diff --git a/compose/api/compose.klib.api b/compose/api/compose.klib.api
index 3fe5178..0c24bc3 100644
--- a/compose/api/compose.klib.api
+++ b/compose/api/compose.klib.api
@@ -72,9 +72,8 @@ abstract interface wang.harlon.tinyui/Navigator { // wang.harlon.tinyui/Navigato
 }
 
 abstract interface wang.harlon.tinyui/PageSink { // wang.harlon.tinyui/PageSink|null[0]
-    abstract fun businessError(kotlin/String, kotlin/String, kotlin/String?) // wang.harlon.tinyui/PageSink.businessError|businessError(kotlin.String;kotlin.String;kotlin.String?){}[0]
+    abstract fun error(wang.harlon.tinyui/PageError) // wang.harlon.tinyui/PageSink.error|error(wang.harlon.tinyui.PageError){}[0]
     abstract fun log(kotlin/String) // wang.harlon.tinyui/PageSink.log|log(kotlin.String){}[0]
-    abstract fun patchProblem(wang.harlon.tinyui.node/PatchProblem) // wang.harlon.tinyui/PageSink.patchProblem|patchProblem(wang.harlon.tinyui.node.PatchProblem){}[0]
 }
 
 abstract interface wang.harlon.tinyui/Store { // wang.harlon.tinyui/Store|null[0]
@@ -191,6 +190,23 @@ final class wang.harlon.tinyui.schema/ComponentSchema { // wang.harlon.tinyui.sc
     final fun prop(kotlin/String): wang.harlon.tinyui.schema/PropSpec? // wang.harlon.tinyui.schema/ComponentSchema.prop|prop(kotlin.String){}[0]
 }
 
+final class wang.harlon.tinyui/BuildManifest { // wang.harlon.tinyui/BuildManifest|null[0]
+    constructor <init>(kotlin.collections/List<kotlin/String>, kotlin.collections/List<kotlin/String>, kotlin.collections/Map<kotlin/String, kotlin/String>) // wang.harlon.tinyui/BuildManifest.<init>|<init>(kotlin.collections.List<kotlin.String>;kotlin.collections.List<kotlin.String>;kotlin.collections.Map<kotlin.String,kotlin.String>){}[0]
+
+    final val buildIds // wang.harlon.tinyui/BuildManifest.buildIds|{}buildIds[0]
+        final fun <get-buildIds>(): kotlin.collections/Map<kotlin/String, kotlin/String> // wang.harlon.tinyui/BuildManifest.buildIds.<get-buildIds>|<get-buildIds>(){}[0]
+    final val pages // wang.harlon.tinyui/BuildManifest.pages|{}pages[0]
+        final fun <get-pages>(): kotlin.collections/List<kotlin/String> // wang.harlon.tinyui/BuildManifest.pages.<get-pages>|<get-pages>(){}[0]
+    final val runtime // wang.harlon.tinyui/BuildManifest.runtime|{}runtime[0]
+        final fun <get-runtime>(): kotlin.collections/List<kotlin/String> // wang.harlon.tinyui/BuildManifest.runtime.<get-runtime>|<get-runtime>(){}[0]
+
+    final fun buildId(kotlin/String): kotlin/String // wang.harlon.tinyui/BuildManifest.buildId|buildId(kotlin.String){}[0]
+
+    final object Companion { // wang.harlon.tinyui/BuildManifest.Companion|null[0]
+        final fun parse(kotlin/String): wang.harlon.tinyui/BuildManifest // wang.harlon.tinyui/BuildManifest.Companion.parse|parse(kotlin.String){}[0]
+    }
+}
+
 final class wang.harlon.tinyui/EventBus { // wang.harlon.tinyui/EventBus|null[0]
     constructor <init>() // wang.harlon.tinyui/EventBus.<init>|<init>(){}[0]
 
@@ -261,9 +277,34 @@ final class wang.harlon.tinyui/InMemoryStore : wang.harlon.tinyui/Store { // wan
     final fun set(kotlin/String, kotlin/String) // wang.harlon.tinyui/InMemoryStore.set|set(kotlin.String;kotlin.String){}[0]
 }
 
+final class wang.harlon.tinyui/PageError { // wang.harlon.tinyui/PageError|null[0]
+    constructor <init>(kotlin/String, kotlin/String, kotlin/String, kotlin/String, kotlin/String? = ..., kotlin/String? = ..., kotlin.collections/List<wang.harlon.tinyui/StackFrame> = ..., kotlin/String? = ...) // wang.harlon.tinyui/PageError.<init>|<init>(kotlin.String;kotlin.String;kotlin.String;kotlin.String;kotlin.String?;kotlin.String?;kotlin.collections.List<wang.harlon.tinyui.StackFrame>;kotlin.String?){}[0]
+
+    final val buildId // wang.harlon.tinyui/PageError.buildId|{}buildId[0]
+        final fun <get-buildId>(): kotlin/String // wang.harlon.tinyui/PageError.buildId.<get-buildId>|<get-buildId>(){}[0]
+    final val entry // wang.harlon.tinyui/PageError.entry|{}entry[0]
+        final fun <get-entry>(): kotlin/String? // wang.harlon.tinyui/PageError.entry.<get-entry>|<get-entry>(){}[0]
+    final val frames // wang.harlon.tinyui/PageError.frames|{}frames[0]
+        final fun <get-frames>(): kotlin.collections/List<wang.harlon.tinyui/StackFrame> // wang.harlon.tinyui/PageError.frames.<get-frames>|<get-frames>(){}[0]
+    final val jsStack // wang.harlon.tinyui/PageError.jsStack|{}jsStack[0]
+        final fun <get-jsStack>(): kotlin/String? // wang.harlon.tinyui/PageError.jsStack.<get-jsStack>|<get-jsStack>(){}[0]
+    final val kind // wang.harlon.tinyui/PageError.kind|{}kind[0]
+        final fun <get-kind>(): kotlin/String // wang.harlon.tinyui/PageError.kind.<get-kind>|<get-kind>(){}[0]
+    final val message // wang.harlon.tinyui/PageError.message|{}message[0]
+        final fun <get-message>(): kotlin/String // wang.harlon.tinyui/PageError.message.<get-message>|<get-message>(){}[0]
+    final val op // wang.harlon.tinyui/PageError.op|{}op[0]
+        final fun <get-op>(): kotlin/String? // wang.harlon.tinyui/PageError.op.<get-op>|<get-op>(){}[0]
+    final val page // wang.harlon.tinyui/PageError.page|{}page[0]
+        final fun <get-page>(): kotlin/String // wang.harlon.tinyui/PageError.page.<get-page>|<get-page>(){}[0]
+
+    final fun toString(): kotlin/String // wang.harlon.tinyui/PageError.toString|toString(){}[0]
+}
+
 final class wang.harlon.tinyui/PageFailure { // wang.harlon.tinyui/PageFailure|null[0]
-    constructor <init>(kotlin/String, kotlin/String) // wang.harlon.tinyui/PageFailure.<init>|<init>(kotlin.String;kotlin.String){}[0]
+    constructor <init>(wang.harlon.tinyui/PageError) // wang.harlon.tinyui/PageFailure.<init>|<init>(wang.harlon.tinyui.PageError){}[0]
 
+    final val error // wang.harlon.tinyui/PageFailure.error|{}error[0]
+        final fun <get-error>(): wang.harlon.tinyui/PageError // wang.harlon.tinyui/PageFailure.error.<get-error>|<get-error>(){}[0]
     final val kind // wang.harlon.tinyui/PageFailure.kind|{}kind[0]
         final fun <get-kind>(): kotlin/String // wang.harlon.tinyui/PageFailure.kind.<get-kind>|<get-kind>(){}[0]
     final val message // wang.harlon.tinyui/PageFailure.message|{}message[0]
@@ -271,7 +312,7 @@ final class wang.harlon.tinyui/PageFailure { // wang.harlon.tinyui/PageFailure|n
 }
 
 final class wang.harlon.tinyui/PageHost { // wang.harlon.tinyui/PageHost|null[0]
-    constructor <init>(wang.harlon.tinyui/RuntimeBundle, kotlin/ByteArray, wang.harlon.tinyui.schema/ComponentRegistry, wang.harlon.tinyui/PageSink, wang.harlon.tinyui/HostServices = ..., kotlin/String = ..., kotlin/Long = ...) // wang.harlon.tinyui/PageHost.<init>|<init>(wang.harlon.tinyui.RuntimeBundle;kotlin.ByteArray;wang.harlon.tinyui.schema.ComponentRegistry;wang.harlon.tinyui.PageSink;wang.harlon.tinyui.HostServices;kotlin.String;kotlin.Long){}[0]
+    constructor <init>(wang.harlon.tinyui/RuntimeBundle, wang.harlon.tinyui/PageModule, wang.harlon.tinyui.schema/ComponentRegistry, wang.harlon.tinyui/PageSink, wang.harlon.tinyui/HostServices = ..., kotlin/String = ..., kotlin/Long = ..., wang.harlon.tinyui/SourceMaps = ...) // wang.harlon.tinyui/PageHost.<init>|<init>(wang.harlon.tinyui.RuntimeBundle;wang.harlon.tinyui.PageModule;wang.harlon.tinyui.schema.ComponentRegistry;wang.harlon.tinyui.PageSink;wang.harlon.tinyui.HostServices;kotlin.String;kotlin.Long;wang.harlon.tinyui.SourceMaps){}[0]
 
     final val registry // wang.harlon.tinyui/PageHost.registry|{}registry[0]
         final fun <get-registry>(): wang.harlon.tinyui.schema/ComponentRegistry // wang.harlon.tinyui/PageHost.registry.<get-registry>|<get-registry>(){}[0]
@@ -297,6 +338,17 @@ final class wang.harlon.tinyui/PageHost { // wang.harlon.tinyui/PageHost|null[0]
     }
 }
 
+final class wang.harlon.tinyui/PageModule { // wang.harlon.tinyui/PageModule|null[0]
+    constructor <init>(kotlin/String, kotlin/ByteArray, kotlin/String = ...) // wang.harlon.tinyui/PageModule.<init>|<init>(kotlin.String;kotlin.ByteArray;kotlin.String){}[0]
+
+    final val buildId // wang.harlon.tinyui/PageModule.buildId|{}buildId[0]
+        final fun <get-buildId>(): kotlin/String // wang.harlon.tinyui/PageModule.buildId.<get-buildId>|<get-buildId>(){}[0]
+    final val bytecode // wang.harlon.tinyui/PageModule.bytecode|{}bytecode[0]
+        final fun <get-bytecode>(): kotlin/ByteArray // wang.harlon.tinyui/PageModule.bytecode.<get-bytecode>|<get-bytecode>(){}[0]
+    final val name // wang.harlon.tinyui/PageModule.name|{}name[0]
+        final fun <get-name>(): kotlin/String // wang.harlon.tinyui/PageModule.name.<get-name>|<get-name>(){}[0]
+}
+
 final class wang.harlon.tinyui/RuntimeBundle { // wang.harlon.tinyui/RuntimeBundle|null[0]
     constructor <init>(kotlin/ByteArray, kotlin/ByteArray) // wang.harlon.tinyui/RuntimeBundle.<init>|<init>(kotlin.ByteArray;kotlin.ByteArray){}[0]
 
