diff --git a/.github/workflows/openapi-breaking-change.yml b/.github/workflows/openapi-breaking-change.yml
new file mode 100644
index 000000000..eee471375
--- /dev/null
+++ b/.github/workflows/openapi-breaking-change.yml
@@ -0,0 +1,178 @@
+name: OpenAPI Breaking Change Detection
+
+on:
+  pull_request:
+    paths:
+      - "BackEnd/src/**"
+      - "BackEnd/package.json"
+      - ".github/workflows/openapi-breaking-change.yml"
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  detect-breaking-changes:
+    name: Diff OpenAPI Spec
+    runs-on: ubuntu-latest
+
+    env:
+      # Minimal env so NestJS can bootstrap without a real database/redis
+      NODE_ENV: production
+      JWT_SECRET: ci-placeholder-secret-32-chars-ok
+      JWT_REFRESH_SECRET: ci-placeholder-refresh-secret-ok
+      JWT_ACCESS_TOKEN_EXPIRATION: 15m
+      JWT_REFRESH_TOKEN_EXPIRATION: 7d
+      DATABASE_URL: postgres://ci:ci@localhost:5432/ci
+      REDIS_URL: redis://localhost:6379
+      STELLAR_NETWORK: testnet
+      # Silence optional integrations
+      SENTRY_DSN: ""
+      OTEL_SDK_DISABLED: "true"
+
+    steps:
+      - name: Checkout PR branch
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0   # need full history to check out base branch
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20
+
+      - name: Cache npm dependencies
+        uses: actions/cache@v4
+        with:
+          path: ~/.npm
+          key: ${{ runner.os }}-backend-npm-${{ hashFiles('BackEnd/package-lock.json') }}
+          restore-keys: |
+            ${{ runner.os }}-backend-npm-
+
+      # ── Generate spec for the PR branch ────────────────────────────────────
+      - name: Install dependencies (PR branch)
+        run: npm ci
+        working-directory: BackEnd
+
+      - name: Generate OpenAPI spec (PR branch)
+        run: npx ts-node -r tsconfig-paths/register scripts/generate-openapi.ts openapi-pr.json
+        working-directory: BackEnd
+
+      # ── Switch to base branch and generate its spec ────────────────────────
+      - name: Checkout base branch (${{ github.base_ref }})
+        run: git checkout origin/${{ github.base_ref }}
+
+      - name: Install dependencies (base branch)
+        run: npm ci
+        working-directory: BackEnd
+
+      - name: Generate OpenAPI spec (base branch)
+        run: npx ts-node -r tsconfig-paths/register scripts/generate-openapi.ts openapi-base.json
+        working-directory: BackEnd
+
+      # ── Restore PR files so artifacts are accessible ───────────────────────
+      - name: Restore PR branch files
+        run: git checkout ${{ github.sha }} -- BackEnd/openapi-pr.json
+
+      # ── Install oasdiff and run the diff ───────────────────────────────────
+      - name: Install oasdiff
+        run: |
+          curl -sSL https://raw.githubusercontent.com/tufin/oasdiff/main/install.sh | sh
+          echo "$HOME/.oasdiff/bin" >> $GITHUB_PATH
+
+      - name: Detect breaking changes
+        id: diff
+        run: |
+          set +e
+          oasdiff breaking \
+            BackEnd/openapi-base.json \
+            BackEnd/openapi-pr.json \
+            --format text > breaking-changes.txt 2>&1
+          EXIT_CODE=$?
