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FA-79576 / Barcode symbology encoding / Open access

GS1-128 inserts FNC1 after fixed-length fields · case 01

Labels waste a symbol character after every GTIN and date and some parsers reject the extra separator.

Verified by executionVariant 1 · 8 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

A separator is added after every field that is not last, including predefined-length AIs.

VERIFIED REPAIR

Only variable-length fields need a following FNC1.

Unsuccessful approach: Treating date AIs as variable-length still adds needless separators.

Case contract

Assemble GS1-128 data from [AI, value] pairs; "#" stands for FNC1. The string starts with FNC1. Predefined fixed-length AIs: 00 (18), 01 and 02 (14), 11/13/15/17 (6), 3103 (6); variable-length AIs with maximum length: 10 and 21 (20), 30 and 37 (8), 400 (30). Numeric AIs: 00, 01, 02, 11, 13, 15, 17, 3103, 30, 37. Values use printable ASCII 33..126 except "#". A variable-length field is followed by FNC1 unless it is last. Errors: unknown-ai, bad-value.

Why this case matters

Retail, logistics, pharmacy and document workflows depend on encoders that produce exactly the module pattern, code-set switches, separators and quiet zones scanners expect; one misplaced module or separator makes a label unreadable or, worse, scan as different data.

1 / The failure

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

N = 1
observations = []
def solve(fields):
    fixed_len = {'00': 18, '01': 14, '02': 14, '11': 6, '13': 6, '15': 6, '17': 6, '3103': 6}
    var_max = {'10': 20, '21': 20, '30': 8, '37': 8, '400': 30}
    numeric = {'00', '01', '02', '11', '13', '15', '17', '3103', '30', '37'}
    out = '#'
    for idx, (ai, val) in enumerate(fields):
        if ai in fixed_len:
            if len(val) != fixed_len[ai]:
                return {'error': 'bad-value', 'ai': ai}
        elif ai in var_max:
            if not 1 <= len(val) <= var_max[ai]:
                return {'error': 'bad-value', 'ai': ai}
        else:
            return {'error': 'unknown-ai', 'ai': ai}
        if ai in numeric and not all(c in '0123456789' for c in val):
            return {'error': 'bad-value', 'ai': ai}
        if not all(33 <= ord(c) <= 126 and c != '#' for c in val):
            return {'error': 'bad-value', 'ai': ai}
        out += ai + val
        if idx < len(fields) - 1:
            out += '#'
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[[['17', '124248'], ['400', 'BAB1XXX/9BAB1B1XC1BCX'], ['30', '86711'], ['11', '769392']], '#17124248400BAB1XXX/9BAB1B1XC1BCX#3086711#11769392'], [[['02', '55122636826325'], ['17', '336235'], ['15', '379442']], '#02551226368263251733623515379442'], [[['00', '90045075234391735A']], {'error': 'bad-value', 'ai': '00'}], [[['30', '314304438']], {'error': 'bad-value', 'ai': '30'}], [[['30', '498926295']], {'error': 'bad-value', 'ai': '30'}], [[['37', '9681'], ['37', '30'], ['30', '601935739'], ['30', '135282']], {'error': 'bad-value', 'ai': '30'}], [[['400', 'BB9B9BCB9AC9BX1X-'], ['3103', '121391'], ['11', '565147'], ['15', '67097']], {'error': 'bad-value', 'ai': '15'}], [[['400', 'X9B1-1X9--'], ['3103', '754725'], ['30', '31441746']], '#400X9B1-1X9--#31037547253031441746']], [[[['3103', '254890'], ['10', 'XCX-91A-']], '#310325489010XCX-91A-'], [[['400', '/XA1XB9A9/B/'], ['15', '153070'], ['17', '288329'], ['01', '17366692698106']], '#400/XA1XB9A9/B/#15153070172883290117366692698106'], [[['15', '556647'], ['37', '11615664'], ['13', '817002'], ['11', '500201']], '#155566473711615664#1381700211500201'], [[['11', '827833']], '#11827833'], [[['10', '999B9'], ['02', '83916947090792'], ['02', '6235977446030']], {'error': 