claude-code - 💡(How to fix) Fix [BUG] 2.1.154 appears to send messages[].role="system" to Anthropic-compatible providers, causing schema parse failures

{
  "has_top_level_system": true,
  "top_level_system_type": "array",
  "message_roles": ["user", "system"],
  "system_messages_in_messages": [
    {
      "index": 1,
      "content_preview": "The following skills are available for use with the Skill tool: ..."
    }
  ]
}

---

{
  "role": "system",
  "content": "SessionStart hook additional context: ..."
}

---

API Error: 400 Failed to deserialize the JSON body into the target type:
messages[1].role: unknown variant `system`, expected `user` or `assistant`


Raw request body summary captured with `OTEL_LOG_RAW_API_BODIES=file:<dir>`:


{
  "model": "deepseek-v4-pro",
  "has_top_level_system": true,
  "top_level_system_type": "array",
  "message_roles": [
    "user",
    "system"
  ],
  "system_messages_in_messages": [
    {
      "index": 1,
      "content_preview": "The following skills are available for use with the Skill tool:\n\n- context7-mcp: ..."
    }
  ]
}


The same error also occurs with another model on the same provider, so this appears to fail during request schema parsing before model execution.

---

$env:ANTHROPIC_BASE_URL = "<third-party-anthropic-compatible-base-url>"
$env:ANTHROPIC_AUTH_TOKEN = "<redacted>"
$env:ANTHROPIC_MODEL = "deepseek-v4-pro"
$env:ANTHROPIC_DEFAULT_SONNET_MODEL = "deepseek-v4-pro"
$env:ANTHROPIC_DEFAULT_OPUS_MODEL = "deepseek-v4-pro"
$env:ANTHROPIC_DEFAULT_HAIKU_MODEL = "deepseek-v4-pro"

---

$clean = Join-Path $env:TEMP ("cc-clean-" + [guid]::NewGuid().ToString())
New-Item -ItemType Directory $clean | Out-Null

$work = Join-Path $env:TEMP ("cc-work-" + [guid]::NewGuid().ToString())
New-Item -ItemType Directory $work | Out-Null
cd $work

$env:CLAUDE_CONFIG_DIR = $clean

claude -p "hi"

---

API Error: 400 Failed to deserialize the JSON body into the target type:
messages[1].role: unknown variant `system`, expected `user` or `assistant`

---

$dump = "$env:TEMP\cc-api-dump"
Remove-Item $dump -Recurse -Force -ErrorAction SilentlyContinue
New-Item -ItemType Directory $dump | Out-Null

$env:CLAUDE_CODE_ENABLE_TELEMETRY = "1"
$env:OTEL_LOGS_EXPORTER = "console"
$env:OTEL_METRICS_EXPORTER = "none"
$env:OTEL_LOG_RAW_API_BODIES = "file:$dump"
$env:OTEL_LOGS_EXPORT_INTERVAL = "1000"

claude -p "hi"

---

$req = Get-ChildItem $dump -Recurse -Filter "*.request.json" |
  Sort-Object LastWriteTime |
  Select-Object -Last 1

Get-Content $req.FullName -Raw | jq '{
  model,
  has_top_level_system: has("system"),
  top_level_system_type: (.system | type),
  message_roles: [.messages[].role],
  system_messages_in_messages: [
    .messages
    | to_entries[]
    | select(.value.role == "system")
    | {
        index: .key,
        content_preview: ((.value.content | tostring)[0:1200])
      }
  ]
}'

---

{
  "message_roles": ["user", "system"],
  "system_messages_in_messages": [
    {
      "index": 1,
      "content_preview": "The following skills are available for use with the Skill tool: ..."
    }
  ]
}

---

{
  "system": "You are a helpful assistant.",
  "messages": [
    {
      "role": "user",
      "content": [
        {
          "type": "text",
          "text": "hi"
        }
      ]
    }
  ]
}

---

The following skills are available for use with the Skill tool:
...