🤖 feat: interactive harness init approval flow

docs/agents/index.mdx

@@ -405,6 +405,82 @@ You are in Explore mode (read-only).
 
 </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
+tools:
+  remove:
+    - web_search
+    - web_fetch
+    - google_search
+---
+
+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 ===
+Harness schema + output path:
+
+- The `.mux/harness/*.jsonc` schema is provided in the system prompt as `<harness_config_schema>`.
+- The required harness output file path is provided as `<harness_output_path>` (derived from `MUX_WORKSPACE_NAME`).
+- Follow the schema exactly (extra/unknown keys will fail validation).
+
+- Write the final harness config to the exact `<harness_output_path>` file.
+  - Do NOT invent filenames.
+  - Create/edit ONLY that one harness file (no extra drafts).
+
+- Web tools are disabled in this mode; do not attempt to look up harness docs online.
+
+- You may ONLY create/edit files under: `.mux/harness/**/*.jsonc`
+- If you delegate to read-only `explore` subagents, instruct them to avoid web_search/web_fetch/google_search too.
+
+- 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.
+
+=== REQUIRED WORKFLOW ===
+
+1. Start by spawning 1-4 read-only `explore` subagents via `task` with `agentId: "explore"`.
+   - Keep each prompt focused (e.g. CI/workflows, Make targets, tests, etc.).
+   - Tell them to avoid web_search/web_fetch/google_search.
+   - Wait for all reports before writing the harness file.
+
+   Suggested prompt template:
+   - Summarize repo-native gate entrypoints (Makefile, package.json scripts, .github/workflows/\*).
+   - Recommend:
+     - Checklist items (short titles + optional notes)
+     - Gate commands (exact command strings + optional title/timeout)
+   - (Optional) include a fenced ```json draft with { "checklist": [...], "gates": [...] }
+
+2. Synthesize the explore reports into a single harness config (matching `<harness_config_schema>`) and write it to `<harness_output_path>`.
+
+Gates:
+
+- Prefer a small set of safe, single commands.
+- Do NOT use shell chaining, pipes, redirects, or quotes.
+
+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>
+
 ### Mux (internal)
 
 **Configure mux global behavior (system workspace)**
@@ -527,3 +603,7 @@ Example:
 
 - Scoped instructions in `AGENTS.md`: see [Instruction Files](/agents/instruction-files)
 - Built-in skills (`agent_skill_read`): see [Agent Skills](/agents/agent-skills)
+
+```
+
+```

src/browser/components/ChatPane.tsx

@@ -549,6 +549,17 @@ 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}
@@ -648,6 +659,11 @@ 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}
                             userMessageNavigation={
                               msg.type === "user" && userMessageNavMap

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;
   /** Navigation info for user messages (backward/forward between user messages) */
@@ -40,6 +42,7 @@ export const MessageRenderer = React.memo<MessageRendererProps>(
     isCompacting,
     onReviewNote,
     isLatestProposePlan,
+    isLatestProposeHarness,
     bashOutputGroup,
     userMessageNavigation,
   }) => {
@@ -72,6 +75,7 @@ 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