FA-21071 / Assistive announcements / Open access
Previous command jumps directly to oldest speech · case 01
The announcement trace violates the stated speech-history contract.
ROOT CAUSE
Fault site: cursor=max(0,cursor-1) is implemented as cursor=0
THE FAILURE
Fault site: cursor=max(0,cursor-1) is implemented as cursor=0
Unsuccessful approach: The attempted repair substitutes cursor=max(0,cursor-2) and still violates a regression oracle.
Case contract
History retains the last three delivered utterances [id,text], newest last. Deliver same ID replaces its prior record and moves it newest. Replay speaks selected history text without adding history. Previous walks a separate cursor newest to oldest and clamps at oldest. Deliver resets cursor to newest. Forget deletes one ID and resets cursor. Clear removes history without changing spoken output. Limit clamps to at least one and trims oldest. Report spoken and history.
Why this case matters
Deterministic controlled model of assistive announcement delivery.
1 / The failure
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(events):
history=[]; out=[]; cursor=0; limit=3
for e in events:
if e[0]=='deliver':
history=[x for x in history if x[0]!=e[1]]
history.append([e[1],e[2]])
history=history[-limit:]
cursor=len(history)
out.append(e[2])
elif e[0]=='replay':
match=next((x for x in history if x[0]==e[1]),None)
if match: out.append(match[1])
elif e[0]=='previous' and history:
cursor=0
out.append(history[cursor][1])
elif e[0]=='forget': history=[x for x in history if x[0]!=e[1]]; cursor=len(history)
elif e[0]=='clear': history=[]; cursor=0
elif e[0]=='limit': limit=max(1,e[1]); history=history[-limit:]; cursor=len(history)
return [out,history,cursor]
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = ["[['deliver',str(i),'word'*N+str(i)] for i in range(N+4)]+[['previous'],['previous'],['previous'],['previous']]", "[['deliver','a','same'*N],['deliver','b','same'*N]]", "[['deliver','a','same'*N],['deliver','b','same'*N],['deliver','a','new'],['replay','a']]", "[['deliver','a','alpha'*N],['deliver','b','beta'],['previous'],['deliver','c','gamma'],['previous']]", "[['deliver','a','alpha'*N],['deliver','b','beta'],['deliver','c','gamma'],['forget','a'],['previous']]", "[['deliver','a','alpha'*N],['clear'],['replay','a']]", "[['deliver','a','a'*N],['deliver','b','b'],['deliver','c','c'],['limit',1],['previous']]", '[]']
expected = {1: [[['word0', 'word1', 'word2', 'word3', 'word4', 'word4', 'word3', 'word2', 'word2'], [['2', 'word2'], ['3', 'word3'], ['4', 'word4']], 0], [['same', 'same'], [['a', 'same'], ['b', 'same']], 2], [['same', 'same', 'new', 'new'], [['b', 'same'], ['a', 'new']], 2], [['alpha', 'beta', 'beta', 'gamma', 'gamma'], [['a', 'alpha'], ['b', 'beta'], ['c', 'gamma']], 2], [['alpha', 'beta', 'gamma', 'gamma'], [['b', 'beta'], ['c', 'gamma']], 1], [['alpha'], [], 0], [['a', 'b', 'c', 'c'], [['c', 'c']], 0], [[], [], 0]], 2: [[['wordword0', 