diff --git a/tools/alignment/audit_clause_coverage.test.ts b/tools/alignment/audit_clause_coverage.test.ts
new file mode 100644
index 000000000..d194f2455
--- /dev/null
+++ b/tools/alignment/audit_clause_coverage.test.ts
@@ -0,0 +1,172 @@
+// audit_clause_coverage.test.ts — tests for alignment-clause coverage audit.
+//
+// B-0058 slice: adds test coverage for the clause-extraction regex,
+// the audit() integration function, and the main() CLI arg parsing.
+//
+// Run: bun test tools/alignment/audit_clause_coverage.test.ts
+
+import { describe, expect, test } from "bun:test";
+import {
+  ALL_CLAUSES,
+  audit,
+  extractClauses,
+  main,
+} from "./audit_clause_coverage.ts";
+
+describe("extractClauses", () => {
+  test("extracts single clause from text", () => {
+    expect(extractClauses("This references HC-1 explicitly.")).toEqual([
+      "HC-1",
+    ]);
+  });
+
+  test("extracts multiple clauses in canonical order", () => {
+    const content = "We cite DIR-3 and HC-2 and SD-5 here.";
+    const result = extractClauses(content);
+    expect(result).toEqual(["HC-2", "SD-5", "DIR-3"]);
+  });
+
+  test("deduplicates repeated clauses", () => {
+    const content = "HC-1 is mentioned, then HC-1 again, then HC-1.";
+    expect(extractClauses(content)).toEqual(["HC-1"]);
+  });
+
+  test("returns empty array for content with no clauses", () => {
+    expect(extractClauses("No alignment clauses here.")).toEqual([]);
+  });
+
+  test("does not match partial clause IDs", () => {
+    expect(extractClauses("HC-0 SD-0 DIR-0 DIR-6 HC-8 SD-10")).toEqual([]);
+  });
+
+  test("matches clauses at word boundaries", () => {
+    expect(extractClauses("(HC-7) [SD-1] {DIR-5}")).toEqual([
+      "HC-7",
+      "SD-1",
+      "DIR-5",
+    ]);
+  });
+
+  test("returns results ordered by ALL_CLAUSES, not input order", () => {
+    const content = "DIR-5 SD-9 HC-1";
+    const result = extractClauses(content);
+    expect(result).toEqual(["HC-1", "SD-9", "DIR-5"]);
+  });
+
+  test("handles all 21 clauses", () => {
+    const content = ALL_CLAUSES.join(" ");
+    expect(extractClauses(content)).toEqual([...ALL_CLAUSES]);
+  });
+});
+
+describe("ALL_CLAUSES", () => {
+  test("has exactly 21 clauses", () => {
+    expect(ALL_CLAUSES).toHaveLength(21);
+  });
+
+  test("covers HC-1..HC-7", () => {
+    for (let i = 1; i <= 7; i++) {
+      expect(ALL_CLAUSES).toContain(`HC-${String(i)}`);
+    }
+  });
+
+  test("covers SD-1..SD-9", () => {
+    for (let i = 1; i <= 9; i++) {
+      expect(ALL_CLAUSES).toContain(`SD-${String(i)}`);
+    }
+  });
+
+  test("covers DIR-1..DIR-5", () => {
+    for (let i = 1; i <= 5; i++) {
+      expect(ALL_CLAUSES).toContain(`DIR-${String(i)}`);
+    }
+  });
+});
+
+describe("audit() integration", () => {
+  test("returns a valid AuditResult shape", () => {
+    const result = audit();
+    expect(result.schema).toBe("alignment-clause-coverage-v2");
+    expect(typeof result.totalSurfaces).toBe("number");
+    expect(typeof result.totalWithZero).toBe("number");
+    expect(result.totalClauses).toBe(ALL_CLAUSES.length);
+    expect(Array.isArray(result.surfaces)).toBe(true);
+    expect(Array.isArray(result.uncitedClauses)).toBe(true);
+  });
+
+  test("finds at least one surface", () => {
+    const result = audit();
+    expect(result.totalSurfaces).toBeGreaterThan(0);
+  });
+
+  test("every surface has expected fields", () => {
+    const result = audit();
+    for (const s of result.surfaces) {
+      expect(["skill", "agent", "backlog"]).toContain(s.kind);
+      expect(typeof s.name).toBe("string");
+      expect(s.name.length).toBeGreaterThan(0);
+      expect(typeof s.path).toBe("string");
+      expect(Array.isArray(s.clausesCited)).toBe(true);
+      expect(typeof s.clauseCount).toBe("number");
+      expect(s.clauseCount).toBe(s.clausesCited.length);
+    }
+  });
+
+  test("totalWithZero equals count of zero-citation surfaces", () => {
+    const result = audit();
+    const zeroCount = result.surfaces.filter(
+      (s) => s.clauseCount === 0,
+    ).length;
+    expect(result.totalWithZero).toBe(zeroCount);
+  });
+
+  test("uncitedClauses are a subset of ALL_CLAUSES", () => {
+    const result = audit();
+    for (const c of result.uncitedClauses) {
+      expect(ALL_CLAUSES).toContain(c);
+    }
+  });
+
+  test("cited clauses in surfaces are all valid clause IDs", () => {
+    const result = audit();
+    for (const s of result.surfaces) {
+      for (const c of s.clausesCited) {
+        expect(ALL_CLAUSES).toContain(c);
+      }
+    }
+  });
+});
+
+describe("main() CLI", () => {
+  test("returns 0 with no args", () => {
+    expect(main([])).toBe(0);
+  });
+
+  test("returns 0 with --help", () => {
+    expect(main(["--help"])).toBe(0);
+  });
+
+  test("returns 0 with --json", () => {
+    expect(main(["--json"])).toBe(0);
+  });
+
+  test("returns 0 with --md", () => {
+    expect(main(["--md"])).toBe(0);
+  });
+
+  test("returns 2 for unknown arg", () => {
+    expect(main(["--bad-flag"])).toBe(2);
+  });
+
+  test("returns 2 when --gate has no value", () => {
+    expect(main(["--gate"])).toBe(2);
+  });
+
+  test("returns 0 with --gate 0 (trivially satisfied)", () => {
+    expect(main(["--gate", "0"])).toBe(0);
+  });
+
+  test("returns 1 with --gate 999 (impossible threshold)", () => {
+    expect(main(["--gate", "999"])).toBe(1);
+  });
+});
diff --git a/tools/alignment/audit_clause_coverage.ts b/tools/alignment/audit_clause_coverage.ts
index 03cfb162f..a9e59b2f4 100644
--- a/tools/alignment/audit_clause_coverage.ts
+++ b/tools/alignment/audit_clause_coverage.ts
@@ -31,7 +31,7 @@ import { spawnSync } from "node:child_process";
 
