{"abstract":"The circuit probe operation is admitted even though a probe runs before the open-state cooldown elapses.","category":"Reliability","checks":9,"contract":"Return a Boolean admission decision for allow a half-open circuit probe. The record r must satisfy all of: r['open_delay'][0]-r['open_delay'][1] >= r['open_delay'][2]; r['probe_exclusive'] == 0; r['circuit_generation'][0] == r['circuit_generation'][1]; r['endpoint_health'][0] in r['endpoint_health'][1]; r['caller_deadline'][0] < r['caller_deadline'][1]. Extra tracing fields are ignored; validation does not mutate the record.","evaluation_group":"xd-circuit-probe","failed_approach":"Adding the open delay check repairs the reported defect, but replacing the adjacent probe exclusive check loses that independent invariant.","family":"xd-circuit-probe-open_delay","id":"FA-951","implementations":{"attempt":{"sha256":"d09f4821eb5a07023c43379d36a25e71e67e096f1bc2fb38003869e355de0173","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (r['open_delay'][0]-r['open_delay'][1] >= r['open_delay'][2]) and (r['circuit_generation'][0] == r['circuit_generation'][1]) and (r['endpoint_health'][0] in r['endpoint_health'][1]) and (r['caller_deadline'][0] < r['caller_deadline'][1])\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'open_delay': [10, 5, 5], 'probe_exclusive': 0, 'circuit_generation': [4, 4], 'endpoint_health': ['a', ['a', 'b']], 'caller_deadline': [10, 11]}\ncheck('valid operation', solve(r), True)\ncheck('A probe runs before the open-state cooldown elapses', solve(dict(r, **{'open_delay': [9, 5, 5]})), False)\ncheck('Concurrent requests occupy the single half-open probe slot', solve(dict(r, **{'probe_exclusive': 1})), False)\ncheck('A stale timer probes a newly opened circuit generation', solve(dict(r, **{'circuit_generation': [3, 4]})), False)\ncheck('A probe targets an endpoint removed from service discovery', solve(dict(r, **{'endpoint_health': ['c', ['a', 'b']]})), False)\ncheck('A probe is started for an already expired caller', solve(dict(r, **{'caller_deadline': [11, 11]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'open_delay': [9, 5, 5], 'probe_exclusive': 1, 'circuit_generation': [3, 4], 'endpoint_health': ['c', ['a', 'b']], 'caller_deadline': [11, 11]}\nkeys = list(invalid)\npair = {keys[N % len(keys)]: invalid[keys[N % len(keys)]], keys[(N+1) % len(keys)]: invalid[keys[(N+1) % len(keys)]]}\ncheck('two independent violations in variant', solve(dict(r, **pair)), False)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"broken":{"sha256":"94022545e652aa1dea763d951cd2351b31c20f7316f2659dcaa0158ebbb89bb0","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (r['probe_exclusive'] == 0) and (r['circuit_generation'][0] == r['circuit_generation'][1]) and (r['endpoint_health'][0] in r['endpoint_health'][1]) and (r['caller_deadline'][0] < r['caller_deadline'][1])\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'open_delay': [10, 5, 5], 'probe_exclusive': 0, 'circuit_generation': [4, 4], 'endpoint_health': ['a', ['a', 'b']], 'caller_deadline': [10, 11]}\ncheck('valid operation', solve(r), True)\ncheck('A probe runs before the open-state cooldown elapses', solve(dict(r, **{'open_delay': [9, 5, 5]})), False)\ncheck('Concurrent requests occupy the single half-open probe slot', solve(dict(r, **{'probe_exclusive': 1})), False)\ncheck('A stale timer probes a newly opened circuit generation', solve(dict(r, **{'circuit_generation': [3, 4]})), False)\ncheck('A probe targets an endpoint removed from service discovery', solve(dict(r, **{'endpoint_health': ['c', ['a', 'b']]})), False)\ncheck('A probe is started for an already expired caller', solve(dict(r, **{'caller_deadline': [11, 11]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'open_delay': [9, 5, 5], 'probe_exclusive': 1, 'circuit_generation': [3, 4], 'endpoint_health': ['c', ['a', 'b']], 'caller_deadline': [11, 11]}\nkeys = list(invalid)\npair = {keys[N % len(keys)]: invalid[keys[N % len(keys)]], keys[(N+1) % len(keys)]: invalid[keys[(N+1) % len(keys)]]}\ncheck('two independent violations in variant', solve(dict(r, **pair)), False)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"fixed":{"sha256":"936c8cdc018d6114263a15014556cf16f82fe1578f421c8579bf25e91c34ca87","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(r):\n    return (r['open_delay'][0]-r['open_delay'][1] >= r['open_delay'][2]) and (r['probe_exclusive'] == 0) and (r['circuit_generation'][0] == r['circuit_generation'][1]) and (r['endpoint_health'][0] in r['endpoint_health'][1]) and (r['caller_deadline'][0] < r['caller_deadline'][1])\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nr = {'open_delay': [10, 5, 5], 'probe_exclusive': 0, 'circuit_generation': [4, 4], 'endpoint_health': ['a', ['a', 'b']], 'caller_deadline': [10, 11]}\ncheck('valid operation', solve(r), True)\ncheck('A probe runs before the open-state cooldown elapses', solve(dict(r, **{'open_delay': [9, 5, 5]})), False)\ncheck('Concurrent requests occupy the single half-open probe slot', solve(dict(r, **{'probe_exclusive': 1})), False)\ncheck('A stale timer probes a newly opened circuit generation', solve(dict(r, **{'circuit_generation': [3, 4]})), False)\ncheck('A probe targets an endpoint removed from service discovery', solve(dict(r, **{'endpoint_health': ['c', ['a', 'b']]})), False)\ncheck('A probe is started for an already expired caller', solve(dict(r, **{'caller_deadline': [11, 11]})), False)\ncheck('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)\ncheck('repeat validation is pure', solve(r), True)\ninvalid = {'open_delay': [9, 5, 5], 'probe_exclusive': 1, 'circuit_generation': [3, 4], 'endpoint_health': ['c', ['a', 'b']], 'caller_deadline': [11, 11]}\nkeys = list(invalid)\npair = {keys[N % len(keys)]: invalid[keys[N % len(keys)]], keys[(N+1) % len(keys)]: invalid[keys[(N+1) % len(keys)]]}\ncheck('two independent violations in variant', solve(dict(r, **pair)), False)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"}},"limitations":" This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.","method":"Deterministic executable model with adversarial boundary fixtures.","provenance":{"created_by":"Failure Map","dependencies":"Python standard library","family":"xd-circuit-probe-open_delay","generated_at":"2026-09-29T14:36:57.235145+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A