Hello @brendenguy @Colin
I experienced the same issue. Updating the CLI version resolved it. CLI version: 2026.04.13-a9d7fb5
However, I encountered another issue after the update. When I change the model to claude-sonnet-4-6[thinking=true,context=200k,effort=medium], the following error occurs upon sending a prompt request: "AI Model Not Found Model name is not valid: “claude-sonnet-4-6"”
Below is the RPC log.
agent --api-key "{{user key}}" acp
{"jsonrpc":"2.0","id":0,"method":"initialize","params":{"protocolVersion":1,"clientInfo":{"name":"agent-test","version":"1.0.0"},"capabilities":{}}}
{"jsonrpc":"2.0","id":1,"method":"session/new","params":{"cwd":".","mcpServers":[]}}
{"jsonrpc":"2.0","id":2,"method":"session/set_config_option","params":{"sessionId":"524c638f-c29f-4708-bf15-086cbcc406fc","configId":"model","value":"claude-sonnet-4-6[thinking=true,context=200k,effort=medium]"}}
{"jsonrpc":"2.0","id":2,"result":{"configOptions":[{"id":"mode","name":"Mode","description":"Controls how the agent executes tasks","category":"mode","type":"select","currentValue":"agent","options":[{"value":"agent","name":"Agent","description":"Full agent capabilities with tool access"},{"value":"plan","name":"Plan","description":"Read-only mode for planning and designing before implementation"},{"value":"ask","name":"Ask","description":"Q&A mode - no edits or command execution"}]},{"id":"model","name":"Model","description":"Controls which model variant is used for responses","category":"model","type":"select","currentValue":"claude-sonnet-4-6[thinking=true,context=200k,effort=medium]","options":[{"value":"default[]","name":"Auto"},{"value":"composer-2[fast=true]","name":"composer-2"},{"value":"composer-1.5[]","name":"composer-1.5"},{"value":"gpt-5.3-codex[reasoning=medium,fast=false]","name":"gpt-5.3-codex"},{"value":"gpt-5.4[reasoning=medium,context=272k,fast=false]","name":"gpt-5.4"},{"value":"claude-sonnet-4-6[thinking=true,context=200k,effort=medium]","name":"claude-sonnet-4-6"},{"value":"claude-opus-4-6[thinking=true,context=200k,effort=high,fast=false]","name":"claude-opus-4-6"},{"value":"claude-opus-4-5[thinking=true]","name":"claude-opus-4-5"},{"value":"gpt-5.2[reasoning=medium,fast=false]","name":"gpt-5.2"},{"value":"gemini-3.1-pro[]","name":"gemini-3.1-pro"},{"value":"gpt-5.4-mini[reasoning=medium]","name":"gpt-5.4-mini"},{"value":"gpt-5.4-nano[reasoning=medium]","name":"gpt-5.4-nano"},{"value":"claude-haiku-4-5[thinking=true]","name":"claude-haiku-4-5"},{"value":"gpt-5.3-codex-spark[reasoning=medium]","name":"gpt-5.3-codex-spark"},{"value":"grok-4-20[thinking=true]","name":"grok-4-20"},{"value":"claude-sonnet-4-5[thinking=true,context=200k]","name":"claude-sonnet-4-5"},{"value":"gpt-5.2-codex[reasoning=medium,fast=false]","name":"gpt-5.2-codex"},{"value":"gpt-5.1-codex-max[reasoning=medium,fast=false]","name":"gpt-5.1-codex-max"},{"value":"gpt-5.1[reasoning=medium]","name":"gpt-5.1"},{"value":"gemini-3-flash[]","name":"gemini-3-flash"},{"value":"gpt-5.1-codex-mini[reasoning=medium]","name":"gpt-5.1-codex-mini"},{"value":"claude-sonnet-4[thinking=false,context=200k]","name":"claude-sonnet-4"},{"value":"gpt-5-mini[]","name":"gpt-5-mini"},{"value":"gemini-2.5-flash[]","name":"gemini-2.5-flash"},{"value":"kimi-k2.5[]","name":"kimi-k2.5"}]}]}}
{"jsonrpc":"2.0","id":3,"method":"session/prompt","params":{"sessionId":"524c638f-c29f-4708-bf15-086cbcc406fc","prompt":[{"type":"text","text":"Which company created and trained you? Reply with ONLY the company name, nothing else."}]}}
{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"524c638f-c29f-4708-bf15-086cbcc406fc","update":{"sessionUpdate":"agent_message_chunk","content":{"type":"text","text":"\n\nError: I: AI Model Not Found Model name is not valid: \"claude-sonnet-4-6\""}}}}
{"jsonrpc":"2.0","id":3,"result":{"stopReason":"end_turn"}}
Below is the Test log
=== ACP Model-Switching Reproduction ===
Agent: cursor-agent acp
[init] protocol=1
[auth] authenticating via cursor_login
[session] 2129db4e-fb95-455e-aea8-6966cfb572cb
[model config] current=claude-sonnet-4-6, 25 models available
--- Testing 4 models ---
[switch] Setting model to: Sonnet 4.6 (claude-sonnet-4-6)
[config] reported currentValue: claude-sonnet-4-6
[prompt] "Which company created and trained you? Reply with ONLY the company name, nothing else."
[response] Error: I: AI Model Not Found Model name is not valid: "claude-sonnet-4-6"
[switch] Setting model to: Codex 5.3 (gpt-5.3-codex)
[config] reported currentValue: gpt-5.3-codex
[prompt] "Which company created and trained you? Reply with ONLY the company name, nothing else."
[response] OpenAI
[switch] Setting model to: Gemini 3.1 Pro (gemini-3.1-pro)
[config] reported currentValue: gemini-3.1-pro
[prompt] "Which company created and trained you? Reply with ONLY the company name, nothing else."
[response] 구글
[switch] Setting model to: Grok 4.20 (grok-4-20)
[config] reported currentValue: grok-4-20
[prompt] "Which company created and trained you? Reply with ONLY the company name, nothing else."
[response] **xAI**
=== Summary ===
Model Config Value Response
---------------------------------------------------------------------------
claude-sonnet-4-6 claude-sonnet-4-6 Error: I: AI Model Not Found Model name is not valid: "claude-sonnet-4-6"
gpt-5.3-codex gpt-5.3-codex OpenAI
gemini-3.1-pro gemini-3.1-pro 구글
grok-4-20 grok-4-20 **xAI**
4 unique response(s) across 4 model(s).
>> Responses differ - model switching appears to be working.
[agent exited] code=143