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v3.25.1

Income taxes - Reconciliation of the differences between PRC statutory income tax rate and the Group's effective income tax rates (Details) | 12 Months Ended
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Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Income Tax Disclosure [Abstract] |  |  |
Computed expected income tax benefit | (25.00%) | (25.00%) | (25.00%)
Effect of preferential tax rate | 7.00% | 4.00% | (17.00%)
Effect of different tax jurisdiction | 4.00% | 2.00% | 2.00%
Change in tax rate | 4.00% | 18.00% | 0.00%
Prior year return-to-provision true up | 0.00% | (2.00%) | 0.00%
Non-deductible expenses and non-taxable income | 1.00% | 4.00% | 40.00%
Research and development expenses additional deduction | (5.00%) | (6.00%) | (5.00%)
Change in valuation allowance | 14.00% | 5.00% | 7.00%
Actual income tax expense | 0.00% | 0.00% | 2.00%

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- Definition Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to changes in the valuation allowance for deferred tax assets. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 231 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482663/740-10-55-231 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 12A -Subparagraph (a)(6) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-12A Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 12 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-12 Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 235 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08(h)(2)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1 + Details
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