'bad-value', 'ai': '02'}], [[['17', '194565'], ['3103', '606142'], ['11', '39946#'], ['13', '993221']], {'error': 'bad-value', 'ai': '11'}], [[['02', '50315475817306'], ['13', '780102'], ['30', '86357A'], ['21', '-9C/C9BB-']], {'error': 'bad-value', 'ai': '30'}], [[['11', '875343'], ['17', '156844'], ['37', '4945']], '#1187534317156844374945']], [[[['30', '1351629'], ['15', '437225'], ['00', '339737021321235033']], '#301351629#1543722500339737021321235033'], [[['11', '684472'], ['30', '151'], ['30', '41437504']], '#1168447230151#3041437504'], [[['21', 'B1'], ['400', '--9CB-'], ['11', '646444'], ['02', '27996349722474']], '#21B1#400--9CB-#116464440227996349722474'], [[['400', '-']], '#400-'], [[['3103', '']], {'error': 'bad-value', 'ai': '3103'}], [[['01', '16614057569424'], ['01', '04741883691497'], ['3103', '20240101'], ['17', '174564']], {'error': 'bad-value', 'ai': '3103'}], [[['37', '08071557'], ['10', 'BB9-C'], ['3103', '566874']], '#3708071557#10BB9-C#3103566874'], [[['3103', '506096'], ['30', '1'], ['11', '465886']], '#3103506096301#11465886']], [[[['01', '09162556501441'], ['13', '875444']], '#010916255650144113875444'], [[['17', '571639'], ['10', '1/99AAX19ABBXA1-AB1X'], ['3103', '938334'], ['30', '5']], '#17571639101/99AAX19ABBXA1-AB1X#3103938334305'], [[['17', '109805'], ['3103', '602171'], ['17', '948038']], '#17109805310360217117948038'], [[['15', '29986'], ['11', '20240101']], {'error': 'bad-value', 'ai': '15'}], [[['17', ''], ['11', ''], ['13', '934852']], {'error': 'bad-value', 'ai': '17'}], [[['11', '293752']], '#11293752'], [[['30', '38239528'], ['21', '-AA-//XB/9']], '#3038239528#21-AA-//XB/9'], [[['15', '819947'], ['10', '9B-'], ['17', '065810']], '#15819947109B-#17065810']], [[[['15', '009908'], ['11', '813644']], '#1500990811813644'], [[['01', '21550398685673'], ['15', '789070'], ['13', '754989']], '#01215503986856731578907013754989'], [[['00', '444497203722145564'], ['13', '779635'], ['10', '99/AC-/91191BBA9XB/'], ['400', 'XCBC']], '#00444497203722145564137796351099/AC-/91191BBA9XB/#400XCBC'], [[['01', '3897861456853'], ['17', '642893']], {'error': 'bad-value', 'ai': '01'}], [[['17', '921066'], ['02', '71174568179311'], ['15', '310514'], ['00', '274821770369219022'], ['99', 'X']], {'error': 'unknown-ai', 'ai': '99'}], [[['21', '-9CCBBBB9AB-ABB-9/C'], ['21', 'X1AC/AA-9/9-CXA9//19']], '#21-9CCBBBB9AB-ABB-9/C#21X1AC/AA-9/9-CXA9//19'], [[['37', '60024422']], '#3760024422'], [[['15', '736088'], ['00', '231739916417638479']], '#1573608800231739916417638479']]]
labels = ["regression: separator after predefined-length fields", "repair trap", "combined fault", "control", "control", "boundary", "boundary", "control"]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("%s %d" % (labels[i % len(labels)], i), solve(args), expected)
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
regression: separator after predefined-length fields 0#17124248#400BAB1XXX/9BAB1B1XC1BCX#3086711#11769392#17124248400BAB1XXX/9BAB1B1XC1BCX#3086711#11769392Failed
repair trap 1#0255122636826325#17336235#15379442#02551226368263251733623515379442Failed
combined fault 2{'ai': '00', 'error': 'bad-value'}{'ai': '00', 'error': 'bad-value'}Passed
control 3{'ai': '30', 'error': 'bad-value'}{'ai': '30', 'error': 'bad-value'}Passed
control 4{'ai': '30', 'error': 'bad-value'}{'ai': '30', 'error': 'bad-value'}Passed
boundary 5{'ai': '30', 'error': 'bad-value'}{'ai': '30', 'error': 'bad-value'}Passed
boundary 6{'ai': '15', 'error': 'bad-value'}{'ai': '15', 'error': 'bad-value'}Passed
control 7#400X9B1-1X9--#3103754725#3031441746#400X9B1-1X9--#31037547253031441746Failed

