chore: import upstream snapshot with attribution

__tests__/explore-blast-radius.test.ts

@@ -0,0 +1,73 @@
+/**
+ * codegraph_explore blast-radius section.
+ *
+ * explore now appends a compact, always-on "Blast radius" for the entry
+ * symbols: who depends on each (locations only — no source) and which test
+ * files cover it, so the agent knows what to update/verify before editing
+ * without a separate impact call. Symbols with no dependents are skipped, and
+ * the section is omitted entirely when nothing qualifies.
+ */
+import { describe, it, expect, beforeEach, afterEach } from 'vitest';
+import * as fs from 'fs';
+import * as path from 'path';
+import * as os from 'os';
+import CodeGraph from '../src/index';
+import { ToolHandler } from '../src/mcp/tools';
+
+describe('codegraph_explore — blast radius', () => {
+  let testDir: string;
+  let cg: CodeGraph;
+  let handler: ToolHandler;
+
+  beforeEach(async () => {
+    testDir = fs.mkdtempSync(path.join(os.tmpdir(), 'codegraph-blast-'));
+    const src = path.join(testDir, 'src');
+    fs.mkdirSync(src, { recursive: true });
+
+    // `target` is depended on by a sibling (caller) and a test file.
+    fs.writeFileSync(
+      path.join(src, 'feature.ts'),
+      `export function target() { return 1; }\n` +
+      `export function caller() { return target(); }\n`,
+    );
+    fs.writeFileSync(
+      path.join(src, 'feature.test.ts'),
+      `import { target } from './feature';\n` +
+      `export function checkTarget() { return target(); }\n`,
+    );
+    // A leaf with no dependents — must NOT show up in the blast radius.
+    fs.writeFileSync(
+      path.join(src, 'leaf.ts'),
+      `export function lonelyLeaf() { return 42; }\n`,
+    );
+
+    cg = CodeGraph.initSync(testDir, { config: { include: ['**/*.ts'], exclude: [] } });
+    await cg.indexAll();
+    handler = new ToolHandler(cg);
+  });
+
+  afterEach(() => {
+    if (cg) cg.destroy();
+    if (fs.existsSync(testDir)) fs.rmSync(testDir, { recursive: true, force: true });
+  });
+
+  it('lists dependents (locations only) and covering tests for an entry symbol', async () => {
+    const res = await handler.execute('codegraph_explore', { query: 'target' });
+    const text = res.content[0].text;
+
+    expect(text).toContain('**Blast radius');
+    expect(text).toContain('`target`');
+    expect(text).toMatch(/caller/); // a caller count is reported
+    // It names WHERE (the caller file) — not the caller's source body.
+    expect(text).toContain('feature.ts');
+    // Test coverage is surfaced (either the covering test file, or the warning).
+    expect(text).toMatch(/tests:.*feature\.test\.ts|no covering tests/);
+  });
+
+  it('omits symbols that have no dependents from the blast radius', async () => {
+    const res = await handler.execute('codegraph_explore', { query: 'lonelyLeaf' });
+    const text = res.content[0].text;
+    // lonelyLeaf has zero callers — it must never appear under a blast-radius bullet.
+    expect(text).not.toMatch(/Blast radius[\s\S]*`lonelyLeaf`/);
+  });
+});