refactor: reduce duplication and simplify codebase

src/client.ts

@@ -1,6 +1,6 @@
 import { sendToDaemon } from './daemon-client.ts';
 import { prepareMetroRuntime } from './client-metro.ts';
-import { AppError } from './utils/errors.ts';
+import { throwDaemonError } from './daemon-error.ts';
 import {
   buildFlags,
   buildMeta,
@@ -57,12 +57,7 @@ export function createAgentDeviceClient(
       meta: buildMeta(merged),
     });
     if (!response.ok) {
-      throw new AppError(response.error.code as any, response.error.message, {
-        ...(response.error.details ?? {}),
-        hint: response.error.hint,
-        diagnosticId: response.error.diagnosticId,
-        logPath: response.error.logPath,
-      });
+      throwDaemonError(response.error);
     }
     return (response.data ?? {}) as Record<string, unknown>;
   };

src/contracts.ts

@@ -1,5 +1,3 @@
-// Keep this public daemon contract shape aligned with MetroRuntimeHints in src/metro.ts
-// and the internal MetroRuntimeHints in src/client-metro.ts.
 export type SessionRuntimeHints = {
   platform?: 'ios' | 'android';
   metroHost?: string;

src/daemon-error.ts

@@ -0,0 +1,11 @@
+import { AppError } from './utils/errors.ts';
+import type { DaemonError } from './contracts.ts';
+
+export function throwDaemonError(error: DaemonError): never {
+  throw new AppError(error.code as any, error.message, {
+    ...(error.details ?? {}),
+    hint: error.hint,
+    diagnosticId: error.diagnosticId,
+    logPath: error.logPath,
+  });
+}

src/daemon/handlers/find.ts

@@ -194,7 +194,7 @@ async function handleFindWait(
     }
     await new Promise((resolve) => setTimeout(resolve, 300));
   }
-  return { ok: false, error: { code: 'COMMAND_FAILED', message: 'find wait timed out' } };
+  return errorResponse('COMMAND_FAILED', 'find wait timed out');
 }
 
 async function handleFindExists(ctx: FindContext): Promise<DaemonResponse> {
@@ -280,7 +280,7 @@ async function handleFindFill(
 ): Promise<DaemonResponse> {
   const { req, sessionName, sessionStore, session, invoke, command } = ctx;
   if (!value) {
-    return { ok: false, error: { code: 'INVALID_ARGS', message: 'find fill requires text' } };
+    return errorResponse('INVALID_ARGS', 'find fill requires text');
   }
   const response = await invoke({
     token: req.token,
@@ -305,10 +305,7 @@ async function handleFindFocus(ctx: FindContext, match: ResolvedMatch): Promise<
   const { req, sessionStore, session, device, command, logPath } = ctx;
   const coords = match.node.rect ? centerOfRect(match.node.rect) : null;
   if (!coords) {
-    return {
-      ok: false,
-      error: { code: 'COMMAND_FAILED', message: 'matched element has no bounds' },
-    };
+    return errorResponse('COMMAND_FAILED', 'matched element has no bounds');
   }
   const response = await dispatchCommand(
     device,
@@ -337,14 +334,11 @@ async function handleFindType(
 ): Promise<DaemonResponse> {
   const { req, sessionStore, session, device, command, logPath } = ctx;
   if (!value) {
-    return { ok: false, error: { code: 'INVALID_ARGS', message: 'find type requires text' } };
+    return errorResponse('INVALID_ARGS', 'find type requires text');
   }
   const coords = match.node.rect ? centerOfRect(match.node.rect) : null;
   if (!coords) {
-    return {
-      ok: false,
-      error: { code: 'COMMAND_FAILED', message: 'matched element has no bounds' },
-    };
+    return errorResponse('COMMAND_FAILED', 'matched element has no bounds');
   }
   await dispatchCommand(device, 'focus', [String(coords.x), String(coords.y)], req.flags?.out, {
     ...contextFromFlags(logPath, req.flags, session?.appBundleId, session?.trace?.outPath),
@@ -375,19 +369,16 @@ function buildAmbiguousMatchError(
       extractNodeText(candidate) || candidate.label || candidate.identifier || candidate.type || '';
     return `@${candidate.ref}${label ? `(${label})` : ''}`;
   });
-  return {
-    ok: false,
-    error: {
-      code: 'AMBIGUOUS_MATCH',
-      message: `find matched ${matches.length} elements for ${locator} "${query}". Use a more specific locator or selector.`,
-      details: {
-        locator,
-        query,
-        matches: matches.length,
-        candidates,
-      },
+  return errorResponse(
+    'AMBIGUOUS_MATCH',
+    `find matched ${matches.length} elements for ${locator} "${query}". Use a more specific locator or selector.`,
+    {
+      locator,
+      query,
+      matches: matches.length,
+      candidates,
     },
-  };
+  );
 }
 