@@ -306,6 +358,34 @@ final class wang.harlon.tinyui/RuntimeBundle { // wang.harlon.tinyui/RuntimeBund
         final fun <get-native>(): kotlin/ByteArray // wang.harlon.tinyui/RuntimeBundle.native.<get-native>|<get-native>(){}[0]
 }
 
+final class wang.harlon.tinyui/SourceMaps { // wang.harlon.tinyui/SourceMaps|null[0]
+    constructor <init>(kotlin.collections/Map<kotlin/String, kotlin/String>) // wang.harlon.tinyui/SourceMaps.<init>|<init>(kotlin.collections.Map<kotlin.String,kotlin.String>){}[0]
+
+    final fun frames(kotlin/String?): kotlin.collections/List<wang.harlon.tinyui/StackFrame> // wang.harlon.tinyui/SourceMaps.frames|frames(kotlin.String?){}[0]
+
+    final object Companion { // wang.harlon.tinyui/SourceMaps.Companion|null[0]
+        final val EMPTY // wang.harlon.tinyui/SourceMaps.Companion.EMPTY|{}EMPTY[0]
+            final fun <get-EMPTY>(): wang.harlon.tinyui/SourceMaps // wang.harlon.tinyui/SourceMaps.Companion.EMPTY.<get-EMPTY>|<get-EMPTY>(){}[0]
+    }
+}
+
+final class wang.harlon.tinyui/StackFrame { // wang.harlon.tinyui/StackFrame|null[0]
+    constructor <init>(kotlin/String, kotlin/String, kotlin/Int, kotlin/Int?, kotlin/Boolean) // wang.harlon.tinyui/StackFrame.<init>|<init>(kotlin.String;kotlin.String;kotlin.Int;kotlin.Int?;kotlin.Boolean){}[0]
+
+    final val column // wang.harlon.tinyui/StackFrame.column|{}column[0]
+        final fun <get-column>(): kotlin/Int? // wang.harlon.tinyui/StackFrame.column.<get-column>|<get-column>(){}[0]
+    final val file // wang.harlon.tinyui/StackFrame.file|{}file[0]
+        final fun <get-file>(): kotlin/String // wang.harlon.tinyui/StackFrame.file.<get-file>|<get-file>(){}[0]
+    final val function // wang.harlon.tinyui/StackFrame.function|{}function[0]
+        final fun <get-function>(): kotlin/String // wang.harlon.tinyui/StackFrame.function.<get-function>|<get-function>(){}[0]
+    final val line // wang.harlon.tinyui/StackFrame.line|{}line[0]
+        final fun <get-line>(): kotlin/Int // wang.harlon.tinyui/StackFrame.line.<get-line>|<get-line>(){}[0]
+    final val mapped // wang.harlon.tinyui/StackFrame.mapped|{}mapped[0]
+        final fun <get-mapped>(): kotlin/Boolean // wang.harlon.tinyui/StackFrame.mapped.<get-mapped>|<get-mapped>(){}[0]
+
+    final fun toString(): kotlin/String // wang.harlon.tinyui/StackFrame.toString|toString(){}[0]
+}
+
 final class wang.harlon.tinyui/StoreValue { // wang.harlon.tinyui/StoreValue|null[0]
     constructor <init>(kotlin/String, kotlin/Long) // wang.harlon.tinyui/StoreValue.<init>|<init>(kotlin.String;kotlin.Long){}[0]
 
@@ -431,6 +511,10 @@ final object wang.harlon.tinyui.schema/LayoutProps { // wang.harlon.tinyui.schem
 final object wang.harlon.tinyui/TinyUI { // wang.harlon.tinyui/TinyUI|null[0]
     final val engineVersion // wang.harlon.tinyui/TinyUI.engineVersion|{}engineVersion[0]
         final fun <get-engineVersion>(): kotlin/String // wang.harlon.tinyui/TinyUI.engineVersion.<get-engineVersion>|<get-engineVersion>(){}[0]
+
+    final var debug // wang.harlon.tinyui/TinyUI.debug|{}debug[0]
+        final fun <get-debug>(): kotlin/Boolean // wang.harlon.tinyui/TinyUI.debug.<get-debug>|<get-debug>(){}[0]
+        final fun <set-debug>(kotlin/Boolean) // wang.harlon.tinyui/TinyUI.debug.<set-debug>|<set-debug>(kotlin.Boolean){}[0]
 }
 
 final const val wang.harlon.tinyui.node/ROOT_ID // wang.harlon.tinyui.node/ROOT_ID|{}ROOT_ID[0]
@@ -456,6 +540,7 @@ final val wang.harlon.tinyui.schema/wang_harlon_tinyui_schema_PropSpec_Str$stabl
 final val wang.harlon.tinyui.schema/wang_harlon_tinyui_schema_SizeValue_Fill$stableprop // wang.harlon.tinyui.schema/wang_harlon_tinyui_schema_SizeValue_Fill$stableprop|#static{}wang_harlon_tinyui_schema_SizeValue_Fill$stableprop[0]
 final val wang.harlon.tinyui.schema/wang_harlon_tinyui_schema_SizeValue_Fixed$stableprop // wang.harlon.tinyui.schema/wang_harlon_tinyui_schema_SizeValue_Fixed$stableprop|#static{}wang_harlon_tinyui_schema_SizeValue_Fixed$stableprop[0]
 final val wang.harlon.tinyui.schema/wang_harlon_tinyui_schema_SizeValue_Wrap$stableprop // wang.harlon.tinyui.schema/wang_harlon_tinyui_schema_SizeValue_Wrap$stableprop|#static{}wang_harlon_tinyui_schema_SizeValue_Wrap$stableprop[0]
+final val wang.harlon.tinyui/wang_harlon_tinyui_BuildManifest$stableprop // wang.harlon.tinyui/wang_harlon_tinyui_BuildManifest$stableprop|#static{}wang_harlon_tinyui_BuildManifest$stableprop[0]
 final val wang.harlon.tinyui/wang_harlon_tinyui_EventBus$stableprop // wang.harlon.tinyui/wang_harlon_tinyui_EventBus$stableprop|#static{}wang_harlon_tinyui_EventBus$stableprop[0]
 final val wang.harlon.tinyui/wang_harlon_tinyui_HostException$stableprop // wang.harlon.tinyui/wang_harlon_tinyui_HostException$stableprop|#static{}wang_harlon_tinyui_HostException$stableprop[0]
 final val wang.harlon.tinyui/wang_harlon_tinyui_HostServices$stableprop // wang.harlon.tinyui/wang_harlon_tinyui_HostServices$stableprop|#static{}wang_harlon_tinyui_HostServices$stableprop[0]
@@ -464,9 +549,14 @@ final val wang.harlon.tinyui/wang_harlon_tinyui_HttpRequest$stableprop // wang.h
 final val wang.harlon.tinyui/wang_harlon_tinyui_HttpResponse$stableprop // wang.harlon.tinyui/wang_harlon_tinyui_HttpResponse$stableprop|#static{}wang_harlon_tinyui_HttpResponse$stableprop[0]
 final val wang.harlon.tinyui/wang_harlon_tinyui_InMemoryStore$stableprop // wang.harlon.tinyui/wang_harlon_tinyui_InMemoryStore$stableprop|#static{}wang_harlon_tinyui_InMemoryStore$stableprop[0]
 final val wang.harlon.tinyui/wang_harlon_tinyui_Navigator_None$stableprop // wang.harlon.tinyui/wang_harlon_tinyui_Navigator_None$stableprop|#static{}wang_harlon_tinyui_Navigator_None$stableprop[0]
+final val wang.harlon.tinyui/wang_harlon_tinyui_PageError$stableprop // wang.harlon.tinyui/wang_harlon_tinyui_PageError$stableprop|#static{}wang_harlon_tinyui_PageError$stableprop[0]
 final val wang.harlon.tinyui/wang_harlon_tinyui_PageFailure$stableprop // wang.harlon.tinyui/wang_harlon_tinyui_PageFailure$stableprop|#static{}wang_harlon_tinyui_PageFailure$stableprop[0]
 final val wang.harlon.tinyui/wang_harlon_tinyui_PageHost$stableprop // wang.harlon.tinyui/wang_harlon_tinyui_PageHost$stableprop|#static{}wang_harlon_tinyui_PageHost$stableprop[0]
+final val wang.harlon.tinyui/wang_harlon_tinyui_PageModule$stableprop // wang.harlon.tinyui/wang_harlon_tinyui_PageModule$stableprop|#static{}wang_harlon_tinyui_PageModule$stableprop[0]
 final val wang.harlon.tinyui/wang_harlon_tinyui_RuntimeBundle$stableprop // wang.harlon.tinyui/wang_harlon_tinyui_RuntimeBundle$stableprop|#static{}wang_harlon_tinyui_RuntimeBundle$stableprop[0]
+final val wang.harlon.tinyui/wang_harlon_tinyui_SourceMap_Position$stableprop // wang.harlon.tinyui/wang_harlon_tinyui_SourceMap_Position$stableprop|#static{}wang_harlon_tinyui_SourceMap_Position$stableprop[0]
+final val wang.harlon.tinyui/wang_harlon_tinyui_SourceMaps$stableprop // wang.harlon.tinyui/wang_harlon_tinyui_SourceMaps$stableprop|#static{}wang_harlon_tinyui_SourceMaps$stableprop[0]
+final val wang.harlon.tinyui/wang_harlon_tinyui_StackFrame$stableprop // wang.harlon.tinyui/wang_harlon_tinyui_StackFrame$stableprop|#static{}wang_harlon_tinyui_StackFrame$stableprop[0]
 final val wang.harlon.tinyui/wang_harlon_tinyui_StoreValue$stableprop // wang.harlon.tinyui/wang_harlon_tinyui_StoreValue$stableprop|#static{}wang_harlon_tinyui_StoreValue$stableprop[0]
 final val wang.harlon.tinyui/wang_harlon_tinyui_TinyUI$stableprop // wang.harlon.tinyui/wang_harlon_tinyui_TinyUI$stableprop|#static{}wang_harlon_tinyui_TinyUI$stableprop[0]
 
