Research Date: 2025-10-13 Purpose: Understand session management architecture and patterns to inform test_sim tool integration

Lines 1-48: Singleton in-memory store for session defaults

Key Features:

• Type Definition (lines 3-13): SessionDefaults includes:

  • projectPath, workspacePath (mutually exclusive project identifiers)
  • scheme, configuration (build settings)
  • simulatorName, simulatorId (mutually exclusive simulator identifiers)
  • deviceId (device identifier)
  • useLatestOS (simulator OS selection)
  • arch (architecture: 'arm64' | 'x86_64')

• Storage Pattern (lines 15-45):

  • setDefaults(partial): Merges new defaults into existing ones (line 18-21)
  • clear(keys?): Clears all or specific keys (lines 23-36)
  • get<K>(key): Retrieves single default value (lines 38-40)
  • getAll(): Returns copy of all defaults (lines 42-44)

Critical Detail: Line 47 exports singleton instance sessionStore

Lines 63-174: createSessionAwareTool<TParams> function

Key Features:

1. Requirement Types (lines 63-65):

   • allOf: All specified keys must be present
   • oneOf: At least one specified key must be present
   • Optional custom error messages

2. Argument Sanitization (lines 92-96):

   • Treats null and undefined as "not provided"
   • Only includes explicitly provided values in sanitizedArgs
   • Critical: Empty object {} from client means "use all session defaults"

3. Factory-Level Mutual Exclusivity Check (lines 98-110):

   • Checks exclusivePairs BEFORE merging session defaults
   • Rejects if user provides multiple values from an exclusive pair
   • Example: { projectPath: '/a', workspacePath: '/b' } → error

4. Session Defaults Merge (line 113):

   • merged = { ...sessionStore.getAll(), ...sanitizedArgs }
   • Explicit args override session defaults

5. Exclusive Pair Pruning (lines 115-128):

   • Only when user provides a concrete value
   • Drops conflicting session defaults from the pair
   • Example: If session has simulatorName but user provides simulatorId, drop simulatorName from merged

6. Requirements Validation (lines 130-155):

   • allOf: All keys must be in merged (line 132-141)
   • oneOf: At least one key must be in merged (line 142-154)
   • Returns friendly error messages with session-set-defaults hints

7. Schema Validation (line 157):

   • Validates merged result against internal schema
   • All XOR constraints enforced by schema's .refine() calls

8. Error Handling (lines 159-173):

   • Zod errors formatted with helpful tips
   • Suggests using session-set-defaults tool

Current State: Does NOT use session-aware factory

Schema Structure:

• Base Schema (lines 19-68): All fields including session-manageable ones
• With XOR Validation (lines 74-84):
  • Line 75-76: Requires at least one of projectPath/workspacePath
  • Line 78-80: Rejects both projectPath AND workspacePath
  • Line 81-84: Platform validation (rejects macOS)

Handler Pattern (lines 135-162):

• Uses manual try-catch with inline validation
• Validates with testSimulatorSchema.parse(args)
• Formats Zod errors manually
• Calls test_simLogic(validatedParams, executor)

Key Observations:

1. No session defaults integration
2. Manual error formatting duplicates factory logic
3. XOR constraints in schema but not in factory-level checks
4. Schema expects both XOR sides to be optional but requires one

Pattern: Uses createTypedTool (NOT session-aware)

Handler (lines 324-330):

handler: createTypedTool<TestMacosParams>(
  testMacosSchema as z.ZodType<TestMacosParams>,
  (params: TestMacosParams) => {
    return testMacosLogic(params, getDefaultCommandExecutor(), getDefaultFileSystemExecutor());
  },
  getDefaultCommandExecutor,
)

Key Observations:

1. Uses standard typed tool factory
2. No session defaults support
3. XOR validation only in schema (lines 52-58)

Pattern: Uses createTypedTool (NOT session-aware)

Handler (lines 281-294):

• Similar to test_macos
• No session defaults integration
• XOR validation in schema only (lines 51-57)

Lines 168-186: Complete session-aware implementation

Key Pattern Elements:

1. Dual Schema Structure:

   • Internal Schema (lines 56-82): Full validation with XOR constraints
   • Public Schema (lines 157-166): Omits session-managed fields

2. Public Schema Creation (lines 157-166):

const publicSchemaObject = baseSchemaObject.omit({
  projectPath: true,
  workspacePath: true,
  scheme: true,
  configuration: true,
  simulatorId: true,
  simulatorName: true,
  useLatestOS: true,
  // platform is NOT omitted - it's available for clients to specify
} as const);

