Spring 2026 Spotlight

Welcome to the Spring Spotlight special edition of the developer changelog. We've got a lot of exciting updates to go over, including the general availability of date-based versioned APIs and Developer Platform version 2026.03. With these date-based updates comes a more stable release cadence. Both the APIs and Developer Platform project versions will have two major releases a year, in March and September. Additionally, to help you better prepare for these updates, we are also introducing an 18-month support cycle. Learn more about how date-based releases affect the Developer Platform on our developer documentation.

Developer Platform version 2026.03 now in General Availability

On March 30th, 2026, we released the HubSpot Developer Platform version 2026.03 for Projects, marking the first date-based platform version. This release reintroduced serverless functions to the Projects framework, formalizes an 18-month support lifecycle, and lays the groundwork for better alignment between the HubSpot Developer Platform, public APIs, and developer tooling.

If you’re currently building project-based private apps—especially those running on Projects version 2025.1—this release is your primary path to a modern platform with serverless support and predictable upgrade cadence.

What's changing?

Date-based platform version for Projects

Projects now support “platformVersion”: “2026.03” in hsprojects.json.

Each platform version follows a fix lifecycle:

• Current (6 months) - active maintenance, bug and security fixes.
• Supported (12 months) - critical fixes.
• After 18 months, versions become unsupported and are no longer updated; builds on unsupported versions will fail.

Serverless Functions on 2026.03

Platform version 2026.03 reintroduces serverless functions on the new Projects framework:

• Apps can define app functions using the updated *-hsmeta.json format (one function per file) instead of the single serverless.json file used in 2025.1, which was previously blocked from migrating to newer platform versions.

Agent tools on the Developer Platform

On the Developer Platform, you can build agent tools - enhanced custom workflow actions that HubSpot AI agents can call to perform tasks on behalf of users. Tools are implemented using the Developer Projects framework, submitted for review, and then made available to customers via your app listing and Breeze Agents.

Code Sharing for UI Extensions

You can now share code between UI extensions. Previously, if your App Cards, App Home Pages, and Settings pages required the same code types, utilities, and components, you had to copy the code for each instance. This meant that whenever you made updates, you had to revise every copy of that code separately.

New app listing & certification review updates

Staying on supported platform versions is now an expectation for listings and certifications. Marketplace apps that submit for listing/relisting or certification/recertification must run on a supported Developer Platform version (Projects 2025.2+ today, with 2026.03 as the recommended target), and certified apps must use a supported date-based API version. Additional app updates include:

• Classic legacy CRM cards must be migrated to App Cards by October 31, 2026. Effective immediately, legacy CRM cards are no longer permitted for new app listings, certifications, or recertifications. All listed or certified apps must migrate to App Cards or risk having their certifications revoked or delisted.

• Agent tools listing requirements for Marketplace apps. For apps that ship agent tools (like Breeze Agents can call), these tools are treated as a reviewable surface: they are built as enhanced custom workflow actions in a project. Marketplace-listed apps cannot deploy unapproved tools; deploys will fail until the tool passes review for compliance with the agent tool listing requirements.

• App Card Review Program reviews and approves CRM UI extension app cards submitted by Marketplace partners before they go live. Partners submit an intake form that includes their App ID, Build ID, and a video walkthrough, triggering an automated tracking ticket. A TPM reviews the video against four quality categories (security/privacy, performance/reliability, usability/accessibility, and value/functionality). Approval adds the app ID to the distribution list, and partners receive the Marketplace listing next steps.

Additionally, we’ll also be introducing a date-based version for APIs

Platform Projects version 2026.03 follows the same date-based naming convention as the public API date-based version /2026-03, improving clarity and consistency for developers building on HubSpot, without introducing technical dependencies between the platform and API date-based versions.

Key dates and next steps

• March 30th, 2026: Platform Projects version 2026.03 becomes generally available (first date-based platform version).

• August 1st, 2026: Projects version 2025.1 reaches the end of support; builds on 2025.1 will fail, and apps must move to 2025.2 or 2026.03 to stay supported.

• October 31st, 2026: Classic CRM cards sunset; apps must use App Cards on Projects 2025.2 or 2026.03 instead.