@@ -492,7 +582,9 @@ final fun wang.harlon.tinyui.schema/wang_harlon_tinyui_schema_PropSpec_Str$stabl
 final fun wang.harlon.tinyui.schema/wang_harlon_tinyui_schema_SizeValue_Fill$stableprop_getter(): kotlin/Int // wang.harlon.tinyui.schema/wang_harlon_tinyui_schema_SizeValue_Fill$stableprop_getter|wang_harlon_tinyui_schema_SizeValue_Fill$stableprop_getter(){}[0]
 final fun wang.harlon.tinyui.schema/wang_harlon_tinyui_schema_SizeValue_Fixed$stableprop_getter(): kotlin/Int // wang.harlon.tinyui.schema/wang_harlon_tinyui_schema_SizeValue_Fixed$stableprop_getter|wang_harlon_tinyui_schema_SizeValue_Fixed$stableprop_getter(){}[0]
 final fun wang.harlon.tinyui.schema/wang_harlon_tinyui_schema_SizeValue_Wrap$stableprop_getter(): kotlin/Int // wang.harlon.tinyui.schema/wang_harlon_tinyui_schema_SizeValue_Wrap$stableprop_getter|wang_harlon_tinyui_schema_SizeValue_Wrap$stableprop_getter(){}[0]
-final fun wang.harlon.tinyui/TinyUIPage(wang.harlon.tinyui/RuntimeBundle, kotlin/ByteArray, wang.harlon.tinyui.schema/ComponentRegistry, wang.harlon.tinyui/PageSink, wang.harlon.tinyui/HostServices?, kotlin/String?, androidx.compose.ui/Modifier?, kotlin/Function3<wang.harlon.tinyui/PageFailure, androidx.compose.runtime/Composer, kotlin/Int, kotlin/Unit>?, kotlin/Function1<wang.harlon.tinyui/PageHost, kotlin/Unit>?, androidx.compose.runtime/Composer?, kotlin/Int, kotlin/Int) // wang.harlon.tinyui/TinyUIPage|TinyUIPage(wang.harlon.tinyui.RuntimeBundle;kotlin.ByteArray;wang.harlon.tinyui.schema.ComponentRegistry;wang.harlon.tinyui.PageSink;wang.harlon.tinyui.HostServices?;kotlin.String?;androidx.compose.ui.Modifier?;kotlin.Function3<wang.harlon.tinyui.PageFailure,androidx.compose.runtime.Composer,kotlin.Int,kotlin.Unit>?;kotlin.Function1<wang.harlon.tinyui.PageHost,kotlin.Unit>?;androidx.compose.runtime.Composer?;kotlin.Int;kotlin.Int){}[0]
+final fun wang.harlon.tinyui/PageFailureScreen(wang.harlon.tinyui/PageFailure, androidx.compose.runtime/Composer?, kotlin/Int) // wang.harlon.tinyui/PageFailureScreen|PageFailureScreen(wang.harlon.tinyui.PageFailure;androidx.compose.runtime.Composer?;kotlin.Int){}[0]
+final fun wang.harlon.tinyui/TinyUIPage(wang.harlon.tinyui/RuntimeBundle, wang.harlon.tinyui/PageModule, wang.harlon.tinyui.schema/ComponentRegistry, wang.harlon.tinyui/PageSink, wang.harlon.tinyui/HostServices?, kotlin/String?, androidx.compose.ui/Modifier?, wang.harlon.tinyui/SourceMaps?, kotlin/Function3<wang.harlon.tinyui/PageFailure, androidx.compose.runtime/Composer, kotlin/Int, kotlin/Unit>?, kotlin/Function1<wang.harlon.tinyui/PageHost, kotlin/Unit>?, androidx.compose.runtime/Composer?, kotlin/Int, kotlin/Int) // wang.harlon.tinyui/TinyUIPage|TinyUIPage(wang.harlon.tinyui.RuntimeBundle;wang.harlon.tinyui.PageModule;wang.harlon.tinyui.schema.ComponentRegistry;wang.harlon.tinyui.PageSink;wang.harlon.tinyui.HostServices?;kotlin.String?;androidx.compose.ui.Modifier?;wang.harlon.tinyui.SourceMaps?;kotlin.Function3<wang.harlon.tinyui.PageFailure,androidx.compose.runtime.Composer,kotlin.Int,kotlin.Unit>?;kotlin.Function1<wang.harlon.tinyui.PageHost,kotlin.Unit>?;androidx.compose.runtime.Composer?;kotlin.Int;kotlin.Int){}[0]
+final fun wang.harlon.tinyui/wang_harlon_tinyui_BuildManifest$stableprop_getter(): kotlin/Int // wang.harlon.tinyui/wang_harlon_tinyui_BuildManifest$stableprop_getter|wang_harlon_tinyui_BuildManifest$stableprop_getter(){}[0]
 final fun wang.harlon.tinyui/wang_harlon_tinyui_EventBus$stableprop_getter(): kotlin/Int // wang.harlon.tinyui/wang_harlon_tinyui_EventBus$stableprop_getter|wang_harlon_tinyui_EventBus$stableprop_getter(){}[0]
 final fun wang.harlon.tinyui/wang_harlon_tinyui_HostException$stableprop_getter(): kotlin/Int // wang.harlon.tinyui/wang_harlon_tinyui_HostException$stableprop_getter|wang_harlon_tinyui_HostException$stableprop_getter(){}[0]
 final fun wang.harlon.tinyui/wang_harlon_tinyui_HostServices$stableprop_getter(): kotlin/Int // wang.harlon.tinyui/wang_harlon_tinyui_HostServices$stableprop_getter|wang_harlon_tinyui_HostServices$stableprop_getter(){}[0]
@@ -501,8 +593,13 @@ final fun wang.harlon.tinyui/wang_harlon_tinyui_HttpRequest$stableprop_getter():
 final fun wang.harlon.tinyui/wang_harlon_tinyui_HttpResponse$stableprop_getter(): kotlin/Int // wang.harlon.tinyui/wang_harlon_tinyui_HttpResponse$stableprop_getter|wang_harlon_tinyui_HttpResponse$stableprop_getter(){}[0]
 final fun wang.harlon.tinyui/wang_harlon_tinyui_InMemoryStore$stableprop_getter(): kotlin/Int // wang.harlon.tinyui/wang_harlon_tinyui_InMemoryStore$stableprop_getter|wang_harlon_tinyui_InMemoryStore$stableprop_getter(){}[0]
 final fun wang.harlon.tinyui/wang_harlon_tinyui_Navigator_None$stableprop_getter(): kotlin/Int // wang.harlon.tinyui/wang_harlon_tinyui_Navigator_None$stableprop_getter|wang_harlon_tinyui_Navigator_None$stableprop_getter(){}[0]
+final fun wang.harlon.tinyui/wang_harlon_tinyui_PageError$stableprop_getter(): kotlin/Int // wang.harlon.tinyui/wang_harlon_tinyui_PageError$stableprop_getter|wang_harlon_tinyui_PageError$stableprop_getter(){}[0]
 final fun wang.harlon.tinyui/wang_harlon_tinyui_PageFailure$stableprop_getter(): kotlin/Int // wang.harlon.tinyui/wang_harlon_tinyui_PageFailure$stableprop_getter|wang_harlon_tinyui_PageFailure$stableprop_getter(){}[0]
 final fun wang.harlon.tinyui/wang_harlon_tinyui_PageHost$stableprop_getter(): kotlin/Int // wang.harlon.tinyui/wang_harlon_tinyui_PageHost$stableprop_getter|wang_harlon_tinyui_PageHost$stableprop_getter(){}[0]
+final fun wang.harlon.tinyui/wang_harlon_tinyui_PageModule$stableprop_getter(): kotlin/Int // wang.harlon.tinyui/wang_harlon_tinyui_PageModule$stableprop_getter|wang_harlon_tinyui_PageModule$stableprop_getter(){}[0]
 final fun wang.harlon.tinyui/wang_harlon_tinyui_RuntimeBundle$stableprop_getter(): kotlin/Int // wang.harlon.tinyui/wang_harlon_tinyui_RuntimeBundle$stableprop_getter|wang_harlon_tinyui_RuntimeBundle$stableprop_getter(){}[0]
+final fun wang.harlon.tinyui/wang_harlon_tinyui_SourceMap_Position$stableprop_getter(): kotlin/Int // wang.harlon.tinyui/wang_harlon_tinyui_SourceMap_Position$stableprop_getter|wang_harlon_tinyui_SourceMap_Position$stableprop_getter(){}[0]
+final fun wang.harlon.tinyui/wang_harlon_tinyui_SourceMaps$stableprop_getter(): kotlin/Int // wang.harlon.tinyui/wang_harlon_tinyui_SourceMaps$stableprop_getter|wang_harlon_tinyui_SourceMaps$stableprop_getter(){}[0]
+final fun wang.harlon.tinyui/wang_harlon_tinyui_StackFrame$stableprop_getter(): kotlin/Int // wang.harlon.tinyui/wang_harlon_tinyui_StackFrame$stableprop_getter|wang_harlon_tinyui_StackFrame$stableprop_getter(){}[0]
 final fun wang.harlon.tinyui/wang_harlon_tinyui_StoreValue$stableprop_getter(): kotlin/Int // wang.harlon.tinyui/wang_harlon_tinyui_StoreValue$stableprop_getter|wang_harlon_tinyui_StoreValue$stableprop_getter(){}[0]
 final fun wang.harlon.tinyui/wang_harlon_tinyui_TinyUI$stableprop_getter(): kotlin/Int // wang.harlon.tinyui/wang_harlon_tinyui_TinyUI$stableprop_getter|wang_harlon_tinyui_TinyUI$stableprop_getter(){}[0]
diff --git a/compose/src/androidHostTest/kotlin/wang/harlon/tinyui/BundleSmokeTest.kt b/compose/src/androidHostTest/kotlin/wang/harlon/tinyui/BundleSmokeTest.kt
index 435565f..e400045 100644
--- a/compose/src/androidHostTest/kotlin/wang/harlon/tinyui/BundleSmokeTest.kt
+++ b/compose/src/androidHostTest/kotlin/wang/harlon/tinyui/BundleSmokeTest.kt
@@ -1,11 +1,19 @@
 package wang.harlon.tinyui
 
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.runBlocking
+import kotlinx.coroutines.withContext
+import kotlinx.coroutines.withTimeout
 import wang.harlon.quickjs.JsEngine
 import wang.harlon.quickjs.JsEngineConfig
 import wang.harlon.quickjs.JsValue
+import wang.harlon.tinyui.components.registerBuiltins
+import wang.harlon.tinyui.schema.ComponentRegistry
 import java.io.File
 import kotlin.test.Test
 import kotlin.test.assertEquals
+import kotlin.test.assertTrue
 
