fix: propagate MCP config and prompt settings to delegate subagents

[buger]

Summary

Fixes three issues where the delegate tool created subagents that were missing critical parent configuration:

• MCP tools not propagated: enableMcp, mcpConfig, mcpConfigPath were never added to configOptions in ProbeAgent.initializeTools(), so the delegateTool closure always captured defaults (false/null). Subagents never loaded MCP tools like workable-api.
• Wrong prompt type: delegate() defaulted to promptType: 'code-researcher', but that prompt type never existed in prompts.js. It fell back to code-explorer which is explicitly READ-ONLY ("You must NEVER create, modify, delete, or write files"), causing delegates to refuse action tools.
• Custom prompts lost: customPrompt and completionPrompt were never passed to delegates, so user-configured system prompts were lost in subagents.

All three issues were present from inception — not regressions. The MCP forwarding PR (#375) added plumbing in delegate.js and vercel.js but missed wiring configOptions in ProbeAgent.js.

Changes

• npm/src/agent/ProbeAgent.js: Added enableMcp, mcpConfig, mcpConfigPath, promptType, customPrompt, completionPrompt to configOptions in initializeTools()
• npm/src/tools/vercel.js: Destructure promptType, customPrompt, completionPrompt from options and forward to delegate() call
• npm/src/delegate.js: Accept customPrompt, completionPrompt params; changed promptType default from 'code-researcher' to undefined (inherits parent's default); pass all three to ProbeAgent constructor
• Tests updated: New tests for MCP config propagation and prompt type inheritance; existing tests updated for new parameter shape

Testing

• 112 test suites, 2852 tests passing
• New tests in probe-agent-delegate.test.js: MCP config propagation (4 tests), prompt type propagation (5 tests)
• Updated delegate-config.test.js, delegate-integration.test.js, delegate-limits.test.js for new parameters

cd npm && node --experimental-vm-modules node_modules/.bin/jest --no-coverage --testPathIgnorePatterns="integration"
# Test Suites: 112 passed, Tests: 2852 passed

🤖 Generated with Claude Code

[probelabs]

PR Overview: Fix MCP Config and Prompt Settings Propagation to Delegate Subagents

Summary

This PR fixes three critical bugs where the delegate tool created subagents that were missing important parent configuration:

1. MCP tools not propagated: enableMcp, mcpConfig, and mcpConfigPath were never added to configOptions in ProbeAgent.initializeTools(), causing subagents to never load MCP tools like workable-api.

2. Wrong prompt type: delegate() defaulted to promptType: 'code-researcher', which doesn't exist in prompts.js. This caused fallback to code-explorer—a READ-ONLY prompt that refuses file modifications.

3. Custom prompts lost: customPrompt and completionPrompt were never passed to delegates, so user-configured system prompts were lost in subagents.

All three issues were present from inception—not regressions. The MCP forwarding PR (#375) added plumbing in delegate.js and vercel.js but missed wiring configOptions in ProbeAgent.js.

Files Changed

Core Implementation

• npm/src/agent/ProbeAgent.js (+12 lines)

  • Added enableMcp, mcpConfig, mcpConfigPath, promptType, customPrompt, completionPrompt to configOptions in initializeTools()
  • These values are captured in the closure used by delegateTool so subagents can inherit parent configuration

• npm/src/delegate.js (+6 lines, -2 lines)

  • Changed promptType default from 'code-researcher' to undefined (inherits parent's default)
  • Added customPrompt and completionPrompt parameters
  • Passes all three prompt settings to ProbeAgent constructor when creating subagents

• npm/src/tools/vercel.js (+4 lines, -1 line)

  • Destructures promptType, customPrompt, completionPrompt from options
  • Forwards all three to the delegate() call

Test Updates

• npm/tests/unit/probe-agent-delegate.test.js (+108 lines)

  • New test suite: "Delegate MCP config propagation" (4 tests)
  • New test suite: "Delegate prompt type propagation" (5 tests)
  • Verifies MCP config is stored before tools are initialized
  • Documents that code-researcher doesn't exist and falls back to read-only code-explorer
  • Verifies code-explorer prompt contains READ-ONLY restrictions

• npm/tests/unit/delegate-limits.test.js (+16 lines, -3 lines)

  • Updated test to expect promptType: undefined instead of 'code-researcher'
  • Added test for explicit promptType parameter passing

• npm/tests/delegate-config.test.js (+2 lines, -2 lines)

  • Updated assertion to use expect.objectContaining() for flexibility

• npm/tests/delegate-integration.test.js (+2 lines, -2 lines)

  • Updated assertion to use expect.objectContaining() for flexibility

Architecture & Impact Assessment

What This PR Accomplishes

1. MCP Tool Propagation: Subagents now properly inherit MCP configuration from parent agents, enabling them to create their own MCPXmlBridge instances and access MCP tools.

2. Prompt Type Inheritance: Subagents now inherit the parent's prompt type (or use the parent's default), fixing the bug where all delegates were forced into read-only mode.

3. Custom Prompt Preservation: User-configured system prompts (customPrompt, completionPrompt) are now properly propagated to subagents.