3. Handler Configuration (lines 172-185):

handler: createSessionAwareTool<BuildSimulatorParams>({
  internalSchema: buildSimulatorSchema as unknown as z.ZodType<BuildSimulatorParams>,
  logicFunction: build_simLogic,
  getExecutor: getDefaultCommandExecutor,
  requirements: [
    { allOf: ['scheme'], message: 'scheme is required' },
    { oneOf: ['projectPath', 'workspacePath'], message: 'Provide a project or workspace' },
    { oneOf: ['simulatorId', 'simulatorName'], message: 'Provide simulatorId or simulatorName' },
  ],
  exclusivePairs: [
    ['projectPath', 'workspacePath'],
    ['simulatorId', 'simulatorName'],
  ],
})

Key Observations:

1. Internal schema has XOR constraints via .refine()
2. Factory requirements declare what's needed (allOf/oneOf)
3. Factory exclusivePairs enable session pruning
4. Public schema exposes only non-session fields
5. Logic function unchanged - receives fully validated params

Lines 522-540: Identical pattern to build_sim

Observations:

• Same dual schema approach
• Same requirements and exclusivePairs
• Demonstrates consistent pattern across tools

Step 1: Base Schema Object

const baseSchemaObject = z.object({
  projectPath: z.string().optional().describe('...'),
  workspacePath: z.string().optional().describe('...'),
  // ... other fields
});

Step 2: Preprocessor Application

const baseSchema = z.preprocess(nullifyEmptyStrings, baseSchemaObject);

Purpose: Converts empty strings to undefined for cleaner optional field handling

Step 3: XOR Constraint Addition

const toolSchema = baseSchema
  .refine((val) => val.projectPath !== undefined || val.workspacePath !== undefined, {
    message: 'Either projectPath or workspacePath is required.',
  })
  .refine((val) => !(val.projectPath !== undefined && val.workspacePath !== undefined), {
    message: 'projectPath and workspacePath are mutually exclusive. Provide only one.',
  });

Step 4: Type Inference

export type ToolParams = z.infer<typeof toolSchema>;

Step 5: Public Schema (Session-Aware Only)

const publicSchemaObject = baseSchemaObject.omit({
  projectPath: true,
  workspacePath: true,
  // ... session-managed fields
} as const);

Two-Step Validation:

1. At least one required: val.projectPath !== undefined || val.workspacePath !== undefined
2. Not both: !(val.projectPath !== undefined && val.workspacePath !== undefined)

Why Two Refines?:

• First ensures at least one is provided
• Second ensures they're mutually exclusive
• Together create true XOR behavior

Purpose: Enable session defaults and provide friendly errors

Factory Checks (createSessionAwareTool):

1. Sanitization: Null/undefined treated as "not provided"
2. Factory-Level XOR Check: Rejects multiple explicit values from exclusivePairs
3. Session Merge: Combines session + explicit args (explicit wins)
4. Session Pruning: Removes conflicting session defaults per exclusivePairs
5. Requirements Check: Validates allOf/oneOf on merged data
6. Then passes to schema validation

Purpose: Enforce type safety and business rules

Schema Validation:

1. Validates merged data against internal schema
2. Enforces XOR via .refine() calls
3. Ensures all type constraints
4. Final safety net

Factory Level:

• User-Friendly: "Missing required session defaults" vs raw Zod error
• Session Logic: Handles merge, pruning, precedence
• XOR Enforcement: Prevents explicit conflicts BEFORE merge

Schema Level:

• Type Safety: Ensures final data structure correctness
• Business Rules: All domain constraints enforced
• Safety Net: Catches any factory logic bugs

Input: { simulatorId: 'ABC' } Session Defaults: { scheme: 'App', projectPath: '/x', simulatorName: 'iPhone 16' }

Factory Processing:

1. Sanitize: simulatorId is concrete
2. Factory XOR: Only one value from [simulatorId, simulatorName] → OK
3. Merge: { scheme: 'App', projectPath: '/x', simulatorId: 'ABC', simulatorName: 'iPhone 16' }
4. Prune: User provided simulatorId, so drop simulatorName → { scheme: 'App', projectPath: '/x', simulatorId: 'ABC' }
5. Requirements: Check allOf/oneOf → OK
6. Pass to schema

Schema Validation:

1. XOR refinement: Only one of simulatorId/simulatorName → OK
2. Type checks: All fields valid → OK
3. Return validated params to logic

Result: Logic receives { scheme: 'App', projectPath: '/x', simulatorId: 'ABC' }

Lines 46-56: Basic merge behavior

• Sets session defaults
• Calls handler with empty object
• Verifies logic receives merged params

Lines 58-85: Explicit args override session

• Session has one value
• Args provide different value
• Verifies arg wins

Lines 87-92: allOf requirement validation

• Missing required field
• Returns friendly error message

Lines 94-99: oneOf requirement validation

• None of the options provided
• Returns friendly error with session-set-defaults hint