 /** Loads what `tinyui build` produced for the sample through the real engine; skips when the sample was not built. */
 class BundleSmokeTest {
@@ -24,4 +32,42 @@ class BundleSmokeTest {
             engine.runBytecode(out.resolve("pages/counter.bin").readBytes()).let { if (it is AutoCloseable) it.close() }
         }
     }
+
+    /** A rejected `await` in the todos page's `loadMore` is E7; its frames map back to the `.tsx` through the built map. */
+    @Test
+    fun stacksFromABuiltPageMapBackToTheSource() = runBlocking {
+        if (!out.isDirectory) return@runBlocking
+        val manifest = BuildManifest.parse(out.resolve("manifest.json").readText())
+        val maps = SourceMaps(mapOf("pages/todos" to out.resolve("pages/todos.js.map").readText(), "@tiny-ui/core" to out.resolve("runtime/core.js.map").readText()))
+        val errors = mutableListOf<PageError>()
+        val sink = object : PageSink {
+            override fun error(error: PageError) { errors += error }
+            override fun log(line: String) {}
+        }
+        val http = object : HttpClient {
+            override suspend fun request(request: HttpRequest): HttpResponse =
+                if (request.url.endsWith("page=1")) HttpResponse(200, """{"items":[{"id":1,"title":"a","done":false}],"next":2}""")
+                else throw HostException("E_HTTP", "500")
+        }
+        val runtime = RuntimeBundle(out.resolve("runtime/core.bin").readBytes(), out.resolve("runtime/native.bin").readBytes())
+        val page = PageModule("pages/todos", out.resolve("pages/todos.bin").readBytes(), manifest.buildId("pages/todos"))
+        val host = PageHost(runtime, page, ComponentRegistry().registerBuiltins(), sink, HostServices(http = http), sourceMaps = maps)
+        host.start()
+        try {
+            // the list only exists once the first page has loaded; node ids are dense, so scan them
+            fun lazyColumn(): Int? = (1..host.tree.size * 2).firstOrNull { host.tree.node(it)?.type == "LazyColumn" }
+            withContext(Dispatchers.Default) { withTimeout(10_000) {
+                while (lazyColumn() == null) delay(20)
+                host.dispatch(lazyColumn()!!, "onReachEnd", "{}")
+                while (errors.none { it.kind == "E7" }) delay(20)
+            } }
+            val e = errors.single { it.kind == "E7" }
+            assertEquals(manifest.buildId("pages/todos"), e.buildId)
+            val own = e.frames.firstOrNull { it.mapped && it.file == "src/pages/todos.tsx" } ?: error("no mapped frame in ${e.frames}; stack=${e.jsStack}")
+            val source = File("../sample/js/src/pages/todos.tsx").readLines()
+            assertTrue("await http.get" in source[own.line - 1], "frame $own points at the await; stack=${e.jsStack}")
+        } finally {
+            host.close()
+        }
+    }
 }
diff --git a/compose/src/commonMain/kotlin/wang/harlon/tinyui/BuildManifest.kt b/compose/src/commonMain/kotlin/wang/harlon/tinyui/BuildManifest.kt
new file mode 100644
index 0000000..19fb7c5
--- /dev/null
+++ b/compose/src/commonMain/kotlin/wang/harlon/tinyui/BuildManifest.kt
@@ -0,0 +1,20 @@
+package wang.harlon.tinyui
+
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.json.jsonArray
+import kotlinx.serialization.json.jsonObject
+import kotlinx.serialization.json.jsonPrimitive
+
+/** `manifest.json` as `tinyui build` writes it: module names and the build id of each. */
+class BuildManifest(val runtime: List<String>, val pages: List<String>, val buildIds: Map<String, String>) {
+    fun buildId(module: String): String = buildIds[module] ?: ""
+
+    companion object {
+        fun parse(json: String): BuildManifest {
+            val root = Json.parseToJsonElement(json).jsonObject
+            val names = { key: String -> root[key]?.jsonArray?.map { it.jsonPrimitive.content } ?: emptyList() }
+            val ids = root["buildIds"]?.jsonObject?.mapValues { it.value.jsonPrimitive.content } ?: emptyMap()
+            return BuildManifest(names("runtime"), names("pages"), ids)
+        }
+    }
+}
diff --git a/compose/src/commonMain/kotlin/wang/harlon/tinyui/PageError.kt b/compose/src/commonMain/kotlin/wang/harlon/tinyui/PageError.kt
new file mode 100644
index 0000000..763f2da
--- /dev/null
+++ b/compose/src/commonMain/kotlin/wang/harlon/tinyui/PageError.kt
@@ -0,0 +1,38 @@
+package wang.harlon.tinyui
+
+/** One line of a JS stack. With a source map the location is the `.tsx` one and [mapped] is true; otherwise it is what the engine printed. */
+class StackFrame(val function: String, val file: String, val line: Int, val column: Int?, val mapped: Boolean) {
+    override fun toString(): String = "at $function ($file:$line${column?.let { ":$it" } ?: ""})"
+}
+
+/**
+ * Every failure of a page in one shape (docs/adr-002 §3.5): [kind] is E1–E7. [frames] is [jsStack] parsed and,
+ * where a source map was available, mapped back to the source; [buildId] pairs [jsStack] with the map offline.
+ */
+class PageError(
+    val kind: String,
+    val page: String,
+    val buildId: String,
+    val message: String,
+    /** E1: the K entry that was running (`dispatch`, `resolve`, `emit`…). */
+    val entry: String? = null,
+    val jsStack: String? = null,
+    val frames: List<StackFrame> = emptyList(),
+    /** E5: the op that was skipped. */
+    val op: String? = null,
+) {
+    override fun toString(): String = buildString {
+        append(kind).append(' ').append(page)
+        if (buildId.isNotEmpty()) append('@').append(buildId)
+        entry?.let { append(" [").append(it).append(']') }
+        append(": ").append(message)
+        op?.let { append(" op=").append(it) }
+        for (f in frames) append("\n    ").append(f)
+    }
+}
+
+interface PageSink {
+    fun error(error: PageError)
+    /** `console.*` and engine log lines. */
+    fun log(line: String)
+}
diff --git a/compose/src/commonMain/kotlin/wang/harlon/tinyui/PageHost.kt b/compose/src/commonMain/kotlin/wang/harlon/tinyui/PageHost.kt
index 8c8ed6e..3c0ef2d 100644
--- a/compose/src/commonMain/kotlin/wang/harlon/tinyui/PageHost.kt
+++ b/compose/src/commonMain/kotlin/wang/harlon/tinyui/PageHost.kt
@@ -50,7 +50,6 @@ import wang.harlon.quickjs.JsRuntime
 import wang.harlon.quickjs.JsValue
 import wang.harlon.quickjs.ObjectTransport
 import wang.harlon.tinyui.node.NodeTree
-import wang.harlon.tinyui.node.PatchProblem
 import wang.harlon.tinyui.node.UINode
 import wang.harlon.tinyui.schema.ComponentRegistry
 import wang.harlon.tinyui.schema.NodeScope
@@ -59,16 +58,16 @@ import wang.harlon.tinyui.schema.SizeValue
 /** Bytecode of the runtime modules every page imports, as `tinyui build` writes them under `runtime/`. */
 class RuntimeBundle(val core: ByteArray, val native: ByteArray)
 
+/** One page's bytecode; [name] is the module name (`pages/todos`) and [buildId] comes from `manifest.json`. */
+class PageModule(val name: String, val bytecode: ByteArray, val buildId: String = "")
+
 /** Everything the host learns about a page's health, in one place (docs/adr-002 §3.5). */
-interface PageSink {
-    fun patchProblem(problem: PatchProblem)
-    fun businessError(entry: String, message: String, stack: String?)
-    fun log(line: String)
+/** The page's failure (E2 / E6): engine gone, error page to be rendered by the host. */
+class PageFailure(val error: PageError) {
+    val kind: String get() = error.kind
+    val message: String get() = error.message
 }
 
-/** The page's failure: engine gone, error page to be rendered by the host. */
-class PageFailure(val kind: String, val message: String)
-
 /**
  * One page: its engine, coroutine scope and node tree (docs/adr-002 §3.4). Every K entry is
  * `entry` + `flush` under one [JsRuntime.withEngine] (docs/js-runtime.html §2). JS runs on a thread
@@ -77,15 +76,16 @@ class PageFailure(val kind: String, val message: String)
 @OptIn(DelicateCoroutinesApi::class, ExperimentalCoroutinesApi::class)
 class PageHost(
     private val runtimeBundle: RuntimeBundle,
-    private val page: ByteArray,
+    private val page: PageModule,
     val registry: ComponentRegistry,
     private val sink: PageSink,
     private val services: HostServices = HostServices.Default,
     private val propsJson: String = "{}",
     /** K entries longer than this are interrupted and fail the page (docs/native-api.md §6). */
     private val entryTimeoutMs: Long = 5_000,
+    private val sourceMaps: SourceMaps = SourceMaps.EMPTY,
 ) {
-    val tree = NodeTree(registry, sink::patchProblem)
+    val tree = NodeTree(registry) { report("E5", it.reason, op = it.op) }
     var failure: PageFailure? by mutableStateOf(null)
         private set
 
@@ -94,7 +94,10 @@ class PageHost(
     private val subscriptions = HashMap<String, AutoCloseable>()
     private val storeVersions = HashMap<String, Long>()
     private val jsThread = newSingleThreadContext("tinyui-page")
-    private val runtime = JsRuntime(JsEngineConfig(moduleScheme = MODULE_SCHEME, logger = sink::log), jsThread)
+    private val runtime = JsRuntime(
+        JsEngineConfig(moduleScheme = MODULE_SCHEME, logger = sink::log, onUnhandledRejection = { report("E7", it.message ?: "unhandled rejection", stack = it.jsStack) }),
+        jsThread,
+    )
     private var entries: Entries? = null
 
     private class Entries(val self: JsRef, val fns: Map<String, JsRef>) {
@@ -112,7 +115,7 @@ class PageHost(
                     step("registering @tiny-ui/native") { registerModule(runtimeBundle.native) }
                     // a registered module only runs on its first import; the runtime must be up before the page
                     evaluateModule("import \"@tiny-ui/core\"; import \"@tiny-ui/native\";").close()
-                    val namespace = runBytecode(page, ObjectTransport.REF) as JsRef
+                    val namespace = runBytecode(page.bytecode, ObjectTransport.REF) as JsRef
                     if (namespace.isPromise) { namespace.close(); error("page module is still pending after microtasks were drained") }
                     val self = evaluate("__tinyui", objects = ObjectTransport.REF) as JsRef
                     val fns = ENTRY_NAMES.associateWith { self.get(it, ObjectTransport.REF) as JsRef }
@@ -186,9 +189,14 @@ class PageHost(
         try { block() } catch (t: Throwable) { throw IllegalStateException("$what: ${t.message}", t) }
 
     private fun fail(kind: String, t: Throwable) {
-        val message = (t as? JsException)?.let { "${it.message}\n${it.jsStack ?: ""}" } ?: t.message ?: t.toString()
-        sink.log("page failed ($kind): $message")
-        failure = PageFailure(kind, message)
+        val error = report(kind, t.message ?: t.toString(), stack = (t as? JsException)?.jsStack)
+        failure = PageFailure(error)
+    }
+
+    private fun report(kind: String, message: String, entry: String? = null, stack: String? = null, op: String? = null): PageError {
+        val error = PageError(kind, page.name, page.buildId, message, entry, stack, sourceMaps.frames(stack), op)
+        sink.error(error)
+        return error
     }
 