 type FindAction =

src/daemon/handlers/handler-utils.ts

@@ -20,3 +20,34 @@ export function recordSessionAction(
     result: result ?? {},
   });
 }
+
+/**
+ * Flag keys inherited from a parent request (batch/replay) into child step flags.
+ * Shared between batch and replay so the inheritance rules stay in sync.
+ */
+export const INHERITED_PARENT_FLAG_KEYS: ReadonlyArray<keyof CommandFlags> = [
+  'platform',
+  'target',
+  'device',
+  'udid',
+  'serial',
+  'verbose',
+  'out',
+];
+
+/**
+ * Merge parent flag values into child flags for keys that are undefined in the child.
+ */
+export function mergeParentFlags(
+  parentFlags: CommandFlags | undefined,
+  childFlags: CommandFlags,
+): CommandFlags {
+  const parentRecord = (parentFlags ?? {}) as Record<string, unknown>;
+  const childRecord = childFlags as Record<string, unknown>;
+  for (const key of INHERITED_PARENT_FLAG_KEYS) {
+    if (childRecord[key] === undefined && parentRecord[key] !== undefined) {
+      childRecord[key] = parentRecord[key];
+    }
+  }
+  return childFlags;
+}

src/daemon/handlers/install-source.ts

@@ -13,6 +13,7 @@ import type { DaemonRequest, DaemonResponse, SessionState } from '../types.ts';
 import { resolveInstallFromSourceResultTarget } from '../../client-shared.ts';
 import { AppError, normalizeError } from '../../utils/errors.ts';
 import { withSuccessText } from '../../utils/success-text.ts';
+import { errorResponse } from './response.ts';
 
 function normalizePlatform(platform: CommandFlags['platform']): 'ios' | 'android' | undefined {
   return platform === 'ios' || platform === 'android' ? platform : undefined;
@@ -73,13 +74,10 @@ export async function handleInstallFromSourceCommand(params: {
       flags: req.flags,
     });
     if (!isCommandSupportedOnDevice('install', device)) {
-      return {
-        ok: false,
-        error: {
-          code: 'UNSUPPORTED_OPERATION',
-          message: 'install_from_source is not supported on this device',
-        },
-      };
+      return errorResponse(
+        'UNSUPPORTED_OPERATION',
+        'install_from_source is not supported on this device',
+      );
     }
 
     const requestSignal = getRequestSignal(req.meta?.requestId);

src/daemon/handlers/interaction-fill.ts

@@ -21,6 +21,7 @@ import { readSnapshotNodesReferenceFrame } from './interaction-touch-reference-f
 import { resolveRefTargetWithRectRefresh, type ResolveRefTarget } from './interaction-targeting.ts';
 import { unsupportedMacOsDesktopSurfaceInteraction } from './interaction-touch-policy.ts';
 import type { RefSnapshotFlagGuardResponse } from './interaction-flags.ts';
+import { errorResponse } from './response.ts';
 
