diff --git a/src/features/workspaces/collaborative-content-session.ts b/src/features/workspaces/collaborative-content-session.ts
new file mode 100644
index 00000000..9ac4c8e4
--- /dev/null
+++ b/src/features/workspaces/collaborative-content-session.ts
@@ -0,0 +1,31 @@
+import { YServer } from "y-partyserver";
+
+/**
+ * Base for collaborative session Durable Objects whose canonical content lives
+ * in an in-memory Yjs document that `onLoad` hydrates from durable storage.
+ *
+ * These sessions are reached two ways. Browser editors connect over
+ * `fetch`/WebSocket, which runs `onStart` — and therefore `onLoad` — before any
+ * handler touches the document. Server tools instead call methods directly over
+ * native Durable Object RPC, which does not run `onStart`. A content method
+ * invoked cold via RPC would read or edit a freshly constructed, empty document:
+ * returning blank content, or checkpointing an empty document over real content.
+ *
+ * Any RPC method that reads or writes the document must `await
+ * this.ensureLoaded()` first. Methods that only touch durable storage (deletion,
+ * for example) must not, so hydration stays opt-in per method rather than a
+ * blanket cost. New editable item types extend this base so the guarantee — and
+ * the reasoning behind it — live in one place.
+ */
+export abstract class CollaborativeContentSession extends YServer {
+	/**
+	 * Runs `onStart`/`onLoad` for this instance if they have not already. Cheap
+	 * and idempotent once started. `__unsafe_ensureInitialized` is the framework's
+	 * sanctioned escape hatch for Durable Objects reached via native RPC; keeping
+	 * the single call here means content methods never touch an unhydrated
+	 * document and the rationale is not repeated at every call site.
+	 */
+	protected async ensureLoaded(): Promise<void> {
+		await this.__unsafe_ensureInitialized();
+	}
+}
diff --git a/src/features/workspaces/documents/document-session.ts b/src/features/workspaces/documents/document-session.ts
index 9526c0de..6286cbd5 100644
--- a/src/features/workspaces/documents/document-session.ts
+++ b/src/features/workspaces/documents/document-session.ts
@@ -4,9 +4,9 @@ import {
 	yDocToProsemirrorJSON,
 } from "@tiptap/y-tiptap";
 import type { Connection, ConnectionContext } from "partyserver";
-import { YServer } from "y-partyserver";
 import * as Y from "yjs";
 import type { DocumentSessionRouteParams } from "#/features/workspaces/agent-routes";
+import { CollaborativeContentSession } from "#/features/workspaces/collaborative-content-session";
 import {
 	parseMarkdownToTiptapDocumentProjection,
 	serializeTiptapDocumentToMarkdown,
@@ -62,7 +62,7 @@ export interface DocumentSessionApplyMarkdownEditsResult {
 	warnings: string[];
 }
 
-export class DocumentSession extends YServer {
+export class DocumentSession extends CollaborativeContentSession {
 	static override options = {
 		hibernate: true,
 	};
@@ -131,6 +131,7 @@ export class DocumentSession extends YServer {
 	async applyMarkdownEdits(
 		input: DocumentSessionApplyMarkdownEditsInput,
 	): Promise<DocumentSessionApplyMarkdownEditsResult> {
+		await this.ensureLoaded();
 		const currentDocument = this.getCurrentTiptapDocument();
 		const markdown = serializeTiptapDocumentToMarkdown(currentDocument);
 		const editResult = applyDocumentMarkdownEdits(markdown, input.edits);
@@ -176,6 +177,7 @@ export class DocumentSession extends YServer {
 	async readMarkdownChunk(
 		input: DocumentMarkdownChunkReadInput,
 	): Promise<DocumentMarkdownChunkReadResult> {
+		await this.ensureLoaded();
 		const stateVector = Uint8Array.from(Y.encodeStateVector(this.document));
 		let currentSnapshot = this.markdownSnapshot;
 		if (!currentSnapshot || !uint8ArraysEqual(currentSnapshot.stateVector, stateVector)) {
@@ -198,6 +200,8 @@ export class DocumentSession extends YServer {
 	}
 
 	async purgeForDeletion(): Promise<void> {
+		// Deliberately no ensureLoaded(): this only wipes durable storage, so
+		// hydrating the in-memory document first would be wasted work.
 		await this.ctx.storage.deleteAll();
 	}