+          set -e
+
+          echo "exit_code=$EXIT_CODE" >> $GITHUB_OUTPUT
+
+          if [ -s breaking-changes.txt ]; then
+            echo "has_changes=true" >> $GITHUB_OUTPUT
+          else
+            echo "has_changes=false" >> $GITHUB_OUTPUT
+          fi
+
+      - name: Post PR comment with breaking changes
+        if: steps.diff.outputs.has_changes == 'true'
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const fs = require('fs');
+            const changes = fs.readFileSync('breaking-changes.txt', 'utf8');
+            const body = [
+              '## ⚠️ OpenAPI Breaking Changes Detected',
+              '',
+              'The following breaking changes were found between `${{ github.base_ref }}` and this PR:',
+              '',
+              '```',
+              changes.trim(),
+              '```',
+              '',
+              'Please review these changes. If they are intentional, bump the API version and update the changelog.',
+            ].join('\n');
+
+            const { data: comments } = await github.rest.issues.listComments({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: context.issue.number,
+            });
+
+            const existing = comments.find(c =>
+              c.user.login === 'github-actions[bot]' &&
+              c.body.startsWith('## ⚠️ OpenAPI Breaking Changes Detected')
+            );
+
+            if (existing) {
+              await github.rest.issues.updateComment({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                comment_id: existing.id,
+                body,
+              });
+            } else {
+              await github.rest.issues.createComment({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                issue_number: context.issue.number,
+                body,
+              });
+            }
+
+      - name: Upload spec artifacts
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: openapi-specs-${{ github.run_id }}
+          path: |
+            BackEnd/openapi-base.json
+            BackEnd/openapi-pr.json
+            breaking-changes.txt
+          retention-days: 14
+
+      - name: Fail on breaking changes
+        if: steps.diff.outputs.exit_code != '0'
+        run: |
+          echo "::error::Breaking API changes detected. See the PR comment and breaking-changes.txt artifact for details."
+          exit 1
+
+      - name: Workflow summary
+        if: always()
+        run: |
+          echo "## OpenAPI Breaking Change Detection" >> $GITHUB_STEP_SUMMARY
+          echo "" >> $GITHUB_STEP_SUMMARY
+          if [ "${{ steps.diff.outputs.exit_code }}" = "0" ]; then
+            echo "✅ No breaking changes detected." >> $GITHUB_STEP_SUMMARY
+          else
+            echo "❌ Breaking changes were found — see artifact \`breaking-changes.txt\`." >> $GITHUB_STEP_SUMMARY
+            echo "" >> $GITHUB_STEP_SUMMARY
+            echo '```' >> $GITHUB_STEP_SUMMARY
+            cat breaking-changes.txt >> $GITHUB_STEP_SUMMARY
+            echo '```' >> $GITHUB_STEP_SUMMARY
+          fi
diff --git a/BackEnd/.gitignore b/BackEnd/.gitignore
index a1a2e3e7f..4ff47a375 100644
--- a/BackEnd/.gitignore
+++ b/BackEnd/.gitignore
@@ -59,3 +59,8 @@ report.[0-9]*.[0-9]*.[0-9]*.[0-9]*.json
 
 /generated/prisma
 /exports
+
+# Generated OpenAPI spec (produced by scripts/generate-openapi.ts)
+openapi.json
+openapi-base.json
+openapi-pr.json
diff --git a/BackEnd/package.json b/BackEnd/package.json
index 752aee38f..04f31f12f 100644
--- a/BackEnd/package.json
+++ b/BackEnd/package.json
@@ -45,6 +45,7 @@
     "schema:sync": "bun run typeorm -- schema:sync",
     "schema:drop": "bun run typeorm -- schema:drop",
     "schema:log": "bun run typeorm -- schema:log",
+    "generate:openapi": "ts-node -r tsconfig-paths/register scripts/generate-openapi.ts openapi.json"
     "check:toolchain": "ts-node scripts/check-toolchain.ts",
     "onboarding": "ts-node scripts/check-toolchain.ts"
   },
diff --git a/BackEnd/scripts/generate-openapi.ts b/BackEnd/scripts/generate-openapi.ts
index a4bdd7b47..6c1b3c7fd 100644
--- a/BackEnd/scripts/generate-openapi.ts
+++ b/BackEnd/scripts/generate-openapi.ts
@@ -1,4 +1,43 @@
 /**
+ * Standalone script to generate the OpenAPI spec JSON file.
