The headwinds remain the same with difficult economic conditions and continued geopolitical tensions. However, we did see renewal rates improving, which is encouraging. Back to Synchro, which is part of Bentley Infrastructure Cloud. As an open, collaborative and data-centric environment, Bentley Infrastructure Cloud is the key to digital project delivery, unlocking digital workflows that help firms increase efficiency and productivity from design through construction and handoff. Our focus in construction is on digital delivery versus a general construction management software. That is leveraging a Digital Twin to sequence and digitally rehearse every step of the construction process. This includes enriching the Digital Twin through that process so that it accurately reflects the as-built asset when handed over into operations.
One reason for this focus is a clear [indiscernible] deliver for users. A recent standout project is EchoWater, a large wastewater treatment facility in California. Engineering firm Project Controls Cubed leveraged Synchro to develop a Digital Twin to manage 22 engineering projects across the facility. Various users from designers to contractors leverage the Digital Twin, working in real time to prepare for and carry out all activities. The Digital Twin streamlined coordination and optimize construction sequencing, reducing overall program cost by an outstanding $400 million. As the Planning Director said, it was an overwhelming success and really prove to everyone the power of Bentley’s digital construction platform. Results like this will further drive the uptake of Bentley Infrastructure Cloud, especially as the silos between design and construction breakdown and engineering and construction teams unite in a collaborative Digital Twin environment.
As users add model-based workflows to their traditional file-based workflows, they will increasingly benefit from digital delivery and gain a competitive advantage in delivering higher quality, sustainable projects. Before I hand over to Werner, I want to thank Bentley colleagues for a strong start to the year. Thanks to their efforts, we are well positioned to take advantage of the many infrastructure opportunities before us in 2024. Over to you Werner.
Werner Andre: Thank you, Nicholas. We are pleased with the strong start to the year, which puts us in a good position to achieve our full year outlook. Total revenues for the first quarter were $338 million, up 7% year-over-year in reported and constant currency. Subscription revenues for the quarter grew 11% year-over-year or 10% in constant currency, in line with our expectations, representing 91% of our total revenues, up from 89% in 23Q1. Our E365 and SMB initiatives continue to be solid contributors to our subscription revenue growth. Perpetual license revenues for the quarter were flat year-over-year or up 1% in constant currency. Perpetual license sales make up only 3% of total revenues and will remain small relative to our recurring revenues.
Our professional services revenues for the quarter declined by $6 million or 22% year-over-year in reported and constant currency driven primarily by weakness in Maximo related work within our digital integrator cohesive. First, 23Q1 was a difficult comparison due to a particularly large Maximo implementation contract in the year ago quarter. And second, during the first quarter of 2024, our Maximo related implementation work was negatively impacted by delays in Maximo version upgrade work with such delays now likely to continue for the second quarter before the pace of upgrade projects is expected to increase early in the second half of the year. An advantage of later upgrades is that we will be better positioned to offer at the same time, the transition from on premise to our hosting managed services for Maximo, facilitating eventual integration with our iTwin environment.
On a positive note, we are pleased that our Bentley software-related services grew modestly as expected. Moving on to our recurring revenue performance. Our last 12 months recurring revenues increased by 11% year-over-year in reported and 10% in constant currency and represent 90% of our total last 12-months revenues. Our last 12-months constant currency account retention rate is up at 99%, and our constant currency recurring revenues, net retention rate was 108%. Our net revenue retention is led by continued accretion within our E365 consumption-based commercial model, ex-China and Russia, our NRR was 109%. We ended Q1 with ARR of $1.186 billion at quarter end spot rates with our E365 and SMB growth initiatives remaining the key growth drivers.
Our constant currency ARR growth rate was 11% year-over-year or 11.5%, excluding China. On a sequential quarterly basis, our constant currency ARR growth rate was 2.2% and was fully in line with our expectations. As I mentioned during last quarter’s call, we expected our ARR growth rate for Q1 to be lower than last year’s sequential 3.1% growth rate for two primary reasons. First, our last programmatic acquisition with appreciable ARR contribution, which was 50 basis points was EasyPower in 23Q1. And second, as Greg slide showed, we have an increasing percentage of our E365 accounts on consumption floors and ceilings, which impacts our quarterly ARR seasonality. With the fourth quarter being our biggest contract renewal quarter, many of these floors and sealants have just reset at the end of Q4.
