# Sphere vs a coding harness on its own

A **coding harness** is an AI coding agent and the tooling that drives it: chat-in-editor assistants, CLI coding agents and similar tools. They are very good at writing and editing code. Sphere uses them; it doesn't compete with them.

## The short answer

A coding harness answers *"write this code"*. Sphere answers *"deliver this change to my system, correctly, and remember it"*.

Many harnesses look “autonomous” because they loop on edits. Sphere’s autonomy is different: it continues through **plan → build → verify → fix** against a **persistent architecture model**, with people at goal/plan approval and result review — not at every re-prompt.

## Side by side

| | Coding harness alone | Sphere (with coding agents) |
|---|---|---|
| **Autonomy** | Writes/edits code in a session | Delivers a checked change across the system model |
| **Context** | Current session: open files, a prompt, maybe rules | A persistent model of the whole system (Architecture as Code) |
| **Scope** | Usually one repository or one task | Changes that span several components and repositories |
| **Planning** | Implicit, inside the conversation | Explicit plan with acceptance criteria, approved before building |
| **Verification** | Left to the developer, or ad hoc | Built into every plan; failures diagnosed and fixed in a loop |
| **Who supervises** | A person steering and checking each step | People approve goal and plan and review the checked result |
| **Memory** | Mostly lost between sessions | Plans, runs and verification kept with the system model |
| **Collaboration** | Primarily developers in an IDE | Control plane for BA, Dev, Architect, and QA |
| **Status** | "Done" when the agent says so | "Done" when the checks pass |

## ROI: compare equal outcomes

Do not claim a magic savings percentage. Use a fair comparison:

For the **same target platform / same production-ready outcome**, look at:

- **Tokens / AI capacity** consumed to get there
- **Production-ready scope** actually delivered (Y)
- **Human interactions** required (Z): re-prompting, re-pasting context, chasing failed builds, translating between roles

A coding harness alone often burns more Z because context and verification sit on people. Sphere lowers Z by anchoring agents in the living blueprint and folding verify/fix into the loop. Exact X/Y/Z numbers come from a **scoped pilot** on your system — not from invented benchmarks. See `roi-and-evaluation.md`.

## Why that matters

Less supervision, fewer surprises across components, trustworthy status, knowledge that compounds, and you keep the coding agents you like.

## When a coding harness alone is enough

For small, self-contained edits in one place, a coding assistant alone is often the right tool. Sphere earns its place when changes are larger, cross boundaries, need verification, need multi-role collaboration, or need to be understood later by someone else.

Do not criticise named competitor products — compare approaches.