NetSuite MCP authorization fails at token exchange after consent - all NetSuite-side config confirmed correct

### MCP server URL or name

https://11815891.suitetalk.api.netsuite.com/services/mcp/v1/suiteapp/com.netsuite.mcpstandardtools)

### How are you connecting to this server?

From a custom connector URL I entered manually

### Where does the issue occur?

When pressing the Connect button

### When did you last reproduce this?

2026-07-01 4:58 PM CST

### Browser and OS

Browser

### Describe the issue

Authorization fails with "Authorization with the MCP server failed" immediately after granting consent on the NetSuite OAuth screen, using role "Claude MCP Role."
Confirmed the following are correctly configured on the NetSuite side:

Integration record ("Claude AI"): State = Enabled, Authorization Code Grant ✓, Public Client ✓, Redirect URI = https://claude.ai/api/mcp/auth_callback (exact match), Scope = NetSuite AI Connector Service ✓
Role "Claude MCP Role" permissions (Setup tab): Log in using Access Tokens = Full, Log in using OAuth 2.0 Access Tokens = Full, MCP Server Connection = Full, REST Web Services = Full
MCP Standard Tools SuiteApp installed, v2.1.1 (latest)
Account-level SuiteCloud features enabled (REST Web Services, OAuth 2.0, Server SuiteScript)

### Error details

```shell
Reference: ofid_c1a1a29fadf53a89
NetSuite account: 11815891
Failure point: after OAuth consent (Continue), during token exchange
Role used: Claude MCP Role (Full on all 4 relevant permissions)
Integration record: "Claude AI", Enabled, Authorization Code Grant + Public Client, correct redirect URI, NetSuite AI Connector Service scope checked
SuiteApp: MCP Standard Tools v2.1.1, installed
```

### Expected behavior

Reference: ofid_c1a1a29fadf53a89
NetSuite account: 11815891
Failure point: after OAuth consent (Continue), during token exchange
Role used: Claude MCP Role (Full on all 4 relevant permissions)
Integration record: "Claude AI", Enabled, Authorization Code Grant + Public Client, correct redirect URI, NetSuite AI Connector Service scope checked
SuiteApp: MCP Standard Tools v2.1.1, installed

### Additional context

_No response_