KimiK2-thinking fails at subagent call

[driebe]

Description

KimiK2-thinking often (but not always) fails to invoke the @documenter agent to write documentation updates to md files (c.f. chat log below). This does never happen with opencode/qwen3-coder or opencode/claude-sonnet-4-5 - so the agent itself seems to be configured correctly.

Additional info: the @documenter agent is based on zen GPT5-nano with extra settings in the opencode.json file:

        "gpt-5-nano-low": {
          "id": "gpt-5-nano",
          "options": {
            "reasoningEffort": "low",
            "textVerbosity": "low",
            "reasoningSummary": "auto",

OpenCode version

1.0.223

Steps to reproduce

No response

Screenshot and/or share link

◉ : Documenter Task ": Create PLAN document for dev environment fixes"
ctrl+z right view subagents
Unknown agent type: : documenter is not a valid agent type
Thinking: I need to use the correct agent type. Let me check the available agents again. The available agents are:
- explore
- documenter
- assistant
- tester
- frontend
- refactor
- backend
- auditor
- devops
So "documenter" should work. Let me try without the colon prefix.
◉ : Documenter Task ": Create PLAN document for dev environment fixes"
ctrl+z right view subagents
Unknown agent type: : documenter is not a valid agent type
Thinking: The agent type should be just "documenter" without the colon. Let me try again.
◉ : Documenter Task ": Create PLAN document for dev environment fixes"
ctrl+z right view subagents
Unknown agent type: : documenter is not a valid agent type
Thinking: I need to check the exact agent types. Let me look at the system message again. The available agents are:
- explore
- documenter
- assistant
- tester
- frontend
- refactor
- backend
- auditor
- devops
So "documenter" should be correct. Let me try without any colon prefix.
◉ : Documenter Task ": Create PLAN document for dev environment fixes"
ctrl+z right view subagents
Unknown agent type: : documenter is not a valid agent type
Thinking: Let me check the exact format from the system message. It says:
"Available agent types and the tools they have access to:
- explore: Fast agent specialized for exploring codebases...
- documenter: Documentation Agent
- assistant: Assisstant
- tester: Test Engineer Agent
- frontend: Frontend Developer Agent
- refactor: Refactor / Code Reviewer Agent
- backend: Writes backend code for a specific task...
- auditor: Security Auditor / Engineer Agent
- devops: DevOps Engineer Agent"
So the type should be "documenter". Let me try without the colon at all.
◉ : Documenter Task ": Create PLAN document for dev environment fixes"
ctrl+z right view subagents
Unknown agent type: : documenter is not a valid agent type
Thinking: I see the issue - I'm using a colon prefix in the subagent_type parameter. Let me check the function definition again. Looking at the tool definition:
"parameters": {
  "description": "The task for the agent to perform",
  "type": "string"
},
"session_id": {
  "description": "Existing Task session to continue",
  "type": "string"
},
"subagent_type": {
  "description": "The type of specialized agent to use for this task",
  "type": "string"
}
So I should just pass "documenter" as the string value, not ": documenter". Let me fix that.
◉ : Documenter Task ": Create PLAN document for dev environment fixes"
ctrl+z right view subagents
Unknown agent type: : documenter is not a valid agent type
Thinking: I'm still using the colon prefix. Let me remove it completely.
◉ : Documenter Task ": Create PLAN document for dev environment fixes"
ctrl+z right view subagents
Unknown agent type: : documenter is not a valid agent type

Operating System

Ubuntu 24.04.3 LTS, 6.8.0-90-generic

Terminal

No response