fix(workspaces): stream kernel file reads to avoid Durable Object resets

src/features/workspaces/components/WorkspaceFileViewer.tsx

@@ -2,6 +2,7 @@ import { type ComponentType, type LazyExoticComponent, lazy, Suspense } from "re
 
 import { ContextMenu, ContextMenuTrigger } from "#/components/ui/context-menu";
 import { Spinner } from "#/components/ui/spinner";
+import WorkspaceFileViewerErrorBoundary from "#/features/workspaces/components/WorkspaceFileViewerErrorBoundary";
 import { WorkspaceItemActionsContextMenuContent } from "#/features/workspaces/components/WorkspaceItemActionsMenu";
 import { useWorkspaceViewCapabilities } from "#/features/workspaces/components/workspace-view-policy";
 import { getWorkspaceItemDisplay } from "#/features/workspaces/model/item-display";
@@ -47,9 +48,11 @@ export default function WorkspaceFileViewer({
 	const Viewer = descriptor ? workspaceFileViewers[descriptor.assetKind] : null;
 	const viewCapabilities = useWorkspaceViewCapabilities();
 	const viewerContent = Viewer ? (
-		<Suspense fallback={<WorkspaceFileViewerSkeleton />}>
-			<Viewer item={item} toolbarSlotId={toolbarSlotId} workspaceId={workspaceId} />
-		</Suspense>
+		<WorkspaceFileViewerErrorBoundary key={item.id} fileName={item.name}>
+			<Suspense fallback={<WorkspaceFileViewerSkeleton />}>
+				<Viewer item={item} toolbarSlotId={toolbarSlotId} workspaceId={workspaceId} />
+			</Suspense>
+		</WorkspaceFileViewerErrorBoundary>
 	) : (
 		<div className="flex h-full items-center justify-center bg-background">
 			<WorkspaceUnsupportedFilePlaceholder item={item} />

src/features/workspaces/components/WorkspaceFileViewerErrorBoundary.tsx

@@ -0,0 +1,61 @@
+import { Component, type ErrorInfo, type ReactNode } from "react";
+
+import { Button } from "#/components/ui/button";
+import { capturePostHogClientException } from "#/integrations/posthog/provider";
+
+interface WorkspaceFileViewerErrorBoundaryProps {
+	fileName: string;
+	children: ReactNode;
+}
+
+interface WorkspaceFileViewerErrorBoundaryState {
+	error: Error | null;
+}
+
+/**
+ * Contains file-viewer failures to the viewer pane instead of letting them bubble to the
+ * root error boundary and take the whole workspace page down. This is the safety net for a
+ * WorkspaceKernel Durable Object reset dropping a content request mid-flight.
+ */
+export default class WorkspaceFileViewerErrorBoundary extends Component<
+	WorkspaceFileViewerErrorBoundaryProps,
+	WorkspaceFileViewerErrorBoundaryState
+> {
+	state: WorkspaceFileViewerErrorBoundaryState = {
+		error: null,
+	};
+
+	static getDerivedStateFromError(error: Error) {
+		return { error };
+	}
+
+	componentDidCatch(error: Error, errorInfo: ErrorInfo) {
+		console.error("Workspace file viewer failed", error, errorInfo);
+		capturePostHogClientException(error, {
+			component_stack: errorInfo.componentStack,
+			error_boundary: "WorkspaceFileViewerErrorBoundary",
+		});
+	}
+
+	render() {
+		const { error } = this.state;
+
+		if (!error) {
+			return this.props.children;
+		}
+
+		return (
+			<div className="flex h-full min-h-0 flex-col items-center justify-center gap-3 bg-background px-4 text-center">
+				<div className="space-y-1">
+					<h2 className="font-medium text-foreground text-sm">Unable to load this file</h2>
+					<p className="text-muted-foreground text-xs">
+						Something went wrong while opening “{this.props.fileName}”. Try again in a moment.
+					</p>
+				</div>
+				<Button variant="outline" size="sm" onClick={() => this.setState({ error: null })}>
+					Retry
+				</Button>
+			</div>
+		);
+	}
+}

