FA-26386 / HTTP ranges / Open access

HEAD retains full representation metadata while suppressing the body · case 01

HEAD retains full representation metadata while suppressing the body.

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

ROOT CAUSE

The head-ignores-range-body decision uses return [206,len(part),part] if method == "GET" else [206,len(part),""].

THE FAILURE

The head-ignores-range-body decision uses return [206,len(part),part] if method == "GET" else [206,len(part),""].

Unsuccessful approach: The partial repair uses return [206,len(part),part] if method == "GET" else [200,len(part),""], which still violates the stated contract.

Case contract

Only GET honors the already resolved range. HEAD returns [200,full-length,empty], GET [206,part-length,part]. Inputs are ASCII strings.

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(method, full, part):
    return [206,len(part),part] if method == "GET" else [206,len(part),""]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('head-ignores-range-body fixture 0', solve("HEAD","abc"*N,"b"*N), [200,3*N,""])
check('head-ignores-range-body fixture 1', solve("GET","abc"*N,"b"*N), [206,N,"b"*N])
check('head-ignores-range-body fixture 2', solve("HEAD","",""), [200,0,""])
check('head-ignores-range-body fixture 3', solve("HEAD","abcd",""), [200,4,""])
check('head-ignores-range-body fixture 4', solve("GET","abcd",""), [206,0,""])
check('head-ignores-range-body fixture 5', solve("GET","abcd","abcd"), [206,4,"abcd"])
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
head-ignores-range-body fixture 0	`[206, 1, '']`	`[200, 3, '']`	Failed
head-ignores-range-body fixture 1	`[206, 1, 'b']`	`[206, 1, 'b']`	Passed
head-ignores-range-body fixture 2	`[206, 0, '']`	`[200, 0, '']`	Failed
head-ignores-range-body fixture 3	`[206, 0, '']`	`[200, 4, '']`	Failed
head-ignores-range-body fixture 4	`[206, 0, '']`	`[206, 0, '']`	Passed
head-ignores-range-body fixture 5	`[206, 4, 'abcd']`	`[206, 4, 'abcd']`	Passed

SHA-256 / 2289a7777fffa89d2a78a4bfed65b78c9a02aa127b58efcf0f0fe19d6a193f26

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(method, full, part):
    return [206,len(part),part] if method == "GET" else [200,len(part),""]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('head-ignores-range-body fixture 0', solve("HEAD","abc"*N,"b"*N), [200,3*N,""])
check('head-ignores-range-body fixture 1', solve("GET","abc"*N,"b"*N), [206,N,"b"*N])
check('head-ignores-range-body fixture 2', solve("HEAD","",""), [200,0,""])
check('head-ignores-range-body fixture 3', solve("HEAD","abcd",""), [200,4,""])
check('head-ignores-range-body fixture 4', solve("GET","abcd",""), [206,0,""])
check('head-ignores-range-body fixture 5', solve("GET","abcd","abcd"), [206,4,"abcd"])
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
head-ignores-range-body fixture 0	`[200, 1, '']`	`[200, 3, '']`	Failed
head-ignores-range-body fixture 1	`[206, 1, 'b']`	`[206, 1, 'b']`	Passed
head-ignores-range-body fixture 2	`[200, 0, '']`	`[200, 0, '']`	Passed
head-ignores-range-body fixture 3	`[200, 0, '']`	`[200, 4, '']`	Failed
head-ignores-range-body fixture 4	`[206, 0, '']`	`[206, 0, '']`	Passed
head-ignores-range-body fixture 5	`[206, 4, 'abcd']`	`[206, 4, 'abcd']`	Passed

SHA-256 / b275004825db95441095401aecd11280310a4a8b1ae5e9a1ce97d51ba870adf0

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

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 2026-09-29T14:41:15.635934+00:00.

Case digest / ffe0ca41df472f5c69b65d7c36e74dfe892b2e21e3f37fc08354b42a56f67e8a