Hmbown/CodeWhale · error · PersistenceBacklogError

rss_during_delta_bytes is inconsistent

Error message

rss_during_delta_bytes is inconsistent

What it means

Raised by validate_receipt() in scripts/check-persistence-backlog-budget.py when a receipt with rss_supported=true records rss_during_delta_bytes that is not exactly max(0, rss_during_bytes - rss_before_bytes). The raw RSS samples are treated as ground truth and the delta column must be a deterministic, clamped-at-zero recompute of them, so any mismatch means the receipt was hand-edited or produced by a buggy sampler. This integrity check runs before the receipt is compared against the budget ceilings.

Source

Thrown at scripts/check-persistence-backlog-budget.py:233

        isinstance(item, str) and item for item in limitations
    ):
        raise PersistenceBacklogError("limitations must be a non-empty string array")

    if not isinstance(receipt["rss_supported"], bool):
        raise PersistenceBacklogError("rss_supported must be boolean")
    if receipt["rss_supported"] != (platform == "macos"):
        raise PersistenceBacklogError(
            "rss_supported must be true exactly on the macOS measurement lane"
        )
    rss_fields = RSS_SAMPLE_FIELDS + RSS_DELTA_FIELDS
    if receipt["rss_supported"]:
        for field in rss_fields:
            non_negative_integer(receipt[field], field)
        before = receipt["rss_before_bytes"]
        if receipt["rss_during_delta_bytes"] != max(
            0, receipt["rss_during_bytes"] - before
        ):
            raise PersistenceBacklogError("rss_during_delta_bytes is inconsistent")
        if receipt["rss_after_delta_bytes"] != max(
            0, receipt["rss_after_bytes"] - before
        ):
            raise PersistenceBacklogError("rss_after_delta_bytes is inconsistent")
    elif any(receipt[field] is not None for field in rss_fields):
        raise PersistenceBacklogError("unsupported RSS fields must be null")


def validate_budget(budget: dict[str, Any]) -> None:
    if budget.get("document_kind") != BUDGET_KIND:
        raise PersistenceBacklogError(f"budget document_kind must be {BUDGET_KIND}")
    if budget.get("schema_version") != SCHEMA_VERSION:
        raise PersistenceBacklogError("budget schema_version changed")
    fixture = budget.get("fixture")
    if not isinstance(fixture, dict) or set(fixture) != set(FIXTURE):
        raise PersistenceBacklogError("budget fixture no longer matches the frozen workload")
    for field, expected in FIXTURE.items():
        if type(fixture[field]) is not type(expected) or fixture[field] != expected:

View on GitHub (pinned to 8880682c63)

Solutions

1. Recompute and write rss_during_delta_bytes = max(0, rss_during_bytes - rss_before_bytes) in the receipt
2. Prefer regenerating the receipt entirely: python scripts/measure-persistence-backlog.py > receipt.json
3. If the sampler itself emits inconsistent deltas, fix its delta computation to use the identical clamp formula
4. Re-run scripts/check-persistence-backlog-budget.py --receipt receipt.json to confirm

Example fix

// before (receipt.json)
"rss_before_bytes": 18923520,
"rss_during_bytes": 28377088,
"rss_during_delta_bytes": 9453000

// after: 28377088 - 18923520 = 9453568
"rss_before_bytes": 18923520,
"rss_during_bytes": 28377088,
"rss_during_delta_bytes": 9453568

def rss_during_delta_consistent(receipt: dict) -> bool:
    if not receipt.get("rss_supported"):
        return receipt.get("rss_during_delta_bytes") is None
    return receipt["rss_during_delta_bytes"] == max(
        0, receipt["rss_during_bytes"] - receipt["rss_before_bytes"]
    )
# call before compare(receipt, budget)

from typing import TypeGuard

def has_consistent_rss_deltas(r: dict) -> TypeGuard[dict]:
    before = r["rss_before_bytes"]
    return (r["rss_during_delta_bytes"] == max(0, r["rss_during_bytes"] - before)
            and r["rss_after_delta_bytes"] == max(0, r["rss_after_bytes"] - before))

try:
    increases, decreases = compare(receipt, budget)
except PersistenceBacklogError as error:
    print(f"[persistence-backlog-budget] ERROR: {error}", file=sys.stderr)
    raise SystemExit(2) from error

When it happens

Trigger: Calling compare()/validate_receipt() with rss_supported true and rss_during_delta_bytes differing from max(0, rss_during_bytes - rss_before_bytes) - e.g. an off-by-one edit, a delta computed from a stale rss_during_bytes sample, or an unclamped negative difference stored as anything other than 0. The repo's own tests trigger it by bumping rss_during_delta_bytes by 1 (test_rss_delta_must_match_samples).

Common situations: Hand-editing a receipt JSON to nudge a number; refactoring scripts/measure-persistence-backlog.py so it samples RSS in a different order or drops the max(0, ...) clamp; mixing in receipts from an older schema where deltas were computed differently; KB-vs-bytes unit confusion.

Related errors

• rss_after_delta_bytes is inconsistent
• unsupported RSS fields must be null
• baseline_observation must retain the final request and paylo
• budget document_kind must be {BUDGET_KIND}
• budget schema_version changed

AI-assisted analysis of Hmbown/CodeWhale@8880682c63 (2026-08-16). Data as JSON: /api/errors/9fb568fa2d2df175. Report an issue: GitHub.