diff --git a/examples/express/expected/oas.json b/examples/express/expected/oas.json
index c98ba29..22475a0 100644
--- a/examples/express/expected/oas.json
+++ b/examples/express/expected/oas.json
@@ -89,7 +89,7 @@
                 }
             }
         },
-        "/users/:userId": {
+        "/users/{userId}": {
             "get": {
                 "summary": "사용자 조회 API",
                 "tags": ["User"],
@@ -383,7 +383,7 @@
                 }
             }
         },
-        "/users/:userId/friends/:friendName": {
+        "/users/{userId}/friends/{friendName}": {
             "delete": {
                 "summary": "특정 사용자의 친구를 삭제합니다.",
                 "tags": ["User"],
diff --git a/lib/__tests__/unit/dsl/OpenAPIGenerator.test.ts b/lib/__tests__/unit/dsl/OpenAPIGenerator.test.ts
index 26860f4..53d5c9f 100644
--- a/lib/__tests__/unit/dsl/OpenAPIGenerator.test.ts
+++ b/lib/__tests__/unit/dsl/OpenAPIGenerator.test.ts
@@ -231,4 +231,42 @@ describe("OpenAPIGenerator", () => {
             assert.isUndefined(spec.paths["/test/no-body-responses"].get.responses["400"].content)
         })
     })
+
+    describe("normalizePathTemplate", () => {
+        it("should handle paths without parameters", () => {
+            const generator = OpenAPIGenerator.getInstance()
+            const normalized = generator["normalizePathTemplate"]("/users")
+            assert.strictEqual(normalized, "/users")
+        })
+
+        it("should handle mixed format paths", () => {
+            const generator = OpenAPIGenerator.getInstance()
+            const normalized = generator["normalizePathTemplate"]("/users/{userId}/posts/:postId")
+            assert.strictEqual(normalized, "/users/{userId}/posts/{postId}")
+        })
+
+        it("should handle parameters with underscores", () => {
+            const generator = OpenAPIGenerator.getInstance()
+            const normalized = generator["normalizePathTemplate"]("/items/:item_id")
+            assert.strictEqual(normalized, "/items/{item_id}")
+        })
+
+        it("should handle empty path", () => {
+            const generator = OpenAPIGenerator.getInstance()
+            const normalized = generator["normalizePathTemplate"]("")
+            assert.strictEqual(normalized, "")
+        })
+
+        it("should handle root path", () => {
+            const generator = OpenAPIGenerator.getInstance()
+            const normalized = generator["normalizePathTemplate"]("/")
+            assert.strictEqual(normalized, "/")
+        })
+
+        it("should handle hyphenated parameter names", () => {
+            const generator = OpenAPIGenerator.getInstance()
+            const normalized = generator["normalizePathTemplate"]("/files/:file-name")
+            assert.strictEqual(normalized, "/files/{file-name}")
+        })
+    })
 })
diff --git a/lib/dsl/generator/OpenAPIGenerator.ts b/lib/dsl/generator/OpenAPIGenerator.ts
index 1a2a38b..88a0afa 100644
--- a/lib/dsl/generator/OpenAPIGenerator.ts
+++ b/lib/dsl/generator/OpenAPIGenerator.ts
@@ -130,10 +130,15 @@ export class OpenAPIGenerator implements IOpenAPIGenerator {
         const paths: Record<string, Record<string, unknown>> = {}
 
         for (const [path, methods] of groupedResults) {
-            paths[path] = {}
+            const normalizedPath = this.normalizePathTemplate(path)
+            paths[normalizedPath] = {}
 
             for (const [method, statusCodes] of methods) {
-                paths[path][method] = this.generateOperationObject(path, method, statusCodes)
+                paths[normalizedPath][method] = this.generateOperationObject(
+                    normalizedPath,
+                    method,
+                    statusCodes,
+                )
             }
         }
 
@@ -533,8 +538,7 @@ export class OpenAPIGenerator implements IOpenAPIGenerator {
      */
     private validatePathParameters(paths: Record<string, Record<string, unknown>>): void {
         for (const [path, pathItem] of Object.entries(paths)) {
-            const pathParamMatches = path.match(/:([^/]+)/g) || []
-            const pathParams = pathParamMatches.map((param) => param.slice(1))
+            const pathParams = this.extractPathParameterNames(path)
 
             if (pathParams.length === 0) continue
 
@@ -571,6 +575,30 @@ export class OpenAPIGenerator implements IOpenAPIGenerator {
         }
     }
 
+    /**
+     * Converts colon-prefixed Express parameters to OpenAPI-compatible templates.
+     * @param {string} path Raw route path
+     * @returns {string} Normalized OpenAPI path
+     */
+    private normalizePathTemplate(path: string): string {
+        return path.replace(/:([A-Za-z0-9_-]+)/g, "{$1}")
+    }
+
+    /**
+     * Extracts parameter names from a normalized or raw path template.
+     * @param {string} path Path string potentially containing parameters
+     * @returns {string[]} Parameter names
+     */
+    private extractPathParameterNames(path: string): string[] {
+        const braceMatches = path.match(/\{([^}]+)\}/g) || []
+        if (braceMatches.length > 0) {
+            return braceMatches.map((param) => param.slice(1, -1))
+        }
+
+        const colonMatches = path.match(/:([^/]+)/g) || []
+        return colonMatches.map((param) => param.slice(1))
+    }
+
     /**
      * Normalizes examples according to the schema.
      * @param {any} example Example value
diff --git a/lib/dsl/test-builders/RequestBuilder.ts b/lib/dsl/test-builders/RequestBuilder.ts
index 2a89b40..8b4ae50 100644
--- a/lib/dsl/test-builders/RequestBuilder.ts
+++ b/lib/dsl/test-builders/RequestBuilder.ts
@@ -19,6 +19,7 @@ import { DSLField } from "../interface"
 import { ResponseBuilder } from "./ResponseBuilder"
 import { FIELD_TYPES } from "../interface/field"
 import { AbstractTestBuilder } from "./AbstractTestBuilder"
+import logger from "../../config/logger"
 
 /**
  * Builder class for setting API request information.
@@ -31,9 +32,18 @@ export class RequestBuilder extends AbstractTestBuilder {
      */
     public header(headers: Record<string, DSLField<string>>): this {
         const normalizedHeaders: Record<string, DSLField<string>> = {}
+        const seen = new Set<string>()
 
         Object.entries(headers).forEach(([headerName, headerValue]) => {
-            normalizedHeaders[headerName.toLowerCase()] = headerValue
+            const normalized = headerName.toLowerCase()
+
+            if (seen.has(normalized)) {
+                logger.warn(`Duplicate header detected: "${headerName}" (already set)`)
+                return
+            }
+
+            seen.add(normalized)
+            normalizedHeaders[normalized] = headerValue
         })
 
         this.config.requestHeaders = normalizedHeaders