FA-986 / Reliability / Open access

Launch a speculative hedged request: Primary and hedge share the same correlated failure domain · case 01

The hedge request operation is admitted even though primary and hedge share the same correlated failure domain.

Verified by executionVariant 1 · 9 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The admission path omits the separate domain invariant while validating the other operation preconditions.

THE FAILURE

The admission path omits the separate domain invariant while validating the other operation preconditions.

Unsuccessful approach: Adding the separate domain check repairs the reported defect, but replacing the adjacent hedge budget check loses that independent invariant.

Case contract

Return a Boolean admission decision for launch a speculative hedged request. The record r must satisfy all of: r['hedge_delay'][0] >= r['hedge_delay'][1]; r['primary_pending'] == 'pending'; r['separate_domain'][0] != r['separate_domain'][1]; r['hedge_budget'][0] < r['hedge_budget'][1]; r['operation_repeatable'] is True. Extra tracing fields are ignored; validation does not mutate the record.

Why this case matters

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.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(r):
    return (r['hedge_delay'][0] >= r['hedge_delay'][1]) and (r['primary_pending'] == 'pending') and (r['hedge_budget'][0] < r['hedge_budget'][1]) and (r['operation_repeatable'] is True)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
r = {'hedge_delay': [5, 5], 'primary_pending': 'pending', 'separate_domain': ['z1', 'z2'], 'hedge_budget': [0, 1], 'operation_repeatable': True}
check('valid operation', solve(r), True)
check('A duplicate request is launched before the hedge delay', solve(dict(r, **{'hedge_delay': [4, 5]})), False)
check('A hedge starts after the primary already completed', solve(dict(r, **{'primary_pending': 'done'})), False)
check('Primary and hedge share the same correlated failure domain', solve(dict(r, **{'separate_domain': ['z1', 'z1']})), False)
check('Speculation consumes more than the allowed duplicate capacity', solve(dict(r, **{'hedge_budget': [1, 1]})), False)
check('A hedge duplicates a non-repeatable side effect', solve(dict(r, **{'operation_repeatable': False})), False)
check('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)
check('repeat validation is pure', solve(r), True)
invalid = {'hedge_delay': [4, 5], 'primary_pending': 'done', 'separate_domain': ['z1', 'z1'], 'hedge_budget': [1, 1], 'operation_repeatable': False}
keys = list(invalid)
pair = {keys[N % len(keys)]: invalid[keys[N % len(keys)]], keys[(N+1) % len(keys)]: invalid[keys[(N+1) % len(keys)]]}
check('two independent violations in variant', solve(dict(r, **pair)), False)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
valid operation	`True`	`True`	Passed
A duplicate request is launched before the hedge delay	`False`	`False`	Passed
A hedge starts after the primary already completed	`False`	`False`	Passed
Primary and hedge share the same correlated failure domain	`True`	`False`	Failed
Speculation consumes more than the allowed duplicate capacity	`False`	`False`	Passed
A hedge duplicates a non-repeatable side effect	`False`	`False`	Passed
unrelated tracing metadata	`True`	`True`	Passed
repeat validation is pure	`True`	`True`	Passed
two independent violations in variant	`False`	`False`	Passed

SHA-256 / cdac50393e14b9de6da4a2ee9f755e3cacabab9be3a0ad24c817dae5432739d9

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(r):
    return (r['hedge_delay'][0] >= r['hedge_delay'][1]) and (r['primary_pending'] == 'pending') and (r['separate_domain'][0] != r['separate_domain'][1]) and (r['operation_repeatable'] is True)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
r = {'hedge_delay': [5, 5], 'primary_pending': 'pending', 'separate_domain': ['z1', 'z2'], 'hedge_budget': [0, 1], 'operation_repeatable': True}
check('valid operation', solve(r), True)
check('A duplicate request is launched before the hedge delay', solve(dict(r, **{'hedge_delay': [4, 5]})), False)
check('A hedge starts after the primary already completed', solve(dict(r, **{'primary_pending': 'done'})), False)
check('Primary and hedge share the same correlated failure domain', solve(dict(r, **{'separate_domain': ['z1', 'z1']})), False)
check('Speculation consumes more than the allowed duplicate capacity', solve(dict(r, **{'hedge_budget': [1, 1]})), False)
check('A hedge duplicates a non-repeatable side effect', solve(dict(r, **{'operation_repeatable': False})), False)
check('unrelated tracing metadata', solve(dict(r, trace='run-'+str(N))), True)
check('repeat validation is pure', solve(r), True)
invalid = {'hedge_delay': [4, 5], 'primary_pending': 'done', 'separate_domain': ['z1', 'z1'], 'hedge_budget': [1, 1], 'operation_repeatable': False}
keys = list(invalid)
pair = {keys[N % len(keys)]: invalid[keys[N % len(keys)]], keys[(N+1) % len(keys)]: invalid[keys[(N+1) % len(keys)]]}
check('two independent violations in variant', solve(dict(r, **pair)), False)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
valid operation	`True`	`True`	Passed
A duplicate request is launched before the hedge delay	`False`	`False`	Passed
A hedge starts after the primary already completed	`False`	`False`	Passed
Primary and hedge share the same correlated failure domain	`False`	`False`	Passed
Speculation consumes more than the allowed duplicate capacity	`True`	`False`	Failed
A hedge duplicates a non-repeatable side effect	`False`	`False`	Passed
unrelated tracing metadata	`True`	`True`	Passed
repeat validation is pure	`True`	`True`	Passed
two independent violations in variant	`False`	`False`	Passed

SHA-256 / ff4a3c57a65d314da580a386be75e88ef1a16ce5d907cc522c2cf860d7b89bb7

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 9 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

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Verification & scope

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.

Observations recorded using Python 3.12.14 at 2026-09-29T14:36:57.886819+00:00.

Case digest / 989c7be59abcbd3ec7d2860fb148345be498383f77ef7fbc3afde68048a3fd8b