---
id: "bug-1683"
status: "fixed"
status_updated: "2026-09-24"
status_note: ""
component: "xceadmin"
severity: "unknown"
timestamp: "2026-08-25T00:05:00Z"
last_seen: "2026-09-19T09:00:00Z"
occurrences: 2
files: ["src/xceadmin/src/xcecommon/wire.py"]
tags: ["xceadmin", "xcecommon", "wire-protocol", "python", "framing", "test-failure", "unreproducible"]
related: ["bug-1604"]
legacy: true
---

# bug-1683: xceadmin pytest failure: test_send_frame_writes_exact_known_good_byte_sequence…

## Description
xceadmin pytest failure: test_send_frame_writes_exact_known_good_byte_sequence (src/xceadmin/tests/test_wire.py:200). Test sends a 4-byte payload b'xce!' via wire.send_frame() over a real TLS socket to a raw capture handler that reads exactly 12 bytes (8-byte length header + 4-byte payload) directly off the wire, bypassing this module's own recv_frame() decoder. Expected the captured bytes to be struct.pack('=Q', 4) + b'xce!' (header correctly encodes length=4, followed by the literal payload bytes). Actual captured bytes: the 8-byte header is correct (b'\x04\x00\x00\x00\x00\x00\x00\x00', i.e. length=4 little-endian native uint64_t), but the trailing 4 bytes are all zero (b'\x00\x00\x00\x00') instead of b'xce!' -- the real payload bytes never reached the wire. 1 failed, 266 passed, 3 skipped -- isolated to this one test.

## Environment
_Not recorded (migrated from buglog.json)._

## Reproduction
_Not recorded (migrated from buglog.json)._

## Root cause
UNRESOLVED -- not reproducible. send_frame() (wire.py:102-113) is two sequential sock.sendall() calls (header, then payload) -- nothing in it, or in the test's _TlsEchoServer/_capture_handler harness (test_wire.py), or conftest.py's session-scoped tls_certs fixture, could zero out payload bytes; all reviewed and found correct. Confirmed only bare pytest 8.4.2 is installed (no pytest-xdist, no pytest-randomly, no addopts) -- test order is deterministic, ruling out parallel-worker/reordering interference.

45+ reproduction attempts (2026-08-25), zero failures: isolated run x5, full test_wire.py x3, full 270-test suite x3 (ad-hoc PYTHONPATH), full meson-driven build+test pipeline (xce-build.sh xceadmin, the project's real test-running convention) x1 clean (267 passed, 3 skipped), isolated via the meson-built venv x15, full suite via meson-built venv x5, full suite under artificial CPU stress (20x `yes` spinners, load 11+) x5, 8-way concurrent parallel execution of the exact test x8 -- all clean. TCP/TLS cannot spontaneously zero application bytes mid-stream, so a genuine code defect producing this exact symptom (correct 8-byte header, real zeroed 4-byte payload) should be deterministically reproducible, and it isn't.

## Fix
Not a code fix -- treating as a suspected ONE-OFF ENVIRONMENTAL/INFRASTRUCTURE artifact, not a defect in current source. This project is documented (.wolf/cerebrum.md, bug-1604) to run many concurrent automated sessions that race on shared build directories -- e.g. a concurrent xce-build.sh/meson-build.sh invocation's `rm -rf "$WORK_DIR"` + `cp -r` mirror step, if raced by another concurrent invocation touching the same build dir, is a plausible analogous corruption mechanism (already confirmed for other components under bug-1604's pattern) -- but no direct evidence this happened for bug-1683 specifically, since it has not recurred. No code changes made. If this recurs, capture `ps aux` (or similar) for a concurrent xce-build.sh/meson-build.sh run racing the same build directory at failure time, per the bug-1604 precedent -- that is the most useful missing evidence right now.

## Verification
_Not recorded (migrated from buglog.json)._

## References
- Related: bug-1604