fix(api): safely join api_url + path so misconfigured base can't corrupt routes (#1650)

src/api/config.rs

@@ -32,6 +32,43 @@ pub fn normalize_api_base_url(url: &str) -> String {
     url.trim().trim_end_matches('/').to_string()
 }
 
+/// Safely join an API base URL with a path.
+///
+/// Behaviour:
+/// - Empty `path` → normalized `base` (no trailing slash).
+/// - `path` starting with `/` → replaces any path on `base` (RFC 3986
+///   absolute-path reference). This is the case that protects us from a
+///   misconfigured `api_url` like `https://api.tinyhumans.ai/openai/v1/chat/completions`
+///   silently corrupting every `/agent-integrations/...` call.
+/// - If `base` fails to parse as a URL, falls back to slash-safe concat
+///   so callers always get a usable string.
+///
+/// Paths SHOULD start with `/`. Relative paths (no leading slash) are
+/// resolved against the base path per RFC 3986, which means the base's
+/// last path segment is dropped — almost never what you want for an API.
+pub fn api_url(base: &str, path: &str) -> String {
+    let base_trimmed = base.trim();
+    if path.is_empty() {
+        return normalize_api_base_url(base_trimmed);
+    }
+    match url::Url::parse(base_trimmed) {
+        Ok(parsed) => match parsed.join(path) {
+            Ok(joined) => joined.to_string().trim_end_matches('/').to_string(),
+            Err(_) => fallback_concat(base_trimmed, path),
+        },
+        Err(_) => fallback_concat(base_trimmed, path),
+    }
+}
+
+fn fallback_concat(base: &str, path: &str) -> String {
+    let base = base.trim_end_matches('/');
+    if path.starts_with('/') {
+        format!("{base}{path}")
+    } else {
+        format!("{base}/{path}")
+    }
+}
+
 /// Resolve API base URL from the environment.
 ///
 /// Each key is checked independently so that an empty `BACKEND_URL` does not
@@ -117,6 +154,70 @@ mod tests {
     // parallel test execution (std::env is process-global).
     static ENV_LOCK: OnceLock<Mutex<()>> = OnceLock::new();
 
+    #[test]
+    fn api_url_empty_path_returns_normalized_base() {
+        assert_eq!(
+            api_url("https://api.tinyhumans.ai", ""),
+            "https://api.tinyhumans.ai"
+        );
+        assert_eq!(
+            api_url("https://api.tinyhumans.ai/", ""),
+            "https://api.tinyhumans.ai"
+        );
+        assert_eq!(
+            api_url("  https://api.tinyhumans.ai/  ", ""),
+            "https://api.tinyhumans.ai"
+        );
+    }
+
+    #[test]
+    fn api_url_absolute_path_replaces_base_path() {
+        // This is the regression: api_url misconfigured with a path baked in
+        // must not corrupt /agent-integrations/* calls.
+        assert_eq!(
+            api_url(
+                "https://api.tinyhumans.ai/openai/v1/chat/completions",
+                "/agent-integrations/composio/toolkits"
+            ),
+            "https://api.tinyhumans.ai/agent-integrations/composio/toolkits"
+        );
+    }
+
+    #[test]
+    fn api_url_clean_base_joins_cleanly() {
+        assert_eq!(
+            api_url(
+                "https://api.tinyhumans.ai",
+                "/agent-integrations/composio/toolkits"
+            ),
+            "https://api.tinyhumans.ai/agent-integrations/composio/toolkits"
+        );
+        assert_eq!(
+            api_url(
+                "https://api.tinyhumans.ai/",
+                "/agent-integrations/composio/toolkits"
+            ),
+            "https://api.tinyhumans.ai/agent-integrations/composio/toolkits"
+        );
+    }
+
+    #[test]
+    fn api_url_preserves_query_string_on_path() {
+        assert_eq!(
+            api_url(
+                "https://api.tinyhumans.ai",
+                "/agent-integrations/composio/tools?toolkits=gmail"
+            ),
+            "https://api.tinyhumans.ai/agent-integrations/composio/tools?toolkits=gmail"
+        );
+    }
+
+    #[test]
+    fn api_url_unparseable_base_falls_back_to_concat() {
+        assert_eq!(api_url("not a url", "/x"), "not a url/x");
+        assert_eq!(api_url("not a url/", "/x"), "not a url/x");
+    }
+
     #[test]
     fn staging_app_env_uses_staging_default_api() {
         assert_eq!(

src/openhuman/composio/client.rs

@@ -314,7 +314,7 @@ impl ComposioClient {
             error: Option<String>,
         }
 
-        let url = format!("{}{}", self.inner.backend_url, path);
+        let url = crate::api::config::api_url(&self.inner.backend_url, path);
         tracing::debug!("[composio] DELETE {}", url);
 
         // Build a fresh lightweight reqwest client for this DELETE.

src/openhuman/integrations/client.rs

@@ -78,7 +78,7 @@ impl IntegrationClient {
         path: &str,
         body: &serde_json::Value,
     ) -> anyhow::Result<T> {
-        let url = format!("{}{}", self.backend_url, path);
+        let url = crate::api::config::api_url(&self.backend_url, path);
         tracing::debug!("[integrations] POST {}", url);
 
         let resp = self
@@ -154,7 +154,7 @@ impl IntegrationClient {
 
     /// GET from a backend endpoint and parse the response `data` field.
     pub async fn get<T: serde::de::DeserializeOwned>(&self, path: &str) -> anyhow::Result<T> {
-        let url = format!("{}{}", self.backend_url, path);
+        let url = crate::api::config::api_url(&self.backend_url, path);
         tracing::debug!("[integrations] GET {}", url);
 
         let resp = self