 type AuditExitCode = 0 | 1 | 2;
 
-const ALL_CLAUSES: readonly string[] = [
+export const ALL_CLAUSES: readonly string[] = [
   "HC-1", "HC-2", "HC-3", "HC-4", "HC-5", "HC-6", "HC-7",
   "SD-1", "SD-2", "SD-3", "SD-4", "SD-5", "SD-6", "SD-7", "SD-8", "SD-9",
   "DIR-1", "DIR-2", "DIR-3", "DIR-4", "DIR-5",
@@ -113,7 +113,7 @@ function parseArgs(argv: readonly string[]): ParseResult {
   return { kind: "args", args: state };
 }
 
-function extractClauses(content: string): readonly string[] {
+export function extractClauses(content: string): readonly string[] {
   const found = new Set<string>();
   const re = /\b(HC-[1-7]|SD-[1-9]|DIR-[1-5])\b/g;
   let match: RegExpExecArray | null;
diff --git a/tools/alignment/audit_clause_drift.test.ts b/tools/alignment/audit_clause_drift.test.ts
new file mode 100644
index 000000000..c870afaeb
--- /dev/null
+++ b/tools/alignment/audit_clause_drift.test.ts
@@ -0,0 +1,50 @@
+// audit_clause_drift.test.ts — tests for alignment-clause drift detector.
+//
+// B-0058 slice: adds test coverage for the drift detector's CLI
+// interface and baseline no-drift assertion.
+//
+// Run: bun test tools/alignment/audit_clause_drift.test.ts
+
+import { describe, expect, test } from "bun:test";
+import { main } from "./audit_clause_drift.ts";
+
+describe("main() CLI", () => {
+  test("returns 0 with --help", () => {
+    expect(main(["--help"])).toBe(0);
+  });
+
+  test("returns 2 for unknown arg", () => {
+    expect(main(["--bad-flag"])).toBe(2);
+  });
+
+  test("returns 2 when --base has no value", () => {
+    expect(main(["--base"])).toBe(2);
+  });
+
+  test("returns 2 when --head has no value", () => {
+    expect(main(["--head"])).toBe(2);
+  });
+});
+
+describe("no-drift baseline", () => {
+  test("HEAD vs HEAD shows zero drift", () => {
+    const code = main(["--base", "HEAD", "--head", "HEAD"]);
+    expect(code).toBe(0);
+  });
+
+  test("HEAD vs HEAD with --json returns 0", () => {
+    const code = main(["--base", "HEAD", "--head", "HEAD", "--json"]);
+    expect(code).toBe(0);
+  });
+
+  test("HEAD vs HEAD with --md returns 0", () => {
+    const code = main(["--base", "HEAD", "--head", "HEAD", "--md"]);
+    expect(code).toBe(0);
+  });
+});
+
+describe("default base ref", () => {
+  test("returns 0 with no args (defaults to main vs HEAD)", () => {
+    expect(main([])).toBe(0);
+  });
+});