| Line Item | Jun 30, 2026 | Mar 31, 2026 | Dec 31, 2025 | Sep 30, 2025 | Jun 30, 2025 | Mar 31, 2025 |
|---|---|---|---|---|---|---|
| Operating expenses: | ||||||
| Research and development, net (includes $10 and $140 for the three months ended June 30, 2026 and 2025, respectively; and $10 and $165 for the six months ended June 30, 2026 and 2025, respectively, of related party research and development reimbursement) | — | — | — | |||
| Selling, general and administrative (includes $65 and $44 for the three months ended June 30, 2026 and 2025, respectively; and $153 and $88 for the six months ended June 30, 2026 and 2025, respectively, of related party expenses) | — | — | — | |||
| Total operating expenses | — | — | — | |||
| Loss from operations | ||||||
| Other income (expense), net: | ||||||
| Financing costs related to issuance of convertible promissory notes | — | — | — | |||
| Change in fair value of convertible promissory notes | — | — | — | — | ||
| Change in fair value of warrant liabilities for Series B-1 and Series D redeemable convertible preferred stock | — | — | — | — | ||
| Other income, net | — | — | — | |||
| Total other income (expenses), net | ||||||
| Loss before income taxes | — | — | — | |||
| Income tax expense | — | — | — | |||
| Net loss | ||||||
| Net loss attributable to common stockholders - basic | — | — | — | |||
| Net loss attributed to common stockholders - diluted | — | — | — | |||
| Net loss per share attributable to common stockholders – basic (in usd per share) | — | |||||
| Net loss per share attributable to common stockholders – diluted (in usd per share) | — |