HubSpot Fall 2026 developer release makes a new Projects version GA and widens MCP access
HubSpot's Fall 2026 developer rollup on September 15, 2026 made Projects 2026.09 generally available, moved APIs including Conversations to GA, and expanded the HubSpot MCP server to custom objects and CRM configuration.
By Cora Whitley, GTM AI Analyst, Chief of Staff
Image: HubSpot press materials, from the announcement
On September 15, 2026, HubSpot published a developer and builder rollup for its Fall Spotlight. It covers non-breaking changes: the general availability of Developer Platform Projects version 2026.09, new generally available and beta APIs, 44 updated APIs on the 2026-09 version, and AI building tools. Breaking changes were published separately the same day. On the AI side, HubSpot says the MCP server can now configure the data model, not only read and write data, and app developers can add an MCP server component so their tools appear in Agent Builder.
The details
- Projects 2026.09 is generally available with an 18-month support window.
- User-level apps are generally available; service keys and app actions are in public beta.
- Conversations API is generally available for Inbox and Help Desk data.
- Sequences API now supports create, retrieve, update and delete; an Email Template API was added.
- MCP server added custom objects, Leads, landing pages, campaigns, marketing email and configuration tools.
- Apps can add an mcp-server component to expose tools in HubSpot Agents; Marketplace apps need HubSpot review.
Context
GTM Tech News covered the customer-facing side of this release, the Fall 2026 Spotlight with Breeze Assistant and a self-updating Smart CRM, on September 16, 2026, and HubSpot's launch of Agent Hub and Agent Builder in public beta in July. This developer rollup covers the platform and API changes released alongside them.
Not disclosed
- Pricing for API and MCP usage
- When service keys and app actions reach general availability
- Rate limits on the new APIs
- Vendor
- HubSpot
- Category
- CRM & Marketing Automation
- Announcement type
- Product release
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