Add custom tool override capability for domain-specific operations

[Copilot]

Leverages the Copilot SDK's SessionHooks API (onPreToolUse/onPostToolUse) to enforce workspace safety, reduce redundant I/O, and expose per-task tool usage stats during execution.

New: src/services/tool-overrides.ts

• ToolOverrideConfig — loaded from / saved to .planeteer/config.json; master enabled switch plus per-tool toggles
• createSessionHooks(config, onToolUse?) — builds SessionHooks with:
  • edit_file / str_replace_editor: denies writes to paths outside process.cwd()
  • read_file: serves in-memory cache on repeated reads (denies the tool call, injects cached content into the denial reason); warns agent when file exceeds configurable size limit (default 100 KB)
  • grep: injects deduplicated exclude_dirs (node_modules, .git, dist, etc.) into modified args and provides --exclude-dir hint as additional context
• ToolUsageStats (reads, edits, greps) + createEmptyStats()

src/services/copilot.ts

• Loads ToolOverrideConfig and attaches hooks on every createSession() call
• Adds onToolUse?: (toolName: string) => void to StreamCallbacks and sendPromptSync options

src/services/executor.ts

• onToolUse?: (taskId, toolName) => void added to ExecutionCallbacks, threaded through init and regular task execution

src/screens/execute.tsx

• Tracks Record<string, ToolUsageStats> per task; renders inline 📖/✏️/🔍 counters next to each task row

Configuration example (.planeteer/config.json)

{
  "enabled": true,
  "editFile": { "enabled": true },
  "readFile": { "enabled": true, "maxSizeKb": 100 },
  "grep": {
    "enabled": true,
    "excludePatterns": ["node_modules", ".git", "dist", ".planeteer"]
  }
}

Tests

14 new tests in src/services/copilot.test.ts covering path validation (allow/deny/disabled), grep deduplication, cache serving, onToolUse callback, and config loading.

Original prompt

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This section details on the original issue you should resolve

<issue_title>[enhancement] Add custom tool override capability for domain-specific operations</issue_title>
<issue_description>## Background

The Copilot SDK v0.1.30 (released March 3, 2026) adds support for overriding built-in tools like grep, edit_file, or read_file, implemented by Steve Sanderson in commit f843c80.

This feature allows applications to customize how Copilot agents interact with files and code, enabling domain-specific optimizations and constraints.

Proposal

Leverage tool overriding to implement Planeteer-specific file operation constraints and workspace scoping:

1. Override edit_file tool to:

   • Enforce that agents only edit files within the current working directory
   • Prevent accidental modification of system files or directories outside the project
   • Add pre/post-edit validation hooks (e.g., syntax checking, formatting)
   • Log all file modifications for audit trail in the Execute screen

2. Override read_file tool to:

   • Implement intelligent file size limits (warn/truncate for files >100KB)
   • Cache frequently-read files to reduce redundant operations
   • Track which files each task has accessed for dependency inference

3. Override grep tool to:

   • Scope searches to project-relevant directories (exclude node_modules, .git, etc.)
   • Add search result caching for repeated queries
   • Provide more context lines by default for better agent understanding

4. Configuration in Settings - Add .planeteer/config.json to allow users to enable/disable overrides or customize behavior

Benefit

• Safety: Prevent agents from accidentally modifying files outside the project workspace
• Performance: Caching and scoping reduce redundant operations and improve execution speed
• Observability: Better logging and tracking of tool usage during execution
• Customization: Users can tailor tool behavior to their project requirements

Acceptance Criteria

• src/services/copilot.ts registers custom tool overrides with overridesBuiltInTool: true flag
• edit_file override validates paths are within process.cwd() before executing
• read_file override implements size limits and caching logic
• grep override excludes common ignore patterns (node_modules, .git, etc.)
• Settings file .planeteer/config.json allows enabling/disabling overrides
• Execute screen displays tool usage statistics (reads, edits, greps per task)
• Tests in src/services/copilot.test.ts verify override behavior
• Documentation in README explains tool overrides and configuration options

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Comments on the Issue (you are @copilot in this section)

• Fixes [enhancement] Add custom tool override capability for domain-specific operations #30

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