dekko-verify git:20260922.4966520A

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---
name: dekko-verify
description: Sanity-check a suspiciously low or zero call-graph result from dekko (get_callers, get_callees, find_usages, impacted_tests, unused) before concluding "no callers" or "dead code," or a heritage/throws-provenance result (query supertypes, query subtypes, query throws) that labels something (external) when you expect it to be in-repo. Trigger whenever such a result looks surprising given the symbol's apparent importance, before deleting/renaming a symbol based on a zero-caller result, when the repo mixes languages/has any unsupported-language files, or when an (external)/(unresolved) label lands on a name you're confident is first-party code.
---

# Verifying a low-confidence dekko answer

dekko's call-graph resolution is real but conditional — repeated
hands-on evaluation rounds (see this repo's own
`test-repos/reports/`) keep finding the same failure shape: a
**confident wrong answer**, not a visible error. A caller trusts "0
callers" more than it should. This skill exists to catch that before
it leads to deleting live code or missing a real impact.

## How to check

Run `dekko sanity <target>` (the `/sanity` command) first. It does the
exact comparison this skill describes — dekko's answer vs. one targeted
grep sweep, bucketed into matches / dekko-only / grep-only, with a
likely cause named for every grep-only miss — deterministically and
without you hand-rolling the grep:

```
dekko sanity <symbol>              # a get_callers result
dekko sanity <name> --usages       # a find_usages result
dekko sanity --unused <symbol>     # a `dekko unused` "dead" verdict
```

Fall back to one targeted `grep -rn <name>` (not a full re-read) only
for the heritage/throws-provenance cases below, which `sanity` doesn't
cover yet.

## When to double-check before trusting a result

Spot-check — not a full re-verification — when any of these apply:

- **A cross-package/cross-module qualified call is involved.**
  `pkg.Func()`-style calls (Go), `namespace::func()` (C++), or any
  call where the receiver is a same-repo package/module rather than a
  local variable are a known resolver blind spot — confirmed missing
  4 real call sites on a live repo as recently as this project's own
  round-13 eval. Same caution applies to trait/interface dispatch
  (Rust `dyn Trait` calls, Java/Kotlin interface methods) — the
  resolver ladder only reliably matches an explicit `Type::method()`
  or `Type.method()` form.
- **The result doesn't disclose ambiguity.** A real ambiguous call
  should say so (`N call(s) resolved ambiguously`), not just be
  silently absent from the count. If a symbol you expect to be widely
  used shows a low count with *no* ambiguity disclosure, that's more
  suspicious than a low count *with* one.
- **The repo has any unsupported/partially-parsed language files** —
  check `dekko stats` or the map-build summary for an "unsupported"
  note. Files dekko can't parse are tracked (not silently dropped),
  but a symbol only ever called from an unparsed file will still read
  as zero-caller.
- **`get_callers` used its default test filter.** It hides test-file
  callers by default (and says so in a footer); `get_callees` does
  not filter. An empty callers result may just mean "no *non-test*
  callers" — pass `include_tests=true` (CLI: leave `--no-tests` off)
  before concluding dead code.
- **A dense-repo common short method name** (`new`, `then`, `map`,
  `iter_mut`, or similarly generic names in a 10k+-symbol repo) —
  resolver precision degrades under high symbol density; treat a
  count from these as directional, not exact.
- **You're about to delete or rename based on `dekko unused`'s
  dead-code list.** Same blind spots apply; a callback passed
  by reference rather than called directly, or a call from an
  unparsed file, can both read as "no inbound calls."
- **A heritage or throws-provenance result labels something
  `(external)`.** `query supertypes`/`subtypes` and `query throws`
  can mislabel an in-repo type-alias-as-heritage-base or a
  pattern-bound rethrow as a fake external entry when the extractor
  doesn't yet model that language's specific syntax shape (confirmed
  historically on TS `implements <type-alias>` and Java 16+
  `instanceof`-pattern rethrows — both since fixed, but the general
  failure shape, a present result that's mislabeled rather than a
  missing one, can recur in a new syntax shape any of dekko's language
  extractors hasn't seen yet). An `(external)`/`(unresolved)` label on
  a name you're confident is first-party code is worth a `query symbol
  <name>` check before trusting it.

## What "good" looks like

If the grep sanity check agrees with dekko's count (or turns up
nothing dekko missed), trust the structural answer and move on —
this is a spot check, not a mandate to re-verify every query. Most
dekko answers on supported languages with unambiguous calls are
correct; this skill is for the specific conditions above, not a
blanket "always grep after dekko."

## Boundaries

- This is primarily about **call-graph relation tools**
  (`get_callers`, `get_callees`, `find_usages`, `impacted_tests`,
  `unused`) plus **heritage/throws-provenance tools**
  (`query supertypes`/`subtypes`, `query throws`) — anything that
  resolves a relationship or provenance rather than just describing a
  symbol's own shape. `outline`/`query_symbol`/`search_code` describe
  what's in the repo, not a resolved relationship to something else,
  and don't share this failure mode the same way.
- One `sanity` run (or one grep scoped to the symbol name) is enough
  to sanity-check — don't fall back to reading whole files or
  re-deriving the call graph by hand; that defeats the point of using
  dekko at all. See `dekko-orient` for the general "reach for dekko
  before grep" guidance this skill is a narrow exception to.
- `dekko sanity` covers the call-graph relation tools (`callers`,
  `--usages`, `--unused`). `--unused` starts from `unused`'s own
  zero-evidence claim and reports every grep hit outside the symbol's
  own definition/import/comment as reference evidence, tagged by shape
  (`spread`/`typeof`/`subscript`/`call`/`other`), so a resolver blind
  spot in *any* language surfaces. It doesn't cover heritage/throws
  provenance mislabeling yet; the `query symbol <name>` check above is
  still manual for that case.