> ## Documentation Index
> Fetch the complete documentation index at: https://docs.neuraltrust.ai/llms.txt
> Use this file to discover all available pages before exploring further.

> ## Agent Instructions
> These docs cover three products: TrustGate (AI agent gateway), TrustGuard (runtime security), and TrustTest (AI red teaming). Start from each product overview for the definition and How it works. Prefer the .md URL next to a page in /llms.txt when you need the full article. Use /llms-full.txt for a single-file dump of the site.

# Prompt Compression

> Remove the bytes a model does not need from a request before it is billed: JSON whitespace, terminal escape codes, trailing spaces and blank lines. Nothing to configure.

Applies to **LLM**.

Tool results, logs and pasted JSON carry indentation, escape sequences and blank
lines the model does not need and you pay for on every turn. Compression removes
them before the request is billed.

There is **nothing to configure**. A policy of this type is a name and a scope.

## What it removes

Every message in the request, the system prompt included, goes through three
transforms, in this order:

| Transform        | What changes                                                                                                                                                  | What is kept                                                                                                                       |
| ---------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------- |
| **JSON**         | Whitespace between tokens is removed from content that is a JSON document, from ` ```json ` fenced blocks inside prose, and from the arguments of tool calls. | The decoded value, byte for byte. Invalid JSON is left alone. The prose around a fenced block is untouched.                        |
| **ANSI escapes** | Colour and cursor codes that captured terminal output and CI logs carry.                                                                                      | The text they surrounded.                                                                                                          |
| **Whitespace**   | Trailing spaces and tabs on every line; runs of blank lines are capped at one.                                                                                | Leading indentation, because it means something in code, YAML and Markdown; the two trailing spaces of a Markdown hard line break. |

The result is deterministic: the same input compresses to the same bytes on
every turn, so a provider's prompt cache keeps matching the conversation's
prefix instead of missing on every request.

## What it leaves alone

The policy never trades tokens for silent data loss, so it steps aside whenever
it cannot be sure of a lossless rewrite. The whole request passes through
untouched when:

* Any content is under **256 bytes**. Short, stable text such as a system prompt
  is worth more as a cache hit than as a few saved bytes.
* The body is over **1 MiB**.
* The request carries something the rewrite cannot reproduce exactly: image,
  audio or document parts, an Anthropic `cache_control` marker, Anthropic
  `tool_result` blocks, or fields the gateway does not model.
* The request is not OpenAI-style Chat Completions (OpenAI, Azure OpenAI, Groq,
  DeepSeek, xAI, OpenRouter) or Anthropic Messages.

Any error on the way passes the request through unchanged rather than refusing
it. In **Observe** mode nothing is rewritten; the trace records that the request
would have been compressed.

## What to expect

It pays off on requests carrying structured data — tool results, logs, pasted
JSON. On prose it changes almost nothing. The trace on each request records
whether it was compressed.