diff --git a/get-shit-done/bin/lib/project-root.generated.cjs b/get-shit-done/bin/lib/project-root.generated.cjs
index bb85c50d3..4f3c45d2c 100644
--- a/get-shit-done/bin/lib/project-root.generated.cjs
+++ b/get-shit-done/bin/lib/project-root.generated.cjs
@@ -3,7 +3,7 @@
 /**
  * GENERATED FILE — DO NOT EDIT.
  *
- * Source: sdk/src/project-root/index.ts
+ * Source: sdk/src/runtime/project-root.ts
  * Regenerate: cd sdk && npm run gen:project-root
  *
  * Project-Root Resolution Module — resolves a project root from a starting
diff --git a/sdk/scripts/gen-project-root.mjs b/sdk/scripts/gen-project-root.mjs
index 660ca3de9..7c781c729 100644
--- a/sdk/scripts/gen-project-root.mjs
+++ b/sdk/scripts/gen-project-root.mjs
@@ -2,7 +2,7 @@
 /**
  * Generator for the Project-Root Resolution Module CJS artifact.
  *
- * Imports the compiled ESM output from sdk/dist/project-root/index.js,
+ * Imports the compiled ESM output from sdk/dist/runtime/project-root.js,
  * captures findProjectRoot via Function.prototype.toString(), then emits
  * get-shit-done/bin/lib/project-root.generated.cjs.
  *
@@ -14,14 +14,14 @@ import { writeFile } from 'node:fs/promises';
 import { fileURLToPath } from 'node:url';
 import { requireFreshDist } from './_gen-helpers.mjs';
 
-requireFreshDist('sdk/dist/project-root/index.js', 'sdk/src/project-root/index.ts');
+requireFreshDist('sdk/dist/runtime/project-root.js', 'sdk/src/runtime/project-root.ts');
 
 const BANNER = `'use strict';
 
 /**
  * GENERATED FILE — DO NOT EDIT.
  *
- * Source: sdk/src/project-root/index.ts
+ * Source: sdk/src/runtime/project-root.ts
  * Regenerate: cd sdk && npm run gen:project-root
  *
  * Project-Root Resolution Module — resolves a project root from a starting
@@ -41,7 +41,7 @@ const BANNER = `'use strict';
  * duplicating the logic.
  */
 export async function buildProjectRootCjs() {
-  const distUrl = new URL('../dist/project-root/index.js', import.meta.url);
+  const distUrl = new URL('../dist/runtime/project-root.js', import.meta.url);
   const { findProjectRoot, FIND_PROJECT_ROOT_MAX_DEPTH } = await import(distUrl.href);
 
   const findProjectRootBody = findProjectRoot.toString();
diff --git a/sdk/src/query/helpers.ts b/sdk/src/query/helpers.ts
index f1d3526c5..a8db4b0ec 100644
--- a/sdk/src/query/helpers.ts
+++ b/sdk/src/query/helpers.ts
@@ -502,9 +502,9 @@ export function planningPaths(projectDir: string, workstream?: string): Planning
 }
 
 // ─── findProjectRoot (multi-repo .planning resolution) ─────────────────────
-// Implementation lives in sdk/src/project-root/index.ts — re-exported here
+// Implementation lives in sdk/src/runtime/project-root.ts — re-exported here
 // so that existing consumers of helpers.ts continue to work unchanged.
-export { findProjectRoot } from '../project-root/index.js';
+export { findProjectRoot } from '../runtime/project-root.js';
 
 // ─── resolvePathUnderProject ───────────────────────────────────────────────
 
diff --git a/sdk/src/project-root/index.test.ts b/sdk/src/runtime/project-root.test.ts
similarity index 98%
rename from sdk/src/project-root/index.test.ts
rename to sdk/src/runtime/project-root.test.ts
index 01b8cce60..3a8bf2687 100644
--- a/sdk/src/project-root/index.test.ts
+++ b/sdk/src/runtime/project-root.test.ts
@@ -1,5 +1,5 @@
 /**
- * Pinning tests for sdk/src/project-root/index.ts
+ * Pinning tests for sdk/src/runtime/project-root.ts
  *
  * These tests pin the behaviour of findProjectRoot before the CJS refactor
  * in Cycle 2. They must remain GREEN throughout (never bend the implementation
@@ -14,7 +14,7 @@ import { describe, it, expect, beforeEach, afterEach } from 'vitest';
 import { mkdtemp, rm, writeFile, mkdir } from 'node:fs/promises';
 import { join } from 'node:path';
 import { tmpdir } from 'node:os';
-import { findProjectRoot } from './index.js';
+import { findProjectRoot } from './project-root.js';
 
 describe('findProjectRoot (project-root module)', () => {
   let workspace: string;
diff --git a/sdk/src/project-root/index.ts b/sdk/src/runtime/project-root.ts
similarity index 99%
rename from sdk/src/project-root/index.ts
rename to sdk/src/runtime/project-root.ts
index 5291ce92e..5e86cdcdb 100644
--- a/sdk/src/project-root/index.ts
+++ b/sdk/src/runtime/project-root.ts
@@ -10,7 +10,8 @@
  * Bounded by FIND_PROJECT_ROOT_MAX_DEPTH ancestors. Sync I/O.
  *
  * Source of truth for `findProjectRoot` — the CJS artifact at
- * get-shit-done/bin/lib/project-root.generated.cjs is generated from this file.
+ * get-shit-done/bin/lib/project-root.generated.cjs is generated from
+ * sdk/src/runtime/project-root.ts.
  */
 
 import { dirname, resolve, sep, relative, parse as parsePath } from 'node:path';
diff --git a/tests/gen-staleness-check.test.cjs b/tests/gen-staleness-check.test.cjs
index bd9c7094b..1afca8361 100644
--- a/tests/gen-staleness-check.test.cjs
+++ b/tests/gen-staleness-check.test.cjs
@@ -53,8 +53,8 @@ const GENERATORS = [
   },
   {
     script: 'gen-project-root.mjs',
-    dist: 'sdk/dist/project-root/index.js',
-    ts: 'sdk/src/project-root/index.ts',
+    dist: 'sdk/dist/runtime/project-root.js',
+    ts: 'sdk/src/runtime/project-root.ts',
   },
   {
     script: 'gen-workstream-inventory-builder.mjs',
diff --git a/tests/project-root-generator.test.cjs b/tests/project-root-generator.test.cjs
index 46302767b..a44bdd826 100644
--- a/tests/project-root-generator.test.cjs
+++ b/tests/project-root-generator.test.cjs
@@ -2,7 +2,7 @@
 /**
  * CJS parity test — project-root module
  *
- * For every fixture from sdk/src/project-root/index.test.ts, asserts that
+ * For every fixture from sdk/src/runtime/project-root.test.ts, asserts that
  * both the SDK (ESM, via dynamic import) and the generated CJS artifact
  * return identical paths. This confirms that the generator correctly
  * captures the function body and that all dependencies (sep, dirname,
@@ -21,7 +21,7 @@ const { findProjectRoot: findProjectRootCjs } = require('../get-shit-done/bin/li
 // SDK ESM — loaded once before all tests via dynamic import
 let findProjectRootSdk;
 before(async () => {
-  const mod = await import('../sdk/dist/project-root/index.js');
+  const mod = await import('../sdk/dist/runtime/project-root.js');
   findProjectRootSdk = mod.findProjectRoot;
 });