FA-30251 / HTTP retries / Open access

Conditional mutation retry reconciliation: Inspection gate violates retry transition semantics · case 01

Inspection gate violates retry transition semantics

Verified by executionVariant 1 · 8 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Inspection gate violates retry transition semantics

VERIFIED REPAIR

Restore the specified transition if state!='uncertain':.

Unsuccessful approach: The attempted repair changes the faulty site to if state=='ready': but still violates a regression oracle.

Case contract

begin(version,desired) creates a pending conditional write. sent records that it may have reached the server; lost means response absent. inspect(version,value) after loss reconciles: desired value at version+1 is committed, unchanged original version permits retry, any other state conflicts. retry only from retry state retains original precondition and desired body. ack(value) succeeds only for an active sent request. Return decisions and outgoing retry preconditions.

Why this case matters

Offline deterministic model of HTTP request retries.

1 / The failure

Exit 1

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

N = 1
observations = []
def solve(events):
    version=0; desired=None; state='idle'; out=[]
    for e in events:
        if e[0]=='begin':
            version=e[1]; desired=e[2]; state='ready'
        elif e[0]=='sent':
            if state=='ready': state='sent'
        elif e[0]=='lost':
            if state=='sent': state='uncertain'
        elif e[0]=='inspect':
            if state=='idle': out.append('ignored'); continue
            if e[1]==version+1 and e[2]==desired:
                state='done'; out.append('committed')
            elif e[1]==version:
                state='retry'; out.append('retryable')
            else: state='conflict'; out.append('conflict')
        elif e[0]=='retry':
            if state!='retry': out.append('denied'); continue
            out.append(['send',version,desired]); state='ready'
        elif e[0]=='ack':
            if state=='sent': state='done'; out.append(['success',e[1]])
            else: out.append('ignored')
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('0', solve([]), [])
check('1', solve([('begin',N,N+9),('sent',),('lost',),('inspect',N,N+1),('retry',),('retry',),('sent',),('ack',N+9)]), ['retryable',['send',N,N+9],'denied',['success',N+9]])
check('2', solve([('begin',N,N+9),('sent',),('lost',),('inspect',N+1,N+9),('retry',),('inspect',N,N)]), ['committed','denied','ignored'])
check('3', solve([('begin',N,N+9),('sent',),('lost',),('inspect',N+1,N+8),('retry',),('inspect',N,N)]), ['conflict','denied','ignored'])
check('4', solve([('begin',N,N+9),('sent',),('lost',),('inspect',N+2,N+9),('retry',)]), ['conflict','denied'])
check('5', solve([('begin',N,N+9),('lost',),('inspect',N,N),('ack',N)]), ['ignored','ignored'])
check('6', solve([('begin',N,N+9),('sent',),('lost',),('ack',N),('inspect',N-1,N),('retry',)]), ['ignored','conflict','denied'])
check('7', solve([('begin',N,N+9),('sent',),('lost',),('inspect',N,N),('retry',),('ack',N)]), ['retryable',['send',N,N+9],'ignored'])
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
0	`[]`	`[]`	Passed
1	`['retryable', ['send', 1, 10], 'denied', ['success', 10]]`	`['retryable', ['send', 1, 10], 'denied', ['success', 10]]`	Passed
2	`['committed', 'denied', 'retryable']`	`['committed', 'denied', 'ignored']`	Failed
3	`['conflict', 'denied', 'retryable']`	`['conflict', 'denied', 'ignored']`	Failed
4	`['conflict', 'denied']`	`['conflict', 'denied']`	Passed
5	`['retryable', 'ignored']`	`['ignored', 'ignored']`	Failed
6	`['ignored', 'conflict', 'denied']`	`['ignored', 'conflict', 'denied']`	Passed
7	`['retryable', ['send', 1, 10], 'ignored']`	`['retryable', ['send', 1, 10], 'ignored']`	Passed

