fix: preserve compaction files and classify Z.AI overflow (#35747)

Co-authored-by: opencode-agent[bot] <219766164+opencode-agent[bot]@users.noreply.github.com>
Co-authored-by: 冯基魁 <56265583+fengjikui@users.noreply.github.com>

packages/core/test/session-compaction.test.ts

@@ -52,6 +52,15 @@ const it = testEffect(
   ),
 )
 
+test("compaction prompt preserves detailed work state and relevant files", () => {
+  const prompt = SessionCompaction.buildPrompt({ context: ["conversation history"] })
+
+  expect(prompt).toContain("## Work State\n### Completed")
+  expect(prompt).toContain("### Active")
+  expect(prompt).toContain("### Blocked")
+  expect(prompt).toContain("## Relevant Files")
+})
+
 test("compaction describes tool media without embedding base64", () => {
   const base64 = "iVBORw0KGgoAAAANSUhEUgAAAAEAAAAB"
   const serialized = SessionCompaction.serializeToolContent([
@@ -74,13 +83,14 @@ test("compaction prompt requires the checkpoint headings in order", () => {
     "## Objective",
     "## Important Details",
     "## Work State",
+    "### Completed",
+    "### Active",
+    "### Blocked",
     "## Next Move",
+    "## Relevant Files",
   ])
   expect(prompt).toContain("one or two brief sentences")
   expect(prompt).toContain("constraints/preferences, decisions and why")
-  expect(prompt).toContain("Completed:")
-  expect(prompt).toContain("Active:")
-  expect(prompt).toContain("Blocked:")
   expect(prompt).toContain("immediate concrete action")
   expect(prompt).toContain("next action if known")
   expect(prompt).toContain("Keep every section, even when empty.")