+  if (!row) return c.json({ error: "Not found" }, 404);
+  return c.json({ ok: true });
+});
\ No newline at end of file
diff --git a/src/routes/pets.ts b/src/routes/pets.ts
index 2264e6c..9642450 100644
--- a/src/routes/pets.ts
+++ b/src/routes/pets.ts
@@ -24,6 +24,8 @@ const createPetSchema = z.object({
   shampooPreference: z.string().max(500).optional(),
   specialCareNotes: z.string().max(2000).optional(),
   customFields: z.record(z.string(), z.string()).optional(),
+  sizeCategory: z.enum(["small", "medium", "large", "xlarge"]).optional(),
+  coatType: z.enum(["smooth", "double", "wire", "curly", "long", "hairless"]).optional(),
 });
 
 const updatePetSchema = createPetSchema.partial().omit({ clientId: true });
diff --git a/src/routes/services.ts b/src/routes/services.ts
index 659dee2..7cf8112 100644
--- a/src/routes/services.ts
+++ b/src/routes/services.ts
@@ -10,6 +10,7 @@ const createServiceSchema = z.object({
   description: z.string().max(2000).optional(),
   basePriceCents: z.number().int().positive(),
   durationMinutes: z.number().int().positive().max(480),
+  defaultBufferMinutes: z.number().int().min(0).optional(),
   active: z.boolean().default(true),
 });