Anthropic: Claude Fable 5

anthropic/claude-fable-5 · anthropic · context 1 000 000 · in $10.00/1M · out $50.00/1M

Global Index

816

95% CI [728–904] · index v0.2.0

Per-domain scores

Domain	Score (95% CI)		Accuracy (IRT)	Consistency	Calibration	Contam. Δ	p50	$/1k
code	816 [728–904]		0.697	1.00	0.98	0.000	3.4s	$19.55

Every answer, every test

Full transparency: the model's latest graded answer on every instantiated item of the current index version. Answer keys never leave the server; anchor-item prompts are withheld to protect the longitudinal subset.

code 15/30 correct

wrongcode.trace.js-v1conf — · 3.3s · $0.002 · 3 tok

question

What does this JavaScript program log?

```js
const arr = [4, 5, 6, 7, 8, 9, 10, 11, 12, 13];
const out = arr
  .map(n => n * 3)
  .filter(n => n % 5 === 0)
  .reduce((a, b) => a + b, 0);
console.log(out);
```

End your reply with exactly two plain-text lines (no markdown, no extra text after them):
ANSWER: <your final answer only>
CONFIDENCE: <integer 0-100, how confident you are that your answer is correct>

model answer: (none extracted)

correctcode.trace.nested-v1conf 98% · 4.2s · $0.032 · 598 tok

question

Trace this Python program exactly. What does it print?

```python
total = 0
for i in range(1, 8):
    for j in range(1, 8):
        if j == 5 and i % 2 == 0:
            break
        if (i + j) % 2 == 0:
            continue
        total += i * 2 + j
print(total)
```

End your reply with exactly two plain-text lines (no markdown, no extra text after them):
ANSWER: <your final answer only>
CONFIDENCE: <integer 0-100, how confident you are that your answer is correct>

model answer: 204

correctcode.trace.python-v1conf 99% · 2.6s · $0.032 · 604 tok

question

Trace the following Python code and give its exact output.

```python
total = 0
v = 2
while total + v <= 95:
    if v % 4 != 0:
        total += v
    v += 9
print(total)
```

End your reply with exactly two plain-text lines (no markdown, no extra text after them):
ANSWER: <your final answer only>
CONFIDENCE: <integer 0-100, how confident you are that your answer is correct>

model answer: 80

correctcode.trace.nested-v1conf 97% · 3.6s · $0.053 · 1021 tok

question

Trace this Python program exactly. What does it print?

```python
total = 0
for i in range(1, 8):
    for j in range(1, 8):
        if j == 6 and i % 2 == 0:
            break
        if (i + j) % 3 == 0:
            continue
        total += i * 4 + j
print(total)
```

End your reply with exactly two plain-text lines (no markdown, no extra text after them):
ANSWER: <your final answer only>
CONFIDENCE: <integer 0-100, how confident you are that your answer is correct>

model answer: 575

correctcode.trace.js-v1conf 99% · 4.1s · $0.016 · 279 tok

question

Evaluate the following JavaScript. What number is logged to the console?

```js
const arr = [2, 3, 4, 5, 6, 7, 8, 9];
const out = arr
  .map(n => n * 2)
  .filter(n => n % 3 === 0)
  .reduce((a, b) => a + b, 0);
console.log(out);
```

End your reply with exactly two plain-text lines (no markdown, no extra text after them):
ANSWER: <your final answer only>
CONFIDENCE: <integer 0-100, how confident you are that your answer is correct>

model answer: 36

wrongcode.trace.python-v1conf — · 3.4s · $0.002 · 3 tok

question

What does this Python program print?

```python
total = 0
v = 6
while total + v <= 111:
    if v % 5 != 0:
        total += v
    v += 3
print(total)
```

End your reply with exactly two plain-text lines (no markdown, no extra text after them):
ANSWER: <your final answer only>
CONFIDENCE: <integer 0-100, how confident you are that your answer is correct>

model answer: (none extracted)

correctcode.trace.nested-v1conf 98% · 4.1s · $0.036 · 678 tok

question

Trace this Python program exactly. What does it print?

```python
total = 0
for i in range(1, 8):
    for j in range(1, 8):
        if j == 6 and i % 2 == 0:
            break
        if (i + j) % 2 == 0:
            continue
        total += i * 4 + j
print(total)
```

End your reply with exactly two plain-text lines (no markdown, no extra text after them):
ANSWER: <your final answer only>
CONFIDENCE: <integer 0-100, how confident you are that your answer is correct>

model answer: 411

wrongcode.trace.js-v1conf — · 5.0s · $0.002 · 2 tok

question

What does this JavaScript program log?

```js
const arr = [6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17];
const out = arr
  .map(n => n * 3)
  .filter(n => n % 2 === 0)
  .reduce((a, b) => a + b, 0);
console.log(out);
```

End your reply with exactly two plain-text lines (no markdown, no extra text after them):
ANSWER: <your final answer only>
CONFIDENCE: <integer 0-100, how confident you are that your answer is correct>

model answer: (none extracted)

correctcode.trace.python-v1conf 99% · 3.0s · $0.023 · 434 tok

question

Trace the following Python code and give its exact output.

```python
total = 0
v = 5
while total + v <= 86:
    if v % 6 != 0:
        total += v
    v += 7
print(total)
```

