🤖 feat: add ESLint rule to enforce folder boundaries

Add 'no-cross-boundary-imports' rule to prevent architectural violations:
- browser/ cannot import from node/
- node/ cannot import from desktop/ or cli/
- cli/ cannot import from browser/
- desktop/ cannot import from browser/
- All folders can import from common/
- Type-only imports allowed for DI patterns

Fixes all 17 violations by moving shared code to common/:
- Move telemetry module (browser-only PostHog client)
- Move git utilities (pure parsers, no Node dependencies)
- Move error formatting utilities
- Move compaction utilities (uses localStorage/window.api)
- Move mode utilities (pure logic)
- Create common model defaults for CLI use

_Generated with `mux`_

Author: kylecarbs

eslint.config.mjs

@@ -106,6 +106,93 @@ const localPlugin = {
         };
       },
     },
+    "no-cross-boundary-imports": {
+      meta: {
+        type: "problem",
+        docs: {
+          description: "Enforce folder boundaries to prevent architectural violations",
+        },
+        messages: {
+          browserToNode:
+            "browser/ cannot import from node/. Move shared code to common/ or use IPC.",
+          nodeToDesktop:
+            "node/ cannot import from desktop/. Move shared code to common/ or use dependency injection.",
+          nodeToCli:
+            "node/ cannot import from cli/. Move shared code to common/.",
+          cliToBrowser:
+            "cli/ cannot import from browser/. Move shared code to common/.",
+          desktopToBrowser:
+            "desktop/ cannot import from browser/. Move shared code to common/.",
+        },
+      },
+      create(context) {
+        return {
+          ImportDeclaration(node) {
+            // Allow type-only imports (for DI patterns)
+            if (node.importKind === "type") {
+              return;
+            }
+
+            const sourceFile = context.filename;
+            const importPath = node.source.value;
+
+            // Extract folder from source file (browser, node, desktop, cli, common)
+            const sourceFolderMatch = sourceFile.match(/\/src\/(browser|node|desktop|cli|common)\//);
+            if (!sourceFolderMatch) return;
+            const sourceFolder = sourceFolderMatch[1];
+
+            // Extract folder from import target
+            // Handle relative imports (e.g., '../node/...')
+            let targetFolder = null;
+            if (importPath.startsWith("../")) {
+              const targetMatch = importPath.match(/\.\.\/(browser|node|desktop|cli|common)\//);
+              if (targetMatch) {
+                targetFolder = targetMatch[1];
+              }
+            } else if (importPath.startsWith("@/")) {
+              // Handle alias imports (e.g., '@/node/...')
+              const targetMatch = importPath.match(/@\/(browser|node|desktop|cli|common)\//);
+              if (targetMatch) {
+                targetFolder = targetMatch[1];
+              }
+            }
+
+            if (!targetFolder) return;
+
+            // Allow imports from common
+            if (targetFolder === "common") return;
+
+            // Check for violations
+            if (sourceFolder === "browser" && targetFolder === "node") {
+              context.report({
+                node,
+                messageId: "browserToNode",
+              });
+            } else if (sourceFolder === "node" && targetFolder === "desktop") {
+              context.report({
+                node,
+                messageId: "nodeToDesktop",
+              });
+            } else if (sourceFolder === "node" && targetFolder === "cli") {
+              context.report({
+                node,
+                messageId: "nodeToCli",
+              });
+            } else if (sourceFolder === "cli" && targetFolder === "browser") {
+              context.report({
+                node,
+                messageId: "cliToBrowser",
+              });
+            } else if (sourceFolder === "desktop" && targetFolder === "browser") {
+              context.report({
+                node,
+                messageId: "desktopToBrowser",
+              });
+            }
+          },
+        };
+      },
+    },
   },
 };
 
@@ -265,6 +352,7 @@ export default defineConfig([
       // Safe Node.js patterns
       "local/no-unsafe-child-process": "error",
       "local/no-sync-fs-methods": "error",
+      "local/no-cross-boundary-imports": "error",
 
       // Allow console for this app (it's a dev tool)
       "no-console": "off",
@@ -410,6 +498,8 @@ export default defineConfig([
       // This file is only used by Node.js code (cli/debug) but lives in common/
       // TODO: Consider moving to node/utils/
       "src/common/utils/providers/ensureProvidersConfig.ts",
+      // Telemetry uses defensive process checks for test environments
+      "src/common/telemetry/**",
     ],
     rules: {
       "no-restricted-globals": [

src/browser/components/ChatInput/index.tsx

@@ -58,7 +58,7 @@ import {
 import type { ThinkingLevel } from "@/common/types/thinking";
 import type { MuxFrontendMetadata } from "@/common/types/message";
 import { useTelemetry } from "@/browser/hooks/useTelemetry";
-import { setTelemetryEnabled } from "@/node/telemetry";
+import { setTelemetryEnabled } from "@/common/telemetry";
 import { getTokenCountPromise } from "@/browser/utils/tokenizer/rendererClient";
 import { CreationCenterContent } from "./CreationCenterContent";
 import { CreationControls } from "./CreationControls";

src/browser/components/ChatInputToasts.tsx

@@ -3,7 +3,7 @@ import type { Toast } from "./ChatInputToast";
 import { SolutionLabel } from "./ChatInputToast";
 import type { ParsedCommand } from "@/browser/utils/slashCommands/types";
 import type { SendMessageError as SendMessageErrorType } from "@/common/types/errors";
-import { formatSendMessageError } from "@/node/utils/errors/formatSendError";
+import { formatSendMessageError } from "@/common/utils/errors/formatSendError";
 