+ * Used by CI to produce a spec artifact for breaking-change diffing.
+ *
+ * Usage: ts-node scripts/generate-openapi.ts [output-path]
+ * Default output: openapi.json (repo root of BackEnd)
+ */
+import { NestFactory } from '@nestjs/core';
+import { DocumentBuilder, SwaggerModule } from '@nestjs/swagger';
+import { writeFileSync } from 'fs';
+import { resolve } from 'path';
+
+// Minimal env defaults so the app can bootstrap without a full .env
+process.env.NODE_ENV = process.env.NODE_ENV ?? 'production';
+process.env.JWT_SECRET =
+  process.env.JWT_SECRET ?? 'ci-placeholder-secret-32-chars-ok';
+process.env.JWT_REFRESH_SECRET =
+  process.env.JWT_REFRESH_SECRET ?? 'ci-placeholder-refresh-secret-ok';
+process.env.JWT_ACCESS_TOKEN_EXPIRATION =
+  process.env.JWT_ACCESS_TOKEN_EXPIRATION ?? '15m';
+process.env.JWT_REFRESH_TOKEN_EXPIRATION =
+  process.env.JWT_REFRESH_TOKEN_EXPIRATION ?? '7d';
+process.env.DATABASE_URL =
+  process.env.DATABASE_URL ?? 'postgres://ci:ci@localhost:5432/ci';
+process.env.REDIS_URL = process.env.REDIS_URL ?? 'redis://localhost:6379';
+process.env.STELLAR_NETWORK = process.env.STELLAR_NETWORK ?? 'testnet';
+
+async function generate() {
+  // Lazy import so env defaults are set first
+  const { AppModule } = await import('../src/app.module');
+
+  const app = await NestFactory.create(AppModule, { logger: false });
+  app.setGlobalPrefix('api');
+
+  const builder = new DocumentBuilder()
+    .setTitle('StellarEarn API')
+    .setDescription('Quest-based earning platform on Stellar blockchain')
+    .setVersion('1.0')
+    .addServer('/api/v1', 'API v1')
+    .addServer('/api/v2', 'API v2')
  * generate-openapi.ts
  *
  * Headless NestJS bootstrap that produces the OpenAPI JSON specification
@@ -113,6 +152,17 @@ async function main(): Promise<void> {
     deepScanRoutes: true,
   });
 
+  const outputPath = resolve(
+    process.argv[2] ?? `${__dirname}/../openapi.json`,
+  );
+  writeFileSync(outputPath, JSON.stringify(document, null, 2));
+  console.log(`OpenAPI spec written to ${outputPath}`);
+
+  await app.close();
+}
+
+generate().catch((err) => {
+  console.error('Failed to generate OpenAPI spec:', err);
   // Validate the generated document has the expected structure
   if (!document.openapi) {
     throw new Error('[openapi-gen] Generated document is missing "openapi" field');
diff --git a/BackEnd/tsconfig.json b/BackEnd/tsconfig.json
index d8b789903..2c87b1d62 100644
--- a/BackEnd/tsconfig.json
+++ b/BackEnd/tsconfig.json
@@ -26,6 +26,6 @@
       "#src/*": ["src/*"]
     }
   },
-  "include": ["src/**/*"],
+  "include": ["src/**/*", "scripts/**/*"],
   "exclude": ["node_modules", "dist"]
 }
\ No newline at end of file
diff --git a/BackEnd/tsconfig.scripts.json b/BackEnd/tsconfig.scripts.json
new file mode 100644
index 000000000..5770914eb
--- /dev/null
+++ b/BackEnd/tsconfig.scripts.json
@@ -0,0 +1,8 @@
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "outDir": "./dist-scripts",
+    "noEmit": true
+  },
+  "include": ["scripts/**/*", "src/**/*"]
+}