taskgraph_ts/tasks/implementation/analysis/bottlenecks.md

id, name, status, depends_on, scope, risk, impact, level

id	name	status	depends_on	scope	risk	impact	level
analysis/bottlenecks	Implement bottlenecks analysis function	completed	graph/construction graph/queries	narrow	low	component	implementation

Description

Implement bottlenecks(graph: TaskGraph): Array<{ taskId: string; score: number }> using graphology-metrics betweenness centrality. Bottleneck tasks are those on the most shortest paths between other nodes.

Acceptance Criteria

• bottlenecks returns array of { taskId, score } objects sorted by score descending
• Uses graphology-metrics betweenness centrality computation
• Normalized scores (0.0–1.0 range)
• Tasks with score 0 are still included (they're not bottlenecks)
• Works on disconnected graphs (betweenness is 0 for disconnected components)
• Unit tests: linear chain (middle node has highest betweenness), star graph (center has highest), independent nodes (all zero)

References

• docs/architecture/api-surface.md — bottlenecks signature
• docs/architecture/build-distribution.md — graphology-metrics dependency

Notes

Graphology-metrics betweenness centrality throws on empty graphs (mnemonist FixedStack requires positive capacity). Handled by returning empty array when graph.raw.order === 0.

Summary

Implemented bottlenecks(graph: TaskGraph): BottleneckResult[] using graphology-metrics betweenness centrality with normalized: true.

• Created: src/analysis/bottleneck.ts (bottlenecks function + BottleneckResult interface)
• Modified: test/analysis.test.ts (replaced placeholder with 20 tests covering all acceptance criteria)
• Tests: 20, all passing (linear chain, star graph, independent nodes, disconnected graph, diamond, empty graph, single node, sorted output, normalized scores)