Open transcript file links in explorer

EXPLORER.md

@@ -267,6 +267,18 @@ The speedometer went; the report is a "Copy render timings" row in
 already are. **Moving it is where the no-coordinate-taps rule got enforced**
 (Bryan, 2026-09-03) — see AGENTS.md's "Driving the UI".
 
+### 14. File links in a session open in the explorer
+
+A markdown destination that is an absolute path or a local `file:` URI opens that document in the
+session's explorer, on the session's setup. A trailing editor line and optional column are removed;
+the viewer opens the file but does not yet scroll to a line. Web links, relative links and `file:`
+URIs naming another host keep their ordinary external behaviour. The distinction is deliberately
+narrow: a relative link might be a web reference, and the phone must not silently reinterpret it as
+a path on another machine.
+
+The markdown link handler is provided around the session rather than taught about setups. That
+keeps the renderer reusable and makes the explorer's existing setup target the one navigation path.
+
 ## HTTP surface
 
 In `routes.rs`'s module doc with the rest. Bodies use `deny_unknown_fields`

app/androidApp/src/main/kotlin/com/example/aiapp/AppRoot.kt

@@ -11,6 +11,7 @@ import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Text
 import androidx.compose.material3.TextButton
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.CompositionLocalProvider
 import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.key
@@ -246,14 +247,19 @@ fun AppRoot(
                 // A Box so the explorer can be drawn *over* the session rather than instead of it.
                 // No imePadding here, for the reason above -- the explorer adds its own.
                 Box {
-                    SessionScreen(
-                        settings = current,
-                        summary = here.summary,
-                        onBack = goToMain,
-                        onFiles = { screen = here.copy(files = it) },
-                        share = share,
-                        onShareTaken = { share = null },
-                    )
+                    val fileLinkHandler = rememberFileLinkHandler { path ->
+                        screen = here.copy(files = here.summary.filesTarget(path))
+                    }
+                    CompositionLocalProvider(LocalFileLinkHandler provides fileLinkHandler) {
+                        SessionScreen(
+                            settings = current,
+                            summary = here.summary,
+                            onBack = goToMain,
+                            onFiles = { screen = here.copy(files = it) },
+                            share = share,
+                            onShareTaken = { share = null },
+                        )
+                    }
                     // Its own back handler is registered after this screen's, so it is the one the
                     // platform asks first, and it steps back inside itself before closing.
                     here.files?.let { target ->

app/androidApp/src/main/kotlin/com/example/aiapp/FilesScreen.kt

@@ -48,7 +48,22 @@ import kotlinx.coroutines.withContext
  * where it was working. That is what makes a second way in -- from the setups tab -- one more
  * caller rather than any new code here.
  */
-data class FilesTarget(val setup: String, val setupName: String, val start: String)
+data class FilesTarget(
+    val setup: String,
+    val setupName: String,
+    val start: String,
+    /** A document to open immediately; [start] remains the fallback directory. */
+    val file: String? = null,
+)
+
+/** The explorer target for this session's machine, optionally opened on [file]. */
+fun SessionSummary.filesTarget(file: String? = null) =
+    FilesTarget(
+        setup = setup,
+        setupName = setupName,
+        start = cwd?.takeIf { it.isNotBlank() } ?: "~",
+        file = file,
+    )
 
 /** Where the explorer is: in a directory, or in one file. */
 private sealed class Spot(val path: String) {
@@ -72,7 +87,14 @@ private sealed class Spot(val path: String) {
 @Composable
 fun FilesScreen(settings: ServerSettings, target: FilesTarget, onClose: () -> Unit) {
     val scope = rememberCoroutineScope()
-    var here by remember { mutableStateOf<Spot>(Spot.Dir(target.start)) }
+    val initialDirectory =
+        target.file?.let(::parentOf)?.let { Spot.Dir(it) } ?: Spot.Dir(target.start)
+    var here by
+        remember(target) {
+            mutableStateOf<Spot>(
+                target.file?.let { Spot.Doc(it, initialDirectory) } ?: initialDirectory
+            )
+        }
     val listings = remember { mutableStateMapOf<String, LoadState<Listing>>() }
     var creating by remember { mutableStateOf(false) }
     // Edit mode and whether anything has been typed live here rather than in the pane below,

