feat(cli): causation-graph DOT export for event inspector

apps/cli/src/main/kotlin/com/correx/apps/cli/commands/EventsCommand.kt

@@ -5,6 +5,7 @@ import com.correx.apps.cli.DEFAULT_PORT
 import com.github.ajalt.clikt.core.CliktCommand
 import com.github.ajalt.clikt.parameters.arguments.argument
 import com.github.ajalt.clikt.parameters.options.default
+import com.github.ajalt.clikt.parameters.options.flag
 import com.github.ajalt.clikt.parameters.options.option
 import io.ktor.client.HttpClient
 import io.ktor.client.call.body
@@ -43,6 +44,19 @@ fun renderEventRows(rows: List<EventRow>): String {
     return (listOf(header) + lines).joinToString("\n")
 }
 
+fun renderDot(rows: List<EventRow>): String = buildString {
+    appendLine("digraph session {")
+    rows.forEach { r ->
+        appendLine(""""${r.eventId}" [label="${r.type} #${r.sequence}"]""")
+    }
+    rows.forEach { r ->
+        r.causationId?.let { causation ->
+            appendLine(""""${r.eventId}" -> "$causation"""")
+        }
+    }
+    append("}")
+}
+
 class EventsCommand : CliktCommand(name = "events") {
     private val sessionId by argument("sessionId")
     private val type by option("--type")
@@ -50,6 +64,7 @@ class EventsCommand : CliktCommand(name = "events") {
     private val limit by option("--limit")
     private val host by option("--host").default("localhost")
     private val port by option("--port").default("$DEFAULT_PORT")
+    private val dot by option("--dot").flag()
 
     private val eventsJson = Json { ignoreUnknownKeys = true }
 
@@ -71,10 +86,10 @@ class EventsCommand : CliktCommand(name = "events") {
 
         runCatching {
             val rows = client.get(url).body<List<EventRow>>()
-            if (outputJson) {
-                println(eventsJson.encodeToString(ListSerializer(EventRow.serializer()), rows))
-            } else {
-                println(renderEventRows(rows))
+            when {
+                dot -> println(renderDot(rows))
+                outputJson -> println(eventsJson.encodeToString(ListSerializer(EventRow.serializer()), rows))
+                else -> println(renderEventRows(rows))
             }
         }.getOrElse { e ->
             System.err.println("Error fetching events: ${e.message}")

apps/cli/src/test/kotlin/com/correx/apps/cli/commands/EventRenderTest.kt

@@ -61,4 +61,87 @@ class EventRenderTest {
         val output = renderEventRows(emptyList())
         assertTrue(output.contains("no events"))
     }
+
+    @Test
+    fun `renderDot generates correct node lines for all events`() {
+        val testRows = listOf(
+            EventRow(
+                sequence = 1L,
+                eventId = "e1",
+                type = "WorkspaceStateObserved",
+                timestamp = "2026-06-12T10:00:00Z",
+                causationId = null,
+                correlationId = null,
+                payload = JsonObject(emptyMap()),
+            ),
+            EventRow(
+                sequence = 2L,
+                eventId = "e2",
+                type = "InitialIntent",
+                timestamp = "2026-06-12T10:01:00Z",
+                causationId = "e1",
+                correlationId = null,
+                payload = JsonObject(emptyMap()),
+            ),
+            EventRow(
+                sequence = 3L,
+                eventId = "e3",
+                type = "SomeEvent",
+                timestamp = "2026-06-12T10:02:00Z",
+                causationId = null,
+                correlationId = null,
+                payload = JsonObject(emptyMap()),
+            ),
+        )
+        val output = renderDot(testRows)
+
+        // Check structure
+        assertTrue(output.startsWith("digraph session {"), "Output should start with digraph session {")
+        assertTrue(output.endsWith("}"), "Output should end with }")
+
+        // Check node lines with labels (eventId and type #sequence)
+        assertTrue(output.contains(""""e1" [label="WorkspaceStateObserved #1"]"""), "Should contain e1 node with label")
+        assertTrue(output.contains(""""e2" [label="InitialIntent #2"]"""), "Should contain e2 node with label")
+        assertTrue(output.contains(""""e3" [label="SomeEvent #3"]"""), "Should contain e3 node with label")
+
+        // Check edge for e2 -> e1 (causation)
+        assertTrue(output.contains(""""e2" -> "e1""""), "Should contain edge from e2 to its causation e1")
+
+        // Check that e1 and e3 (with null causation) don't have outgoing edges
+        assertTrue(!output.contains(""""e1" -> """"), "e1 should not have outgoing edge (no causation)")
+        assertTrue(!output.contains(""""e3" -> """"), "e3 should not have outgoing edge (no causation)")
+    }
+
+    @Test
+    fun `renderDot returns empty digraph for no events`() {
+        val output = renderDot(emptyList())
+        assertTrue(output.startsWith("digraph session {"), "Should start with digraph session {")
+        assertTrue(output.endsWith("}"), "Should end with }")
+    }
+
+    @Test
+    fun `renderDot handles events with causationId matching eventId`() {
+        val testRows = listOf(
+            EventRow(
+                sequence = 1L,
+                eventId = "e1",
+                type = "Event1",
+                timestamp = "2026-06-12T10:00:00Z",
+                causationId = null,
+                correlationId = null,
+                payload = JsonObject(emptyMap()),
+            ),
+            EventRow(
+                sequence = 2L,
+                eventId = "e2",
+                type = "Event2",
+                timestamp = "2026-06-12T10:01:00Z",
+                causationId = "e1",
+                correlationId = null,
+                payload = JsonObject(emptyMap()),
+            ),
+        )
+        val output = renderDot(testRows)
+        assertTrue(output.contains(""""e2" -> "e1""""), "Should correctly reference causation by ID")
+    }
 }