diff --git a/composeApp/src/commonMain/kotlin/ai/rever/boss/search/GlobalSearchService.kt b/composeApp/src/commonMain/kotlin/ai/rever/boss/search/GlobalSearchService.kt
index 33b9936a0e..39ebdc4650 100644
--- a/composeApp/src/commonMain/kotlin/ai/rever/boss/search/GlobalSearchService.kt
+++ b/composeApp/src/commonMain/kotlin/ai/rever/boss/search/GlobalSearchService.kt
@@ -17,6 +17,7 @@ import kotlinx.coroutines.async
 import kotlinx.coroutines.awaitAll
 import kotlinx.coroutines.coroutineScope
 import kotlinx.coroutines.withContext
+import java.io.File
 
 private val logger = BossLogger.forComponent("GlobalSearchService")
 
@@ -239,6 +240,31 @@ object GlobalSearchService {
             }
         }
 
+    /**
+     * Index in [relativePath] where the file name starts, for either platform's separator.
+     *
+     * [IndexedFile.relativePath] is produced by relativizing two absolute paths, so on Windows it
+     * arrives joined with `\` and a bare `lastIndexOf('/')` returns -1. The match ranges below are
+     * then rebased against 0 instead of the file name's first character, which underlines the wrong
+     * characters - or, once a range lands past the name's length, underlines nothing at all.
+     *
+     * `/` is checked ALONGSIDE [File.separatorChar] rather than instead of it. On a POSIX host the
+     * two are the same character, so that host's behaviour is unchanged; on Windows `/` is not a
+     * legal file-name character, so it cannot split a name by accident. Deliberately not a bare
+     * `lastIndexOf('\\')` on every platform: a backslash IS a legal POSIX file-name character, and
+     * that would split `dir/we\ird.kt` inside its own name. [ContentSearchService] reaches for
+     * [File.separatorChar] in this package for the same reason.
+     *
+     * [separator] defaults to the host's and is only passed explicitly by tests. Because the rule
+     * is deliberately platform-dependent, a Windows-shaped path proves nothing when fed to a POSIX
+     * host - the shift there is correctly zero - so the parameter is what lets the Windows case be
+     * asserted on every runner rather than only on a Windows one.
+     */
+    internal fun fileNameStartIn(
+        relativePath: String,
+        separator: Char = File.separatorChar,
+    ): Int = maxOf(relativePath.lastIndexOf(separator), relativePath.lastIndexOf('/')) + 1
+
     /**
      * Search files using fuzzy matching.
      */
@@ -270,7 +296,7 @@ object GlobalSearchService {
 
