The @diagram tool renders architecture, dependency, flow and ER diagrams to PNG, SVG or JPG from Graphviz DOT — with crisp, exactly-correct text, because the labels come from the layout engine, not from pixels a vision model guesses.
Graphviz is embedded: go-graphviz ships the upstream engine compiled to WebAssembly, run on the pure-Go wazero runtime. So there is no cgo, no dot binary to install and no network call — the same self-contained DNA as the embedded TTS/STT and the pure-Go voice notes.
For any node/edge diagram, prefer @diagram over @image. @image produces a raster image and mangles letters; @diagram is deterministic and the names come out 100% correct. SVG is infinitely scalable; PNG with dpi=300 is print-grade.
Usage
<tool_call name="@diagram" args='{"cmd":"render","dot":"digraph{rankdir=LR; cli->agent; cli->llm}","output":"/tmp/arch.png"}' />
<tool_call name="@diagram" args='{"file":"./arch.dot","format":"svg","output":"/tmp/arch.svg"}' />
<tool_call name="@diagram" args='{"cmd":"gomod","root":".","format":"svg","output":"/tmp/imports.svg"}' />
@diagram automatically when you ask for an architecture/dependency diagram as an image — it writes the DOT (models are good at DOT) and renders it here.
There are two subcommands: render (DOT → image) and gomod (real import graph of a Go module → image).
render subcommand
Renders DOT — inline (dot) or from a .dot file (file) — to an image.
Arguments
| Argument | Description | Default |
|---|
dot | Inline Graphviz DOT source. Exactly one of dot | file. | (one of) |
file | Path to a .dot file to render. Exactly one of dot | file. | (one of) |
format | png | svg | jpg | png |
engine | Layout: dot | neato | fdp | sfdp | circo | twopi | osage | patchwork | dot |
dpi | Raster resolution for png/jpg (30–600, clamped) | 150 |
output | Output file path. When omitted, a temp file is written and its path returned. | (temp) |
gomod subcommand
Builds the real import graph of a Go module (via go list -json ./...) and renders it, clustered by top-level directory — a 1:1, code-faithful dependency graph with no manual package enumeration.
Arguments
| Argument | Description | Default |
|---|
root | Module directory to analyze | . |
internalOnly | Only edges between packages of this module (drop third-party deps) | true |
cluster | Group packages into clusters by top-level directory | true |
style | dark | light | plain | dark |
dotOnly | Return the generated DOT source instead of rendering an image | false |
format / engine / dpi / output | Same as render | — |
Use dotOnly: true to get the generated DOT and edit it (colors, grouping, labels) before rendering with render. For focused diagrams, point root at a subdirectory (e.g. ./cli) — the whole-module graph can get very wide.
Output
For render and gomod (without dotOnly), the tool writes the file and returns a summary with path, format, size and — for raster — the dimensions:
Diagram rendered → /tmp/arch.png (PNG, 245.1KB)
dimensions: 1200x800
dotOnly: true, gomod returns the DOT source itself (text), ready to edit or version.
Notes
- Not read-only and not concurrency-safe: the tool writes a file (and
gomod shells out to go list), so it goes through the standard security confirmation and never joins a parallel read-only batch.
- Truly embedded: Graphviz runs as WebAssembly via wazero — nothing to install, works offline on first use, on any OS/architecture.
- Supported engines:
dot (hierarchical, default), neato/fdp/sfdp (force-directed), circo (circular), twopi (radial), osage/patchwork (clusters/treemap).
Combine with @docs-flatten and @context: build a knowledge base of the project and ask for an architecture diagram — the AI uses what it learned to write the DOT and @diagram to render it faithfully. 
