code-understand

1# Code Understand — On-Demand Architecture Focus Map
2 
3You are about to work in a codebase you don't fully know yet. Instead of grepping around or
4reading files at random, ask the local extractor for a **focus map**: the ranked symbols the
5architecture hangs on, each with a `file:line` citation and evidence type. Read only what it
6points at — this is a map, not a substitute for reading the actual code it cites.
7 
8## When to reach for this
9 
10- Before editing an unfamiliar module — see what calls it and what it calls before changing
11  its shape.
12- The user asks "how does X work", "what's the impact of changing Y", "who else uses this
13  function" for a codebase, not the wiki.
14- You're about to do a large refactor and want a ranked list of load-bearing files instead of
15  reading the whole tree.
16- You already have a diff or a set of changed files and want to know their blast radius before
17  finishing the change.
18 
19Not for: summarizing what a project *does* for the wiki (that's `wiki-update` Step 3b, which
20calls this same command as part of a bigger sync flow) — use this skill directly only when you
21need the focus map for your own immediate work, not to persist knowledge.
22 
23## Running it
24 
25```bash
26obsidian-wiki code-understand --project <dir> [--backend auto|builtin|codegraph|graphify] \
27    [--changed <file>...] [--since <sha>] [--max-symbols N] [--pretty]
28```
29 
30- `--project` — defaults to the current directory.
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