To get ready:

• Check your current platform version in the platformVersion field of hsproject.json, and plan your move to 2026.03 if you’re on 2025.1 or earlier.
• Review your UI extensions and migrate any classic CRM cards or legacy settings pages to App Cards, App Pages, and the new setting component model.
• If you build on the Marketplace, confirm your app is on the supported platform + API date-based version and review the App Card and agent tools listing requirements so you’re set up for future certifications and recertifications.

Helpful resources:

• Determine your migration path to 2026.03
• Serverless functions overview
• Agents and tools overview
• Share code between your extensions using npm workspaces
• Create an app card
• API versioning

Reintroducing Expanded Serverless Functions

Serverless Functions (App Functions) are back in the Developer Platform 2026.03. The Developer Platform 2026.03 release restores and expands the capabilities last seen in version 2025.1, aligning them with the unified Projects architecture introduced in 2025.02. A key update is expanded support for UI Extensions across App Settings and App Pages (formerly known as App Homes), including the ability to run and test functions in developer test accounts.

Availability and Access:

• App Functions (private)
• Access: Requires an Enterprise subscription or a free developer test account.
• Usage: Available within App Cards, App Pages, App Settings, and developer test accounts.
• Public Endpoint Functions
• Access: Requires a Content Hub Enterprise subscription.
• Usage: Public HTTP endpoints exposed via function configuration (for webhooks, public APIs, etc.).
• Note: Public endpoints are not available in developer test accounts.

Functions can now run within Developer Test Accounts, enabling safer and more iterative development before production rollout.

How it Works:

• Upgrade to 2026.03: Ensure you are using CLI version 8.3.0 or higher, as the steps may vary based on your current version.

• From 2025.2: Update the platformVersion in your hsproject.json file from “2025.2” to “2026.03”, then run hs project upload.

• From 2023.0. 2023.2, or 2025.1: Run hs project migrate in your project directory and follow the prompts.

• Legacy public apps (non-project-based): Run hs app migrate and follow the prompts.

• Define your functions: Define serverless functions within your project directory, now aligning with the Projects 2025.2+ structure.

• Integrate with UI Extensions: Trigger these functions directly from the frontend code in App Settings and App Pages to handle custom data and enable user interactivity.

• Test in developer accounts: Deploy and validate your functions in a developer test account before deploying to production.

What's changing?

HubSpot offers multiple serverless function solutions depending on your use case:

Key Differences:

• New configuration format: Uses -hsmeta.json files (e.g., myFunction-hsmeta.json) instead of a single serverless.json file. Each function has its own configuration file, improving validation and IDE support.

• Unified component model: Functions use the same Project schema as the other app components, making configuration more consistent across your app.

• Expanded UI Extension support: App Functions can be invoked from App Cards, App Pages, and App Settings, enabling richer in-app experiences powered by serverless logic.

• Simplified migration from 2025.2: If you’re already on 2025.2, moving to 2026.03 is primarily a version bump and reuse of the -hsmeta.json pattern your app already uses.

Configuration Examples:

Directory structure

• Before (2025.1):

• After (2026.03):

Configuration Schema

• Before (2025.1):

• After (2026.03):

Functions are now configured and located in a single src/app/functions/ directory. This replaces the previous structure that used nested .functions folders. For complete migration steps, including updates from 2025.1 to 2025.2, please refer to the detailed guides in HubSpot’s Developer Documentation.

The 2026.03 version is now available. Developers can start building apps on 2026.03 or migrate eligible 2025.2, 2025.1, and 2023.3 projects to 2026.03.

Introducing a Modern API infrastructure: Date-based Versioned APIs

The first date-based API version, /2026-03/, is now available. Date-based versioning APIs from /2026-03/ onward use a /YYYY-MM/ format to clearly indicate the year and month they went live.

Why does it matter?

For included APIs, date-based versioning brings clearer expectations around timing of change with consistent windows for updates and support.

• Plan with confidence — breaking changes to supported APIs occur twice a year (March and September), with 18 months of support for each version.
• Reduce maintenance overhead — immutable API versions in /2026-03/ mean your supported APIs won't lead your integration to break unexpectedly within an API's support window, and you can migrate to newer versions on your own timeline.
• Navigate APIs more easily — Before, v1, v2, v3, v4 denoted versions of APIs. With date-based versioning, APIs from /2026-03/ onward will use a /YYYY-MM/ format to clearly indicate the year and month they went live.

