diff --git a/apps/docs/app/openapi.json/route.ts b/apps/docs/app/openapi.json/route.ts
new file mode 100644
index 00000000000..b668de90a90
--- /dev/null
+++ b/apps/docs/app/openapi.json/route.ts
@@ -0,0 +1,11 @@
+import { createOpenApiDownloadDocument } from '@/lib/openapi-download'
+
+export const revalidate = false
+
+export function GET() {
+  return Response.json(createOpenApiDownloadDocument(), {
+    headers: {
+      'Content-Disposition': 'attachment; filename="sim-openapi-v2.json"',
+    },
+  })
+}
diff --git a/apps/docs/components/docs-layout/sidebar-components.tsx b/apps/docs/components/docs-layout/sidebar-components.tsx
index a899be3a730..2e4112f69f4 100644
--- a/apps/docs/components/docs-layout/sidebar-components.tsx
+++ b/apps/docs/components/docs-layout/sidebar-components.tsx
@@ -69,23 +69,12 @@ export function SidebarItem({ item }: { item: Item }) {
   )
 }
 
-function isApiReferenceFolder(node: Folder): boolean {
-  if (node.index?.url.includes('/api-reference/')) return true
-  for (const child of node.children) {
-    if (child.type === 'page' && child.url.includes('/api-reference/')) return true
-    if (child.type === 'folder' && isApiReferenceFolder(child)) return true
-  }
-  return false
-}
-
 export function SidebarFolder({ item, children }: { item: Folder; children: ReactNode }) {
   const pathname = usePathname()
   const { prefetch } = useSidebar()
   const hasActiveChild = checkHasActiveChild(item, pathname)
-  const isApiRef = isApiReferenceFolder(item)
-  const isOnApiRefPage = pathname.startsWith('/api-reference')
   const hasChildren = item.children.length > 0
-  const defaultOpen = hasActiveChild || (isApiRef && isOnApiRefPage)
+  const defaultOpen = hasActiveChild
   const [manualOpen, setManualOpen] = useState<{ pathname: string; open: boolean } | null>(null)
   const open = manualOpen?.pathname === pathname ? manualOpen.open : defaultOpen
   const toggleOpen = () => setManualOpen({ pathname, open: !open })
@@ -131,6 +120,7 @@ export function SidebarFolder({ item, children }: { item: Folder; children: Reac
                   chipHoverSurfaceClass
                 )}
                 aria-label={open ? 'Collapse' : 'Expand'}
+                aria-expanded={open}
               >
                 <SidebarChevron open={open} className='text-[var(--text-icon)]' />
               </button>
@@ -139,6 +129,7 @@ export function SidebarFolder({ item, children }: { item: Folder; children: Reac
         ) : (
           <button
             onClick={toggleOpen}
+            aria-expanded={open}
             className={cn(
               'flex flex-1 items-center gap-2 rounded-md px-2 py-1.5 text-sm transition-colors',
               'text-[var(--text-body)]',
diff --git a/apps/docs/content/docs/api-reference/getting-started.mdx b/apps/docs/content/docs/api-reference/getting-started.mdx
index 73b72490885..db66a4fd9e6 100644
--- a/apps/docs/content/docs/api-reference/getting-started.mdx
+++ b/apps/docs/content/docs/api-reference/getting-started.mdx
@@ -1,6 +1,6 @@
 ---
 title: Getting Started
-description: Base URL, first API call, response format, error handling, and pagination
+description: Base URL, OpenAPI specification, first API call, response format, error handling, and pagination
 ---
 
 import { Callout } from 'fumadocs-ui/components/callout'
@@ -15,6 +15,10 @@ All API requests are made to:
 https://www.sim.ai
 ```
 
+## OpenAPI specification
+
+Download the [complete OpenAPI 3.1 specification](/openapi.json) as JSON for client generation, request validation, and API tooling.
