agents: reduce prompt token bloat from exec and context (#16539)

Merged via /review-pr -> /prepare-pr -> /merge-pr.

Prepared head SHA: 8e1635fa3f
Co-authored-by: CharlieGreenman <8540141+CharlieGreenman@users.noreply.github.com>
Co-authored-by: gumadeiras <5599352+gumadeiras@users.noreply.github.com>
Reviewed-by: @gumadeiras

src/gateway/server-node-events.test.ts

@@ -83,6 +83,42 @@ describe("node exec events", () => {
     expect(requestHeartbeatNowMock).toHaveBeenCalledWith({ reason: "exec-event" });
   });
 
+  it("suppresses noisy exec.finished success events with empty output", async () => {
+    const ctx = buildCtx();
+    await handleNodeEvent(ctx, "node-2", {
+      event: "exec.finished",
+      payloadJSON: JSON.stringify({
+        runId: "run-quiet",
+        exitCode: 0,
+        timedOut: false,
+        output: "   ",
+      }),
+    });
+
+    expect(enqueueSystemEventMock).not.toHaveBeenCalled();
+    expect(requestHeartbeatNowMock).not.toHaveBeenCalled();
+  });
+
+  it("truncates long exec.finished output in system events", async () => {
+    const ctx = buildCtx();
+    await handleNodeEvent(ctx, "node-2", {
+      event: "exec.finished",
+      payloadJSON: JSON.stringify({
+        runId: "run-long",
+        exitCode: 0,
+        timedOut: false,
+        output: "x".repeat(600),
+      }),
+    });
+
+    const [[text]] = enqueueSystemEventMock.mock.calls;
+    expect(typeof text).toBe("string");
+    expect(text.startsWith("Exec finished (node=node-2 id=run-long, code 0)\n")).toBe(true);
+    expect(text.endsWith("…")).toBe(true);
+    expect(text.length).toBeLessThan(280);
+    expect(requestHeartbeatNowMock).toHaveBeenCalledWith({ reason: "exec-event" });
+  });
+
   it("enqueues exec.denied events with reason", async () => {
     const ctx = buildCtx();
     await handleNodeEvent(ctx, "node-3", {

src/gateway/server-node-events.ts

@@ -15,6 +15,20 @@ import {
 } from "./session-utils.js";
 import { formatForLog } from "./ws-log.js";
 
+const MAX_EXEC_EVENT_OUTPUT_CHARS = 180;
+
+function compactExecEventOutput(raw: string) {
+  const normalized = raw.replace(/\s+/g, " ").trim();
+  if (!normalized) {
+    return "";
+  }
+  if (normalized.length <= MAX_EXEC_EVENT_OUTPUT_CHARS) {
+    return normalized;
+  }
+  const safe = Math.max(1, MAX_EXEC_EVENT_OUTPUT_CHARS - 1);
+  return `${normalized.slice(0, safe)}…`;
+}
+
 export const handleNodeEvent = async (ctx: NodeEventContext, nodeId: string, evt: NodeEvent) => {
   switch (evt.event) {
     case "voice.transcript": {
@@ -244,9 +258,14 @@ export const handleNodeEvent = async (ctx: NodeEventContext, nodeId: string, evt
         }
       } else if (evt.event === "exec.finished") {
         const exitLabel = timedOut ? "timeout" : `code ${exitCode ?? "?"}`;
+        const compactOutput = compactExecEventOutput(output);
+        const shouldNotify = timedOut || exitCode !== 0 || compactOutput.length > 0;
+        if (!shouldNotify) {
+          return;
+        }
         text = `Exec finished (node=${nodeId}${runId ? ` id=${runId}` : ""}, ${exitLabel})`;
-        if (output) {
-          text += `\n${output}`;
+        if (compactOutput) {
+          text += `\n${compactOutput}`;
         }
       } else {
         text = `Exec denied (node=${nodeId}${runId ? ` id=${runId}` : ""}${reason ? `, ${reason}` : ""})`;