feat: unify context compaction

pi-compaction/test/native-compaction.test.ts

@@ -0,0 +1,50 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+import {
+  buildReplacementHistory,
+  findNativeCheckpoint,
+  parseNativeCompactionDetails,
+  type NativeCompactionDetails,
+} from "../src/native-compaction.ts";
+
+const details: NativeCompactionDetails = {
+  kind: "pi-compaction",
+  version: 1,
+  checkpoint: "native",
+  modelKey: "openai-codex/openai-codex-responses/gpt-test",
+  replacementHistory: [{ type: "compaction", encrypted_content: "opaque" }],
+  portableSummary: "portable",
+  sourceFingerprint: "abc",
+};
+
+test("recognizes only the unified native checkpoint format", () => {
+  assert.deepEqual(parseNativeCompactionDetails(details), details);
+  assert.equal(parseNativeCompactionDetails({ ...details, kind: "openai-codex-native-compaction" }), undefined);
+  assert.equal(parseNativeCompactionDetails({ ...details, portableSummary: undefined }), undefined);
+});
+
+test("latest Pi compaction entry is the authoritative native checkpoint", () => {
+  const branch = [
+    { type: "message", id: "m1" },
+    { type: "compaction", id: "c1", details },
+  ] as any;
+  const found = findNativeCheckpoint(branch);
+  assert.equal(found.status, "valid");
+  if (found.status === "valid") assert.equal(found.checkpoint.entryIndex, 1);
+
+  const shadowed = findNativeCheckpoint([...branch, { type: "compaction", id: "c2", details: { kind: "other" } }] as any);
+  assert.equal(shadowed.status, "none");
+  const portable = findNativeCheckpoint([
+    ...branch,
+    { type: "compaction", id: "c3", details: { kind: "pi-compaction", version: 1, checkpoint: "portable" } },
+  ] as any);
+  assert.equal(portable.status, "none");
+});
+
+test("replacement history ends with exactly one native item", () => {
+  const history = buildReplacementHistory([
+    { role: "user", content: [{ type: "input_text", text: "recent" }] },
+  ], { type: "compaction", encrypted_content: "opaque" }, 1_000);
+  assert.equal(history.at(-1)?.type, "compaction");
+  assert.equal(history.filter((item) => item.type === "compaction").length, 1);
+});