End your reply with exactly two plain-text lines (no markdown, no extra text after them):
ANSWER: <your final answer only>
CONFIDENCE: <integer 0-100, how confident you are that your answer is correct>

model answer: 83

correctcode.trace.nested-v1conf 98% · 2.8s · $0.032 · 606 tok

question

Trace this Python program exactly. What does it print?

```python
total = 0
for i in range(1, 6):
    for j in range(1, 7):
        if j == 3 and i % 2 == 0:
            break
        if (i + j) % 2 == 0:
            continue
        total += i * 2 + j
print(total)
```

End your reply with exactly two plain-text lines (no markdown, no extra text after them):
ANSWER: <your final answer only>
CONFIDENCE: <integer 0-100, how confident you are that your answer is correct>

model answer: 104

wrongcode.trace.js-v1conf — · 3.0s · $0.002 · 2 tok

question

What does this JavaScript program log?

```js
const arr = [2, 3, 4, 5, 6, 7, 8, 9, 10];
const out = arr
  .map(n => n * 5)
  .filter(n => n % 4 === 0)
  .reduce((a, b) => a + b, 0);
console.log(out);
```

End your reply with exactly two plain-text lines (no markdown, no extra text after them):
ANSWER: <your final answer only>
CONFIDENCE: <integer 0-100, how confident you are that your answer is correct>

model answer: (none extracted)

correctcode.trace.nested-v1conf 98% · 4.2s · $0.066 · 1278 tok

question

Trace this Python program exactly. What does it print?

```python
total = 0
for i in range(1, 8):
    for j in range(1, 6):
        if j == 3 and i % 2 == 0:
            break
        if (i + j) % 3 == 0:
            continue
        total += i * 2 + j
print(total)
```

End your reply with exactly two plain-text lines (no markdown, no extra text after them):
ANSWER: <your final answer only>
CONFIDENCE: <integer 0-100, how confident you are that your answer is correct>

model answer: 182

wrongcode.trace.python-v1conf — · 2.9s · $0.002 · 2 tok

question

Execute this Python snippet mentally. What is printed?

```python
total = 0
v = 10
while total + v <= 116:
    if v % 5 != 0:
        total += v
    v += 2
print(total)
```

End your reply with exactly two plain-text lines (no markdown, no extra text after them):
ANSWER: <your final answer only>
CONFIDENCE: <integer 0-100, how confident you are that your answer is correct>

model answer: (none extracted)

wrongcode.trace.js-v1conf — · 3.8s · $0.003 · 9 tok

question

Evaluate the following JavaScript. What number is logged to the console?

```js
const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11];
const out = arr
  .map(n => n * 5)
  .filter(n => n % 5 === 0)
  .reduce((a, b) => a + b, 0);
console.log(out);
```

End your reply with exactly two plain-text lines (no markdown, no extra text after them):
ANSWER: <your final answer only>
CONFIDENCE: <integer 0-100, how confident you are that your answer is correct>

model answer: (none extracted)

correctcode.trace.python-v1conf 99% · 2.8s · $0.018 · 333 tok

question

Execute this Python snippet mentally. What is printed?

```python
total = 0
v = 6
while total + v <= 59:
    if v % 5 != 0:
        total += v
    v += 5
print(total)
```

End your reply with exactly two plain-text lines (no markdown, no extra text after them):
ANSWER: <your final answer only>
CONFIDENCE: <integer 0-100, how confident you are that your answer is correct>

model answer: 54

correctcode.trace.nested-v1conf 98% · 3.1s · $0.047 · 896 tok

question

Trace this Python program exactly. What does it print?

```python
total = 0
for i in range(1, 5):
    for j in range(1, 6):
        if j == 4 and i % 2 == 0:
            break
        if (i + j) % 3 == 0:
            continue
        total += i * 2 + j
print(total)
```

End your reply with exactly two plain-text lines (no markdown, no extra text after them):
ANSWER: <your final answer only>
CONFIDENCE: <integer 0-100, how confident you are that your answer is correct>

model answer: 83

wrongcode.trace.js-v1conf — · 8.3s · $0.002 · 3 tok

question

What does this JavaScript program log?

```js
const arr = [10, 11, 12, 13, 14, 15, 16, 17];
const out = arr
  .map(n => n * 2)
  .filter(n => n % 4 === 0)
  .reduce((a, b) => a + b, 0);
console.log(out);
```

End your reply with exactly two plain-text lines (no markdown, no extra text after them):
ANSWER: <your final answer only>
CONFIDENCE: <integer 0-100, how confident you are that your answer is correct>

model answer: (none extracted)

correctcode.trace.nested-v1conf 98% · 4.5s · $0.049 · 937 tok

question

Trace this Python program exactly. What does it print?

```python
total = 0
for i in range(1, 6):
    for j in range(1, 8):
        if j == 4 and i % 2 == 0:
            break
        if (i + j) % 3 == 0:
            continue
        total += i * 4 + j
print(total)
```

