> Fetch https://askmiles.ai/llms.txt first: it indexes every public Miles capability. This file is the markdown twin of https://askmiles.ai/docs/trust/stability.

# Stability

What Miles promises not to change on the MCP server and the Chat API, how a breaking change ships when one must, and the one exception on record.

## The rule

Agents on the other side of an MCP connection cannot be redeployed by Miles. So:

- A shipped tool's declared parameters are **never renamed or removed**. A test in Miles' build fails on any field or tool disappearing.
- A breaking change ships as a **new tool name plus a deprecation window** on the old one, never an in-place edit of an existing field.
- A pure addition, a new optional parameter or a new tool, can appear at any time without notice.
- The resource URI `miles://guidance/working-with-miles` and the `points_question` prompt's `question` argument are never renamed either.

## The Chat API

`/v1/chat/completions` follows the OpenAI request and response shapes. Two things are outside that contract and may change with a changelog entry rather than a deprecation window: the `x-miles-quota-*` headers, and the `miles` object on non-streaming responses.

## The one exception on record

On 2026-08-20 the refusal channel changed shape. Every declared parameter schema was untouched, but a refusal (a spent ceiling, a missing scope, a Membership gate) stopped arriving as the tool's ordinary JSON text and started arriving as an `isError` result with a structured code. A caller that detected a refusal by parsing the tool's text got a plain sentence and a parse error instead. It shipped without a deprecation window because the connected population at the time was two users, and it is recorded here rather than hidden so the promise above stays honest.

## Credentials

Every credential Miles mints carries a prefix: `miles_sk_` for a personal key, `miles_at_` and `miles_rt_` for OAuth access and refresh tokens, `miles_ac_` for an authorization code. The prefixes are stable and safe to match on.