Key Technical Changes

Before:

ProbeAgent.initializeTools()
  └─ configOptions = { ... }  // Missing MCP and prompt settings
      └─ delegateTool(configOptions)
          └─ closure captures defaults (enableMcp: false, promptType: 'code-researcher')
              └─ delegate() creates subagent with wrong config

After:

ProbeAgent.initializeTools()
  └─ configOptions = {
       enableMcp: this.enableMcp,
       mcpConfig: this.mcpConfig,
       mcpConfigPath: this.mcpConfigPath,
       promptType: this.promptType,
       customPrompt: this.customPrompt,
       completionPrompt: this.completionPrompt,
       ...
     }
      └─ delegateTool(configOptions)
          └─ closure captures actual parent values
              └─ delegate() creates subagent with correct config

Affected System Components

1. Delegation System: Core delegation flow in delegate.js and vercel.js
2. MCP Integration: MCP tool loading in subagents via MCPXmlBridge
3. Prompt System: Prompt type selection and custom prompt handling
4. Tool Initialization: ProbeAgent.initializeTools() configOptions construction

Component Relationships

graph TD
    A[ProbeAgent Parent] -->|initializeTools| B[configOptions]
    B -->|includes MCP & prompt settings| C[delegateTool]
    C -->|closure captures config| D[delegate function]
    D -->|creates| E[ProbeAgent Subagent]
    E -->|uses MCP config| F[MCPXmlBridge]
    E -->|uses prompt settings| G[System Prompt]
    
    style B fill:#90EE90
    style E fill:#FFB6C1

Loading

Scope Discovery & Context Expansion

Direct Impact

• Delegation: All delegate tool invocations now properly inherit MCP and prompt configuration
• MCP Tools: Subagents can now access MCP servers configured in parent agents
• Prompt Behavior: Subagents no longer forced into read-only mode when parent has write capabilities

Indirect Impact

• Multi-Agent Workflows: Agents using delegation for task breakdown now maintain consistent tool access
• Custom Prompts: Enterprise deployments with custom system prompts now work correctly with delegation
• MCP Server Access: Tools like workable-api now available in delegated subagents

Related Files (Not Changed)

• npm/src/agent/mcp/xmlBridge.js - MCP bridge implementation (unchanged, now properly receives config)
• npm/src/agent/shared/prompts.js - Prompt definitions (unchanged, bug was using non-existent type)
• npm/src/agent/tools.js - Tool creation factory (unchanged, receives updated configOptions)

Testing Coverage

• 112 test suites, 2852 tests passing
• New tests verify MCP config propagation through the delegation chain
• New tests document the code-researcher → code-explorer fallback bug
• Tests verify prompt type inheritance and custom prompt preservation

Root Cause Analysis

The bugs originated from incomplete implementation in PR #375:

1. MCP forwarding was added to delegate.js (lines 497-500) and vercel.js (lines 1259-1262)
2. But configOptions in ProbeAgent.js was never updated to include MCP settings
3. The delegateTool closure captured undefined values, defaulting to enableMcp: false
4. Prompt type bug was older: delegate.js hardcoded 'code-researcher' which never existed in prompts.js

References

• npm/src/agent/ProbeAgent.js:882-899 - MCP and prompt settings added to configOptions
• npm/src/delegate.js:387-390 - Prompt type default changed, custom prompts added
• npm/src/tools/vercel.js:1135-1260 - Prompt settings forwarded to delegate()
• npm/src/agent/shared/prompts.js - Predefined prompts (no code-researcher exists)
• npm/tests/unit/probe-agent-delegate.test.js:661-769 - New MCP and prompt propagation tests

Metadata

• Review Effort: 2 / 5
• Primary Label: bug

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Last updated: 2026-03-20T18:05:48.962Z | Triggered by: pr_opened | Commit: ce8b9a0

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[probelabs]

✅ Security Check Passed

No security issues found – changes LGTM.

✅ Security Check Passed

No security issues found – changes LGTM.

\n\n

Architecture Issues (3)

Severity	Location	Issue
🟡 Warning	npm/src/tools/vercel.js:1135	The delegateTool function destructures 20+ parameters from options, creating a complex function signature. This parameter explosion suggests the need for a configuration object pattern to improve maintainability and reduce coupling. 💡 Suggestion Consider grouping related parameters (e.g., mcpSettings, promptSettings, timeoutSettings, securitySettings) into configuration objects to reduce the parameter count and improve readability.
🟡 Warning	npm/src/delegate.js:387	The promptType default changed from 'code-researcher' to undefined. While this fixes the bug (non-existent prompt type), it creates an implicit dependency on ProbeAgent's default behavior. The inheritance pattern is not explicitly documented in the function signature or JSDoc. 💡 Suggestion Add explicit JSDoc documentation explaining that undefined promptType means 'inherit parent's default'. Consider making this intent more explicit with a named constant or comment.
🟡 Warning	npm/src/agent/ProbeAgent.js:882	Adding 6 new fields to configOptions (enableMcp, mcpConfig, mcpConfigPath, promptType, customPrompt, completionPrompt) creates a tight coupling between ProbeAgent initialization and delegate tool creation. This pattern requires manual synchronization whenever new configuration is added. 💡 Suggestion Consider a configuration propagation pattern where ProbeAgent exposes a getDelegateConfig() method that returns all relevant configuration, eliminating the need to manually add each field to configOptions.

✅ Performance Check Passed

No performance issues found – changes LGTM.

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Last updated: 2026-03-20T18:00:55.075Z | Triggered by: pr_opened | Commit: ce8b9a0

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