src/features/workspaces/kernel/workspace-kernel-access.ts

@@ -18,6 +18,7 @@ import type {
 	DeleteWorkspaceKernelItemsResult,
 	ListWorkspaceKernelItemRelationsArgs,
 	MoveWorkspaceKernelItemsResult,
+	ReadWorkspaceKernelFileContentStreamResult,
 	ReadWorkspaceKernelFilePreviewResult,
 	ReadWorkspaceKernelFileProjectionArgs,
 	ReadWorkspaceKernelFileProjectionResult,
@@ -100,6 +101,9 @@ export interface WorkspaceKernelClient {
 		fileName: string;
 		sizeBytes: number;
 	}>;
+	readFileContentStream(input: {
+		itemId: string;
+	}): Promise<ReadWorkspaceKernelFileContentStreamResult>;
 	readFilePreview(input: { itemId: string }): Promise<ReadWorkspaceKernelFilePreviewResult | null>;
 	upsertFileProjection(input: UpsertWorkspaceKernelFileProjectionArgs): Promise<void>;
 	readFileProjection(
@@ -114,7 +118,7 @@ export interface WorkspaceKernelClient {
 	purgeForDeletion(): Promise<void>;
 }
 
-export async function readWorkspaceKernelFileContent(input: {
+export async function readWorkspaceKernelFileContentStream(input: {
 	workspaceId: string;
 	userId: string;
 	itemId: string;
@@ -125,7 +129,7 @@ export async function readWorkspaceKernelFileContent(input: {
 		await assertCanReadWorkspace(dbContext.db, input);
 		const kernel = await getWorkspaceKernel(input.workspaceId);
 
-		return await kernel.readFileContent({ itemId: input.itemId });
+		return await kernel.readFileContentStream({ itemId: input.itemId });
 	} finally {
 		await dbContext.dispose();
 	}

src/features/workspaces/kernel/workspace-kernel-file-commands.ts

@@ -17,6 +17,7 @@ import type {
 	CreateWorkspaceKernelFileFromUploadArgs,
 	ReadWorkspaceKernelFileContentArgs,
 	ReadWorkspaceKernelFileContentResult,
+	ReadWorkspaceKernelFileContentStreamResult,
 	ReadWorkspaceKernelFilePreviewResult,
 	ReadWorkspaceKernelFileProjectionArgs,
 	ReadWorkspaceKernelFileProjectionResult,
@@ -191,6 +192,37 @@ export class WorkspaceKernelFileCommands {
 		};
 	}
 
+	async readFileContentStream(
+		input: ReadWorkspaceKernelFileContentArgs,
+	): Promise<ReadWorkspaceKernelFileContentStreamResult> {
+		const row = this.store.assertActiveItem(input.itemId);
+
+		if (row.type !== "file") {
+			throw new Error("Workspace item is not a file.");
+		}
+
+		// Stream bytes straight from storage (R2 for large files) instead of buffering the
+		// whole blob into the Durable Object isolate, which trips Cloudflare's memory limit
+		// and resets the object on large files/PDFs.
+		const stream = await this.workspace.readFileStream(row.shell_path);
+
+		if (!stream) {
+			throw new Error("Workspace file content was not found.");
+		}
+
+		const item = this.store.requireItem(input.itemId);
+		const contentType = getMetadataString(item.metadataJson, "mimeType");
+		const originalName = getMetadataString(item.metadataJson, "originalName");
+		const sizeBytes = getMetadataNumber(item.metadataJson, "sizeBytes");
+
+		return {
+			stream,
+			contentType: contentType ?? "application/octet-stream",
+			fileName: originalName ?? item.name,
+			sizeBytes: sizeBytes ?? null,
+		};
+	}
+
 	async readFilePreview(
 		input: ReadWorkspaceKernelFileContentArgs,
 	): Promise<ReadWorkspaceKernelFilePreviewResult | null> {

src/features/workspaces/kernel/workspace-kernel-types.ts

@@ -105,6 +105,13 @@ export interface ReadWorkspaceKernelFileContentResult {
 	sizeBytes: number;
 }
 
