diff --git a/scripts/hooks/check-console-log.js b/scripts/hooks/check-console-log.js
index 28f3ac6db..021d617ef 100755
--- a/scripts/hooks/check-console-log.js
+++ b/scripts/hooks/check-console-log.js
@@ -14,7 +14,8 @@
  */
 
 const fs = require('fs');
-const { isGitRepo, getGitModifiedFiles, readFile, log } = require('../lib/utils');
+const path = require('path');
+const { isGitRepo, getGitModifiedFiles, readFile, log, runCommand } = require('../lib/utils');
 
 // Files where console.log is expected and should not trigger warnings
 const EXCLUDED_PATTERNS = [
@@ -27,6 +28,18 @@ const EXCLUDED_PATTERNS = [
 ];
 
 const MAX_DIRECT_STDIN_BYTES = 16 * 1024 * 1024;
+
+// This Stop hook inspects the session's working directory. Inherited GIT_*
+// variables from another Git process can silently redirect discovery and diff
+// commands to a different repository, so give every Git call the same clean env.
+function sessionGitOptions() {
+  const env = { ...process.env };
+  for (const name of Object.keys(env)) {
+    if (name.toUpperCase().startsWith('GIT_')) delete env[name];
+  }
+  return { env };
+}
+
 let data = '';
 let stdinBytes = 0;
 let oversized = false;
@@ -61,19 +74,23 @@ function passThroughAndExit() {
 
 process.stdin.on('end', () => {
   try {
-    if (!isGitRepo()) {
+    const gitOptions = sessionGitOptions();
+    if (!isGitRepo(gitOptions)) {
       passThroughAndExit();
       return;
     }
 
-    const files = getGitModifiedFiles(['\\.tsx?$', '\\.jsx?$'])
-      .filter(f => fs.existsSync(f))
+    // git reports paths from the repository root, and the session can run in a
+    // subdirectory of it, so read each file from the root.
+    const root = runCommand('git rev-parse --show-toplevel', gitOptions).output;
+    const files = getGitModifiedFiles(['\\.tsx?$', '\\.jsx?$'], gitOptions)
+      .filter(f => fs.existsSync(path.join(root, f)))
       .filter(f => !EXCLUDED_PATTERNS.some(pattern => pattern.test(f)));
 
     let hasConsole = false;
 
     for (const file of files) {
-      const content = readFile(file);
+      const content = readFile(path.join(root, file));
       if (content && content.includes('console.log')) {
         log(`[Hook] WARNING: console.log found in ${file}`);
         hasConsole = true;
diff --git a/scripts/hooks/config-protection.js b/scripts/hooks/config-protection.js
index 75a7a0781..8dce8b2ea 100644
--- a/scripts/hooks/config-protection.js
+++ b/scripts/hooks/config-protection.js
@@ -117,8 +117,9 @@ const PROTECTED_FILES = new Set([
 const PROTECTED_PATTERNS = [
   // eslint.config.base.mjs, prettier.config.shared.cjs, stylelint.config.local.js ...
   /^(eslint|prettier|stylelint|commitlint|oxlint)\.config(\.[A-Za-z0-9_-]+)*\.(js|mjs|cjs|ts|mts|cts)$/i,
-  // .eslintrc.base.json, .prettierrc.shared.yml ...
-  /^\.(eslintrc|prettierrc|stylelintrc|markdownlintrc)(\.[A-Za-z0-9_-]+)*\.(js|cjs|mjs|json|jsonc|yml|yaml|toml)$/i,
+  // .eslintrc.base.json, .prettierrc.shared.yml ... Prettier also reads
+  // `.prettierrc.ts`, `.mts`, `.cts` and `.json5`.
+  /^\.(eslintrc|prettierrc|stylelintrc|markdownlintrc)(\.[A-Za-z0-9_-]+)*\.(js|cjs|mjs|ts|mts|cts|json|jsonc|json5|yml|yaml|toml)$/i,
 ];
 
 function isProtectedName(basename) {
diff --git a/scripts/hooks/pre-bash-dev-server-block.js b/scripts/hooks/pre-bash-dev-server-block.js
index 06eb64020..c5c336e68 100755
--- a/scripts/hooks/pre-bash-dev-server-block.js
+++ b/scripts/hooks/pre-bash-dev-server-block.js
@@ -56,7 +56,9 @@ function readToken(input, startIndex) {
         continue;
       }
 
