In development · Pre-release

A modelling tool made for practising architects.

Principled. Web-native. Quadrant-native. Built for the work architects actually do — not the enterprise platforms they're given.

ArchiMate 3.1 UML 2.5.1 C4 Model BPMN LLM-native
The approach

Every architectural artefact lives somewhere in the formality–detail quadrant.

Philippe Kruchten observed that architectural representation evolves from informal metaphor to structured formalism, and from sparse sketch to complete specification. Every diagram an architect produces sits somewhere in that two-dimensional space. The trouble is that every existing modelling tool forces a single position.

Informal · High detail
The whiteboard explosion
Rich capture of a design conversation. Many elements, many annotations, no notation discipline.
Excalidraw (with patience)
Formal · High detail
The reference artefact
The HLSD. The full specification. Typed, validated, complete. The thing the repository stores.
Bizzdesign · Sparx · LeanIX
Informal · Low detail
The sketch
Three wobbly boxes in a Tuesday-morning meeting. Communicates an idea in ninety seconds.
Excalidraw · Balsamiq
Formal · Low detail
The overview
Executive summary. Reference architecture overview. Rigorous notation, deliberate sparsity.
PowerPoint (usually)

The enterprise platforms chose formal-detailed as the only legitimate position. The casual diagramming tools made no commitment at all. Balsamiq chose informal-moderate-detail and defended it for fifteen years. Architects work across all four quadrants every week, and currently have to switch tools to move between them — losing their work to redrawing each time.

EOModeller treats formality and detail as first-class properties of every diagram. The same artefact can start as a sketch, grow into a draft, and become a reference — on the same substrate, without being re-authored. Pick the position; the tool's visual rendering and validation behaviour follow from it.

No other modelling tool works this way. Sparx has hand-drawn mode and a whiteboard style, but they are decorative — buried in menus, disconnected from the model's meaning. In EOModeller, the position is the model's stance toward itself.

Positioning

The tool you'd choose — not the one you're given.

The modelling tool market has been captured by enterprise platforms bought over the heads of the people who actually use them. Architects inside those organisations routinely reach for something else.

"Fifteen minutes into the meeting, the architect opened Excalidraw. Three wobbly rectangles, arrows between them, ninety seconds. The organisation pays several hundred thousand dollars a year for an enterprise architecture platform. The architect did not open it."

Observed, Tuesday morning, 2026

This happens every day. It's not a training gap. It's a revealed preference. The imposed platform succeeds at inventory, compliance, and executive reporting — and fails at the architect's actual job: producing artefacts that communicate design with precision under time pressure.

EOModeller closes the gap between the imposed platform and the casual diagramming tool. It opens as fast as Excalidraw. It produces artefacts that survive the meeting. It respects that architects already know what they're doing — and gets out of the way.

It is a tool for individuals. It is priced for individuals. It is deliberately not an enterprise platform, and will not become one.

Capabilities

A modelling substrate, not a checklist of features.

Built from a principled metamodel rather than a union of notations. Every capability below follows from the same underlying structure.

The differentiator
Quadrant-native modelling
Formality and detail as first-class diagram properties. Visual rendering and validation behaviour follow from position. Promotion is a property change, not a redraw.
Metamodel
Three-layer element model
A principled account of element identity, representation, and instance. The same element coheres across views and notations without duplication.
Metamodel
Artefact boundary framework
Explicit boundaries between artefacts. Understand what each model owns, references, and delegates — with semantics that survive across projects.
Notation
Notation-plural
ArchiMate, UML, C4, BPMN, ER, and cloud deployment live inside a single coherent metamodel. Cross-notation references work because the substrate is shared.
History
Snapshot versioning
HEAD plus named baseline snapshots. Not file copies — a genuine versioning model that understands architectural evolution.
Collaboration
Real-time co-editing
Multi-user editing with presence, comments, and review threads. For architecture teams of two to ten — no enterprise SSO scaffolding required.
AI
LLM-native via MCP
Claude and compatible agents produce real model elements, not just Mermaid text. Textual representation that LLMs read and write natively.
Distribution
Confluence integration
Embed live EOModeller diagrams into Confluence pages. Meet architects where their organisation already stores documentation.
Publishing
Living artefacts
Generate views, export to ArchiMate XML, Structurizr DSL, Mermaid, Word documents. Models and documentation stay synchronised by construction.
Standards

Built on the notations you already know.

EOModeller doesn't replace established standards — it implements them faithfully and lets you work across them without friction.

Enterprise
ArchiMate 3.1
Full viewpoint and aspect support — Business, Application, Technology, Motivation, Strategy, Implementation, with cross-layer relationships.
Available
Software
UML 2.5.1
Class, sequence, state, activity, and component diagrams — conformant with the specification, not approximations of it.
Available
Software
C4 Model
Context, Container, and Component levels with Structurizr DSL export. Designed for architects who live alongside code.
Q1 2026
Process
BPMN (subset)
The eighty percent of BPMN architects actually use — events, tasks, gateways, lanes, sequence and message flows. No full-spec-compliance theatre.
Q3 2026
Information
ER / Information
Architect-level ER modelling with entities, attributes, and relationships. Not a replacement for erwin — a companion to it.
Q4 2026
Infrastructure
Cloud deployment
AWS, Azure, and GCP architectural-level deployment modelling. For describing cloud architectures to humans, not generating IaC.
Q2 2026
The companion volume

Models That Matter

Architectural modelling for the modern age.

Jason Swain · 2026
The book

A method alongside the tool.

EOModeller is the implementation of a method. Models That Matter is the explanation of the method — a working architect's account of what principled modelling looks like in 2026, and why most tools and most practice have drifted away from it.

The book and the tool reinforce each other. Neither stands alone. The framework published in the book is what EOModeller implements; the practice EOModeller enables is what the book describes.

Chapter sampler
  1. The work architects actually do
  2. The formality–detail quadrantAvailable now
  3. Three layers of element identity
  4. Artefact boundaries and delegation
  5. Notation pluralism and the principled metamodel
  6. Modelling in the age of AI agents
Early access

Join the pre-release programme.

For practising architects and small teams. No enterprise sales motion. No demos with salespeople. Just the tool, when it's ready.

No marketing. No spam. Unsubscribe any time.