These resets consider consumption growth expectations over the next year. As such, floor resets can be and often are above the consumption level at the beginning of the renewal period with accounts growing into and above the floors over the renewal term. While our practice is to recognize ARR from E365 consumption and associated growth based on the annualized quarterly consumption, if a consumption floor, which reflects the minimum contract value resets at a higher level than current consumption, we recognize ARR at the new floor level at the time of contract renewal. As such, the higher prevalence of floors and ceilings, tends to align an increasing portion of our E365 consumption growth with the contract renewal timing, which is heavily weighted towards H2 and Q4.
Lastly, we continue to be impacted by ARR headwinds in China and the greater preference there for perpetual licenses. China represents 3% of our ERR. Now moving to profitability performance, our GAAP operating income was $92 million for the first quarter. We have previously explained the impact on our GAAP operating results from amortization of purchased intangibles, deferred compensation plan liability revaluations, and acquisition expenses. Moving on to adjusted operating income with stock-based compensation expense, our primary profitability and margin performance measure. Adjusted operating income with stock-based compensation expense was $112 million for the quarter, up $22 million, 24% year-over-year with a margin of 33.3% up 450 basis points.
During the fourth quarter of 2023, we initiated a strategic realignment program to better align our resources with our strategy, address market opportunities, and to support our growth. Most of the realignment actions were completed at the beginning of 2024. Our first quarter profitability benefited from these run rate savings which we expect to fully reinvest into priority areas throughout the rest of the year. As we previously discussed, our priority investment areas are AI in product development and marketing. As a reminder, we calibrate our business to achieve our annual operating margin improvement objective by investing in long-term initiatives rather than maximizing short-term profitability. I will now briefly comment on our services gross margin.
While our services revenues declined year-over-year by 22% for the reasons we discussed, we pay close attention to our services delivery cost structure to adjust for volatility in episodic services work. The net year-over-year services gross profit impact for the quarter was a decline of only $1 million. Moving back to adjusted operating income with stock-based compensation, our Q1 operating margin is typically a higher margin quarter for us due to OPEX seasonality and I do want to remind you of our seasonal pattern of expenses. We concentrate our annual raises for colleagues to occur as of April 1st of each year. And since approximately 80% of our cost structure is headcount and related support costs, annual raises have a significant impact on our operating expenses in Q2, Q3, and Q4 relative to Q1.
This is further compounded by our larger promotional and event related costs, which are historically highest in the second half of the year. With respect to liquidity, our operating cash flow was $205 million for the quarter, up $29 million or 16% and benefited from the strong profitability of the quarter. For 2024, we continue to expect that our conversion rate of adjusted EBITDA to cash flow from operations will be in the range of 80%. Based on the expected seasonality of collections and expenditures, we expect that 65% to 70% of our cash flow from operations will be generated during the first half of 2024, up from our previous estimate of 55% to 60%. With regards to capital allocation, in the quarter, along with providing sufficiently for our growth initiatives, we deployed $95 million paying down bank debt, and we have now fully paid down our revolving credit facility, $18 million on dividends and $23 million in share repurchases to offset dilution from stock-based compensation.
As of the end of Q1, our net senior debt leverage was 0.1 times and including our 2026 and 2027 convertible notes full year’s debt, our net debt leverage was 3 times. We continued our deleveraging trajectory, delevering 0.5 times adjusted EBITDA in the quarter and 1.7 times adjusted EBITDA since the beginning of 2023. With our strong free cash flow generation profile, we have delevered and increased our balance sheet strength and in April, we have now started to pay down our term loan, while increasing our dividend, continuing sufficient share repurchases to offset dilution from stock-based compensation, and maintaining our programmatic M&A readiness. From a rate exposure perspective, now that we have fully repaid our revolving line of credit, all of our remaining debt is protected from higher rising interest rates through either very low fixed coupon interest in our convertible notes or our $200 million interest rate swap expiring in 2030.
We are very comfortable with our capital structure, in terms of leverage, maturities, and especially interest rate exposure, and we have flexibility to optimize as conditions change. And finally, we remain comfortable with the outlook we provided just over two months ago on our Q4 call. With regards to foreign exchange rates, for the first quarter, the U.S. dollar has weakened slightly relative to the exchange rates assumed in our 2024 annual financial outlook, resulting in less than $1 million of incremental revenues from currency. Based on the most recent rates where the U.S. dollar has strengthened, if end of April exchange rates would prevail throughout the remainder of the year, our Q2 to Q4 GAAP revenues would be negatively impacted by approximately $6 million relative to the exchange rates assumed in our 2024 financial outlook.