+export interface ReadWorkspaceKernelFileContentStreamResult {
+	stream: ReadableStream<Uint8Array>;
+	contentType: string;
+	fileName: string;
+	sizeBytes: number | null;
+}
+
 export type WorkspaceKernelFileProjectionFormat = "pages" | "preview";
 
 export type WorkspaceKernelFileProjectionStatus =

src/features/workspaces/kernel/workspace-kernel.ts

@@ -44,7 +44,11 @@ import type {
 	WorkspaceRealtimeServerMessage,
 } from "#/features/workspaces/realtime/messages";
 
-const workspaceKernelInlineThresholdBytes = 1_500_000;
+// Keep only small files inline in the Durable Object's SQLite. Anything larger spills to R2 so
+// big files/PDFs never bloat a single SQLite row (base64 inflates ~33%), which was tripping
+// Cloudflare's storage-operation timeout and resetting the object. Existing files keep whatever
+// backend they were written with — this threshold only governs new writes.
+const workspaceKernelInlineThresholdBytes = 128 * 1024;
 
 export { setWorkspaceKernelUserHeaders };
 
@@ -149,6 +153,10 @@ export class WorkspaceKernel extends Agent<Cloudflare.Env> {
 		return await this.fileCommands.readFileContent(input);
 	}
 
+	async readFileContentStream(input: ReadWorkspaceKernelFileContentArgs) {
+		return await this.fileCommands.readFileContentStream(input);
+	}
+
 	async readFilePreview(input: ReadWorkspaceKernelFileContentArgs) {
 		return await this.fileCommands.readFilePreview(input);
 	}

src/routes/api/v1/workspaces.$workspaceId.files.$itemId.content.ts

@@ -1,6 +1,6 @@
 import { createFileRoute } from "@tanstack/react-router";
 
-import { readWorkspaceKernelFileContent } from "#/features/workspaces/kernel/workspace-kernel-access";
+import { readWorkspaceKernelFileContentStream } from "#/features/workspaces/kernel/workspace-kernel-access";
 import { WorkspaceForbiddenError } from "#/features/workspaces/server/permissions";
 import { apiError, getRequestId } from "#/lib/api/http";
 import { getSessionFromRequest } from "#/lib/auth-queries.server";
@@ -20,22 +20,24 @@ async function handleWorkspaceFileContent(request: Request, workspaceId: string,
 			);
 		}
 
-		const content = await readWorkspaceKernelFileContent({
+		const content = await readWorkspaceKernelFileContentStream({
 			workspaceId,
 			userId: session.user.id,
 			itemId,
 		});
-		const body = new Uint8Array(content.bytes).buffer;
 
-		return new Response(body, {
-			headers: {
-				"cache-control": "private, max-age=60",
-				"content-disposition": `inline; filename="${sanitizeHeaderFileName(content.fileName)}"`,
-				"content-length": String(body.byteLength),
-				"content-type": content.contentType,
-				"x-request-id": requestId,
-			},
+		const headers = new Headers({
+			"cache-control": "private, max-age=60",
+			"content-disposition": `inline; filename="${sanitizeHeaderFileName(content.fileName)}"`,
+			"content-type": content.contentType,
+			"x-request-id": requestId,
 		});
+
+		if (content.sizeBytes != null && content.sizeBytes >= 0) {
+			headers.set("content-length", String(content.sizeBytes));
+		}
+
+		return new Response(content.stream, { headers });
 	} catch (error) {
 		if (error instanceof WorkspaceForbiddenError) {
 			return apiError(