Cover - shares	3 Months Ended
	Mar. 31, 2026	Apr. 24, 2026
Cover [Abstract]
Document Type	10-Q/A
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2026
Document Transition Report	false
Entity File Number	001-36177
Registrant Name	Crescent Biopharma, Inc.
Entity Incorporation, State or Country Code	E9
Entity Tax Identification Number	06-1686563
Entity Address, Address Line One	300 Fifth Avenue
Entity Address, City or Town	Waltham
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02451
City Area Code	617
Local Phone Number	430-5595
Title of 12(b) Security	Ordinary Shares, $0.001 par value per share
Trading Symbol	CBIO
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		27,571,935
Entity Central Index Key	0001253689
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	Q1
Amendment Flag	true
Document Fiscal Year Focus	2026
Amendment Description	Crescent Biopharma, Inc. (the “Company”) is filing this Amendment No. 1 on Form 10-Q/A (this “Amendment”) to its Quarterly Report on Form 10-Q for the quarterly period ended March 31, 2026, which was originally filed with the Securities and Exchange Commission (the “SEC”) on April 29, 2026 (the “Original Filing”). This Amendment is being filed to revise Part II “Item 5. Other Information” by adding disclosure regarding Rule 10b5-1 trading arrangements (as defined in Item 408(a) of Regulation S-K), which was inadvertently omitted from the Original Filing.In addition, as required by Rule 12b-15 of the Securities and Exchange Act of 1934, as amended (the “Exchange Act”), new certifications by the Company’s principal executive officer and principal financial officer are filed herewith as exhibits to this Amendment, under Part II, Item 6 hereof, pursuant to Rule 13a-14(a) or 15d-14(a) of the Exchange Act. Because no financial statements have been included in this Amendment and this Amendment does not contain or amend any disclosure with respect to Items 307 and 308 of Regulation S-K, paragraphs 3, 4 and 5 of the certifications have been omitted. The Company is also not including new certifications under Section 1350 of Chapter 63 of Title 18 of the United States Code (18 U.S.C. 1350) (Section 906 of the Sarbanes-Oxley Act of 2002), as no financial statements are being filed with this Amendment.Other than as expressly set forth herein, this Amendment does not, and does not purport to, amend, update or restate the information in the Original Filing or reflect any events that have occurred after the date the Original Filing was made. Information not affected by this Amendment remains unchanged and reflects the disclosures made at the time as of which the Original Filing was made. No changes have been made to the financial statements of the Company as contained in the Original Filing. Accordingly, this Amendment should be read together with the Original Filing and the Company’s other filings with the SEC.