feat(graph): rank the frontier — what to consolidate next (v6.5.0)

[CryptoJones]

Closes #197.

The gap

omind graph answers neighbors, path, orphans, dangling, stats. Every one is a structural yes/no: is this note connected, is that link broken, how big is the graph. None answers the ranking question — of everything in the vault, what should be worked on next?

score = (out_degree - in_degree) * 0.5 ** (days_since_updated / 30)

High score: points at many, pointed at by few, touched recently. That is a note where memory is actively accumulating and consolidation hasn't caught up. Negative: a hub the vault has already absorbed.

The distinction that makes this worth having: an orphan is disconnected; a frontier note is connected but unabsorbed. Only the second one tells you where to spend effort.

Surfaces

• omind graph frontier [--limit N] [--include-generated] [--json] — table or JSON.
• graph(op="frontier") on the MCP tool, paged like every other list-shaped result (invariant 7). Ranking is computed over the whole graph, then paged.

Design notes

• Read-only, no write path. Deliberate, following the source design's reasoning that keeping it read-only removes a write-path attack surface.
• No new scan, no new state. The links table was already built. The one addition is surfacing mtime_ns from the index's notes table — already stored, previously not read.
• Generated notes excluded by default. Journals and worklogs link outward at everything by construction; unfiltered they own the entire ranking. Same rule as searchindex._weight_generated, --include-generated to override.
• A true half-life, not a time constant. The source uses exp(-days / HALFLIFE), which decays to 1/e — not a half — at the named value. This uses 0.5 ** (days / 30), so "30-day half-life" means what it says.

Verified against the live vault

score	out	in	days	note
+4.33	5	0	6	omind 3.2.0 — knowledge graph over the vault's [[wikilinks]] (2026-06-25).md
+3.49	5	0	16	Antigua Runners — agent handoff after Quiet Circle basement (2026-07-17).md
+3.00	3	0	0	omind #186–#190 backlog batch — CJ chose minor-per-item …

Recent, outward-linking, unabsorbed — which is what it claims to find.

Tests

Four: hub-vs-frontier ordering; recency decay (a note aged exactly one half-life scores half as much, pytest.approx); generated exclusion and the opt-in; limit=0 returns everything in descending order. Plus MCP coverage and the paging contract.

Gates

ruff check . · mypy src (strict) · pytest (856 passed, 1 skipped) · pip-audit — green locally.

🤖 Generated with Claude Code

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📒 Files selected for processing (11)

• BACKLOG.md
• CHANGELOG.md
• README.md
• pyproject.toml
• src/omind/__init__.py
• src/omind/cli.py
• src/omind/graph.py
• src/omind/searchindex.py
• src/omind/server.py
• tests/test_graph.py
• tests/test_server.py

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