'wordword1', 'wordword2', 'wordword3', 'wordword4', 'wordword5', 'wordword5', 'wordword4', 'wordword3', 'wordword3'], [['3', 'wordword3'], ['4', 'wordword4'], ['5', 'wordword5']], 0], [['samesame', 'samesame'], [['a', 'samesame'], ['b', 'samesame']], 2], [['samesame', 'samesame', 'new', 'new'], [['b', 'samesame'], ['a', 'new']], 2], [['alphaalpha', 'beta', 'beta', 'gamma', 'gamma'], [['a', 'alphaalpha'], ['b', 'beta'], ['c', 'gamma']], 2], [['alphaalpha', 'beta', 'gamma', 'gamma'], [['b', 'beta'], ['c', 'gamma']], 1], [['alphaalpha'], [], 0], [['aa', 'b', 'c', 'c'], [['c', 'c']], 0], [[], [], 0]], 3: [[['wordwordword0', 'wordwordword1', 'wordwordword2', 'wordwordword3', 'wordwordword4', 'wordwordword5', 'wordwordword6', 'wordwordword6', 'wordwordword5', 'wordwordword4', 'wordwordword4'], [['4', 'wordwordword4'], ['5', 'wordwordword5'], ['6', 'wordwordword6']], 0], [['samesamesame', 'samesamesame'], [['a', 'samesamesame'], ['b', 'samesamesame']], 2], [['samesamesame', 'samesamesame', 'new', 'new'], [['b', 'samesamesame'], ['a', 'new']], 2], [['alphaalphaalpha', 'beta', 'beta', 'gamma', 'gamma'], [['a', 'alphaalphaalpha'], ['b', 'beta'], ['c', 'gamma']], 2], [['alphaalphaalpha', 'beta', 'gamma', 'gamma'], [['b', 'beta'], ['c', 'gamma']], 1], [['alphaalphaalpha'], [], 0], [['aaa', 'b', 'c', 'c'], [['c', 'c']], 0], [[], [], 0]], 4: [[['wordwordwordword0', 'wordwordwordword1', 'wordwordwordword2', 'wordwordwordword3', 'wordwordwordword4', 'wordwordwordword5', 'wordwordwordword6', 'wordwordwordword7', 'wordwordwordword7', 'wordwordwordword6', 'wordwordwordword5', 'wordwordwordword5'], [['5', 'wordwordwordword5'], ['6', 'wordwordwordword6'], ['7', 'wordwordwordword7']], 0], [['samesamesamesame', 'samesamesamesame'], [['a', 'samesamesamesame'], ['b', 'samesamesamesame']], 2], [['samesamesamesame', 'samesamesamesame', 'new', 'new'], [['b', 'samesamesamesame'], ['a', 'new']], 2], [['alphaalphaalphaalpha', 'beta', 'beta', 'gamma', 'gamma'], [['a', 'alphaalphaalphaalpha'], ['b', 'beta'], ['c', 'gamma']], 2], [['alphaalphaalphaalpha', 'beta', 'gamma', 'gamma'], [['b', 'beta'], ['c', 'gamma']], 1], [['alphaalphaalphaalpha'], [], 0], [['aaaa', 'b', 'c', 'c'], [['c', 'c']], 0], [[], [], 0]], 5: [[['wordwordwordwordword0', 'wordwordwordwordword1', 'wordwordwordwordword2', 'wordwordwordwordword3', 'wordwordwordwordword4', 'wordwordwordwordword5', 'wordwordwordwordword6', 'wordwordwordwordword7', 'wordwordwordwordword8', 'wordwordwordwordword8', 'wordwordwordwordword7', 'wordwordwordwordword6', 'wordwordwordwordword6'], [['6', 'wordwordwordwordword6'], ['7', 'wordwordwordwordword7'], ['8', 'wordwordwordwordword8']], 0], [['samesamesamesamesame', 'samesamesamesamesame'], [['a', 'samesamesamesamesame'], ['b', 'samesamesamesamesame']], 2], [['samesamesamesamesame', 'samesamesamesamesame', 'new', 'new'], [['b', 'samesamesamesamesame'], ['a', 'new']], 2], [['alphaalphaalphaalphaalpha', 'beta', 'beta', 'gamma', 'gamma'], [['a', 'alphaalphaalphaalphaalpha'], ['b', 'beta'], ['c', 'gamma']], 2], [['alphaalphaalphaalphaalpha', 'beta', 'gamma', 'gamma'], [['b', 'beta'], ['c', 'gamma']], 1], [['alphaalphaalphaalphaalpha'], [], 0], [['aaaaa', 'b', 'c', 'c'], [['c', 'c']], 0], [[], [], 0]]}[N]
