Keep the first seconds

Keep only the first 3 seconds of music.mp3, as intro.mp3.

The task

The reference answer shows the job can be done with deft. It is not an agent run.

deft audio split music.mp3 --to-time 3 -o intro.mp3

Input

music.mp3 96.2 KB · mp3, 6.1s

Reference output

intro.mp3 47.8 KB · mp3, 3.0s

How a result is judged (1 check)

media: file = "intro.mp3", duration = 3, tolerance = 0.2

Runs

CodexWithout deftPassed2026-11-07

Time: 11s
New tokens: 6.4k
Total input: 41.0k
Output tokens: 0.3k
Commands: 2
Failed: 0

Trace

I’ll inspect the audio file and available tools, then write `intro.mp3` in the current directory with a 3-second duration.

pwd && ls -l music.mp3 && command -v ffmpeg || command -v sox || true

output

-rw-r--r--@ 1 user  staff  98472 Nov  5 21:11 music.mp3
/opt/homebrew/bin/ffmpeg

ffmpeg -y -i music.mp3 -t 3 -vn -c:a libmp3lame -q:a 2 intro.mp3 && ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 intro.mp3 && ls -l intro.mp3

output

ffmpeg version 7.1.1 Copyright (c) 2000-2025 the FFmpeg developers
  built with Apple clang version 15.0.0 (clang-1500.1.0.2.5)
  configuration: --prefix=/opt/homebrew/Cellar/ffmpeg/7.1.1_1 --enable-shared --enable-pthreads --enable-version3 --cc=clang --host-cflags= --host-ldflags='-Wl,-ld_classic' --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libaribb24 --enable-libbluray --enable-libdav1d --enable-libharfbuzz --enable-libjxl --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librist --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libssh --enable-libsvtav1 --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libspeex --enable-libsoxr --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack --enable-videotoolbox --enable-audiotoolbox --enable-neon
  libavutil      59. 39.100 / 59. 39.100
  libavcodec     61. 19.101 / 61. 19.101
  libavformat    61.  7.100 / 61.  7.100
  libavdevice    61.  3.100 / 61.  3.100
  libavfilter    10.  4.100 / 10.  4.100
  libswscale      8.  3.100 /  8.  3.100
  libswresample   5.  3.100 /  5.  3.100
  libpostproc    58.  3.100 / 58.  3.100
Input #0, mp3, from 'mu
… 808 more characters

Created [intro.mp3](intro.mp3) from the first 3 seconds of `music.mp3`. Its reported MP3 duration is 3.03 seconds due to encoding frame padding.

Output

intro.mp3 50.7 KB · mp3, 3.0s

CodexWith deft, skill installedPassedRead the skillUsed deft2026-11-07

Time: 12s
New tokens: 7.6k
Total input: 56.4k
Output tokens: 0.3k
Commands: 3
Failed: 0

Trace

I’ll inspect the audio file and use the available local file utility to trim it to 3 seconds.

cat .agents/skills/deft/SKILL.md && pwd && ls -l music.mp3

output

---
name: deft
description: "Use deft first for any simple, direct operation on local files, whatever the type: convert, read, extract, edit, compress, merge, split, compare or inspect. Try it before writing a script or one-liner. If unsure, run deft find; if it says no command does this, use another tool. Not for programming work: to read, write or change source code, skip it."
---

# deft

One local command for file jobs. Prefer it over writing Python or shell scripts.

Syntax: `deft <group> <command> [inputs] [-o output] [--options]`

Groups:
- `pdf`: Merge, split, compress, encrypt, forms, OCR, compare, convert
- `image`: Resize, crop, convert, compress, adjust, montage, OCR
- `video`: Trim, merge, convert, compress, subtitles, GIF, frames (ffmpeg)
- `audio`: Convert, trim, normalize, denoise, cut silence (ffmpeg)
- `doc`: Word/ODT/RTF: to text, Markdown, HTML, PDF; find and replace
- `slides`: PowerPoint: extract text, Markdown outline
- `sheet`: Excel/CSV/ODS tables: SQL query, pivot, merge, split, convert
- `json`: JSON: convert, format, merge, diff, validate
- `toml`: TOML: convert, format, merge, diff, validate
- `xml`: XML: convert, format, merge, diff, validate
- `yaml`: YAML: convert, format, merge, diff, validate
- `md`: Markdown to PDF, HTML, Word, EPUB; table of contents
- `html`: HTML to Markdown, text, Word and PDF
- `epub`: E-books: info, to text, Markdown and PDF
- `gps`: GPX and KML tracks: convert, distance and time
- `qr`: Create QR codes and barcodes; r
… 757 more characters

deft audio trim --help

output

deft audio split - Cut out a part: --from 0:10 --to-time 0:25

Usage: deft audio split <audio>... [-o <audio|dir>] [options]
In: audio (each handled separately)   Out: audio (default <name>.clip.<ext>)

