[stefan-jansen]

Closes #93

Outcome

Session APIs now resolve the canonical calendar through shared FeedSpec: explicit selection, declared feed metadata, then NYSE. Explicit None preserves observations unchanged with no session column or grid expansion. The constructor's old positional/calendar_name forms and explicit exchange selector remain supported, but conflicting explicit selectors fail. Descriptive metadata exchange is not inferred as a selector.

Data Metadata preserves version-2 omitted calendar versus explicit null through JSON/copy/shared projection, with version-1 null inheritance retained. Temporal normalization and serialization use Specs, not a second resolver. Declared timezone, timestamp semantics and grid fields survive metadata bridges.

Provider-driven updates retain explicit null in the metadata payload and reject invalid temporal declarations atomically instead of silently dropping them. The calendar-disable storage round trip is a positive control on the old implementation because the backend already preserves it; the two invalid-declaration mutations are the reproduced update defects. Provider reuse itself is a separate finding and is not hidden behind a broad ValueError assertion here: these update tests explicitly select the real synthetic provider.

Event intervals use [open,close), selecting the new session at continuous midnight. Close-labeled bars use (open,close], including exchange close and break start; explicit declarations override frequency/midnight heuristics. Lunch breaks and declared calendar interruptions are excluded using the same tradable intervals in assignment and completion. Daily labels remain unique when a session contains multiple tradable intervals. Session labels retain civil dates. Naive instants use existing UTC unless a timezone is declared; ambiguous local clocks fail. Existing outside-session null/raise/drop behavior remains.

DataManager's session operations now use one implementation with and without storage. fill_gaps=False assigns without expansion. Minute completion remains the existing open-labeled operation, rejects unsupported close/session-label metadata and honors calendar=None. This is not a claim of general intraday completeness or roll-calendar conformance.

Executed verification

• Base55b86e250fd6279222876c5a1e4c20ae1469d7fa, imported from an isolated immutable archive: ten real workflow failures and one passing control among existing public API calls. These reproduce default/None errors, lost midnight session, ignored no-fill flag and silently conflicting selectors, not new-keyword TypeErrors.
• Regression-only42aa185: original24 cases produce20 failures/4 controls passing.
• Current head14cb9957f07763eef490ea09acd42cba010aa185 includes merged provider repairc7b9dfa without rewriting published work. Invalid-temporal update cases fail twice on immutable55b86e2 with one disabled-calendar control passing. Empty timezone silently becoming UTC in both adapters is reproduced and rejected. Additional actual provider/model tests reproduce ignored event-count/non-minute completion, dropped session-start metadata and ignored general-grid policy; the current revision preserves declarations and explicitly rejects unsupported adapters. Full hosted gates must qualify the new exact combined head; previous-head green checks do not substitute for them.
• Ruff lint/format, ty, diff check and commit hooks passed. Full supported CI/resource/package/ecosystem and strict documentation gates must finish before ordinary merge. They run hosted; no heavy local suite or benchmark during Backtest's reserved timing window.
• Native interruption regression99df664 on sourcef57c8d9: six actual public-workflow failures and one daily-label control pass. Registered schedule with two halts, real SyntheticProvider minute rows: assignment incorrectly accepts halt rows and completion fabricates30 rows or accepts an observation during the halt. Fixed at14cb9957f07763eef490ea09acd42cba010aa185;148 focused session/range/provider tests pass in11.66s, native caps1 and ResourceWarning as error. Strict documentation build1.65s, full Ruff/format/ty and normal commit hooks pass. Full hosted qualification is pending at the new exact head.

Review and assistance

AI-assisted implementation, regressions and prose under maintainer direction. Owner reviewed actual source diff, shared contract/version semantics, old signatures, non-mutating disabled behavior, continuous/close/break interval boundaries, facade parity and metadata serialization. No independent reviewer is claimed. Separate range-planner PR92 changes different implementation files; remaining general intraday-grid, ingestion propagation and futures-roll work stays explicit. No release/deployment or change to published0.2.1; Specs source pin remains701bde68744035050ede386efce498234c661c21.

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