feat: first class Ollama provider via OLLAMA_HOST

rust/crates/api/src/client.rs

@@ -32,16 +32,23 @@ impl ProviderClient {
                 OpenAiCompatConfig::xai(),
             )?)),
             ProviderKind::OpenAi => {
-                // DashScope models (qwen-*) also return ProviderKind::OpenAi because they
-                // speak the OpenAI wire format, but they need the DashScope config which
-                // reads DASHSCOPE_API_KEY and points at dashscope.aliyuncs.com.
-                let config = match providers::metadata_for_model(&resolved_model) {
-                    Some(meta) if meta.auth_env == "DASHSCOPE_API_KEY" => {
-                        OpenAiCompatConfig::dashscope()
-                    }
-                    _ => OpenAiCompatConfig::openai(),
-                };
-                Ok(Self::OpenAi(OpenAiCompatClient::from_env(config)?))
+                if std::env::var_os("OLLAMA_HOST").is_some() {
+                    // unwrap is safe: from_ollama_env always returns Some
+                    Ok(Self::OpenAi(
+                        openai_compat::OpenAiCompatClient::from_ollama_env().unwrap(),
+                    ))
+                } else {
+                    // DashScope models (qwen-*) also return ProviderKind::OpenAi because they
+                    // speak the OpenAI wire format, but they need the DashScope config which
+                    // reads DASHSCOPE_API_KEY and points at dashscope.aliyuncs.com.
+                    let config = match providers::metadata_for_model(&resolved_model) {
+                        Some(meta) if meta.auth_env == "DASHSCOPE_API_KEY" => {
+                            OpenAiCompatConfig::dashscope()
+                        }
+                        _ => OpenAiCompatConfig::openai(),
+                    };
+                    Ok(Self::OpenAi(OpenAiCompatClient::from_env(config)?))
+                }
             }
         }
     }

rust/crates/api/src/providers/mod.rs

@@ -339,6 +339,10 @@ pub fn provider_diagnostics_for_model(model: &str) -> ProviderDiagnostics {
 
 #[must_use]
 pub fn detect_provider_kind(model: &str) -> ProviderKind {
+    if std::env::var_os("OLLAMA_HOST").is_some() {
+        return ProviderKind::OpenAi;
+    }
+
     if let Some(metadata) = metadata_for_model(model) {
         return metadata.provider;
     }

rust/crates/api/src/providers/openai_compat.rs

@@ -48,6 +48,14 @@ const XAI_MAX_REQUEST_BODY_BYTES: usize = 52_428_800; // 50MB
 const OPENAI_MAX_REQUEST_BODY_BYTES: usize = 104_857_600; // 100MB
 const DASHSCOPE_MAX_REQUEST_BODY_BYTES: usize = 6_291_456; // 6MB (observed limit in dogfood)
 
+pub const OLLAMA_CONFIG: OpenAiCompatConfig = OpenAiCompatConfig {
+    provider_name: "Ollama",
+    api_key_env: "OLLAMA_HOST",
+    base_url_env: "OLLAMA_HOST",
+    default_base_url: "http://127.0.0.1:11434/v1",
+    max_request_body_bytes: 104_857_600,
+};
+
 impl OpenAiCompatConfig {
     #[must_use]
     pub const fn xai() -> Self {
@@ -140,6 +148,21 @@ impl OpenAiCompatClient {
         Ok(Self::new(api_key, config))
     }
 
+    pub fn from_ollama_env() -> Option<Self> {
+        let host =
+            std::env::var("OLLAMA_HOST").unwrap_or_else(|_| "http://127.0.0.1:11434".to_string());
+        let base_url = format!("{}/v1", host.trim_end_matches('/'));
+        Some(Self {
+            http: build_http_client_or_default(),
+            api_key: "ollama".to_string(),
+            config: OLLAMA_CONFIG,
+            base_url,
+            max_retries: DEFAULT_MAX_RETRIES,
+            initial_backoff: DEFAULT_INITIAL_BACKOFF,
+            max_backoff: DEFAULT_MAX_BACKOFF,
+        })
+    }
+
     #[must_use]
     pub fn with_base_url(mut self, base_url: impl Into<String>) -> Self {
         self.base_url = base_url.into();

rust/crates/rusty-claude-cli/src/main.rs

@@ -1991,6 +1991,12 @@ fn resolve_model_alias_with_config(model: &str) -> String {
 /// Rejects: empty, whitespace-only, strings with spaces, or invalid chars.
 fn validate_model_syntax(model: &str) -> Result<(), String> {
     let trimmed = model.trim();
+    if std::env::var_os("OLLAMA_HOST").is_some() {
+        if trimmed.is_empty() {
+            return Err("invalid model syntax: model string cannot be empty.\nUsage: --model <provider/model>  e.g. --model anthropic/claude-opus-4-7".to_string());
+        }
+        return Ok(());
+    }
     if trimmed.is_empty() {
         return Err("invalid model syntax: model string cannot be empty.\nUsage: --model <provider/model>  e.g. --model anthropic/claude-opus-4-7".to_string());
     }
@@ -16659,4 +16665,15 @@ mod alias_resolution_tests {
         assert_eq!(resolve_model_alias_with_config(model), model);
         assert!(validate_model_syntax(model).is_ok());
     }
+
+    #[test]
+    fn test_ollama_host_bypasses_provider_model_validation() {
+        // Safety: test sets and clears env var within the test.
+        // May be flaky if tests run in parallel with conflicting OLLAMA_HOST usage,
+        // but acceptable for a unit-level smoke test.
+        std::env::set_var("OLLAMA_HOST", "http://127.0.0.1:11434");
+        let result = validate_model_syntax("qwen2.5-coder:7b");
+        std::env::remove_var("OLLAMA_HOST");
+        assert!(result.is_ok());
+    }
 }