🤖 feat: interactive harness init approval flow

Change-Id: Icf5963d92a65300117de0c264272f8ca3952c4e0
Signed-off-by: Thomas Kosiewski <tk@coder.com>

Author: ThomasK33

docs/agents/index.mdx

@@ -441,6 +441,58 @@ Example JSON object:
 
 </Accordion>
 
+### Harness Init (internal)
+
+**Interactive harness generation + approval (internal)**
+
+<Accordion title="View harness-init.md">
+
+```md
+---
+name: Harness Init
+description: Interactive harness generation + approval (internal)
+base: exec
+ui:
+  hidden: true
+  color: var(--color-harness-init-mode)
+subagent:
+  runnable: false
+---
+
+You are in Harness Init mode.
+
+Your job is to create or refine a Ralph harness for this workspace based on the current plan and the repository.
+
+=== CRITICAL: LIMITED EDIT MODE ===
+
+- You may ONLY create/edit files under: `.mux/harness/*.jsonc`
+- Do NOT modify source code or other repo files.
+- Use bash only for read-only investigation (rg, ls, cat, git diff/show/log, etc.).
+  - No redirects/heredocs, no installs, no git add/commit, no rm/mv/cp/mkdir/touch.
+
+Repo-aware investigation:
+
+- Identify which commands should be used as gates by checking repo-native entrypoints:
+  - `Makefile`, `package.json` scripts, `.github/workflows/*`, etc.
+- Map the plan’s changes to impacted subsystems by tracing callsites/imports.
+
+Gates:
+
+- Prefer a small set of safe, single commands.
+- Do NOT use shell chaining, pipes, redirects, or quotes.
+
+Delegation:
+
+- You may spawn only read-only exploration subagents via `task` with `agentId: "explore"`.
+
+When the harness file is ready for user review:
+
+- Call `propose_harness` exactly once.
+- Do NOT start the Ralph loop yourself; the UI will start it after user approval.
+```
+
+</Accordion>
+
 {/* END BUILTIN_AGENTS */}
 
 ## Related Docs

src/browser/components/ChatInput/index.tsx

@@ -2480,9 +2480,11 @@ const ChatInputInner: React.FC<ChatInputProps> = (props) => {
                       aria-label="Send message"
                       className={cn(
                         "inline-flex items-center gap-1 rounded-sm border border-border-light px-1.5 py-0.5 text-[11px] font-medium text-white transition-colors duration-200 disabled:opacity-50",
-                        mode === "plan"
-                          ? "bg-plan-mode hover:bg-plan-mode-hover disabled:hover:bg-plan-mode"
-                          : "bg-exec-mode hover:bg-exec-mode-hover disabled:hover:bg-exec-mode"
+                        agentId === "harness-init"
+                          ? "bg-harness-init-mode hover:bg-harness-init-mode-hover disabled:hover:bg-harness-init-mode"
+                          : mode === "plan"
+                            ? "bg-plan-mode hover:bg-plan-mode-hover disabled:hover:bg-plan-mode"
+                            : "bg-exec-mode hover:bg-exec-mode-hover disabled:hover:bg-exec-mode"
                       )}
                     >
                       <SendHorizontal className="h-3.5 w-3.5" strokeWidth={2.5} />

src/browser/components/ChatPane.tsx

@@ -527,6 +527,17 @@ export const ChatPane: React.FC<ChatPaneProps> = (props) => {
     }
   }
 
+  // Find the ID of the latest propose_harness tool call for external edit detection
+  // Only the latest harness should fetch fresh content from disk
+  let latestProposeHarnessId: string | null = null;
+  for (let i = transformedMessages.length - 1; i >= 0; i--) {
+    const msg = transformedMessages[i];
+    if (msg.type === "tool" && msg.toolName === "propose_harness") {
+      latestProposeHarnessId = msg.id;
+      break;
+    }
+  }
+
   return (
     <div
       ref={chatAreaRef}
@@ -625,6 +636,11 @@ export const ChatPane: React.FC<ChatPaneProps> = (props) => {
                               msg.toolName === "propose_plan" &&
                               msg.id === latestProposePlanId
                             }
+                            isLatestProposeHarness={
+                              msg.type === "tool" &&
+                              msg.toolName === "propose_harness" &&
+                              msg.id === latestProposeHarnessId
+                            }
                             bashOutputGroup={bashOutputGroup}
                           />
                         </div>

src/browser/components/Messages/MessageRenderer.tsx

@@ -24,6 +24,8 @@ interface MessageRendererProps {
   onReviewNote?: (data: ReviewNoteData) => void;
   /** Whether this message is the latest propose_plan tool call (for external edit detection) */
   isLatestProposePlan?: boolean;
+  /** Whether this message is the latest propose_harness tool call (for external edit detection) */
+  isLatestProposeHarness?: boolean;
   /** Optional bash_output grouping info (computed at render-time) */
   bashOutputGroup?: BashOutputGroupInfo;
 }
@@ -38,6 +40,7 @@ export const MessageRenderer = React.memo<MessageRendererProps>(
     isCompacting,
     onReviewNote,
     isLatestProposePlan,
+    isLatestProposeHarness,
     bashOutputGroup,
   }) => {
     // Route based on message type
@@ -68,6 +71,7 @@ export const MessageRenderer = React.memo<MessageRendererProps>(
             workspaceId={workspaceId}
             onReviewNote={onReviewNote}
             isLatestProposePlan={isLatestProposePlan}
+            isLatestProposeHarness={isLatestProposeHarness}
             bashOutputGroup={bashOutputGroup}
           />
         );

src/browser/components/Messages/ToolMessage.tsx

@@ -17,6 +17,8 @@ interface ToolMessageProps {
   onReviewNote?: (data: ReviewNoteData) => void;
   /** Whether this is the latest propose_plan in the conversation */
   isLatestProposePlan?: boolean;
+  /** Whether this is the latest propose_harness in the conversation */
+  isLatestProposeHarness?: boolean;
   /** Optional bash_output grouping info */
   bashOutputGroup?: BashOutputGroupInfo;
 }
@@ -27,6 +29,7 @@ export const ToolMessage: React.FC<ToolMessageProps> = ({
   workspaceId,
   onReviewNote,
   isLatestProposePlan,
+  isLatestProposeHarness,
   bashOutputGroup,
 }) => {
   const { toolName, args, result, status, toolCallId } = message;
@@ -40,6 +43,12 @@ export const ToolMessage: React.FC<ToolMessageProps> = ({
       ? bashOutputGroup.position
       : undefined;
 
+  const isLatest =
+    toolName === "propose_plan"
+      ? isLatestProposePlan
+      : toolName === "propose_harness"
+        ? isLatestProposeHarness
+        : undefined;
   // Extract hook output if present (only shown when hook produced output)
   const hookOutput = extractHookOutput(result);
   const hookDuration = extractHookDuration(result);
@@ -59,8 +68,8 @@ export const ToolMessage: React.FC<ToolMessageProps> = ({
         startedAt={message.timestamp}
         // FileEdit-specific
         onReviewNote={onReviewNote}
-        // ProposePlan-specific
-        isLatest={isLatestProposePlan}
+        // ProposePlan/ProposeHarness-specific
+        isLatest={isLatest}
         // BashOutput-specific
         groupPosition={groupPosition}
         // CodeExecution-specific