In software development, “stable” can be a double-edged sword. If you have a HubSpot app running today, that’s a good thing—customers are using it, data is flowing and you may not have touched the code in months. But in a platform ecosystem, stability only holds if the ground beneath it stays the same.
Starting in March 2026, the HubSpot Developer Platform enters a more predictable phase. With the release of Projects 2026.03, we’re formalizing a cadence we’ll follow going forward: new platform versions every six months, each supported for 18 months.
That predictability is a win for developers, but it also means every app eventually reaches a decision point. For many teams, that point is arriving.
Three platform milestones are landing. Each is tied to that release cadence and each affects a different class of apps. Understanding which ones apply to you will tell you when you need to act and what kind of work to plan for.
The 2026 Timeline: Three Dates to Know
Rather than one sweeping change, 2026 brings a series of updates. Each has a clear scope and a corresponding source of truth.
March 2026: Serverless Support on the New Platform
With the release of Projects 2026.03, serverless functions will be supported on the new developer platform.
If you’ve been holding off on migration because your app depends on serverless functions, this release removes that blocker. Staying on Projects 2025.1 can be a valid, temporary strategy but only if serverless support is the thing preventing your move.
June 1, 2026: Projects 2025.1 Deprecation
On June 1, Projects version 2025.1 reaches the end of support. Apps still running on that version must migrate to 2025.2 or later to continue operating.
This deprecation is driven by upstream infrastructure changes, including AWS Lambda’s deprecation of Node.js v20. If your app is on 2025.1 today, you'll need to migrate to keep running.
October 31, 2026: Legacy CRM Cards Sunset
On October 31, support for the legacy CRM card framework ends. Apps that rely on classic, static CRM cards will no longer render in the HubSpot UI after this date.
React-based App Cards replace the old framework, enabling richer, interactive experiences that are consistent with the rest of the modern HubSpot UI.
Decision Framework: Which Path Are You On?
This table maps the most common starting points to a recommended path:
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If your app is currently |
How to check |
Recommended action |
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A legacy app (no Projects) |
No hsproject.json file |
Start evaluating now. Decide whether to migrate the existing app or rebuild on the new platform. |
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Projects 2025.1 (no serverless) |
platformVersion: "2025.1" in hsproject.json |
Plan migration to 2025.2+ before June 1, 2026. |
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Projects 2025.1 (uses serverless) |
/src/app/functions directory exists |
Plan migration efforts once Projects version 2026.03 is available starting March 20, 2026 and before June 1, 2026 |
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|
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You’re current and supported until March 2027. Continue monitoring platform updates. |
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Plan to either migrate or replace with App Cards before October 31, 2026. |
What You Gain with the Developer Platform
Migrating to the modern HubSpot Developer Platform isn’t just about avoiding deprecations, it’s about upgrading the foundation your app is built on. You unlock the following and so much more:
Modern UI Extensions
Build React-based App Cards, App Home experiences, and settings pages that live natively inside HubSpot and replace static UI with interactive workflows.
AI-Ready Capabilities
Access Agent Tools for Breeze and MCP server support for IDE copilots, making it easier to build AI-assisted experiences on top of your app.
Improved Developer Experience
Faster builds, clearer error messages, and a more streamlined CLI.
Predictable Lifecycle
Six-month releases and 18-month support windows make platform changes easier to plan for rather than react to.
How to Get Started
This post is meant to answer when and why to migrate. For the execution steps, we’ve put together a centralized onboarding guide that walks through the process based on your starting point.
Start with the step-by-step migration guide
Stay Updated
The HubSpot Developer Platform now follows a regular release schedule. Deprecations, new capabilities, and version availability are all communicated through the changelog. If you maintain an app, subscribing is the simplest way to make migration planning routine instead of reactive.
Subscribe to the Developer Changelog