for i, expression in enumerate(fixtures):
check("trace-"+str(i+1), solve(eval(expression)), expected[i])
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 |
|---|---|---|---|
| trace-1 | [['word0', 'word1', 'word2', 'word3', 'word4', 'word2', 'word2', 'word2', 'word2'], [['2', 'word2'], ['3', 'word3'], ['4', 'word4']], 0] | [['word0', 'word1', 'word2', 'word3', 'word4', 'word4', 'word3', 'word2', 'word2'], [['2', 'word2'], ['3', 'word3'], ['4', 'word4']], 0] | Failed |
| trace-2 | [['same', 'same'], [['a', 'same'], ['b', 'same']], 2] | [['same', 'same'], [['a', 'same'], ['b', 'same']], 2] | Passed |
| trace-3 | [['same', 'same', 'new', 'new'], [['b', 'same'], ['a', 'new']], 2] | [['same', 'same', 'new', 'new'], [['b', 'same'], ['a', 'new']], 2] | Passed |
| trace-4 | [['alpha', 'beta', 'alpha', 'gamma', 'alpha'], [['a', 'alpha'], ['b', 'beta'], ['c', 'gamma']], 0] | [['alpha', 'beta', 'beta', 'gamma', 'gamma'], [['a', 'alpha'], ['b', 'beta'], ['c', 'gamma']], 2] | Failed |
| trace-5 | [['alpha', 'beta', 'gamma', 'beta'], [['b', 'beta'], ['c', 'gamma']], 0] | [['alpha', 'beta', 'gamma', 'gamma'], [['b', 'beta'], ['c', 'gamma']], 1] | Failed |
| trace-6 | [['alpha'], [], 0] | [['alpha'], [], 0] | Passed |
| trace-7 | [['a', 'b', 'c', 'c'], [['c', 'c']], 0] | [['a', 'b', 'c', 'c'], [['c', 'c']], 0] | Passed |
| trace-8 | [[], [], 0] | [[], [], 0] | Passed |
SHA-256 / c8b72b86ba567cc903fab104879e4f8cff681c2f6204eb1786d893640ff20780
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(events):
history=[]; out=[]; cursor=0; limit=3
for e in events:
if e[0]=='deliver':
history=[x for x in history if x[0]!=e[1]]
history.append([e[1],e[2]])
history=history[-limit:]
cursor=len(history)
out.append(e[2])
elif e[0]=='replay':
match=next((x for x in history if x[0]==e[1]),None)
if match: out.append(match[1])
elif e[0]=='previous' and history:
cursor=max(0,cursor-2)
out.append(history[cursor][1])
elif e[0]=='forget': history=[x for x in history if x[0]!=e[1]]; cursor=len(history)
elif e[0]=='clear': history=[]; cursor=0
elif e[0]=='limit': limit=max(1,e[1]); history=history[-limit:]; cursor=len(history)
return [out,history,cursor]
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = ["[['deliver',str(i),'word'*N+str(i)] for i in range(N+4)]+[['previous'],['previous'],['previous'],['previous']]", "[['deliver','a','same'*N],['deliver','b','same'*N]]", "[['deliver','a','same'*N],['deliver','b','same'*N],['deliver','a','new'],['replay','a']]", "[['deliver','a','alpha'*N],['deliver','b','beta'],['previous'],['deliver','c','gamma'],['previous']]", "[['deliver','a','alpha'*N],['deliver','b','beta'],['deliver','c','gamma'],['forget','a'],['previous']]", "[['deliver','a','alpha'*N],['clear'],['replay','a']]", "[['deliver','a','a'*N],['deliver','b','b'],['deliver','c','c'],['limit',1],['previous']]", '[]']