SHA-256 / 4dfe5078c191e96921c1cd854ef454608cd5bed00cc4cd65d9dad65ee9c87c6e

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(events):
    version=0; desired=None; state='idle'; out=[]
    for e in events:
        if e[0]=='begin':
            version=e[1]; desired=e[2]; state='ready'
        elif e[0]=='sent':
            if state=='ready': state='sent'
        elif e[0]=='lost':
            if state=='sent': state='uncertain'
        elif e[0]=='inspect':
            if state=='ready': out.append('ignored'); continue
            if e[1]==version+1 and e[2]==desired:
                state='done'; out.append('committed')
            elif e[1]==version:
                state='retry'; out.append('retryable')
            else: state='conflict'; out.append('conflict')
        elif e[0]=='retry':
            if state!='retry': out.append('denied'); continue
            out.append(['send',version,desired]); state='ready'
        elif e[0]=='ack':
            if state=='sent': state='done'; out.append(['success',e[1]])
            else: out.append('ignored')
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('0', solve([]), [])
check('1', solve([('begin',N,N+9),('sent',),('lost',),('inspect',N,N+1),('retry',),('retry',),('sent',),('ack',N+9)]), ['retryable',['send',N,N+9],'denied',['success',N+9]])
check('2', solve([('begin',N,N+9),('sent',),('lost',),('inspect',N+1,N+9),('retry',),('inspect',N,N)]), ['committed','denied','ignored'])
check('3', solve([('begin',N,N+9),('sent',),('lost',),('inspect',N+1,N+8),('retry',),('inspect',N,N)]), ['conflict','denied','ignored'])
check('4', solve([('begin',N,N+9),('sent',),('lost',),('inspect',N+2,N+9),('retry',)]), ['conflict','denied'])
check('5', solve([('begin',N,N+9),('lost',),('inspect',N,N),('ack',N)]), ['ignored','ignored'])
check('6', solve([('begin',N,N+9),('sent',),('lost',),('ack',N),('inspect',N-1,N),('retry',)]), ['ignored','conflict','denied'])
check('7', solve([('begin',N,N+9),('sent',),('lost',),('inspect',N,N),('retry',),('ack',N)]), ['retryable',['send',N,N+9],'ignored'])
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
0	`[]`	`[]`	Passed
1	`['retryable', ['send', 1, 10], 'denied', ['success', 10]]`	`['retryable', ['send', 1, 10], 'denied', ['success', 10]]`	Passed
2	`['committed', 'denied', 'retryable']`	`['committed', 'denied', 'ignored']`	Failed
3	`['conflict', 'denied', 'retryable']`	`['conflict', 'denied', 'ignored']`	Failed
4	`['conflict', 'denied']`	`['conflict', 'denied']`	Passed
5	`['ignored', 'ignored']`	`['ignored', 'ignored']`	Passed
6	`['ignored', 'conflict', 'denied']`	`['ignored', 'conflict', 'denied']`	Passed
7	`['retryable', ['send', 1, 10], 'ignored']`	`['retryable', ['send', 1, 10], 'ignored']`	Passed

SHA-256 / 59c611c16229bcb1edb677ec1ee23fd77763bdb46131a5a4b679d1e59c4e2c7f

3 / The verified repair

Exit 0

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

N = 1
observations = []
def solve(events):
    version=0; desired=None; state='idle'; out=[]
    for e in events:
        if e[0]=='begin':
            version=e[1]; desired=e[2]; state='ready'
        elif e[0]=='sent':
            if state=='ready': state='sent'
        elif e[0]=='lost':
            if state=='sent': state='uncertain'
        elif e[0]=='inspect':
            if state!='uncertain': out.append('ignored'); continue
            if e[1]==version+1 and e[2]==desired:
                state='done'; out.append('committed')
            elif e[1]==version:
                state='retry'; out.append('retryable')
            else: state='conflict'; out.append('conflict')
        elif e[0]=='retry':
            if state!='retry': out.append('denied'); continue
            out.append(['send',version,desired]); state='ready'
        elif e[0]=='ack':
            if state=='sent': state='done'; out.append(['success',e[1]])
            else: out.append('ignored')
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('0', solve([]), [])
check('1', solve([('begin',N,N+9),('sent',),('lost',),('inspect',N,N+1),('retry',),('retry',),('sent',),('ack',N+9)]), ['retryable',['send',N,N+9],'denied',['success',N+9]])
check('2', solve([('begin',N,N+9),('sent',),('lost',),('inspect',N+1,N+9),('retry',),('inspect',N,N)]), ['committed','denied','ignored'])
check('3', solve([('begin',N,N+9),('sent',),('lost',),('inspect',N+1,N+8),('retry',),('inspect',N,N)]), ['conflict','denied','ignored'])
check('4', solve([('begin',N,N+9),('sent',),('lost',),('inspect',N+2,N+9),('retry',)]), ['conflict','denied'])
check('5', solve([('begin',N,N+9),('lost',),('inspect',N,N),('ack',N)]), ['ignored','ignored'])
check('6', solve([('begin',N,N+9),('sent',),('lost',),('ack',N),('inspect',N-1,N),('retry',)]), ['ignored','conflict','denied'])
check('7', solve([('begin',N,N+9),('sent',),('lost',),('inspect',N,N),('retry',),('ack',N)]), ['retryable',['send',N,N+9],'ignored'])
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
0	`[]`	`[]`	Passed
1	`['retryable', ['send', 1, 10], 'denied', ['success', 10]]`	`['retryable', ['send', 1, 10], 'denied', ['success', 10]]`	Passed
2	`['committed', 'denied', 'ignored']`	`['committed', 'denied', 'ignored']`	Passed
3	`['conflict', 'denied', 'ignored']`	`['conflict', 'denied', 'ignored']`	Passed
4	`['conflict', 'denied']`	`['conflict', 'denied']`	Passed
5	`['ignored', 'ignored']`	`['ignored', 'ignored']`	Passed
6	`['ignored', 'conflict', 'denied']`	`['ignored', 'conflict', 'denied']`	Passed
7	`['retryable', ['send', 1, 10], 'ignored']`	`['retryable', ['send', 1, 10], 'ignored']`	Passed

SHA-256 / e4da5bf408a2ab2e3676f3b11d7ca79438c4fd559672f4aad786e2abd9cefe00

Verification & scope

Stipulated bounded simulator, not a complete HTTP implementation or a standards conformance claim. 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 2026-09-29T14:41:51.135630+00:00.

Case digest / 86bc29c21b8fae076105f2fa93838b64965748113807f8633ec3499e22243b30