diff --git a/.github/PULL_REQUEST_TEMPLATE.md b/.github/PULL_REQUEST_TEMPLATE.md
index cf48061..00979a6 100644
--- a/.github/PULL_REQUEST_TEMPLATE.md
+++ b/.github/PULL_REQUEST_TEMPLATE.md
@@ -20,4 +20,4 @@
 ---
 
 ## 📎 관련 이슈(선택)
-- Close #이슈번호
+- Closes #이슈번호
diff --git a/.github/scripts/close-develop-issues.js b/.github/scripts/close-develop-issues.js
new file mode 100644
index 0000000..ee8132e
--- /dev/null
+++ b/.github/scripts/close-develop-issues.js
@@ -0,0 +1,182 @@
+'use strict';
+
+const EXPECTED_OWNER = 'CKLOB';
+const EXPECTED_REPOSITORY = 'MUDDA-Server';
+const EXPECTED_FULL_NAME = `${EXPECTED_OWNER}/${EXPECTED_REPOSITORY}`;
+const MARKER_PREFIX = 'auto-close-develop-pr';
+const CLOSING_KEYWORDS =
+  'close|closes|closed|fix|fixes|fixed|resolve|resolves|resolved';
+
+function stripNonContent(body) {
+  let content = typeof body === 'string' ? body : '';
+
+  content = content.replace(/<!--[\s\S]*?-->/g, ' ');
+  content = content.replace(/```[\s\S]*?```/g, ' ');
+  content = content.replace(/~~~[\s\S]*?~~~/g, ' ');
+  content = content.replace(/^(?: {4}|\t).+$/gm, ' ');
+  content = content.replace(/`[^`\r\n]*`/g, ' ');
+  content = content.replace(/https?:\/\/[^\s<>()]+/gi, ' ');
+
+  return content;
+}
+
+function extractLinkedIssueNumbers(body) {
+  const content = stripNonContent(body);
+  const pattern = new RegExp(
+    `(?:^|[^\\p{L}\\p{N}_-])(?:${CLOSING_KEYWORDS})(?![\\p{L}\\p{N}_-])(?:\\s+|\\s*:\\s*)#([1-9]\\d*)(?!\\d)`,
+    'giu',
+  );
+  const issueNumbers = new Set();
+
+  for (const match of content.matchAll(pattern)) {
+    const issueNumber = Number(match[1]);
+    if (Number.isSafeInteger(issueNumber) && issueNumber > 0) {
+      issueNumbers.add(issueNumber);
+    }
+  }
+
+  return [...issueNumbers];
+}
+
+function isTargetPullRequest(repository, pullRequest) {
+  return (
+    repository?.full_name === EXPECTED_FULL_NAME &&
+    pullRequest?.base?.ref === 'develop' &&
+    pullRequest?.merged === true &&
+    pullRequest?.head?.repo?.full_name === EXPECTED_FULL_NAME
+  );
+}
+
+function getMarker(pullRequestNumber) {
+  return `<!-- ${MARKER_PREFIX}:${pullRequestNumber} -->`;
+}
+
+function getPullRequestUrl(pullRequestNumber) {
+  return `https://github.com/${EXPECTED_FULL_NAME}/pull/${pullRequestNumber}`;
+}
+
+function errorMessage(error) {
+  return error instanceof Error ? error.message : String(error);
+}
+
+async function closeLinkedIssues({ github, repository, pullRequest }) {
+  const result = {
+    skipped: [],
+    closed: [],
+    failures: [],
+  };
+
+  if (!isTargetPullRequest(repository, pullRequest)) {
+    result.skipped.push({ reason: 'event does not target a merged develop PR' });
+    return result;
+  }
+
+  const pullRequestNumber = pullRequest.number;
+  if (!Number.isSafeInteger(pullRequestNumber) || pullRequestNumber < 1) {
+    result.failures.push({ reason: 'invalid pull request number' });
+    return result;
+  }
+
+  const issueNumbers = extractLinkedIssueNumbers(pullRequest.body);
+  result.issueNumbers = issueNumbers;
+
+  for (const issueNumber of issueNumbers) {
+    try {
+      const issueResponse = await github.rest.issues.get({
+        owner: EXPECTED_OWNER,
+        repo: EXPECTED_REPOSITORY,
+        issue_number: issueNumber,
+      });
+      const issue = issueResponse.data;
+
+      if (issue.pull_request) {
+        result.skipped.push({ issueNumber, reason: 'target is a pull request' });
+        continue;
+      }
+
+      if (issue.state !== 'open') {
+        result.skipped.push({ issueNumber, reason: 'issue is already closed' });
+        continue;
+      }
+
+      const marker = getMarker(pullRequestNumber);
+      const comments = await github.paginate(github.rest.issues.listComments, {
+        owner: EXPECTED_OWNER,
+        repo: EXPECTED_REPOSITORY,
+        issue_number: issueNumber,
+        per_page: 100,
+      });
+      const alreadyAudited = comments.some((comment) =>
+        typeof comment.body === 'string' && comment.body.includes(marker),
+      );
+
+      if (!alreadyAudited) {
+        await github.rest.issues.createComment({
+          owner: EXPECTED_OWNER,
+          repo: EXPECTED_REPOSITORY,
+          issue_number: issueNumber,
+          body: `PR #${pullRequestNumber}가 develop에 병합되어 자동으로 종료되었습니다.\n\n${marker}\n${getPullRequestUrl(pullRequestNumber)}`,
