diff --git a/src/main/java/com/yunhai/platform/gateway/filter/SanitizeFilter.java b/src/main/java/com/yunhai/platform/gateway/filter/SanitizeFilter.java
new file mode 100644
index 0000000..552da89
--- /dev/null
+++ b/src/main/java/com/yunhai/platform/gateway/filter/SanitizeFilter.java
@@ -0,0 +1,104 @@
+package com.yunhai.platform.gateway.filter;
+
+import com.yunhai.platform.gateway.envelope.EnvelopeWriter;
+import org.springframework.core.annotation.Order;
+import org.springframework.stereotype.Component;
+
+import javax.servlet.Filter;
+import javax.servlet.FilterChain;
+import javax.servlet.ServletException;
+import javax.servlet.ServletRequest;
+import javax.servlet.ServletResponse;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import java.io.IOException;
+
+/**
+ * 请求规整化（T1.1，安全链第一环）：进转发链前对 URI 做解码归一化检查，
+ * 杜绝路径穿越/编码绕过。<b>只拒绝不修复</b>（不做自动纠错）；query 部分不动
+ * （canonical 计算按 F1 排序规则处理）。
+ * <p>
+ * 拒绝（裸 400）条件——对 percent-decode 后的 URI 判定：
+ * 含 {@code ..}（含编码形态 {@code %2e%2e}）、路径含双斜杠 {@code //}、
+ * 含控制字符（0x00-0x1f，含空字节）。
+ * <p>
+ * 通过后把<b>原始 URI</b>（逐字节不改写——T0.12 forwardUrl 与 T1.2 canonical 都消费原始形态）
+ * 与剥掉 target 首段后的路径存 request attribute，后续过滤器与转发器一律取此值。
+ */
+@Component
+@Order(1)
+public class SanitizeFilter implements Filter {
+
+    public static final String ATTR_SANITIZED_URI = "yh.gateway.sanitized.uri";
+    public static final String ATTR_STRIPPED_PATH = "yh.gateway.stripped.path";
+
+    @Override
+    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
+            throws IOException, ServletException {
+        if (!(request instanceof HttpServletRequest) || !(response instanceof HttpServletResponse)) {
+            chain.doFilter(request, response);
+            return;
+        }
+        HttpServletRequest req = (HttpServletRequest) request;
+        HttpServletResponse res = (HttpServletResponse) response;
+        String uri = req.getRequestURI();
+        String decoded = percentDecode(uri);
+        if (isRejected(decoded)) {
+            EnvelopeWriter.writeBare(res, 400);
+            return;
+        }
+        req.setAttribute(ATTR_SANITIZED_URI, uri);
+        req.setAttribute(ATTR_STRIPPED_PATH, stripTargetSegment(uri));
+        chain.doFilter(request, response);
+    }
+
+    /** 解码后含 ..、双斜杠、控制字符（含空字节）即拒 */
+    static boolean isRejected(String decodedUri) {
+        if (decodedUri == null || decodedUri.isEmpty()) {
+            return true;
+        }
+        if (decodedUri.contains("..")) {
+            return true;
+        }
+        if (decodedUri.contains("//")) {
+            return true;
+        }
+        for (int i = 0; i < decodedUri.length(); i++) {
+            if (decodedUri.charAt(i) <= '\u001f') {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    /** percent-decode（仅 %XX；'+' 保持字面——path 部分 + 是合法字符，不走 query 规则） */
+    static String percentDecode(String s) {
+        if (s == null || s.indexOf('%') < 0) {
+            return s;
+        }
+        StringBuilder sb = new StringBuilder(s.length());
+        for (int i = 0; i < s.length(); i++) {
+            char c = s.charAt(i);
+            if (c == '%' && i + 2 < s.length()) {
+                int hi = Character.digit(s.charAt(i + 1), 16);
+                int lo = Character.digit(s.charAt(i + 2), 16);
+                if (hi >= 0 && lo >= 0) {