Lines 101-111: Zod error formatting

• Invalid type provided
• Formats error with "Tip: set session defaults"

Lines 113-134: Session pruning with null

• User provides null for conflicting field
• Session default NOT pruned (null = not provided)

Lines 136-157: Session pruning with undefined

• User provides undefined for conflicting field
• Session default NOT pruned (undefined = not provided)

Lines 159-189: Factory-level XOR check

• User provides both sides of exclusive pair
• Factory rejects BEFORE schema validation
• Error: "Mutually exclusive parameters provided"

1. Sanitization Works: null and undefined don't trigger pruning
2. Factory XOR Enforced: Multiple explicit values rejected early
3. Session Pruning Logic: Only concrete user values trigger pruning
4. Friendly Errors: All error paths provide helpful messages
5. Schema Still Validates: Factory doesn't bypass schema checks

Current test_sim (src/mcp/tools/simulator/test_sim.ts):

• Schema (lines 74-84): XOR constraints via .refine()
• Handler (lines 135-162): Manual validation, no session support
• Public Schema (line 134): baseSchemaObject.shape - exposes ALL fields

To match build_sim pattern:

1. Keep Internal Schema (lines 74-84):

   • XOR constraints stay
   • Used for final validation
   • No changes needed

2. Add Public Schema:

   • Omit session-managed fields
   • Expose only per-call configuration

3. Replace Handler (lines 135-162):

   • Use createSessionAwareTool
   • Define requirements (allOf/oneOf)
   • Define exclusivePairs

4. Result:

   • Factory handles session merge + pruning + requirements
   • Schema validates final merged data
   • Logic function unchanged

Factory exclusivePairs:

• Prevent user from providing both explicit values
• Enable session default pruning

Schema refines:

• Validate final merged data structure
• Ensure business rules after merge
• Safety net for factory bugs

Both Are Needed:

• Factory: User-facing validation + session logic
• Schema: Type safety + final correctness

From Grep Results (src/mcp/tools/):

• simulator/build_sim.ts (lines 168-186)
• simulator/build_run_sim.ts (lines 522-540)

Based on schema-helpers usage, these tools likely follow similar patterns:

• simulator/stop_app_sim.ts
• simulator/launch_app_sim.ts
• simulator/get_sim_app_path.ts
• macos/build_macos.ts
• macos/build_run_macos.ts
• macos/get_mac_app_path.ts
• device/build_device.ts
• device/get_device_app_path.ts

• project-discovery/show_build_settings.ts
• project-discovery/list_schemes.ts

• utilities/clean.ts

All session-aware tools follow the same pattern:

1. Internal schema with XOR constraints
2. Public schema omitting session fields
3. Handler using createSessionAwareTool
4. Requirements and exclusivePairs defined
5. Logic function unchanged

1. Tool Test (src/mcp/tools/simulator/__tests__/test_sim.test.ts):

   • Add session defaults test cases
   • Test requirement validation errors
   • Test exclusivePairs behavior
   • Ensure logic tests unchanged (using direct logic function calls)

2. Integration Pattern:

   • Follow test patterns from build_sim.__tests__/build_sim.test.ts
   • Test session merge behavior
   • Test public schema (omitted fields not visible)

Critical: NO Vitest mocking allowed

Pattern:

import { test_simLogic } from '../test_sim.ts';
import { createMockExecutor } from '../../../test-utils/mock-executors.ts';

it('should use session defaults', async () => {
  sessionStore.setDefaults({
    scheme: 'Test',
    projectPath: '/path/proj.xcodeproj',
    simulatorId: 'SIM-123'
  });

  const mockExecutor = createMockExecutor({
    success: true,
    output: 'TEST SUCCEEDED'
  });

  // Test handler (includes session merge)
  const result = await toolHandler({});

  // Or test logic directly (bypass session, test pure logic)
  const params = { scheme: 'Test', projectPath: '/x', simulatorId: 'S' };
  const logicResult = await test_simLogic(params, mockExecutor);
});

File: src/mcp/tools/simulator/test_sim.ts

Changes:

1. After line 87 (type definition), add public schema:

// Public schema = internal minus session-managed fields
const publicSchemaObject = baseSchemaObject.omit({
  projectPath: true,
  workspacePath: true,
  scheme: true,
  configuration: true,
  simulatorId: true,
  simulatorName: true,
  useLatestOS: true,
  // platform is NOT omitted - it's available for clients to specify
  // testRunnerEnv is NOT omitted - per-test configuration
} as const);