deterministic local contract for reliability. Each negative fixture violates exactly one invariant. No transport timing, persistence, cryptographic verification, or full protocol implementation is claimed.","repair":"Require r['open_delay'][0]-r['open_delay'][1] >= r['open_delay'][2] together with every other stated precondition before accepting the operation.","root_cause":"The admission path omits the open delay invariant while validating the other operation preconditions.","sha256":"648367291dd38eeec9db319f933e530444ccae623cd33be0f90bb7c62d3ec1d1","title":"Allow a half-open circuit probe: A probe runs before the open-state cooldown elapses · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":30.468,"exit_code":1,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"A probe runs before the open-state cooldown elapses","expected":false,"passed":true},{"actual":true,"check":"Concurrent requests occupy the single half-open probe slot","expected":false,"passed":false},{"actual":false,"check":"A stale timer probes a newly opened circuit generation","expected":false,"passed":true},{"actual":false,"check":"A probe targets an endpoint removed from service discovery","expected":false,"passed":true},{"actual":false,"check":"A probe is started for an already expired caller","expected":false,"passed":true},{"actual":true,"check":"unrelated tracing metadata","expected":true,"passed":true},{"actual":true,"check":"repeat validation is pure","expected":true,"passed":true},{"actual":false,"check":"two independent violations in variant","expected":false,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"valid operation\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"A probe runs before the open-state cooldown elapses\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Concurrent requests occupy the single half-open probe slot\", \"actual\": true, \"expected\": false, \"passed\": false}, {\"check\": \"A stale timer probes a newly opened circuit generation\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A probe targets an endpoint removed from service discovery\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A probe is started for an already expired caller\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"unrelated tracing metadata\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"repeat validation is pure\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"two independent violations in variant\", \"actual\": false, \"expected\": false, \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":100.382,"exit_code":1,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":true,"check":"A probe runs before the open-state cooldown elapses","expected":false,"passed":false},{"actual":false,"check":"Concurrent requests occupy the single half-open probe slot","expected":false,"passed":true},{"actual":false,"check":"A stale timer probes a newly opened circuit generation","expected":false,"passed":true},{"actual":false,"check":"A probe targets an endpoint removed from service discovery","expected":false,"passed":true},{"actual":false,"check":"A probe is started for an already expired caller","expected":false,"passed":true},{"actual":true,"check":"unrelated tracing metadata","expected":true,"passed":true},{"actual":true,"check":"repeat validation is pure","expected":true,"passed":true},{"actual":false,"check":"two independent violations in variant","expected":false,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"valid operation\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"A probe runs before the open-state cooldown elapses\", \"actual\": true, \"expected\": false, \"passed\": false}, {\"check\": \"Concurrent requests occupy the single half-open probe slot\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A stale timer probes a newly opened circuit generation\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A probe targets an endpoint removed from service discovery\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A probe is started for an already expired caller\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"unrelated tracing metadata\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"repeat validation is pure\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"two independent violations in variant\", \"actual\": false, \"expected\": false, \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":30.479,"exit_code":0,"observations":[{"actual":true,"check":"valid operation","expected":true,"passed":true},{"actual":false,"check":"A probe runs before the open-state cooldown elapses","expected":false,"passed":true},{"actual":false,"check":"Concurrent requests occupy the single half-open probe slot","expected":false,"passed":true},{"actual":false,"check":"A stale timer probes a newly opened circuit generation","expected":false,"passed":true},{"actual":false,"check":"A probe targets an endpoint removed from service discovery","expected":false,"passed":true},{"actual":false,"check":"A probe is started for an already expired caller","expected":false,"passed":true},{"actual":true,"check":"unrelated tracing metadata","expected":true,"passed":true},{"actual":true,"check":"repeat validation is pure","expected":true,"passed":true},{"actual":false,"check":"two independent violations in variant","expected":false,"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"valid operation\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"A probe runs before the open-state cooldown elapses\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"Concurrent requests occupy the single half-open probe slot\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A stale timer probes a newly opened circuit generation\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A probe targets an endpoint removed from service discovery\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"A probe is started for an already expired caller\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"unrelated tracing metadata\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"repeat validation is pure\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"two independent violations in variant\", \"actual\": false, \"expected\": false, \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}