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FA-26531 / HTTP ranges / Open access

A fresh full response replaces all stale sparse fragments · case 01

A fresh full response replaces all stale sparse fragments.

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

ROOT CAUSE

The cache-full-response-replaces-fragments decision uses r=dict(old) r.update(enumerate(full)) return sorted(r.items()).

VERIFIED REPAIR

Apply the bounded decision exactly: return list(enumerate(full))

Unsuccessful approach: The partial repair uses return sorted(old.items()) if not full else list(enumerate(full)), which still violates the stated contract.

Case contract

old maps absolute offsets to old chars. A completed full ASCII body atomically replaces the whole partial cache, including removal of bytes past new EOF.

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(old, full):
    r=dict(old)
    r.update(enumerate(full))
    return sorted(r.items())
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('cache-full-response-replaces-fragments fixture 0', solve( {0:"x",N+2:"z"},"a"*N), list(enumerate("a"*N)))
check('cache-full-response-replaces-fragments fixture 1', solve({0:"x"},""), [])
check('cache-full-response-replaces-fragments fixture 2', solve({},"ab"), [(0,"a"),(1,"b")])
check('cache-full-response-replaces-fragments fixture 3', solve({0:"x"},"a"), [(0,"a")])
check('cache-full-response-replaces-fragments fixture 4', solve({},""), [])
check('cache-full-response-replaces-fragments fixture 5', solve({1:"b"},"xy"), [(0,"x"),(1,"y")])
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
cache-full-response-replaces-fragments fixture 0[[0, 'a'], [3, 'z']][[0, 'a']]Failed
cache-full-response-replaces-fragments fixture 1[[0, 'x']][]Failed
cache-full-response-replaces-fragments fixture 2[[0, 'a'], [1, 'b']][[0, 'a'], [1, 'b']]Passed
cache-full-response-replaces-fragments fixture 3[[0, 'a']][[0, 'a']]Passed
cache-full-response-replaces-fragments fixture 4[][]Passed
cache-full-response-replaces-fragments fixture 5[[0, 'x'], [1, 'y']][[0, 'x'], [1, 'y']]Passed

SHA-256 / db4d9416539ce59eb86485a6d1a3782a3b1f32a278b06b2d37655125590a89bd

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(old, full):
    return sorted(old.items()) if not full else list(enumerate(full))
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('cache-full-response-replaces-fragments fixture 0', solve( {0:"x",N+2:"z"},"a"*N), list(enumerate("a"*N)))
check('cache-full-response-replaces-fragments fixture 1', solve({0:"x"},""), [])
check('cache-full-response-replaces-fragments fixture 2', solve({},"ab"), [(0,"a"),(1,"b")])
check('cache-full-response-replaces-fragments fixture 3', solve({0:"x"},"a"), [(0,"a")])
check('cache-full-response-replaces-fragments fixture 4', solve({},""), [])
check('cache-full-response-replaces-fragments fixture 5', solve({1:"b"},"xy"), [(0,"x"),(1,"y")])
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
cache-full-response-replaces-fragments fixture 0[[0, 'a']][[0, 'a']]Passed
cache-full-response-replaces-fragments fixture 1[[0, 'x']][]Failed
cache-full-response-replaces-fragments fixture 2[[0, 'a'], [1, 'b']][[0, 'a'], [1, 'b']]Passed
cache-full-response-replaces-fragments fixture 3[[0, 'a']][[0, 'a']]Passed
cache-full-response-replaces-fragments fixture 4[][]Passed
cache-full-response-replaces-fragments fixture 5[[0, 'x'], [1, 'y']][[0, 'x'], [1, 'y']]Passed

SHA-256 / 722230a350dfd2129fd3420df90d2bec53224e3fe8fc1f5c7e99bd55261e3664

3 / The verified repair

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

N = 1
observations = []
def solve(old, full):
    return list(enumerate(full))
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('cache-full-response-replaces-fragments fixture 0', solve( {0:"x",N+2:"z"},"a"*N), list(enumerate("a"*N)))
check('cache-full-response-replaces-fragments fixture 1', solve({0:"x"},""), [])
check('cache-full-response-replaces-fragments fixture 2', solve({},"ab"), [(0,"a"),(1,"b")])
check('cache-full-response-replaces-fragments fixture 3', solve({0:"x"},"a"), [(0,"a")])
check('cache-full-response-replaces-fragments fixture 4', solve({},""), [])
check('cache-full-response-replaces-fragments fixture 5', solve({1:"b"},"xy"), [(0,"x"),(1,"y")])
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
cache-full-response-replaces-fragments fixture 0[[0, 'a']][[0, 'a']]Passed
cache-full-response-replaces-fragments fixture 1[][]Passed
cache-full-response-replaces-fragments fixture 2[[0, 'a'], [1, 'b']][[0, 'a'], [1, 'b']]Passed
cache-full-response-replaces-fragments fixture 3[[0, 'a']][[0, 'a']]Passed
cache-full-response-replaces-fragments fixture 4[][]Passed
cache-full-response-replaces-fragments fixture 5[[0, 'x'], [1, 'y']][[0, 'x'], [1, 'y']]Passed

SHA-256 / 6bf39738141f0c8580d3d9d9d44c11eac8bf9f52e5c0fd2aa9503c64f7bec6ef

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 2026-09-29T14:41:16.890708+00:00.

Case digest / 8278225e6d435bc609eaeee5149b686a29d36e9c385521f3211f97f4c276322d