+        });
+      }
+
+      await github.rest.issues.update({
+        owner: EXPECTED_OWNER,
+        repo: EXPECTED_REPOSITORY,
+        issue_number: issueNumber,
+        state: 'closed',
+        state_reason: 'completed',
+      });
+      result.closed.push(issueNumber);
+    } catch (error) {
+      if (error?.status === 404) {
+        result.skipped.push({ issueNumber, reason: 'issue does not exist' });
+      } else {
+        result.failures.push({ issueNumber, reason: errorMessage(error) });
+      }
+    }
+  }
+
+  return result;
+}
+
+async function writeSummary(core, result) {
+  if (!core?.summary) {
+    return;
+  }
+
+  const summary = core.summary
+    .addHeading('Develop PR Issue Automation')
+    .addRaw(`Closed: ${result.closed.join(', ') || 'none'}\n`)
+    .addRaw(`Skipped: ${result.skipped.length}\n`)
+    .addRaw(`Failures: ${result.failures.length}\n`);
+
+  if (result.skipped.length > 0) {
+    summary.addHeading('Skipped', 2).addTable([
+      [{ data: 'Issue', header: true }, { data: 'Reason', header: true }],
+      ...result.skipped.map((entry) => [
+        String(entry.issueNumber ?? '-'),
+        entry.reason,
+      ]),
+    ]);
+  }
+
+  if (result.failures.length > 0) {
+    summary.addHeading('Failures', 2).addTable([
+      [{ data: 'Issue', header: true }, { data: 'Reason', header: true }],
+      ...result.failures.map((entry) => [
+        String(entry.issueNumber ?? '-'),
+        entry.reason,
+      ]),
+    ]);
+  }
+
+  await summary.write();
+}
+
+module.exports = {
+  closeLinkedIssues,
+  extractLinkedIssueNumbers,
+  isTargetPullRequest,
+  stripNonContent,
+  writeSummary,
+};
diff --git a/.github/scripts/close-develop-issues.test.js b/.github/scripts/close-develop-issues.test.js
new file mode 100644
index 0000000..1c1cc78
--- /dev/null
+++ b/.github/scripts/close-develop-issues.test.js
@@ -0,0 +1,208 @@
+'use strict';
+
+const assert = require('node:assert/strict');
+const test = require('node:test');
+
+const {
+  closeLinkedIssues,
+  extractLinkedIssueNumbers,
+  isTargetPullRequest,
+} = require('./close-develop-issues');
+
+const repository = { full_name: 'CKLOB/MUDDA-Server' };
+const sameRepositoryHead = { repo: { full_name: 'CKLOB/MUDDA-Server' } };
+
+function createGithub(issues, comments = new Map()) {
+  const createdComments = [];
+  const updatedIssues = [];
+  const github = {
+    rest: {
+      issues: {
+        async get({ issue_number: issueNumber }) {
+          const issue = issues[issueNumber];
+          if (issue instanceof Error) {
+            throw issue;
+          }
+          if (!issue) {
+            const error = new Error('Not Found');
+            error.status = 404;
+            throw error;
+          }
+          return { data: issue };
+        },
+        async listComments() {
+          return { data: [] };
+        },
+        async createComment(params) {
+          createdComments.push(params);
+          return { data: params };
+        },
+        async update(params) {
+          updatedIssues.push(params);
+          return { data: params };
+        },
+      },
+    },
+    async paginate(_method, { issue_number: issueNumber }) {
+      return comments.get(issueNumber) ?? [];
+    },
+  };
+
+  return { github, createdComments, updatedIssues };
+}
+
+test('extracts official keywords, colon variants, and deduplicates issue numbers', () => {
+  assert.deepEqual(
+    extractLinkedIssueNumbers(
+      'Closes #32, closes #34\nFIXED: #35\nResolves: #32\nclosed #36',
+    ),
+    [32, 34, 35, 36],
+  );
+});
+
+test('ignores non-closing references and masked markdown content', () => {
+  const fencedCodeBlock = ['```markdown', 'Closes #7', '```'].join('\n');
+
+  assert.deepEqual(
+    extractLinkedIssueNumbers(
+      [
+        'Refs #1',
+        'Related #2',
+        '#3',
+        'Closes #4, #5',
+        '`Closes #6`',
+        fencedCodeBlock,
+        '<!-- Closes #8 -->',
+        'https://example.com/Closes%20%239',
+        'Closes CKLOB/other-repository#10',
+        '    Closes #12',
+        'Closes #0',
+        'Closes#11',
+      ].join('\n'),
+    ),
+    [4],
+  );
+});
+
+test('only accepts a merged PR targeting develop in this repository', () => {
