fix(tables): migrate legacy multiselect columns; readable contract error

- Tables created before the select/multiselect merge stored `type:
  'multiselect'`, which the removed type no longer accepts — every response
  carrying such a column failed contract validation and column edits threw.
  getTableById now maps `multiselect` → `select` + `multiple: true` on read
  (covers reads, column ops via withLockedTable, and their responses); the
  migrated shape persists on the table's next schema write.
- requestJson's "Response failed contract validation" now appends a short
  "field: reason" summary of the Zod issues instead of a bare message, so the
  failing field is visible.

Author: TheodoreSpeaks

apps/sim/lib/api/client/request.ts

@@ -161,6 +161,26 @@ function isSchemaValidationError(error: unknown): boolean {
   )
 }
 
+/**
+ * Compresses a ZodError's issues into a short, readable "field: reason" summary
+ * so a failed response tells you which field was wrong instead of a bare
+ * "Response failed contract validation".
+ */
+function summarizeSchemaIssues(error: unknown): string {
+  const issues = (error as { issues?: unknown }).issues
+  if (!Array.isArray(issues)) return ''
+  const summary = issues
+    .slice(0, 3)
+    .map((issue) => {
+      const path = Array.isArray(issue?.path) ? issue.path.join('.') : ''
+      const message = typeof issue?.message === 'string' ? issue.message : 'invalid'
+      return path ? `${path}: ${message}` : message
+    })
+    .join('; ')
+  const extra = issues.length > 3 ? ` (+${issues.length - 3} more)` : ''
+  return summary ? `${summary}${extra}` : ''
+}
+
 export async function requestJson<C extends AnyApiRouteContract>(
   contract: C,
   input: ApiClientRequest<C>
@@ -199,9 +219,12 @@ export async function requestJson<C extends AnyApiRouteContract>(
     return contract.response.schema.parse(parsed) as ContractJsonResponse<C>
   } catch (error) {
     if (isSchemaValidationError(error)) {
+      const details = summarizeSchemaIssues(error)
       throw new ApiClientError({
         status: response.status,
-        message: 'Response failed contract validation',
+        message: details
+          ? `Response failed contract validation — ${details}`
+          : 'Response failed contract validation',
         body: parsed,
         rawBody: raw,
       })

apps/sim/lib/table/service.ts

@@ -86,6 +86,24 @@ export async function withLockedTable<T>(
  * the wire. The client doesn't have to join the two arrays itself — every
  * consumer (grid, sidebar, copilot, mothership) gets the same ordered list.
  */
+/**
+ * Backward-compat for the removed `'multiselect'` column type: map it to a
+ * `select` column with `multiple: true`. Applied on every schema read so legacy
+ * tables — created before the two types were unified — load, edit, and validate
+ * under the current model; the migrated shape persists on the table's next
+ * schema write.
+ */
+function migrateLegacyColumns(schema: TableSchema): TableSchema {
+  let mutated = false
+  const columns = schema.columns.map((c) => {
+    if ((c.type as string) !== 'multiselect') return c
+    mutated = true
+    const { type: _legacyType, ...rest } = c
+    return { ...rest, type: 'select' as const, multiple: true }
+  })
+  return mutated ? { ...schema, columns } : schema
+}
+
 function applyColumnOrderToSchema(
   schema: TableSchema,
   metadata: TableMetadata | null
@@ -151,7 +169,7 @@ export async function getTableById(
     id: table.id,
     name: table.name,
     description: table.description,
-    schema: applyColumnOrderToSchema(table.schema as TableSchema, metadata),
+    schema: applyColumnOrderToSchema(migrateLegacyColumns(table.schema as TableSchema), metadata),
     metadata,
     rowCount: Math.max(0, table.rowCount - pendingDeleteRemaining),
     maxRows: table.maxRows,
@@ -215,7 +233,7 @@ export async function listTables(
       id: t.id,
       name: t.name,
       description: t.description,
-      schema: applyColumnOrderToSchema(t.schema as TableSchema, metadata),
+      schema: applyColumnOrderToSchema(migrateLegacyColumns(t.schema as TableSchema), metadata),
       metadata,
       rowCount: Math.max(0, t.rowCount - pendingDeleteRemaining),
       maxRows: t.maxRows,