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fix(acp): expose Cursor non-fast model variants #6188

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fix(acp): expose Cursor non-fast model variants #6188

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244 changes: 235 additions & 9 deletions crates/buzz-acp/src/acp.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -408,7 +408,12 @@ fn build_client_capabilities() -> serde_json::Value {
// Non-standard extension used by claude-agent-acp to advertise the
// exact terminal login argv for subscription auth. Unknown `_meta`
// keys are ignored by other adapters.
"terminal-auth": true
"terminal-auth": true,
// Cursor otherwise collapses model parameters into a single
// variant ID and only advertises its fast=true default. Buzz
// understands the separate model + fast config options and
// composes them back into one persisted model selection.
"parameterizedModelPicker": true
}
})
}
Expand Down Expand Up @@ -646,8 +651,8 @@ impl AcpClient {
/// member from a null one. When both `ClaudeMeta` and `session_title` are
/// present the two `_meta` members are merged into a single object.
///
/// Callers use [`extract_model_config_options`] and [`extract_model_state`]
/// to pull model info from the raw result.
/// Callers use [`extract_model_picker_config_options`] and
/// [`extract_model_state`] to pull model info from the raw result.
pub async fn session_new_full(
&mut self,
cwd: &str,
Expand Down Expand Up @@ -2158,23 +2163,78 @@ pub enum ModelSwitchMethod {
SetModel { model_id: String },
}

/// Extract `configOptions` entries with `category == "model"` from a `session/new` result.
/// A model change plus any parameter config options encoded in its persisted ID.
#[derive(Debug, Clone, PartialEq)]
pub struct ModelSwitchPlan {
/// The ACP method used to select the base model.
pub model: ModelSwitchMethod,
/// Additional `session/set_config_option` values applied after the model.
pub parameters: Vec<(String, String)>,
}

fn config_option_id(option: &serde_json::Value) -> Option<&str> {
option
.get("configId")
.or_else(|| option.get("id"))
.and_then(|value| value.as_str())
}

fn is_fast_config_option(option: &serde_json::Value) -> bool {
config_option_id(option) == Some("fast")
}

/// Extract base-model `configOptions` entries from a `session/new` result.
///
/// Returns the raw JSON array entries. Each entry has `configId` (spelled `id`
/// by some adapters, e.g. claude-agent-acp), `displayName`,
/// `options: [{ value, displayName }]`, etc.
/// `options: [{ value, displayName }]`, etc. Cursor's separate `fast` model
/// parameter is excluded; use [`extract_model_picker_config_options`] when the
/// caller needs to reconstruct full model choices.
pub fn extract_model_config_options(result: &serde_json::Value) -> Vec<serde_json::Value> {
result["configOptions"]
.as_array()
.map(|arr| {
arr.iter()
.filter(|opt| opt.get("category").and_then(|c| c.as_str()) == Some("model"))
.filter(|opt| {
opt.get("category").and_then(|c| c.as_str()) == Some("model")
&& !is_fast_config_option(opt)
})
.cloned()
.collect()
})
.unwrap_or_default()
}

/// Extract the model selector and the Cursor `fast` parameter needed to
/// reconstruct a complete persisted model choice during discovery.
pub fn extract_model_picker_config_options(result: &serde_json::Value) -> Vec<serde_json::Value> {
result["configOptions"]
.as_array()
.map(|options| {
options
.iter()
.filter(|option| {
option.get("category").and_then(|value| value.as_str()) == Some("model")
|| is_fast_config_option(option)
})
.cloned()
.collect()
})
.unwrap_or_default()
}

fn parse_fast_model_variant(desired_model: &str) -> (&str, Option<&str>) {
for value in ["false", "true"] {
let suffix = format!("[fast={value}]");
if let Some(model) = desired_model.strip_suffix(&suffix) {
if !model.is_empty() {
return (model, Some(value));
}
}
}
(desired_model, None)
}

/// Extract `SessionModelState` (unstable path) from a `session/new` result.
///
/// Returns the `models` object if present: `{ currentModelId, availableModels: [...] }`.
Expand Down Expand Up @@ -2235,6 +2295,38 @@ pub fn resolve_model_switch_method(
None
}

/// Resolve a persisted model ID into the model switch and optional Cursor fast
/// parameter update required by a parameterized model picker.
pub fn resolve_model_switch_plan(
session_new_result: &serde_json::Value,
desired_model: &str,
) -> Option<ModelSwitchPlan> {
let (model_id, fast_value) = parse_fast_model_variant(desired_model);
let model = resolve_model_switch_method(session_new_result, model_id)?;
let mut parameters = Vec::new();

if let Some(value) = fast_value {
let fast_option = session_new_result["configOptions"]
.as_array()?
.iter()
.find(|option| is_fast_config_option(option))?;
let supported = fast_option
.get("options")
.and_then(|options| options.as_array())
.is_some_and(|options| {
options.iter().any(|option| {
option.get("value").and_then(|value| value.as_str()) == Some(value)
})
});
if !supported {
return None;
}
parameters.push(("fast".to_string(), value.to_string()));
}

