Every plan, including the free one, comes with Inkwell-hosted AI: skills, the Dramaturg, inline edit, and ghost text all work without a key. Plans differ in two ways — how much you can run each month, and which models you can choose.
The allowance
Skill runs are counted per month, ghost-text completions and inline edits per day. The limits for every plan are on Plans and quotas; Settings → Plan & usage shows how much of this period's allowance you have used.
Model choice
Paid plans unlock the more capable models for skills and chat; the model picker in a skill's options, and in the Chat tab on Ask, lists what your plan can use. The free plan runs the standard model. Which model a plan offers is on the pricing page.
Your own key
With your own Anthropic or OpenAI key, the model list is the provider's list, and runs draw on your provider account rather than the Inkwell allowance. See Bring your own key.
Running out
When the month's skill allowance is used up, a run stops before it starts and the Skills tab says so, with the options: wait for the reset, add credits, or use your own key. See Credits and overage.