When should I start planning items in the sprint for new team members?

When should I start planning items in the sprint for new team members?
Sprint planning for a growing team, digital art (DALL-E)
At what point should I start planning tasks in a sprint for the newcomers on my team? Do you multiply with some coefficient when estimating their capacity?

My approach to this is that new team members can be included in planning as soon as they've completed onboarding and they're comfortable being included, but it's important to communicate expectations clearly with the team. The output from the new members of the team will be lower initially, and that's ok – the team needs to foster an encouraging and supportive environment. Now is a great time to double-down on pair-programming (pun intended).

Team velocity is always evolving. When you introduce new members to a team, you gain capacity long-term – but during engineer onboarding, existing team members will be shifting their focus from delivery to supporting the new recruit.

At the same time, it's unreasonable to expect new members to match the delivery capacity of the current team already familiar with the product and codebase while they ramp up.

A team change signals a new calibration period for velocity, but initially I'll plan for the same capacity as before the change: the additional engineer operating at reduced capacity will effectively cancel out the time spent onboarding them. Over time, velocity should steadily increase as the team stabilises and the new engineers build familiarity and confidence.