1) Direct Answer
You are right. I gave you incompatible code and then gave a wrong assessment before checking it tightly against the actual DO.py contract.

2) What I got wrong

I changed DD.py behavior without preserving the output/exit semantics DO.py expects.
I answered from inference instead of revalidating against the exact source you had already provided.
I gave conflicting guidance about whether DD had to restart from the beginning because I conflated rsync changes with DD changes.

3) Specific failures

DD.py returned early/fatally in ways DO.py was not built to tolerate.
I did not preserve the original parse_fixed()/Done processed: ... fixed:... style contract.
I answered “don’t guess” situations with analysis that was not grounded enough in the actual files already in context.

4) Corrective summary
The right approach is:

preserve DO.py compatibility exactly,
preserve DD.py output format exactly unless DO.py is updated too,
only then add optimizations like inode short-circuit and safer relink behavior.

5) Action Plan
I should now produce a full DD.py that is explicitly backward-compatible with your existing DO.py output parsing and invocation model, instead of introducing a new contract.