             val pathMatch = FuzzyMatcher.match(query, file.relativePath, file.relativePath.lowercase())
             if (pathMatch != null && pathMatch.score >= MIN_SCORE) {
-                val fileNameStart = file.relativePath.lastIndexOf('/') + 1
+                val fileNameStart = fileNameStartIn(file.relativePath)
                 val adjustedRanges =
                     pathMatch.matchRanges
                         .filter { it.start >= fileNameStart || it.end > fileNameStart }
diff --git a/composeApp/src/desktopTest/kotlin/ai/rever/boss/search/GlobalSearchFileHighlightTest.kt b/composeApp/src/desktopTest/kotlin/ai/rever/boss/search/GlobalSearchFileHighlightTest.kt
new file mode 100644
index 0000000000..2739f9e17d
--- /dev/null
+++ b/composeApp/src/desktopTest/kotlin/ai/rever/boss/search/GlobalSearchFileHighlightTest.kt
@@ -0,0 +1,115 @@
+package ai.rever.boss.search
+
+import kotlinx.coroutines.runBlocking
+import java.io.File
+import kotlin.test.AfterTest
+import kotlin.test.BeforeTest
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+
+/**
+ * Pins where a path-only file hit draws its underline.
+ *
+ * [SearchResult.FileResult.matchRanges] index the file NAME, while the match that produced them was
+ * found in the whole relative path, so the ranges have to be shifted back past the leading
+ * directories. That shift used to look for `/` only. [IndexedFile.relativePath] is built by
+ * relativizing two absolute paths, so on Windows it is joined with `\` and the search found no
+ * separator at all - the ranges were then shifted by nothing and underlined whatever characters
+ * happened to sit at those offsets in the name.
+ *
+ * The rule is deliberately platform-dependent, so the Windows case cannot be proven by feeding a
+ * backslash path to a POSIX host - the shift there is correctly zero. The separator is injected
+ * instead, which is what makes the two shift tests below assert the same thing on every runner.
+ * The end-to-end test uses the HOST's separator, and so is a red test only on Windows; it is a
+ * regression guard elsewhere, and is written that way on purpose rather than by accident.
+ */
+class GlobalSearchFileHighlightTest {
+    @BeforeTest
+    fun setUp() {
+        SearchSources.clearForTests()
+    }
+
+    @AfterTest
+    fun tearDown() {
+        SearchSources.clearForTests()
+    }
+
+    private companion object {
+        /** Built from its code point so the separator survives any tooling that rewrites escapes. */
+        val BACKSLASH: Char = Char(92)
+
+        /** `uiButton` is a subsequence of `app<sep>ui<sep>Button.kt` but NOT of `Button.kt`. */
+        const val QUERY = "uiButton"
+
+        const val NAME = "Button.kt"
+    }
+
+    // ---- the shift itself, asserted identically on every OS ----
+
+    @Test
+    fun `a windows path shifts past its last backslash`() {
+        val relative = "app${BACKSLASH}ui${BACKSLASH}Button.kt"
+
+        assertEquals(7, GlobalSearchService.fileNameStartIn(relative, separator = BACKSLASH))
+    }
+
+    @Test
+    fun `a posix path shifts past its last slash on any host`() {
+        assertEquals(7, GlobalSearchService.fileNameStartIn("app/ui/Button.kt", separator = '/'))
+    }
+
+    @Test
+    fun `a bare file name shifts by nothing`() {
+        assertEquals(0, GlobalSearchService.fileNameStartIn(NAME, separator = BACKSLASH))
+        assertEquals(0, GlobalSearchService.fileNameStartIn(NAME, separator = '/'))
+    }
+
+    @Test
+    fun `a backslash inside a posix file name is not mistaken for a separator`() {
+        // A backslash is a legal POSIX file-name character. With '/' as the separator the name
+        // starts after the slash, not after the backslash inside it.
+        val relative = "dir/we${BACKSLASH}ird.kt"
+
+        assertEquals(4, GlobalSearchService.fileNameStartIn(relative, separator = '/'))
+    }
+
+    // ---- what the dialog actually draws, through the real search ----
+
+    /**
+     * Red on Windows, where the separator is `\`. On a POSIX host the shift already worked, so this
+     * guards against a regression rather than proving the fix.
+     */
+    @Test
+    fun `a path hit underlines the file name, not an offset slice of it`() {
+        val sep = File.separatorChar
+        val file =
+            IndexedFile(
+                name = NAME,
+                path = "${File.separator}proj${sep}app${sep}ui$sep$NAME",
+                relativePath = "app${sep}ui$sep$NAME",
+            )
+
+        val result =
+            runBlocking {
+                GlobalSearchService
+                    .search(rawQuery = QUERY, windowId = null, indexedFiles = listOf(file))
+                    .filterIsInstance<SearchResult.FileResult>()
+                    .single()
+            }
+
+        val underlined = result.matchRanges.map { result.name.substring(it.start, it.end) }
+
+        // Before the fix, on Windows, this was ["on", "kt"]: the ranges for `ui` and `Button` in the
+        // full path were rebased against 0, landing on "Butt(on)" and "Button.(kt)".
+        assertEquals(listOf("Button"), underlined, "underlined text")
+        assertEquals(listOf(MatchRange(0, 6)), result.matchRanges, "ranges into the file name")
+
+        val wanted = QUERY.lowercase().toSet()
+        for (text in underlined) {
+            for (ch in text.lowercase()) {
+                assertTrue(ch in wanted, "underlined '$ch' from \"$text\", which is not in \"$QUERY\"")
+            }
+        }
+    }
+}