+
 ## Quick Start
 
 <Steps>
diff --git a/apps/docs/lib/openapi-download.test.ts b/apps/docs/lib/openapi-download.test.ts
new file mode 100644
index 00000000000..2d78e782187
--- /dev/null
+++ b/apps/docs/lib/openapi-download.test.ts
@@ -0,0 +1,71 @@
+import { describe, expect, it } from 'vitest'
+import { createOpenApiDownloadDocument } from '@/lib/openapi-download'
+import { GET } from '@/app/openapi.json/route'
+
+function collectReferences(value: unknown, references: string[] = []): string[] {
+  if (Array.isArray(value)) {
+    for (const item of value) collectReferences(item, references)
+    return references
+  }
+  if (!value || typeof value !== 'object') return references
+
+  for (const [key, item] of Object.entries(value)) {
+    if (key === '$ref' && typeof item === 'string') references.push(item)
+    collectReferences(item, references)
+  }
+  return references
+}
+
+function resolveReference(document: Record<string, unknown>, reference: string): unknown {
+  return reference
+    .replace('#/', '')
+    .split('/')
+    .reduce<unknown>((value, part) => {
+      if (!value || typeof value !== 'object') return undefined
+      return (value as Record<string, unknown>)[part]
+    }, document)
+}
+
+describe('OpenAPI download', () => {
+  it('combines every API domain into one OpenAPI document', () => {
+    const document = createOpenApiDownloadDocument()
+    const paths = document.paths as Record<string, unknown>
+    const tags = document.tags as Array<{ name: string }>
+
+    expect(document.openapi).toBe('3.1.0')
+    expect(Object.keys(paths)).toHaveLength(129)
+    expect(tags.map((tag) => tag.name)).toEqual([
+      'Workflows',
+      'Workflow Runs',
+      'Logs',
+      'Files',
+      'Audit Logs',
+      'Tables',
+      'Knowledge Bases',
+      'Billing',
+      'Meta',
+      'Workspaces',
+      'MCP Servers',
+      'Skills',
+      'Custom Tools',
+      'Credentials',
+      'Secrets',
+      'Catalog',
+    ])
+    for (const reference of collectReferences(document)) {
+      expect(reference).toMatch(/^#\//)
+      expect(resolveReference(document, reference)).toBeDefined()
+    }
+  })
+
+  it('serves the document as a named JSON download', async () => {
+    const response = GET()
+    const document = await response.json()
+
+    expect(response.headers.get('content-type')).toContain('application/json')
+    expect(response.headers.get('content-disposition')).toBe(
+      'attachment; filename="sim-openapi-v2.json"'
+    )
+    expect(document.info.title).toBe('Sim API v2')
+  })
+})
diff --git a/apps/docs/lib/openapi-download.ts b/apps/docs/lib/openapi-download.ts
new file mode 100644
index 00000000000..4ed635367aa
--- /dev/null
+++ b/apps/docs/lib/openapi-download.ts
@@ -0,0 +1,166 @@
+import { isDeepStrictEqual } from 'node:util'
+import { OPENAPI_SPEC_FILES } from '@/lib/openapi-specs'
+import billingSpec from '@/openapi-v2-billing.json'
+import filesAuditSpec from '@/openapi-v2-files-audit.json'
+import knowledgeSpec from '@/openapi-v2-knowledge.json'
+import logsSpec from '@/openapi-v2-logs.json'
+import resourcesSpec from '@/openapi-v2-resources.json'
+import tablesSpec from '@/openapi-v2-tables.json'
+import workflowsSpec from '@/openapi-v2-workflows.json'
+
+type JsonObject = Record<string, unknown>
+type OpenApiSpecFile = (typeof OPENAPI_SPEC_FILES)[number]
+
+const OPENAPI_DOCUMENTS_BY_FILE = {
+  'openapi-v2-workflows.json': workflowsSpec,
+  'openapi-v2-logs.json': logsSpec,
+  'openapi-v2-files-audit.json': filesAuditSpec,
+  'openapi-v2-tables.json': tablesSpec,
+  'openapi-v2-knowledge.json': knowledgeSpec,
+  'openapi-v2-billing.json': billingSpec,
+  'openapi-v2-resources.json': resourcesSpec,
+} satisfies Record<OpenApiSpecFile, JsonObject>
+
+const OPENAPI_DOCUMENTS = OPENAPI_SPEC_FILES.map((file) => ({
+  document: OPENAPI_DOCUMENTS_BY_FILE[file],
+  namespace: file
+    .replace('openapi-v2-', '')
+    .replace('.json', '')
+    .split('-')
+    .map((part) => `${part.charAt(0).toUpperCase()}${part.slice(1)}`)
+    .join(''),
+}))
+
+interface OpenApiDocumentEntry {
+  document: JsonObject
+  namespace: string
+}
+
+function requireObject(value: unknown, label: string): JsonObject {
+  if (!value || typeof value !== 'object' || Array.isArray(value)) {
+    throw new Error(`[docs] ${label} must be an object`)
+  }
+  return value as JsonObject
+}
+
+function assertSharedValue(documents: JsonObject[], key: string): unknown {
