# Gitnexus Pdg Query

Use when querying or extending GitNexus's PDG control/data-dependence surface (the...

- Repository: https://github.com/abhigyanpatwari/GitNexus (48173 stars)
- Category: AI and agents
- License: see repository
- Last updated: 2026-11-01
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add abhigyanpatwari/GitNexus --skill gitnexus-pdg-query -g -a claude-code -y`
Codex: `npx skills add abhigyanpatwari/GitNexus --skill gitnexus-pdg-query -g -a codex -y`
Cursor: `npx skills add abhigyanpatwari/GitNexus --skill gitnexus-pdg-query -g -a cursor -y`
Gemini CLI: `npx skills add abhigyanpatwari/GitNexus --skill gitnexus-pdg-query -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add abhigyanpatwari/GitNexus`

## Description

Use when querying or extending GitNexus's PDG control/data-dependence surface (the `pdg_query` MCP tool, CDG/REACHING_DEF edges), or reasoning about \"what controls X\" / \"where does Y flow\" / guard clauses. Examples: \"what guards this statement?\", \"trace this variable within the function\", \"why is the pdg_query result empty?\", \"add a CDG query\".

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# PDG query surface with GitNexus

Expert knowledge for the `pdg_query` MCP tool and the control/data-dependence
edges it reads, the opt-in `--pdg` program-dependence layers. Read this before
touching `gitnexus/src/mcp/local/local-backend.ts` (`_pdgQueryImpl`) or the
`pdg_query` tool def, or when explaining a `pdg_query` result.

## When to Use

- "Under what condition does this statement run?" (guarding predicates).
- "Where does this variable flow inside the function?" (def→use).
- Guard-clause discovery (early-return guards, subsumes the #559 heuristic).
- Extending or reviewing `pdg_query` / the CDG / REACHING_DEF read path.
- Debugging an empty or surprising `pdg_query` result.

## The layered substrate (build order)

`pdg_query` runs **on** the same graph taint runs on. Each layer is opt-in
behind `--pdg`; a default `analyze` run records none of them (byte-identical).

```
L1  CFG            per-function basic blocks + control-flow edges   (M1 #2081)
L2  REACHING_DEF   GEN/KILL def→use data dependence (pure solver)   (M2 #2082)
L5  CDG            Ferrante control dependence (post-dominators)    (M5 #2085)
```

All three are `BasicBlock → BasicBlock` edges in the single `CodeRelation` table
(keyed by the `type` property). There is **no** `Function → BasicBlock` edge.

## The two modes

- `pdg_query({ mode: 'controls', target })`, CDG. For the anchored function,
  each edge: controlling predicate block → dependent block + branch sense in
  `reason` (`'T'` = predicate's true/taken arm, `'F'` = false/fall-through). An
  edge into an early-return/throw block is flagged `guard: true`.
- `pdg_query({ mode: 'flows', target, variable? })`, REACHING_DEF def→use
  edges; `variable` filters to one binding.

`target` is **required**, a file path or a symbol/function name (resolved like
`context()`). There is no anchorless mode (see below).

## The corrected guard-clause Cypher

The rest: https://github.com/abhigyanpatwari/GitNexus/blob/HEAD/gitnexus-claude-plugin/skills/gitnexus-pdg-query/SKILL.md