-      if (ch === '\\' && quote === '"' && index + 1 < input.length) {
+      // Inside double quotes, bash drops a backslash only before $ ` " \ or a
+      // newline, so `"echo ready\;"` keeps its `\;` for tmux.
+      if (ch === '\\' && quote === '"' && index + 1 < input.length && '$`"\\\n'.includes(input[index + 1])) {
         token += input[index + 1];
         index += 2;
         continue;
@@ -104,7 +106,7 @@ function normalizeCommandWord(token) {
   return base.replace(/\.(cmd|exe|bat)$/i, '');
 }
 
-function getLeadingCommandWord(segment) {
+function getLeadingCommand(segment) {
   let index = 0;
   let activeWrapper = null;
   let skipNextValue = false;
@@ -145,7 +147,7 @@ function getLeadingCommandWord(segment) {
       continue;
     }
 
-    return normalizedToken;
+    return { word: normalizedToken, end: index };
   }
 
   return null;
@@ -160,7 +162,19 @@ process.stdin.on('data', chunk => {
   }
 });
 
-const TMUX_LAUNCHER = /^\s*tmux\s+(new|new-session|new-window|split-window)\b/;
+// tmux commands, and their aliases, that run their shell command in a tmux pane,
+// where its output stays readable. run-shell and `tmux -c` run it without one.
+const TMUX_PANE_COMMANDS = new Set([
+  'new-session', 'new',
+  'new-window', 'neww',
+  'split-window', 'splitw',
+  'respawn-pane', 'respawnp',
+  'respawn-window', 'respawnw',
+  'send-keys', 'send'
+]);
+// tmux's own options that take a value (`-L work`, `-Lwork`, or the last of a
+// cluster such as `-vL work`).
+const TMUX_OPTION_VALUE_LETTERS = new Set(['f', 'L', 'S', 'T']);
 // Trailing (?![\w-]) rather than \b: \b treats a hyphen as a word boundary, so
 // `dev\b` matches the `dev` prefix of distinct scripts like `dev-setup` /
 // `dev-docs` / `dev-build` and wrongly blocks them. The lookahead still matches
@@ -199,10 +213,51 @@ function collectCheckSegments(cmd) {
   return segments;
 }
 
+/**
+ * Return true when the tmux invocation that starts at `index` runs the dev
+ * server in a pane. The tmux commands follow tmux's own options (`-L work`,
+ * `-f conf`), and the executable may come through a path or an env prefix, so
+ * this reads the parsed tokens instead of the start of the segment. A sequence
+ * (`new-session -d \; run-shell ...`) is exempt only when every command in it
+ * that runs the dev server is a pane command.
+ */
+function isTmuxPaneLaunch(segment, index) {
+  const tokens = [];
+  for (let parsed = readToken(segment, index); parsed; parsed = readToken(segment, parsed.end)) {
+    if (parsed.token) tokens.push(parsed.token);
+  }
+
+  let next = 0;
+  for (; next < tokens.length && isOptionToken(tokens[next]); next++) {
+    const letters = tokens[next].slice(1);
+    for (let i = 0; i < letters.length; i++) {
+      // -c runs its shell command without a pane.
+      if (letters[i] === 'c') return false;
+      if (TMUX_OPTION_VALUE_LETTERS.has(letters[i])) {
+        if (i === letters.length - 1) next++;
+        break;
+      }
+    }
+  }
+
+  // tmux ends a command at a `;` argument and at a `;` that ends an argument
+  // (`'npm run dev;'`); an escaped `\;` at the end stays literal.
+  const commands = [[]];
+  for (const token of tokens.slice(next)) {
+    const ends = token.endsWith(';') && !token.endsWith('\\;');
+    const value = ends ? token.slice(0, -1) : token;
+    if (value) commands[commands.length - 1].push(value);
+    if (ends) commands.push([]);
+  }
+  const devCommands = commands.filter(command => DEV_PATTERN.test(command.join(' ')));
+  return devCommands.length > 0 && devCommands.every(command => TMUX_PANE_COMMANDS.has(command[0]));
+}
+
 function isBlockedDevSegment(segment) {
-  const commandWord = getLeadingCommandWord(segment);
-  if (!commandWord || !DEV_COMMAND_WORDS.has(commandWord)) return false;
-  return DEV_PATTERN.test(segment) && !TMUX_LAUNCHER.test(segment);
+  const command = getLeadingCommand(segment);
+  if (!command || !DEV_COMMAND_WORDS.has(command.word)) return false;
+  if (!DEV_PATTERN.test(segment)) return false;
+  return !(command.word === 'tmux' && isTmuxPaneLaunch(segment, command.end));
 }
 
