Bug: fathom.packs entry points reference a nonexistent nautilus.rule_packs package (ModuleNotFoundError)

[se-jo-ma]

Bug (standalone; weak paper tie). pyproject.toml declares fathom.packs entry points pointing at nautilus.rule_packs.data_routing_nist / data_routing_hipaa, but that Python package does not exist on disk — the actual packs live as YAML under rule-packs/data-routing-{nist,hipaa}/. fathom ships a real RulePackLoader.discover that calls ep.load(), so any caller resolving these packs by name hits ModuleNotFoundError.

Fix (either).

• (a) Create nautilus/rule_packs/{data_routing_nist,data_routing_hipaa}/ packages whose __path__ resolves to the YAML pack dirs; or
• (b) repoint the entry points at the real pack location.
• Add a test that imports every declared fathom.packs entry point and asserts a non-empty rule set loads.

Where.

• pyproject.toml:90-92 ([project.entry-points.'fathom.packs'] → nautilus.rule_packs.*, verified absent).
• Actual YAML: rule-packs/data-routing-nist/, rule-packs/data-routing-hipaa/.
• Consumer: fathom RulePackLoader.discover (packs.py:18-42).

Acceptance criteria.

• Every declared fathom.packs entry point resolves and loads a non-empty rule set (covered by a test).

Blast radius. Low — nautilus's own runtime loads only the nautilus.adapters group (loader.py:158, broker.py:170), never fathom.packs; this only affects external callers resolving the NIST/HIPAA packs by entry-point name. Built-ins (nautilus/rules/) and external packs (rule-packs/) use slightly different layouts and may need normalization.

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Source: arXiv:2605.22502v1 — "Compiling Agentic Workflows into LLM Weights" (subterranean agents). Distilled from arXiv-research/2605.22502v1/analysis.md; file refs verified against current main by the analysis pass.