SHA-256 / e8023316eceb55c9884655b81f31fcd33d8c1885e713db2bcadd6331b08e6e7c

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(fields):
    fixed_len = {'00': 18, '01': 14, '02': 14, '11': 6, '13': 6, '15': 6, '17': 6, '3103': 6}
    var_max = {'10': 20, '21': 20, '30': 8, '37': 8, '400': 30}
    numeric = {'00', '01', '02', '11', '13', '15', '17', '3103', '30', '37'}
    out = '#'
    for idx, (ai, val) in enumerate(fields):
        if ai in fixed_len:
            if len(val) != fixed_len[ai]:
                return {'error': 'bad-value', 'ai': ai}
        elif ai in var_max:
            if not 1 <= len(val) <= var_max[ai]:
                return {'error': 'bad-value', 'ai': ai}
        else:
            return {'error': 'unknown-ai', 'ai': ai}
        if ai in numeric and not all(c in '0123456789' for c in val):
            return {'error': 'bad-value', 'ai': ai}
        if not all(33 <= ord(c) <= 126 and c != '#' for c in val):
            return {'error': 'bad-value', 'ai': ai}
        out += ai + val
        if (ai in var_max or ai in ('11', '13', '15', '17')) and idx < len(fields) - 1:
            out += '#'
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[[['17', '124248'], ['400', 'BAB1XXX/9BAB1B1XC1BCX'], ['30', '86711'], ['11', '769392']], '#17124248400BAB1XXX/9BAB1B1XC1BCX#3086711#11769392'], [[['02', '55122636826325'], ['17', '336235'], ['15', '379442']], '#02551226368263251733623515379442'], [[['00', '90045075234391735A']], {'error': 'bad-value', 'ai': '00'}], [[['30', '314304438']], {'error': 'bad-value', 'ai': '30'}], [[['30', '498926295']], {'error': 'bad-value', 'ai': '30'}], [[['37', '9681'], ['37', '30'], ['30', '601935739'], ['30', '135282']], {'error': 'bad-value', 'ai': '30'}], [[['400', 'BB9B9BCB9AC9BX1X-'], ['3103', '121391'], ['11', '565147'], ['15', '67097']], {'error': 'bad-value', 'ai': '15'}], [[['400', 'X9B1-1X9--'], ['3103', '754725'], ['30', '31441746']], '#400X9B1-1X9--#31037547253031441746']], [[[['3103', '254890'], ['10', 'XCX-91A-']], '#310325489010XCX-91A-'], [[['400', '/XA1XB9A9/B/'], ['15', '153070'], ['17', '288329'], ['01', '17366692698106']], '#400/XA1XB9A9/B/#15153070172883290117366692698106'], [[['15', '556647'], ['37', '11615664'], ['13', '817002'], ['11', '500201']], '#155566473711615664#1381700211500201'], [[['11', '827833']], '#11827833'], [[['10', '999B9'], ['02', '83916947090792'], ['02', '6235977446030']], {'error': 'bad-value', 'ai': '02'}], [[['17', '194565'], ['3103', '606142'], ['11', '39946#'], ['13', '993221']], {'error': 'bad-value', 'ai': '11'}], [[['02', '50315475817306'], ['13', '780102'], ['30', '86357A'], ['21', '-9C/C9BB-']], {'error': 'bad-value', 'ai': '30'}], [[['11', '875343'], ['17', '156844'], ['37', '4945']], '#1187534317156844374945']], [[[['30', '1351629'], ['15', '437225'], ['00', '339737021321235033']], '#301351629#1543722500339737021321235033'], [[['11', '684472'], ['30', '151'], ['30', '41437504']], '#1168447230151#3041437504'], [[['21', 