 process.stdin.on('end', () => {
diff --git a/scripts/hooks/stop-format-typecheck.js b/scripts/hooks/stop-format-typecheck.js
index 25341ed44..27adec981 100644
--- a/scripts/hooks/stop-format-typecheck.js
+++ b/scripts/hooks/stop-format-typecheck.js
@@ -128,10 +128,16 @@ function findTsConfigDir(filePath) {
   return null;
 }
 
+// tsc --pretty false starts each diagnostic with the file it is about:
+// `src/a.ts(1,14): error TS2322: ...`. Compare that path instead of looking for
+// the edited path anywhere in the line, which let a root `index.ts` claim the
+// errors of `src/index.ts`, and `src/utils.ts` those of `web/src/utils.ts`.
 function diagnosticMatchesFile(line, paths) {
-  const normalizedLine = line.replace(/\\/g, '/');
+  const location = /^(.+?)\(\d+,\d+\): /.exec(line);
+  if (!location) return false;
+  const file = location[1].replace(/\\/g, '/');
   for (const candidate of paths) {
-    if (normalizedLine.includes(candidate.replace(/\\/g, '/'))) return true;
+    if (file === candidate.replace(/\\/g, '/')) return true;
   }
   return false;
 }
diff --git a/scripts/lib/resolve-formatter.js b/scripts/lib/resolve-formatter.js
index 3fec591c9..251264e78 100644
--- a/scripts/lib/resolve-formatter.js
+++ b/scripts/lib/resolve-formatter.js
@@ -32,7 +32,16 @@ const PRETTIER_CONFIGS = [
   '.prettierrc.toml',
   'prettier.config.js',
   'prettier.config.cjs',
-  'prettier.config.mjs'
+  'prettier.config.mjs',
+  // The rest of the names Prettier's config searcher looks for
+  // (src/config/prettier-config/config-searcher.js).
+  '.prettierrc.json5',
+  '.prettierrc.ts',
+  '.prettierrc.mts',
+  '.prettierrc.cts',
+  'prettier.config.ts',
+  'prettier.config.mts',
+  'prettier.config.cts'
 ];
 
 const PROJECT_ROOT_MARKERS = ['package.json', ...BIOME_CONFIGS, ...PRETTIER_CONFIGS];
diff --git a/scripts/lib/utils.d.ts b/scripts/lib/utils.d.ts
index 9e980c699..df9bb8aad 100644
--- a/scripts/lib/utils.d.ts
+++ b/scripts/lib/utils.d.ts
@@ -193,10 +193,10 @@ export interface CommandResult {
 export function runCommand(cmd: string, options?: ExecSyncOptions): CommandResult;
 
 /** Check if the current directory is inside a git repository */
-export function isGitRepo(): boolean;
+export function isGitRepo(options?: ExecSyncOptions): boolean;
 
 /**
  * Get git modified files (staged + unstaged), optionally filtered by regex patterns.
  * Invalid regex patterns are silently skipped.
  */
-export function getGitModifiedFiles(patterns?: string[]): string[];
+export function getGitModifiedFiles(patterns?: string[], options?: ExecSyncOptions): string[];
diff --git a/scripts/lib/utils.js b/scripts/lib/utils.js
index 2e8550e5e..416c1c21f 100644
--- a/scripts/lib/utils.js
+++ b/scripts/lib/utils.js
@@ -537,22 +537,25 @@ function runCommand(cmd, options = {}) {
 }
 
 /**
- * Check if current directory is a git repository
+ * Check if current directory is a git repository.
+ * @param {object} [options] - Options forwarded to runCommand, including env.
  */
-function isGitRepo() {
-  return runCommand('git rev-parse --git-dir').success;
+function isGitRepo(options = {}) {
+  return runCommand('git rev-parse --git-dir', options).success;
 }
 