2. Replace handler (lines 135-162) with:

export default {
  name: 'test_sim',
  description: 'Runs tests on a simulator.',
  schema: publicSchemaObject.shape, // Public schema for MCP clients
  handler: createSessionAwareTool<TestSimulatorParams>({
    internalSchema: testSimulatorSchema as unknown as z.ZodType<TestSimulatorParams>,
    logicFunction: test_simLogic,
    getExecutor: getDefaultCommandExecutor,
    requirements: [
      { allOf: ['scheme'], message: 'scheme is required' },
      { oneOf: ['projectPath', 'workspacePath'], message: 'Provide a project or workspace' },
      { oneOf: ['simulatorId', 'simulatorName'], message: 'Provide simulatorId or simulatorName' },
    ],
    exclusivePairs: [
      ['projectPath', 'workspacePath'],
      ['simulatorId', 'simulatorName'],
    ],
  }),
};

3. Add import:

import { createSessionAwareTool } from '../../../utils/typed-tool-factory.ts';

File: src/mcp/tools/simulator/__tests__/test_sim.test.ts

Add Test Cases:

1. Session defaults merge test
2. Explicit args override session test
3. Requirements validation tests
4. ExclusivePairs behavior tests
5. Public schema validation (omitted fields)

Pattern: Follow build_sim.__tests__/build_sim.test.ts structure

Checklist:

• npm run typecheck passes
• npm run lint passes
• npm run test passes
• Manual test with mcpli/reloaderoo
• Description follows Tool Description Policy (concise)

1. Separation of Concerns:

   • Factory: Session management, user-friendly errors
   • Schema: Type safety, business rules
   • Logic: Pure business logic, unchanged

2. Progressive Enhancement:

   • Tools work without session defaults (explicit args)
   • Session defaults reduce repetition
   • Both modes supported seamlessly

3. Type Safety Maintained:

   • Factory validates requirements before schema
   • Schema validates final merged data
   • Logic receives guaranteed-valid params

4. Testing Strategy:

   • Test logic functions directly with mock executors
   • Test factory behavior with integration tests
   • No Vitest mocking - dependency injection only

1. Don't Remove Schema XOR Constraints:

   • Factory exclusivePairs ≠ schema refinements
   • Both serve different purposes
   • Both are required

2. Don't Change Logic Signatures:

   • Logic functions stay unchanged
   • Only handlers change to session-aware
   • Tests of logic remain valid

3. Don't Omit All Optional Fields from Public Schema:

   • Only session-managed fields omitted
   • Per-call configuration (like platform) stays public
   • Test-specific fields (like testRunnerEnv) stay public

4. Don't Forget Preprocessing:

   • z.preprocess(nullifyEmptyStrings, ...) stays
   • Handles empty string → undefined conversion
   • Critical for optional field behavior

• SessionStore: /src/utils/session-store.ts (lines 1-48)
• Factory: /src/utils/typed-tool-factory.ts (lines 63-174)
• Schema Helpers: /src/utils/schema-helpers.ts (lines 1-25)

• Set Defaults: /src/mcp/tools/session-management/session_set_defaults.ts
• Clear Defaults: /src/mcp/tools/session-management/session_clear_defaults.ts
• Show Defaults: /src/mcp/tools/session-management/session_show_defaults.ts

• build_sim: /src/mcp/tools/simulator/build_sim.ts (lines 168-186)
• build_run_sim: /src/mcp/tools/simulator/build_run_sim.ts (lines 522-540)

• test_sim: /src/mcp/tools/simulator/test_sim.ts (lines 1-164) - Not session-aware
• test_macos: /src/mcp/tools/macos/test_macos.ts (lines 1-332) - Not session-aware
• test_device: /src/mcp/tools/device/test_device.ts (lines 1-296) - Not session-aware

• Factory Tests: /src/utils/__tests__/session-aware-tool-factory.test.ts (lines 1-191)
• SessionStore Tests: /src/utils/__tests__/session-store.test.ts
• build_sim Tests: /src/mcp/tools/simulator/__tests__/build_sim.test.ts

• Session Plan: /docs/session_management_plan.md (lines 1-485)
• Testing Guide: /docs/TESTING.md
• Architecture: /docs/ARCHITECTURE.md

The session management system is a well-designed middleware layer that:

1. Preserves existing logic - no changes to business logic functions
2. Provides friendly UX - clear error messages with actionable hints
3. Maintains type safety - factory AND schema validation
4. Enables progressive enhancement - works with or without session defaults

The test_sim tool can be migrated by:

1. Adding a public schema that omits session fields
2. Replacing the handler with createSessionAwareTool
3. Defining requirements and exclusivePairs
4. Keeping the internal schema and logic unchanged

This pattern is proven by build_sim and build_run_sim implementations, and follows the architectural principles documented in the session management plan.