moesniper

Escape-proof precision file editor for LLM agents. All content is hex-encoded to guarantee zero shell corruption. Edits are applied via line-range splicing with atomic writes and automatic backups.

Install

cargo install moesniper

Usage

# Replace lines 10-12 with hex-decoded content
sniper file.rs 10 12 7573652070657473

# Delete lines 5-8
sniper file.rs 5 8 --delete

# Batch operations from a manifest file
sniper file.rs --manifest ops.json

# Undo last edit (restores backup)
sniper file.rs --undo

Flags

Heredoc Input (--stdin)

For LLM agents, --stdin with heredoc avoids hex encoding entirely:

sniper file.rs 10 15 --stdin <<'SNIPER_EOF'
fn hello() {
    println!("$world {}", x);
    let escaped = "quotes \"inside\" quotes";
}
SNIPER_EOF

Single-quoted heredoc ('SNIPER_EOF') disables ALL shell interpolation — content arrives byte-for-byte. Works with --manifest too:

sniper file.rs --manifest --stdin < ops.json

LLM Agent Workflow

# 1. Find the lines you want to edit (using ix)
ix "fn main" file.rs

# 2. Encode your replacement content
echo -n 'fn main() {}' | xxd -p | tr -d '\n'
# Output: 666e206d61696e2829207b7d

# 3. Dry-run to preview (safe - never modifies files)
sniper --json --dry-run file.rs 5 5 666e206d61696e2829207b7d

# 4. Apply the edit
sniper --json file.rs 5 5 666e206d61696e2829207b7d

# 5. Undo if something went wrong
sniper --json file.rs --undo

Hex Encoding

All replacement content must be hex-encoded. This prevents shell mangling of special characters.

# Encode your text
echo -n 'use petgraph' | xxd -p
# Output: 757365207065746772617068

# Decode a hex string
echo 757365207065746772617068 | xxd -r -p

Manifest Format

A manifest is a JSON array of operations applied bottom-up (highest line first) so line numbers in the original file stay valid:

[
  {"start": 10, "end": 12, "hex": "6e6577"},
  {"start": 5, "end": 7, "delete": true},
  {"start": 1, "hex": "6869"}
]

• start/end: 1-indexed line range (inclusive)
• hex: replacement content (hex-encoded)
• delete: set to true to delete the range (no hex needed)

Run: sniper target_file.rs --manifest ops.json

JSON Output

sniper --json file.rs 5 5 6869

{
  "status": "ok",
  "file": "file.rs",
  "lines_removed": 1,
  "lines_inserted": 1,
  "total_lines": 42,
  "backup": ".sniper/file.rs.1712345678",
  "ai_hint": "verify: read file.rs lines 5-5"
}

The ai_hint field provides contextual guidance for the next step (e.g., "verify:", "check path", "read file first"). It helps LLM agents recover from errors or verify success.

Backups

Every edit automatically creates a backup in .sniper/:

.sniper/
  file.rs.1712345678    # timestamped backup

Undo restores the most recent backup: sniper file.rs --undo

License

MIT