 export async function handleFillCommand(params: {
   req: DaemonRequest;
@@ -49,17 +50,11 @@ export async function handleFillCommand(params: {
     }
   }
   if (session && !isCommandSupportedOnDevice('fill', session.device)) {
-    return {
-      ok: false,
-      error: { code: 'UNSUPPORTED_OPERATION', message: 'fill is not supported on this device' },
-    };
+    return errorResponse('UNSUPPORTED_OPERATION', 'fill is not supported on this device');
   }
   if (req.positionals?.[0]?.startsWith('@')) {
     if (!session) {
-      return {
-        ok: false,
-        error: { code: 'SESSION_NOT_FOUND', message: 'No active session. Run open first.' },
-      };
+      return errorResponse('SESSION_NOT_FOUND', 'No active session. Run open first.');
     }
     const invalidRefFlagsResponse = refSnapshotFlagGuardResponse('fill', req.flags);
     if (invalidRefFlagsResponse) return invalidRefFlagsResponse;
@@ -70,10 +65,7 @@ export async function handleFillCommand(params: {
         ? req.positionals.slice(2).join(' ')
         : req.positionals.slice(1).join(' ');
     if (!text) {
-      return {
-        ok: false,
-        error: { code: 'INVALID_ARGS', message: 'fill requires text after ref' },
-      };
+      return errorResponse('INVALID_ARGS', 'fill requires text after ref');
     }
 
     const resolvedRefFillTarget = await resolveRefTargetWithRectRefresh({
@@ -91,7 +83,7 @@ export async function handleFillCommand(params: {
       captureSnapshotForSession,
       resolveRefTarget,
     });
-    if (!resolvedRefFillTarget.ok) return resolvedRefFillTarget.response;
+    if (!resolvedRefFillTarget.ok) return resolvedRefFillTarget;
 
     const { ref, node, snapshotNodes, point } = resolvedRefFillTarget.target;
     const nodeType = node.type ?? '';
@@ -140,28 +132,19 @@ export async function handleFillCommand(params: {
   }
 
   if (!session) {
-    return {
-      ok: false,
-      error: { code: 'SESSION_NOT_FOUND', message: 'No active session. Run open first.' },
-    };
+    return errorResponse('SESSION_NOT_FOUND', 'No active session. Run open first.');
   }
 
   const selectorArgs = splitSelectorFromArgs(req.positionals ?? [], {
     preferTrailingValue: true,
   });
   if (selectorArgs) {
     if (selectorArgs.rest.length === 0) {
-      return {
-        ok: false,
-        error: { code: 'INVALID_ARGS', message: 'fill requires text after selector' },
-      };
+      return errorResponse('INVALID_ARGS', 'fill requires text after selector');
     }
     const text = selectorArgs.rest.join(' ').trim();
     if (!text) {
-      return {
-        ok: false,
-        error: { code: 'INVALID_ARGS', message: 'fill requires text after selector' },
-      };
+      return errorResponse('INVALID_ARGS', 'fill requires text after selector');
     }
 
     const chain = parseSelectorChain(selectorArgs.selectorExpression);
@@ -184,13 +167,10 @@ export async function handleFillCommand(params: {
       { command: req.command },
     );
     if (!resolved || !resolved.node.rect) {
-      return {
-        ok: false,
-        error: {
-          code: 'COMMAND_FAILED',
-          message: formatSelectorFailure(chain, resolved?.diagnostics ?? [], { unique: true }),
-        },
-      };
+      return errorResponse(
+        'COMMAND_FAILED',
+        formatSelectorFailure(chain, resolved?.diagnostics ?? [], { unique: true }),
+      );
     }
 
     const node = resolved.node;
@@ -235,11 +215,5 @@ export async function handleFillCommand(params: {
     });
   }
 
