fix: filter heartbeat pairs before context shaping

src/agents/pi-embedded-runner/run/attempt.spawn-workspace.context-injection.test.ts

@@ -1,4 +1,7 @@
-import { afterEach, beforeEach, describe, expect, it } from "vitest";
+import type { AgentMessage } from "@mariozechner/pi-agent-core";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import { HEARTBEAT_PROMPT } from "../../../auto-reply/heartbeat.js";
+import { limitHistoryTurns } from "../history.js";
 import {
   cleanupTempPaths,
   createContextEngineAttemptRunner,
@@ -130,4 +133,42 @@ describe("runEmbeddedAttempt context injection", () => {
       expect.anything(),
     );
   });
+
+  it("filters no-op heartbeat pairs before history limiting and context-engine assembly", async () => {
+    hoisted.getDmHistoryLimitFromSessionKeyMock.mockReturnValue(1);
+    hoisted.limitHistoryTurnsMock.mockImplementation(limitHistoryTurns);
+    const assemble = vi.fn(async ({ messages }: { messages: AgentMessage[] }) => ({
+      messages,
+      estimatedTokens: 1,
+    }));
+    const sessionMessages: AgentMessage[] = [
+      { role: "user", content: "real question", timestamp: 1 } as AgentMessage,
+      { role: "assistant", content: "real answer", timestamp: 2 } as AgentMessage,
+      { role: "user", content: HEARTBEAT_PROMPT, timestamp: 3 } as AgentMessage,
+      { role: "assistant", content: "HEARTBEAT_OK", timestamp: 4 } as AgentMessage,
+    ];
+
+    await createContextEngineAttemptRunner({
+      contextEngine: { assemble },
+      attemptOverrides: {
+        config: {
+          agents: {
+            list: [{ id: "main", heartbeat: {} }],
+          },
+        },
+      },
+      sessionKey: "agent:main:discord:dm:test-user",
+      sessionMessages,
+      tempPaths,
+    });
+
+    expect(assemble).toHaveBeenCalledWith(
+      expect.objectContaining({
+        messages: [
+          expect.objectContaining({ role: "user", content: "real question" }),
+          expect.objectContaining({ role: "assistant", content: "real answer" }),
+        ],
+      }),
+    );
+  });
 });

src/agents/pi-embedded-runner/run/attempt.spawn-workspace.test-support.ts

@@ -53,6 +53,10 @@ type AttemptSpawnWorkspaceHoisted = {
   getGlobalHookRunnerMock: Mock<() => unknown>;
   initializeGlobalHookRunnerMock: UnknownMock;
   runContextEngineMaintenanceMock: AsyncUnknownMock;
+  getDmHistoryLimitFromSessionKeyMock: Mock<
+    (sessionKey: string | undefined, config: unknown) => number | undefined
+  >;
+  limitHistoryTurnsMock: Mock<<T>(messages: T, limit: number | undefined) => T>;
   sessionManager: SessionManagerMocks;
 };
 
@@ -99,6 +103,12 @@ const hoisted = vi.hoisted((): AttemptSpawnWorkspaceHoisted => {
   const getGlobalHookRunnerMock = vi.fn<() => unknown>(() => undefined);
   const initializeGlobalHookRunnerMock = vi.fn();
   const runContextEngineMaintenanceMock = vi.fn(async (_params?: unknown) => undefined);
+  const getDmHistoryLimitFromSessionKeyMock = vi.fn<
+    (sessionKey: string | undefined, config: unknown) => number | undefined
+  >(() => undefined);
+  const limitHistoryTurnsMock = vi.fn<<T>(messages: T, limit: number | undefined) => T>(
+    (messages) => messages,
+  );
   const sessionManager = {
     getLeafEntry: vi.fn(() => null),
     branch: vi.fn(),
@@ -124,6 +134,8 @@ const hoisted = vi.hoisted((): AttemptSpawnWorkspaceHoisted => {
     getGlobalHookRunnerMock,
     initializeGlobalHookRunnerMock,
     runContextEngineMaintenanceMock,
+    getDmHistoryLimitFromSessionKeyMock,
+    limitHistoryTurnsMock,
     sessionManager,
   };
 });
@@ -430,8 +442,10 @@ vi.mock("../compaction-safety-timeout.js", () => ({
 }));
 