End your reply with exactly two plain-text lines (no markdown, no extra text after them):
ANSWER: <your final answer only>
CONFIDENCE: <integer 0-100, how confident you are that your answer is correct>

model answer: 273

wrongcode.trace.python-v1conf — · 3.3s · $0.002 · 2 tok

question

Execute this Python snippet mentally. What is printed?

```python
total = 0
v = 5
while total + v <= 103:
    if v % 7 != 0:
        total += v
    v += 4
print(total)
```

End your reply with exactly two plain-text lines (no markdown, no extra text after them):
ANSWER: <your final answer only>
CONFIDENCE: <integer 0-100, how confident you are that your answer is correct>

model answer: (none extracted)

wrongcode.trace.js-v1conf — · 3.7s · $0.002 · 2 tok

question

Evaluate the following JavaScript. What number is logged to the console?

```js
const arr = [3, 4, 5, 6, 7, 8];
const out = arr
  .map(n => n * 3)
  .filter(n => n % 4 === 0)
  .reduce((a, b) => a + b, 0);
console.log(out);
```

End your reply with exactly two plain-text lines (no markdown, no extra text after them):
ANSWER: <your final answer only>
CONFIDENCE: <integer 0-100, how confident you are that your answer is correct>

model answer: (none extracted)

correctcode.trace.nested-v1conf 98% · 3.2s · $0.049 · 936 tok

question

Trace this Python program exactly. What does it print?

```python
total = 0
for i in range(1, 8):
    for j in range(1, 5):
        if j == 3 and i % 2 == 0:
            break
        if (i + j) % 2 == 0:
            continue
        total += i * 3 + j
print(total)
```

End your reply with exactly two plain-text lines (no markdown, no extra text after them):
ANSWER: <your final answer only>
CONFIDENCE: <integer 0-100, how confident you are that your answer is correct>

model answer: 159

wrongcode.trace.python-v1conf — · 2.8s · $0.002 · 3 tok

question

What does this Python program print?

```python
total = 0
v = 7
while total + v <= 48:
    if v % 3 != 0:
        total += v
    v += 9
print(total)
```

End your reply with exactly two plain-text lines (no markdown, no extra text after them):
ANSWER: <your final answer only>
CONFIDENCE: <integer 0-100, how confident you are that your answer is correct>

model answer: (none extracted)

wrongcode.trace.js-v1conf — · 2.9s · $0.002 · 5 tok

question

What does this JavaScript program log?

```js
const arr = [5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15];
const out = arr
  .map(n => n * 5)
  .filter(n => n % 5 === 0)
  .reduce((a, b) => a + b, 0);
console.log(out);
```

End your reply with exactly two plain-text lines (no markdown, no extra text after them):
ANSWER: <your final answer only>
CONFIDENCE: <integer 0-100, how confident you are that your answer is correct>

model answer: (none extracted)

correctcode.trace.nested-v1conf 97% · 2.8s · $0.039 · 750 tok

question

Trace this Python program exactly. What does it print?

```python
total = 0
for i in range(1, 8):
    for j in range(1, 7):
        if j == 5 and i % 2 == 0:
            break
        if (i + j) % 2 == 0:
            continue
        total += i * 2 + j
print(total)
```

End your reply with exactly two plain-text lines (no markdown, no extra text after them):
ANSWER: <your final answer only>
CONFIDENCE: <integer 0-100, how confident you are that your answer is correct>

model answer: 204

wrongcode.trace.python-v1conf — · 3.6s · $0.002 · 2 tok

question

What does this Python program print?

```python
total = 0
v = 7
while total + v <= 61:
    if v % 4 != 0:
        total += v
    v += 4
print(total)
```

End your reply with exactly two plain-text lines (no markdown, no extra text after them):
ANSWER: <your final answer only>
CONFIDENCE: <integer 0-100, how confident you are that your answer is correct>

model answer: (none extracted)

wrongcode.trace.js-v1conf — · 4.1s · $0.002 · 6 tok

question

What does this JavaScript program log?

```js
const arr = [4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15];
const out = arr
  .map(n => n * 2)
  .filter(n => n % 2 === 0)
  .reduce((a, b) => a + b, 0);
console.log(out);
```

End your reply with exactly two plain-text lines (no markdown, no extra text after them):
ANSWER: <your final answer only>
CONFIDENCE: <integer 0-100, how confident you are that your answer is correct>

model answer: (none extracted)

correctcode.trace.python-v1anchorconf 99% · 3.2s · $0.015 · 277 tok

model answer: 0

correctcode.trace.nested-v1anchorconf 97% · 4.2s · $0.052 · 999 tok

model answer: 283

wrongcode.trace.js-v1anchorconf — · 4.2s · $0.002 · 3 tok

model answer: (none extracted)

wrongcode.trace.python-v1anchorconf — · 3.1s · $0.002 · 2 tok

model answer: (none extracted)

Run history

2026-08-05v0.2.0index_fit816
2026-08-05v0.1.0index_fit621