FA-10476 / Caching / Open access
Representation identity ignores one of the selected request headers · case 01
Representation identity ignores one of the selected request headers.
ROOT CAUSE
A multi-header variant key keeps only the first selected dimension.
VERIFIED REPAIR
Preserve the cache-state invariant: Header names are already normalized lowercase and values are strings. Return sorted unique requested Vary names paired with value or None for missing fields; ignore unselected headers.
Unsuccessful approach: Keying on every request header fragments entries on unrelated tracing metadata.
Case contract
Header names are already normalized lowercase and values are strings. Return sorted unique requested Vary names paired with value or None for missing fields; ignore unselected headers.
Why this case matters
A deterministic cache state transformation. Inputs are copied or treated as immutable; no remote storage, real clock, or concurrent interleaving is simulated.
1 / The failure
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(vary, headers):
return [[name,headers.get(name)] for name in vary[:1]]
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve(*(['accept', 'lang'], {'accept': 'json', 'lang': 'fr', 'trace': 'x'})), [['accept', 'json'], ['lang', 'fr']])
check('fixture 2', solve(*(['lang'], {'lang': 'en', 'trace': 'y'})), [['lang', 'en']])
check('fixture 3', solve(*([], {'trace': 'x'})), [])
check('fixture 4', solve(*(['lang', 'lang'], {})), [['lang', None]])
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 |
|---|---|---|---|
| fixture 1 | [['accept', 'json']] | [['accept', 'json'], ['lang', 'fr']] | Failed |
| fixture 2 | [['lang', 'en']] | [['lang', 'en']] | Passed |
| fixture 3 | [] | [] | Passed |
| fixture 4 | [['lang', None]] | [['lang', None]] | Passed |
SHA-256 / 2642f1fa52920c871369c42739ddb5189959113c453d93a2c14856592f69c781
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(vary, headers):
return [[name,headers.get(name)] for name in sorted(headers)]
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve(*(['accept', 'lang'], {'accept': 'json', 'lang': 'fr', 'trace': 'x'})), [['accept', 'json'], ['lang', 'fr']])
check('fixture 2', solve(*(['lang'], {'lang': 'en', 'trace': 'y'})), [['lang', 'en']])
check('fixture 3', solve(*([], {'trace': 'x'})), [])
check('fixture 4', solve(*(['lang', 'lang'], {})), [['lang', None]])
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 |
|---|---|---|---|
| fixture 1 | [['accept', 'json'], ['lang', 'fr'], ['trace', 'x']] | [['accept', 'json'], ['lang', 'fr']] | Failed |
| fixture 2 | [['lang', 'en'], ['trace', 'y']] | [['lang', 'en']] | Failed |
| fixture 3 | [['trace', 'x']] | [] | Failed |
| fixture 4 | [] | [['lang', None]] | Failed |
SHA-256 / 09207463d2e86b7318329ffb02073419163f2396a378a57e25facba639ce7903
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(vary, headers):
return [[name,headers.get(name)] for name in sorted(set(vary))]
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve(*(['accept', 'lang'], {'accept': 'json', 'lang': 'fr', 'trace': 'x'})), [['accept', 'json'], ['lang', 'fr']])
check('fixture 2', solve(*(['lang'], {'lang': 'en', 'trace': 'y'})), [['lang', 'en']])
check('fixture 3', solve(*([], {'trace': 'x'})), [])
check('fixture 4', solve(*(['lang', 'lang'], {})), [['lang', None]])
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 |
|---|---|---|---|
| fixture 1 | [['accept', 'json'], ['lang', 'fr']] | [['accept', 'json'], ['lang', 'fr']] | Passed |
| fixture 2 | [['lang', 'en']] | [['lang', 'en']] | Passed |
| fixture 3 | [] | [] | Passed |
| fixture 4 | [['lang', None]] | [['lang', None]] | Passed |
SHA-256 / 25adf4e19484d84e6e7abbb37b64f15595158a614392254bb70631eaa3fa2fa1
Verification & scope
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 2026-09-29T14:38:39.315665+00:00.
Case digest / 284df38a0d678ee2d94a041a9f6f9c310ac6a9b80817fba5549b94931d108a4a