fix(sessions): spend each write marker only on the tool that wrote it

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KcyBRxE8j3ujCYkum9KrC4

frontend/src/lib/components/copilot/chat/global/core.test.ts

@@ -2160,6 +2160,27 @@ describe('global AI tools', () => {
 		expect(UserDraft.takeDraftOnlyDiscard('resource', path, { workspace: WORKSPACE })).toBe(true)
 	})
 
+	// Nothing consumes a marker outside a session, so one can outlive the item it
+	// was about. Recreating the item must void it, or the next action on the
+	// recreated item reads it and sends a perfectly valid editor back to its list.
+	it('voids a draft-only removal marker when the item is written again', async () => {
+		const path = 'f/resources/discard-then-recreate'
+		await callGlobalTool('write_resource', {
+			path,
+			resource_type: 'postgresql',
+			value: { host: 'localhost' }
+		})
+		await callGlobalTool('discard_local_draft', { type: 'resource', path })
+
+		// The marker is standing (no listener consumed it), and now the item is back.
+		await callGlobalTool('write_resource', {
+			path,
+			resource_type: 'postgresql',
+			value: { host: 'elsewhere' }
+		})
+		expect(UserDraft.takeDraftOnlyDiscard('resource', path, { workspace: WORKSPACE })).toBe(false)
+	})
+
 	// "Create a resource, then never mind": delete_workspace_item must reject a path
 	// that was never deployed, before the confirmation card — otherwise the user
 	// confirms a workspace mutation that 404s past the draft cleanup, leaving the

frontend/src/lib/components/copilot/chat/global/userDraftAdapter.ts

@@ -421,6 +421,9 @@ export async function persistGlobalDraft(
 	const itemKind = itemKindFor(type, opts.triggerKind)
 	if (!itemKind) throw new Error(`Unsupported draft type "${type}".`)
 	const storagePath = resolveDraftStoragePath(workspace, itemKind, path)
+	// Writing the item back means it exists again, so any removal marker left from
+	// an earlier draft-only discard is void.
+	UserDraft.clearDraftOnlyDiscard(itemKind, storagePath, { workspace })
 	UserDraft.seed(itemKind, storagePath, value, { workspace })
 	await UserDraftDbSyncer.save({
 		workspace,

frontend/src/lib/userDraft.svelte.ts

@@ -442,6 +442,13 @@ export const UserDraft = {
 		noteMarker(draftOnlyDiscards, mapKey(resolveWorkspace(opts), itemKind, path))
 	},
 
+	/** Drop any removal marker for this cell — the item exists again, so a marker
+	 * still standing (nothing consumed it, because nothing was listening) would be
+	 * read by whatever touches it next and send its editor away. */
+	clearDraftOnlyDiscard(itemKind: UserDraftItemKind, path: string, opts?: UserDraftOptions): void {
+		draftOnlyDiscards.delete(mapKey(resolveWorkspace(opts), itemKind, path))
+	},
+
 	/** Whether the last discard for this cell removed the item outright (see
 	 * {@link recordDraftOnlyDiscard}), clearing the record. */
 	takeDraftOnlyDiscard(

frontend/src/routes/(root)/(logged)/sessions/+page.svelte

@@ -625,12 +625,20 @@
 			// editor still loading holds none yet and the seed no-opped past it. The
 			// miss is recorded when it happens — asking now would be too late, since
 			// the editor can have acquired the cell during the write's round-trip.
+			// Each marker is read only by the kind of tool that writes it. A marker
+			// left unread — nothing consumes them outside a session — would otherwise
+			// be spent by whatever touched the item next, and a removal marker read by
+			// a deploy sends a live editor away.
 			const kind = path ? entityKindForPage(pages[0]) : undefined
-			const seedReachedEditor = !kind || !path || !UserDraft.takeSeedMiss(kind, path, { workspace })
+			const readable = !!kind && !!path
+			const seedReachedEditor =
+				!readable || entity !== 'none' || !UserDraft.takeSeedMiss(kind!, path!, { workspace })
 			// A discard of a draft-only item removed the item itself, so its editor has
 			// nothing left to re-read and must leave instead.
 			const itemSurvives =
-				!kind || !path || !UserDraft.takeDraftOnlyDiscard(kind, path, { workspace })
+				!readable ||
+				name !== 'discard_local_draft' ||
+				!UserDraft.takeDraftOnlyDiscard(kind!, path!, { workspace })
 			const effect = effectForDiscard(effectForWrite(entity, seedReachedEditor), itemSurvives)
 			if (effect !== 'none') pendingMutations.push({ pages, effect, path, workspace })
 			clearTimeout(reloadHandle)