     private fun registerHost(engine: JsEngine) {
@@ -201,13 +209,14 @@ class PageHost(
             val detail = (args[1] as? JsValue.Str)?.value ?: ""
             val fields = runCatching { Json.parseToJsonElement(detail).jsonObject }.getOrNull()
             if (kind == "E1" && fields != null) {
-                sink.businessError(
+                report(
+                    "E1",
+                    fields["message"]?.jsonPrimitive?.contentOrNull ?: "",
                     entry = fields["entry"]?.jsonPrimitive?.contentOrNull ?: "?",
-                    message = fields["message"]?.jsonPrimitive?.contentOrNull ?: "",
                     stack = fields["stack"]?.jsonPrimitive?.contentOrNull,
                 )
             } else {
-                sink.businessError(entry = "?", message = "unparseable $kind report: $detail", stack = null)
+                report("E1", "unparseable $kind report: $detail")
             }
             JsValue.Undefined
         }
diff --git a/compose/src/commonMain/kotlin/wang/harlon/tinyui/SourceMaps.kt b/compose/src/commonMain/kotlin/wang/harlon/tinyui/SourceMaps.kt
new file mode 100644
index 0000000..e381711
--- /dev/null
+++ b/compose/src/commonMain/kotlin/wang/harlon/tinyui/SourceMaps.kt
@@ -0,0 +1,107 @@
+package wang.harlon.tinyui
+
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.json.jsonArray
+import kotlinx.serialization.json.jsonObject
+import kotlinx.serialization.json.jsonPrimitive
+
+/**
+ * The `.js.map` files `tinyui build` wrote, keyed by module name (`pages/todos`, `@tiny-ui/core`), parsed on first use.
+ * Ship them in debug builds only (docs/build-chain.md); release stacks are mapped offline with the build id.
+ */
+class SourceMaps(maps: Map<String, String>) {
+    private val entries: Map<String, Lazy<SourceMap>> = maps.mapValues { (_, json) -> lazy { SourceMap(json) } }
+
+    /** Parses an engine stack (`    at fn (module:line:col)` per line), mapping the frames whose module has a map. */
+    fun frames(stack: String?): List<StackFrame> {
+        if (stack.isNullOrBlank()) return emptyList()
+        return stack.lineSequence().mapNotNull(::frame).toList()
+    }
+
+    private fun frame(line: String): StackFrame? {
+        val m = FRAME.matchEntire(line.trim()) ?: return null
+        val function = m.groups[1]?.value ?: "<anonymous>"
+        val location = m.groups[2]?.value ?: m.groups[3]!!.value
+        val loc = LOCATION.matchEntire(location)
+            ?: return StackFrame(function, location, 0, null, mapped = false)
+        val file = loc.groupValues[1]
+        val lineNo = loc.groupValues[2].toInt()
+        val column = loc.groups[3]?.value?.toInt()
+        // a broken map must not cost the report itself: fall back to the engine's frame
+        val mapped = runCatching { entries[file.removePrefix("${PageHost.MODULE_SCHEME}:")]?.value?.lookup(lineNo, column) }.getOrNull()
+        return if (mapped != null) StackFrame(function, mapped.file, mapped.line, mapped.column, mapped = true)
+        else StackFrame(function, file, lineNo, column, mapped = false)
+    }
+
+    companion object {
+        val EMPTY = SourceMaps(emptyMap())
+        private val FRAME = Regex("""at (?:(.+?) \((.+)\)|(.+))""")
+        private val LOCATION = Regex("""(.+?):(\d+)(?::(\d+))?""")
+    }
+}
+
+/** Source map v3 (`mappings` VLQ), enough to answer "which source line is generated line L, column C". */
+internal class SourceMap(json: String) {
+    class Position(val file: String, val line: Int, val column: Int)
+
+    private val sources: List<String>
+    /** Per generated line: segments as (generatedColumn, sourceIndex, sourceLine, sourceColumn), all 0-based. */
+    private val lines: List<IntArray>
+
+    init {
+        val root = Json.parseToJsonElement(json).jsonObject
+        sources = root["sources"]?.jsonArray?.map { it.jsonPrimitive.content } ?: emptyList()
+        lines = decode(root["mappings"]?.jsonPrimitive?.content ?: "")
+    }
+
+    /** [line] and [column] as the engine prints them (1-based); without a column the first segment of the line answers. */
+    fun lookup(line: Int, column: Int?): Position? {
+        val segments = lines.getOrNull(line - 1) ?: return null
+        if (segments.isEmpty()) return null
+        var best = -1
+        val target = (column ?: 1) - 1
+        for (i in 0 until segments.size / 4) {
+            if (segments[i * 4] <= target) best = i else break
+        }
+        if (best < 0) best = 0
+        val source = sources.getOrNull(segments[best * 4 + 1]) ?: return null
+        return Position(source, segments[best * 4 + 2] + 1, segments[best * 4 + 3] + 1)
+    }
+
+    private fun decode(mappings: String): List<IntArray> {
+        val out = ArrayList<IntArray>()
+        var source = 0; var sourceLine = 0; var sourceColumn = 0
+        for (group in mappings.split(';')) {
+            var generated = 0
+            val segments = ArrayList<Int>()
+            if (group.isNotEmpty()) for (segment in group.split(',')) {
+                val fields = vlq(segment)
+                generated += fields[0]
+                if (fields.size >= 4) {
+                    source += fields[1]; sourceLine += fields[2]; sourceColumn += fields[3]
+                    segments += generated; segments += source; segments += sourceLine; segments += sourceColumn
+                }
+            }
+            out += segments.toIntArray()
+        }
+        return out
+    }
+
+    private fun vlq(segment: String): IntArray {
+        val values = ArrayList<Int>()
+        var value = 0; var shift = 0
+        for (c in segment) {
+            val digit = BASE64.indexOf(c)
+            require(digit >= 0) { "bad VLQ character '$c'" }
+            value = value or ((digit and 31) shl shift)
+            if (digit and 32 != 0) { shift += 5; continue }
+            values += if (value and 1 != 0) -(value shr 1) else value shr 1
+            value = 0; shift = 0
+        }
+        return values.toIntArray()
+    }
+
+    private companion object {
+        const val BASE64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
+    }
+}
diff --git a/compose/src/commonMain/kotlin/wang/harlon/tinyui/TinyUI.kt b/compose/src/commonMain/kotlin/wang/harlon/tinyui/TinyUI.kt
index 0ea9d7a..82c61a2 100644
--- a/compose/src/commonMain/kotlin/wang/harlon/tinyui/TinyUI.kt
+++ b/compose/src/commonMain/kotlin/wang/harlon/tinyui/TinyUI.kt
@@ -5,4 +5,7 @@ import wang.harlon.quickjs.QuickJs
 object TinyUI {
     /** Version of the quickjs-kmp SDK this build links against. */
     val engineVersion: String get() = QuickJs.sdkVersion
+
+    /** Debug builds show the (mapped) JS stack on the page-failure screen; keep false in release. */
+    var debug: Boolean = false
 }
diff --git a/compose/src/commonMain/kotlin/wang/harlon/tinyui/TinyUIPage.kt b/compose/src/commonMain/kotlin/wang/harlon/tinyui/TinyUIPage.kt
index bd7ec87..099bb9b 100644
--- a/compose/src/commonMain/kotlin/wang/harlon/tinyui/TinyUIPage.kt
+++ b/compose/src/commonMain/kotlin/wang/harlon/tinyui/TinyUIPage.kt
@@ -1,12 +1,19 @@
 package wang.harlon.tinyui
 
 import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.verticalScroll
+import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.DisposableEffect
 import androidx.compose.runtime.key
 import androidx.compose.runtime.remember
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.font.FontFamily
+import androidx.compose.ui.unit.dp
 import wang.harlon.tinyui.schema.ComponentRegistry
 
 /**
@@ -16,16 +23,19 @@ import wang.harlon.tinyui.schema.ComponentRegistry
 @Composable
 fun TinyUIPage(
     runtime: RuntimeBundle,
-    page: ByteArray,
+    page: PageModule,
     registry: ComponentRegistry,
     sink: PageSink,
     services: HostServices = HostServices.Default,
     propsJson: String = "{}",
     modifier: Modifier = Modifier,
-    error: @Composable (PageFailure) -> Unit = { Text("TinyUI page failed (${it.kind}): ${it.message}") },
+    sourceMaps: SourceMaps = SourceMaps.EMPTY,
+    error: @Composable (PageFailure) -> Unit = { PageFailureScreen(it) },
     onHost: (PageHost) -> Unit = {},
 ) {
-    val host = remember(runtime, page, registry, sink, services, propsJson) { PageHost(runtime, page, registry, sink, services, propsJson) }
+    val host = remember(runtime, page, registry, sink, services, propsJson, sourceMaps) {
+        PageHost(runtime, page, registry, sink, services, propsJson, sourceMaps = sourceMaps)
+    }
     DisposableEffect(host) {
         onHost(host)
         host.start()
@@ -41,3 +51,15 @@ fun TinyUIPage(
     }
 }
 
+
+/** The default failure screen: kind and message, plus the stack when [TinyUI.debug] is on. */
+@Composable
+fun PageFailureScreen(failure: PageFailure) {
+    Column(Modifier.padding(16.dp).verticalScroll(rememberScrollState())) {
+        Text("TinyUI page failed (${failure.kind})", style = MaterialTheme.typography.titleMedium)
+        Text(failure.message, style = MaterialTheme.typography.bodyMedium)
+        if (TinyUI.debug) {
+            for (frame in failure.error.frames) Text(frame.toString(), style = MaterialTheme.typography.bodySmall, fontFamily = FontFamily.Monospace)
+        }
+    }
+}
diff --git a/compose/src/commonTest/kotlin/wang/harlon/tinyui/PageHostTest.kt b/compose/src/commonTest/kotlin/wang/harlon/tinyui/PageHostTest.kt
index 4e45545..17aa661 100644
--- a/compose/src/commonTest/kotlin/wang/harlon/tinyui/PageHostTest.kt
+++ b/compose/src/commonTest/kotlin/wang/harlon/tinyui/PageHostTest.kt
@@ -8,7 +8,6 @@ import kotlinx.coroutines.withContext
 import kotlinx.coroutines.withTimeout
 import wang.harlon.quickjs.JsBytecode
 import wang.harlon.tinyui.components.registerBuiltins
-import wang.harlon.tinyui.node.PatchProblem
 import wang.harlon.tinyui.schema.ComponentRegistry
 import kotlin.test.Test
 import kotlin.test.assertEquals
@@ -18,9 +17,9 @@ import kotlin.test.assertNull
 /** Drives PageHost with a hand-written stand-in for `@tiny-ui/core`: the K/J entry shapes, not the real runtime. */
 class PageHostTest {
     private val log = mutableListOf<String>()
+    private val errors = mutableListOf<PageError>()
     private val sink = object : PageSink {
-        override fun patchProblem(problem: PatchProblem) { log += "E5 $problem" }
-        override fun businessError(entry: String, message: String, stack: String?) { log += "E1 $message @$entry stack=${stack != null}" }
+        override fun error(error: PageError) { errors += error; log += error.toString() }
         override fun log(line: String) { log += line }
     }
 
@@ -41,6 +40,7 @@ class PageHostTest {
                 if (id === 2 && event === "onClick") handler();
                 if (event === "onTimer") __host_call("timer.schedule", 7, JSON.stringify({ ms: 10 }));
                 if (event === "onBoom") { try { throw new Error("boom"); } catch (e) { __host_report("E1", JSON.stringify({ entry: "dispatch", message: e.message, stack: e.stack })); } }
+                if (event === "onReject") Promise.reject(new Error("nobody catches"));
                 if (event === "onQuery") patches.push(["p",1,"text", __host_query("store.get", JSON.stringify({ key: "cart" })) + "|" + __host_query("i18n.t", JSON.stringify({ key: "hi" })) + "|" + JSON.parse(__host_query("device.info", "{}")).os]);
                 if (event === "onHttp") __host_call("http.request", 9, JSON.stringify({ method: "GET", url: "/todos" }));
                 if (event === "onSubscribe") { __host_send("store.subscribe", JSON.stringify({ key: "cart" })); __host_send("store.subscribe", JSON.stringify({ key: "cart" })); __host_send("events.subscribe", JSON.stringify({ topic: "net" })); __host_send("events.subscribe", JSON.stringify({ topic: "net" })); patches.push(["p",1,"text","subscribed"]); }
@@ -52,7 +52,7 @@ class PageHostTest {
         export const VERSION = "stub";
     """)
     private val native = module("@tiny-ui/native", "export const NATIVE = 1;")
-    private val page = module("pages/counter", "export default function Counter() { return 'page'; }")
+    private val page = PageModule("pages/counter", module("pages/counter", "export default function Counter() { return 'page'; }"), "abcd1234")
 
     private val store = InMemoryStore().apply { set("cart", """{"n":2}""") }
     private val services = HostServices(
@@ -65,7 +65,8 @@ class PageHostTest {
         },
     )
 
