fix(headers): 兼容非 ASCII header 值，避免 httpx ASCII 编码报错

将 HeaderBuilder 中的 latin-1 透传方案替换为 ASCII 归一化策略：
- 对 x-codex-turn-metadata 做 JSON 重编码（ensure_ascii=true）保留语义
- 其他非 ASCII 头值仅转义非 ASCII 字符为 \uXXXX，保留 ASCII 字符原样
- 新增单测覆盖中文 header 与 codex turn metadata 场景

Close #180

Co-Authored-By: AAEE86 <ppk0227@hotmail.com>

src/core/api_format/headers.py

@@ -12,6 +12,7 @@
 
 from __future__ import annotations
 
+import json
 from collections.abc import Set as AbstractSet
 from typing import Any
 
@@ -365,27 +366,48 @@ class HeaderBuilder:
         return self
 
     def build(self) -> dict[str, str]:
-        """构建最终的头部字典
-
-        httpx 要求 header 值可被 latin-1 编码。对于包含非 latin-1 字符
-        （如中文）的值，先 UTF-8 编码再按 latin-1 解码，使 httpx 将原始
-        UTF-8 字节逐字节发送到上游 —— 与 Go net/http 的行为一致。
-        """
+        """构建最终的头部字典"""
         result: dict[str, str] = {}
         for original_key, value in self._headers.values():
-            try:
-                value.encode("latin-1")
-            except (UnicodeEncodeError, UnicodeDecodeError):
-                # 将 UTF-8 字节逐字节映射为 latin-1 字符串，httpx 会原样发送
-                logger.debug(
-                    "Header '{}' contains non-latin-1 chars, encoding as raw UTF-8 bytes",
-                    original_key,
-                )
-                value = value.encode("utf-8").decode("latin-1")
-            result[original_key] = value
+            result[original_key] = _normalize_header_value_for_httpx(original_key, value)
         return result
 
 
+def _normalize_header_value_for_httpx(key: str, value: str) -> str:
+    """将 header 值归一化为 httpx/h11 可发送的 ASCII 字符串。
+
+    说明：
+    - 当前 httpx/h11 栈会对 str 类型 header 值执行 ASCII 编码。
+    - 若值包含非 ASCII 字符（如中文），会抛出 UnicodeEncodeError。
+    - 因此这里统一做 ASCII 归一化，确保请求可稳定发出。
+    """
+    if value.isascii():
+        return value
+
+    key_lower = key.lower()
+
+    # Codex CLI 元数据是 JSON 字符串，优先重编码为 ASCII JSON，语义最稳定。
+    if key_lower == "x-codex-turn-metadata":
+        try:
+            normalized = json.dumps(json.loads(value), ensure_ascii=True, separators=(",", ":"))
+            logger.debug(
+                "Header '{}' contains non-ASCII chars, normalized as ASCII JSON",
+                key,
+            )
+            return normalized
+        except Exception:
+            # 非法 JSON 时走通用兜底，避免阻断请求。
+            pass
+
+    # 兜底：仅将非 ASCII 字符替换为 \uXXXX，保留 ASCII 字符原样
+    escaped = "".join(c if c.isascii() else f"\\u{ord(c):04x}" for c in value)
+    logger.warning(
+        "Header '{}' contains non-ASCII chars, escaped for httpx compatibility",
+        key,
+    )
+    return escaped
+
+
 def build_upstream_headers_for_endpoint(
     original_headers: dict[str, str],
     endpoint: str | EndpointSignature | tuple,

tests/unit/test_headers.py

@@ -1,3 +1,5 @@
+import json
+
 from src.core.api_format import (
     CORE_REDACT_HEADERS,
     HeaderBuilder,
@@ -73,6 +75,23 @@ class TestHeaderBuilder:
         assert built["Authorization"] == "base"
         assert built["X-Test"] == "1"
 
+    def test_non_ascii_value_is_escaped_for_httpx(self) -> None:
+        builder = HeaderBuilder()
+        builder.add("X-Test", "桌面")
+        built = builder.build()
+        assert built["X-Test"] == r"\u684c\u9762"
+
+    def test_codex_turn_metadata_is_normalized_to_ascii_json(self) -> None:
+        builder = HeaderBuilder()
+        raw = '{"turn_id":"t1","workspaces":{"d:\\\\桌面\\\\123\\\\Aether":{"has_changes":true}}}'
+        builder.add("x-codex-turn-metadata", raw)
+        built = builder.build()
+
+        normalized = built["x-codex-turn-metadata"]
+        assert normalized.isascii()
+        parsed = json.loads(normalized)
+        assert "d:\\桌面\\123\\Aether" in parsed["workspaces"]
+
 
 class TestBuildUpstreamHeaders:
     def test_priority_and_drop_headers(self) -> None: