Adopts the zig-cobs v1.2.0 coverage-driver pattern. See CHANGELOG for the measured line-coverage number and methodology.

The seven algorithms the original v0.1.0 README listed as out-of-scope are now all implemented.

Note on version chronology: v1.0.0 (also dated 2026-05-13) shipped earlier the same day as a hygiene-only milestone (CI / SECURITY / contributor docs / API freeze statement). This release is the first to ship the genuine algorithmic v1.0 content. Bumped to v1.1.0 to preserve the already-published v1.0.0 tag rather than rewrite history.

Added

• betweennessCentrality — Brandes 2001 algorithm. BFS path for unweighted = true (O(V·E)); Dijkstra path otherwise. Optional [0, 1] normalisation.
• closenessCentrality — Wasserman-Faust normalised closeness. Handles disconnected components.
• fiedlerValue / fiedlerVector / fiedler — algebraic connectivity (second-smallest Laplacian eigenvalue) via deflated power iteration on M = τI − L with τ = 2·max_deg + 1. O(V + E) per iteration. Validated against closed-form λ₁ for Pₙ, Cₙ, K₁,ₙ₋₁, Kₙ, and a barbell reference.
• louvain / modularity — Blondel et al. 2008 modularity-maximising community detection. Returns labels, community count, and Newman modularity Q.
• directedPagerank — directed-edge PageRank respecting edge direction; sinks redistribute mass uniformly.
• bfs / dfs / sssp / bfsPath — foundational traversal helpers.
• buildAdjacency / buildDirectedAdjacency — CSR-style adjacency construction exposed as public API.

Changed

• Test count: 16 → 50. Includes three new random-graph fuzz harnesses (betweenness non-negativity + upper bound; Fiedler spectral bound; Louvain modularity ∈ [-0.5, 1]).
• Source factored into src/{traversal, centrality, spectral, community}.zig with src/root.zig as the re-export hub. Existing API preserved verbatim — purely additive.
• Minimum Zig: 0.15.0 → 0.16.0.

Bench numbers (i7-1065G7 @ 1.30 GHz, busy laptop, ±2× variance)

Louvain modularity on 1k-node ER sparse graph: Q ≈ 0.33 across 16 communities. Fiedler λ₁ ≈ 0 on 10k-node disconnected ER graph (correct — k components → k zero eigenvalues).

Out of scope for this release

Honest list of what is not implemented: Leiden refinement, parallel-edge merging at construction time, hypergraphs, ILP-optimal community detection, CSR caching at the Graph level, GPU offload. Each is documented in the README with reasoning.

PRs welcome — the bar is "correctness against canonical small examples + invariant fuzz + benchmark on a medium graph".

v1.0.0 — 2026-05-13

Production-grade hygiene milestone.

• LICENSE, README, CONTRIBUTING, SECURITY, CI all present.
• Repo declared at v1.x milestone: existing surface stable; breaking changes bump to v2.x.
• Engineering posture: Virgil work-in-progress convention adapted for OSS — v1.0 means we stand behind the existing surface; v1.x patches refine without breaking.

See CHANGELOG.md for full context.

Initial release. See CHANGELOG.md for details. Cross-validated tests, CI, runnable example, MIT license. Minimum Zig: 0.16.0.