FA-11251 / Media timeline seeking / Open access
Chapter selection latest start · case 01
The first matching chapter remains selected throughout later chapters.
ROOT CAUSE
The first matching chapter remains selected throughout later chapters.
VERIFIED REPAIR
Preserve the media contract: Chapters are sorted unique start times. Select the latest chapter starting at or before playback time; no earlier chapter yields None.
Unsuccessful approach: Strict comparison keeps the preceding chapter at an exact chapter boundary.
Case contract
Chapters are sorted unique start times. Select the latest chapter starting at or before playback time; no earlier chapter yields None.
Why this case matters
A deterministic local media controller stage; metadata and downloaded data are supplied explicitly. No external player, service or codec is required.
1 / The failure
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(chapters, time):
return next((name for start,name in chapters if start<=time),None)
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1',solve(*([[0, 'a'], [10, 'b'], [20, 'c']], 15)),'b')
check('fixture 2',solve(*([[0, 'a'], [10, 'b']], 10)),'b')
check('fixture 3',solve(*([[5, 'a']], 2)),None)
check('fixture 4',solve(*([], 0)),None)
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 |
|---|---|---|---|
| fixture 1 | a | b | Failed |
| fixture 2 | a | b | Failed |
| fixture 3 | None | None | Passed |
| fixture 4 | None | None | Passed |
SHA-256 / 7a8e700257720c4e04345751a2788fd5095c692db8f8079af42343fc31ee41bd
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(chapters, time):
return next((name for start,name in reversed(chapters) if start<time),None)
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1',solve(*([[0, 'a'], [10, 'b'], [20, 'c']], 15)),'b')
check('fixture 2',solve(*([[0, 'a'], [10, 'b']], 10)),'b')
check('fixture 3',solve(*([[5, 'a']], 2)),None)
check('fixture 4',solve(*([], 0)),None)
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 |
|---|---|---|---|
| fixture 1 | b | b | Passed |
| fixture 2 | a | b | Failed |
| fixture 3 | None | None | Passed |
| fixture 4 | None | None | Passed |
SHA-256 / 7e7611733229edc095e68a0324b7828579fbadd1bf362bd1b7346bedeb99b568
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(chapters, time):
return next((name for start,name in reversed(chapters) if start<=time),None)
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1',solve(*([[0, 'a'], [10, 'b'], [20, 'c']], 15)),'b')
check('fixture 2',solve(*([[0, 'a'], [10, 'b']], 10)),'b')
check('fixture 3',solve(*([[5, 'a']], 2)),None)
check('fixture 4',solve(*([], 0)),None)
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 |
|---|---|---|---|
| fixture 1 | b | b | Passed |
| fixture 2 | b | b | Passed |
| fixture 3 | None | None | Passed |
| fixture 4 | None | None | Passed |
SHA-256 / 540d6713052a0c851c7ae893e8e7baaee3077a206d65dbb9195ae5d4bf4530cc
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 2026-09-29T14:38:46.219978+00:00.
Case digest / fec8bccf7ec55518dea897278f81ccd1e7e1a04b9dd857d02a8226072a2a1429