-  return {
-    ok: false,
-    error: {
-      code: 'INVALID_ARGS',
-      message: 'fill requires x y text, @ref text, or selector text',
-    },
-  };
+  return errorResponse('INVALID_ARGS', 'fill requires x y text, @ref text, or selector text');
 }

src/daemon/handlers/interaction-flags.ts

@@ -1,5 +1,6 @@
 import type { CommandFlags } from '../../core/dispatch.ts';
 import type { DaemonResponse } from '../types.ts';
+import { errorResponse } from './response.ts';
 
 const REF_UNSUPPORTED_FLAG_MAP: ReadonlyArray<[keyof CommandFlags, string]> = [
   ['snapshotDepth', '--depth'],
@@ -13,13 +14,10 @@ export function refSnapshotFlagGuardResponse(
 ): DaemonResponse | null {
   const unsupported = unsupportedRefSnapshotFlags(flags);
   if (unsupported.length === 0) return null;
-  return {
-    ok: false,
-    error: {
-      code: 'INVALID_ARGS',
-      message: `${command} @ref does not support ${unsupported.join(', ')}.`,
-    },
-  };
+  return errorResponse(
+    'INVALID_ARGS',
+    `${command} @ref does not support ${unsupported.join(', ')}.`,
+  );
 }
 
 export type RefSnapshotFlagGuardResponse = typeof refSnapshotFlagGuardResponse;

src/daemon/handlers/interaction-get.ts

@@ -6,28 +6,18 @@ import { refSnapshotFlagGuardResponse } from './interaction-flags.ts';
 import { readTextForNode } from './interaction-read.ts';
 import { resolveRefTarget } from './interaction-targeting.ts';
 import { resolveSelectorTarget } from './interaction-selector.ts';
+import { errorResponse } from './response.ts';
 
 export async function handleGetCommand(params: InteractionHandlerParams): Promise<DaemonResponse> {
   const { req, sessionName, sessionStore, contextFromFlags } = params;
   const sub = req.positionals?.[0];
   if (sub !== 'text' && sub !== 'attrs') {
-    return {
-      ok: false,
-      error: { code: 'INVALID_ARGS', message: 'get only supports text or attrs' },
-    };
+    return errorResponse('INVALID_ARGS', 'get only supports text or attrs');
   }
   const session = sessionStore.get(sessionName);
-  if (!session) {
-    return {
-      ok: false,
-      error: { code: 'SESSION_NOT_FOUND', message: 'No active session. Run open first.' },
-    };
-  }
+  if (!session) return errorResponse('SESSION_NOT_FOUND', 'No active session. Run open first.');
   if (!isCommandSupportedOnDevice('get', session.device)) {
-    return {
-      ok: false,
-      error: { code: 'UNSUPPORTED_OPERATION', message: 'get is not supported on this device' },
-    };
+    return errorResponse('UNSUPPORTED_OPERATION', 'get is not supported on this device');
   }
   const refInput = req.positionals?.[1] ?? '';
   if (refInput.startsWith('@')) {
@@ -43,7 +33,7 @@ export async function handleGetCommand(params: InteractionHandlerParams): Promis
       invalidRefMessage: 'get text requires a ref like @e2',
       notFoundMessage: `Ref ${refInput} not found`,
     });
-    if (!resolvedRefTarget.ok) return resolvedRefTarget.response;
+    if (!resolvedRefTarget.ok) return resolvedRefTarget;
     const { ref, node } = resolvedRefTarget.target;
     const selectorChain = buildSelectorChainForNode(node, session.device.platform, {
       action: 'get',
@@ -77,10 +67,7 @@ export async function handleGetCommand(params: InteractionHandlerParams): Promis
 
   const selectorExpression = req.positionals.slice(1).join(' ').trim();
   if (!selectorExpression) {
-    return {
-      ok: false,
-      error: { code: 'INVALID_ARGS', message: 'get requires @ref or selector expression' },
-    };
+    return errorResponse('INVALID_ARGS', 'get requires @ref or selector expression');
   }
   const resolvedSelectorTarget = await resolveSelectorTarget({
     command: req.command,
@@ -94,7 +81,7 @@ export async function handleGetCommand(params: InteractionHandlerParams): Promis
     requireUnique: true,
     disambiguateAmbiguous: sub === 'text',
   });
-  if (!resolvedSelectorTarget.ok) return resolvedSelectorTarget.response;
+  if (!resolvedSelectorTarget.ok) return resolvedSelectorTarget;
   const { resolved } = resolvedSelectorTarget;
   const node = resolved.node;
   const selectorChain = buildSelectorChainForNode(node, session.device.platform, {