From db46d347272c940057dca1aa7fb4b4456eea8a9e Mon Sep 17 00:00:00 2001
From: Ruben Fiszel <ruben@windmill.dev>
Date: Mon, 3 Aug 2026 22:51:33 +0000
Subject: [PATCH] fix: base a new fork on the dev workspace when forking from
 one (#10489)

* fix: base a new fork on the dev workspace when forking from one

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

* fix: carry dev-workspace fields on the superadmin-synthesized entry

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
---
 .../sessions/WorkspaceFamilyPicker.svelte     | 20 +++++++-----
 .../CreateWorkspaceInner.svelte               | 11 ++++---
 .../lib/utils/useForkableWorkspaces.svelte.ts |  4 +++
 .../src/lib/utils/workspaceHierarchy.test.ts  | 31 +++++++++++++++++++
 frontend/src/lib/utils/workspaceHierarchy.ts  | 25 +++++++++++++++
 5 files changed, 79 insertions(+), 12 deletions(-)
 create mode 100644 frontend/src/lib/utils/workspaceHierarchy.test.ts

diff --git a/frontend/src/lib/components/sessions/WorkspaceFamilyPicker.svelte b/frontend/src/lib/components/sessions/WorkspaceFamilyPicker.svelte
index e1480d5097..6c41dd198b 100644
--- a/frontend/src/lib/components/sessions/WorkspaceFamilyPicker.svelte
+++ b/frontend/src/lib/components/sessions/WorkspaceFamilyPicker.svelte
@@ -12,6 +12,7 @@
 	import {
 		findWorkspaceDescendants,
 		findCanonicalDevWorkspace,
+		findDefaultForkBase,
 		findWorkspaceRoot,
 		buildWorkspaceHierarchy
 	} from '$lib/utils/workspaceHierarchy'
@@ -107,6 +108,9 @@
 	const devOfRoot = $derived(
 		root ? findCanonicalDevWorkspace(root.id, forkableWorkspaces) : undefined
 	)
+	// Base a new fork gets by default: the dev workspace when the selection sits in its subtree, the
+	// family root otherwise.
+	const defaultForkBase = $derived(findDefaultForkBase(effectiveId, forkableWorkspaces))
 	const createForkLabel = 'Create new fork…'
 	// Candidate bases ("targets") for a new fork: the root plus every fork/dev in the family, so a fork
 	// can itself be the base — i.e. a fork of a fork. Root first, matching the list order below.
@@ -205,8 +209,8 @@
 	// Bare fork id, without the wm-fork- prefix. Forks have no separate display
 	// name — the id is the name (it also becomes the git branch).
 	let newForkId = $state('')
-	// The base ("target") a new fork will branch from. Defaults to the root; the user can pick any fork
-	// in the family (via the inline target selector) to create a fork of a fork.
+	// The base ("target") a new fork will branch from. Defaults to `defaultForkBase`; the user can pick
+	// any fork in the family (via the inline target selector) to create a fork of a fork.
 	let createForkBaseId = $state<string | undefined>(undefined)
 
 	// Manual keyboard navigation, modelled after SelectDropdown. melt's
@@ -266,8 +270,8 @@
 	}
 
