fix(web): render prompt.completed in stage Transcript

Prompt-shape stages (prompt, fan_in) only emit `prompt.completed` for
their response, so the Transcript tab showed the input but never the
output. Add the event to STAGE_ACTIVITY_EVENT_TYPES and to the
eventsToActivity reducer, suppressing it when a prior agent.message
already streamed the same content (agent stages).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/fabro-web/app/lib/run-events.ts

@@ -64,6 +64,7 @@ const STAGE_EVENTS = new Set([
 // to run-scoped invalidations (stages list, graph, detail).
 export const STAGE_ACTIVITY_EVENT_TYPES = [
   "stage.prompt",
+  "prompt.completed",
   "agent.message",
   "agent.tool.started",
   "agent.tool.completed",

apps/fabro-web/app/routes/run-stages.test.ts

@@ -226,6 +226,116 @@ describe("eventsToActivity", () => {
     ]);
   });
 
+  test("renders prompt.completed as an assistant turn for prompt-shape stages", () => {
+    const events: EventEnvelope[] = [
+      envelope(1, {
+        event: "stage.prompt",
+        stage_id: "summarize@1",
+        node_id: "summarize",
+        properties: { text: "summarize the diff" },
+      }),
+      envelope(2, {
+        event: "prompt.completed",
+        stage_id: "summarize@1",
+        node_id: "summarize",
+        properties: {
+          response: "Refactored auth module",
+          model: "claude-sonnet-4-6",
+          provider: "anthropic",
+          billing: { input_tokens: 120, output_tokens: 30 },
+        },
+      }),
+    ];
+
+    expect(eventsToActivity(events, "summarize@1")).toEqual([
+      {
+        kind: "system",
+        ts: "2026-04-09T12:00:00Z",
+        content: "summarize the diff",
+      },
+      {
+        kind: "assistant",
+        ts: "2026-04-09T12:00:00Z",
+        content: "Refactored auth module",
+        inputTokens: 120,
+        outputTokens: 30,
+      },
+    ]);
+  });
+
+  test("does not duplicate the assistant turn when prompt.completed follows agent.message", () => {
+    const events: EventEnvelope[] = [
+      envelope(1, {
+        event: "stage.prompt",
+        stage_id: "simplify@1",
+        node_id: "simplify",
+        properties: { text: "simplify" },
+      }),
+      envelope(2, {
+        event: "agent.message",
+        stage_id: "simplify@1",
+        node_id: "simplify",
+        properties: {
+          text: "Done.",
+          billing: { input_tokens: 10, output_tokens: 5 },
+        },
+      }),
+      envelope(3, {
+        event: "prompt.completed",
+        stage_id: "simplify@1",
+        node_id: "simplify",
+        properties: {
+          response: "Done.",
+          model: "claude-sonnet-4-6",
+          provider: "anthropic",
+          billing: { input_tokens: 10, output_tokens: 5 },
+        },
+      }),
+    ];
+
+    const turns = eventsToActivity(events, "simplify@1");
+    expect(turns).toEqual([
+      {
+        kind: "system",
+        ts: "2026-04-09T12:00:00Z",
+        content: "simplify",
+      },
+      {
+        kind: "assistant",
+        ts: "2026-04-09T12:00:00Z",
+        content: "Done.",
+        inputTokens: 10,
+        outputTokens: 5,
+      },
+    ]);
+  });
+
+  test("renders prompt.completed even with no preceding stage.prompt", () => {
+    const events: EventEnvelope[] = [
+      envelope(1, {
+        event: "prompt.completed",
+        stage_id: "summarize@1",
+        node_id: "summarize",
+        properties: {
+          response: "All clear.",
+          model: "claude-sonnet-4-6",
+          provider: "anthropic",
+          billing: { input_tokens: 0, output_tokens: 4 },
+        },
+      }),
+    ];
+
+    expect(eventsToActivity(events, "summarize@1")).toEqual([
+      {
+        kind: "assistant",
+        ts: "2026-04-09T12:00:00Z",
+        content: "All clear.",
+        inputTokens: 0,
+        outputTokens: 4,
+      },
+    ]);
+  });
+
   test("extractStageModel pulls model from agent.session.activated, ignoring other stages", () => {
     const events: EventEnvelope[] = [
       envelope(1, {

apps/fabro-web/app/routes/run-stages.tsx

@@ -111,6 +111,7 @@ export function eventsToActivity(events: EventEnvelope[], stageId: string): Turn
   const turns: TurnType[] = [];
   const pendingTools = new Map<string, PendingTool>();
   let pendingCommand: PendingCommand | undefined;
+  let sawAssistantMessage = false;
 
   for (const e of events) {
     const eventName = e.event;
@@ -128,6 +129,7 @@ export function eventsToActivity(events: EventEnvelope[], stageId: string): Turn
         turns.push({ kind: "system", ts: e.ts, content: getString(props, "text") ?? e.text ?? "" });
         break;
       case "agent.message": {
+        sawAssistantMessage = true;
         const msg = getString(props, "text") ?? e.text ?? "";
         if (msg) {
           const billing = (props.billing ?? {}) as UnknownRecord;
@@ -141,6 +143,19 @@ export function eventsToActivity(events: EventEnvelope[], stageId: string): Turn
         }
         break;
       }
+      case "prompt.completed": {
+        if (!sawAssistantMessage) {
+          const billing = (props.billing ?? {}) as UnknownRecord;
+          turns.push({
+            kind: "assistant",
+            ts: e.ts,
+            content: getString(props, "response") ?? "",
+            inputTokens: getNumber(billing, "input_tokens") ?? 0,
+            outputTokens: getNumber(billing, "output_tokens") ?? 0,
+          });
+        }
+        break;
+      }
       case "agent.steering.injected": {
         const text = getString(props, "text") ?? e.text ?? "";
         if (text) {