Skillintermediate

AI Coding Assistant Hook System Comparison

A comprehensive comparison of hook/extensibility features across Claude Code, Cursor, Gemini CLI, and Codex CLI.

Claude Code Knowledge Pack7/10/2026

Overview

A comprehensive comparison of hook/extensibility features across Claude Code, Cursor, Gemini CLI, and Codex CLI.

Last Updated: January 2026

Event Type	Claude Code	Cursor	Gemini CLI	Codex CLI
Pre-tool execution	✅ PreToolUse	✅ beforeShellExecution, beforeMCPExecution, beforeReadFile	✅ BeforeTool	❌
Post-tool execution	✅ PostToolUse	✅ afterShellExecution, afterMCPExecution, afterFileEdit	✅ AfterTool	❌
Tool failure	✅ PostToolUseFailure	❌	❌	❌
Permission request	✅ PermissionRequest	❌ (use beforeShell)	✅ Notification (ToolPermission)	❌
User prompt submit	✅ UserPromptSubmit	✅ beforeSubmitPrompt (beta)	✅ BeforeAgent	❌
Agent stop	✅ Stop	✅ stop	✅ AfterAgent	❌
Subagent start	✅ SubagentStart	❌	❌	❌
Subagent stop	✅ SubagentStop	❌	❌	❌
Session start	✅ SessionStart	❌	✅ SessionStart	❌
Session end	✅ SessionEnd	❌	✅ SessionEnd	❌
Pre-compaction	✅ PreCompact	❌	✅ PreCompress	❌
Notification	✅ Notification	❌	✅ Notification	✅ notify (limited)
Pre-model (LLM request)	❌	❌	✅ BeforeModel	❌
Post-model (LLM response)	❌	❌	✅ AfterModel	❌
Tool selection	❌	❌	✅ BeforeToolSelection	❌
Agent thought/reasoning	❌	✅ afterAgentThought	❌	❌
Tab completions	❌	✅ beforeTabFileRead, afterTabFileEdit	❌	❌

Total Events: Claude Code: 11 | Cursor: 10 | Gemini CLI: 11 | Codex CLI: 1

Capability	Claude Code	Cursor	Gemini CLI	Codex CLI
Block operations	✅ Exit 2 or JSON deny	✅ permission: deny	✅ Exit 2 or JSON deny	❌
Allow operations	✅ permissionDecision: allow	✅ permission: allow	✅ decision: allow	❌
Prompt user	✅ permissionDecision: ask	✅ permission: ask	✅ decision: ask	❌
Modify tool input	✅ updatedInput	❌	✅ (via deny + reason)	❌
Inject context to agent	✅ additionalContext (UserPromptSubmit)	✅ agent_message	✅ additionalContext	❌
Message to user only	✅ systemMessage	✅ user_message	✅ systemMessage	❌
Force agent continuation	✅ Stop hook block	✅ followup_message	✅ AfterAgent block	❌
Modify LLM request	❌	❌	✅ llm_request	❌
Modify LLM response	❌	❌	✅ llm_response	❌
Filter available tools	❌	❌	✅ toolConfig	❌

Aspect	Claude Code	Cursor	Gemini CLI	Codex CLI
Config format	JSON	JSON	JSON	TOML
User config	`~/.claude/settings.json`	`~/.cursor/hooks.json`	`~/.gemini/settings.json`	`~/.codex/config.toml`
Project config	`.claude/settings.json`	`.cursor/hooks.json`	`.gemini/settings.json`	`.codex/config.toml`
Hook type: command	✅	✅	✅	✅ (notify only)
Hook type: prompt (LLM)	✅ (Haiku)	❌	❌	❌
Tool matchers	✅ Regex (`Write\	Edit`)	❌ Global only	✅ Regex (`write_file\
Timeout config	✅ Per-hook	❌	✅ Per-hook	N/A
Hot reload	❌ Restart required	❌ Restart required	❌	N/A

Aspect	Claude Code	Cursor	Gemini CLI	Codex CLI
Input method	stdin JSON	stdin JSON	stdin JSON	stdin JSON
Output method	stdout JSON	stdout JSON	stdout JSON	N/A
Exit 0	Success, parse JSON	Success, parse JSON	Success, parse JSON	N/A
Exit 2	Block with stderr message	Not documented	Block with stderr message	N/A
Other exit	Non-blocking warning	Not documented	Non-blocking warning	N/A
Invalid JSON fallback	Treat as plain text	Treat as plain text	Treat as systemMessage	N/A

