---
model: gpt-6 (exact variant not exposed)
service: codex
timestamp: 2026-09-24T16:57:57.342784+00:00
git_ref: 1da9b760
diff_cmd: git diff 1da9b760 -- piker/tsp/_history.py tests/test_history_backfill.py
---

## Prompt

The human requested documentation and tests for
maybe_fill_null_segments(), identifying its flat OHLC fallback
and asking how packed SHM could accept later recovered bars.

## Code output

> `git diff 1da9b760 -- piker/tsp/_history.py`

> `git diff 1da9b760 -- tests/test_history_backfill.py`

Document the existing slot-based repair and its limitations.
Extend fallback coverage to NoData and DataUnavailable; verify
the observed packed MNQ gap remains unchanged. Reproduce the
relative-tolerance failure at a modern epoch, then disable relative
tolerance in the synthetic timestamp boundary check.

## Validation

Before the fix: modern-epoch boundary case failed, zero-epoch
case passed. The overfull synthetic run duplicated the right bar.
After the fix: 15 backfill tests passed in 1.99s.

## Close-copy factoring follow-up

The human requested stronger internal types, a reusable close-copy
helper, searchable comments for copying close and synthesizing
stamps, and research into historical venue closure queries.
Extracted _copy_close_to_null_rows(), preserving non-OHLC fields and
rejecting occupied slots before mutation. Added explicit callback,
array, segment-index and date annotations. Preserved the existing
provenance TODO and suggested avoiding volume sentinels.
Four helper cases cover successful fill and unchanged rejected
inputs. Backfill suite: 19 passed in 2.01s; Ruff and diff check pass.

IB documents historical SCHEDULE requests separately from contract
hours. The installed ib_async exposes reqHistoricalScheduleAsync.
No live schedule request or venue behavior change was performed.
Source: https://interactivebrokers.github.io/tws-api/historical_bars.html