 /**
  * Creates a toast message for command-related errors and help messages

src/browser/components/GitStatusIndicatorView.stories.tsx

@@ -1,7 +1,7 @@
 import type { Meta, StoryObj } from "@storybook/react-vite";
 import { expect, userEvent, waitFor } from "storybook/test";
 import { GitStatusIndicatorView } from "./GitStatusIndicatorView";
-import type { GitCommit, GitBranchHeader } from "@/node/utils/git/parseGitLog";
+import type { GitCommit, GitBranchHeader } from "@/common/utils/git/parseGitLog";
 import { useState } from "react";
 
 // Type for the wrapped component props (without interaction handlers)

src/browser/components/GitStatusIndicatorView.tsx

@@ -1,7 +1,7 @@
 import React from "react";
 import { createPortal } from "react-dom";
 import type { GitStatus } from "@/common/types/workspace";
-import type { GitCommit, GitBranchHeader } from "@/node/utils/git/parseGitLog";
+import type { GitCommit, GitBranchHeader } from "@/common/utils/git/parseGitLog";
 import { cn } from "@/common/lib/utils";
 
 // Helper for indicator colors

src/browser/components/Messages/ChatBarrier/RetryBarrier.tsx

@@ -9,7 +9,7 @@ import {
   isEligibleForAutoRetry,
   isNonRetryableSendError,
 } from "@/browser/utils/messages/retryEligibility";
-import { formatSendMessageError } from "@/node/utils/errors/formatSendError";
+import { formatSendMessageError } from "@/common/utils/errors/formatSendError";
 import { createManualRetryState, calculateBackoffDelay } from "@/browser/utils/messages/retryState";
 
 interface RetryBarrierProps {

src/browser/components/RightSidebar/CodeReview/FileTree.tsx

@@ -3,7 +3,7 @@
  */
 
 import React from "react";
-import type { FileTreeNode } from "@/node/utils/git/numstatParser";
+import type { FileTreeNode } from "@/common/utils/git/numstatParser";
 import { usePersistedState } from "@/browser/hooks/usePersistedState";
 import { getFileTreeExpandStateKey } from "@/common/constants/storage";
 import { cn } from "@/common/lib/utils";

src/browser/components/RightSidebar/CodeReview/ReviewPanel.tsx

@@ -28,12 +28,12 @@ import { ReviewControls } from "./ReviewControls";
 import { FileTree } from "./FileTree";
 import { usePersistedState } from "@/browser/hooks/usePersistedState";
 import { useReviewState } from "@/browser/hooks/useReviewState";
-import { parseDiff, extractAllHunks } from "@/node/utils/git/diffParser";
+import { parseDiff, extractAllHunks } from "@/common/utils/git/diffParser";
 import { getReviewSearchStateKey } from "@/common/constants/storage";
 import { Tooltip, TooltipWrapper } from "@/browser/components/Tooltip";
-import { parseNumstat, buildFileTree, extractNewPath } from "@/node/utils/git/numstatParser";
+import { parseNumstat, buildFileTree, extractNewPath } from "@/common/utils/git/numstatParser";
 import type { DiffHunk, ReviewFilters as ReviewFiltersType } from "@/common/types/review";
-import type { FileTreeNode } from "@/node/utils/git/numstatParser";
+import type { FileTreeNode } from "@/common/utils/git/numstatParser";
 import { matchesKeybind, KEYBINDS, formatKeybind } from "@/browser/utils/ui/keybinds";
 import { applyFrontendFilters } from "@/browser/utils/review/filterHunks";
 import { cn } from "@/common/lib/utils";

src/browser/components/TitleBar.tsx

@@ -3,7 +3,7 @@ import { cn } from "@/common/lib/utils";
 import { VERSION } from "@/version";
 import { TooltipWrapper, Tooltip } from "./Tooltip";
 import type { UpdateStatus } from "@/common/types/ipc";
-import { isTelemetryEnabled } from "@/node/telemetry";
+import { isTelemetryEnabled } from "@/common/telemetry";
 
 // Update check intervals
 const UPDATE_CHECK_INTERVAL_MS = 4 * 60 * 60 * 1000; // 4 hours

src/browser/components/hooks/useGitBranchDetails.ts

@@ -5,7 +5,7 @@ import {
   parseGitShowBranch,
   type GitCommit,
   type GitBranchHeader,
-} from "@/node/utils/git/parseGitLog";
+} from "@/common/utils/git/parseGitLog";
 
 const GitBranchDataSchema = z.object({
   showBranch: z.string(),