diff --git a/src/features/posts/bird-client.server.ts b/src/features/posts/bird-client.server.ts
new file mode 100644
index 0000000..92dc594
--- /dev/null
+++ b/src/features/posts/bird-client.server.ts
@@ -0,0 +1,13 @@
+import { TwitterClient } from '@yuta/bird'
+import type { BirdReader } from './post-service'
+
+let client: TwitterClient | undefined
+
+export function getBirdReader(): BirdReader {
+  client ??= new TwitterClient({
+    relayBaseUrl: process.env.TWITTER_RELAY_BASE_URL,
+    profileName: process.env.BIRD_PROFILE_NAME,
+    timeoutMs: 20_000,
+  })
+  return client
+}
diff --git a/src/features/posts/post-service.test.ts b/src/features/posts/post-service.test.ts
new file mode 100644
index 0000000..2ac84a8
--- /dev/null
+++ b/src/features/posts/post-service.test.ts
@@ -0,0 +1,121 @@
+import { describe, expect, it, vi } from 'vitest'
+import { type BirdReader, loadUserPage, searchPage } from './post-service'
+
+const reader = (): BirdReader => ({
+  getUserIdByUsername: vi
+    .fn()
+    .mockResolvedValue({ success: true, userId: '42' }),
+  getUserTweetsPaged: vi.fn().mockResolvedValue({
+    success: true,
+    tweets: [
+      { id: '1', text: 'hello', author: { username: 'yuta', name: 'Yuta' } },
+    ],
+    nextCursor: 'user-next',
+  }),
+  getAllSearchResults: vi.fn().mockResolvedValue({
+    success: true,
+    tweets: [],
+    nextCursor: 'search-next',
+  }),
+})
+
+describe('loadUserPage', () => {
+  it('resolves a handle and fetches exactly one page', async () => {
+    const client = reader()
+    const result = await loadUserPage(client, {
+      target: 'https://x.com/yuta',
+      cursor: 'cursor-1',
+    })
+
+    expect(client.getUserIdByUsername).toHaveBeenCalledWith('yuta')
+    expect(client.getUserTweetsPaged).toHaveBeenCalledWith('42', 20, {
+      cursor: 'cursor-1',
+      maxPages: 1,
+      pageDelayMs: 0,
+    })
+    expect(result).toMatchObject({
+      ok: true,
+      page: { nextCursor: 'user-next' },
+    })
+  })
+
+  it('returns a safe not-found error', async () => {
+    const client = reader()
+    vi.mocked(client.getUserIdByUsername).mockResolvedValue({
+      success: false,
+      error: 'User not found: private relay detail',
+    })
+
+    expect(await loadUserPage(client, { target: 'missing' })).toEqual({
+      ok: false,
+      error: {
+        code: 'user-not-found',
+        message: 'ユーザーが見つかりませんでした。',
+        retryable: false,
+      },
+    })
+  })
+})
+
+describe('searchPage', () => {
+  it('forwards Top and appends follows once', async () => {
+    const client = reader()
+    await searchPage(client, {
+      query: 'AI lang:ja',
+      product: 'Top',
+      following: true,
+      cursor: 'cursor-2',
+    })
+
+    expect(client.getAllSearchResults).toHaveBeenCalledWith(
+      'AI lang:ja filter:follows',
+      { product: 'Top', cursor: 'cursor-2', maxPages: 1 },
+    )
+  })
+
+  it('removes raw response data from posts and quoted posts', async () => {
+    const client = reader()
+    vi.mocked(client.getAllSearchResults).mockResolvedValue({
+      success: true,
+      tweets: [
+        {
+          id: '1',
+          text: 'hello',
+          author: { username: 'yuta', name: 'Yuta' },
+          quotedTweet: {
+            id: '2',
+            text: 'quoted',
+            author: { username: 'bird', name: 'Bird' },
+            _raw: { rest_id: 'private-quoted-detail' },
+          },
+          _raw: { rest_id: 'private-detail' },
+        },
+      ],
+    })
+
+    const result = await searchPage(client, {
+      query: 'AI',
+      product: 'Latest',
+      following: false,
+    })
+
+    expect(result).toEqual({
+      ok: true,
+      page: {
+        nextCursor: undefined,
+        tweets: [
+          {
+            id: '1',
+            text: 'hello',
+            author: { username: 'yuta', name: 'Yuta' },
+            quotedTweet: {
+              id: '2',
+              text: 'quoted',
+              author: { username: 'bird', name: 'Bird' },
+            },
+          },
+        ],
+      },
+    })
+  })
+})
diff --git a/src/features/posts/post-service.ts b/src/features/posts/post-service.ts
new file mode 100644
index 0000000..51f170f
--- /dev/null
+++ b/src/features/posts/post-service.ts
@@ -0,0 +1,135 @@
+import type { SearchProduct, SearchResult, TweetData } from '@yuta/bird'
+import { buildSearchQuery, InputError, normalizeUserTarget } from './inputs'
+import type {
+  LoadError,
+  LoadResult,
+  Post,
+  SearchPageInput,
+  UserPageInput,
+} from './types'
+
+type UserLookupResult = {
+  success: boolean
+  userId?: string
+  error?: string
+}
+
+export interface BirdReader {
+  getUserIdByUsername(username: string): Promise<UserLookupResult>
+  getUserTweetsPaged(
+    userId: string,
