How large is the smallest ordinal larger than any “minimal ordinal parameter” for any pair of an Ordinal Turing Machine and a real?

Since there is disputation on how to interpret the problem, I think it would be better to clarify my interpretation:

Let $P(x,alpha)$ be a program, which takes a binary sequence $xin 2^mathbb{N}$ (also called a real, which is standard terminology in set theory) and an ordinal $alpha$. Consider the set $$H = {alphamid text{$alpha$ is the least ordinal such that $P(x,alpha) $ halts for some $x$, $P$} }.$$ Then $H$ is a set. What is the value of $sup H$?

If I understand your problem correctly, then the answer is $omega_1$. Please feel free to comment if there is an error in my proof.

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For the lower bound, we will find an OTM-program with a parameter $xin 2^mathbb{N}$ that computes a countable ordinal. Assume that $x$ codes a well-order over $omega$ whose order-type is $alpha$. Consider the following procedure: decode $x$ and enumerate ordinals less than the order-type of $x$ by brute force. (This is possible since there are only countably many members in $x$ and we have infinite time.) In this way, we can compute $alpha$ from $x$. Now take $P(beta)$ as follows: if $beta=alpha$, it halts. If not, it does not halt.

For the upper bound, assume that we have a program $P$ of real parameter $x$. By Lemma 2.6 of Koepke's Ordinal Computability, the ordinal computation by $P$ is absolute between $V$ and $L[x]$. Assume that $P$ halts with an input $alpha_0$, and $alpha_0$ is the smallest such an ordinal. Moreover assume that we take time $theta$ to compute $P(alpha_0)$.

Now consider the Skolem hull $M$ of sufficiently large $L_gamma[x]$ generated by ${theta,alpha_0,x}$. By condensation, there is an isomorphism $pi:Mto L_beta[x]$ for some countable $beta$. Then $L_beta[x]$ thinks $P$ halts with an input $pi(alpha_0)$ and does not halt if we plug in ordinals smaller than $pi(alpha_0)$. By $pi(alpha_0)le alpha_0$, Lemma 2.6 of Koepke and minimality of $alpha_0$, we have $pi(alpha_0)=alpha_0$. Hence $alpha_0$ is countable.