diff --git a/desktop/src-tauri/src/managed_agents/agent_env.rs b/desktop/src-tauri/src/managed_agents/agent_env.rs
index 05979e76cb..af3850503c 100644
--- a/desktop/src-tauri/src/managed_agents/agent_env.rs
+++ b/desktop/src-tauri/src/managed_agents/agent_env.rs
@@ -148,6 +148,48 @@ mod tests {
         );
     }
 
+    /// The regression that routed an OpenAI agent's traffic to Anthropic.
+    ///
+    /// Desktop inherits the developer's login shell, so `GOOSE_PROVIDER` from
+    /// an installed goose reached the agent subprocess and beat the record's
+    /// configured provider. Spawn must clear the derived keys before writing
+    /// the ones it derives, so the record is the only source.
+    ///
+    /// Uses `env` as the child rather than reaching into `spawn_agent_child`
+    /// (which needs an `AppHandle`): the assertion is about what survives to
+    /// the child's environment, which is exactly what `env` prints.
+    #[test]
+    fn spawn_clears_inherited_provider_and_model_before_deriving_its_own() {
+        let mut cmd = std::process::Command::new("env");
+        cmd.env_clear();
+        // Stand in for the inherited login-shell environment.
+        for key in super::super::env_vars::DERIVED_PROVIDER_MODEL_ENV_KEYS {
+            cmd.env(key, "inherited-from-login-shell");
+        }
+
+        // The clearing step under test, mirrored from `spawn_agent_child`.
+        for key in super::super::env_vars::DERIVED_PROVIDER_MODEL_ENV_KEYS {
+            cmd.env_remove(key);
+        }
+        // Then the record's own values, as `runtime_metadata_env_vars` writes.
+        cmd.env("BUZZ_AGENT_PROVIDER", "openai");
+        cmd.env("BUZZ_AGENT_MODEL", "gpt-5.6-sol");
+
+        let output = cmd.output().expect("env should run");
+        let stdout = String::from_utf8_lossy(&output.stdout);
+
+        assert!(
+            !stdout.contains("inherited-from-login-shell"),
+            "no inherited provider/model value may reach the agent: {stdout}"
+        );
+        assert!(stdout.contains("BUZZ_AGENT_PROVIDER=openai"));
+        assert!(stdout.contains("BUZZ_AGENT_MODEL=gpt-5.6-sol"));
+        // An agent with no configured provider must get none at all, rather
+        // than silently inheriting the developer's.
+        assert!(!stdout.contains("GOOSE_PROVIDER="));
+        assert!(!stdout.contains("GOOSE_MODEL="));
+    }
+
     #[test]
     fn parse_agent_env_lines_splits_on_first_equals() {
         // Value may itself contain `=` — only the first `=` is the separator.
diff --git a/desktop/src-tauri/src/managed_agents/runtime.rs b/desktop/src-tauri/src/managed_agents/runtime.rs
index 51f03c1077..66180e01cb 100644
--- a/desktop/src-tauri/src/managed_agents/runtime.rs
+++ b/desktop/src-tauri/src/managed_agents/runtime.rs
@@ -6,10 +6,10 @@ use super::agent_env::build_buzz_agent_provider_defaults;
 
 use crate::{
     managed_agents::{
-        append_log_marker, known_acp_runtime, login_shell_path, managed_agent_log_path,
-        missing_command_message, normalize_agent_args, open_log_file, resolve_command,
-        spawn_key_refusal, KnownAcpRuntime, ManagedAgentPairRuntime, ManagedAgentRecord,
-        ManagedAgentRuntimeKey, ManagedAgentSummary,
+        append_log_marker, env_vars::DERIVED_PROVIDER_MODEL_ENV_KEYS, known_acp_runtime,
+        login_shell_path, managed_agent_log_path, missing_command_message, normalize_agent_args,
+        open_log_file, resolve_command, spawn_key_refusal, KnownAcpRuntime,
+        ManagedAgentPairRuntime, ManagedAgentRecord, ManagedAgentRuntimeKey, ManagedAgentSummary,
     },
     util::now_iso,
 };
@@ -740,6 +740,23 @@ pub fn spawn_agent_child(
         resolve_session_title(record.display_name.as_deref(), &record.name),
     );
     build_buzz_agent_provider_defaults(&mut command);
+    // Clear inherited provider/model keys before deriving this agent's own.
+    //
+    // `DERIVED_PROVIDER_MODEL_ENV_KEYS` are refused at save time so a stale
+    // override cannot shadow the record's structured provider/model fields.
+    // That guard only covers env we *persist*: the child still inherits this
+    // process's environment, and Desktop inherits the user's login shell.
+    // A developer with goose installed exports `GOOSE_PROVIDER` there, and it
+    // reached the agent as if it were configuration — an agent set to OpenAI
+    // sent its OpenAI model to Anthropic and 404'd every turn while its
+    // settings still read "OpenAI" in the UI.
+    //
+    // Removing them here makes the record the only source: whatever
+    // `runtime_metadata_env_vars` derives below is what the child sees, and an
+    // agent with no configured provider gets none rather than the developer's.
+    for key in DERIVED_PROVIDER_MODEL_ENV_KEYS {
+        command.env_remove(key);
+    }
     if let Some(meta) = runtime_meta {
         for (key, value) in runtime_metadata_env_vars(
             meta.model_env_var,