+                    sb.append((char) ((hi << 4) | lo));
+                    i += 2;
+                    continue;
+                }
+            }
+            sb.append(c);
+        }
+        return sb.toString();
+    }
+
+    /** 剥 target 首段：/userbase/oapi/x → /oapi/x；无第二段原样返回（target 判定是 TargetRouter 职责） */
+    static String stripTargetSegment(String uri) {
+        if (uri == null || uri.isEmpty()) {
+            return uri;
+        }
+        int second = uri.indexOf('/', 1);
+        return second < 0 ? uri : uri.substring(second);
+    }
+}
diff --git a/src/test/java/com/yunhai/platform/gateway/filter/SanitizeFilterTest.java b/src/test/java/com/yunhai/platform/gateway/filter/SanitizeFilterTest.java
new file mode 100644
index 0000000..ae95d96
--- /dev/null
+++ b/src/test/java/com/yunhai/platform/gateway/filter/SanitizeFilterTest.java
@@ -0,0 +1,61 @@
+package com.yunhai.platform.gateway.filter;
+
+import com.yunhai.platform.gateway.envelope.EnvelopeWriter;
+import org.junit.jupiter.api.Test;
+import org.springframework.mock.web.MockFilterChain;
+import org.springframework.mock.web.MockHttpServletRequest;
+import org.springframework.mock.web.MockHttpServletResponse;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * SanitizeFilter 五用例（T1.1 TDD）：路径穿越（明文/编码）、双斜杠、控制字符均裸 400；
+ * 正常路径放行且两个 attribute 契约已设。
+ */
+class SanitizeFilterTest {
+
+    private MockHttpServletResponse run(String uri) throws Exception {
+        MockHttpServletRequest req = new MockHttpServletRequest("GET", uri);
+        MockHttpServletResponse res = new MockHttpServletResponse();
+        MockFilterChain chain = new MockFilterChain();
+        new SanitizeFilter().doFilter(req, res, chain);
+        return res;
+    }
+
+    @Test
+    void 路径穿越_裸400() throws Exception {
+        assertThat(run("/userbase/oapi/a/../b").getStatus()).isEqualTo(400);
+    }
+
+    @Test
+    void 编码形态路径穿越_裸400() throws Exception {
+        assertThat(run("/userbase/oapi/%2e%2e/b").getStatus()).isEqualTo(400);
+        assertThat(run("/userbase/oapi/%2E%2E%2Fetc").getStatus()).isEqualTo(400);
+    }
+
+    @Test
+    void 路径双斜杠_裸400() throws Exception {
+        assertThat(run("/userbase//oapi/x").getStatus()).isEqualTo(400);
+        assertThat(run("/userbase/oapi//list").getStatus()).isEqualTo(400);
+    }
+
+    @Test
+    void 控制字符与空字节_裸400() throws Exception {
+        assertThat(run("/userbase/oapi/a\u0000b").getStatus()).isEqualTo(400);
+        assertThat(run("/userbase/oapi/a\u001fb").getStatus()).isEqualTo(400);
+    }
+
+    @Test
+    void 正常路径放行且attribute已设() throws Exception {
+        MockHttpServletRequest req = new MockHttpServletRequest("GET", "/userbase/oapi/x");
+        MockHttpServletResponse res = new MockHttpServletResponse();
+        MockFilterChain chain = new MockFilterChain();
+        new SanitizeFilter().doFilter(req, res, chain);
+        assertThat(res.getStatus()).as("正常路径放行").isEqualTo(200);
+        assertThat(chain.getRequest()).as("链条继续").isNotNull();
+        assertThat(req.getAttribute(SanitizeFilter.ATTR_SANITIZED_URI))
+                .as("sanitized.uri = 原始 URI（逐字节不改写）").isEqualTo("/userbase/oapi/x");
+        assertThat(req.getAttribute(SanitizeFilter.ATTR_STRIPPED_PATH))
+                .as("stripped.path = 剥 target 首段").isEqualTo("/oapi/x");
+    }
+}