Field	Claude Code	Cursor	Gemini CLI	Codex CLI
`session_id`	✅	✅ conversation_id	✅	❌
`hook_event_name`	✅	✅	✅	❌
`cwd`	✅	✅ (may be empty)	✅	❌
`tool_name`	✅	✅ (in specific hooks)	✅	❌
`tool_input`	✅	✅	✅	❌
`tool_result`	✅ (PostToolUse)	✅ result_json	✅ tool_response	❌
`transcript_path`	✅	❌	✅	❌
`timestamp`	❌	❌	✅	❌
`user_prompt`	✅ (UserPromptSubmit)	✅ prompt	✅ prompt	❌

Field	Claude Code	Cursor	Gemini CLI	Codex CLI
Permission decision	`hookSpecificOutput.permissionDecision`	`permission`	`decision`	N/A
Reason for agent	`permissionDecisionReason`	`agent_message`	`reason`	N/A
Message for user	`systemMessage`	`user_message`	`systemMessage`	N/A
Modified input	`hookSpecificOutput.updatedInput`	❌	❌	N/A
Context injection	`hookSpecificOutput.additionalContext`	`agent_message`	`hookSpecificOutput.additionalContext`	N/A
Stop processing	`continue: false`	`continue: false`	`continue: false`	N/A
Suppress output	`suppressOutput: true`	❌	`suppressOutput: true`	N/A

Tool Type	Claude Code	Cursor	Gemini CLI	Codex CLI
Shell	`Bash`	N/A (beforeShellExecution)	`run_shell_command`	shell_tool
Read file	`Read`	N/A (beforeReadFile)	`read_file`, `read_many_files`	Built-in
Write file	`Write`	N/A (afterFileEdit)	`write_file`	Built-in
Edit file	`Edit`, `MultiEdit`	N/A (afterFileEdit)	`replace`	apply_patch
Search files	`Glob`	N/A	`glob`	Built-in
Search content	`Grep`	N/A	`search_file_content`	Built-in
Web fetch	`WebFetch`	N/A	`web_fetch`	Built-in
Web search	`WebSearch`	N/A	`google_web_search`	web_search
MCP tools	`mcp__<server>__<tool>`	`<server>__<tool>`	`mcp__<server>__<tool>`	`mcp__<server>__<tool>`

Aspect	Claude Code	Cursor	Gemini CLI	Codex CLI
Execution	Parallel (all matching)	Sequential (first only*)	Synchronous	N/A
Hook ordering	Non-deterministic	First in array	Concatenated by priority	N/A
Conflicting decisions	Last write wins (undefined)	N/A	Not documented	N/A
Default timeout	60s (command), 30s (prompt)	Not documented	60s	N/A
Max timeout	Configurable	Not documented	Configurable	N/A

*Cursor has a known bug where only the first hook in an array executes.

Platform	Claude Code	Cursor	Gemini CLI	Codex CLI
macOS	✅ Full	✅ Full	✅ Full	✅ Full
Linux	✅ Full	✅ Full	✅ Full	✅ Full
Windows	✅ Full	⚠️ Issues (Git Bash, PowerShell)	✅ Full	⚠️ Experimental

Issue Type	Claude Code	Cursor	Gemini CLI	Codex CLI
Hook not firing	Regression v2.0.27-v2.0.31	Multiple hooks bug	Issue #13155	N/A (no hooks)
Race conditions	PermissionRequest dialog	N/A	N/A	N/A
Field name changes	Legacy `decision`→`permissionDecision`	camelCase→snake_case (v2.0)	N/A	N/A
Windows issues	None major	Git Bash/PowerShell injection	None major	WSL recommended
Performance	Hooks stop after ~2.5h (log growth)	beforeTabFileRead slow on Windows	N/A	LD_LIBRARY_PATH regression (fixed)

Feature	Claude Code	Cursor	Gemini CLI	Codex CLI
LLM-evaluated hooks	✅ type: prompt	❌	❌	❌
Subagent hooks	✅ SubagentStart/Stop	❌	❌	❌
Model request hooks	❌	❌	✅ BeforeModel/AfterModel	❌
Tool selection hooks	❌