How does it work?

Each version moves through three stages: Current (actively maintained, first 6 months), Supported (critical fixes to maintain stability and security, months 6–18), and Unsupported (no further updates after 18 months). Please note, HubSpot teams will continue to release enhancements via Public Betas throughout the year.

You can see which APIs are included in date-based versioning /2026-03/ here and HubSpot’s release schedule here.

Updates to the Webhooks Journal API

This release introduces several new capabilities to the Webhooks Journal API, including batched reads for higher-throughput journal processing, CRM object filtering on subscriptions to reduce event noise, list membership subscriptions for real-time list-change tracking, and a snapshot status polling endpoint to monitor asynchronous snapshot processing.

Webhooks Journal CRM Object Filtering (New)

The Webhooks Journal API now supports CRM-style object filtering on subscriptions, letting you define filter criteria (similar to CRM Search filters) that are evaluated against each journal event. Only events whose CRM object data matches your filters are written to the journal for that subscription.

This change reduces noise, bandwidth, and processing. It’s a push-based alternative to polling CRM APIs with the same filters, keeping your event selection logic centralized in subscription definitions rather than scattered across custom polling code.

Subscription Type for List Membership (New)

LIST_MEMBERSHIP subscriptionType lets your app receive your journal events whenever records enter or leave HubSpot lists, rather than polling the Lists API or inferring membership from property changes.

Webhooks v4 Batched Reads with Journal API (New)

The Webhooks Journal API now supports batched reads, allowing integrators to pull multiple journal entries in a single API call, significantly improving throughput for high-volume event streams and reducing per-entry request overhead.

Previously, the Webhooks Journal API required stepping through entries sequentially, meaning integrators had to make an API call for each journal entry URL and use a single “reader” process to advance the offset, which became a bottleneck at scale.

With this update, the Webhooks Journal API now lets you request multiple journal entries at once. Preserving the journal’s chronological, offset-based model while reducing the number of network round-trips required to stay caught up with event volume.

Batch Endpoints:

• Batch Read by offset: POST /webhooks/v4/journal/batch/read

• Batch Next (range from offset): GET webhooks/v4/journal/batch/{offset}/next/{count}

• Batch Fetch Earliest Entries: GET /webhooks/v4/journal/batch/earliest/{count}

• Batch Fetch Latest Entries: GET /webhooks/v4/journal/batch/latest/{count}

Note: Maximum batch size is 100 entries (journal batch operations), and exceeding the limit returns a 400 Bad Request error.

Snapshot Status Polling Endpoint (New)

You can now check the processing status of CRM object snapshots using a new polling endpoint. You can track whether a snapshot is still being processed, has completed successfully, or has failed. Each snapshot creation response now returns a snapshotStatusId that you can use to poll for updates until the snapshot reaches a terminal state.

Snapshot Endpoints:

• Create Snapshots: POST /webhooks/v4/snapshots/crm

• Check Snapshot Status: GET /webhooks/v4/snapshots/status/{statusId}

Note: 404’s are expected after creation. Status records are created asynchronously. This does not mean the snapshot failed - retry with backoff. Additionally, use an exponential backoff. Start at 1 second, cap at 30 seconds, and enforce a max polling direction (e.g., 10 minutes or 20 attempts) to avoid infinite loops.

For additional details on how to use the API, please refer to the developer documentation.

HubSpot MCP Server (remote) and Developer MCP Server (local) now in General Availability

The HubSpot MCP server (remote) is now generally available, enabling connecting agentic tools to your HubSpot account, and it includes expanded access. The HubSpot MCP server now has read-only access to campaigns, landing pages, website pages, blog posts. The HubSpot MCP server also has write access to certain CRM objects, including Contacts, Companies, Deals, Tickets, Line items, Products, Engagements: Calls, Engagements: Meetings, Engagements: Notes, Engagements: Tasks, and Engagements: Emails, meaning you can make updates to your CRM data through natural language.

