FA-30781 / HTTP retries / Open access

Stable client operation identity over retries: Reject terminal violates retry transition semantics · case 01

Reject terminal violates retry transition semantics

Verified by executionVariant 1 · 6 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Reject terminal violates retry transition semantics

THE FAILURE

Reject terminal violates retry transition semantics

Unsuccessful approach: The attempted repair changes the faulty site to elif e[0]=='reject': state='ready' but still violates a regression oracle.

Case contract

begin(provided key or None,body) starts a logical operation and advances a local operation serial. Generated key is operation serial; explicit keys including zero remain exact. send(body) first sends only matching snapshotted body. uncertain authorizes a resend; reject is terminal; success is terminal. Retried sends reuse the initial key. Return sent key/body pairs or refusal reason.

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):
    serial=0; key=None; original=None; state='idle'; out=[]
    for e in events:
        if e[0]=='begin':
            serial+=1
            key=serial if e[1] is None else e[1]
            original=e[2]
            state='ready'
        elif e[0]=='send':
            if state not in ('ready','uncertain'): out.append('blocked'); continue
            if e[1]!=original: out.append('body-conflict'); continue
            out.append([key,original])
            state='sent'
        elif e[0]=='uncertain':
            if state=='sent': state='uncertain'
        elif e[0]=='reject': state='uncertain'
        elif e[0]=='success':
            if state=='sent': state='done'
    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',None,N),('send',N),('uncertain',),('send',N),('send',N),('success',),('uncertain',),('send',N)]), [[1,N],[1,N],'blocked','blocked'])
check('2', solve([('begin',0,N),('send',N)]), [[0,N]])
check('3', solve([('begin','customer-key',N),('send',N),('uncertain',),('send',N+1),('send',N)]), [['customer-key',N],'body-conflict',['customer-key',N]])
check('4', solve([('begin',None,N),('send',N),('reject',),('uncertain',),('send',N),('begin',None,N+1),('send',N+1)]), [[1,N],'blocked',[2,N+1]])
check('5', solve([('begin',None,N),('send',N+1),('send',N)]), ['body-conflict',[1,N]])
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	`[[1, 1], [1, 1], 'blocked', 'blocked']`	`[[1, 1], [1, 1], 'blocked', 'blocked']`	Passed
2	`[[0, 1]]`	`[[0, 1]]`	Passed
3	`[['customer-key', 1], 'body-conflict', ['customer-key', 1]]`	`[['customer-key', 1], 'body-conflict', ['customer-key', 1]]`	Passed
4	`[[1, 1], [1, 1], [2, 2]]`	`[[1, 1], 'blocked', [2, 2]]`	Failed
5	`['body-conflict', [1, 1]]`	`['body-conflict', [1, 1]]`	Passed

SHA-256 / 0de2ad4fcbe83ecbdc9bfb7656612e158af4218724439c6837bd1c2947d7014b

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(events):
    serial=0; key=None; original=None; state='idle'; out=[]
    for e in events:
        if e[0]=='begin':
            serial+=1
            key=serial if e[1] is None else e[1]
            original=e[2]
            state='ready'
        elif e[0]=='send':
            if state not in ('ready','uncertain'): out.append('blocked'); continue
            if e[1]!=original: out.append('body-conflict'); continue
            out.append([key,original])
            state='sent'
        elif e[0]=='uncertain':
            if state=='sent': state='uncertain'
        elif e[0]=='reject': state='ready'
        elif e[0]=='success':
            if state=='sent': state='done'
    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',None,N),('send',N),('uncertain',),('send',N),('send',N),('success',),('uncertain',),('send',N)]), [[1,N],[1,N],'blocked','blocked'])
check('2', solve([('begin',0,N),('send',N)]), [[0,N]])
check('3', solve([('begin','customer-key',N),('send',N),('uncertain',),('send',N+1),('send',N)]), [['customer-key',N],'body-conflict',['customer-key',N]])
check('4', solve([('begin',None,N),('send',N),('reject',),('uncertain',),('send',N),('begin',None,N+1),('send',N+1)]), [[1,N],'blocked',[2,N+1]])
check('5', solve([('begin',None,N),('send',N+1),('send',N)]), ['body-conflict',[1,N]])
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	`[[1, 1], [1, 1], 'blocked', 'blocked']`	`[[1, 1], [1, 1], 'blocked', 'blocked']`	Passed
2	`[[0, 1]]`	`[[0, 1]]`	Passed
3	`[['customer-key', 1], 'body-conflict', ['customer-key', 1]]`	`[['customer-key', 1], 'body-conflict', ['customer-key', 1]]`	Passed
4	`[[1, 1], [1, 1], [2, 2]]`	`[[1, 1], 'blocked', [2, 2]]`	Failed
5	`['body-conflict', [1, 1]]`	`['body-conflict', [1, 1]]`	Passed

SHA-256 / b6b54ba4c1d57dcb68f9d05bce9d1891d36240a9eca437a7df3b070c7657a116

HELD IN THE MEMBER ARCHIVE

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

This mechanism has 6 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.

Member access is invitation-based. Sign in with your invited account to inspect the repair.

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 2026-09-29T14:41:56.111686+00:00.

Case digest / f03c844b6ce5b7e109c2ff352dae6cf2cfbffc7c95a3b5fc73d4154e53a35813