FA-11276 / Media timeline seeking / Open access
Seek request generation result · case 01
Completion of an earlier seek overwrites the newer requested position.
ROOT CAUSE
Completion of an earlier seek overwrites the newer requested position.
VERIFIED REPAIR
Preserve the media contract: Install an asynchronous seek result [generation,position] only if it belongs to the exact current seek request; retain current position otherwise.
Unsuccessful approach: Accepting all older generations preserves the race instead of fencing obsolete completions.
Case contract
Install an asynchronous seek result [generation,position] only if it belongs to the exact current seek request; retain current position otherwise.
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(position, generation, completion):
return completion[1]
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1',solve(*(10, 3, [2, 2])),10)
check('fixture 2',solve(*(10, 3, [3, 20])),20)
check('fixture 3',solve(*(10, 3, [4, 30])),10)
check('fixture 4',solve(*(0, 0, [0, 5])),5)
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 | 2 | 10 | Failed |
| fixture 2 | 20 | 20 | Passed |
| fixture 3 | 30 | 10 | Failed |
| fixture 4 | 5 | 5 | Passed |
SHA-256 / 993c4027e47eb3311147424e473c8764d27bfdcb8a367f32a81d9f89e3e2d3b6
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(position, generation, completion):
return completion[1] if completion[0]<=generation else position
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1',solve(*(10, 3, [2, 2])),10)
check('fixture 2',solve(*(10, 3, [3, 20])),20)
check('fixture 3',solve(*(10, 3, [4, 30])),10)
check('fixture 4',solve(*(0, 0, [0, 5])),5)
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 | 2 | 10 | Failed |
| fixture 2 | 20 | 20 | Passed |
| fixture 3 | 10 | 10 | Passed |
| fixture 4 | 5 | 5 | Passed |
SHA-256 / 89c738a2d9db535f6ff24d57120865a84503f81b2f86f6a60b1e8a9490fdf5d9
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(position, generation, completion):
return completion[1] if completion[0]==generation else position
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1',solve(*(10, 3, [2, 2])),10)
check('fixture 2',solve(*(10, 3, [3, 20])),20)
check('fixture 3',solve(*(10, 3, [4, 30])),10)
check('fixture 4',solve(*(0, 0, [0, 5])),5)
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 | 10 | 10 | Passed |
| fixture 2 | 20 | 20 | Passed |
| fixture 3 | 10 | 10 | Passed |
| fixture 4 | 5 | 5 | Passed |
SHA-256 / c781cf3a8818b4e9eb04c300f0bb61e57aa90f5860b1add7dd50488559b6c0e1
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 2026-09-29T14:38:46.551699+00:00.
Case digest / bf711842461f44c34a794f3c1af9436fcda1546b5517a968c3f21ab163aaa3e7