FA-100711 / Speculative decoding bookkeeping / Open access
Decoding: Unaccepted proposal count is inflated by a replacement slot · case 01
Unaccepted proposal count is inflated by a replacement slot.
ROOT CAUSE
The replacement token is incorrectly included among rejected draft tokens.
THE FAILURE
The replacement token is incorrectly included among rejected draft tokens.
Unsuccessful approach: Using the total output count as residual swaps accepted and rejected accounting.
Case contract
Return draft length minus accepted prefix length.
Why this case matters
A self-contained bookkeeping model makes prefix and token-count semantics observable without a model runtime.
1 / The failure
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(draft, accepted):
return len(draft)-accepted+1
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('partial residual', solve([1,2,3],1),2)
check('reject all', solve([1,2],0),2)
check('all accepted', solve([1,2],2),0)
check('empty', solve([],0),0)
check('singleton reject', solve([N],0),1)
check('single accepted', solve([N],1),0)
check('long suffix', solve([1,2,3,4,5],2),3)
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 |
|---|---|---|---|
| partial residual | 3 | 2 | Failed |
| reject all | 3 | 2 | Failed |
| all accepted | 1 | 0 | Failed |
| empty | 1 | 0 | Failed |
| singleton reject | 2 | 1 | Failed |
| single accepted | 1 | 0 | Failed |
| long suffix | 4 | 3 | Failed |
SHA-256 / d2fd1be9cacf061e76a84e67ffa9b51ca060ee2da6a4897a0409e59e66198b33
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(draft, accepted):
return accepted
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('partial residual', solve([1,2,3],1),2)
check('reject all', solve([1,2],0),2)
check('all accepted', solve([1,2],2),0)
check('empty', solve([],0),0)
check('singleton reject', solve([N],0),1)
check('single accepted', solve([N],1),0)
check('long suffix', solve([1,2,3,4,5],2),3)
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 |
|---|---|---|---|
| partial residual | 1 | 2 | Failed |
| reject all | 0 | 2 | Failed |
| all accepted | 2 | 0 | Failed |
| empty | 0 | 0 | Passed |
| singleton reject | 0 | 1 | Failed |
| single accepted | 1 | 0 | Failed |
| long suffix | 2 | 3 | Failed |
SHA-256 / d423ac48b81d9c21dd8c4fed88596e2585d9af0380ec52f371845a60c3fd21c9
HELD IN THE MEMBER ARCHIVE
The verified repair and its recorded checks are member-only.
This mechanism has 7 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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Sign in to the archive ↗Verification & scope
These are finite toy sequences with explicit contracts; they make no claim about production decoder behavior or model quality. 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 2026-09-30T16:48:38.598381+00:00.
Case digest / 2861db9c0accb29c6d6b7a68f8d2ebcc012fbf2ae4b3fc1970e6d162f27beb39