+  const mergedDevelopPr = {
+    base: { ref: 'develop' },
+    head: sameRepositoryHead,
+    merged: true,
+  };
+  assert.equal(isTargetPullRequest(repository, mergedDevelopPr), true);
+  assert.equal(
+    isTargetPullRequest(repository, {
+      base: { ref: 'develop' },
+      head: sameRepositoryHead,
+      merged: false,
+    }),
+    false,
+  );
+  assert.equal(
+    isTargetPullRequest(repository, {
+      base: { ref: 'main' },
+      head: sameRepositoryHead,
+      merged: true,
+    }),
+    false,
+  );
+  assert.equal(
+    isTargetPullRequest(
+      { full_name: 'someone/another-repository' },
+      mergedDevelopPr,
+    ),
+    false,
+  );
+  assert.equal(
+    isTargetPullRequest(repository, {
+      base: { ref: 'develop' },
+      head: { repo: { full_name: 'someone/another-repository' } },
+      merged: true,
+    }),
+    false,
+  );
+});
+
+test('does not use a title reference when the body is empty or null', async () => {
+  const { github, updatedIssues } = createGithub({
+    1: { state: 'open' },
+  });
+
+  const result = await closeLinkedIssues({
+    github,
+    repository,
+    pullRequest: {
+      number: 35,
+      title: 'Closes #1',
+      body: null,
+      base: { ref: 'develop' },
+      head: sameRepositoryHead,
+      merged: true,
+    },
+  });
+
+  assert.deepEqual(result.issueNumbers, []);
+  assert.deepEqual(updatedIssues, []);
+});
+
+test('closes open issues once and does not duplicate an existing audit comment', async () => {
+  const existingMarker = '<!-- auto-close-develop-pr:35 -->';
+  const comments = new Map([[2, [{ body: `already audited ${existingMarker}` }]]]);
+  const { github, createdComments, updatedIssues } = createGithub(
+    {
+      1: { state: 'open' },
+      2: { state: 'open' },
+      3: { state: 'closed' },
+      4: { state: 'open', pull_request: {} },
+    },
+    comments,
+  );
+
+  const result = await closeLinkedIssues({
+    github,
+    repository,
+    pullRequest: {
+      number: 35,
+      body: 'Closes #1, fixes #2, resolves #1, closes #3, closes #4, closes #5',
+      base: { ref: 'develop' },
+      head: sameRepositoryHead,
+      merged: true,
+    },
+  });
+
+  assert.deepEqual(result.closed, [1, 2]);
+  assert.equal(createdComments.length, 1);
+  assert.equal(createdComments[0].issue_number, 1);
+  assert.equal(createdComments[0].body.includes('auto-close-develop-pr:35'), true);
+  assert.deepEqual(
+    updatedIssues.map((issue) => issue.issue_number),
+    [1, 2],
+  );
+});
+
+test('continues after an API failure and reports the failed issue', async () => {
+  const { github, updatedIssues } = createGithub({
+    1: Object.assign(new Error('rate limited'), { status: 429 }),
+    2: { state: 'open' },
+  });
+
+  const result = await closeLinkedIssues({
+    github,
+    repository,
+    pullRequest: {
+      number: 35,
+      body: 'Closes #1, fixes #2',
+      base: { ref: 'develop' },
+      head: sameRepositoryHead,
+      merged: true,
+    },
+  });
+
+  assert.deepEqual(result.closed, [2]);
+  assert.deepEqual(result.failures, [{ issueNumber: 1, reason: 'rate limited' }]);
+  assert.deepEqual(
+    updatedIssues.map((issue) => issue.issue_number),
+    [2],
+  );
+});
diff --git a/.github/workflows/close-develop-issues.yml b/.github/workflows/close-develop-issues.yml
new file mode 100644
index 0000000..a2c062b
--- /dev/null
+++ b/.github/workflows/close-develop-issues.yml
@@ -0,0 +1,67 @@
+name: Close Issues Linked from Develop PRs
+
+on:
+  pull_request:
+    types: [closed]
+
+permissions:
+  contents: read
+  pull-requests: read
+  issues: write
+
+concurrency:
+  group: close-develop-issues-${{ github.event.pull_request.number }}
+  cancel-in-progress: false
+
+jobs:
+  close-linked-issues:
+    if: >-
+      github.repository == 'CKLOB/MUDDA-Server' &&
+      github.event.pull_request.base.ref == 'develop' &&
+      github.event.pull_request.merged == true &&
+      github.event.pull_request.head.repo.full_name == github.repository
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    permissions:
+      contents: read
+      pull-requests: read
+      issues: write
+
+    steps:
+      # Always execute the trusted automation code from the default branch.