 	function enterCreateMode(initialId?: string, baseId?: string) {
-		// Default the target to the root; the user can switch to any fork in the family (fork of a fork).
-		createForkBaseId = baseId ?? root?.id
+		// The user can switch to any fork in the family (fork of a fork).
+		createForkBaseId = baseId ?? defaultForkBase?.id
 		creatingFork = true
 		newForkId = initialId ?? defaultForkId()
 		// Focus + select is handled by the input's own autofocus (it mounts with
@@ -338,8 +342,8 @@
 		const wasOpen = lastDropdownOpen
 		lastDropdownOpen = dropdownOpen
 		if (dropdownOpen && !wasOpen && pendingFork && !creatingFork && showCreateFork) {
-			// Preserve the base the fork was staged from; without this the re-entry defaults to the root
-			// and silently re-parents a fork that was staged off another fork.
+			// Preserve the base the fork was staged from; without this the re-entry falls back to the
+			// default base and silently re-parents a fork that was staged off another workspace.
 			void enterCreateMode(
 				pendingFork.id.startsWith(WM_FORK_PREFIX)
 					? pendingFork.id.slice(WM_FORK_PREFIX.length)
@@ -475,8 +479,8 @@
 			{#if showCreateFork}
 				<div class="my-1 border-t border-border-light shrink-0"></div>
 				{#if creatingFork}
-					<!-- Small inline form with labels: fork id + base ("target") workspace. The base
-							     defaults to the root; picking a fork there creates a fork of a fork. -->
+					<!-- Small inline form with labels: fork id + base ("target") workspace. Picking a
+							     fork as the base creates a fork of a fork. -->
 					<div class="flex flex-col gap-2 px-2.5 py-2">
 						<div class="flex flex-col gap-0.5">
 							<span class="text-2xs font-normal text-hint">Fork ID</span>
diff --git a/frontend/src/lib/components/workspaceSettings/CreateWorkspaceInner.svelte b/frontend/src/lib/components/workspaceSettings/CreateWorkspaceInner.svelte
index 23ed37caad..5e54aaef89 100644
--- a/frontend/src/lib/components/workspaceSettings/CreateWorkspaceInner.svelte
+++ b/frontend/src/lib/components/workspaceSettings/CreateWorkspaceInner.svelte
@@ -24,7 +24,8 @@
 	import {
 		workspaceIsFork,
 		findWorkspaceRoot,
-		findWorkspaceDescendants
+		findWorkspaceDescendants,
+		findDefaultForkBase
 	} from '$lib/utils/workspaceHierarchy'
 	import { useForkableWorkspaces } from '$lib/utils/useForkableWorkspaces.svelte'
 	import {
@@ -115,7 +116,9 @@
 			subtitle: w.is_dev_workspace ? 'dev workspace' : w.id === familyRoot?.id ? undefined : 'fork'
 		}))
 	)
-	let defaultBaseWorkspaceId = $derived(familyRoot?.id)
+	let defaultBaseWorkspaceId = $derived(
+		findDefaultForkBase($workspaceStore, forkableWorkspaces)?.id
+	)
 	// Seed the base once the family is known; keep an explicit user choice as long as it stays valid.
 	$effect(() => {
 		if (!isFork) return
@@ -896,8 +899,8 @@
 						{#if createAsDevWorkspace}
 							A dev workspace is always based on the root workspace.
 						{:else}
-							Workspace to fork from. Defaults to the root; pick an existing fork to create a fork
-							of a fork (the new branch is based on the selected workspace's branch).
+							Workspace to fork from: the new branch is based on the selected workspace's branch.
+							Pick an existing fork to create a fork of a fork.
 						{/if}
 					</span>
 					<Select
diff --git a/frontend/src/lib/utils/useForkableWorkspaces.svelte.ts b/frontend/src/lib/utils/useForkableWorkspaces.svelte.ts
index 372d3652a6..c2d95423b9 100644
--- a/frontend/src/lib/utils/useForkableWorkspaces.svelte.ts
+++ b/frontend/src/lib/utils/useForkableWorkspaces.svelte.ts
@@ -42,6 +42,10 @@ export function useForkableWorkspaces(args: {
 					username: '',
 					color: w.color ?? undefined,
 					parent_workspace_id: w.parent_workspace_id,
+					// Dev-ness travels with the entry: the fork-base default and the "dev" badge both read
+					// it off the list, and a synthesized entry missing it reads as an ordinary fork.
+					is_dev_workspace: w.is_dev_workspace,
+					dev_workspace_label: w.dev_workspace_label,
 					disabled: false
 				}
 			]
diff --git a/frontend/src/lib/utils/workspaceHierarchy.test.ts b/frontend/src/lib/utils/workspaceHierarchy.test.ts
new file mode 100644
index 0000000000..38dc12576e
--- /dev/null
+++ b/frontend/src/lib/utils/workspaceHierarchy.test.ts
@@ -0,0 +1,31 @@
+import { describe, expect, it } from 'vitest'
+
+import { findDefaultForkBase } from './workspaceHierarchy'
+import type { UserWorkspace } from '../stores'
+
+function ws(id: string, parent?: string, extra: Partial<UserWorkspace> = {}): UserWorkspace {
+	return { id, name: id, username: 'u', parent_workspace_id: parent, disabled: false, ...extra }
+}
+
+const root = ws('prod')
+const dev = ws('devws', 'prod', { is_dev_workspace: true })
+const forkOfDev = ws('wm-fork-a', 'devws')
+const forkOfRoot = ws('wm-fork-b', 'prod')
+const family = [root, dev, forkOfDev, forkOfRoot]
+
+describe('findDefaultForkBase', () => {
+	it('bases a fork on the dev workspace from inside its subtree', () => {
+		expect(findDefaultForkBase('devws', family)?.id).toBe('devws')
+		expect(findDefaultForkBase('wm-fork-a', family)?.id).toBe('devws')
+	})
+
+	it('bases a fork on the root outside the dev subtree', () => {
+		expect(findDefaultForkBase('prod', family)?.id).toBe('prod')
+		expect(findDefaultForkBase('wm-fork-b', family)?.id).toBe('prod')
+	})
+
+	it('skips a dev workspace the user is disabled in', () => {
+		const disabledDev = [root, { ...dev, disabled: true }, forkOfDev]
+		expect(findDefaultForkBase('wm-fork-a', disabledDev)?.id).toBe('prod')
+	})
+})
diff --git a/frontend/src/lib/utils/workspaceHierarchy.ts b/frontend/src/lib/utils/workspaceHierarchy.ts
index 9c817f49e2..3597d6f4ea 100644
--- a/frontend/src/lib/utils/workspaceHierarchy.ts
+++ b/frontend/src/lib/utils/workspaceHierarchy.ts
@@ -168,6 +168,31 @@ export function findCanonicalDevWorkspace(
 	)
 }
 
+/**
+ * The workspace a new fork should branch from by default. Inside a dev workspace's subtree the base is
+ * that dev workspace, not the family root: the dev workspace carries the changes being worked on, and
+ * a prod locked against forking (`lock_prod_forking`) rejects a root-based fork outright. Anywhere
+ * else it is the family root, so an ad-hoc fork branches from prod rather than from whichever
+ * throwaway fork happens to be open. A dev workspace the user is disabled in is skipped — forking from
+ * it would fail — and the walk continues upwards.
+ */
+export function findDefaultForkBase(
+	currentWorkspaceId: string | undefined,
+	allWorkspaces: UserWorkspace[]
+): UserWorkspace | undefined {
+	let current = allWorkspaces.find((w) => w.id === currentWorkspaceId)
+	while (current) {
+		if (current.is_dev_workspace && !current.disabled) return current
+		if (!current.parent_workspace_id) break
+		const parent: UserWorkspace | undefined = allWorkspaces.find(
+			(w) => w.id === current!.parent_workspace_id
+		)
+		if (!parent) break
+		current = parent
+	}
+	return findWorkspaceRoot(currentWorkspaceId, allWorkspaces)
+}
+
 /**
  * Helper function to find all descendants of a workspace
  */