expected = {1: [[['word0', 'word1', 'word2', 'word3', 'word4', 'word4', 'word3', 'word2', 'word2'], [['2', 'word2'], ['3', 'word3'], ['4', 'word4']], 0], [['same', 'same'], [['a', 'same'], ['b', 'same']], 2], [['same', 'same', 'new', 'new'], [['b', 'same'], ['a', 'new']], 2], [['alpha', 'beta', 'beta', 'gamma', 'gamma'], [['a', 'alpha'], ['b', 'beta'], ['c', 'gamma']], 2], [['alpha', 'beta', 'gamma', 'gamma'], [['b', 'beta'], ['c', 'gamma']], 1], [['alpha'], [], 0], [['a', 'b', 'c', 'c'], [['c', 'c']], 0], [[], [], 0]], 2: [[['wordword0', 'wordword1', 'wordword2', 'wordword3', 'wordword4', 'wordword5', 'wordword5', 'wordword4', 'wordword3', 'wordword3'], [['3', 'wordword3'], ['4', 'wordword4'], ['5', 'wordword5']], 0], [['samesame', 'samesame'], [['a', 'samesame'], ['b', 'samesame']], 2], [['samesame', 'samesame', 'new', 'new'], [['b', 'samesame'], ['a', 'new']], 2], [['alphaalpha', 'beta', 'beta', 'gamma', 'gamma'], [['a', 'alphaalpha'], ['b', 'beta'], ['c', 'gamma']], 2], [['alphaalpha', 'beta', 'gamma', 'gamma'], [['b', 'beta'], ['c', 'gamma']], 1], [['alphaalpha'], [], 0], [['aa', 'b', 'c', 'c'], [['c', 'c']], 0], [[], [], 0]], 3: [[['wordwordword0', 'wordwordword1', 'wordwordword2', 'wordwordword3', 'wordwordword4', 'wordwordword5', 'wordwordword6', 'wordwordword6', 'wordwordword5', 'wordwordword4', 'wordwordword4'], [['4', 'wordwordword4'], ['5', 'wordwordword5'], ['6', 'wordwordword6']], 0], [['samesamesame', 'samesamesame'], [['a', 'samesamesame'], ['b', 'samesamesame']], 2], [['samesamesame', 'samesamesame', 'new', 'new'], [['b', 'samesamesame'], ['a', 'new']], 2], [['alphaalphaalpha', 'beta', 'beta', 'gamma', 'gamma'], [['a', 'alphaalphaalpha'], ['b', 'beta'], ['c', 'gamma']], 2], [['alphaalphaalpha', 'beta', 'gamma', 'gamma'], [['b', 'beta'], ['c', 'gamma']], 1], [['alphaalphaalpha'], [], 0], [['aaa', 'b', 'c', 'c'], [['c', 'c']], 0], [[], [], 0]], 4: [[['wordwordwordword0', 'wordwordwordword1', 'wordwordwordword2', 'wordwordwordword3', 'wordwordwordword4', 'wordwordwordword5', 'wordwordwordword6', 'wordwordwordword7', 'wordwordwordword7', 'wordwordwordword6', 'wordwordwordword5', 'wordwordwordword5'], [['5', 'wordwordwordword5'], ['6', 'wordwordwordword6'], ['7', 'wordwordwordword7']], 0], [['samesamesamesame', 'samesamesamesame'], [['a', 'samesamesamesame'], ['b', 'samesamesamesame']], 2], [['samesamesamesame', 'samesamesamesame', 'new', 'new'], [['b', 'samesamesamesame'], ['a', 'new']], 2], [['alphaalphaalphaalpha', 'beta', 'beta', 'gamma', 'gamma'], [['a', 'alphaalphaalphaalpha'], ['b', 'beta'], ['c', 'gamma']], 2], [['alphaalphaalphaalpha', 'beta', 'gamma', 'gamma'], [['b', 'beta'], ['c', 'gamma']], 1], [['alphaalphaalphaalpha'], [], 0], [['aaaa', 'b', 'c', 'c'], [['c', 'c']], 0], [[], [], 