 vi.mock("../history.js", () => ({
-  getDmHistoryLimitFromSessionKey: () => undefined,
-  limitHistoryTurns: <T>(messages: T) => messages,
+  getDmHistoryLimitFromSessionKey: (sessionKey: string | undefined, config: unknown) =>
+    hoisted.getDmHistoryLimitFromSessionKeyMock(sessionKey, config),
+  limitHistoryTurns: <T>(messages: T, limit: number | undefined) =>
+    hoisted.limitHistoryTurnsMock(messages, limit),
 }));
 
 vi.mock("../logger.js", () => ({
@@ -599,6 +613,8 @@ export function resetEmbeddedAttemptHarness(
   hoisted.hasCompletedBootstrapTurnMock.mockReset().mockResolvedValue(false);
   hoisted.getGlobalHookRunnerMock.mockReset().mockReturnValue(undefined);
   hoisted.runContextEngineMaintenanceMock.mockReset().mockResolvedValue(undefined);
+  hoisted.getDmHistoryLimitFromSessionKeyMock.mockReset().mockReturnValue(undefined);
+  hoisted.limitHistoryTurnsMock.mockReset().mockImplementation((messages) => messages);
   hoisted.sessionManager.getLeafEntry.mockReset().mockReturnValue(null);
   hoisted.sessionManager.branch.mockReset();
   hoisted.sessionManager.resetLeaf.mockReset();
@@ -755,6 +771,7 @@ export async function createContextEngineAttemptRunner(params: {
     info?: Partial<ContextEngineInfo>;
   };
   attemptOverrides?: Partial<Parameters<Awaited<ReturnType<typeof loadRunEmbeddedAttempt>>>[0]>;
+  sessionMessages?: AgentMessage[];
   sessionKey: string;
   tempPaths: string[];
 }) {
@@ -764,9 +781,8 @@ export async function createContextEngineAttemptRunner(params: {
   const sessionFile = path.join(workspaceDir, "session.jsonl");
   params.tempPaths.push(workspaceDir, agentDir);
   await fs.writeFile(sessionFile, "", "utf8");
-  const seedMessages: AgentMessage[] = [
-    { role: "user", content: "seed", timestamp: 1 } as AgentMessage,
-  ];
+  const seedMessages: AgentMessage[] =
+    params.sessionMessages ?? ([{ role: "user", content: "seed", timestamp: 1 }] as AgentMessage[]);
   const infoId = params.contextEngine.info?.id ?? "test-context-engine";
   const infoName = params.contextEngine.info?.name ?? "Test Context Engine";
   const infoVersion = params.contextEngine.info?.version ?? "0.0.1";

src/agents/pi-embedded-runner/run/attempt.ts

@@ -1217,8 +1217,17 @@ export async function runEmbeddedAttempt(
           sessionId: params.sessionId,
           policy: transcriptPolicy,
         });
-        const truncated = limitHistoryTurns(
+        const heartbeatSummary =
+          params.config && sessionAgentId
+            ? resolveHeartbeatSummaryForAgent(params.config, sessionAgentId)
+            : undefined;
+        const heartbeatFiltered = filterHeartbeatPairs(
           validated,
+          heartbeatSummary?.ackMaxChars,
+          heartbeatSummary?.prompt,
+        );
+        const truncated = limitHistoryTurns(
+          heartbeatFiltered,
           getDmHistoryLimitFromSessionKey(params.sessionKey, params.config),
         );
         // Re-run tool_use/tool_result pairing repair after truncation, since
@@ -1667,10 +1676,6 @@ export async function runEmbeddedAttempt(
             activeSession.agent.state.messages = activeSession.messages;
           }
 
-          const heartbeatSummary =
-            params.config && sessionAgentId
-              ? resolveHeartbeatSummaryForAgent(params.config, sessionAgentId)
-              : undefined;
           const filteredMessages = filterHeartbeatPairs(
             activeSession.messages,
             heartbeatSummary?.ackMaxChars,