Developers can use the HubSpot MCP server with AI APIs to build custom agentic workflows that leverage HubSpot data by building MCP auth apps. Learn more in the documentation.

The Developer MCP server (local) is also generally available, giving you the power to create HubSpot apps using natural language. You can download it through the HubSpot CLI and start chatting with it in your preferred AI-powered code editor, like Claude Code or Cursor. Run the command hs mcp setup to get started. You must be on the HubSpot CLI version 8.2.0 or higher to use the Developer MCP server. To check which version of the HubSpot CLI you're using, you can run the command hs --version.

The Developer MCP server has access to tools such as searching the developer documentaiton, creating new projects, and validating code before uploading to your account. See the table below for more info on the tools available:

Expanding App Homes into App Pages, a Multi-page, Custom App Experience

App pages for UI extensions allows you to build custom, full-page experiences for your app directly within HubSpot using React. Starting with a dedicated app home as your app's landing page, app pages expand from there, letting you build as many additional pages as your app needs. Powered by UI extensions, these pages share the same toolkit as app cards and settings pages, allowing for a unified development approach that includes dedicated header actions, multi-page navigation, and seamless data fetching.

This feature fills a critical gap by providing a central home base for your app within HubSpot, eliminating the friction of sending users to external sites for dashboards, documentation, or configurations. App pages empowers developers to build a native-feeling, multi-page experience that improves user retention and gives users a dedicated, organized space for everything from high-level app interactions and reporting to onboarding flows and support resources.

Developers can get started by running hs project add in the CLI and selecting "Pages" to generate the necessary React and configuration files for their app pages. Additional pages can be added alongside it, with built-in PageRoutes and PageLink components handling navigation between them. You can build each interface using standard UI components and the PageHeader wrapper for primary and secondary page actions. Once deployed, users access app pages by clicking the Marketplace icon and selecting your app from "Recently visited apps" or via a direct app URL.

Keep your HubSpot Projects code DRY with code sharing

You can now share code across multiple UI extensions, app cards, settings pages, and app pages, within a single project using npm workspaces. You can create shared packages for utilities, types and components once, then import them into any extension in your project. With shared code, you can fix bugs in a single place, keeping things consistent between all pieces of your projects.

npm workspaces let you define shared packages for utilities, types, components or anything else alongside your extensions within the same project. Each extension can declare those shared packages as dependencies and import from them directly, just like any other package. Shared packages are installed automatically when you run hs project dev or hs project upload, or you can install them manually with hs project install-deps.

Technology Partner Program: Discover Your Tier in the New Dashboard

A new Technology Partner dashboard is now available in the Developer Platform, giving you an in-product view of your status in HubSpot's Technology Partner Program. From one place, you can see your current tier (Partner, Rising, Leading or Premier), what that tier unlocks, high-level requirements to maintain or advance and links to program resources and contacts.

Progress indicators show how close you are to the next tier based on key performance signals, refreshed approximately once per month. Tier badges also appear on your Marketplace app listing page and in Marketplace filters for Rising, Leading and Premier partners.

Learn more about Technology Partner tiers.

Public Betas

Connect the HubSpot MCP Server Securely with MCP Auth Apps

You can now build and manage your own AI connectors to the HubSpot MCP Server using a new self-service MCP Auth Apps tool in the Developer Platform. This update removes the need for general-purpose app tooling; it enables full lifecycle management of MCP connectors, including creation, configuration, and secure OAuth 2.1 credential access, all within a dedicated interface. End-user permissions are now handled automatically, giving customers more control over the data shared through MCP connections. Learn more in the HubSpot MCP Server documentation.

New App Install Governance Tool for Admins

Super Admins now have centralized control over which apps can be installed in their HubSpot account and what data can be shared with them — including controls over AI connectors like the HubSpot connectors for ChatGPT, Claude and Gemini.

With this public beta, admins can approve which apps are allowed, control which users can install each app, customize optional data permissions (such as read-only vs. write access) and revoke approval at any time.

Users who want access to an unapproved app can submit a request directly from within HubSpot for Super Admin review. Manage everything from Settings > Integrations > Connected Apps under the Manage Apps tab. Available across all hubs and tiers.

Learn more about managing app access