Some(ModelSwitchPlan { model, parameters })
}

/// Whether `desired_model` appears in pre-extracted catalog halves.
///
/// Mirrors [`resolve_model_switch_method`]'s match, but operates on the
Expand All @@ -2246,17 +2338,35 @@ pub fn model_in_catalog(
available_models: Option<&serde_json::Value>,
desired_model: &str,
) -> bool {
let (model_id, fast_value) = parse_fast_model_variant(desired_model);
let in_config_options = config_options.iter().any(|config_opt| {
if is_fast_config_option(config_opt) {
return false;
}
config_opt
.get("options")
.and_then(|v| v.as_array())
.is_some_and(|options| {
options
.iter()
.any(|opt| opt.get("value").and_then(|v| v.as_str()) == Some(desired_model))
.any(|opt| opt.get("value").and_then(|v| v.as_str()) == Some(model_id))
})
});
if in_config_options {
let fast_supported = fast_value.is_none_or(|desired_fast| {
config_options.iter().any(|config_opt| {
is_fast_config_option(config_opt)
&& config_opt
.get("options")
.and_then(|value| value.as_array())
.is_some_and(|options| {
options.iter().any(|option| {
option.get("value").and_then(|value| value.as_str())
== Some(desired_fast)
})
})
})
});
if in_config_options && fast_supported {
return true;
}

Expand All @@ -2266,8 +2376,9 @@ pub fn model_in_catalog(
.is_some_and(|available| {
available
.iter()
.any(|model| model.get("modelId").and_then(|v| v.as_str()) == Some(desired_model))
.any(|model| model.get("modelId").and_then(|v| v.as_str()) == Some(model_id))
})
&& fast_supported
}

// ─── Drop: kill child process ─────────────────────────────────────────────────
Expand Down Expand Up @@ -2497,6 +2608,11 @@ mod tests {
Some(true),
"goose customNotifications capability must be advertised"
);
assert_eq!(
msg["params"]["clientCapabilities"]["_meta"]["parameterizedModelPicker"].as_bool(),
Some(true),
"parameterized model picker support must be advertised so Cursor exposes fast=false"
);
}

#[test]
Expand Down Expand Up @@ -2712,6 +2828,36 @@ mod tests {
assert_eq!(opts[0]["configId"].as_str(), Some("model"));
}

#[test]
fn extract_model_picker_config_options_includes_cursor_fast_parameter() {
let result = serde_json::json!({
"configOptions": [
{
"id": "model",
"category": "model",
"options": [{ "value": "grok-4.6" }]
},
{
"id": "fast",
"options": [
{ "value": "false" },
{ "value": "true" }
]
},
{
"id": "theme",
"category": "appearance",
"options": [{ "value": "dark" }]
}
]
});

let options = super::extract_model_picker_config_options(&result);
assert_eq!(options.len(), 2);
assert_eq!(options[0]["id"].as_str(), Some("model"));
assert_eq!(options[1]["id"].as_str(), Some("fast"));
}

#[test]
fn extract_model_config_options_empty_when_no_config_options() {
let result = serde_json::json!({ "sessionId": "sess-1" });
Expand Down Expand Up @@ -2877,6 +3023,61 @@ mod tests {
);
}

#[test]
fn resolve_parameterized_fast_variant_builds_ordered_switch_plan() {
let result = serde_json::json!({
"configOptions": [
{
"id": "model",
"category": "model",
"options": [{ "value": "grok-4.6" }]
},
{
"id": "fast",
"category": "model",
"options": [
{ "value": "false" },
{ "value": "true" }
]
}
]
});

let plan = super::resolve_model_switch_plan(&result, "grok-4.6[fast=false]")
.expect("parameterized model should resolve");

assert_eq!(
plan,
super::ModelSwitchPlan {
model: super::ModelSwitchMethod::ConfigOption {
config_id: "model".to_string(),
option_value: "grok-4.6".to_string(),
},
parameters: vec![("fast".to_string(), "false".to_string())],
}
);
}

#[test]
fn resolve_parameterized_fast_variant_rejects_unadvertised_value() {
let result = serde_json::json!({
"configOptions": [
{
"id": "model",
"category": "model",
"options": [{ "value": "grok-4.6" }]
},
{
"id": "fast",
"category": "model",
"options": [{ "value": "true" }]
}
]
});

assert!(super::resolve_model_switch_plan(&result, "grok-4.6[fast=false]").is_none());
}

// ── model_in_catalog tests ────────────────────────────────────────────

#[test]
Expand Down Expand Up @@ -2929,6 +3130,31 @@ mod tests {
assert!(!super::model_in_catalog(&[], None, "anything"));
}

#[test]
fn model_in_catalog_accepts_parameterized_fast_variant() {
let config_options = vec![
serde_json::json!({
"id": "model",
"category": "model",
"options": [{ "value": "grok-4.6" }]
}),
serde_json::json!({
"id": "fast",
"category": "model",
"options": [
{ "value": "false" },
{ "value": "true" }
]
}),
];

assert!(super::model_in_catalog(
&config_options,
None,
"grok-4.6[fast=false]"
));
}

// ── Error variant display ─────────────────────────────────────────────

#[test]
Expand Down
4 changes: 2 additions & 2 deletions crates/buzz-acp/src/lib.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -4984,7 +4984,7 @@ async fn run_authenticate(args: AuthenticateArgs) -> Result<()> {
/// Flow: spawn → initialize → session/new → print models → shutdown.
/// No relay connection, no MCP servers, no subscriptions. ~2-5s total.
async fn run_models(args: ModelsArgs) -> Result<()> {
use acp::{extract_model_config_options, extract_model_state};
use acp::{extract_model_picker_config_options, extract_model_state};

let agent_args = config::normalize_agent_args(&args.agent.agent_command, args.agent.agent_args);
let cwd = std::env::current_dir()
Expand Down Expand Up @@ -5041,7 +5041,7 @@ async fn run_models(args: ModelsArgs) -> Result<()> {
.unwrap_or("unknown");

// Extract model info from session/new response.
let config_options = extract_model_config_options(&session_resp.raw);
let config_options = extract_model_picker_config_options(&session_resp.raw);
let model_state = extract_model_state(&session_resp.raw);

if args.json {
Expand Down
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