fix: deduplicate compaction terminal failures

web/workspace/src/lib/workspace/console/model.test.ts

@@ -338,6 +338,13 @@ Deno.test("durable compaction failure reconciles live alert and error in both vi
         },
       },
     },
+    {
+      eventId: "controller-error",
+      event: {
+        event: "error",
+        data: { code: "internal", message: "summary unavailable" },
+      },
+    },
     {
       eventId: "failed",
       event: transition("failed-entry", {
@@ -346,13 +353,6 @@ Deno.test("durable compaction failure reconciles live alert and error in both vi
         failure: "compaction",
       }),
     },
-    {
-      eventId: "controller-error",
-      event: {
-        event: "error",
-        data: { code: "internal", message: "summary unavailable" },
-      },
-    },
   ]);
 
   const errors = projection.lines.filter((line) => line.kind === "error");
@@ -362,6 +362,18 @@ Deno.test("durable compaction failure reconciles live alert and error in both vi
   assertEquals(errors[0].entryId, "failed-entry");
   assertEquals(projectConsoleLines(projection.lines, "normal"), errors);
   assertEquals(projectConsoleLines(projection.lines, "overview"), errors);
+
+  const history = projectSessionHistoryEntries([{
+    entry_id: "failed-entry",
+    timestamp: 10,
+    provenance: "legacy_unknown",
+    kind: "run_error",
+    message,
+    failure: "compaction",
+  }], null);
+  const merged = mergeCommittedHistoryLines(history, projection.lines);
+  assertEquals(merged.filter((line) => line.kind === "error").length, 1);
+  assertEquals(merged.find((line) => line.kind === "error")?.entryId, "failed-entry");
 });
 
 Deno.test("snapshot restores compaction terminal without reviving transition progress", () => {
@@ -3232,6 +3244,26 @@ Deno.test("committed history reconciles overlapping Read groups before counting
   }
 });
 
+Deno.test("committed history keeps identical run failures with distinct entry identities", () => {
+  const message = "the same failure happened again";
+  const runError = (entryId: string): SessionSnapshotEntry => ({
+    kind: "run_error",
+    entry_id: entryId,
+    timestamp: 1,
+    provenance: "legacy_unknown",
+    message,
+    failure: "compaction",
+  });
+  const retained = projectSessionHistoryEntries([runError("run-error-1")], null);
+  const current = projectSessionHistoryEntries([runError("run-error-2")], null);
+
+  const merged = mergeCommittedHistoryLines(retained, current);
+  assertEquals(merged.map((line) => line.entryId), ["run-error-1", "run-error-2"]);
+  assertEquals(merged.map((line) => line.body), [message, message]);
+  assertEquals(projectConsoleLines(merged, "normal").length, 2);
+  assertEquals(projectConsoleLines(merged, "overview").length, 2);
+});
+
 Deno.test("committed history matches tool calls across live and durable result identities", () => {
   const retained: ConsoleLine = {
     ...consoleLine("tool-call-a", "tool"), entryId: "call-entry-a",

web/workspace/src/lib/workspace/console/model.ts

@@ -2208,7 +2208,10 @@ function applySessionEntry(
   const entryId = stringField(value, "entry_id");
   if (entryId) {
     for (
-      let index = Math.max(0, lineCountBefore - 1);
+      let index = Math.max(
+        0,
+        Math.min(lineCountBefore, projection.lines.length - 1),
+      );
       index < projection.lines.length;
       index += 1
     ) {