diff --git a/cli/__tests__/adapters.claude.environment.test.mjs b/cli/__tests__/adapters.claude.environment.test.mjs
index 0b0cdce65b..0081dc97db 100644
--- a/cli/__tests__/adapters.claude.environment.test.mjs
+++ b/cli/__tests__/adapters.claude.environment.test.mjs
@@ -130,7 +130,7 @@ describe('claude adapter — ctx.environment', () => {
   test('TASK-174: a warmed MCP home makes claude execute the home build, not npx @latest', async () => {
     // The control for this arm is the rest of this file: every other test here
     // declares the shipped `npx -y @commonlyai/mcp@latest`, and the jest setup
-    // points COMMONLY_MCP_HOME at an EMPTY dir, so they all see it unchanged.
+    // points COMMONLY_MCP_HOME at a home with no installed build, so they all see it unchanged.
     // This arm is the same call with a populated home.
     const home = fs.mkdtempSync(path.join(os.tmpdir(), 'cli-mcp-home-'));
     const pkgDir = path.join(home, '0.3.13', 'node_modules', '@commonlyai', 'mcp');
@@ -140,6 +140,7 @@ describe('claude adapter — ctx.environment', () => {
     }));
     fs.writeFileSync(path.join(pkgDir, 'src', 'index.js'), '');
     fs.writeFileSync(path.join(home, 'current'), '0.3.13\n');
+    fs.writeFileSync(path.join(home, '.warm.lock'), 'warming\n');
     const previous = process.env.COMMONLY_MCP_HOME;
     process.env.COMMONLY_MCP_HOME = home;
     try {
@@ -181,7 +182,7 @@ describe('claude adapter — ctx.environment', () => {
   });
 
   test('TASK-174: the cold path materialises an EXACT spec — the spawn never names @latest', async () => {
-    // The home holds nothing but the warm's registry cache: an empty home is the
+    // The home has no installed build, only the registry cache and warm lock: this is the
     // one state where the declaration still runs through npx, and `@latest` is
     // the one spec whose npx dir every seat shares and a publish rewrites in
     // place. So the config this adapter writes names the version the host
@@ -192,6 +193,7 @@ describe('claude adapter — ctx.environment', () => {
     fs.writeFileSync(path.join(home, '.registry.json'), JSON.stringify({
       version: '0.3.13', checkedAt: Date.now(),
     }));
+    fs.writeFileSync(path.join(home, '.warm.lock'), 'warming\n');
     const previous = process.env.COMMONLY_MCP_HOME;
     process.env.COMMONLY_MCP_HOME = home;
     try {
@@ -249,6 +251,7 @@ describe('claude adapter — ctx.environment', () => {
     }));
     fs.writeFileSync(path.join(pkgDir, 'src', 'index.js'), '');
     fs.writeFileSync(path.join(home, 'current'), '0.3.7\n');
+    fs.writeFileSync(path.join(home, '.warm.lock'), 'warming\n');
     const previous = process.env.COMMONLY_MCP_HOME;
     process.env.COMMONLY_MCP_HOME = home;
     try {
diff --git a/cli/__tests__/adapters.codex.test.mjs b/cli/__tests__/adapters.codex.test.mjs
index 2beca25ccf..f5ebea80e7 100644
--- a/cli/__tests__/adapters.codex.test.mjs
+++ b/cli/__tests__/adapters.codex.test.mjs
@@ -196,6 +196,7 @@ describe('codex adapter — spawn()', () => {
     }));
     await writeFile(join(pkgDir, 'src', 'index.js'), '');
     await writeFile(join(home, 'current'), '0.3.13\n');
+    await writeFile(join(home, '.warm.lock'), 'warming\n');
     const previous = process.env.COMMONLY_MCP_HOME;
     process.env.COMMONLY_MCP_HOME = home;
     try {
diff --git a/cli/__tests__/adapters.pi.test.mjs b/cli/__tests__/adapters.pi.test.mjs
index dfa5668557..b6b640f343 100644
--- a/cli/__tests__/adapters.pi.test.mjs
+++ b/cli/__tests__/adapters.pi.test.mjs
@@ -354,7 +354,7 @@ describe('helpers', () => {
   });
   test('TASK-174: a warmed MCP home makes pi exec the home build, not npx @latest', async () => {
     // Control: the helper tests in this file call resolveMcpServers with the
-    // empty home the jest setup installs, and see `npx -y @commonlyai/mcp@latest`
+    // home without an installed build from jest setup, and see `npx -y @commonlyai/mcp@latest`
     // carried through unchanged. This arm is the same call with a real home.
     const home = await mkdtemp(join(tmpdir(), 'cli-mcp-home-'));
     const pkgDir = join(home, '0.3.13', 'node_modules', '@commonlyai', 'mcp');
@@ -364,6 +364,7 @@ describe('helpers', () => {
     }));
     await writeFile(join(pkgDir, 'src', 'index.js'), '');
     await writeFile(join(home, 'current'), '0.3.13\n');
+    await writeFile(join(home, '.warm.lock'), 'warming\n');
     const previous = process.env.COMMONLY_MCP_HOME;
     process.env.COMMONLY_MCP_HOME = home;
     try {
diff --git a/cli/jest.setup.cjs b/cli/jest.setup.cjs
index 591c1ef6ff..62e7dc707f 100644
--- a/cli/jest.setup.cjs
+++ b/cli/jest.setup.cjs
@@ -9,12 +9,15 @@
  * adapter tests that pin the npx form would fail for a reason that has nothing
  * to do with the change.
  *
- * Pointing the home at a fresh empty dir per run restores that: the default
- * `COMMONLY_MCP_HOME` is the real `~/.commonly/mcp`, and tests that want a
- * warmed home set up their own temp dir and pass it in.
+ * Pointing the home at a fresh dir with no installed build per run restores
+ * that: the default `COMMONLY_MCP_HOME` is the real `~/.commonly/mcp`, and
+ * tests that want a warmed home set up their own temp dir and pass it in.
+ * The lock suppresses an unrelated detached warm child that could still write
+ * to this fixture after Jest has moved on to the next test file.
  */
-const { mkdtempSync } = require('node:fs');
+const { mkdtempSync, writeFileSync } = require('node:fs');
 const { tmpdir } = require('node:os');
 const { join } = require('node:path');
 
 process.env.COMMONLY_MCP_HOME = mkdtempSync(join(tmpdir(), 'commonly-mcp-home-jest-'));
+writeFileSync(join(process.env.COMMONLY_MCP_HOME, '.warm.lock'), 'warming\n');