From 95f9625079e05943742dbc24255a19b550be6f60 Mon Sep 17 00:00:00 2001
From: Waleed Latif <walif6@gmail.com>
Date: Sat, 11 Jul 2026 10:32:58 -0700
Subject: [PATCH] fix(mcp): coerce corrupted consecutiveFailures instead of
 crashing the whole server list
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Root cause: updateServerStatus() only fell back to the default status
config when the whole statusConfig column was null/undefined, not when
it was a real object missing consecutiveFailures (e.g. the column's
'{}' default on server creation). currentConfig.consecutiveFailures
was then undefined, undefined + 1 evaluated to NaN, and
JSON.stringify(NaN) persisted as a literal `null` into the DB the
first time a freshly-created server had a connection failure.

That corrupted value then failed listMcpServersContract's Zod parse
client-side (consecutiveFailures: z.number() rejects null), and since
the response is a single array, one bad server blanked the entire MCP
servers list with "Response failed contract validation" for the whole
workspace — currently affecting 81 servers across 69 production
workspaces.

Two fixes:
- service.ts: normalize the read-back statusConfig so
  consecutiveFailures is always a real number, never NaN, going
  forward.
- contracts/mcp.ts: coerce any non-number consecutiveFailures
  (including the already-corrupted `null` rows) to the schema's
  default of 0 instead of failing validation, so every
  already-affected workspace self-heals on next load with no DB
  migration needed.
---
 apps/sim/lib/api/contracts/mcp.ts |  7 ++++++-
 apps/sim/lib/mcp/service.ts       | 13 ++++++++-----
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/apps/sim/lib/api/contracts/mcp.ts b/apps/sim/lib/api/contracts/mcp.ts
index 1c0159e9ec2..b41cff74d95 100644
--- a/apps/sim/lib/api/contracts/mcp.ts
+++ b/apps/sim/lib/api/contracts/mcp.ts
@@ -38,9 +38,14 @@ export const mcpTransportSchema = z.enum(['streamable-http'])
 
 export const mcpAuthTypeSchema = z.enum(['none', 'headers', 'oauth'])
 
+const consecutiveFailuresSchema = z.preprocess(
+  (value) => (typeof value === 'number' ? value : undefined),
+  z.number().default(0)
+)
+
 export const mcpServerStatusConfigSchema = z
   .object({
-    consecutiveFailures: z.number().default(0),
+    consecutiveFailures: consecutiveFailuresSchema,
     lastSuccessfulDiscovery: z.string().nullable().default(null),
   })
   .passthrough()
diff --git a/apps/sim/lib/mcp/service.ts b/apps/sim/lib/mcp/service.ts
index 12c30e7c8c3..7e97d3fc2de 100644
--- a/apps/sim/lib/mcp/service.ts
+++ b/apps/sim/lib/mcp/service.ts
@@ -328,11 +328,14 @@ class McpService {
         )
         .limit(1)
 
-      const currentConfig: McpServerStatusConfig =
-        (currentServer?.statusConfig as McpServerStatusConfig | null) ?? {
-          consecutiveFailures: 0,
-          lastSuccessfulDiscovery: null,
-        }
+      const storedConfig = currentServer?.statusConfig as Partial<McpServerStatusConfig> | null
+      const currentConfig: McpServerStatusConfig = {
+        consecutiveFailures:
+          typeof storedConfig?.consecutiveFailures === 'number'
+            ? storedConfig.consecutiveFailures
+            : 0,
+        lastSuccessfulDiscovery: storedConfig?.lastSuccessfulDiscovery ?? null,
+      }
 
       const now = new Date()