diff --git a/java/com/google/turbine/binder/Processing.java b/java/com/google/turbine/binder/Processing.java
index 984dee66..0c24d2eb 100644
--- a/java/com/google/turbine/binder/Processing.java
+++ b/java/com/google/turbine/binder/Processing.java
@@ -21,7 +21,6 @@
 import com.google.auto.value.AutoValue;
 import com.google.common.base.Joiner;
 import com.google.common.base.Stopwatch;
-import com.google.common.base.Throwables;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
@@ -296,9 +295,8 @@ static SupportedAnnotationTypes create(Processor processor) {
   private static void logProcessorCrash(TurbineLog log, Processor processor, Throwable t) {
     log.diagnostic(
         Diagnostic.Kind.ERROR,
-        String.format(
-            "An exception occurred in %s:\n%s",
-            processor.getClass().getCanonicalName(), Throwables.getStackTraceAsString(t)));
+        String.format("An exception occurred in %s:", processor.getClass().getCanonicalName()),
+        t);
   }
 
   /** Returns a map from annotations present in the compilation to the annotated elements. */
diff --git a/java/com/google/turbine/diag/TurbineDiagnostic.java b/java/com/google/turbine/diag/TurbineDiagnostic.java
index c47cbebf..06369282 100644
--- a/java/com/google/turbine/diag/TurbineDiagnostic.java
+++ b/java/com/google/turbine/diag/TurbineDiagnostic.java
@@ -21,6 +21,7 @@
 import static java.util.Objects.requireNonNull;
 
 import com.google.common.base.CharMatcher;
+import com.google.common.base.Throwables;
 import com.google.common.collect.ImmutableList;
 import com.google.turbine.binder.sym.ClassSymbol;
 import com.google.turbine.diag.TurbineError.ErrorKind;
@@ -37,18 +38,21 @@ public class TurbineDiagnostic {
   private final ImmutableList<Object> args;
   private final @Nullable SourceFile source;
   private final int position;
+  private final @Nullable Throwable cause;
 
   private TurbineDiagnostic(
       Diagnostic.Kind severity,
       ErrorKind kind,
       ImmutableList<Object> args,
       @Nullable SourceFile source,
-      int position) {
+      int position,
+      @Nullable Throwable cause) {
     this.severity = requireNonNull(severity);
     this.kind = requireNonNull(kind);
     this.args = requireNonNull(args);
     this.source = source;
     this.position = position;
+    this.cause = cause;
   }
 
   /** The diagnostic kind. */
@@ -85,6 +89,9 @@ public String diagnostic() {
       sb.append(": ").append(severity);
     }
     sb.append(": ").append(message());
+    if (cause != null) {
+      sb.append(System.lineSeparator()).append(Throwables.getStackTraceAsString(cause));
+    }
     if (position != -1) {
       sb.append(System.lineSeparator());
       sb.append(lineSource());
@@ -104,7 +111,8 @@ private static TurbineDiagnostic create(
       ErrorKind kind,
       ImmutableList<Object> args,
       SourceFile source,
-      int position) {
+      int position,
+      @Nullable Throwable cause) {
     switch (kind) {
       case SYMBOL_NOT_FOUND ->
           checkArgument(
@@ -114,13 +122,31 @@ private static TurbineDiagnostic create(
               args);
       default -> {}
     }
-    return new TurbineDiagnostic(severity, kind, args, source, position);
+    return new TurbineDiagnostic(severity, kind, args, source, position, cause);
+  }
+
+  private static TurbineDiagnostic create(
+      Diagnostic.Kind severity,
+      ErrorKind kind,
+      ImmutableList<Object> args,
+      SourceFile source,
+      int position) {
+    return create(severity, kind, args, source, position, null);
+  }
+
+  public @Nullable Throwable cause() {
+    return cause;
   }
 
   public static TurbineDiagnostic format(Diagnostic.Kind severity, ErrorKind kind, String message) {
     return create(severity, kind, ImmutableList.of(message), null, -1);
   }
 
+  public static TurbineDiagnostic format(
+      Diagnostic.Kind severity, ErrorKind kind, String message, Throwable cause) {
+    return create(severity, kind, ImmutableList.of(message), null, -1, cause);
+  }
+
   public static TurbineDiagnostic format(Diagnostic.Kind severity, ErrorKind kind) {
     return create(severity, kind, ImmutableList.of(), null, -1);
   }
@@ -149,7 +175,7 @@ public static TurbineDiagnostic format(
   }
 
   public TurbineDiagnostic withPosition(SourceFile source, int position) {
-    return new TurbineDiagnostic(severity, kind, args, source, position);
+    return new TurbineDiagnostic(severity, kind, args, source, position, cause);
   }
 
   @Override
diff --git a/java/com/google/turbine/diag/TurbineLog.java b/java/com/google/turbine/diag/TurbineLog.java
index 46e41ab4..2af0a970 100644
--- a/java/com/google/turbine/diag/TurbineLog.java
+++ b/java/com/google/turbine/diag/TurbineLog.java
@@ -98,6 +98,13 @@ public void diagnostic(Diagnostic.Kind severity, String message) {
     add(TurbineDiagnostic.format(severity, ErrorKind.PROC, message));
   }
 
+  /**
+   * Reports an annotation processing diagnostic with no position information, retaining the cause.
+   */
+  public void diagnostic(Diagnostic.Kind severity, String message, Throwable t) {
+    add(TurbineDiagnostic.format(severity, ErrorKind.PROC, message, t));
+  }
+
   public void add(TurbineDiagnostic diagnostic) {
     synchronized (lock) {
       diagnostics.add(diagnostic);
diff --git a/javatests/com/google/turbine/processing/ProcessingIntegrationTest.java b/javatests/com/google/turbine/processing/ProcessingIntegrationTest.java
index a4802f3f..34bdeb57 100644
--- a/javatests/com/google/turbine/processing/ProcessingIntegrationTest.java
+++ b/javatests/com/google/turbine/processing/ProcessingIntegrationTest.java
@@ -125,7 +125,11 @@ public void crash() throws IOException {
         e.diagnostics().stream().map(TurbineDiagnostic::message).collect(toImmutableList());
     assertThat(messages).hasSize(2);
     assertThat(messages.getFirst()).contains("could not resolve NoSuch");
-    assertThat(messages.get(1)).contains("crash!");
+    assertThat(messages.get(1))
+        .contains(
+            "An exception occurred in"
+                + " com.google.turbine.processing.ProcessingIntegrationTest.CrashingProcessor:");
+    assertThat(e.diagnostics().get(1).cause()).hasMessageThat().contains("crash!");
   }
 
   @SupportedAnnotationTypes("*")