test(telemetry): enforce no-repo-identity-egress invariant

Pins the contract that repo/branch identity in the synced skill-usage.jsonl is
stripped before the remote POST. Three checks: a floor (the three known fields),
coverage (every repo/branch field a producer writes into skill-usage.jsonl is
stripped, so a future producer rename can't silently leak), and behavior (runs
the actual sed strip expressions over a sample event). Scoped to the synced
file, so the local-only timeline branch field is correctly excluded.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

test/telemetry-repo-strip.test.ts

@@ -0,0 +1,137 @@
+/**
+ * Telemetry "no repo identity egress" invariant.
+ *
+ * The telemetry consent copy promises a user's repo name is recorded locally
+ * only and stripped before any upload (scripts/resolvers/preamble/
+ * generate-telemetry-prompt.ts). Two producers write repo/branch identity into
+ * the local skill-usage.jsonl:
+ *
+ *   - the preamble epilogue        → "repo"
+ *     (scripts/resolvers/preamble/generate-preamble-bash.ts)
+ *   - gstack-telemetry-log         → "_repo_slug", "_branch"
+ *     (bin/gstack-telemetry-log)
+ *
+ * gstack-telemetry-sync MUST strip every one of those fields before the remote
+ * POST (bin/gstack-telemetry-sync). This test enforces that contract three ways:
+ *
+ *   1. Coverage — every repo/branch field the producers emit is also stripped.
+ *      Catches "added a new repo field, forgot to strip it" (the rename-to-_repo
+ *      landmine, or any future producer drift).
+ *   2. Behavior — run the ACTUAL sed strip expressions from the sync script over
+ *      a sample event line and assert no repo/branch field survives, while benign
+ *      fields do. Catches a broken/edited regex, not just a missing line.
+ *   3. Floor — the three known fields are always in the stripped set, so deleting
+ *      a strip rule fails CI even if a producer also stops emitting it.
+ */
+
+import { describe, test, expect } from 'bun:test';
+import { spawnSync } from 'bun';
+import fs from 'fs';
+import path from 'path';
+
+const ROOT = path.resolve(__dirname, '..');
+const SYNC = path.join(ROOT, 'bin', 'gstack-telemetry-sync');
+const PREAMBLE = path.join(ROOT, 'scripts', 'resolvers', 'preamble', 'generate-preamble-bash.ts');
+const TEL_LOG = path.join(ROOT, 'bin', 'gstack-telemetry-log');
+
+// Fields that identify the user's repo/branch. The promise is that NONE of
+// these reach the network. Add to this floor if a new identity field is born.
+const REPO_IDENTITY_FLOOR = ['repo', '_repo_slug', '_branch'];
+
+const isRepoIdentity = (field: string) => /repo|branch/i.test(field);
+
+/** Pull every `sed -e 's/.../g'` expression out of the sync script. */
+function extractSedExprs(scriptText: string): string[] {
+  return [...scriptText.matchAll(/-e\s+'(s\/[^']*)'/g)].map((m) => m[1]);
+}
+
+/** The JSON key a strip expression targets, e.g. `,"repo":"[^"]*"` -> `repo`. */
+function fieldFromSedExpr(expr: string): string | null {
+  const m = expr.match(/,"([A-Za-z_][A-Za-z0-9_]*)":/);
+  return m ? m[1] : null;
+}
+
+/**
+ * Repo/branch JSON keys a producer writes INTO skill-usage.jsonl — the only
+ * file gstack-telemetry-sync reads and uploads. Scoped to the emission lines
+ * that target the synced file so local-only sinks (e.g. the timeline log, which
+ * carries "branch" but is never synced) don't count against the egress invariant.
+ */
+function emittedRepoFields(lines: string[]): string[] {
+  const text = lines.join('\n');
+  const keys = [...text.matchAll(/"([A-Za-z_][A-Za-z0-9_]*)":/g)].map((m) => m[1]);
+  return [...new Set(keys.filter(isRepoIdentity))];
+}
+
+describe('telemetry no-repo-identity-egress invariant', () => {
+  const syncText = fs.readFileSync(SYNC, 'utf-8');
+  const sedExprs = extractSedExprs(syncText);
+  const strippedRepoExprs = sedExprs.filter((e) => {
+    const f = fieldFromSedExpr(e);
+    return f !== null && isRepoIdentity(f);
+  });
+  const strippedFields = new Set(
+    strippedRepoExprs.map(fieldFromSedExpr).filter((f): f is string => f !== null),
+  );
+
+  test('floor: the three known repo-identity fields are stripped', () => {
+    for (const field of REPO_IDENTITY_FLOOR) {
+      expect(strippedFields.has(field)).toBe(true);
+    }
+  });
+
+  test('coverage: every repo/branch field the producers emit into skill-usage.jsonl is stripped', () => {
+    // Only emission lines that target the synced file (skill-usage.jsonl). The
+    // preamble appends directly; gstack-telemetry-log builds the synced event
+    // with a `printf '{"v":1,...` line into $JSONL_FILE (= skill-usage.jsonl).
+    const preambleSynced = fs
+      .readFileSync(PREAMBLE, 'utf-8')
+      .split('\n')
+      .filter((l) => l.includes('skill-usage.jsonl'));
+    const telLogSynced = fs
+      .readFileSync(TEL_LOG, 'utf-8')
+      .split('\n')
+      .filter((l) => l.includes('"v":1') || l.includes('skill-usage'));
+    const emitted = new Set<string>([
+      ...emittedRepoFields(preambleSynced),
+      ...emittedRepoFields(telLogSynced),
+    ]);
+    // The preamble must emit "repo" — guards against the test silently passing
+    // because a regex stopped matching the producer.
+    expect(emitted.has('repo')).toBe(true);
+    for (const field of emitted) {
+      expect(
+        strippedFields.has(field),
+        `producer emits repo-identity field "${field}" but gstack-telemetry-sync does not strip it (would leak to remote)`,
+      ).toBe(true);
+    }
+  });
+
+  test('behavior: the real sed expressions remove repo identity, keep benign fields', () => {
+    const sample =
+      '{"v":1,"ts":"2026-06-02T00:00:00Z","skill":"design-shotgun",' +
+      '"repo":"my-secret-repo","_repo_slug":"acme-my-secret-repo","_branch":"feature-x",' +
+      '"sessions":3,"installation_id":"abc123"}';
+
+    const sedArgs: string[] = [];
+    for (const e of strippedRepoExprs) {
+      sedArgs.push('-e', e);
+    }
+    const out = spawnSync(['sed', ...sedArgs], {
+      stdin: Buffer.from(sample),
+    });
+    const cleaned = out.stdout.toString();
+
+    // No repo/branch identity survives, value or key.
+    expect(cleaned).not.toContain('my-secret-repo');
+    expect(cleaned).not.toContain('feature-x');
+    expect(cleaned).not.toContain('"repo"');
+    expect(cleaned).not.toContain('_repo_slug');
+    expect(cleaned).not.toContain('_branch');
+
+    // Benign fields are untouched — the strip is surgical, not a blanket wipe.
+    expect(cleaned).toContain('"skill":"design-shotgun"');
+    expect(cleaned).toContain('"sessions":3');
+    expect(cleaned).toContain('"ts":"2026-06-02T00:00:00Z"');
+  });
+});