-    private fun host(props: String = "{}") = PageHost(RuntimeBundle(core, native), page, ComponentRegistry().registerBuiltins(), sink, services, props)
+    private fun host(props: String = "{}", maps: SourceMaps = SourceMaps.EMPTY) =
+        PageHost(RuntimeBundle(core, native), page, ComponentRegistry().registerBuiltins(), sink, services, props, sourceMaps = maps)
 
     // runTest's virtual time never advances the real engine thread: wait on a real dispatcher
     private suspend fun PageHost.await(check: () -> Boolean) =
@@ -113,7 +114,48 @@ class PageHostTest {
         host.dispatch(2, "onTimer", "{}")
         host.await { host.tree.node(1)!!.props["text"] == "timer 7" }
         host.dispatch(2, "onBoom", "{}")
-        host.await { log.any { it.startsWith("E1 boom") } }
+        host.await { errors.any { it.kind == "E1" } }
+        val e = errors.single { it.kind == "E1" }
+        assertEquals("boom", e.message)
+        assertEquals("dispatch", e.entry)
+        assertEquals("pages/counter", e.page)
+        assertEquals("abcd1234", e.buildId)
+        val frame = e.frames.first()
+        assertEquals("dispatch", frame.function)
+        assertEquals("@tiny-ui/core", frame.file, "engine frames name the module; stack=${e.jsStack}")
+        assertEquals(16, frame.line)
+        assertNotNull(frame.column, "bytecode compiled with --strip-source keeps columns; stack=${e.jsStack}")
+        host.close()
+    }
+
+    @Test
+    fun framesAreMappedThroughTheModuleSourceMap() = runTest {
+        // generated line 16 → src/core.ts line 3 column 7: fifteen empty groups, then one segment [0, 0, 2, 6]
+        val map = SourceMaps(mapOf("@tiny-ui/core" to """{"version":3,"sources":["src/core.ts"],"mappings":";;;;;;;;;;;;;;;AAEM"}"""))
+        val host = host(maps = map)
+        host.start()
+        host.await { host.tree.root.children.isNotEmpty() }
+        host.dispatch(2, "onBoom", "{}")
+        host.await { errors.any { it.kind == "E1" } }
+        val frame = errors.single { it.kind == "E1" }.frames.first()
+        assertEquals(true, frame.mapped)
+        assertEquals("src/core.ts", frame.file)
+        assertEquals(3, frame.line)
+        assertEquals(7, frame.column)
+        host.close()
+    }
+
+    @Test
+    fun unhandledRejectionsAreE7() = runTest {
+        val host = host()
+        host.start()
+        host.await { host.tree.root.children.isNotEmpty() }
+        host.dispatch(2, "onReject", "{}")
+        host.await { errors.any { it.kind == "E7" } }
+        val e = errors.single { it.kind == "E7" }
+        assertEquals(true, "nobody catches" in e.message, e.message)
+        assertEquals(true, e.frames.isNotEmpty(), "stack=${e.jsStack}")
+        assertNull(host.failure)
         host.close()
     }
 
@@ -149,6 +191,8 @@ class PageHostTest {
         val failure = assertNotNull(host.failure)
         assertEquals("E2", failure.kind)
         assertEquals(true, "render exploded" in failure.message)
+        assertEquals(true, failure.error.frames.any { it.function == "flush" && it.file == "@tiny-ui/core" }, "stack=${failure.error.jsStack}")
+        assertEquals(1, errors.count { it.kind == "E2" }, "E2 goes through the sink once")
         host.close()
     }
 
@@ -159,6 +203,7 @@ class PageHostTest {
         host.start()
         host.await { host.failure != null }
         assertEquals("E6", host.failure!!.kind)
+        assertEquals("E6", errors.single().kind)
         host.close()
     }
 
diff --git a/docs/README.md b/docs/README.md
index 8c7b010..cdb92cb 100644
--- a/docs/README.md
+++ b/docs/README.md
@@ -40,7 +40,7 @@ JS                                   桥                          Kotlin
 | 编号 | 主题 | 状态 | 结论 |
 |---|---|---|---|
 | [ADR-001](./adr-001-reactivity-model.md) | 状态管理与更新模型 | 已定（2026-09-14，所有权 / 清理 2026-09-15 补定） | 运行时 Signal（细粒度绑定），不做 vdom diff，不走编译期静态依赖；作用域只开在结构边界，同步渲染期外创建 effect 抛错 |
-| [ADR-002](./adr-002-bridge-communication.md) | JS 与 Kotlin 通信机制（含序列化） | 已定（2026-09-15） | 双向入口 5 + 5；JS 专用线程、K 入口不等待；一次 K 入口一个事务；每页一个引擎；错误六类一个 sink；JSON 文本载荷 |
+| [ADR-002](./adr-002-bridge-communication.md) | JS 与 Kotlin 通信机制（含序列化） | 已定（2026-09-15） | 双向入口 5 + 5；JS 专用线程、K 入口不等待；一次 K 入口一个事务；每页一个引擎；错误七类一个 sink；JSON 文本载荷 |
 | [ADR-003](./adr-003-kotlin-node-tree-and-registry.md) | Kotlin 侧节点表与组件注册 | 已定（2026-09-15） | 节点即重组单元；JS 线程直接写快照状态、主线程只重组；App 级注册表 + 清单下发；prop / event schema 写入时转换 |
 | [ADR-004](./adr-004-events-and-input-ownership.md) | 事件与输入状态归属 | 已定（2026-09-15） | 事件三分（离散 / 流式输入 / 连续），60 fps 状态留 Kotlin；新增 `x` 命令 op（ref + cmd）；文本框 initial prop + 命令 + 事件，不受控回写 |
 | [ADR-005](./adr-005-engine.md) | JS 引擎选型 | 已定（2026-09-15） | MicroQuickJS → QuickJS（ES2025，经 quickjs-kmp）；原生 ESM 必选；不降级 ES5；热下发不在本期 |
@@ -99,7 +99,7 @@ tinyui/
 
 | 文件 | 主题 | 状态 |
 |---|---|---|
-| [build-chain.md](./build-chain.md) | 构建链：TSX → ESM 模块字节码，esbuild 选型，字节码由 CLI 经 `qjsc-kmp` 生成 | 已完成（2026-09-16） |
+| [build-chain.md](./build-chain.md) | 构建链：TSX → ESM 模块字节码，esbuild 选型，字节码由 CLI 经 `qjsc-kmp` 生成；§7 错误上报与 source map 回映射 | 已完成（2026-09-16；§7 2026-09-17） |
 | [app-model.md](./app-model.md) | 应用模型：路由、生命周期、跨页状态在 Kotlin；页面之间经 Kotlin 中转的四种通信 | 已对齐（2026-09-16），API 面归 C 组 |
 | [js-runtime.html](./js-runtime.html) | **JS 层总览**：七样运行时对象、四个时期、响应式闭环、一个页面的一生、规则表。先读这份（浏览器打开） | 已定（2026-09-16） |
 | [runtime-api.md](./runtime-api.md) | `@tiny-ui/core` v1 的 API 定义、页面模块契约、桥入口 | 已定（2026-09-16） |
diff --git a/docs/adr-002-bridge-communication.md b/docs/adr-002-bridge-communication.md
index a790603..196706f 100644
--- a/docs/adr-002-bridge-communication.md
+++ b/docs/adr-002-bridge-communication.md
@@ -11,6 +11,7 @@
 > - **每页一 Runtime 的论证重写**：§3.4 表中"后续页面只能走源码 evaluate"是 MicroQuickJS 特有问题，作废。QuickJS 下真正的替代是"一 Runtime 多 Context"（共享堆、原子表、shape），但限额与 interrupt 是 Runtime 级、卸载 = 关 Runtime 仍是最干净的回收，结论不变。2026-09-16 在 quickjs-kmp 侧实测后不翻：Runtime + Context 基线仅 155 KB，多 Context 每页只省约 100 KB；模块缓存挂在 JSContext 上，运行时模块每页仍要各编译一遍，共享堆换不来共享 `@tiny-ui/core`；微任务队列也是 Runtime 级，多页共享会打破"一次 K 入口 = 一个事务"的页级边界。quickjs-kmp 已定为不暴露多 Context（其 docs/decisions.md「Runtime / Context」条）
 > - K0 改为"注册运行时模块（`@tiny-ui/core` / `@tiny-ui/native`）→ 求值页面模块（Promise，排空后取 namespace）→ 调 `default` 导出挂载"；"每引擎一个程序"的硬限制消失
 > - Promise 原生，J3 / K3 的对接不再需要 polyfill
+> - **sink 的形态（2026-09-17）**：七类错误统一为一个 `PageError`（kind / 页面 / buildId / message / 入口 / 原始栈 / 映射后的帧 / op）经 `PageSink.error()` 交出，`log()` 只收 `console.*`；栈经 source map 回映射到 `.tsx`，dev 进包实时映射、release 离线，见 build-chain.md §7
 > - **新增 E7：未处理的 Promise rejection**——业务 `async` 里抛出且无人 catch，既不经入口 catch（非 E1）也非宿主失败（非 E3）；由 quickjs-kmp 接 `JS_SetHostPromiseRejectionTracker` 上报，页面继续。**E6 增加栈溢出**：`JS_SetMaxStackSize` 触发归入引擎级失败
 
 
diff --git a/docs/build-chain.md b/docs/build-chain.md
index 2a6a4f5..133c55c 100644
--- a/docs/build-chain.md
+++ b/docs/build-chain.md
@@ -1,8 +1,8 @@
 # 构建链：TSX → ESM 模块字节码
 
-- 状态：已完成（2026-09-16，PR #2）；sample 在 Android 模拟器与 iOS 模拟器上显示 `tinyui:pages/home`
+- 状态：已完成（2026-09-16，PR #2；2026-09-17 加 §7 错误上报与 source map）；sample 在 Android 模拟器与 iOS 模拟器上显示 `tinyui:pages/home`
 - 来源：[ADR-005](./adr-005-engine.md) §4 "语言目标 / 模块" 两行的展开；roadmap A 组"构建链打通"
-- 范围：`@tiny-ui/cli` 的 `tinyui build`、`compose/` 的 K0 加载序列、sample 的接线与 CI。自动 thunk（roadmap C 组）、字节码行号回映射、`qjsc-kmp` 二进制分发、页面级配置文件不在本期
+- 范围：`@tiny-ui/cli` 的 `tinyui build`、`compose/` 的 K0 加载序列、sample 的接线与 CI。自动 thunk（roadmap C 组）、`qjsc-kmp` 二进制分发、页面级配置文件不在本期；字节码行号回映射见 §7
 
