Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2023

Fair Value Measurement Inputs and Valuation Techniques [Line Items]

Schedule of Fair Value Hierarchy for Assets and Liabilities Measured at Fair Value at Issuance Date and on Recurring Basis

The following tables present the fair value hierarchy for assets and liabilities that are measured at fair value at issuance date and on a recurring basis and indicate the level within the fair value hierarchy of the valuation techniques the Company utilized to determine such fair value (in thousands):

Fair Value Measurement as of December 31, 2023
	Total Carrying Value		Level 1		Level 2		Level 3
Assets:
Cash equivalents
Money market funds	$	30,582	$	30,582	$	—	$	—
Total assets	$	30,582	$	30,582	$	—	$	—
Liabilities:
Legacy Allurion Common Stock Warrant Liabilities	$	821	$	—	$	—	$	821
Public Warrants		5,943		5,943		—		—
Revenue Interest Financing		36,200		—		—		36,200
PIPE Conversion Option		5,600		—		—		5,600
Earn-out Liability		23,990		—		—		23,990
Term Loan Derivative Liability		1,895		—		—		1,895
Success Fee Derivative Liability		14		—		—		14
Total Liabilities	$	74,463	$	5,943	$	—	$	68,520

Fair Value Measurement as of December 31, 2022
	Total Carrying Value		Level 1		Level 2		Level 3
Assets:
Cash equivalents
Money market funds	$	4,925	$	4,925	$	—	$	—
Total assets	$	4,925	$	4,925	$	—	$	—
Liabilities:
Legacy Allurion Series C Common Stock Warrant Liability	$	340	$	—	$	—	$	340
Legacy Allurion Series B Preferred Stock Warrant Liability		303		—		—		303
Legacy Allurion Series A-1 Preferred Stock Warrant Liability		82		—		—		82
Other Common Stock Warrant Liabilities		255		—		—		255
Legacy Allurion Series C Preferred Stock Warrant Liability		684		—		—		684
Derivative Liability—Success Fee		180		—		—		180
Legacy Allurion Series D-1 Preferred Stock Warrant Liability		707		—		—		707
Total Liabilities	$	2,551	$	—	$	—	$	2,551

Schedule of Assumptions used in Pricing Model

The Company has classified the warrants within Level 3 of the hierarchy as the fair value is derived using the Black-Scholes option pricing model, which uses a combination of observable (Level 2) and unobservable (level 3) inputs. See table below for the assumptions used in the pricing model:

	Measurement Date	Interest Rate	Exercise Price	Estimated Fair Value of Underlying Share Price		Expected Volatility	Expected Life (Years)
Legacy Allurion Series C Preferred Stock warrants (as converted to Common)	December 31, 2023	3.88%	6.73		3.74	100%		7.25
Other Common Stock	December 31, 2023	3.95%	1.05		3.74	100%		3.69
Legacy Allurion Series D-1 Preferred Stock warrants (as converted to Common)	December 31, 2023	3.88%	12.14		3.74	100%	7.25-8.71

	Measurement Date	Interest Rate			Exercise Price		Estimated Fair Value of Underlying Share Price		Expected Volatility			Expected Life (Years)
Legacy Allurion Series A-1 Preferred Stock warrants (as converted to Rollover warrants)	December 31, 2022		4.42	%	$	1.90	$	6.75		69	%		0.25
Legacy Allurion Series B Preferred Stock warrants (as converted to Rollover warrants)	December 31, 2022		4.41	%		2.38		6.91		65	%		2.00
Legacy Allurion Series C Common Stock warrants (as converted to Rollover warrants)	December 31, 2022		4.11	%		0.01		4.54		63	%		4.00
Legacy Allurion Series C Preferred Stock warrants (as converted to Rollover warrants)	December 31, 2022		3.92	%		6.58		7.24		63	%		8.20
Other Common Stock Warrants	December 31, 2022		3.99	%	1.02 -1.10			4.54		63	%	4.6-4.7
Legacy Allurion Series D-1 Preferred Stock warrants (as converted to Rollover warrants)	December 31, 2022	3.88-3.92%				11.87		11.31		63	%	8.2-9.7

