fix(harness): retain useful continuation parts before placeholders [SAP-3292]

.changeset/assistant-useful-brief-parts.md

@@ -0,0 +1,5 @@
+---
+"@sapiom/harness": patch
+---
+
+Use the same usefulness predicate for part selection and message reduction. Preserve the latest useful text/tool/file parts and report all omitted parts without claiming they were necessarily earlier.

packages/harness/docs/assistant-history.md

@@ -185,3 +185,7 @@ the exact previous revision; compacted tasks and recorded real replies remain.
 A failed Terminal binding publication can roll back only its original close
 generation and exact proposed marker. A queued End retains its durable tombstone
 or confirmed removal, and other sessions keep their own process and binding.
+
+Brief part selection keeps the latest useful Assistant text, tool results and
+attachments even when blank or omitted control parts follow them. Omission counts
+remain explicit without incorrectly labeling every removed part as earlier.

packages/harness/src/core/assistant-continuation-brief.test.ts

@@ -122,7 +122,7 @@ it("reserves user context and the newest Assistant parts when both messages are
   expect(frozen.text).toContain("excerpt truncated");
   expect(frozen.text).toContain("assistant state 12:");
   expect(frozen.text).not.toContain("assistant state 0:");
-  expect(frozen.text).toContain("1 earlier parts omitted.");
+  expect(frozen.text).toContain("1 part omitted.");
   expect(frozen.text).toContain("incomplete; do not assume success");
 });
 it("keeps the newest useful Assistant state ahead of later empty native messages", () => {
@@ -170,3 +170,72 @@ it("fails without usable public history or with corrupt binding metadata", () =>
     }),
   ).toThrow();
 });
+
+it.each(["blank", "omitted", "mixed"])(
+  "keeps the latest useful text, tool and attachment before thirteen %s parts",
+  (kind) => {
+    const record = fixture();
+    record.turns[0]!.messages.push({
+      id: "msg_state",
+      role: "assistant",
+      parentId: "msg_user_0",
+      createdAt: 2,
+      completedAt: 3,
+      parts: [
+        {
+          id: "prt_state",
+          type: "text",
+          text: "Latest result: tests pass; deployment pending.",
+          truncated: false,
+        },
+        {
+          id: "prt_tool",
+          type: "tool",
+          callId: "call_verify",
+          name: "test",
+          status: "completed",
+          input: "{}",
+          output: "12 tests passed",
+          error: null,
+          startedAt: 2,
+          completedAt: 3,
+          truncated: false,
+        },
+        {
+          id: "prt_file",
+          type: "file",
+          name: "test-report.txt",
+          mime: "text/plain",
+        },
+        ...Array.from({ length: 13 }, (_, index) =>
+          kind === "omitted" || (kind === "mixed" && index % 2 === 0)
+            ? {
+                id: `prt_empty_${index}`,
+                type: "omitted" as const,
+                nativeType: "step-finish",
+              }
+            : {
+                id: `prt_empty_${index}`,
+                type: "text" as const,
+                text: " \n\t ",
+                truncated: false,
+              },
+        ),
+      ],
+    });
+    record.messageCount = 2;
+    const frozen = buildAssistantContinuationBrief(record);
+    expect(frozen.text).toContain(
+      "Latest result: tests pass; deployment pending.",
+    );
+    expect(frozen.text).toContain("Recorded tool test (completed)");
+    expect(frozen.text).toContain("12 tests passed");
+    expect(frozen.text).toContain(
+      "Attachment test-report.txt (text/plain); contents omitted.",
+    );
+    expect(frozen.text).toContain("13 parts omitted.");
+    expect(frozen.text).not.toContain("earlier parts omitted");
+    expect(frozen.estimatedTokens).toBeLessThanOrEqual(6000);
+    expect(frozen).toEqual(buildAssistantContinuationBrief(record));
+  },
+);

packages/harness/src/core/assistant-continuation-brief.ts

@@ -2,6 +2,7 @@ import { createHash } from "node:crypto";
 import type {
   AssistantRecord,
   AssistantRecordBinding,
+  AssistantRecordPart,
 } from "../shared/assistant-record.js";
 import { validateAssistantRecord } from "./assistant-record.js";
 import {
@@ -25,6 +26,9 @@ const clamp = (value: string, limit: number) =>
   value.length <= limit
     ? value
     : `${value.slice(0, limit)}… [excerpt truncated]`;
+const usefulPart = (part: AssistantRecordPart) =>
+  part.type !== "omitted" &&
+  (part.type !== "text" || part.text.trim().length > 0);
 
 /** Freeze a bounded public reconstruction. It carries context, never an instruction to replay work. */
 export function buildAssistantContinuationBrief(
@@ -45,7 +49,7 @@ export function buildAssistantContinuationBrief(
       const messages = turn.messages.map((message) => {
         const selected =
           message.role === "assistant"
-            ? message.parts.slice(-12)
+            ? message.parts.filter(usefulPart).slice(-12)
             : message.parts.slice(0, 12);
         const parts = selected.map((part) => {
           switch (part.type) {
@@ -59,18 +63,15 @@ export function buildAssistantContinuationBrief(
               return `Omitted ${part.nativeType} part.`;
           }
         });
-        if (message.parts.length > 12) {
-          const omitted = `${message.parts.length - 12} ${message.role === "assistant" ? "earlier" : "further"} parts omitted.`;
+        if (message.parts.length > selected.length) {
+          const count = message.parts.length - selected.length;
+          const omitted = `${count} ${message.role === "assistant" ? "" : "further "}part${count === 1 ? "" : "s"} omitted.`;
           if (message.role === "assistant") parts.unshift(omitted);
           else parts.push(omitted);
         }
         return {
           text: `${message.role === "user" ? "User" : "Assistant"} ${message.id}:\n${parts.join("\n")}`,
-          useful: message.parts.some(
-            (part) =>
-              part.type !== "omitted" &&
-              (part.type !== "text" || part.text.trim().length > 0),
-          ),
+          useful: selected.some(usefulPart),
         };
       });
       return {