+  const value = documents[0]?.[key]
+  for (const document of documents.slice(1)) {
+    if (!isDeepStrictEqual(document[key], value)) {
+      throw new Error(`[docs] OpenAPI documents disagree on ${key}`)
+    }
+  }
+  return value
+}
+
+function mergeUniqueEntries(records: JsonObject[], label: string): JsonObject {
+  const merged: JsonObject = {}
+  for (const record of records) {
+    for (const [key, value] of Object.entries(record)) {
+      if (key in merged && !isDeepStrictEqual(merged[key], value)) {
+        throw new Error(`[docs] Conflicting OpenAPI ${label}: ${key}`)
+      }
+      merged[key] = value
+    }
+  }
+  return merged
+}
+
+function rewriteComponentReferences(value: unknown, namespace: string): unknown {
+  if (Array.isArray(value)) {
+    return value.map((item) => rewriteComponentReferences(item, namespace))
+  }
+  if (!value || typeof value !== 'object') return value
+
+  const rewritten: JsonObject = {}
+  for (const [key, item] of Object.entries(value)) {
+    if (key === '$ref' && typeof item === 'string') {
+      const match = item.match(/^#\/components\/([^/]+)\/(.+)$/)
+      rewritten[key] =
+        match && match[1] !== 'securitySchemes'
+          ? `#/components/${match[1]}/${namespace}_${match[2]}`
+          : item
+      continue
+    }
+    rewritten[key] = rewriteComponentReferences(item, namespace)
+  }
+  return rewritten
+}
+
+function mergeComponents(entries: OpenApiDocumentEntry[]): JsonObject {
+  const merged: JsonObject = {}
+
+  for (const { document, namespace } of entries) {
+    const components = requireObject(document.components, 'components')
+    for (const [componentType, value] of Object.entries(components)) {
+      const componentEntries = requireObject(value, componentType)
+      const existing = requireObject(merged[componentType] ?? {}, componentType)
+
+      if (componentType === 'securitySchemes') {
+        merged[componentType] = mergeUniqueEntries([existing, componentEntries], 'security scheme')
+        continue
+      }
+
+      const namespacedEntries: JsonObject = {}
+      for (const [name, component] of Object.entries(componentEntries)) {
+        namespacedEntries[`${namespace}_${name}`] = rewriteComponentReferences(component, namespace)
+      }
+      merged[componentType] = mergeUniqueEntries([existing, namespacedEntries], componentType)
+    }
+  }
+
+  return merged
+}
+
+function mergeTags(documents: JsonObject[]): unknown[] {
+  const tagsByName = new Map<string, unknown>()
+  for (const document of documents) {
+    if (!Array.isArray(document.tags)) throw new Error('[docs] OpenAPI tags must be an array')
+    for (const tag of document.tags) {
+      const record = requireObject(tag, 'tag')
+      if (typeof record.name !== 'string') throw new Error('[docs] OpenAPI tag requires a name')
+      const existing = tagsByName.get(record.name)
+      if (existing && !isDeepStrictEqual(existing, tag)) {
+        throw new Error(`[docs] Conflicting OpenAPI tag: ${record.name}`)
+      }
+      tagsByName.set(record.name, tag)
+    }
+  }
+  return [...tagsByName.values()]
+}
+
+/** Builds the complete public API description from the domain specs used by the reference UI. */
+export function createOpenApiDownloadDocument(): JsonObject {
+  const entries = OPENAPI_DOCUMENTS
+  const documents = entries.map(({ document }) => document)
+  if (documents.length === 0) throw new Error('[docs] At least one OpenAPI document is required')
+
+  const info = requireObject(documents[0].info, 'info')
+  const version = info.version
+  for (const document of documents.slice(1)) {
+    const documentInfo = requireObject(document.info, 'info')
+    if (documentInfo.version !== version) {
+      throw new Error('[docs] OpenAPI documents disagree on info.version')
+    }
+  }
+
+  return {
+    openapi: assertSharedValue(documents, 'openapi'),
+    info: {
+      title: 'Sim API v2',
+      version,
+      description: 'Complete OpenAPI description for the Sim API v2.',
+    },
+    servers: assertSharedValue(documents, 'servers'),
+    security: assertSharedValue(documents, 'security'),
+    tags: mergeTags(documents),
+    paths: mergeUniqueEntries(
+      entries.map(({ document, namespace }) =>
+        requireObject(rewriteComponentReferences(document.paths, namespace), 'paths')
+      ),
+      'path'
+    ),
+    components: mergeComponents(entries),
+    'x-generated-by': assertSharedValue(documents, 'x-generated-by'),
+  }
+}