# Tier 4 QA returns a compressed 20-50 token fix — never a full stack trace, never a multi-paragraph diagnosis

## The compression contract

A Tier 4 (Utility / QA) agent:

- Receives only the raw error output (a stack trace or a linter warning) and a 20-line block of the offending code.
- Returns a single compressed string (20-50 tokens) describing the fix.
- Wakes up, translates the error, and immediately dies — no persistent memory across calls.

Per `docs/MMA_Support/Tier4_Utility.md:6-7`: "Tier 4 acts as the financial firewall. It solves the expensive problem of feeding massive (e.g., 3,000-token) stack traces back into a mid-tier LLM's context window."

Per `docs/MMA_Support/Tier4_Utility.md:17`: the output is "a surgical, highly compressed string (20-50 tokens) passed back into the Tier 3 Contributor's working memory (e.g., 'Syntax Error on line 42: You missed a closing parenthesis. Add `]`')."

## Why

Massive stack traces (1,000-3,000 tokens of `stderr`) explode the mid-tier model's context window for very little signal. A cheap model can compress the same trace into one sentence that points the worker at the line + the fix.

## What this means in practice

- Tier 4 invocation prompts explicitly say "respond in <= 50 tokens" or "one sentence fix."
- Tier 4 does not return the raw trace, the full file context, or a multi-paragraph diagnosis — only the fix.
- Tier 4's full output is logged to `comms.log` for debugging but only the compressed fix enters the worker's working memory.