Compaction: sanitize token split accounting (#24058)

* Compaction: sanitize token split accounting

* Tests/Compaction: type sanitize token estimate callback

src/agents/compaction.token-sanitize.test.ts

@@ -0,0 +1,52 @@
+import type { AgentMessage } from "@mariozechner/pi-agent-core";
+import { describe, expect, it, vi } from "vitest";
+
+const piCodingAgentMocks = vi.hoisted(() => ({
+  estimateTokens: vi.fn((_message: unknown) => 1),
+  generateSummary: vi.fn(async () => "summary"),
+}));
+
+vi.mock("@mariozechner/pi-coding-agent", async () => {
+  const actual = await vi.importActual<typeof import("@mariozechner/pi-coding-agent")>(
+    "@mariozechner/pi-coding-agent",
+  );
+  return {
+    ...actual,
+    estimateTokens: piCodingAgentMocks.estimateTokens,
+    generateSummary: piCodingAgentMocks.generateSummary,
+  };
+});
+
+import { chunkMessagesByMaxTokens, splitMessagesByTokenShare } from "./compaction.js";
+
+describe("compaction token accounting sanitization", () => {
+  it("does not pass toolResult.details into per-message token estimates", () => {
+    const messages: AgentMessage[] = [
+      {
+        role: "toolResult",
+        toolCallId: "call_1",
+        toolName: "browser",
+        isError: false,
+        content: [{ type: "text", text: "ok" }],
+        details: { raw: "x".repeat(50_000) },
+        timestamp: 1,
+        // oxlint-disable-next-line typescript/no-explicit-any
+      } as any,
+      {
+        role: "user",
+        content: "next",
+        timestamp: 2,
+      },
+    ];
+
+    splitMessagesByTokenShare(messages, 2);
+    chunkMessagesByMaxTokens(messages, 16);
+
+    const calledWithDetails = piCodingAgentMocks.estimateTokens.mock.calls.some((call) => {
+      const message = call[0] as { details?: unknown } | undefined;
+      return Boolean(message?.details);
+    });
+
+    expect(calledWithDetails).toBe(false);
+  });
+});