---
name: knowledge-graph
description: >-
  Records and retrieves engineering decisions in the kgai knowledge graph (a small,
  stable graph of domain ELEMENTS — Invoice, Pricing, Checkout… — shaped by an immutable
  log of DECISIONS). INVOKE THIS SKILL AUTOMATICALLY, WITHOUT WAITING TO BE ASKED,
  WHENEVER you make or implement a structural/architectural choice: splitting, merging,
  or moving a module/feature; renaming a domain element (its canonical name changes —
  code-level renames of files/functions don't count); changing a dependency, ownership
  boundary, or how something is exposed/rendered; deprecating or replacing a prior
  decision; or finishing ANY task in which such a choice was made. The skill then
  records it for you (no
  confirmation needed) — capturing the decision is part of completing the task, not
  optional bookkeeping, so do not end your turn with an uncaptured structural decision.
  ALSO invoke it BEFORE a non-trivial change to read prior decisions you must respect,
  and to answer "why is X like this", "how does X relate to Y", "what changed and when".
---

# kgai knowledge graph

`kg` is on your PATH (a shim; the engine lives in `~/.kgai`). Every command prints JSON.

**Mental model.** The live graph is a small set of **Elements** (domain things) joined
by **links** (PART_OF, DEPENDS_ON, RENDERS, …). It is NOT a pile of decision records.
A **Decision** is an immutable event that *mutates* that graph — adds an element, adds
or retires a link, sets a property — and records who/why/when. The chain of decisions
is the **history**; the live graph is always just the current shape.

## 1. READ before you change code

```bash
kg search "how is invoice rendering structured"   # free-text, relevance-ranked — pass a phrase or task description; tolerant to word forms and typos
kg context --about "Invoice"          # the element + its current links + decisions that shaped it
kg context --paths "src/billing/*"    # elements whose `paths` property matches what you're editing
kg history "feature:Invoice"          # full decision chain that shaped one element (the why, over time)
kg as-of 2026-01-01                   # the whole graph at a past date (end of that day; exact, via replay)
kg conflicts --about "Invoice"        # elements with two competing head decisions (unresolved)
```

`kg context` returns, per matched element: its current **links** and its **head
decision(s)** — the ones currently governing it, with rationale (superseded ones live
in `kg history`). If a decision constrains what you're about to do, respect it — or
supersede it with a new decision (§2).

**Matching is lexical (word overlap), not semantic — YOU are the semantic layer.**
The engine matches your words against element names and decision texts
deterministically; it cannot bridge pure synonyms. Before concluding "no record",
rephrase once or twice with the words the team would have used when recording —
domain nouns and decision vocabulary, not your paraphrase. "customer statements" →
try "invoice"; "login state" → try "session", "auth". Union what the variants
return; a hit on any phrasing counts.

If `kg` prints `{"ok":false,...}`, is not installed, or returns no items, **say so
plainly** ("the knowledge graph has no record of this yet") — never invent elements,
links or decisions that the commands didn't return.

## 2. WRITE a decision as graph mutations

When a **structural** choice is made about the domain — split/merge/move a feature,
change a dependency, mark how something is rendered/owned — **record it automatically.
You do NOT need to ask permission first.** At the end of the task, run ONE consolidated
`kg ingest` whose `mutations` reshape the graph, then tell the user in one line what you
recorded (and that they can adjust or retract it). The only gate is the DO/DON'T rules
below — apply them strictly so you capture genuine structural decisions and nothing else.

```bash
kg ingest <<'JSON'
{
  "decision": {
    "title": "Invoice renders standalone, outside Pricing",
    "rationale": "Invoice is its own domain; it must not hang off Pricing",
    "author": "alex",
    "refs": [{"system": "clickup", "url": "https://app.clickup.com/t/CU-1234"}],
    "mutations": [
      {"op": "upsert_element", "kind": "feature", "name": "Invoice", "props": {"paths": "src/billing/invoice/*"}},
      {"op": "upsert_element", "kind": "feature", "name": "Pricing"},
      {"op": "retire_link", "from": "feature:Invoice", "link": "PART_OF", "to": "feature:Pricing"},
      {"op": "set_prop", "element": "feature:Invoice", "key": "display", "value": "standalone"}
    ]
  }
}
JSON
```

**Every decision must attach to at least one element** through its mutations — element-
centric recall (`kg context`, `kg history`) can only surface decisions via their
elements. This holds for dead ends too: record a rejected approach as a decision ON the
element it concerned (a single `upsert_element` is enough). Pick or create the obvious
domain element yourself — never ask the user which element to attach.