 /**
  * Get git modified files, optionally filtered by regex patterns
  * @param {string[]} patterns - Array of regex pattern strings to filter files.
  *   Invalid patterns are silently skipped.
+ * @param {object} [options] - Options forwarded to every Git subprocess.
  * @returns {string[]} Array of modified file paths
  */
-function getGitModifiedFiles(patterns = []) {
-  if (!isGitRepo()) return [];
+function getGitModifiedFiles(patterns = [], options = {}) {
+  if (!isGitRepo(options)) return [];
 
-  const result = runCommand('git diff --name-only HEAD');
+  // Paths from the repository root even when diff.relative is set.
+  const result = runCommand('git -c diff.relative=false diff --name-only HEAD', options);
   if (!result.success) return [];
 
   let files = result.output.split('\n').filter(Boolean);
diff --git a/tests/hooks/config-protection.test.js b/tests/hooks/config-protection.test.js
index b0b88ae54..9ab7d844f 100644
--- a/tests/hooks/config-protection.test.js
+++ b/tests/hooks/config-protection.test.js
@@ -447,6 +447,25 @@ function runTests() {
     })
   );
 
+  results.push(
+    test("blocks Prettier's TypeScript and JSON5 rc files", () => {
+      return withOwnedDirectory(fs.mkdtempSync(path.join(os.tmpdir(), 'ecc-config-protect-prettier-')), tmpDir => {
+        for (const name of ['.prettierrc.ts', '.prettierrc.mts', '.prettierrc.cts', '.prettierrc.json5', '.prettierrc.shared.ts']) {
+          const absPath = path.join(tmpDir, name);
+          fs.writeFileSync(absPath, 'export default {};\n');
+
+          const result = runHook({ tool_name: 'Edit', tool_input: { file_path: absPath } });
+
+          assert.strictEqual(result.code, 2, 'Expected ' + name + ' to be blocked');
+          assert.ok(
+            result.stderr.includes('BLOCKED: Modifying ' + name + ' is not allowed.'),
+            'Expected block message for ' + name + ', got: ' + result.stderr
+          );
+        }
+      });
+    })
+  );
+
   results.push(
     test('does not block build or test tooling configs', () => {
       // Pins the boundary: this hook guards LINTER configs. A future widening
diff --git a/tests/hooks/hooks.test.js b/tests/hooks/hooks.test.js
index 899b05a69..e31cdf449 100644
--- a/tests/hooks/hooks.test.js
+++ b/tests/hooks/hooks.test.js
@@ -233,6 +233,14 @@ function createTestDir() {
   return fs.mkdtempSync(path.join(os.tmpdir(), 'hooks-test-'));
 }
 
+function fixtureGitOptions(cwd) {
+  const env = { ...process.env };
+  for (const name of Object.keys(env)) {
+    if (name.toUpperCase().startsWith('GIT_')) delete env[name];
+  }
+  return { cwd, env };
+}
+
 // Clean up test directory
 function cleanupTestDir(testDir) {
   const retryableCodes = new Set(['EPERM', 'EBUSY', 'ENOTEMPTY']);
@@ -1201,6 +1209,74 @@ async function runTests() {
     passed++;
   else failed++;
 