+    limit: number,
+    options: {
+      cursor?: string
+      maxPages: number
+      pageDelayMs: number
+    },
+  ): Promise<SearchResult>
+  getAllSearchResults(
+    query: string,
+    options: {
+      product: SearchProduct
+      cursor?: string
+      maxPages: number
+    },
+  ): Promise<SearchResult>
+}
+
+const failure = (
+  code: LoadError['code'],
+  message: string,
+  retryable: boolean,
+): LoadResult => ({ ok: false, error: { code, message, retryable } })
+
+function upstreamFailure(message = ''): LoadResult {
+  const lower = message.toLowerCase()
+  if (lower.includes('timeout') || lower.includes('aborted')) {
+    return failure('timeout', '取得がタイムアウトしました。', true)
+  }
+  if (lower.includes('not found')) {
+    return failure('user-not-found', 'ユーザーが見つかりませんでした。', false)
+  }
+  if (lower.includes('suspended') || lower.includes('protected')) {
+    return failure(
+      'user-unavailable',
+      'このユーザーの投稿は取得できません。',
+      false,
+    )
+  }
+  return failure('upstream', 'X から投稿を取得できませんでした。', true)
+}
+
+function publicPost(tweet: TweetData): Post {
+  const post = { ...tweet }
+  delete post._raw
+  if (post.quotedTweet) {
+    post.quotedTweet = publicPost(post.quotedTweet)
+  }
+  return post
+}
+
+function resultPage(result: SearchResult): LoadResult {
+  return result.success
+    ? {
+        ok: true,
+        page: {
+          tweets: result.tweets.map(publicPost),
+          nextCursor: result.nextCursor,
+        },
+      }
+    : upstreamFailure(result.error)
+}
+
+export async function loadUserPage(
+  reader: BirdReader,
+  input: UserPageInput,
+): Promise<LoadResult> {
+  try {
+    const handle = normalizeUserTarget(input.target)
+    const user = await reader.getUserIdByUsername(handle)
+    if (!user.success || !user.userId) {
+      return upstreamFailure(user.error)
+    }
+    return resultPage(
+      await reader.getUserTweetsPaged(user.userId, 20, {
+        cursor: input.cursor,
+        maxPages: 1,
+        pageDelayMs: 0,
+      }),
+    )
+  } catch (error) {
+    if (error instanceof Error && error.name === 'AbortError') {
+      return failure('timeout', '取得がタイムアウトしました。', true)
+    }
+    if (error instanceof InputError) {
+      return failure('invalid-input', error.message, false)
+    }
+    return upstreamFailure(error instanceof Error ? error.message : '')
+  }
+}
+
+export async function searchPage(
+  reader: BirdReader,
+  input: SearchPageInput,
+): Promise<LoadResult> {
+  try {
+    return resultPage(
+      await reader.getAllSearchResults(
+        buildSearchQuery(input.query, input.following),
+        {
+          product: input.product,
+          cursor: input.cursor,
+          maxPages: 1,
+        },
+      ),
+    )
+  } catch (error) {
+    if (error instanceof Error && error.name === 'AbortError') {
+      return failure('timeout', '取得がタイムアウトしました。', true)
+    }
+    if (error instanceof InputError) {
+      return failure('invalid-input', error.message, false)
+    }
+    return upstreamFailure(error instanceof Error ? error.message : '')
+  }
+}
diff --git a/src/features/posts/server-functions.ts b/src/features/posts/server-functions.ts
new file mode 100644
index 0000000..85095c8
--- /dev/null
+++ b/src/features/posts/server-functions.ts
@@ -0,0 +1,38 @@
+import { createServerFn } from '@tanstack/react-start'
+import { searchPageInputSchema, userPageInputSchema } from './inputs'
+import { loadUserPage, searchPage } from './post-service'
+import type { LoadResult } from './types'
+
+const configFailure = (): LoadResult => ({
+  ok: false,
+  error: {
+    code: 'relay-config',
+    message: 'TWITTER_RELAY_BASE_URL を設定してください。',
+    retryable: false,
+  },
+})
+
+async function reader() {
+  const { getBirdReader } = await import('./bird-client.server')
+  return getBirdReader()
+}
+
+export const loadUserPosts = createServerFn({ method: 'GET' })
+  .validator(userPageInputSchema)
+  .handler(async ({ data }) => {
+    try {
+      return await loadUserPage(await reader(), data)
+    } catch {
+      return configFailure()
+    }
+  })
+
+export const searchPosts = createServerFn({ method: 'GET' })
+  .validator(searchPageInputSchema)
+  .handler(async ({ data }) => {
+    try {
+      return await searchPage(await reader(), data)
+    } catch {
+      return configFailure()
+    }
+  })
diff --git a/src/features/posts/types.ts b/src/features/posts/types.ts
index e62f004..ae16c56 100644
--- a/src/features/posts/types.ts
+++ b/src/features/posts/types.ts
@@ -1,6 +1,8 @@
 import type { SearchProduct, TweetData } from '@yuta/bird'
 
-export type Post = TweetData
+export type Post = Omit<TweetData, '_raw' | 'quotedTweet'> & {
+  quotedTweet?: Post
+}
 
 export type PostPage = {
   tweets: Post[]