feat(acp,desktop): identify and reap stale agent harness processes

crates/buzz-acp/src/lib.rs

@@ -2764,6 +2764,19 @@ fn handle_prompt_result(
         PromptOutcome::Cancelled => "cancelled",
     };
     let agent_index = result.agent.index;
+    // Capture the spawn-time configured model and our PID before the agent is
+    // moved into match arms below. `desired_model` reflects the config/persona
+    // model at spawn time — it does NOT reflect `session/set_model` overrides,
+    // which live in buzz-agent's session state and are what `llm: (model) …`
+    // errors carry. The two can legitimately differ; `configured_model=` is
+    // still valuable for identifying a stale orphan running an old model.
+    let harness_configured_model = result
+        .agent
+        .desired_model
+        .as_deref()
+        .unwrap_or("<none>")
+        .to_string();
+    let harness_pid = std::process::id();
 
     let channel_id = match &result.source {
         PromptSource::Channel(ch) => Some(*ch),
@@ -2798,6 +2811,8 @@ fn handle_prompt_result(
             tracing::warn!(
                 agent = agent_index,
                 outcome = outcome_label,
+                configured_model = %harness_configured_model,
+                pid = harness_pid,
                 "agent_returned — respawning"
             );
             let death_message = match outcome_label {
@@ -2842,6 +2857,8 @@ fn handle_prompt_result(
             tracing::debug!(
                 agent = agent_index,
                 outcome = outcome_label,
+                configured_model = %harness_configured_model,
+                pid = harness_pid,
                 "agent_returned (cancelled)"
             );
             pool.return_agent(result.agent);
@@ -2858,6 +2875,8 @@ fn handle_prompt_result(
                 tracing::warn!(
                     agent = agent_index,
                     outcome = outcome_label,
+                    configured_model = %harness_configured_model,
+                    pid = harness_pid,
                     error = %e,
                     "transport/protocol error — respawning agent"
                 );
@@ -2882,6 +2901,8 @@ fn handle_prompt_result(
                 tracing::warn!(
                     agent = agent_index,
                     outcome = outcome_label,
+                    configured_model = %harness_configured_model,
+                    pid = harness_pid,
                     error = %e,
                     "agent_returned (application error — pipe intact)"
                 );

crates/buzz-agent/src/llm.rs

@@ -72,7 +72,7 @@ impl Llm {
         effective_model: &str,
     ) -> Result<LlmResponse, AgentError> {
         let effort = cfg.thinking_effort;
-        match cfg.provider {
+        let result = match cfg.provider {
             Provider::Anthropic => {
                 let v = self
                     .post_anthropic(
@@ -140,7 +140,17 @@ impl Llm {
                 })
                 .await
             }
-        }
+        };
+        // Stamp the effective model into Llm errors so log lines carry
+        // `llm: (model-name) 404 Not Found: …` instead of the bare status.
+        // The `llm: ` prefix comes from `Display for AgentError::Llm`; the
+        // map_err here prepends `(model-name) ` to the inner string only.
+        // This is the single place all provider paths converge, so the mapping
+        // is centralized and never needs to be repeated in each provider arm.
+        result.map_err(|e| match e {
+            AgentError::Llm(s) => AgentError::Llm(format!("({effective_model}) {s}")),
+            other => other,
+        })
     }
 
     pub async fn summarize(

desktop/src-tauri/src/managed_agents/restore.rs

@@ -132,6 +132,17 @@ pub async fn restore_managed_agents_on_launch(
         // whose desktop process is no longer running and reap them.
         super::reap_dead_instance_agents(&super::current_instance_id(app), &tracked_pids);
 
+        // Exact-path sweep: kill any buzz-acp process whose executable path
+        // matches this bundle's harness binary but is not in the tracked set.
+        // Complements the env-var sweep above — catches orphans that predate
+        // BUZZ_MANAGED_AGENT injection or lost their PID-file receipt.
+        //
+        // TODO: the three sweeps above each walk the PID table independently.
+        // A future consolidation should collect a single shared process snapshot
+        // at the top of this block and thread it through all sweep functions,
+        // replacing the three separate kernel enumerations.
+        super::sweep_untracked_bundle_harnesses(&tracked_pids);
+
         let candidates: Vec<String> = records
             .iter()
             .filter(|record| record.start_on_app_launch && record.backend == BackendKind::Local)