 ## 1. 目标与验收
 
@@ -98,4 +98,16 @@ rolldown 是真正的备选（Rollup 同形 API、oxc 转译）。CLI 只包一
 | `settings.gradle.kts` | 有 `quickjs-kmp.dir` 时把 `qjsc-kmp` 路径传给 Exec 任务 |
 | CI | gradle job 加 setup-node + pnpm，clone quickjs-kmp 的 catalog 版本 tag 编 `buildHostTools`（qjsc-kmp）与 `buildNativeHostJni`（Android host 测试要加载宿主 JNI 库，Maven 包里没有），经 `TINYUI_QJSC` / `TINYUI_QUICKJS_HOST_JNI` 传入；ios.yml 同样 |
 
-source map 随 `.js` 输出到 `.map`；行列号回映射到 TSX 归 E1 / E2 错误上报那一期。
+## 7. 错误上报与 source map
+
+定于 2026-09-17。七类错误（ADR-002 §3.5，E1～E7）统一成一个 `PageError`（kind、页面模块名、buildId、message、E1 的入口名、原始 JS 栈、解析 / 映射后的帧、E5 的 op 原文）经 `PageSink.error()` 交给宿主；`console.*` 与引擎日志仍走 `PageSink.log()`。E2 / E6 同时置 `PageHost.failure`，错误页由 Kotlin 渲染，`TinyUI.debug` 为 true 时显示映射后的栈；E1 / E7 只上报不叠层，页面继续。
+
+**栈的形态**：QuickJS 打印 `at fn (模块名:行:列)`，`--strip-source` 保留行与列（宿主测试断言）。J3 的 `HostError` 在 K3 `reject` 处创建，它自己的栈只会指向 core 的入口，所以 `call()` 时先记下调用点的栈（约 1 µs），rejection 带着它——`await http.get` 无人 catch 的 E7 因此指向业务的 `await` 那一行。
+
+**回映射在哪做**：dev 构建把 `.js.map` 一起打进 App，Kotlin 侧 `SourceMaps` 按模块名惰性解析（source map v3 的 VLQ，约百行，无依赖），只解析栈里出现的行；release 不进包，sink 拿到原始栈 + `buildId`，离线对 map（Sentry / Crashlytics 的做法）。否掉 JS 侧运行时映射：字节码与内存都涨，出错时还要跑 JS。
+
+**buildId**：CLI 对每个模块的 `.js` 取 sha256 前 8 位写进 `manifest.json` 的 `buildIds`，`BuildManifest.parse` 读出，`PageModule(name, bytecode, buildId)` 交给 `PageHost`。宿主发布时把 `out/` 目录整体归档即可对回。
+
+**map 的路径**：thunk pass 的内联 map 以绝对路径作 `source`（相对路径会被 esbuild 再按文件目录解析一次，出现 `src/pages/src/pages/` 的重复，2026-09-17 修），esbuild 输出后 CLI 把 `sources` 改写为相对项目根（`src/pages/todos.tsx`、`../../packages/core/src/host.ts`），运行时与离线符号化都以此显示。
+
+**sample 的接线**：`collectTinyUIResources` 默认连 `.js.map` 一起进资源，`-Ptinyui.maps=false` 不带；`App.kt` 读 manifest，能读到的 map 交给 `SourceMaps`，读不到就按原始栈上报。真实 App 按构建变体决定要不要带 map，库不替宿主决定。
diff --git a/docs/jsx-transform.md b/docs/jsx-transform.md
index 995a8b2..cd516b9 100644
--- a/docs/jsx-transform.md
+++ b/docs/jsx-transform.md
@@ -71,7 +71,7 @@ h(Text, { text: thunk(() => "Count: " + count()), color: thunk(() => theme.prima
 
 ## 5. source map
 
-本 pass 用字符串局部替换生成 map，以内联 `sourceMappingURL` 交给 esbuild；esbuild 与自己的 JSX / 合并 map 组合后输出 `pages/<name>.js.map`，`sources` 指向原 `.tsx`。字节码保留行号（`--strip-source`），E1 / E2 的栈里是 `.js` 的行列，经 `.js.map` 回到 `.tsx`，这一步在错误上报那一期做。
+本 pass 用字符串局部替换生成 map，以内联 `sourceMappingURL` 交给 esbuild；esbuild 与自己的 JSX / 合并 map 组合后输出 `pages/<name>.js.map`，`sources` 指向原 `.tsx`。字节码保留行列（`--strip-source`），E1 / E2 的栈里是 `.js` 的行列，经 `.js.map` 回到 `.tsx`（[build-chain.md](./build-chain.md) §7）。
 
 ## 6. 实现（非契约）
 
diff --git a/docs/roadmap.md b/docs/roadmap.md
index a2c4b62..56708f3 100644
--- a/docs/roadmap.md
+++ b/docs/roadmap.md
@@ -38,6 +38,7 @@
 | `@tiny-ui/native` 的 `navigation` / `store` / `events` API 面与 `Navigator` 接口（[app-model.md](./app-model.md)）；`push` 的 Promise 糖做不做 | app-model.md | 已定（native-api.md §2–§5；Promise 糖不做） |
 | E3 错误 code 表、K 入口超时阈值、连续事件节流阈值 | ADR-002 / 004 | 已定（native-api.md §6） |
 | `Placeholder` 在 release 的表现 | ADR-003 | 已定（components.md §5：零尺寸空 Box） |
+| 错误上报：`PageError` 单 sink、E7 接入、栈经 source map 回映射到 `.tsx`、buildId | ADR-002 §3.5 | 已完成（2026-09-17，[build-chain.md](./build-chain.md) §7） |
 
 ## D. 明确推迟（记录不做，触发条件写清）
 
diff --git a/docs/runtime-api.md b/docs/runtime-api.md
index aa99458..a8c36b9 100644
--- a/docs/runtime-api.md
+++ b/docs/runtime-api.md
@@ -272,8 +272,11 @@ export default function Home(props: HomeProps): Node { … }
 |---|---|
 | E1 handler / 回调抛错 | `dispatch` / `resolve` / `reject` / `emit` 内 catch → `__host_report("E1")` → 入口正常返回，Kotlin 照常调 `flush()` |
 | E2 渲染期抛错 | `mount()` 或 `flush()` **直接抛出**（`JsException` 带 JS 栈），运行时先清空 patch 缓冲；Kotlin 不再调 `flush()`，判页面失败 |
-| E3 `reject` 到达 | 对应 Promise reject；无人 catch 走 E7（引擎的 unhandled rejection 回调，Kotlin 侧接） |
+| E3 `reject` 到达 | 对应 Promise reject 为 `HostError`，其 `stack` 是 J3 调用点（`call()` 时记下），不是 `reject` 到达处；无人 catch 走 E7（引擎的 unhandled rejection 回调，Kotlin 侧接） |
 | E4 `__host_query` 抛错 | 在 JS 里是普通异常，落入 E1 |
+| E7 未处理 rejection | quickjs-kmp `onUnhandledRejection` → Kotlin `PageError("E7")`，页面继续 |
+
+Kotlin 侧的统一上报对象 `PageError` 与栈回映射见 [build-chain.md](./build-chain.md) §7。
 
 ## 10. 与 ADR 的差异说明
 
diff --git a/packages/cli/src/build.ts b/packages/cli/src/build.ts
index f3b1867..b7ed76e 100644
--- a/packages/cli/src/build.ts
+++ b/packages/cli/src/build.ts
@@ -1,6 +1,7 @@
 import { build as esbuild, type Plugin } from "esbuild";
+import { createHash } from "node:crypto";
 import { mkdir, readdir, readFile, rm, writeFile } from "node:fs/promises";
-import { dirname, join, relative, resolve, sep } from "node:path";
+import { dirname, isAbsolute, join, relative, resolve, sep } from "node:path";
 import { compileModule, findQjsc } from "./qjsc.ts";
 import { TransformError, transformJsx } from "./transform.ts";
 
@@ -22,6 +23,8 @@ export interface BuiltModule {
     name: string;
     js: string;
     map: string;
+    /** First 8 hex digits of the sha256 of the ESM output: pairs a stack trace with its source map (docs/build-chain.md). */
+    buildId: string;
     bin?: string;
 }
 
@@ -34,6 +37,7 @@ export interface BuildResult {
 export interface Manifest {
     runtime: string[];
     pages: string[];
+    buildIds: Record<string, string>;
 }
 
 export async function build(options: BuildOptions): Promise<BuildResult> {
@@ -53,6 +57,10 @@ export async function build(options: BuildOptions): Promise<BuildResult> {
     await rm(join(out, "runtime"), { recursive: true, force: true });
     const runtime = await bundleRuntime(root, out);
     const pages = await bundlePages(root, out, pageNames);
+    for (const m of [...runtime, ...pages]) {
+        m.buildId = createHash("sha256").update(await readFile(m.js)).digest("hex").slice(0, 8);
+        await rootRelativeSources(root, m.map);
+    }
     if (qjsc) {
         for (const m of [...runtime, ...pages]) {
             m.bin = m.js.replace(/\.js$/, ".bin");
@@ -61,7 +69,11 @@ export async function build(options: BuildOptions): Promise<BuildResult> {
     }
 
     const manifest = join(out, "manifest.json");
-    const content: Manifest = { runtime: runtime.map((m) => m.name), pages: pages.map((m) => m.name) };
+    const content: Manifest = {
+        runtime: runtime.map((m) => m.name),
+        pages: pages.map((m) => m.name),
+        buildIds: Object.fromEntries([...runtime, ...pages].map((m) => [m.name, m.buildId])),
+    };
     await writeFile(manifest, JSON.stringify(content, null, 2) + "\n");
     return { runtime, pages, manifest };
 }
@@ -96,7 +108,7 @@ async function bundleRuntime(root: string, out: string): Promise<BuiltModule[]>
             outfile,
             external: RUNTIME_MODULES.filter((m) => m !== name),
         });
-        built.push({ name, js: outfile, map: outfile + ".map" });
+        built.push({ name, js: outfile, map: outfile + ".map", buildId: "" });
     }
     return built;
 }
@@ -118,8 +130,19 @@ async function bundlePages(root: string, out: string, pages: Map<string, string>
     });
     return [...pages.keys()].map((name) => {
         const js = join(outdir, name.slice("pages/".length) + ".js");
-        return { name, js, map: js + ".map" };
+        return { name, js, map: js + ".map", buildId: "" };
+    });
+}
+
+/** esbuild writes `sources` relative to the map; the runtime and offline symbolication want paths from the project root. */
+async function rootRelativeSources(root: string, mapFile: string): Promise<void> {
+    const map = JSON.parse(await readFile(mapFile, "utf8")) as { sources: string[] };
+    map.sources = map.sources.map((s) => {
+        // a bare scheme (`tinyui:jsx-shim`) stays; an absolute path (`/x` or `C:\x`) or a map-relative one becomes root-relative
+        if (!isAbsolute(s) && /^[a-z][a-z0-9+.-]*:/i.test(s)) return s;
+        return relative(root, resolve(dirname(mapFile), s)).split(sep).join("/");
     });
+    await writeFile(mapFile, JSON.stringify(map));
 }
 