'B1'], ['400', '--9CB-'], ['11', '646444'], ['02', '27996349722474']], '#21B1#400--9CB-#116464440227996349722474'], [[['400', '-']], '#400-'], [[['3103', '']], {'error': 'bad-value', 'ai': '3103'}], [[['01', '16614057569424'], ['01', '04741883691497'], ['3103', '20240101'], ['17', '174564']], {'error': 'bad-value', 'ai': '3103'}], [[['37', '08071557'], ['10', 'BB9-C'], ['3103', '566874']], '#3708071557#10BB9-C#3103566874'], [[['3103', '506096'], ['30', '1'], ['11', '465886']], '#3103506096301#11465886']], [[[['01', '09162556501441'], ['13', '875444']], '#010916255650144113875444'], [[['17', '571639'], ['10', '1/99AAX19ABBXA1-AB1X'], ['3103', '938334'], ['30', '5']], '#17571639101/99AAX19ABBXA1-AB1X#3103938334305'], [[['17', '109805'], ['3103', '602171'], ['17', '948038']], '#17109805310360217117948038'], [[['15', '29986'], ['11', '20240101']], {'error': 'bad-value', 'ai': '15'}], [[['17', ''], ['11', ''], ['13', '934852']], {'error': 'bad-value', 'ai': '17'}], [[['11', '293752']], '#11293752'], [[['30', '38239528'], ['21', '-AA-//XB/9']], '#3038239528#21-AA-//XB/9'], [[['15', '819947'], ['10', '9B-'], ['17', '065810']], '#15819947109B-#17065810']], [[[['15', '009908'], ['11', '813644']], '#1500990811813644'], [[['01', '21550398685673'], ['15', '789070'], ['13', '754989']], '#01215503986856731578907013754989'], [[['00', '444497203722145564'], ['13', '779635'], ['10', '99/AC-/91191BBA9XB/'], ['400', 'XCBC']], '#00444497203722145564137796351099/AC-/91191BBA9XB/#400XCBC'], [[['01', '3897861456853'], ['17', '642893']], {'error': 'bad-value', 'ai': '01'}], [[['17', '921066'], ['02', '71174568179311'], ['15', '310514'], ['00', '274821770369219022'], ['99', 'X']], {'error': 'unknown-ai', 'ai': '99'}], [[['21', '-9CCBBBB9AB-ABB-9/C'], ['21', 'X1AC/AA-9/9-CXA9//19']], '#21-9CCBBBB9AB-ABB-9/C#21X1AC/AA-9/9-CXA9//19'], [[['37', '60024422']], '#3760024422'], [[['15', '736088'], ['00', '231739916417638479']], '#1573608800231739916417638479']]]
labels = ["regression: separator after predefined-length fields", "repair trap", "combined fault", "control", "control", "boundary", "boundary", "control"]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("%s %d" % (labels[i % len(labels)], i), solve(args), expected)
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
regression: separator after predefined-length fields 0#17124248#400BAB1XXX/9BAB1B1XC1BCX#3086711#11769392#17124248400BAB1XXX/9BAB1B1XC1BCX#3086711#11769392Failed
repair trap 1#025512263682632517336235#15379442#02551226368263251733623515379442Failed
combined fault 2{'ai': '00', 'error': 'bad-value'}{'ai': '00', 'error': 'bad-value'}Passed
control 3{'ai': '30', 'error': 'bad-value'}{'ai': '30', 'error': 'bad-value'}Passed
control 4{'ai': '30', 'error': 'bad-value'}{'ai': '30', 'error': 'bad-value'}Passed
boundary 5{'ai': '30', 'error': 'bad-value'}{'ai': '30', 'error': 'bad-value'}Passed
boundary 6{'ai': '15', 'error': 'bad-value'}{'ai': '15', 'error': 'bad-value'}Passed
control 7#400X9B1-1X9--#31037547253031441746#400X9B1-1X9--#31037547253031441746Passed

SHA-256 / e3ae2e948d8486abd2392002b28e7918bed928def2a36d82b6527356857f2816

3 / The verified repair

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

N = 1
observations = []
def solve(fields):
    fixed_len = {'00': 18, '01': 14, '02': 14, '11': 6, '13': 6, '15': 6, '17': 6, '3103': 6}
    var_max = {'10': 20, '21': 20, '30': 8, '37': 8, '400': 30}
    numeric = {'00', '01', '02', '11', '13', '15', '17', '3103', '30', '37'}
    out = '#'
    for idx, (ai, val) in enumerate(fields):
        if ai in fixed_len:
            if len(val) != fixed_len[ai]:
                return {'error': 'bad-value', 'ai': ai}
        elif ai in var_max:
            if not 1 <= len(val) <= var_max[ai]:
                return {'error': 'bad-value', 'ai': ai}
        else:
            return {'error': 'unknown-ai', 'ai': ai}
        if ai in numeric and not all(c in '0123456789' for c in val):
            return {'error': 'bad-value', 'ai': ai}
        if not all(33 <= ord(c) <= 126 and c != '#' for c in val):
            return {'error': 'bad-value', 'ai': ai}
        out += ai + val
        if ai in var_max and idx < len(fields) - 1:
            out += '#'
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[[['17', '124248'], ['400', 'BAB1XXX/9BAB1B1XC1BCX'], ['30', '86711'], ['11', '769392']], '#17124248400BAB1XXX/9BAB1B1XC1BCX#3086711#11769392'], [[['02', '55122636826325'], ['17', '336235'], ['15', '379442']], '#02551226368263251733623515379442'], [[['00', '90045075234391735A']], {'error': 'bad-value', 'ai': '00'}], [[['30', '314304438']], {'error': 'bad-value', 'ai': '30'}], [[['30', '498926295']], {'error': 'bad-value', 'ai': '30'}], [[['37', '9681'], ['37', '30'], ['30', '601935739'], ['30', '135282']], {'error': 'bad-value', 'ai': '30'}], [[['400', 'BB9B9BCB9AC9BX1X-'], ['3103', '121391'], ['11', '565147'], ['15', '67097']], {'error': 'bad-value', 'ai': '15'}], [[['400', 'X9B1-1X9--'], ['3103', '754725'], ['30', '31441746']], '#400X9B1-1X9--#31037547253031441746']], [[[['3103', '254890'], ['10', 'XCX-91A-']], '#310325489010XCX-91A-'], [[['400', '/XA1XB9A9/B/'], ['15', '153070'], ['17', '288329'], ['01', '17366692698106']], '#400/XA1XB9A9/B/#15153070172883290117366692698106'], [[['15', '556647'], ['37', '11615664'], ['13', '817002'], ['11', '500201']], '#155566473711615664#1381700211500201'], [[['11', '827833']], '#11827833'], [[['10', '999B9'], ['02', '83916947090792'], ['02', '6235977446030']], {'error': 'bad-value', 'ai': '02'}], [[['17', '194565'], ['3103', '606142'], ['11', '39946#'], ['13', '993221']], {'error': 'bad-value', 'ai': '11'}], [[['02', '50315475817306'], ['13', '780102'], ['30', '86357A'], ['21', '-9C/C9BB-']], {'error': 'bad-value', 'ai': '30'}], [[['11', '875343'], ['17', '156844'], ['37', '4945']], '#1187534317156844374945']], [[[['30', '1351629'], ['15', '437225'], ['00', '339737021321235033']], '#301351629#1543722500339737021321235033'], [[['11', '684472'], ['30', '151'], ['30', '41437504']], '#1168447230151#3041437504'], [[['21', 'B1'], ['400', '--9CB-'], ['11', '646444'], ['02', '27996349722474']], '#21B1#400--9CB-#116464440227996349722474'], [[['400', '-']], '#400-'], [[['3103', '']], {'error': 'bad-value', 'ai': '3103'}], [[['01', '16614057569424'], ['01', '04741883691497'], ['3103', '20240101'], ['17', '174564']], {'error': 'bad-value', 'ai': '3103'}], [[['37', '08071557'], ['10', 'BB9-C'], ['3103', '566874']], '#3708071557#10BB9-C#3103566874'], [[['3103', '506096'], ['30', '1'], ['11', '465886']], '#3103506096301#11465886']], [[[['01', '09162556501441'], ['13', '875444']], '#010916255650144113875444'], [[['17', '571639'], ['10', '1/99AAX19ABBXA1-AB1X'], ['3103', '938334'], ['30', '5']], '#17571639101/99AAX19ABBXA1-AB1X#3103938334305'], [[['17', '109805'], ['3103', '602171'], ['17', '948038']], '#17109805310360217117948038'], [[['15', '29986'], ['11', '20240101']], {'error': 'bad-value', 'ai': '15'}], [[['17', ''], ['11', ''], ['13', '934852']], {'error': 'bad-value', 'ai': '17'}], [[['11', '293752']], '#11293752'], [[['30', '38239528'], ['21', '-AA-//XB/9']], '#3038239528#21-AA-//XB/9'], [[['15', '819947'], ['10', '9B-'], ['17', '065810']], '#15819947109B-#17065810']], [[[['15', '009908'], ['11', '813644']], '#1500990811813644'], [[['01', '21550398685673'], ['15', '789070'], ['13', '754989']], '#01215503986856731578907013754989'], [[['00', '444497203722145564'], ['13', '779635'], ['10', '99/AC-/91191BBA9XB/'], ['400', 'XCBC']], '#00444497203722145564137796351099/AC-/91191BBA9XB/#400XCBC'], [[['01', '3897861456853'], ['17', '642893']], {'error': 'bad-value', 'ai': '01'}], [[['17', '921066'], ['02', '71174568179311'], ['15', '310514'], ['00', '274821770369219022'], ['99', 'X']], {'error': 'unknown-ai', 'ai': '99'}], [[['21', '-9CCBBBB9AB-ABB-9/C'], ['21', 'X1AC/AA-9/9-CXA9//19']], '#21-9CCBBBB9AB-ABB-9/C#21X1AC/AA-9/9-CXA9//19'], [[['37', '60024422']], '#3760024422'], [[['15', '736088'], ['00', '231739916417638479']], '#1573608800231739916417638479']]]
labels = ["regression: separator after predefined-length fields", "repair trap", "combined fault", "control", "control", "boundary", "boundary", "control"]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("%s %d" % (labels[i % len(labels)], i), solve(args), expected)
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
regression: separator after predefined-length fields 0#17124248400BAB1XXX/9BAB1B1XC1BCX#3086711#11769392#17124248400BAB1XXX/9BAB1B1XC1BCX#3086711#11769392Passed
repair trap 1#02551226368263251733623515379442#02551226368263251733623515379442Passed
combined fault 2{'ai': '00', 'error': 'bad-value'}{'ai': '00', 'error': 'bad-value'}Passed
control 3{'ai': '30', 'error': 'bad-value'}{'ai': '30', 'error': 'bad-value'}Passed
control 4{'ai': '30', 'error': 'bad-value'}{'ai': '30', 'error': 'bad-value'}Passed
boundary 5{'ai': '30', 'error': 'bad-value'}{'ai': '30', 'error': 'bad-value'}Passed
boundary 6{'ai': '15', 'error': 'bad-value'}{'ai': '15', 'error': 'bad-value'}Passed
control 7#400X9B1-1X9--#31037547253031441746#400X9B1-1X9--#31037547253031441746Passed

SHA-256 / 3e1f204c6d96402fb1263298c75501b329beed5875afd8ceb51bce9fc3e4528e

Verification & scope

A deterministic bounded teaching model with a stipulated contract; it makes no claim of conformance to any published specification. 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 2026-09-29T14:49:45.749577+00:00.

Case digest / 02d909f6345f5785f8547ef917267ae1b3c2d83ddec65c31ea8283241d1f4de4