diff --git a/.changeset/devtools-bundler-core-stateful-regex.md b/.changeset/devtools-bundler-core-stateful-regex.md
new file mode 100644
index 000000000..5a77b249f
--- /dev/null
+++ b/.changeset/devtools-bundler-core-stateful-regex.md
@@ -0,0 +1,5 @@
+---
+'@tanstack/devtools-bundler-core': patch
+---
+
+Make `matcher` deterministic when `injectSource.ignore` regexes use the `g` (global) or `y` (sticky) flag. Such regexes are stateful under `.test()`, advancing `lastIndex` on each match; since the user's config regex object is reused across every module/component transform, ignored files and components alternated between being ignored and injected depending on processing order. The matcher now clones `g`/`y`-flagged regexes without those flags per call, so matching is stateless and the user's config object is never mutated.
diff --git a/packages/devtools-bundler-core/src/matcher.test.ts b/packages/devtools-bundler-core/src/matcher.test.ts
index eced3535e..e5724b608 100644
--- a/packages/devtools-bundler-core/src/matcher.test.ts
+++ b/packages/devtools-bundler-core/src/matcher.test.ts
@@ -30,4 +30,24 @@ describe('matcher', () => {
     expect(matcher(patterns, 'src/components/ignored-file.jsx')).toBe(true)
     expect(matcher(patterns, 'src/components/other.jsx')).toBe(false)
   })
+
+  it('is deterministic across repeated calls with a g-flagged regex', () => {
+    const pattern = /\.test\.tsx$/g
+    for (let i = 0; i < 5; i++) {
+      expect(matcher([pattern], 'src/Foo.test.tsx')).toBe(true)
+    }
+  })
+
+  it('is deterministic across repeated calls with a y-flagged regex', () => {
+    const pattern = /\.test\.tsx$/y
+    for (let i = 0; i < 5; i++) {
+      expect(matcher([pattern], 'src/Foo.test.tsx')).toBe(true)
+    }
+  })
+
+  it('does not mutate the user-supplied regex lastIndex', () => {
+    const pattern = /\.test\.tsx$/g
+    expect(matcher([pattern], 'src/Foo.test.tsx')).toBe(true)
+    expect(pattern.lastIndex).toBe(0)
+  })
 })
diff --git a/packages/devtools-bundler-core/src/matcher.ts b/packages/devtools-bundler-core/src/matcher.ts
index 0098d7635..402171736 100644
--- a/packages/devtools-bundler-core/src/matcher.ts
+++ b/packages/devtools-bundler-core/src/matcher.ts
@@ -11,7 +11,10 @@ export const matcher = (
     if (typeof pattern === 'string') {
       return picomatch(pattern)
     } else {
-      return (s: string) => pattern.test(s)
+      const re = /[gy]/.test(pattern.flags)
+        ? new RegExp(pattern.source, pattern.flags.replace(/[gy]/g, ''))
+        : pattern
+      return (s: string) => re.test(s)
     }
   })