fix(hook): cursor hook fails to rewrite commands due to incorrect exit code handling

[sebastiancichos]

Summary

The Cursor agent hook (~/.cursor/hooks/rtk-rewrite.sh) fails to rewrite shell commands because it incorrectly handles the exit code from rtk rewrite. The hook treats exit code 3 (which indicates a successful rewrite) as a failure condition.

Bug Description

Current Behavior (Broken)

All shell commands pass through unchanged - RTK never rewrites them.

Expected Behavior

Shell commands like git status, ls, cat, etc. should be automatically rewritten to their RTK equivalents.

Root Cause

In hooks/cursor/rtk-rewrite.sh (line 43):

# Delegate all rewrite logic to the Rust binary.
# rtk rewrite exits 1 when there's no rewrite — hook passes through silently.
REWRITTEN=$(rtk rewrite "$CMD" 2>/dev/null) || { echo '{}'; exit 0; }

The problem: The comment says "exits 1 when there's no rewrite", but rtk rewrite actually returns exit code 3 when it successfully rewrites a command.

The || operator treats ANY non-zero exit code as failure, so:

• Exit 0 (no rewrite needed) → OK, hook continues
• Exit 3 (successfully rewritten) → TREATED AS FAILURE, hook exits with {}
• Exit 1 (actual error) → TREATED AS FAILURE, hook exits with {}

Result: Commands are never rewritten because the hook always exits early.

Evidence

Test showing rtk rewrite exit codes:

# Command that should be rewritten
$ rtk rewrite "git status"
rtk git status
$ echo $?  
3  # ← This is "success", not failure!

# Command with no rewrite needed  
$ rtk rewrite "unknown-command"
unknown-command
$ echo $?
0

Hook behavior with current code:

$ echo '{"tool_input": {"command": "git status"}}' | ~/.cursor/hooks/rtk-rewrite.sh
{}  # ← Always returns empty object, never rewrites

Fix

Replace the incorrect exit code handling:

Before:

REWRITTEN=$(rtk rewrite "$CMD" 2>/dev/null) || { echo '{}'; exit 0; }

After:

# rtk rewrite returns exit 3 on successful rewrite, 0 when no rewrite needed.
REWRITTEN=$(rtk rewrite "$CMD" 2>/dev/null)
RTK_EXIT=$?

# Exit 0 = no rewrite needed, exit 3 = successfully rewritten
# Any other exit code indicates an actual error
if [ "$RTK_EXIT" -ne 0 ] && [ "$RTK_EXIT" -ne 3 ]; then
  echo '{}'
  exit 0
fi

Testing

After applying the fix:

$ echo '{"tool_input": {"command": "git status"}}' | ~/.cursor/hooks/rtk-rewrite.sh
{
  "permission": "allow",
  "updated_input": {
    "command": "rtk git status"
  }
}

Hook now correctly rewrites commands and RTK tracking works:

$ rtk gain
RTK Token Savings (Global Scope)
════════════════════════════════════════════════════════════

Total commands:    1
Input tokens:      77
Output tokens:     76
Tokens saved:      1 (1.3%)

Impact

Without this fix:

• Cursor users get 0% token savings from the auto-rewrite feature
• Hook appears installed but does nothing
• Users must manually prefix commands with rtk

With this fix:

• 60-90% token savings on shell commands as advertised
• Transparent command rewriting works as designed
• Full RTK adoption for Cursor users

Checklist

• Fix implemented in hooks/cursor/rtk-rewrite.sh
• Tested locally with rtk rewrite commands
• Verified hook output format matches Cursor requirements

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