FA-3326 / Encodings / Open access

ASCII85 expands the zero tuple incorrectly · case 01

ASCII85 expands the zero tuple incorrectly.

Verified by executionVariant 1 · 4 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The implementation applies an operation whose text or grammar semantics violate this contract: Encode ASCII85 using the zero-tuple z abbreviation without Adobe wrapping.

VERIFIED REPAIR

Implement the complete stated contract, including the boundary fixtures: Encode ASCII85 using the zero-tuple z abbreviation without Adobe wrapping.

Unsuccessful approach: The attempted repair handles the primary example but still violates a separate boundary of the same contract.

Case contract

Encode ASCII85 using the zero-tuple z abbreviation without Adobe wrapping.

Why this case matters

A local executable model for consumers of structured text; oracle values are authored literals, not outputs copied from the repaired implementation.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import re, unicodedata, json, csv, io, html, base64, binascii, codecs, struct
from urllib.parse import quote, unquote, unquote_to_bytes, urlencode, parse_qsl, urlsplit, urlunsplit
from email.header import decode_header, make_header
from email.utils import getaddresses
from xml.etree import ElementTree as ET
import shlex, string, textwrap

N = 1
observations = []
def solve(x):
    try:
        return base64.b85encode(bytes.fromhex(x)).decode()
    except Exception as exc:
        return {"error": type(exc).__name__}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('boundary 1', solve('00000000'), 'z')
check('boundary 2', solve('61'), '@/')
check('boundary 3', solve('0000000000000000'), 'zz')
check('boundary 4', solve(''), '')
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
boundary 1	`00000`	`z`	Failed
boundary 2	`VE`	`@/`	Failed
boundary 3	`0000000000`	`zz`	Failed
boundary 4			Passed

SHA-256 / 9312144a150d347b97242f74fc93fe6c0b0acb032ba03c7f00eb7d41161ddf84

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import re, unicodedata, json, csv, io, html, base64, binascii, codecs, struct
from urllib.parse import quote, unquote, unquote_to_bytes, urlencode, parse_qsl, urlsplit, urlunsplit
from email.header import decode_header, make_header
from email.utils import getaddresses
from xml.etree import ElementTree as ET
import shlex, string, textwrap

N = 1
observations = []
def solve(x):
    try:
        return base64.a85encode(bytes.fromhex(x)).decode().replace('z','!!!!!')
    except Exception as exc:
        return {"error": type(exc).__name__}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('boundary 1', solve('00000000'), 'z')
check('boundary 2', solve('61'), '@/')
check('boundary 3', solve('0000000000000000'), 'zz')
check('boundary 4', solve(''), '')
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
boundary 1	`!!!!!`	`z`	Failed
boundary 2	`@/`	`@/`	Passed
boundary 3	`!!!!!!!!!!`	`zz`	Failed
boundary 4			Passed

SHA-256 / 94bfcc0dd9c1630e2bb5024f89b3d364a47d39c31bba04abd44ced36ab01ebff

3 / The verified repair

Exit 0

"""Failure Map reference implementation. Python standard library only."""
import json
import re, unicodedata, json, csv, io, html, base64, binascii, codecs, struct
from urllib.parse import quote, unquote, unquote_to_bytes, urlencode, parse_qsl, urlsplit, urlunsplit
from email.header import decode_header, make_header
from email.utils import getaddresses
from xml.etree import ElementTree as ET
import shlex, string, textwrap

N = 1
observations = []
def solve(x):
    try:
        return base64.a85encode(bytes.fromhex(x)).decode()
    except Exception as exc:
        return {"error": type(exc).__name__}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('boundary 1', solve('00000000'), 'z')
check('boundary 2', solve('61'), '@/')
check('boundary 3', solve('0000000000000000'), 'zz')
check('boundary 4', solve(''), '')
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
boundary 1	`z`	`z`	Passed
boundary 2	`@/`	`@/`	Passed
boundary 3	`zz`	`zz`	Passed
boundary 4			Passed

SHA-256 / 8bb7d5a31dd0dbb11f8bdaaea11a2f164021c6705650cad5c6ff84b3145a8d3d

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 2026-09-29T14:37:24.398812+00:00.

Case digest / 383d469e70bfad83f8b7424477604193f8431e7809deccc17e985a45c380c762