+      # Never checkout or execute the closed PR's head branch.
+      - name: Checkout automation code
+        uses: actions/checkout@v4
+        with:
+          ref: main
+          persist-credentials: false
+
+      - name: Close linked issues
+        uses: actions/github-script@v7
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          script: |
+            const path = require('node:path');
+            const {
+              closeLinkedIssues,
+              writeSummary,
+            } = require(
+              path.join(
+                process.env.GITHUB_WORKSPACE,
+                '.github/scripts/close-develop-issues.js',
+              ),
+            );
+
+            const result = await closeLinkedIssues({
+              github,
+              repository: context.payload.repository,
+              pullRequest: context.payload.pull_request,
+            });
+
+            await writeSummary(core, result);
+
+            if (result.failures.length > 0) {
+              core.setFailed(
+                `Failed to process ${result.failures.length} linked issue(s).`,
+              );
+            }
diff --git a/docs/GIT_FLOW.md b/docs/GIT_FLOW.md
new file mode 100644
index 0000000..dc6cf56
--- /dev/null
+++ b/docs/GIT_FLOW.md
@@ -0,0 +1,31 @@
+# Git Flow
+
+## 브랜치 역할
+
+- `main`: 운영·배포 안정 브랜치이자 GitHub 기본 브랜치
+- `develop`: 기능 통합 브랜치
+- `feature/*`, `fix/*`, `chore/*`: 작업 브랜치
+
+기능·수정·설정 변경 PR은 기본적으로 `develop`을 대상으로 생성합니다. `develop → main`은 별도의 릴리스 과정으로 진행하며, 기능 PR을 `main`에 직접 병합하지 않습니다.
+
+## Issue 연결
+
+완료한 Issue는 `develop` 대상 PR 본문에서 공식 closing keyword로 명시합니다.
+
+지원하는 keyword는 `close`, `closes`, `closed`, `fix`, `fixes`, `fixed`, `resolve`, `resolves`, `resolved`이며 대소문자를 구분하지 않습니다. `Closes #32`, `CLOSES: #32`, `Resolves: #34`처럼 작성할 수 있습니다.
+
+```text
+Closes #32
+Fixes #33
+Resolves: #34
+```
+
+여러 Issue를 종료하려면 각 번호에 keyword를 반복해서 작성합니다. `Closes #32, #33`처럼 두 번째 번호에 keyword가 없는 축약형은 지원하지 않습니다. `Related #N`, `Refs #N`, 단순 `#N`, PR 제목·브랜치·커밋 메시지의 번호는 자동 종료 대상으로 사용하지 않습니다.
+
+## 자동 종료 Workflow
+
+`.github/workflows/close-develop-issues.yml`은 PR이 실제로 병합되어 닫힌 경우에만 실행되며, base가 정확히 `develop`인 같은 저장소 PR 본문을 검사합니다. 연결된 같은 저장소의 열린 Issue만 검증한 뒤 감사 Comment를 남기고 `completed` 사유로 종료합니다. `main` 대상 릴리스 PR이나 닫히기만 한 미병합 PR은 처리하지 않습니다.
+
+Workflow는 PR Head 코드를 실행하지 않고 기본 브랜치 `main`의 자동화 코드를 사용합니다. 따라서 이 자동화 PR이 `main`에 병합된 이후부터 동작하며, 병합 후 `main → develop` 동기화가 필요합니다.
+
+보안상 외부 Fork에서 생성된 PR은 자동 종료 대상에서 제외합니다. Fork PR의 `GITHUB_TOKEN`은 Issue 쓰기 권한이 제한될 수 있으므로, 권한을 확대하거나 `pull_request_target`을 사용하지 않고 같은 저장소 브랜치의 PR만 처리합니다.