0]], 5: [[['wordwordwordwordword0', 'wordwordwordwordword1', 'wordwordwordwordword2', 'wordwordwordwordword3', 'wordwordwordwordword4', 'wordwordwordwordword5', 'wordwordwordwordword6', 'wordwordwordwordword7', 'wordwordwordwordword8', 'wordwordwordwordword8', 'wordwordwordwordword7', 'wordwordwordwordword6', 'wordwordwordwordword6'], [['6', 'wordwordwordwordword6'], ['7', 'wordwordwordwordword7'], ['8', 'wordwordwordwordword8']], 0], [['samesamesamesamesame', 'samesamesamesamesame'], [['a', 'samesamesamesamesame'], ['b', 'samesamesamesamesame']], 2], [['samesamesamesamesame', 'samesamesamesamesame', 'new', 'new'], [['b', 'samesamesamesamesame'], ['a', 'new']], 2], [['alphaalphaalphaalphaalpha', 'beta', 'beta', 'gamma', 'gamma'], [['a', 'alphaalphaalphaalphaalpha'], ['b', 'beta'], ['c', 'gamma']], 2], [['alphaalphaalphaalphaalpha', 'beta', 'gamma', 'gamma'], [['b', 'beta'], ['c', 'gamma']], 1], [['alphaalphaalphaalphaalpha'], [], 0], [['aaaaa', 'b', 'c', 'c'], [['c', 'c']], 0], [[], [], 0]]}[N]
for i, expression in enumerate(fixtures):
check("trace-"+str(i+1), solve(eval(expression)), expected[i])
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 |
|---|---|---|---|
| trace-1 | [['word0', 'word1', 'word2', 'word3', 'word4', 'word3', 'word2', 'word2', 'word2'], [['2', 'word2'], ['3', 'word3'], ['4', 'word4']], 0] | [['word0', 'word1', 'word2', 'word3', 'word4', 'word4', 'word3', 'word2', 'word2'], [['2', 'word2'], ['3', 'word3'], ['4', 'word4']], 0] | Failed |
| trace-2 | [['same', 'same'], [['a', 'same'], ['b', 'same']], 2] | [['same', 'same'], [['a', 'same'], ['b', 'same']], 2] | Passed |
| trace-3 | [['same', 'same', 'new', 'new'], [['b', 'same'], ['a', 'new']], 2] | [['same', 'same', 'new', 'new'], [['b', 'same'], ['a', 'new']], 2] | Passed |
| trace-4 | [['alpha', 'beta', 'alpha', 'gamma', 'beta'], [['a', 'alpha'], ['b', 'beta'], ['c', 'gamma']], 1] | [['alpha', 'beta', 'beta', 'gamma', 'gamma'], [['a', 'alpha'], ['b', 'beta'], ['c', 'gamma']], 2] | Failed |
| trace-5 | [['alpha', 'beta', 'gamma', 'beta'], [['b', 'beta'], ['c', 'gamma']], 0] | [['alpha', 'beta', 'gamma', 'gamma'], [['b', 'beta'], ['c', 'gamma']], 1] | Failed |
| trace-6 | [['alpha'], [], 0] | [['alpha'], [], 0] | Passed |
| trace-7 | [['a', 'b', 'c', 'c'], [['c', 'c']], 0] | [['a', 'b', 'c', 'c'], [['c', 'c']], 0] | Passed |
| trace-8 | [[], [], 0] | [[], [], 0] | Passed |
SHA-256 / 87c414bf8d84e5b2b971bce60d49bc9a1d44d1a41dbdade42d2f9b9c2558c335
HELD IN THE MEMBER ARCHIVE
The verified repair and its recorded checks are member-only.
This mechanism has 8 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.
Sign in to the archive ↗Verification & scope
Stipulated bounded policy, not a browser, speech engine, platform API, or standards conformance claim. 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 2026-09-29T14:40:25.269453+00:00.
Case digest / 29d506d9c0dc53aad895581e1ea1f8c8a0987dff0d0961319dd26ef803d9b385