Income tax - Uncertain Tax Position (Details) ¥ in Thousands	12 Months Ended
Dec. 31, 2024 CNY (¥)
Income tax
Interest expense related to unrecognized tax benefits	¥ 0
Penalties related to unrecognized tax benefits	¥ 0

Amount of expense for penalties related to a tax position claimed or expected to be claimed in the tax return.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 15
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-15

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration