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FA-35576 / Tab interfaces / Open access

Reorder drop: selection after reorder · case 01

The tab workspace reports an incorrect selection after reorder.

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

ROOT CAUSE

The selection after reorder decision uses x['tabs'][x['index']] instead of x['active'].

THE FAILURE

The selection after reorder decision uses x['tabs'][x['index']] instead of x['active'].

Unsuccessful approach: The partial repair x['tabs'][min(x['boundary'],len(x['tabs'])-1)] still violates a workspace boundary or normal case.

Case contract

A strip drag uses pre-removal boundary indices: remove the dragged view, decrement later boundaries, clamp and insert while retaining active identity.

Why this case matters

Offline tab/panel workspace behavior; no browser or desktop framework is emulated.

1 / The failure

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

N = 1
observations = []
def solve(x):
    r0 = x['tabs'][x['index']]
    r1 = x['tabs'][:x['index']]+x['tabs'][x['index']+1:]
    r2 = x['boundary']-(x['boundary']>x['index'])
    r3 = x['boundary'] in (x['index'],x['index']+1)
    r4 = abs(x['boundary']-(x['boundary']>x['index'])-x['index'])
    r5 = x['tabs'][x['index']]
    return [r0,r1,r2,r3,r4,r5]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = {1: [({'tabs': ['a', 'b', 'c', 'd'], 'index': 1, 'boundary': 4, 'active': 'c'}, ['b', ['a', 'c', 'd'], 3, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd'], 'index': 1, 'boundary': 0, 'active': 'c'}, ['b', ['a', 'c', 'd'], 0, False, 1, 'c']), ({'tabs': ['a', 'b', 'c', 'd'], 'index': 1, 'boundary': 2, 'active': 'c'}, ['b', ['a', 'c', 'd'], 1, True, 0, 'c']), ({'tabs': ['a', 'b', 'c', 'd'], 'index': 0, 'boundary': 3, 'active': 'c'}, ['a', ['b', 'c', 'd'], 2, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd'], 'index': 3, 'boundary': 1, 'active': 'c'}, ['d', ['a', 'b', 'c'], 1, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd'], 'index': 1, 'boundary': 4, 'active': 'b'}, ['b', ['a', 'c', 'd'], 3, False, 2, 'b'])], 2: [({'tabs': ['a', 'b', 'c', 'd', 'background0'], 'index': 1, 'boundary': 4, 'active': 'c'}, ['b', ['a', 'c', 'd', 'background0'], 3, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0'], 'index': 1, 'boundary': 0, 'active': 'c'}, ['b', ['a', 'c', 'd', 'background0'], 0, False, 1, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0'], 'index': 1, 'boundary': 2, 'active': 'c'}, ['b', ['a', 'c', 'd', 'background0'], 1, True, 0, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0'], 'index': 0, 'boundary': 3, 'active': 'c'}, ['a', ['b', 'c', 'd', 'background0'], 2, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0'], 'index': 3, 'boundary': 1, 'active': 'c'}, ['d', ['a', 'b', 'c', 'background0'], 1, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0'], 'index': 1, 'boundary': 4, 'active': 'b'}, ['b', ['a', 'c', 'd', 'background0'], 3, False, 2, 'b'])], 3: [({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1'], 'index': 1, 'boundary': 4, 'active': 'c'}, ['b', ['a', 'c', 'd', 'background0', 'background1'], 3, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1'], 'index': 1, 'boundary': 0, 'active': 'c'}, ['b', ['a', 'c', 'd', 'background0', 'background1'], 0, False, 1, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1'], 'index': 1, 'boundary': 2, 'active': 'c'}, ['b', ['a', 'c', 'd', 'background0', 'background1'], 1, True, 0, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1'], 'index': 0, 'boundary': 3, 'active': 'c'}, ['a', ['b', 'c', 'd', 'background0', 'background1'], 2, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1'], 'index': 3, 'boundary': 1, 'active': 'c'}, ['d', ['a', 'b', 'c', 'background0', 'background1'], 1, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1'], 'index': 1, 'boundary': 4, 'active': 'b'}, ['b', ['a', 'c', 'd', 'background0', 'background1'], 3, False, 2, 'b'])], 4: [({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1', 'background2'], 'index': 1, 'boundary': 4, 'active': 'c'}, ['b', ['a', 'c', 'd', 'background0', 'background1', 'background2'], 3, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1', 'background2'], 'index': 1, 'boundary': 0, 'active': 'c'}, ['b', ['a', 'c', 'd', 'background0', 'background1', 'background2'], 0, False, 1, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1', 'background2'], 'index': 1, 'boundary': 2, 'active': 'c'}, ['b', ['a', 'c', 'd', 'background0', 'background1', 'background2'], 1, True, 0, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1', 'background2'], 'index': 0, 'boundary': 3, 'active': 'c'}, ['a', ['b', 'c', 'd', 'background0', 'background1', 'background2'], 2, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1', 'background2'], 'index': 3, 'boundary': 1, 'active': 'c'}, ['d', ['a', 'b', 'c', 'background0', 'background1', 'background2'], 1, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1', 'background2'], 'index': 1, 'boundary': 4, 'active': 'b'}, ['b', ['a', 'c', 'd', 'background0', 'background1', 'background2'], 3, False, 2, 'b'])], 5: [({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1', 'background2', 'background3'], 'index': 1, 'boundary': 4, 'active': 'c'}, ['b', ['a', 'c', 'd', 'background0', 'background1', 'background2', 'background3'], 3, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1', 'background2', 'background3'], 'index': 1, 'boundary': 0, 'active': 'c'}, ['b', ['a', 'c', 'd', 'background0', 'background1', 'background2', 'background3'], 0, False, 1, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1', 'background2', 'background3'], 'index': 1, 'boundary': 2, 'active': 'c'}, ['b', ['a', 'c', 'd', 'background0', 'background1', 'background2', 'background3'], 1, True, 0, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1', 'background2', 'background3'], 'index': 0, 'boundary': 3, 'active': 'c'}, ['a', ['b', 'c', 'd', 'background0', 'background1', 'background2', 'background3'], 2, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1', 'background2', 'background3'], 'index': 3, 'boundary': 1, 'active': 'c'}, ['d', ['a', 'b', 'c', 'background0', 'background1', 'background2', 'background3'], 1, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1', 'background2', 'background3'], 'index': 1, 'boundary': 4, 'active': 'b'}, ['b', ['a', 'c', 'd', 'background0', 'background1', 'background2', 'background3'], 3, False, 2, 'b'])]}
for i, (inputs, expected) in enumerate(fixtures[N]):
    check("workspace regression "+str(i), solve(inputs), 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
workspace regression 0['b', ['a', 'c', 'd'], 3, False, 2, 'b']['b', ['a', 'c', 'd'], 3, False, 2, 'c']Failed
workspace regression 1['b', ['a', 'c', 'd'], 0, False, 1, 'b']['b', ['a', 'c', 'd'], 0, False, 1, 'c']Failed
workspace regression 2['b', ['a', 'c', 'd'], 1, True, 0, 'b']['b', ['a', 'c', 'd'], 1, True, 0, 'c']Failed
workspace regression 3['a', ['b', 'c', 'd'], 2, False, 2, 'a']['a', ['b', 'c', 'd'], 2, False, 2, 'c']Failed
workspace regression 4['d', ['a', 'b', 'c'], 1, False, 2, 'd']['d', ['a', 'b', 'c'], 1, False, 2, 'c']Failed
workspace regression 5['b', ['a', 'c', 'd'], 3, False, 2, 'b']['b', ['a', 'c', 'd'], 3, False, 2, 'b']Passed

SHA-256 / 7a26dbb5b381a9fdae6b44df6e0e455c1e7bc8c26a2d863d4228090b69a44d8d

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(x):
    r0 = x['tabs'][x['index']]
    r1 = x['tabs'][:x['index']]+x['tabs'][x['index']+1:]
    r2 = x['boundary']-(x['boundary']>x['index'])
    r3 = x['boundary'] in (x['index'],x['index']+1)
    r4 = abs(x['boundary']-(x['boundary']>x['index'])-x['index'])
    r5 = x['tabs'][min(x['boundary'],len(x['tabs'])-1)]
    return [r0,r1,r2,r3,r4,r5]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = {1: [({'tabs': ['a', 'b', 'c', 'd'], 'index': 1, 'boundary': 4, 'active': 'c'}, ['b', ['a', 'c', 'd'], 3, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd'], 'index': 1, 'boundary': 0, 'active': 'c'}, ['b', ['a', 'c', 'd'], 0, False, 1, 'c']), ({'tabs': ['a', 'b', 'c', 'd'], 'index': 1, 'boundary': 2, 'active': 'c'}, ['b', ['a', 'c', 'd'], 1, True, 0, 'c']), ({'tabs': ['a', 'b', 'c', 'd'], 'index': 0, 'boundary': 3, 'active': 'c'}, ['a', ['b', 'c', 'd'], 2, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd'], 'index': 3, 'boundary': 1, 'active': 'c'}, ['d', ['a', 'b', 'c'], 1, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd'], 'index': 1, 'boundary': 4, 'active': 'b'}, ['b', ['a', 'c', 'd'], 3, False, 2, 'b'])], 2: [({'tabs': ['a', 'b', 'c', 'd', 'background0'], 'index': 1, 'boundary': 4, 'active': 'c'}, ['b', ['a', 'c', 'd', 'background0'], 3, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0'], 'index': 1, 'boundary': 0, 'active': 'c'}, ['b', ['a', 'c', 'd', 'background0'], 0, False, 1, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0'], 'index': 1, 'boundary': 2, 'active': 'c'}, ['b', ['a', 'c', 'd', 'background0'], 1, True, 0, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0'], 'index': 0, 'boundary': 3, 'active': 'c'}, ['a', ['b', 'c', 'd', 'background0'], 2, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0'], 'index': 3, 'boundary': 1, 'active': 'c'}, ['d', ['a', 'b', 'c', 'background0'], 1, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0'], 'index': 1, 'boundary': 4, 'active': 'b'}, ['b', ['a', 'c', 'd', 'background0'], 3, False, 2, 'b'])], 3: [({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1'], 'index': 1, 'boundary': 4, 'active': 'c'}, ['b', ['a', 'c', 'd', 'background0', 'background1'], 3, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1'], 'index': 1, 'boundary': 0, 'active': 'c'}, ['b', ['a', 'c', 'd', 'background0', 'background1'], 0, False, 1, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1'], 'index': 1, 'boundary': 2, 'active': 'c'}, ['b', ['a', 'c', 'd', 'background0', 'background1'], 1, True, 0, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1'], 'index': 0, 'boundary': 3, 'active': 'c'}, ['a', ['b', 'c', 'd', 'background0', 'background1'], 2, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1'], 'index': 3, 'boundary': 1, 'active': 'c'}, ['d', ['a', 'b', 'c', 'background0', 'background1'], 1, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1'], 'index': 1, 'boundary': 4, 'active': 'b'}, ['b', ['a', 'c', 'd', 'background0', 'background1'], 3, False, 2, 'b'])], 4: [({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1', 'background2'], 'index': 1, 'boundary': 4, 'active': 'c'}, ['b', ['a', 'c', 'd', 'background0', 'background1', 'background2'], 3, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1', 'background2'], 'index': 1, 'boundary': 0, 'active': 'c'}, ['b', ['a', 'c', 'd', 'background0', 'background1', 'background2'], 0, False, 1, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1', 'background2'], 'index': 1, 'boundary': 2, 'active': 'c'}, ['b', ['a', 'c', 'd', 'background0', 'background1', 'background2'], 1, True, 0, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1', 'background2'], 'index': 0, 'boundary': 3, 'active': 'c'}, ['a', ['b', 'c', 'd', 'background0', 'background1', 'background2'], 2, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1', 'background2'], 'index': 3, 'boundary': 1, 'active': 'c'}, ['d', ['a', 'b', 'c', 'background0', 'background1', 'background2'], 1, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1', 'background2'], 'index': 1, 'boundary': 4, 'active': 'b'}, ['b', ['a', 'c', 'd', 'background0', 'background1', 'background2'], 3, False, 2, 'b'])], 5: [({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1', 'background2', 'background3'], 'index': 1, 'boundary': 4, 'active': 'c'}, ['b', ['a', 'c', 'd', 'background0', 'background1', 'background2', 'background3'], 3, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1', 'background2', 'background3'], 'index': 1, 'boundary': 0, 'active': 'c'}, ['b', ['a', 'c', 'd', 'background0', 'background1', 'background2', 'background3'], 0, False, 1, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1', 'background2', 'background3'], 'index': 1, 'boundary': 2, 'active': 'c'}, ['b', ['a', 'c', 'd', 'background0', 'background1', 'background2', 'background3'], 1, True, 0, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1', 'background2', 'background3'], 'index': 0, 'boundary': 3, 'active': 'c'}, ['a', ['b', 'c', 'd', 'background0', 'background1', 'background2', 'background3'], 2, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1', 'background2', 'background3'], 'index': 3, 'boundary': 1, 'active': 'c'}, ['d', ['a', 'b', 'c', 'background0', 'background1', 'background2', 'background3'], 1, False, 2, 'c']), ({'tabs': ['a', 'b', 'c', 'd', 'background0', 'background1', 'background2', 'background3'], 'index': 1, 'boundary': 4, 'active': 'b'}, ['b', ['a', 'c', 'd', 'background0', 'background1', 'background2', 'background3'], 3, False, 2, 'b'])]}
for i, (inputs, expected) in enumerate(fixtures[N]):
    check("workspace regression "+str(i), solve(inputs), 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
workspace regression 0['b', ['a', 'c', 'd'], 3, False, 2, 'd']['b', ['a', 'c', 'd'], 3, False, 2, 'c']Failed
workspace regression 1['b', ['a', 'c', 'd'], 0, False, 1, 'a']['b', ['a', 'c', 'd'], 0, False, 1, 'c']Failed
workspace regression 2['b', ['a', 'c', 'd'], 1, True, 0, 'c']['b', ['a', 'c', 'd'], 1, True, 0, 'c']Passed
workspace regression 3['a', ['b', 'c', 'd'], 2, False, 2, 'd']['a', ['b', 'c', 'd'], 2, False, 2, 'c']Failed
workspace regression 4['d', ['a', 'b', 'c'], 1, False, 2, 'b']['d', ['a', 'b', 'c'], 1, False, 2, 'c']Failed
workspace regression 5['b', ['a', 'c', 'd'], 3, False, 2, 'd']['b', ['a', 'c', 'd'], 3, False, 2, 'b']Failed

SHA-256 / c82df4f4cc0f42d008cf9bef8e2ac3b402718647cb75a98aa33a21b4969610cb

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.

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Verification & scope

Finite stipulated workspace snapshots only. Independent result fields describe observable obligations, not a full UI runtime. 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 2026-09-29T14:42:43.024760+00:00.

Case digest / 2d05ff84a68cb8cba963fbdb619df0ab5dd276fbb1d2dbad39ce37fc1bb83e77