---
title: "Exit 128 in the git broker proof and what else changed before the pass"
canonical: https://dxdev.com/blog/git-broker-e2e-failed-at-step-one/
datePublished: 2026-07-07
---
`git fetch origin -> 128: Host key verification failed.` That was the error from the git broker's end-to-end proof on the night of 7/6.

The broker is server-owned. The agent gets MCP tools named `mcp__gitbroker__git_…`, and the server runs git on its behalf. The proof was a prompt that opened "You are running the end-to-end proof" and told the agent about those tools.

## Three sessions in seven minutes

The evening has three proof sessions, at 10:51 PM, 10:54 PM and 10:57 PM. The first two ran 3 prompts each. The third ran 13 prompts, on an `agent/` proof branch. The pass is logged at 11:20 PM, in the same entry as the fixes to the spawn MCP wiring and the ssh profile.

## Reading the error

Exit 128 is git's generic fatal, so the number says little by itself. The useful part is the message after it. The fix recorded in the log is "SYSTEM ssh profile for broker git": the broker's git now goes through the user's ssh profile instead of SYSTEM's. That is the change the entry ties to this failure.

## The wiring in the same entry

Fixing ssh was not the only change in the 11:20 PM entry. The other was "spawn MCP wiring (per-session broker token)". Each spawned agent session now gets its own broker token in its `--mcp-config`.

We also retired 2 stale pm tests in the same change.

## What else the night produced

Alongside the fixes we filed two follow-ups: one for a LAN bind, one for a metered key sitting in the service environment. The log marks the plan at 6/7 at that point.

The next morning's summary calls the broker "e2e-proven and wired." The pass and the fixes sit in that same 11:20 PM entry, so the word "proven" describes the system after the ssh profile and the per-session token changes, not the system the first proof session ran against. When a pass gets reported, read the log entry it came in and check what else changed alongside it.