+  if (
+    await asyncTest('finds console.log in a modified file when the session runs in a subdirectory', async () => {
+      // git reports paths from the repository root, not from the session's directory.
+      const repo = fs.mkdtempSync(path.join(os.tmpdir(), 'ecc-console-log-'));
+      try {
+        const appDir = path.join(repo, 'packages', 'app');
+        fs.mkdirSync(path.join(appDir, 'src'), { recursive: true });
+        execFileSync('git', ['init', '-q'], fixtureGitOptions(repo));
+        fs.writeFileSync(path.join(appDir, 'src', 'a.ts'), 'export const a = 1;\n');
+        execFileSync('git', ['add', '-A'], fixtureGitOptions(repo));
+        execFileSync('git', ['-c', 'user.email=t@t.local', '-c', 'user.name=t', '-c', 'commit.gpgsign=false', 'commit', '-q', '-m', 'seed'], fixtureGitOptions(repo));
+        fs.writeFileSync(path.join(appDir, 'src', 'a.ts'), 'export const a = 1;\nconsole.log(a);\n');
+
+        const result = await runScript(path.join(scriptsDir, 'check-console-log.js'), '{}', {}, appDir);
+        assert.strictEqual(result.code, 0);
+        assert.ok(result.stderr.includes('console.log found in packages/app/src/a.ts'), `Should warn about the file, got: ${result.stderr}`);
+
+        // diff.relative would make git report paths from the session's directory.
+        execFileSync('git', ['config', 'diff.relative', 'true'], fixtureGitOptions(repo));
+        const relative = await runScript(path.join(scriptsDir, 'check-console-log.js'), '{}', {}, appDir);
+        assert.ok(relative.stderr.includes('console.log found in packages/app/src/a.ts'), `Should warn with diff.relative, got: ${relative.stderr}`);
+      } finally {
+        fs.rmSync(repo, { recursive: true, force: true });
+      }
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    await asyncTest('uses the session repository despite inherited Git environment overrides', async () => {
+      const root = fs.mkdtempSync(path.join(os.tmpdir(), 'ecc-console-git-env-'));
+      try {
+        const makeRepo = (name, file) => {
+          const repo = path.join(root, name);
+          fs.mkdirSync(path.join(repo, 'src'), { recursive: true });
+          execFileSync('git', ['init', '-q'], fixtureGitOptions(repo));
+          fs.writeFileSync(path.join(repo, 'src', file), 'export const value = 1;\n');
+          execFileSync('git', ['add', '-A'], fixtureGitOptions(repo));
+          execFileSync('git', ['-c', 'user.email=t@t.local', '-c', 'user.name=t', '-c', 'commit.gpgsign=false', 'commit', '-q', '-m', 'seed'], fixtureGitOptions(repo));
+          return repo;
+        };
+        const sessionRepo = makeRepo('session', 'local.ts');
+        const foreignRepo = makeRepo('foreign', 'foreign.ts');
+        fs.writeFileSync(path.join(foreignRepo, 'src', 'foreign.ts'), 'console.log("foreign");\n');
+        const env = {
+          GIT_DIR: path.join(foreignRepo, '.git'),
+          GIT_WORK_TREE: foreignRepo,
+          GIT_INDEX_FILE: path.join(foreignRepo, '.git', 'index')
+        };
+
+        const clean = await runScript(path.join(scriptsDir, 'check-console-log.js'), '{}', env, sessionRepo);
+        assert.strictEqual(clean.code, 0);
+        assert.ok(!clean.stderr.includes('console.log found'), `foreign repository leaked into hook: ${clean.stderr}`);
+
+        fs.writeFileSync(path.join(sessionRepo, 'src', 'local.ts'), 'console.log("local");\n');
+        const local = await runScript(path.join(scriptsDir, 'check-console-log.js'), '{}', env, sessionRepo);
+        assert.strictEqual(local.code, 0);
+        assert.ok(local.stderr.includes('console.log found in src/local.ts'), local.stderr);
+        assert.ok(!local.stderr.includes('foreign.ts'), local.stderr);
+      } finally {
+        fs.rmSync(root, { recursive: true, force: true });
+      }
+    })
+  )
+    passed++;
+  else failed++;
+
   // session-end.js tests
   console.log('\nsession-end.js:');
 
diff --git a/tests/hooks/pre-bash-dev-server-block.test.js b/tests/hooks/pre-bash-dev-server-block.test.js
index 89524b1e0..a5d47c8e2 100644
--- a/tests/hooks/pre-bash-dev-server-block.test.js
+++ b/tests/hooks/pre-bash-dev-server-block.test.js
@@ -68,6 +68,25 @@ function runTests() {
       const result = runScript('npm run dev:ssr');
       assert.strictEqual(result.code, 2, `Expected exit code 2, got ${result.code}`);
     }) ? passed++ : failed++);
+
+    (test('still blocks tmux run-shell and tmux -c — no pane keeps the log (exit 2)', () => {
+      for (const command of [
+        'tmux run-shell "npm run dev"',
+        'tmux -L work run-shell "npm run dev"',
+        'tmux -c "npm run dev"',
+        "tmux -c'npm run dev'",
+        // In -vL the L takes `new-session` as its socket name, so run-shell is the command.
+        'tmux -vL new-session run-shell "npm run dev"',
+        // A pane command earlier in a sequence does not cover a later run-shell.
+        'tmux new-session -d \\; run-shell "npm run dev"',
+        'tmux -L work new-session -d \\; run-shell "npm run dev"',
+        // A `;` that ends an argument separates tmux commands too.
+        "tmux -L work new-session -d 'npm run dev;' run-shell 'npm run dev'"
+      ]) {
+        const result = runScript(command);
+        assert.strictEqual(result.code, 2, `Expected exit code 2 for ${command}, got ${result.code}`);
+      }
+    }) ? passed++ : failed++);
   } else {
     console.log('  (skipping blocking tests on Windows)\n');
   }
@@ -79,6 +98,34 @@ function runTests() {
     assert.strictEqual(result.code, 0, `Expected exit code 0, got ${result.code}`);
   }) ? passed++ : failed++);
 
