Impact & Analysis

NestWeaver’s analysis commands help you understand the consequences of changes before you make them. The impact command traces the blast radius of a symbol through the dependency graph with confidence-weighted scoring, while pr-impact analyzes an entire PR’s changed files and assigns a risk level. These are structural analyses based on the graph — no LLM required.

checkout and refund call processPayment, so they sit in its blast radius. The walk follows incoming calls, imports, and inheritance.

Command reference

Command	Description	Key Flags
impact	Trace blast radius of a symbol	--depth, --confidence, --repo, --json
pr-impact	PR blast radius with risk scoring	--files, --depth, --json
affected-tests	Select tests for changed files	--files, --base-ref, --json
dead-code	Detect unreachable symbols	--min-confidence, --json
hubs	Find most-connected hub nodes	--top, --json, --config
bridges	Find architectural chokepoints	--top, --json, --config
contracts	Inspect API contract graph	(subcommand)
ranking	Inspect ranking priors	explain, rank subcommands
eval	Offline retrieval-quality evaluation	run, compare subcommands
export	Export graph to external format	--format, --output, --top
clusters	Detect community clusters	--resolution, --json

Blast radius analysis

# Check what depends on a symbol
nestweaver impact "processPayment" --depth 5

# Filter to a specific repo in a multi-repo setup
nestweaver impact "processPayment" --repo payments-api --json

# Set minimum edge confidence threshold
nestweaver impact "processPayment" --confidence 0.8

impact traverses incoming CALLS, IMPORTS, EXTENDS, and IMPLEMENTS edges from the target symbol. Each affected symbol gets an impact_score that decays multiplicatively through edges — low-confidence paths are pruned automatically. The default depth is 3.

PR impact analysis

# Auto-detect changed files from git diff
nestweaver pr-impact

# Specify files explicitly
nestweaver pr-impact --files src/auth.rs,src/db.rs

# Deeper analysis
nestweaver pr-impact --depth 5 --json

pr-impact maps changed files to their symbols, runs transitive impact analysis, groups results by cluster, and assigns Low, Medium, High, or Unknown. Unknown means the change was not assessed. When no --files are given, it uses git diff --name-only against the working tree.

Test selection

# Select tests affected by specific file changes
nestweaver affected-tests --files src/auth.rs,src/db.rs

# Diff against a base branch
nestweaver affected-tests --base-ref main --json

affected-tests performs static, call-graph-based regression test selection. It maps changed files to symbols, reverse-traverses CALLS/IMPORTS to depth 3, and buckets dependent test files into priority tiers. This is a prioritized signal, not a provably safe subset — it misses reflection, DI, codegen, and data-driven tests.

Dead code detection

# Find potentially dead code
nestweaver dead-code

# Only high-confidence results
nestweaver dead-code --min-confidence high --json

dead-code walks forward from every entry point following CALLS, IMPORTS, EXTENDS, IMPLEMENTS, and MEMBER_OF edges. Symbols not reached are reported as potentially dead, with confidence levels: low, medium, high. Entry points are determined from manifest files and visibility modifiers.

Graph topology

# Find hub nodes (ranked by total degree: incoming plus outgoing)
nestweaver hubs --top 20

# Find bridge/chokepoint nodes (highest betweenness centrality)
nestweaver bridges --top 20

# Detect community clusters (Louvain-style local moving)
nestweaver clusters --resolution 0.5 --json

Hubs are central abstractions many parts of the codebase depend on. Bridges are architectural chokepoints — many shortest paths pass through them, so changing a bridge has outsized blast radius. Clusters use Louvain-style local moving, not the full Leiden algorithm. Results are cached in a sidecar file. Hubs are ranked by total degree. PageRank is extra metadata, not the sort key.

Graph export

# Export as Cypher (Neo4j)
nestweaver export --format cypher

# Export as GraphML (Gephi/yEd)
nestweaver export --format graphml --output graph.xml

# Export as Mermaid flowchart (top 30 symbols by PageRank)
nestweaver export --format mermaid --top 30

# Export as MessagePack (for WASM mode)
nestweaver export --format msgpack --output graph.msgpack

Supported formats: Cypher (Neo4j), GraphML (Gephi/yEd), Mermaid, MessagePack.