huskies: merge 1100 bug Multiple LLM agents can run concurrently on the same story (coder + mergemaster + others) — enforce one-agent-per-story invariant

server/src/agents/pool/start/validation.rs

@@ -2,11 +2,11 @@
 
 use std::path::Path;
 
-use crate::config::ProjectConfig;
-use crate::pipeline_state::Stage;
-
-use super::super::super::{PipelineStage, agent_config_stage, pipeline_stage};
+use super::super::super::{
+    PipelineStage, agent_config_stage, canonical_pipeline_stage, pipeline_stage,
+};
 use super::super::worktree::find_active_story_stage;
+use crate::config::ProjectConfig;
 
 /// Validate that an explicit `agent_name` is allowed to attach to `story_id`'s
 /// current pipeline stage.
@@ -34,16 +34,15 @@ pub(super) fn validate_agent_stage(
     let Some(story_stage) = find_active_story_stage(project_root, story_id) else {
         return Ok(());
     };
-    let expected_stage = match story_stage {
-        Stage::Coding { .. } => PipelineStage::Coder,
-        Stage::Qa => PipelineStage::Qa,
-        Stage::Merge { .. } => PipelineStage::Mergemaster,
-        _ => PipelineStage::Other,
-    };
-    if expected_stage != PipelineStage::Other && expected_stage != agent_stage {
+    let canonical = canonical_pipeline_stage(&story_stage);
+    let is_llm = matches!(
+        agent_stage,
+        PipelineStage::Coder | PipelineStage::Qa | PipelineStage::Mergemaster
+    );
+    if is_llm && (canonical.is_none() || canonical.as_ref() != Some(&agent_stage)) {
         return Err(format!(
             "Agent '{name}' (stage: {agent_stage:?}) cannot be assigned to \
-             story '{story_id}' in {}/ (requires stage: {expected_stage:?})",
+             story '{story_id}' in {}/ (requires stage: {canonical:?})",
             story_stage.dir_name()
         ));
     }