What if your partner already suspects you are going to propose?
Keep the plan if it still suits you both. Suspicion does not remove the meaning of your words or the experience you have prepared. Avoid manufacturing distress or changing everything merely to make the proposal harder to predict.
Should you deny it if they ask?
You can keep details private without making elaborate false claims. Say that you have planned something thoughtful or would like to keep part of the outing a surprise. Use an approach consistent with how you normally communicate.
What can remain unexpected?
Your specific words, a personal letter, the setting, or a small celebration can still be new. You do not need to add more spectacle. Anticipation can be enjoyable when both people know the commitment is wanted.
When should you adjust the plan?
Change it if their reaction reveals a genuine preference you missed, such as discomfort with public attention. Do not change it simply because they guessed the date. A good plan should fit your partner, not test their ability to detect clues.
What are people discussing on Reddit?
These related discussions inspired the topic. The answer above is original Proposal Tips guidance, not a quotation or a claim that Reddit users all agree.
A ring-size question leads to discussion of direct communication and keeping the date a surprise.
A discussion about planning decisions people would make differently.