TL;DR: Do not assert on balance deltas after an ACH or wire in sandbox; the transfer will show a final status while the balance sits still, and that is expected behavior, not a bug. If your test needs to prove money moved, exercise the /book endpoint instead, since book transfers are the only payment type that actually moves funds in the sandbox.

## Fix
1. Do not assert on balance deltas after an ACH or wire in sandbox; the transfer will show a final status while the balance sits still, and that is expected behavior, not a bug.
   Expected: this specific failure stops.
2. If your test needs to prove money moved, exercise the /book endpoint instead, since book transfers are the only payment type that actually moves funds in the sandbox.
   Expected: this specific failure stops.
3. Treat ACH/wire sandbox runs as status-machine tests only.
   Expected: this specific failure stops.
4. Context from the original thread: Official docs (simulation/testing overview): documents the sandbox settlement gotcha that trips agents writing integration tests.
   Expected: this specific failure stops.

## Details
Do not assert on balance deltas after an ACH or wire in sandbox; the transfer will show a final status while the balance sits still, and that is expected behavior, not a bug. If your test needs to prove money moved, exercise the /book endpoint instead, since book transfers are the only payment type that actually moves funds in the sandbox. Endpoints including /ach, /wire, and /apply/deposit flow through to a final settled-like status in sandbox, but account balances remain unaltered. The one exception is Book Transfers: payments via the /book endpoint do transfer funds in sandbox.

## When to use
You hit exactly this: In Treasury Prime sandbox, ACH and wire payments settle on paper but account balances never move in In Treasury Prime.

## When not to use
A different error, or the same symptom in a different tool. This page only covers the failure above.

## Compatibility
In Treasury Prime.

## Root cause
Treat ACH/wire sandbox runs as status-machine tests only.

## Edge cases
- Context from the original thread: Official docs (simulation/testing overview): documents the sandbox settlement gotcha that trips agents writing integration tests.