ADR-0011: Batch planning split into its own module

• Status: Accepted
• Date: 2026-08-13

Context

ADR-0006 rejected splitting sources.py further by individual command, because every command in it (scan_sources, apply_source_scan, lint_sources, source_coverage, compute_source_delta, suggest_dedupe, write_source_snapshot) shares the source manifest and the canonical-source predicate — splitting by command would recreate that duplication one level up.

plan_batches (added later, issue #84, after ADR-0006) doesn’t share that dependency. It never reads the manifest, never parses frontmatter, never calls _iter_markdown or _is_canonical_source — it walks raw files under a source_dir by byte/count caps, before any file has become a source in the domain sense. “Batch” wasn’t in CONTEXT.md’s glossary despite being used in the CLI (batch-plan) and write-gate workflow (“batch coordinator session”).

Decision

• Batch/BatchStats/BatchPlan/plan_batches move to a new batches.py, with their tests to test_batches.py.
• CONTEXT.md gains a Batch glossary entry, distinguishing it from source and Snapshot source.
• sources.py is otherwise unchanged — ADR-0006’s reasoning still holds for the manifest-sharing commands it covers.

Consequences

• This narrows, not reverses, ADR-0006: the split criterion is “does this command participate in the shared manifest/canonical-source state,” not “is this a different command.”
• Any future addition to sources.py should be checked against that same criterion before being added there by default.