FAILURE MAP
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FA-26556 / HTTP ranges / Open access

Multipart framing bytes do not advance the representation cursor · case 01

Multipart framing bytes do not advance the representation cursor.

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

ROOT CAUSE

The stream-framing-not-progress decision uses return offset+payload_written+framing_written.

VERIFIED REPAIR

Apply the bounded decision exactly: return offset+payload_written

Unsuccessful approach: The partial repair uses return offset+max(payload_written,framing_written), which still violates the stated contract.

Case contract

Return representation cursor after payload writes; framing bytes are tracked by the transport separately.

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(offset, payload_written, framing_written):
    return offset+payload_written+framing_written
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('stream-framing-not-progress fixture 0', solve(N,N,3*N), 2*N)
check('stream-framing-not-progress fixture 1', solve(N,0,N), N)
check('stream-framing-not-progress fixture 2', solve(N,N,0), 2*N)
check('stream-framing-not-progress fixture 3', solve(0,0,0), 0)
check('stream-framing-not-progress fixture 4', solve(0,2*N,N), 2*N)
check('stream-framing-not-progress fixture 5', solve(3*N,N,N), 4*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 fixtureActualExpectedOutcome
stream-framing-not-progress fixture 052Failed
stream-framing-not-progress fixture 121Failed
stream-framing-not-progress fixture 222Passed
stream-framing-not-progress fixture 300Passed
stream-framing-not-progress fixture 432Failed
stream-framing-not-progress fixture 554Failed

SHA-256 / b17b05f8fc98b6095b9bbdba556f7683745f3d697653bc3235d14758bb53dfc8

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(offset, payload_written, framing_written):
    return offset+max(payload_written,framing_written)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('stream-framing-not-progress fixture 0', solve(N,N,3*N), 2*N)
check('stream-framing-not-progress fixture 1', solve(N,0,N), N)
check('stream-framing-not-progress fixture 2', solve(N,N,0), 2*N)
check('stream-framing-not-progress fixture 3', solve(0,0,0), 0)
check('stream-framing-not-progress fixture 4', solve(0,2*N,N), 2*N)
check('stream-framing-not-progress fixture 5', solve(3*N,N,N), 4*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 fixtureActualExpectedOutcome
stream-framing-not-progress fixture 042Failed
stream-framing-not-progress fixture 121Failed
stream-framing-not-progress fixture 222Passed
stream-framing-not-progress fixture 300Passed
stream-framing-not-progress fixture 422Passed
stream-framing-not-progress fixture 544Passed

SHA-256 / 391ec7d5fb283aefbeb68985549661bd22cfbf4c0f2af971cd477d233fdca049

3 / The verified repair

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

N = 1
observations = []
def solve(offset, payload_written, framing_written):
    return offset+payload_written
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('stream-framing-not-progress fixture 0', solve(N,N,3*N), 2*N)
check('stream-framing-not-progress fixture 1', solve(N,0,N), N)
check('stream-framing-not-progress fixture 2', solve(N,N,0), 2*N)
check('stream-framing-not-progress fixture 3', solve(0,0,0), 0)
check('stream-framing-not-progress fixture 4', solve(0,2*N,N), 2*N)
check('stream-framing-not-progress fixture 5', solve(3*N,N,N), 4*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 fixtureActualExpectedOutcome
stream-framing-not-progress fixture 022Passed
stream-framing-not-progress fixture 111Passed
stream-framing-not-progress fixture 222Passed
stream-framing-not-progress fixture 300Passed
stream-framing-not-progress fixture 422Passed
stream-framing-not-progress fixture 544Passed

SHA-256 / 32dcf440d06a628ebbfb56a1d150f362c05534a2e9aca807f6c0317dd7efa935

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 2026-09-29T14:41:17.016368+00:00.

Case digest / 245f1103d47c204e02dff6ce74167ee186a7119d52226575e1e6ca8b21d3c85e