Use IB UTC syntax for history `endDateTime`

Serialize aware reverse-fill boundaries as `YYYYMMDD-HH:MM:SS`
before handing them to `ib_async`.

This avoids Gateway error 10314 from its trailing-`UTC` format and
drops the unfinished EST comparison breakpoint from `Client.bars()`.

Prompt-IO: ai/prompt-io/opencode/20260729T034106Z_922a5df8_prompt_io.md

(this patch was generated in some part by `opencode` using `gpt-5.6-sol` (`openai`))

.claude/skills/run-tests/test-harness-reference.md

@@ -106,6 +106,7 @@ Deterministic or local first-pass targets:
 - `tests/test_watchlists.py`
 - `tests/test_storage_audit.py`
 - `tests/test_backfill_audit_snippet.py`
+- `tests/test_ib_history.py`
 - `tests/test_accounting.py::test_account_file_default_empty`
 - `tests/test_services.py::test_runtime_boot`
 - `tests/test_services.py::test_datad_spawn`
@@ -188,6 +189,7 @@ tests/
   test_dpi_font.py          Qt DPI/font behavior
   test_ems.py               actor, EMS, and paper-position behavior
   test_feeds.py             live Binance/Kraken feeds and shared memory
+  test_ib_history.py        deterministic IB history request formatting
   test_questrade.py         obsolete credentialed tests; skipped
   test_services.py          pikerd/datad/feed/EMS actor lifecycle
   test_storage_audit.py     read-only NativeDB audit and JSON CLI
@@ -203,6 +205,7 @@ tests/
 | `piker/watchlists/` | `tests/test_watchlists.py` | CLI suite is skipped |
 | `piker/storage/_audit.py`, `piker/storage/cli.py` | `tests/test_storage_audit.py` | direct Typer app, no actor |
 | `snippets/nativedb_backfill_audit.xsh` | `tests/test_backfill_audit_snippet.py` | disposable paths only |
+| `piker/brokers/ib/api.py` history formatting | `tests/test_ib_history.py` | fake client, no network |
 | `piker/config.py` | `test_account_file_default_empty` | root-network test has a known mismatch |
 | `piker/accounting/` | targeted accounting node | some cases use live/configured state |
 | `piker/ui/_style.py`, `piker/ui/qt.py` | `tests/test_dpi_font.py` | GUI/config-isolated opt-in |

ai/prompt-io/opencode/20260729T034106Z_922a5df8_prompt_io.md

@@ -0,0 +1,40 @@
+---
+model: gpt-5.6-sol
+provider: openai
+service: opencode
+session: 24fb9765-a550-4570-8350-f0fc9b7e17db
+timestamp: 2026-07-29T03:41:06Z
+git_ref: 922a5df8
+scope: code
+substantive: true
+raw_file: 20260729T034106Z_922a5df8_prompt_io.raw.md
+---
+
+## Prompt
+
+Diagnose the live IB reverse-fill failure where
+`reqHistoricalDataAsync()` raised API error 10314 because its end date,
+time, or timezone was invalid.
+
+## Response summary
+
+Traced the failure to `Client.bars()`, where an unfinished EST conversion
+left the original datetime for `ib_async` to serialize as
+`YYYYMMDD HH:MM:SS UTC`. Converted aware boundaries explicitly to UTC and
+passed IB's accepted `YYYYMMDD-HH:MM:SS` string while retaining a blank
+latest-request boundary. Added exact request-argument regressions.
+
+## Files changed
+
+- `piker/brokers/ib/api.py` - explicit UTC-dash history boundary format
+- `tests/test_ib_history.py` - IB request-format regressions
+- `.claude/skills/run-tests/test-harness-reference.md`
+  - deterministic IB history test mapping
+- `ai/prompt-io/opencode/20260729T034106Z_922a5df8_prompt_io.raw.md`
+  - unedited response record
+- `ai/prompt-io/opencode/20260729T034106Z_922a5df8_prompt_io.md`
+  - provenance metadata and response summary
+
+## Human edits
+
+None - generated changes have not been edited by the human.

ai/prompt-io/opencode/20260729T034106Z_922a5df8_prompt_io.raw.md

@@ -0,0 +1,25 @@
+---
+model: gpt-5.6-sol
+provider: openai
+service: opencode
+timestamp: 2026-07-29T03:41:06Z
+git_ref: 922a5df8
+diff_cmd: git diff HEAD~1..HEAD
+---
+
+> `git diff HEAD~1..HEAD -- piker/brokers/ib/api.py tests/test_ib_history.py .claude/skills/run-tests/test-harness-reference.md`
+
+Fixed IB reverse-history requests to serialize aware end boundaries with
+IB's explicit UTC-dash syntax, `YYYYMMDD-HH:MM:SS`. This bypasses
+`ib_async`'s trailing-`UTC` representation, which the live Gateway rejected
+with API error 10314, and removes the unfinished EST comparison breakpoint.
+
+The regression captures the exact `reqHistoricalDataAsync()` argument for
+latest, stdlib-aware, Pendulum UTC, and America/New_York inputs.
+
+Verification generated with the patch:
+
+- IB history request regressions: 4 passed
+- focused Ruff: passed
+- `git diff --check`: passed
+- adversarial review: no findings

piker/brokers/ib/api.py

@@ -29,7 +29,10 @@ from dataclasses import (
     asdict,
     astuple,
 )
-from datetime import datetime
+from datetime import (
+    UTC,
+    datetime,
+)
 from functools import (
     partial,
 )
@@ -395,15 +398,13 @@ class Client:
             default_dt_duration
         )
 
-        # TODO: maybe remove all this?
         global _enters
         if end_dt is None:
-            end_dt: str = ''
+            end_date_time: str = ''
-
         else:
-            est_end_dt = end_dt.in_tz('EST')
+            end_date_time = end_dt.astimezone(UTC).strftime(
-            if est_end_dt != end_dt:
+                '%Y%m%d-%H:%M:%S'
-                breakpoint()
+            )
 
         _enters += 1
 
@@ -412,7 +413,7 @@ class Client:
 
         kwargs: dict[str, Any] = dict(
             contract=contract,
-            endDateTime=end_dt,
+            endDateTime=end_date_time,
             formatDate=2,
 
             # OHLC sampling values:

tests/test_ib_history.py

@@ -0,0 +1,81 @@
+'''
+IB historical-data request regressions.
+
+'''
+from datetime import (
+    UTC,
+    datetime,
+)
+from types import SimpleNamespace
+
+from pendulum import datetime as pdatetime
+import pytest
+import trio
+
+from piker.brokers.ib.api import Client
+
+
+@pytest.mark.parametrize(
+    ('end_dt', 'expected'),
+    [
+        (None, ''),
+        (
+            datetime(2026, 7, 28, 23, 30, tzinfo=UTC),
+            '20260728-23:30:00',
+        ),
+        (
+            pdatetime(2026, 7, 28, 23, 30, tz='UTC'),
+            '20260728-23:30:00',
+        ),
+        (
+            pdatetime(
+                2026,
+                7,
+                28,
+                23,
+                30,
+                tz='America/New_York',
+            ),
+            '20260729-03:30:00',
+        ),
+    ],
+)
+def test_history_end_datetime_uses_ib_utc_format(
+    end_dt: datetime|None,
+    expected: str,
+) -> None:
+    '''
+    Reverse history boundaries must use IB's explicit UTC syntax.
+
+    ``ib_async`` adds a trailing ``UTC`` zone to aware datetimes.
+    The live IB gateway rejected that form with error 10314 while
+    filling an MNQ gap. Invoke ``Client.bars()`` with stdlib and
+    Pendulum boundaries, then capture the request kwargs.
+    Prove each becomes IB's UTC-dash form while latest requests stay
+    blank.
+
+    '''
+    request: dict = {}
+
+    class FakeIB:
+        async def reqHistoricalDataAsync(self, **kwargs) -> list:
+            request.update(kwargs)
+            return []
+
+    client = SimpleNamespace(ib=FakeIB())
+
+    async def find_contracts(fqme: str) -> list:
+        return [SimpleNamespace()]
+
+    client.find_contracts = find_contracts
+
+    async def main() -> None:
+        await Client.bars(
+            client,
+            fqme='mnq.cme.20260918',
+            sample_period_s=60,
+            end_dt=end_dt,
+        )
+
+    trio.run(main)
+    assert request['endDateTime'] == expected