refactor(agent): share model endpoint resolution

Signed-off-by: Alex Rosenzweig <arosenzweig@squareup.com>

crates/buzz-agent/src/config.rs

@@ -1,3 +1,5 @@
+pub mod endpoint;
+
 use std::time::Duration;
 
 pub const PROTOCOL_VERSION: u32 = 2;
@@ -639,7 +641,6 @@ pub struct Config {
 
 impl Config {
     pub fn from_env() -> Result<Self, String> {
-        let databricks_host = env("DATABRICKS_HOST");
         let databricks_model = env("DATABRICKS_MODEL");
         let provider = resolve_provider(
             env("BUZZ_AGENT_PROVIDER").as_deref(),
@@ -660,7 +661,7 @@ impl Config {
         // Databricks borrows api_key as the *optional* `DATABRICKS_TOKEN` escape
         // hatch — empty means "use OAuth PKCE." Legacy Databricks encodes the
         // model in the URL path; Databricks v2 keeps it in the request body.
-        let (api_key, model, base_url, openai_api) = match provider {
+        let (api_key, model, openai_api) = match provider {
             Provider::Anthropic => (
                 req("ANTHROPIC_API_KEY")?,
                 resolve_model(
@@ -668,7 +669,6 @@ impl Config {
                     env("ANTHROPIC_MODEL").as_deref(),
                 )
                 .ok_or_else(|| "config: ANTHROPIC_MODEL required".to_string())?,
-                env_or("ANTHROPIC_BASE_URL", "https://api.anthropic.com"),
                 OpenAiApi::Auto, // unused for Anthropic
             ),
             Provider::OpenAi => (
@@ -678,14 +678,12 @@ impl Config {
                     env("OPENAI_COMPAT_MODEL").as_deref(),
                 )
                 .ok_or_else(|| "config: OPENAI_COMPAT_MODEL required".to_string())?,
-                env_or("OPENAI_COMPAT_BASE_URL", "https://api.openai.com/v1"),
                 parse_openai_api(env("OPENAI_COMPAT_API").as_deref())?,
             ),
             Provider::Databricks | Provider::DatabricksV2 => (
                 env("DATABRICKS_TOKEN").unwrap_or_default(),
                 resolve_model(buzz_agent_model.as_deref(), databricks_model.as_deref())
                     .ok_or_else(|| "config: DATABRICKS_MODEL required".to_string())?,
-                databricks_host.ok_or_else(|| "config: DATABRICKS_HOST required".to_string())?,
                 OpenAiApi::Chat, // only read by OpenAI/legacy Databricks dispatch
             ),
             Provider::OpenRouter => (
@@ -695,10 +693,10 @@ impl Config {
                     env("OPENROUTER_MODEL").as_deref(),
                 )
                 .ok_or_else(|| "config: OPENROUTER_MODEL required".to_string())?,
-                env_or("OPENROUTER_BASE_URL", "https://openrouter.ai/api/v1"),
                 OpenAiApi::Chat, // OpenRouter uses Chat Completions only
             ),
         };
+        let base_url = endpoint::provider_base_url(&provider, env)?;
         let system_prompt = match (env("BUZZ_AGENT_SYSTEM_PROMPT"), env("BUZZ_AGENT_SYSTEM_PROMPT_FILE")) {
             (Some(_), Some(_)) => return Err(
                 "config: BUZZ_AGENT_SYSTEM_PROMPT and BUZZ_AGENT_SYSTEM_PROMPT_FILE are mutually exclusive".into()),

crates/buzz-agent/src/config/endpoint.rs

@@ -0,0 +1,65 @@
+//! Endpoint resolution shared by agent startup and desktop security suggestions.
+use super::Provider;
+
+pub fn provider_base_url(
+    provider: &Provider,
+    lookup: impl Fn(&str) -> Option<String>,
+) -> Result<String, String> {
+    let (key, default) = match provider {
+        Provider::Anthropic => ("ANTHROPIC_BASE_URL", Some("https://api.anthropic.com")),
+        Provider::OpenAi => ("OPENAI_COMPAT_BASE_URL", Some("https://api.openai.com/v1")),
+        Provider::OpenRouter => ("OPENROUTER_BASE_URL", Some("https://openrouter.ai/api/v1")),
+        Provider::Databricks | Provider::DatabricksV2 => ("DATABRICKS_HOST", None),
+    };
+    lookup(key)
+        .or_else(|| default.map(str::to_owned))
+        .ok_or_else(|| format!("config: {key} required"))
+}
+
+/// Resolve without fetching credentials, signing in, or making network requests.
+pub fn configured_endpoint(lookup: impl Fn(&str) -> Option<String>) -> Option<String> {
+    let provider = super::resolve_provider(
+        lookup("BUZZ_AGENT_PROVIDER").as_deref(),
+        Some("configured"),
+        Some("configured"),
+        Some("configured"),
+    )
+    .ok()?;
+    provider_base_url(&provider, lookup).ok()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn endpoints_follow_selected_provider_and_overrides() {
+        for (provider, expected) in [
+            ("anthropic", "https://api.anthropic.com"),
+            ("openai-compat", "https://api.openai.com/v1"),
+            ("openrouter", "https://openrouter.ai/api/v1"),
+        ] {
+            assert_eq!(
+                configured_endpoint(|key| (key == "BUZZ_AGENT_PROVIDER").then(|| provider.into()))
+                    .as_deref(),
+                Some(expected)
+            );
+        }
+        assert_eq!(
+            configured_endpoint(|key| match key {
+                "BUZZ_AGENT_PROVIDER" => Some("databricks_v2".into()),
+                "DATABRICKS_HOST" => Some("https://workspace.example.com".into()),
+                _ => None,
+            })
+            .as_deref(),
+            Some("https://workspace.example.com")
+        );
+        assert!(configured_endpoint(|_| None).is_none());
+        assert_eq!(
+            provider_base_url(&Provider::OpenAi, |_| Some(
+                "http://localhost:1234/v1".into()
+            ))
+            .unwrap(),
+            "http://localhost:1234/v1"
+        );
+    }
+}