Hey c_hixon - we’ve explored something similar using Intelligent Selection within canvas and it can help with the auto-picking a winner over time requirement since it optimises toward a conversion event.
That said, there are a couple of constraints to be aware of:
- Intelligent Selection supports up to 8 variants in a canvas, so it won’t fully cover a 10-way subject line test in one go
- The standard Experiment Path and Audience Path limits of 4 and 8 variants respectively, still apply, so you can’t natively run a clean 10-way split with auto-winner selection in a single canvas.
One approach that may work for you is to potentially group subject lines into themes (e.g. urgency, curiosity, offer-driven) then use Intelligent Selection across those themes, and let it optimise toward the best-performing group. From there, you can run a follow-up experiment (or a new canvas) to refine within the winning theme.
It’s not a perfect single-pass solution, but it balances scale with automation and still gets you to a strong winning subject line over time
