feat: salvage malformed compress content strings (omp#121)

package.json

@@ -60,7 +60,7 @@
 	"devDependencies": {
 		"@earendil-works/pi-coding-agent": "0.83.0",
 		"@types/node": "^26.1.2",
-		"acp-kernel": "0.0.32",
+		"acp-kernel": "file:../acp-kernel/acp-kernel-0.0.33.tgz",
 		"billion-context-kit": "0.2.0",
 		"tsup": "^8.5.1",
 		"tsx": "^4.23.1",

src/compress-tool.ts

@@ -7,7 +7,7 @@ import type {
 import type { AcpRuntime } from "./runtime.js";
 import { debug, logError, logInfo, logThrow, logWarn } from "./log.js";
 import { estimateTokens, collectCoveredMessageIds, calibrateTokens } from "./tokens.js";
-import { defaultCountTokens, type CompressionBlock } from "acp-kernel";
+import { defaultCountTokens, salvageParseRanges, type CompressionBlock } from "acp-kernel";
 import { getSystemPromptText } from "./compat.js";
 
 function formatK(n: number): string {
@@ -78,6 +78,20 @@ function normalizeRanges(content: CompressArgs["content"]): RangeEntry[] | strin
     try {
       ranges = JSON.parse(ranges);
     } catch (e) {
+      // Weak/local models emit truncated or malformed JSON here ~50% of the
+      // time (see billion-context-omp#121). Before giving up, run the kernel's
+      // salvage ladder (fences / comma+newline repairs / truncated-array
+      // prefix / field-regex). Recovered entries proceed as normal ranges.
+      const sal = salvageParseRanges(ranges as string);
+      logWarn("compress", {
+        event: "content-salvage",
+        layer: sal.layer,
+        note: sal.note,
+        ranges: sal.ranges.length,
+      });
+      if (sal.ranges.length > 0) {
+        return sal.ranges.map((r) => ({ startId: r.startRef, endId: r.endRef, summary: r.summary, ...(r.topic ? { topic: r.topic } : {}) })) as RangeEntry[];
+      }
       return `Invalid content: not valid JSON (${e instanceof Error ? e.message : String(e)}). content must be an ARRAY of {startId, endId, summary} objects — pass the array directly, not a string.`;
     }
   }

tests/compress-retry.test.ts

@@ -175,6 +175,26 @@ test("compress tool accepts JSON-encoded string content (non-strict-tool provide
   await rm(`${stateFile}.acp.json`, { force: true });
 });
 
+test("compress tool SALVAGES truncated JSON string content (omp#121)", async () => {
+  const { api, handlers } = captureApi();
+  createAcpExtension({ modelContextLimit: 200_000 })(api as any);
+  const stateFile = "/tmp/pai-acp-retry-salvage.session.json";
+  await rm(`${stateFile}.acp.json`, { force: true });
+  const entries = [userMsg("e1", ZH)];
+  const ctx = fakeCtx(() => entries, stateFile);
+  await fire(handlers, ctx); // assigns refs
+
+  const compressTool = api.tools.find((t: any) => t.name === "compress")!;
+  // truncated mid-second-entry: strict parse fails, the first complete entry
+  // must be salvaged by the kernel ladder instead of throwing
+  const truncated =
+    '[{"startId":"m00001","endId":"m00001","summary":"first entry fully intact and salvageable"},{"startId":"m0';
+  const out = await compressTool.execute("tc1", { content: truncated }, undefined, undefined, ctx);
+  const text = typeof out === "string" ? out : out.content?.[0]?.text ?? String(out);
+  assert.ok(/ACP \|/.test(text), `expected success panel: ${text}`);
+  await rm(`${stateFile}.acp.json`, { force: true });
+});
+
 test("compress tool THROWS on garbage string content (isError:true → retry nudge fires)", async () => {
   const { api, handlers } = captureApi();
   createAcpExtension({ modelContextLimit: 200_000 })(api as any);