cstat-driven codebase cleanup — agent reference

What is cstat

cstat is a static analysis CLI for Rust codebases. It measures structure; it does not modify code. Use it before and after a cleanup stage to verify that objective metrics moved in the intended direction while the project's own build and tests preserve behavior.

Starting point

Run the focused report first:

cstat report --json --path <project_root>

Omitting the command is equivalent to cstat summary, which is the same focused report. The JSON contains:

line_counts: total code lines, physical lines, and per-file counts.
symbols: total and per-file counts for functions, structs, enums, traits, and impl blocks.
dependencies: module list, module interdependency matrix, edge count, and fan-in/fan-out degrees.
dead_code: functions not statically reachable from main, tests, or benchmarks.
test_reachability: static test/benchmark reachability, step counts, max depth, and per-function/per-edge reaching-entry counts.

The focused report intentionally excludes older exploratory dashboards. They remain available under cstat advanced ....

Focused drilldowns

Each accepts --json for structured output.

cstat loc --explain --json — machine-readable loc contract: modes, code_lines rules, project JSON fields, and selected-file JSON fields.
cstat loc --json --path . — project size-shape data.
cstat loc --json --path src/lib.rs — selected-file projected static line reachability.
cstat symbols --json --path . — symbol totals by kind and per file.
cstat deps --json --path . — dependency edges, coupling, fan-in/fan-out, and cohesion.
cstat dead-code --json --path . — static cold-function candidates.
cstat test-reachability --json --path . — static test/benchmark reachability and reaching-entry counts.
cstat complexity --json --path . — per-function cyclomatic, cognitive, nesting, parameter, and line metrics.

Advanced / legacy commands

Use these only when the focused report points to a question they answer:

cstat advanced summary --json --path . — previous broad dashboard.
cstat advanced flow --json --path . — raw static call graph.
cstat advanced graph --json --path . — graph centrality, SCCs, PageRank.
cstat advanced flow-heatmap --json --path . — previous random-walk heatmap.
cstat advanced circuits --json --path . — call-graph community detection.
cstat advanced redundancy --json --path . — similar/duplicate function candidates.
cstat advanced dist --json --path . — metric histograms/correlation views.
cstat advanced map --json --path . — terminal architecture map.
cstat advanced dump --path . — previous diagnostic-score dump.
cstat advanced guide <topic> — metric reference material.

Cleanup workflow

Run cstat report --json --path ..
Read the focused sections in this order:
- line counts: find oversized files first;
- symbols: find files with too many definitions;
- dependency matrix: find high fan-in/fan-out modules and cycles;
- dead code: review cold candidates before deleting;
- test reachability: compare code surface against what tests/benches can statically reach.
Plan one cleanup stage at a time.
After each stage, rerun cstat report --json --path . and the project's own build/tests. cstat metrics do not prove correctness.

Safety rules

Dead-code findings are static. Check macros, trait-object calls, public API use, build scripts, and string-based dispatch before deleting.
Test-reachability counts are static entry-root reachability: how many test/benchmark roots can reach a function or edge. They are not runtime hit-count profiling.
Dependency edges come from source-level use/mod relationships. Generated code and macro expansion can hide edges.
For exact loc code_lines rules and JSON fields, run cstat loc --explain or cstat loc --explain --json; that command is the canonical contract.
Prefer targeted reductions: remove dead code, split large files, move symbols across modules, then reduce per-function complexity.

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