P1: add affected tests command

README.md

@@ -87,6 +87,9 @@ node ./dist/cli.js review --base HEAD --head WORKTREE --summary
 # broader blast-radius map when the review packet needs expansion
 node ./dist/cli.js impact --base HEAD --head WORKTREE --pretty
 
+# focused affected-test list for current edits
+node ./dist/cli.js affected --base HEAD --head WORKTREE --quiet
+
 # one-call answer for a concrete repo question
 node ./dist/cli.js explore "how does auth reach db?" --root . --pretty
 
@@ -138,6 +141,7 @@ Use these as starting points, then see [docs/cli.md](./docs/cli.md) for all flag
 # fastest code-review handoff for current edits
 codegraph review --base HEAD --head WORKTREE --summary
 codegraph impact --base HEAD --head WORKTREE --pretty
+codegraph affected --base HEAD --head WORKTREE --quiet
 
 # repo question, orientation, and bounded follow-up
 codegraph explore "how does auth reach db?" --root . --pretty

codegraph-skill/codegraph/SKILL.md

@@ -9,7 +9,7 @@ Use Codegraph for structure-aware repo questions:
 
 - repo overview, hotspots, cycles, unresolved imports, and public API surface
 - symbol navigation with definitions, references, dependencies, and paths
-- PR or worktree impact review with candidate tests and risk signals
+- PR or worktree impact review with candidate tests, affected test lists, and risk signals
 - duplicate cleanup and refactor-risk triage
 - bounded agent context through explore, orientation, search, packets, explain, and MCP
 
@@ -40,6 +40,7 @@ Then choose the smallest useful follow-up:
 - references: `codegraph refs --file <file> --line <line> --col <column> --pretty`
 - duplicates: `codegraph duplicates --root . ./src --profile cleanup`
 - impact: `codegraph impact --base HEAD --head WORKTREE --pretty`
+- affected tests: `codegraph affected --base HEAD --head WORKTREE --quiet`
 - review: `codegraph review --base HEAD --head WORKTREE --summary`
 - drift: `codegraph drift ./src --base origin/main --head HEAD --pretty --graph-edges summary --public-api removals`
 - installer: `codegraph install --target codex,claude --dry-run`
@@ -64,6 +65,7 @@ Current high-value surfaces:
 - `orient --pretty`: ranked first-turn focus targets with copyable follow-ups
 - `impact --pretty`: ranked "what could this break?" map
 - `review --summary`: compact reviewer handoff
+- `affected --quiet`: deterministic path-only test selection for a changed-file set
 - `duplicates --profile cleanup`: refactor ROI ordering
 - `duplicates --json`: full grouped duplicate data
 

docs/cli.md

@@ -14,6 +14,7 @@ Default workflow:
 
 - code review: `codegraph review --base HEAD --head WORKTREE --summary`
 - blast-radius follow-up: `codegraph impact --base HEAD --head WORKTREE --pretty`
+- affected tests: `codegraph affected --base HEAD --head WORKTREE --quiet`
 - unfamiliar repo: `codegraph explore "how does auth reach db?" --root . --pretty`
 - first-turn map: `codegraph orient --root . --budget small --pretty`
 - targeted follow-up: `codegraph search "<query>" --json` then `codegraph explain <handle|file|symbol>`
@@ -56,6 +57,7 @@ Cache and manifest reuse is rooted at `--root`. Reusing a project root lets comm
 # Fast code-review handoff for current local edits
 codegraph review --base HEAD --head WORKTREE --summary
 codegraph impact --base HEAD --head WORKTREE --pretty
+codegraph affected --base HEAD --head WORKTREE --quiet
 
 # First-pass repo summary and next-step suggestions
 codegraph orient --root . --budget small --pretty
@@ -125,6 +127,19 @@ Graph, index, and review reports include `backend.native.byLanguage` so native u
 - `uninit` removes only recognized lifecycle state by default. It refuses unknown `.codegraph/` entries unless `--force` is passed.
 - Lifecycle commands accept either a positional project path or `--root <path>`. They reject using both together because lifecycle manifests always describe one project boundary, not include-root subsets.
 
+### Affected tests
+
+- `affected` maps changed source files to likely test files by traversing reverse dependencies through the project graph. It also includes directly changed test files at depth 0.
+- Inputs can be positional files, newline-delimited `--stdin`, or a Git range with `--base <ref> --head <ref>`. Paths are normalized under `--root` and output as project-root-relative paths.
+- Use `--depth <n>` to expand transitive reverse dependencies, `--filter <glob>` to restrict returned test paths, `--quiet` for path-only output, or `--json` for `schemaVersion: 1`, `changedFiles`, `affectedTests`, and `omittedCounts`.
+
+```bash
+codegraph affected src/auth.ts src/db.ts
+codegraph affected --stdin --quiet
+codegraph affected --base main --head HEAD --json
+codegraph affected --base HEAD --head WORKTREE --filter "tests/**/*.test.ts" --quiet
+```
+
 ### Symbols, navigation, grep, and chunking
 
 ```bash

src/cli.ts

@@ -27,6 +27,7 @@ import {
   type CliRuntime,
   type CommandReport,
 } from "./cli/context.js";
+import { handleAffectedCommand } from "./cli/affected.js";
 import { buildDoctorReport } from "./cli/doctor.js";
 import { handleDriftCommand } from "./cli/drift.js";
 import { handleDuplicatesCommand } from "./cli/duplicates.js";
@@ -911,6 +912,23 @@ async function runCliWithActiveRuntime(rawArgs: string[]) {
     return;
   }
 
+  if (cmd === "affected") {
+    await handleAffectedCommand({
+      projectRootFs,
+      buildOptions: buildAgentOptions(),
+      positionals: parsed.positionals,
+      getOpt,
+      hasFlag,
+      parsedOptions: parsed.options,
+      readStdin: readCliStdin,
+      writeJSONLine,
+      writeStdoutLine,
+      writeStderrLine,
+      exit: exitCli,
+    });
+    return;
+  }
+
   // Review entry point: CLI workflow for review reports.
   if (cmd === "review") {
     const commandReport: CommandReport | undefined = reportEnabled ? { command: "review", timings: {} } : undefined;