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CONVERTIBLE REDEEMABLE PREFERRED SHARES - Preferred shares activity (Details) ¥ in Thousands, $ in Thousands |  |  |  |  | 12 Months Ended
--- | --- | --- | --- | --- | ---
Jul. 20, 2023 CNY (¥) shares | May 14, 2021 CNY (¥) shares | Feb. 22, 2021 CNY (¥) shares | Dec. 25, 2020 CNY (¥) shares | Dec. 31, 2025 CNY (¥) shares | Dec. 31, 2025 USD ($) shares | Dec. 31, 2024 CNY (¥) shares | Dec. 31, 2023 CNY (¥) shares
Increase (Decrease) in Temporary Equity [Roll Forward] |  |  |  |  |  |  |  |
Balance at the beginning |  |  |  |  | ¥ 933,780 |  | ¥ 871,780 | ¥ 352,373
Accretion of convertible redeemable preferred shares to redemption value |  |  |  |  | 20,082 | $ 2,872 | 62,000 | 43,330
Conversion of redeemable preferred shares into ordinary shares upon IPO, value |  |  |  |  | (953,862) |  |  |
Balance at the end |  |  |  |  |  |  | 933,780 | 871,780
Series A preferred stock |  |  |  |  |  |  |  |
Increase (Decrease) in Temporary Equity [Roll Forward] |  |  |  |  |  |  |  |
Balance at the beginning |  |  |  |  | ¥ 231,944 |  | ¥ 212,421 | ¥ 194,589
Balance at the beginning (in shares) | shares |  |  |  |  | 34,833,028 | 34,833,028 | 34,833,028 | 34,833,028
Accretion of convertible redeemable preferred shares to redemption value |  |  |  |  | ¥ 6,268 |  | ¥ 19,523 | ¥ 17,832
Issuance of Preferred Shares, net of issuance cost |  |  | ¥ 5,000 | ¥ 160,000 |  |  |  |
Issuance of Preferred Shares, net of issuance cost (in shares) | shares |  |  | 1,055,546 | 33,777,482 |  |  |  |
Conversion of redeemable preferred shares into ordinary shares upon IPO, value |  |  |  |  | ¥ (238,212) |  |  |
Conversion of redeemable preferred shares into ordinary shares upon IPO (in shares) | shares |  |  |  |  | (34,833,028) | (34,833,028) |  |
Balance at the end |  |  |  |  |  |  | ¥ 231,944 | ¥ 212,421
Balance at the end (in shares) | shares |  |  |  |  | 0 | 0 | 34,833,028 | 34,833,028
Series B preferred stock |  |  |  |  |  |  |  |
Increase (Decrease) in Temporary Equity [Roll Forward] |  |  |  |  |  |  |  |
Balance at the beginning |  |  |  |  | ¥ 234,715 |  | ¥ 213,608 | ¥ 157,784
Balance at the beginning (in shares) | shares |  |  |  |  | 14,914,404 | 14,914,404 | 14,914,404 | 12,256,755
Accretion of convertible redeemable preferred shares to redemption value |  |  |  |  | ¥ 6,717 |  | ¥ 21,107 | ¥ 16,652
Issuance of Preferred Shares, net of issuance cost |  | ¥ 140,000 |  |  |  |  |  | ¥ 39,172
Issuance of Preferred Shares, net of issuance cost (in shares) | shares |  | 12,256,755 |  |  |  |  |  | 2,657,649
Conversion of redeemable preferred shares into ordinary shares upon IPO, value |  |  |  |  | ¥ (241,432) |  |  |
Conversion of redeemable preferred shares into ordinary shares upon IPO (in shares) | shares |  |  |  |  | (14,914,404) | (14,914,404) |  |
Balance at the end |  |  |  |  |  |  | ¥ 234,715 | ¥ 213,608
Balance at the end (in shares) | shares |  |  |  |  | 0 | 0 | 14,914,404 | 14,914,404
Series B+ Preferred Shares |  |  |  |  |  |  |  |
Increase (Decrease) in Temporary Equity [Roll Forward] |  |  |  |  |  |  |  |
Balance at the beginning |  |  |  |  | ¥ 467,121 |  | ¥ 445,751 |
Balance at the beginning (in shares) | shares |  |  |  |  | 20,374,577 | 20,374,577 | 20,374,577 |
Accretion of convertible redeemable preferred shares to redemption value |  |  |  |  | ¥ 7,097 |  | ¥ 21,370 | ¥ 8,846
Issuance of Preferred Shares, net of issuance cost | ¥ 209,902 |  |  |  |  |  |  | ¥ 436,905
Issuance of Preferred Shares, net of issuance cost (in shares) | shares | 12,780,417 |  |  |  |  |  |  | 20,374,577
Conversion of redeemable preferred shares into ordinary shares upon IPO, value |  |  |  |  | ¥ (474,218) |  |  |
Conversion of redeemable preferred shares into ordinary shares upon IPO (in shares) | shares |  |  |  |  | (20,374,577) | (20,374,577) |  |
Balance at the end |  |  |  |  |  |  | ¥ 467,121 | ¥ 445,751
Balance at the end (in shares) | shares |  |  |  |  | 0 | 0 | 20,374,577 | 20,374,577
Class A Ordinary shares |  |  |  |  |  |  |  |
Increase (Decrease) in Temporary Equity [Roll Forward] |  |  |  |  |  |  |  |
Exchange of ordinary shares for preferred shares (in shares) | shares |  |  |  |  |  |  |  | 1,046,761
Class A Ordinary shares | Junjie Zhang, Xianggui Peng And Peibang Gong (Employees) |  |  |  |  |  |  |  |
Increase (Decrease) in Temporary Equity [Roll Forward] |  |  |  |  |  |  |  |
Exchange of ordinary shares for preferred shares (in shares) | shares |  |  |  |  |  |  |  | 1,046,761
Class B Ordinary shares |  |  |  |  |  |  |  |
Increase (Decrease) in Temporary Equity [Roll Forward] |  |  |  |  |  |  |  |
Exchange of ordinary shares for preferred shares (in shares) | shares |  |  |  |  |  |  |  | 1,610,888
Class B Ordinary shares | Junjie Zhang, Xianggui Peng And Peibang Gong (Employees) |  |  |  |  |  |  |  |
Increase (Decrease) in Temporary Equity [Roll Forward] |  |  |  |  |  |  |  |
Exchange of ordinary shares for preferred shares (in shares) | shares |  |  |  |  |  |  |  | 1,610,888

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