Two live gate attempts failed with "An error occurred downloading the FUT
Squad Update" while the redirect response was verified byte-identical to the
Python oracle. Rolling back to the Python redirector fixed it, so the response
bytes were never the whole contract.
Log archaeology found the discriminator: the client polls
/fifa17/fut/rosterupdate.xml ~4x/min in every successful FUT session, and the
only gap in 300 recorded fetches is 03:47-03:58 -- exactly the two
Rust-redirector sessions. The Blaze RPC sequence over those sessions is
identical (msgNum 0-53), so the divergence is entirely outside Blaze.
A differential lifecycle probe against both redirectors found the two
behaviours this host never reproduced:
* the oracle drains the request body per Content-Length; this host stopped
at the header terminator, leaving unread data in the receive queue, which
makes Linux close with RST rather than FIN
* the oracle holds the connection open ~300ms before closing
(time.sleep(0.3)); this host closed at 0ms
Both are now reproduced. The dwell is a named constant, ORACLE_CLOSE_DWELL,
overridable only so the causal experiment -- set it to 0, confirm the failure
returns -- can be run without a rebuild.
The suite could not have caught either: it sent Content-Length: 0, so there
was never a body to drain. It now POSTs a body, and asserts a split-write body
is fully consumed.
Testing the drain via client-visible symptoms does NOT work -- verified by
mutation: with the drain removed the client still reads the buffered response
and sees close_notify before any reset. So the host records a per-connection
ConnOutcome and the test asserts on that. Both mutations (no-dwell, no-drain)
are now each caught by exactly one test.
This does not yet prove causation for the FUT Squad Update failure; it removes
the only two measured divergences. Gate 6 is the test.
funman300
e2c4ca6d56