 const JSX_SHIM = "tinyui:jsx-shim";
@@ -140,7 +163,8 @@ const pagePlugin: Plugin = {
         api.onLoad({ filter: TSX }, async (args) => {
             const source = await readFile(args.path, "utf8");
             try {
-                const { code, map } = transformJsx(relative(api.initialOptions.absWorkingDir ?? "", args.path), source);
+                // the map's `source` is resolved against the file's directory, so it has to be the absolute path
+                const { code, map } = transformJsx(args.path, source);
                 const inline = Buffer.from(map).toString("base64");
                 return { contents: `${code}\n//# sourceMappingURL=data:application/json;base64,${inline}`, loader: "tsx" };
             } catch (e) {
diff --git a/packages/cli/test/build.test.ts b/packages/cli/test/build.test.ts
index 76eef57..635eb0b 100644
--- a/packages/cli/test/build.test.ts
+++ b/packages/cli/test/build.test.ts
@@ -63,7 +63,9 @@ describe("tinyui build", () => {
             assert.ok(map.sources.length > 0, `${m.name} has sources`);
         }
         const home = JSON.parse(await readFile(join(out, "pages", "home.js.map"), "utf8")) as { sources: string[] };
-        assert.ok(home.sources.some((s) => s.endsWith("src/pages/home.tsx")));
+        assert.ok(home.sources.includes("src/pages/home.tsx"), `sources are root-relative: ${home.sources}`);
+        const core = JSON.parse(await readFile(join(out, "runtime", "core.js.map"), "utf8")) as { sources: string[] };
+        assert.ok(core.sources.every((s) => s.includes(":") || !s.startsWith("/")), `runtime sources are relative: ${core.sources}`);
     });
 
     it("bundles each runtime module on its own", async () => {
@@ -86,10 +88,11 @@ describe("tinyui build", () => {
 
     it("lists everything in manifest.json", async () => {
         const manifest = JSON.parse(await readFile(result.manifest, "utf8"));
-        assert.deepEqual(manifest, {
-            runtime: ["@tiny-ui/core", "@tiny-ui/native"],
-            pages: ["pages/home", "pages/nested/detail"],
-        });
+        assert.deepEqual(manifest.runtime, ["@tiny-ui/core", "@tiny-ui/native"]);
+        assert.deepEqual(manifest.pages, ["pages/home", "pages/nested/detail"]);
+        assert.deepEqual(Object.keys(manifest.buildIds), [...manifest.runtime, ...manifest.pages]);
+        for (const id of Object.values(manifest.buildIds)) assert.match(id as string, /^[0-9a-f]{8}$/);
+        assert.equal(manifest.buildIds["pages/home"], result.pages[0]!.buildId);
     });
 
     it("compiles every module to bytecode when qjsc-kmp is available", { skip: !process.env["TINYUI_QJSC"] && "TINYUI_QJSC not set" }, async () => {
diff --git a/packages/core/src/host.ts b/packages/core/src/host.ts
index 2655fce..c6481f6 100644
--- a/packages/core/src/host.ts
+++ b/packages/core/src/host.ts
@@ -8,6 +8,8 @@ declare const __host_report: (kind: string, detailJson: string) => void;
 interface Pending {
     resolve: (value: unknown) => void;
     reject: (error: HostError) => void;
+    /** Stack at the J3 call: a rejection's own stack would only show the K3 entry. */
+    site?: string;
 }
 
 export class HostError extends Error {
@@ -33,8 +35,9 @@ export function query<T>(name: string, args: Record<string, unknown> = {}): T {
 /** J3: asynchronous capability; settles when the host calls K3. */
 export function call<T>(name: string, args: Record<string, unknown> = {}): Promise<T> {
     const cbId = nextCbId++;
+    const site = new Error().stack;
     return new Promise<T>((resolve, reject) => {
-        pending.set(cbId, { resolve: resolve as (v: unknown) => void, reject });
+        pending.set(cbId, { resolve: resolve as (v: unknown) => void, reject, ...(site !== undefined && { site }) });
         __host_call(name, cbId, JSON.stringify(args));
     });
 }
@@ -72,7 +75,9 @@ export function rejectPending(cbId: number, errorJson: string): void {
     } catch {
         e = { code: "E_BAD_JSON", message: errorJson };
     }
-    p.reject(new HostError(e.code ?? "unknown", e.message ?? "host call failed"));
+    const error = new HostError(e.code ?? "unknown", e.message ?? "host call failed");
+    if (p.site !== undefined) error.stack = p.site;
+    p.reject(error);
 }
 
 export function cancelPending(cbId: number): void {
diff --git a/packages/core/test/async.test.ts b/packages/core/test/async.test.ts
index e042812..c52bf80 100644
--- a/packages/core/test/async.test.ts
+++ b/packages/core/test/async.test.ts
@@ -25,10 +25,11 @@ describe("resource + K3", () => {
         unmount();
     });
 
-    it("rejection lands in error() and is not reported", async () => {
+    it("rejection lands in error() with the call site's stack and is not reported", async () => {
+        let seen: HostError | undefined;
         mount(() => {
             const [, { error }] = resource(() => call("http.get"));
-            return h(Column, null, h(Text, { text: thunk(() => { const e = error(); return e instanceof HostError ? e.code : "ok"; }) }));
+            return h(Column, null, h(Text, { text: thunk(() => { const e = error(); if (e instanceof HostError) seen = e; return e instanceof HostError ? e.code : "ok"; }) }));
         });
         tinyui().reject(bridge.calls.at(-1)!.cbId, JSON.stringify({ code: "E_NET", message: "offline" }));
         await drain();
@@ -36,6 +37,8 @@ describe("resource + K3", () => {
         tinyui().flush();
         assert.deepEqual(bridge.applied.slice(before).flat(), [["p", 1, "text", "E_NET"]]);
         assert.equal(bridge.reports.length, 0);
+        assert.match(seen!.stack ?? "", /at resource /, "the stack is where call() happened (inside resource's fetcher)");
+        assert.doesNotMatch(seen!.stack ?? "", /rejectPending/, "not where reject() arrived");
         unmount();
     });
 
diff --git a/sample/shared/build.gradle.kts b/sample/shared/build.gradle.kts
index 108c612..01ed857 100644
--- a/sample/shared/build.gradle.kts
+++ b/sample/shared/build.gradle.kts
@@ -65,7 +65,11 @@ val buildTinyUIPages by tasks.registering(Exec::class) {
 }
 
 val collectTinyUIResources by tasks.registering(Sync::class) {
-    from(buildTinyUIPages) { include("**/*.bin", "manifest.json") }
+    // maps ride along for the debug-only failure screen (docs/build-chain.md); -Ptinyui.maps=false leaves them out
+    from(buildTinyUIPages) {
+        include("**/*.bin", "manifest.json")
+        if (providers.gradleProperty("tinyui.maps").orNull != "false") include("**/*.js.map")
+    }
     into(layout.buildDirectory.dir("tinyui-resources/files/tinyui"))
 }
 
diff --git a/sample/shared/src/commonMain/kotlin/wang/harlon/tinyui/sample/App.kt b/sample/shared/src/commonMain/kotlin/wang/harlon/tinyui/sample/App.kt
index 40e4e92..7b8ad37 100644
--- a/sample/shared/src/commonMain/kotlin/wang/harlon/tinyui/sample/App.kt
+++ b/sample/shared/src/commonMain/kotlin/wang/harlon/tinyui/sample/App.kt
@@ -15,27 +15,30 @@ import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import kotlinx.coroutines.delay
 import org.jetbrains.compose.resources.ExperimentalResourceApi
+import wang.harlon.tinyui.BuildManifest
 import wang.harlon.tinyui.HostException
 import wang.harlon.tinyui.HostServices
 import wang.harlon.tinyui.HttpClient
 import wang.harlon.tinyui.HttpRequest
 import wang.harlon.tinyui.HttpResponse
+import wang.harlon.tinyui.PageError
+import wang.harlon.tinyui.PageModule
 import wang.harlon.tinyui.PageSink
 import wang.harlon.tinyui.RuntimeBundle
+import wang.harlon.tinyui.SourceMaps
+import wang.harlon.tinyui.TinyUI
 import wang.harlon.tinyui.TinyUIPage
 import wang.harlon.tinyui.components.registerBuiltins
-import wang.harlon.tinyui.node.PatchProblem
 import wang.harlon.tinyui.sample.res.Res
 import wang.harlon.tinyui.schema.ComponentRegistry
 
-private class Bundle(val runtime: RuntimeBundle, val page: ByteArray)
+private class Bundle(val runtime: RuntimeBundle, val page: PageModule, val maps: SourceMaps)
 
 /** App-level, built once (docs/adr-003 §3.3). */
 private val registry = ComponentRegistry().registerBuiltins()
 
 private val sink = object : PageSink {
-    override fun patchProblem(problem: PatchProblem) = println("TinyUI E5 $problem")
-    override fun businessError(entry: String, message: String, stack: String?) = println("TinyUI E1 [$entry] $message")
+    override fun error(error: PageError) = println("TinyUI $error")
     override fun log(line: String) = println("TinyUI $line")
 }
 
@@ -58,18 +61,27 @@ private val services = HostServices(http = FakeTodos, deviceInfo = mapOf("app" t
 fun App() {
     var bundle by remember { mutableStateOf<Bundle?>(null) }
     LaunchedEffect(Unit) {
+        val manifest = BuildManifest.parse(Res.readBytes("files/tinyui/manifest.json").decodeToString())
+        // debug builds ship the maps; without them (-Ptinyui.maps=false) stacks stay as the engine printed them
+        val maps = (manifest.runtime + manifest.pages).mapNotNull { name ->
+            val file = if (name.startsWith("@tiny-ui/")) "runtime/" + name.removePrefix("@tiny-ui/") else name
+            runCatching { Res.readBytes("files/tinyui/$file.js.map").decodeToString() }.getOrNull()?.let { name to it }
+        }.toMap()
+        // stacks on the failure screen only when the maps came along, i.e. the same switch as -Ptinyui.maps
+        TinyUI.debug = maps.isNotEmpty()
         bundle = Bundle(
             RuntimeBundle(
                 core = Res.readBytes("files/tinyui/runtime/core.bin"),
                 native = Res.readBytes("files/tinyui/runtime/native.bin"),
             ),
-            page = Res.readBytes("files/tinyui/pages/todos.bin"),
+            page = PageModule("pages/todos", Res.readBytes("files/tinyui/pages/todos.bin"), manifest.buildId("pages/todos")),
+            maps = SourceMaps(maps),
         )
     }
     MaterialTheme {
         Box(Modifier.fillMaxSize().safeDrawingPadding(), contentAlignment = Alignment.Center) {
             val b = bundle
-            if (b == null) Text("loading…") else TinyUIPage(b.runtime, b.page, registry, sink, services)
+            if (b == null) Text("loading…") else TinyUIPage(b.runtime, b.page, registry, sink, services, sourceMaps = b.maps)
         }
     }
 }