Mutation ops (required fields in **bold**):
- `upsert_element` — ensure a node exists: **`kind`** (e.g. `feature`, `business`,
  `service`, `component`, `concept`) + **`name`**. Optional `props` (e.g. `paths` →
  makes `kg context --paths` find it).
- `add_link` / `retire_link` — **`from`**, **`to`** (element refs `kind:name`),
  **`link`** (the relationship kind, e.g. `PART_OF`, `DEPENDS_ON`, `RENDERS`).
- `set_prop` — **`element`**, **`key`**, **`value`**.

How it behaves:
- **Element identity is deterministic** (hash of kind+name, normalized to lowercase +
  collapsed spaces) — reuse the exact same `name` to refer to the same element; two
  people converge on one node, no duplicates. But **diacritics and distinct words still
  fork the node**: `Zürich` ≠ `Zurich`, `Invoice` ≠ `Bill`. Pick one canonical name per
  element and reuse it. Unsure if it exists? `kg resolve "feature:Invoice"` first.
- The decision **automatically supersedes** the previous head decision(s) of every
  element it takes **authority** over → the element's history chains, and concurrent
  edits surface as a conflict (§3). Authority comes from `set_prop`, from
  `upsert_element` that **creates** the element or carries `props`, and from the
  **`from`** side of `add_link`/`retire_link`. A bare `upsert_element` of an element
  that already exists — the dead-end pattern above — and a link's `to` side are
  provenance only: they show in search and history but supersede nothing and can't
  conflict. To take authority over an extra element explicitly, list it in the
  decision's `"supersedes_on": ["kind:name", …]`. You usually don't set supersession
  by hand.
- **Retiring a link removes it from the live graph but never from history** — the
  decision that retired it is permanent, and `kg as-of <date>` reconstructs the old
  shape.
- Several decisions at once: send `{"decisions": [ {...}, {...} ]}`.

### When to record (keep it structural, not noise)
- **DO:** split/merge/move a feature or component; change a dependency or ownership;
  decide how something is rendered/exposed; deprecate/replace a prior structural choice;
  rename a **domain element** (its canonical name in the graph changes). This applies
  to ANY kind of element the team decides about — a feature, a service, a business
  object — not just code.
- **DON'T:** behavior-preserving refactors; code-level renames (files, functions,
  variables) that change no element's name or boundary; formatting; pure implementation
  details with no effect on how elements relate; **analyses, research findings, cost or
  status reports, and recommendations nobody has acted on** — however important. If a
  real choice came out of the analysis, record THE CHOICE (element + mutations + a
  2–3 sentence why), not the analysis itself; volatile figures (prices, counts,
  billing) belong in the report, not in the immutable log. When in doubt, don't.

## 3. Conflicts = two head decisions on one element

If the same element was changed concurrently (e.g. from two sessions), it has two head
decisions — a branch. `kg conflicts` lists them. Resolve by recording one decision that
**takes authority over that element again** (a `set_prop`, an `upsert_element` with
`props`, or a link from it — a bare upsert resolves nothing): it supersedes both heads.
Its mutations should re-express the intended state, with a rationale for the resolution.

## Schema (for `kg query`)
Nodes: `Element(id, kind, name, props)`, `Decision(id, title, rationale, author,
recorded_at, lamport)`. Rels: `LINK(kind, created_by)` Element→Element (current state),
`SHAPES(authority)` Decision→Element (provenance; `authority = true` when the decision
governs that element), `SUPERSEDES` Decision→Decision (evolution). A decision is a
**head** for an element if it SHAPES it with authority and no later authority decision
on that element supersedes it.