FA-29346 / HTTP retries / Open access

Replay source snapshot: Retry rewinds into a prefix preceding the request body · case 01

Retry rewinds into a prefix preceding the request body

Verified by executionVariant 1 · 7 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Retry rewinds into a prefix preceding the request body

THE FAILURE

Retry rewinds into a prefix preceding the request body

Unsuccessful approach: The attempted repair changes the faulty site to origin = max(0,e[2]-1) but still violates a regression oracle.

Case contract

Events open(list of integer bytes, starting index), mutate(index,byte), read(count), retry, close. Opening freezes bytes and origin. Reads advance within the frozen representation. Retry rewinds to origin. Reads after close return closed; retry after close returns closed. Output read chunks or status markers.

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):
    body = (); live = []; origin = 0; pos = 0; closed = True; out = []
    for e in events:
        if e[0] == 'open':
            live = list(e[1])
            body = tuple(live)
            origin = 0
            pos = origin
            closed = False
        elif e[0] == 'mutate':
            live[e[1]] = e[2]
        elif e[0] == 'close':
            closed = True
        elif e[0] == 'read':
            if closed:
                out.append('closed')
                continue
            chunk = list(body[pos:pos+e[1]])
            pos += len(chunk)
            out.append(chunk)
        elif e[0] == 'retry':
            if closed:
                out.append('closed')
                continue
            pos = origin
            out.append('rewound')
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('0', solve([]), [])
check('1', solve([('open',[N,N+1,N+2],1),('read',1),('retry',),('read',2)]), [[N+1],'rewound',[N+1,N+2]])
check('2', solve([('open',[N,N+1,N+2],0),('read',2),('read',1),('read',1)]), [[N,N+1],[N+2],[]])
check('3', solve([('open',[N,N+1],0),('mutate',0,99),('retry',),('read',2)]), ['rewound',[N,N+1]])
check('4', solve([('open',[],0),('read',0),('retry',),('read',1)]), [[],'rewound',[]])
check('5', solve([('open',[N,N+1],0),('close',),('read',1),('retry',)]), ['closed','closed'])
check('6', solve([('open',[N],0),('read',1),('close',),('read',1),('retry',),('open',[N+2],0),('read',1)]), [[N],'closed','closed',[N+2]])
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], 'rewound', [1, 2]]`	`[[2], 'rewound', [2, 3]]`	Failed
2	`[[1, 2], [3], []]`	`[[1, 2], [3], []]`	Passed
3	`['rewound', [1, 2]]`	`['rewound', [1, 2]]`	Passed
4	`[[], 'rewound', []]`	`[[], 'rewound', []]`	Passed
5	`['closed', 'closed']`	`['closed', 'closed']`	Passed
6	`[[1], 'closed', 'closed', [3]]`	`[[1], 'closed', 'closed', [3]]`	Passed

SHA-256 / d8e88f7a89a39e56836fccf7f797e0371ba8c59af7ef7dc52156608430f2f042

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(events):
    body = (); live = []; origin = 0; pos = 0; closed = True; out = []
    for e in events:
        if e[0] == 'open':
            live = list(e[1])
            body = tuple(live)
            origin = max(0,e[2]-1)
            pos = origin
            closed = False
        elif e[0] == 'mutate':
            live[e[1]] = e[2]
        elif e[0] == 'close':
            closed = True
        elif e[0] == 'read':
            if closed:
                out.append('closed')
                continue
            chunk = list(body[pos:pos+e[1]])
            pos += len(chunk)
            out.append(chunk)
        elif e[0] == 'retry':
            if closed:
                out.append('closed')
                continue
            pos = origin
            out.append('rewound')
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('0', solve([]), [])
check('1', solve([('open',[N,N+1,N+2],1),('read',1),('retry',),('read',2)]), [[N+1],'rewound',[N+1,N+2]])
check('2', solve([('open',[N,N+1,N+2],0),('read',2),('read',1),('read',1)]), [[N,N+1],[N+2],[]])
check('3', solve([('open',[N,N+1],0),('mutate',0,99),('retry',),('read',2)]), ['rewound',[N,N+1]])
check('4', solve([('open',[],0),('read',0),('retry',),('read',1)]), [[],'rewound',[]])
check('5', solve([('open',[N,N+1],0),('close',),('read',1),('retry',)]), ['closed','closed'])
check('6', solve([('open',[N],0),('read',1),('close',),('read',1),('retry',),('open',[N+2],0),('read',1)]), [[N],'closed','closed',[N+2]])
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], 'rewound', [1, 2]]`	`[[2], 'rewound', [2, 3]]`	Failed
2	`[[1, 2], [3], []]`	`[[1, 2], [3], []]`	Passed
3	`['rewound', [1, 2]]`	`['rewound', [1, 2]]`	Passed
4	`[[], 'rewound', []]`	`[[], 'rewound', []]`	Passed
5	`['closed', 'closed']`	`['closed', 'closed']`	Passed
6	`[[1], 'closed', 'closed', [3]]`	`[[1], 'closed', 'closed', [3]]`	Passed

SHA-256 / ef29ac1d870e5a372d0c12ffba169f17f4148b1bcef52a60ce0573a77c61f4f8

HELD IN THE MEMBER ARCHIVE

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

This mechanism has 7 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 2026-09-29T14:41:42.764608+00:00.

Case digest / 90fb8004c8024502318c7a7423dc5be19b0f57f46bea7a61c98f3d13e8cdafd4