+  (test('allows a tmux launch after tmux options, a path, an env prefix or a command alias (exit code 0)', () => {
+    for (const command of [
+      'tmux -L work new-session -d -s dev "npm run dev"',
+      'tmux -f ~/.tmux.dev.conf new-session -d "npm run dev"',
+      '/opt/homebrew/bin/tmux new-session -d -s dev "npm run dev"',
+      'env TERM=xterm-256color tmux new-session -d "npm run dev"',
+      'tmux neww "npm run dev"',
+      'tmux splitw -h "pnpm dev"'
+    ]) {
+      const result = runScript(command);
+      assert.strictEqual(result.code, 0, `Expected exit code 0 for ${command}, got ${result.code}`);
+    }
+  }) ? passed++ : failed++);
+
+  (test('allows npm run dev sent to or respawned in a tmux pane (exit code 0)', () => {
+    for (const command of [
+      'tmux send-keys -t dev "npm run dev" Enter',
+      'tmux respawn-pane -k -t dev "npm run dev"',
+      'tmux new-session -d -s dev \\; send-keys -t dev "npm run dev" Enter',
+      "tmux new-session -d 'echo start;' send-keys -t dev 'npm run dev' Enter",
+      // In double quotes bash keeps the backslash before ;, so tmux reads a literal ;
+      'tmux send-keys -t dev "echo ready\\;" "npm run dev" Enter'
+    ]) {
+      const result = runScript(command);
+      assert.strictEqual(result.code, 0, `Expected exit code 0 for ${command}, got ${result.code}`);
+    }
+  }) ? passed++ : failed++);
+
   (test('allows npm install (exit code 0)', () => {
     const result = runScript('npm install');
     assert.strictEqual(result.code, 0, `Expected exit code 0, got ${result.code}`);
diff --git a/tests/hooks/stop-format-typecheck.test.js b/tests/hooks/stop-format-typecheck.test.js
index 944c546a1..1e440254d 100644
--- a/tests/hooks/stop-format-typecheck.test.js
+++ b/tests/hooks/stop-format-typecheck.test.js
@@ -246,6 +246,57 @@ if (test('matches forward-slash TypeScript paths against Windows edited paths',
 
 })) passed++; else failed++;
 
