diff --git a/bun.lock b/bun.lock
new file mode 100644
index 0000000..d21d3ac
--- /dev/null
+++ b/bun.lock
@@ -0,0 +1,35 @@
+{
+  "lockfileVersion": 1,
+  "configVersion": 1,
+  "workspaces": {
+    "": {
+      "name": "oj2",
+      "devDependencies": {
+        "@types/bun": "latest",
+        "typescript": "^5.7.0",
+      },
+    },
+    "packages/contract": {
+      "name": "@oj2/contract",
+      "version": "0.0.0",
+      "dependencies": {
+        "zod": "^4.0.0",
+      },
+    },
+  },
+  "packages": {
+    "@oj2/contract": ["@oj2/contract@workspace:packages/contract"],
+
+    "@types/bun": ["@types/bun@1.3.14", "", { "dependencies": { "bun-types": "1.3.14" } }, "sha512-h1hFqFVcvAvD9j9K7ZW7vd82aSA+rTdznZa+5bwvCwqSB1jmmfLcbIWhOLx1/+boy/xmjgCs/OMUL8hRJSmnPw=="],
+
+    "@types/node": ["@types/node@26.1.2", "", { "dependencies": { "undici-types": "~8.3.0" } }, "sha512-Vu4a5UFA9rIIFJ7rB/Vaafh9lrCQszopTCx6KjFboXTGQbPNasehVR5TEiithSDGyd1DEiUByggTZsg8jukeIg=="],
+
+    "bun-types": ["bun-types@1.3.14", "", { "dependencies": { "@types/node": "*" } }, "sha512-4N0ig0fEomHt5R0KCFWjovxow98rIoRwKolrYdCcknNwMekCXRnWEUvgu5soYV8QXtVsrUD8B95MBOZGPvr6KQ=="],
+
+    "typescript": ["typescript@5.9.3", "", { "bin": { "tsc": "bin/tsc", "tsserver": "bin/tsserver" } }, "sha512-jl1vZzPDinLr9eUt3J/t7V6FgNEw9QjvBPdysz9KfQDD41fQrC2Y4vKQdiaUpFT4bXlb1RHhLpp8wtm6M5TgSw=="],
+
+    "undici-types": ["undici-types@8.3.0", "", {}, "sha512-j375ScV60dom+YkPFIfTLcOiPxkN/buHz5GobjLhixFuANaNs3C9l4GmrWqejgXWJ7BbJcFYpTEUkS1Ge8bpZQ=="],
+
+    "zod": ["zod@4.4.3", "", {}, "sha512-ytENFjIJFl2UwYglde2jchW2Hwm4GJFLDiSXWdTrJQBIN9Fcyp7n4DhxJEiWNAJMV1/BqWfW/kkg71UDcHJyTQ=="],
+  }
+}
diff --git a/bunfig.toml b/bunfig.toml
new file mode 100644
index 0000000..a2f3173
--- /dev/null
+++ b/bunfig.toml
@@ -0,0 +1,3 @@
+[install]
+# workspace 内部依赖走本地链接，不去 registry 找
+linker = "hoisted"
diff --git a/package.json b/package.json
new file mode 100644
index 0000000..7c265a2
--- /dev/null
+++ b/package.json
@@ -0,0 +1,17 @@
+{
+  "name": "oj2",
+  "private": true,
+  "type": "module",
+  "workspaces": ["apps/*", "packages/*"],
+  "scripts": {
+    "dev": "bun run --filter '*' dev",
+    "dev:api": "bun run --filter '@oj2/api' dev",
+    "dev:web": "bun run --filter '@oj2/web' dev",
+    "db:up": "docker compose -f docker/compose.dev.yml up -d",
+    "db:down": "docker compose -f docker/compose.dev.yml down"
+  },
+  "devDependencies": {
+    "typescript": "^5.7.0",
+    "@types/bun": "latest"
+  }
+}
diff --git a/packages/contract/package.json b/packages/contract/package.json
new file mode 100644
index 0000000..a28dc39
--- /dev/null
+++ b/packages/contract/package.json
@@ -0,0 +1,12 @@
+{
+  "name": "@oj2/contract",
+  "version": "0.0.0",
+  "private": true,
+  "type": "module",
+  "main": "./src/index.ts",
+  "types": "./src/index.ts",
+  "exports": { ".": "./src/index.ts" },
+  "dependencies": {
+    "zod": "^4.0.0"
+  }
+}
diff --git a/packages/contract/src/index.ts b/packages/contract/src/index.ts
new file mode 100644
index 0000000..ddfe08e
--- /dev/null
+++ b/packages/contract/src/index.ts
@@ -0,0 +1 @@
+export * from "./problem"
diff --git a/packages/contract/src/problem.ts b/packages/contract/src/problem.ts
new file mode 100644
index 0000000..91ccdc7
--- /dev/null
+++ b/packages/contract/src/problem.ts
@@ -0,0 +1,13 @@
+import { z } from "zod"
+
+/** 题目列表项。字段取自 problem 表，只含列表页需要的列。 */
+export const problemSummarySchema = z.object({
+  id: z.number().int(),
+  _id: z.string(), // 展示用编号，与自增 id 不同
+  title: z.string(),
+  difficulty: z.string(),
+  submissionNumber: z.number().int(),
+  acceptedNumber: z.number().int(),
+})
+
+export type ProblemSummary = z.infer<typeof problemSummarySchema>
diff --git a/packages/contract/tsconfig.json b/packages/contract/tsconfig.json
new file mode 100644
index 0000000..564a599
--- /dev/null
+++ b/packages/contract/tsconfig.json
@@ -0,0 +1,4 @@
+{
+  "extends": "../../tsconfig.base.json",
+  "include": ["src"]
+}
diff --git a/tsconfig.base.json b/tsconfig.base.json
new file mode 100644
index 0000000..49b1488
--- /dev/null
+++ b/tsconfig.base.json
@@ -0,0 +1,14 @@
+{
+  "compilerOptions": {
+    "target": "ESNext",
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "lib": ["ESNext", "DOM"],
+    "strict": true,
+    "noUncheckedIndexedAccess": true,
+    "skipLibCheck": true,
+    "esModuleInterop": true,
+    "resolveJsonModule": true,
+    "types": ["bun"]
+  }
+}