At what point do you pull in the product marketing team while working on a new feature enhancement?

From the very beginning and throughout the development process.

This is very much related to the previous question. I will try to bring to life how the process works on the Square teams.

• For any new feature development, we hold a kickoff/ problem alignment with PM, PMM, Design, Eng and Data Science. The goal is to align on the customer problem, generate hypotheses, identify open questions that need further investigation. From there, PM, PMM, and Design may divide and conquer customer research tasks.
• Once the team is aligned on this is the right problem to solve and the right time, Design and Eng will lead the solution generation. We do weekly design check-ins where PMMs are invited to follow how the team is progressing.
• Solution design is finalized and now the Eng team is heads-down executing. At this point, the PMM is well aware of the customer problem and the solution space, and they start the go-to-market planning with creative and channel partners.
• You are ready to launch! For bigger features, we will have a pre-launch meeting where we go through beta or testing party results, and the PMM shares the go-to-market plan. For smaller ones, the PMM populates the GTM section in the PRD.

As early as possible! I pull in product marketing as soon I have a good understanding of the problem statement and its benefits to customers. Typically the artifact we'll share at this point is a draft of a PR/FAQ. If you're not familiar with this term, it's a practice taken from Amazon, where they start feature or product development by authoring a strawman press release (PR) that a customer could conceivably read and understand the value proposition of the product.

Having PMM's eyes on this early ensures that PMs aren't too inward-facing or talking about too much technical mumbo-jumbo that obscures the nature of the problem. Plus, it gives PMM a good sense of the assets they'll need to update or create in order to support the feature when it gets released.

The FAQ portion of the document is something we'll add to as development progresses. But it's important to get PMM's feedback on the PR portion as soon as practical.