diff --git a/internal/translator/codex/openai/responses/codex_openai-responses_request.go b/internal/translator/codex/openai/responses/codex_openai-responses_request.go
index f0407149..1161c515 100644
--- a/internal/translator/codex/openai/responses/codex_openai-responses_request.go
+++ b/internal/translator/codex/openai/responses/codex_openai-responses_request.go
@@ -26,6 +26,8 @@ func ConvertOpenAIResponsesRequestToCodex(modelName string, inputRawJSON []byte,
 	rawJSON, _ = sjson.DeleteBytes(rawJSON, "temperature")
 	rawJSON, _ = sjson.DeleteBytes(rawJSON, "top_p")
 	rawJSON, _ = sjson.DeleteBytes(rawJSON, "service_tier")
+	rawJSON, _ = sjson.DeleteBytes(rawJSON, "truncation")
+	rawJSON = applyResponsesCompactionCompatibility(rawJSON)
 
 	// Delete the user field as it is not supported by the Codex upstream.
 	rawJSON, _ = sjson.DeleteBytes(rawJSON, "user")
@@ -36,6 +38,23 @@ func ConvertOpenAIResponsesRequestToCodex(modelName string, inputRawJSON []byte,
 	return rawJSON
 }
 
+// applyResponsesCompactionCompatibility handles OpenAI Responses context_management.compaction
+// for Codex upstream compatibility.
+//
+// Codex /responses currently rejects context_management with:
+// {"detail":"Unsupported parameter: context_management"}.
+//
+// Compatibility strategy:
+// 1) Remove context_management before forwarding to Codex upstream.
+func applyResponsesCompactionCompatibility(rawJSON []byte) []byte {
+	if !gjson.GetBytes(rawJSON, "context_management").Exists() {
+		return rawJSON
+	}
+
+	rawJSON, _ = sjson.DeleteBytes(rawJSON, "context_management")
+	return rawJSON
+}
+
 // convertSystemRoleToDeveloper traverses the input array and converts any message items
 // with role "system" to role "developer". This is necessary because Codex API does not
 // accept "system" role in the input array.
diff --git a/internal/translator/codex/openai/responses/codex_openai-responses_request_test.go b/internal/translator/codex/openai/responses/codex_openai-responses_request_test.go
index 4f562486..65732c3f 100644
--- a/internal/translator/codex/openai/responses/codex_openai-responses_request_test.go
+++ b/internal/translator/codex/openai/responses/codex_openai-responses_request_test.go
@@ -280,3 +280,41 @@ func TestUserFieldDeletion(t *testing.T) {
 		t.Errorf("user field should be deleted, but it was found with value: %s", userField.Raw)
 	}
 }
+
+func TestContextManagementCompactionCompatibility(t *testing.T) {
+	inputJSON := []byte(`{
+		"model": "gpt-5.2",
+		"context_management": [
+			{
+				"type": "compaction",
+				"compact_threshold": 12000
+			}
+		],
+		"input": [{"role":"user","content":"hello"}]
+	}`)
+
+	output := ConvertOpenAIResponsesRequestToCodex("gpt-5.2", inputJSON, false)
+	outputStr := string(output)
+
+	if gjson.Get(outputStr, "context_management").Exists() {
+		t.Fatalf("context_management should be removed for Codex compatibility")
+	}
+	if gjson.Get(outputStr, "truncation").Exists() {
+		t.Fatalf("truncation should be removed for Codex compatibility")
+	}
+}
+
+func TestTruncationRemovedForCodexCompatibility(t *testing.T) {
+	inputJSON := []byte(`{
+		"model": "gpt-5.2",
+		"truncation": "disabled",
+		"input": [{"role":"user","content":"hello"}]
+	}`)
+
+	output := ConvertOpenAIResponsesRequestToCodex("gpt-5.2", inputJSON, false)
+	outputStr := string(output)
+
+	if gjson.Get(outputStr, "truncation").Exists() {
+		t.Fatalf("truncation should be removed for Codex compatibility")
+	}
+}