app/androidApp/src/main/kotlin/com/example/aiapp/MarkdownLinks.kt

@@ -32,6 +32,7 @@ import com.mikepenz.markdown.model.markdownAnnotator
 import com.mikepenz.markdown.utils.getUnescapedTextInNode
 import com.mikepenz.markdown.utils.resolveImageAlt
 import com.mikepenz.markdown.utils.resolveImageLink
+import java.net.URI
 import org.intellij.markdown.MarkdownElementTypes
 import org.intellij.markdown.MarkdownTokenTypes
 import org.intellij.markdown.ast.ASTNode
@@ -89,6 +90,7 @@ fun LinkedText(content: String, node: ASTNode, style: TextStyle, modifier: Modif
             content.buildMarkdownAnnotatedString(node, style, settings)
         }
     val uriHandler = LocalUriHandler.current
+    val fileLinkHandler = LocalFileLinkHandler.current
     val onPlainTap = LocalMarkdownTap.current
     val layout = remember { Ref<TextLayoutResult>() }
     // The renderer's own rule for a style that names no colour: the theme's text colour.
@@ -127,7 +129,7 @@ fun LinkedText(content: String, node: ASTNode, style: TextStyle, modifier: Modif
                     when {
                         url != null -> {
                             up.consume()
-                            uriHandler.openUri(url)
+                            if (fileLinkHandler?.invoke(url) != true) uriHandler.openUri(url)
                         }
                         onPlainTap != null -> {
                             up.consume()
@@ -164,6 +166,55 @@ fun LinkedText(content: String, node: ASTNode, style: TextStyle, modifier: Modif
  */
 val LocalMarkdownTap = compositionLocalOf<(() -> Unit)?> { null }
 
+/**
+ * Opens a markdown destination inside the current session when it names a file on that session's
+ * machine. Null outside a session, where every link keeps its ordinary URI behaviour.
+ */
+val LocalFileLinkHandler = compositionLocalOf<((String) -> Boolean)?> { null }
+
+/**
+ * A stable markdown link handler whose behaviour follows the latest [onFile]. Keeping its identity
+ * stable matters: every visible markdown paragraph reads it, and a session recomposes on every
+ * streamed event.
+ */
+@Composable
+fun rememberFileLinkHandler(onFile: (String) -> Unit): (String) -> Boolean {
+    val latest = rememberUpdatedState(onFile)
+    return remember {
+        { destination ->
+            val path = filePathOf(destination)
+            if (path == null) false
+            else {
+                latest.value(path)
+                true
+            }
+        }
+    }
+}
+
+/**
+ * The path named by a local-file markdown destination.
+ *
+ * Only absolute paths and local `file:` URIs are claimed. A relative destination might be a web
+ * link, and sending one to a machine's filesystem would silently give an ordinary link a different
+ * meaning. Editors commonly append a line and optional column; the current viewer opens the file
+ * itself, so those coordinates are removed here.
+ */
+internal fun filePathOf(destination: String): String? {
+    val uri = runCatching { URI(destination) }.getOrNull()
+    val path =
+        when {
+            destination.startsWith("/") && !destination.startsWith("//") ->
+                uri?.path ?: destination.substringBefore('#').substringBefore('?')
+            uri != null &&
+                uri.scheme.equals("file", ignoreCase = true) &&
+                (uri.host.isNullOrEmpty() || uri.host == "localhost") -> uri.path
+            else -> null
+        }
+    if (path.isNullOrEmpty() || !path.startsWith('/')) return null
+    return path.replace(Regex(":\\d+(?::\\d+)?$"), "")
+}
+
 /**
  * [onTap] as a stable value to provide for [LocalMarkdownTap]. The identity stays put while the
  * behaviour follows the latest [onTap], which is what keeps providing it from invalidating the text

app/androidApp/src/main/kotlin/com/example/aiapp/SessionScreen.kt

@@ -1411,15 +1411,10 @@ fun SessionScreen(
                             "Files",
                             onClick = {
                                 onFiles(
-                                    FilesTarget(
-                                        setup = summary.setup,
-                                        setupName = summary.setupName,
-                                        // Where this session works, and the machine's own home when
-                                        // it was never given a directory -- resolved there rather
-                                        // than guessed at here, since this app does not know that
-                                        // home.
-                                        start = summary.cwd?.takeIf { it.isNotBlank() } ?: "~",
-                                    )
+                                    // Where this session works, and the machine's own home when it
+                                    // was never given a directory -- resolved there rather than
+                                    // guessed at here, since this app does not know that home.
+                                    summary.filesTarget()
                                 )
                             },
                         )

app/androidApp/src/test/kotlin/com/example/aiapp/MarkdownLinksTest.kt

@@ -0,0 +1,31 @@
+package com.example.aiapp
+
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertNull
+
+class MarkdownLinksTest {
+    @Test
+    fun `absolute file paths are opened on the session machine`() {
+        assertEquals(
+            "/home/bob/repos/ai app/Main.kt",
+            filePathOf("/home/bob/repos/ai%20app/Main.kt"),
+        )
+        assertEquals("/home/bob/Main.kt", filePathOf("file:///home/bob/Main.kt"))
+        assertEquals("/home/bob/Main.kt", filePathOf("file://localhost/home/bob/Main.kt"))
+    }
+
+    @Test
+    fun `editor coordinates select the file itself`() {
+        assertEquals("/home/bob/Main.kt", filePathOf("/home/bob/Main.kt:42"))
+        assertEquals("/home/bob/Main.kt", filePathOf("file:///home/bob/Main.kt:42:7#L42"))
+    }
+
+    @Test
+    fun `ordinary links keep their external meaning`() {
+        assertNull(filePathOf("https://example.com/source.kt"))
+        assertNull(filePathOf("docs/source.kt"))
+        assertNull(filePathOf("//example.com/source.kt"))
+        assertNull(filePathOf("file://example.com/source.kt"))
+    }
+}