feat(codex): 基于用户 API key 生成稳定的 prompt_cache_key，实现跨 provider key 的 prompt 缓存复用

- prepare_context 传递 user_api_key_id 到 CodexRequestContext
- wrap_request 中调用 patch_openai_cli_request_for_codex 注入 prompt_cache_key
- 客户端已提供 prompt_cache_key 时不覆盖
- 补充对应单元测试

tests/services/test_codex_request.py

@@ -6,7 +6,9 @@ import jwt
 import pytest
 
 from src.api.handlers.base.request_builder import PassthroughRequestBuilder
+from src.services.provider.adapters.codex.context import set_codex_request_context
 from src.services.provider.adapters.codex.request_patching import (
+    build_stable_codex_prompt_cache_key,
     maybe_patch_request_for_codex,
     patch_openai_cli_request_for_codex,
 )
@@ -47,6 +49,37 @@ def test_patch_openai_cli_request_for_codex_is_passthrough_except_internal_senti
     assert out["input"][0]["role"] == "system"
 
 
+def test_patch_openai_cli_request_for_codex_generates_stable_prompt_cache_key_from_user_api_key_id() -> (
+    None
+):
+    req = {"model": "gpt-test", "input": []}
+
+    out = patch_openai_cli_request_for_codex(req, user_api_key_id="user-key-123")
+
+    assert out is not req
+    assert out["prompt_cache_key"] == build_stable_codex_prompt_cache_key("user-key-123")
+
+
+def test_patch_openai_cli_request_for_codex_preserves_existing_prompt_cache_key() -> None:
+    req = {"model": "gpt-test", "input": [], "prompt_cache_key": "client-cache-key"}
+
+    out = patch_openai_cli_request_for_codex(req, user_api_key_id="user-key-123")
+
+    assert out["prompt_cache_key"] == "client-cache-key"
+
+
+def test_patch_openai_cli_request_for_codex_ignores_provider_key_and_uses_only_user_api_key_id() -> (
+    None
+):
+    req = {"model": "gpt-test", "input": []}
+
+    out_a = patch_openai_cli_request_for_codex(req, user_api_key_id="user-key-123")
+    out_b = patch_openai_cli_request_for_codex(req, user_api_key_id="user-key-123")
+
+    assert out_a["prompt_cache_key"] == out_b["prompt_cache_key"]
+    assert out_a["prompt_cache_key"] == build_stable_codex_prompt_cache_key("user-key-123")
+
+
 def test_maybe_patch_request_for_codex_is_noop_for_non_codex() -> None:
     req = {"model": "gpt-test", "input": []}
     out = maybe_patch_request_for_codex(
@@ -119,6 +152,66 @@ def test_codex_envelope_extra_headers_does_not_inject_synthetic_headers() -> Non
     assert codex_oauth_envelope.extra_headers() is None
 
 
+def test_codex_envelope_wrap_request_injects_stable_prompt_cache_key_from_user_api_key() -> None:
+    from src.services.provider.adapters.codex.envelope import codex_oauth_envelope
+
+    try:
+        codex_oauth_envelope.prepare_context(
+            provider_config=None,
+            key_id="provider-key-123",
+            user_api_key_id="user-key-123",
+            is_stream=True,
+        )
+        out, url_model = codex_oauth_envelope.wrap_request(
+            {"model": "gpt-test", "input": []},
+            model="gpt-test",
+            url_model=None,
+            decrypted_auth_config=None,
+        )
+    finally:
+        set_codex_request_context(None)
+
+    assert url_model is None
+    assert out["prompt_cache_key"] == build_stable_codex_prompt_cache_key("user-key-123")
+
+
+def test_codex_envelope_wrap_request_same_user_different_provider_keys_share_prompt_cache_key() -> (
+    None
+):
+    from src.services.provider.adapters.codex.envelope import codex_oauth_envelope
+
+    try:
+        codex_oauth_envelope.prepare_context(
+            provider_config=None,
+            key_id="provider-key-123",
+            user_api_key_id="user-key-123",
+            is_stream=True,
+        )
+        out_a, _ = codex_oauth_envelope.wrap_request(
+            {"model": "gpt-test", "input": []},
+            model="gpt-test",
+            url_model=None,
+            decrypted_auth_config=None,
+        )
+        codex_oauth_envelope.prepare_context(
+            provider_config=None,
+            key_id="provider-key-456",
+            user_api_key_id="user-key-123",
+            is_stream=True,
+        )
+        out_b, _ = codex_oauth_envelope.wrap_request(
+            {"model": "gpt-test", "input": []},
+            model="gpt-test",
+            url_model=None,
+            decrypted_auth_config=None,
+        )
+    finally:
+        set_codex_request_context(None)
+
+    assert out_a["prompt_cache_key"] == out_b["prompt_cache_key"]
+    assert out_a["prompt_cache_key"] == build_stable_codex_prompt_cache_key("user-key-123")
+
+
 def test_codex_passthrough_builder_preserves_real_codex_headers() -> None:
     from src.services.provider.adapters.codex.envelope import codex_oauth_envelope