+if (test('matches a diagnostic by the file it names, not by a substring of the line', () => {
+  const rootIndex = new Set(['/project/index.ts', 'index.ts']);
+  assert.strictEqual(diagnosticMatchesFile('index.ts(1,14): error TS2322: Type', rootIndex), true);
+  assert.strictEqual(diagnosticMatchesFile('src/index.ts(1,14): error TS2322: Type', rootIndex), false);
+  const utils = new Set(['/project/src/utils.ts', 'src/utils.ts']);
+  assert.strictEqual(diagnosticMatchesFile('web/src/utils.ts(2,1): error TS2304: Cannot find name', utils), false);
+  assert.strictEqual(diagnosticMatchesFile("app.ts(3,1): error TS2307: Cannot find module './src/utils.ts'", utils), false);
+  assert.strictEqual(diagnosticMatchesFile('src/(group)/page.tsx(3,5): error TS2322', new Set(['src/(group)/page.tsx'])), true);
+  assert.strictEqual(diagnosticMatchesFile("  Type 'string' is not assignable to type 'number'.", utils), false);
+})) passed++; else failed++;
+
+if (test('stop hook reports a tsc diagnostic only under the file it names', () => {
+  const { spawnSync } = require('child_process');
+  const projectDir = fs.mkdtempSync(path.join(accumulatorTempRoot, 'ts-project-'));
+  const binDir = path.join(projectDir, 'bin');
+  fs.mkdirSync(path.join(projectDir, 'src'));
+  fs.mkdirSync(binDir);
+  fs.writeFileSync(path.join(projectDir, 'tsconfig.json'), '{}');
+  fs.writeFileSync(path.join(projectDir, 'index.ts'), 'export const ok = 1;\n');
+  fs.writeFileSync(path.join(projectDir, 'src', 'index.ts'), 'export const bad: number = "x";\n');
+  const diagnostic = "src/index.ts(1,14): error TS2322: Type 'string' is not assignable to type 'number'.";
+  const fakeTsc = path.join(binDir, 'fake-tsc.js');
+  fs.writeFileSync(fakeTsc, `process.stdout.write(${JSON.stringify(`${diagnostic}\n`)});\nprocess.exitCode = 2;\n`);
+  if (process.platform === 'win32') {
+    fs.writeFileSync(path.join(binDir, 'npx.cmd'), `@echo off\r\nnode "${fakeTsc}" %*\r\n`);
+  } else {
+    fs.writeFileSync(path.join(binDir, 'npx'), `#!/usr/bin/env node\nrequire(${JSON.stringify(fakeTsc)});\n`);
+    fs.chmodSync(path.join(binDir, 'npx'), 0o755);
+  }
+  const pathKey = Object.keys(process.env).find(key => key.toLowerCase() === 'path') || 'PATH';
+  const stopScript = path.resolve(__dirname, '../../scripts/hooks/stop-format-typecheck.js');
+  const stopStderr = editedFile => {
+    fs.writeFileSync(getAccumFile(), `${editedFile}\n`);
+    return spawnSync('node', [stopScript], {
+      input: '{}',
+      env: { ...process.env, CLAUDE_SESSION_ID: TEST_SESSION_ID, [pathKey]: `${binDir}${path.delimiter}${process.env[pathKey]}` },
+      encoding: 'utf8',
+      timeout: 10000
+    }).stderr;
+  };
+  try {
+    const rootStderr = stopStderr(path.join(projectDir, 'index.ts'));
+    assert.ok(!rootStderr.includes('TypeScript errors'), `root index.ts must not get src/index.ts errors:\n${rootStderr}`);
+    const nestedStderr = stopStderr(path.join(projectDir, 'src', 'index.ts'));
+    assert.ok(nestedStderr.includes(`TypeScript errors in index.ts:\n${diagnostic}`), nestedStderr);
+  } finally {
+    cleanAccumFile();
+    fs.rmSync(projectDir, { recursive: true, force: true });
+  }
+})) passed++; else failed++;
+
 if (test('stop hook clears accumulator after processing duplicates', () => {
   cleanAccumFile();
   fs.writeFileSync(getAccumFile(), '/nonexistent/x.ts\n/nonexistent/x.ts\n/nonexistent/y.ts\n', 'utf8');
diff --git a/tests/lib/resolve-formatter.test.js b/tests/lib/resolve-formatter.test.js
index dc478fc84..42185725f 100644
--- a/tests/lib/resolve-formatter.test.js
+++ b/tests/lib/resolve-formatter.test.js
@@ -155,6 +155,21 @@ function runTests() {
     assert.strictEqual(detectFormatter(root), 'prettier');
   });
 
+  run("detectFormatter: detects Prettier's TypeScript and JSON5 config files", () => {
+    const names = ['.prettierrc.json5', '.prettierrc.ts', '.prettierrc.mts', '.prettierrc.cts',
+      'prettier.config.ts', 'prettier.config.mts', 'prettier.config.cts'];
+    for (const name of names) {
+      const root = makeTmpDir();
+      fs.writeFileSync(path.join(root, 'package.json'), JSON.stringify({ name: 'test' }));
+      fs.writeFileSync(path.join(root, name), 'export default {};\n');
+      assert.strictEqual(detectFormatter(root), 'prettier', name);
+      const nested = path.join(root, 'src');
+      fs.mkdirSync(nested);
+      fs.rmSync(path.join(root, 'package.json'));
+      assert.strictEqual(findProjectRoot(nested), root, `${name} marks the project root`);
+    }
+  });
+
   run('detectFormatter: detects prettier key in package.json', () => {
     const root = makeTmpDir();
     fs.writeFileSync(path.join(root, 'package.json'), JSON.stringify({ name: 'test', prettier: { singleQuote: true } }));