Schedule of Changes in Fair Values

The following table reconciles the changes in fair value for the years ended December 31, 2023 and 2022 of the warrant liabilities valued using Level 3 inputs:

	Preferred Stock Warrants (as converted to Common)			Common Stock Warrants			Total
Balance – January 1, 2022	$	510		$	231		$	741
Fair value upon issuance		834			—			834
Change in fair value		456			365			821
Exercise of warrants		(23	)		—			(23	)
Balance – December 31, 2022	$	1,777		$	596		$	2,373
Change in fair value		(720	)		172			(548	)
Exercise of warrants		(75	)		—			(75	)
Derecognition of liability to equity		(340	)		(589	)		(929	)
Balance – December 31, 2023	$	642		$	179		$	821

Schedule of Estimated Fair Value was Measured Using a Monte Carlo Simulation Method

The assumptions used in the Black-Scholes option-pricing model are as follows:

	Year Ended December 31,
	2023			2022
Expected volatility		85.8	%		63	%
Risk-free interest rate		4.5	%		3.56	%
Expected dividend yield		—	%		—	%
Expected term (in years)	5.8				5.8

Public Warrants

Fair Value Measurement Inputs and Valuation Techniques [Line Items]

Schedule of Changes in Fair Values

The changes in the fair values of the Success Fee derivative liability, 2023 Convertible Notes, PubCo Additional Shares liability, Base PubCo Shares and Backstop Shares liability, Revenue Interest Financing, PIPE Conversion Option, Earn-out liability, and Term Loan Derivative Liability categorized with Level 3 inputs for the years ended December 31, 2023 and 2022 were as follows:

	Success Fee Derivative Liability			2023 Convertible Notes			PubCo Share Liability			Base PubCo & Backstop Share Liability			Revenue Interest Financing			PIPE Conversion Derivative		Earn-Out Liability			Term Loan Derivative Liability		Total
Balance – January 1, 2022	$	159		$	—		$	—		$	—		$	—		$	—	$	—		$	—	$	159
Fair value upon issuance		—			—			—			—			—			—		—			—		—
Change in fair value		19			—			—			—			—			—		—			—		19
Exercise of warrants		—			—			—			—			—			—		—			—		—
Balance – December 31, 2022	$	178		$	—		$	—		$	—		$	—		$	—	$	—		$	—	$	178
Fair value upon issuance		—		$	28,700			3,370			3,264			40,000			3,340		53,040			1,895		133,609
Change in fair value		(164	)		3,751			(642	)		10,106			(3,408	)		2,260		(29,050	)		—		(17,147	)
Change in fair value - OCI		—			—			—			—			700			—		—			—		700
Payments		—			(10,750	)		—			—			(1,092	)		—		—			—		(11,842	)
Derecognition of liability to    equity		—			(21,701	)		(2,728	)		(13,370	)		—			—		—			—		(37,799	)
Balance – December 31, 2023	$	14		$	—		$	—		$	—		$	36,200		$	5,600	$	23,990		$	1,895	$	67,699

Earn-Out Liability

Fair Value Measurement Inputs and Valuation Techniques [Line Items]

Schedule of Estimated Fair Value was Measured Using a Monte Carlo Simulation Method

The estimated fair value of the earn-out shares was determined using a Monte Carlo Simulation Method using the following assumptions at the valuation date:

	December 31, 2023
Stock Price	3.74
Risk-free interest rate	3.9%
Expected term (in years)	4.6
Expected volatility	87.0%

Revenue Interest Financing and PIPE Conversion Option

Fair Value Measurement Inputs and Valuation Techniques [Line Items]

Schedule of Estimated Fair Value was Measured Using a Monte Carlo Simulation Method

The fair value of the PIPE Conversion Option was accounted for as a derivative under ASC 815. The instrument is measured using a Monte Carlo Simulation Method using the number of shares convertible of 1,065,341 and the following assumptions:

	December 31, 2023
Stock Price	3.74
Risk-free interest rate	4.46%
Expected term (in years)	1.6
Expected volatility	82.5%