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FA-26421 / HTTP ranges / Open access

A range read is rejected if metadata and body revisions diverge · case 01

A range read is rejected if metadata and body revisions diverge.

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

ROOT CAUSE

The representation-pin-revision decision uses return ["ok",body].

VERIFIED REPAIR

Apply the bounded decision exactly: return ["ok",body] if body_revision==header_revision else ["restart",""]

Unsuccessful approach: The partial repair uses return ["ok",body] if body_revision>=header_revision else ["restart",""], which still violates the stated contract.

Case contract

Pinned response plan requires exact revision equality; return [ok,body] or [restart,empty]. Revisions are nonnegative integers.

Why this case matters

Range responses combine representation identity, conditional requests, framing, and partial-object state.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(header_revision, body_revision, body):
    return ["ok",body]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('representation-pin-revision fixture 0', solve(N,N+1,"p"*N), ["restart",""])
check('representation-pin-revision fixture 1', solve(N+1,N,"p"), ["restart",""])
check('representation-pin-revision fixture 2', solve(N,N,"p"*N), ["ok","p"*N])
check('representation-pin-revision fixture 3', solve(0,0,""), ["ok",""])
check('representation-pin-revision fixture 4', solve(0,N,"p"), ["restart",""])
check('representation-pin-revision fixture 5', solve(N,0,"p"), ["restart",""])
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 fixtureActualExpectedOutcome
representation-pin-revision fixture 0['ok', 'p']['restart', '']Failed
representation-pin-revision fixture 1['ok', 'p']['restart', '']Failed
representation-pin-revision fixture 2['ok', 'p']['ok', 'p']Passed
representation-pin-revision fixture 3['ok', '']['ok', '']Passed
representation-pin-revision fixture 4['ok', 'p']['restart', '']Failed
representation-pin-revision fixture 5['ok', 'p']['restart', '']Failed

SHA-256 / 2546579e8bc08a5e33668eeeb124edc63ce05e9bb1110baa40fe28275c3afae6

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(header_revision, body_revision, body):
    return ["ok",body] if body_revision>=header_revision else ["restart",""]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('representation-pin-revision fixture 0', solve(N,N+1,"p"*N), ["restart",""])
check('representation-pin-revision fixture 1', solve(N+1,N,"p"), ["restart",""])
check('representation-pin-revision fixture 2', solve(N,N,"p"*N), ["ok","p"*N])
check('representation-pin-revision fixture 3', solve(0,0,""), ["ok",""])
check('representation-pin-revision fixture 4', solve(0,N,"p"), ["restart",""])
check('representation-pin-revision fixture 5', solve(N,0,"p"), ["restart",""])
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 fixtureActualExpectedOutcome
representation-pin-revision fixture 0['ok', 'p']['restart', '']Failed
representation-pin-revision fixture 1['restart', '']['restart', '']Passed
representation-pin-revision fixture 2['ok', 'p']['ok', 'p']Passed
representation-pin-revision fixture 3['ok', '']['ok', '']Passed
representation-pin-revision fixture 4['ok', 'p']['restart', '']Failed
representation-pin-revision fixture 5['restart', '']['restart', '']Passed

SHA-256 / 9ca4aa099d906b35cbdbb37afc0c22204deb450be4ab29a0809d950bcef62011

3 / The verified repair

Exit 0
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(header_revision, body_revision, body):
    return ["ok",body] if body_revision==header_revision else ["restart",""]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('representation-pin-revision fixture 0', solve(N,N+1,"p"*N), ["restart",""])
check('representation-pin-revision fixture 1', solve(N+1,N,"p"), ["restart",""])
check('representation-pin-revision fixture 2', solve(N,N,"p"*N), ["ok","p"*N])
check('representation-pin-revision fixture 3', solve(0,0,""), ["ok",""])
check('representation-pin-revision fixture 4', solve(0,N,"p"), ["restart",""])
check('representation-pin-revision fixture 5', solve(N,0,"p"), ["restart",""])
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 fixtureActualExpectedOutcome
representation-pin-revision fixture 0['restart', '']['restart', '']Passed
representation-pin-revision fixture 1['restart', '']['restart', '']Passed
representation-pin-revision fixture 2['ok', 'p']['ok', 'p']Passed
representation-pin-revision fixture 3['ok', '']['ok', '']Passed
representation-pin-revision fixture 4['restart', '']['restart', '']Passed
representation-pin-revision fixture 5['restart', '']['restart', '']Passed

SHA-256 / 6a097f8ad1df03c2b46f10b9ed587230a2b42197f30694c12ad3f8f5bb939a97

Verification & scope

Deterministic simplified range service, with stipulated local policies and already parsed trusted inputs; not a complete HTTP implementation. 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 2026-09-29T14:41:15.843550+00:00.

Case digest / 69e6ad68e3b41589d69e92fa083e29fe51c68f6947537d2538cdcb3d1e05a9dc