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fix: strip blockContent from tool results to prevent O(n²) token growth #241

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fix: strip blockContent from tool results to prevent O(n²) token growth #241

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48 changes: 37 additions & 11 deletions src/lib/ai/workers/workspace-worker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,32 @@ import { getNoteContentAsMarkdown } from "@/lib/utils/format-workspace-context";
import { serializeBlockNote } from "@/lib/utils/serialize-blocknote";
import type { Block } from "@/components/editor/BlockNoteEditor";

/**
* Returns the event to include in the tool result, or undefined if the event
* should be omitted entirely from the tool result.
*
* ITEM_UPDATED events that carry blockContent are omitted because:
* 1. Zero token cost — no event JSON enters the AI SDK conversation history,
* preventing O(n²) token growth when the AI makes serial note edits.
* 2. Correct UI rendering — useOptimisticToolUpdate skips the cache update
* when result.event is undefined, so the Supabase broadcast delivers the
* full event (with blockContent) without being deduplicated against a stale
* cache entry. Without this, the editor would show old blocks until a refresh.
*
* The full event is always persisted to the DB regardless of what this returns.
*/
function eventForToolResult(event: WorkspaceEvent): WorkspaceEvent | undefined {
if (event.type === "ITEM_UPDATED") {
const data = (event.payload.changes as any)?.data;
if (!data || !("blockContent" in data)) return event;
return undefined;
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@cubic-dev-ai cubic-dev-ai bot Mar 16, 2026 •
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P1: Dropping the update event here prevents the initiating client from seeing AI note edits until a refetch, because neither the optimistic hook nor realtime will apply a replacement event.

Prompt for AI agents 
Check if this issue is valid — if so, understand the root cause and fix it. At src/lib/ai/workers/workspace-worker.ts, line 41:

<comment>Dropping the update event here prevents the initiating client from seeing AI note edits until a refetch, because neither the optimistic hook nor realtime will apply a replacement event.</comment>

<file context>
@@ -20,6 +20,32 @@ import { getNoteContentAsMarkdown } from "@/lib/utils/format-workspace-context";
+    if (event.type === "ITEM_UPDATED") {
+        const data = (event.payload.changes as any)?.data;
+        if (!data || !("blockContent" in data)) return event;
+        return undefined;
+    }
+    // ITEM_CREATED: keep the full event so the optimistic cache shows the new note
</file context>
Fix with Cubic

}
// ITEM_CREATED: keep the full event so the optimistic cache shows the new note
// immediately with correct block rendering. The create event appears only once
// in conversation history so its token cost is fixed, not O(n²).
return event;
}

/** Create params for a single item (used by create and bulkCreate). Exported for autogen. */
export type CreateItemParams = {
id?: string; // Optional pre-generated item ID (if not provided, one is generated)
Expand Down Expand Up @@ -406,7 +432,7 @@ export async function workspaceWorker(
itemId: item.id,
message: `Created ${item.type} "${item.name}" successfully`,
cardCount,
event,
event: eventForToolResult(event),
version: appendResult.version,
};
}
Expand Down Expand Up @@ -660,7 +686,7 @@ export async function workspaceWorker(
success: true,
itemId: params.itemId,
message: `Updated note successfully`,
event,
event: eventForToolResult(event),
version: appendResult.version,
};
if (diffOutput) {
Expand Down Expand Up @@ -781,7 +807,7 @@ export async function workspaceWorker(
itemId: params.itemId,
cardsAdded: newCards.length,
message: `Added ${newCards.length} card${newCards.length !== 1 ? 's' : ''} to flashcard deck${params.title ? ` and renamed to "${params.title}"` : ''}`,
event,
event: eventForToolResult(event),
version: appendResult.version,
};
}
Expand Down Expand Up @@ -902,7 +928,7 @@ export async function workspaceWorker(
message: hasQuestions
? `Added ${questionsToAdd!.length} question${questionsToAdd!.length !== 1 ? "s" : ""} to quiz`
: "Quiz title updated.",
event,
event: eventForToolResult(event),
version: appendResult.version,
};
}
Expand Down Expand Up @@ -988,7 +1014,7 @@ export async function workspaceWorker(
success: true,
itemId: params.itemId,
message: `Cached text content for PDF "${existingItem.name}" (${contentLen} chars)`,
event,
event: eventForToolResult(event),
version: appendResult.version,
};
}
Expand Down Expand Up @@ -1058,7 +1084,7 @@ export async function workspaceWorker(
success: true,
itemId: params.itemId,
message: params.imageOcrStatus === "failed" ? "Marked image OCR as failed" : `Cached OCR content for image "${existingItem.name}"`,
event,
event: eventForToolResult(event),
version: appendResult.version,
};
}
Expand Down Expand Up @@ -1154,7 +1180,7 @@ export async function workspaceWorker(
success: true,
itemId: params.itemId,
message: "Updated note successfully",
event,
event: eventForToolResult(event),
version: appendResult.version,
diff: diffOutput,
filediff: { additions: filediffAdditions, deletions: filediffDeletions },
Expand Down Expand Up @@ -1245,7 +1271,7 @@ export async function workspaceWorker(
success: true,
itemId: params.itemId,
message: `Updated flashcard deck (${newCards.length} cards)`,
event,
event: eventForToolResult(event),
version: appendResult.version,
cardCount: newCards.length,
};
Expand Down Expand Up @@ -1332,7 +1358,7 @@ export async function workspaceWorker(
success: true,
itemId: params.itemId,
message: `Updated quiz (${validatedQuestions.length} questions)`,
event,
event: eventForToolResult(event),
version: appendResult.version,
questionCount: validatedQuestions.length,
};
Expand Down Expand Up @@ -1368,7 +1394,7 @@ export async function workspaceWorker(
success: true,
itemId: params.itemId,
message: `Renamed PDF to "${rename}"`,
event,
event: eventForToolResult(event),
version: appendResult.version,
};
}
Expand Down Expand Up @@ -1419,7 +1445,7 @@ export async function workspaceWorker(
success: true,
itemId: params.itemId,
message: `Deleted note successfully`,
event,
event: eventForToolResult(event),
version: appendResult.version,
};
}
Expand Down
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