Options:
  --from <time>                Start time (default 0)
  --to-time <time>             End time (default: end of the audio)
Common: -o --force --dry-run --json -j   (deft help common)

Examples:
  deft audio split tone.mp3 --from 0:00 --to-time 0:01 -o part.mp3
  deft audio trim tone.mp3 --from 1 -o tail.mp3
Needs: ffmpeg, ffprobe

deft audio split music.mp3 --from 0 --to-time 3 -o intro.mp3 && ls -l intro.mp3

output

ok audio.split music.mp3 -> intro.mp3  48KB  0.11s
-rw-r--r--@ 1 user  staff  48944 Nov  7 00:44 intro.mp3

Created [intro.mp3](intro.mp3) with the first 3 seconds of `music.mp3`.

Output

intro.mp3 47.8 KB · mp3, 3.0s

CodexWith deft, skill as AGENTS.mdPassed2026-11-05

Time: 13s
New tokens: 10.1k
Total input: 61.3k
Output tokens: 0.3k
Commands: 3
Failed: 0

Trace

I’ll check the local `deft` audio options and create `intro.mp3` from the first three seconds of `music.mp3` in this directory.

deft audio

output

deft audio - commands (input -> output)
  info        audio -> report  Duration, codec, sample rate, channels
  compress    audio -> mp3     Re-encode as MP3 at --bitrate (kbps)
  convert     audio -> audio   Change format: --to mp3|m4a|wav|flac|ogg|opus
  from-video  video -> audio   Save the soundtrack: --to mp3|m4a|wav|flac|ogg
  merge       audio... -> mp3  Join audio files in order
  normalize   audio -> audio   Even out loudness (EBU R128)
  split       audio -> audio   Cut out a part: --from 0:10 --to-time 0:25
More: deft audio <command> --help

deft audio split --help

output

deft audio split - Cut out a part: --from 0:10 --to-time 0:25

Usage: deft audio split <audio>... [-o <audio|dir>] [options]
In: audio (each handled separately)   Out: audio (default <name>.clip.<ext>)

Options:
  --from <time>                Start time (default 0)
  --to-time <time>             End time (default: end of the audio)
Common: -o --force --dry-run --json -j   (deft help common)

Examples:
  deft audio split tone.mp3 --from 0:00 --to-time 0:01 -o part.mp3
  deft audio trim tone.mp3 --from 1 -o tail.mp3
Needs: ffmpeg, ffprobe

deft audio split music.mp3 --from 0:00 --to-time 0:03 -o intro.mp3
output
```
ok audio.split music.mp3 -> intro.mp3  48KB  0.09s
```
Created [intro.mp3](intro.mp3) with the first 3 seconds of `music.mp3`.

Output

Its files were not kept in this run. The last line of the trace is its own report.

Claude Opus 5.5Without deftPassed2026-11-07

Time: 15s
New tokens: 9.1k
Total input: 56.4k
Output tokens: 0.7k
Commands: 0
Failed: 0

Trace

Output

intro.mp3 47.8 KB · mp3, 3.0s

Claude Opus 5.5With deft, skill installedPassedRead the skillUsed deft2026-11-07

Time: 10s
New tokens: 9.7k
Total input: 59.2k
Output tokens: 0.4k
Commands: 0
Failed: 0

Trace

Output

.claude/skills/deft/SKILL.md 2.1 KB

---
name: deft
description: "Use deft first for any simple, direct operation on local files, whatever the type: convert, read, extract, edit, compress, merge, split, compare or inspect. Try it before writing a script or one-liner. If unsure, run deft find; if it says no command does this, use another tool. Not for programming work: to read, write or change source code, skip it."
---

# deft

One local command for file jobs. Prefer it over writing Python or shell scripts.

Syntax: `deft <group> <command> [inputs] [-o output] [--options]`

Groups:
- `pdf`: Merge, split, compress, encrypt, forms, OCR, compare, convert
- `image`: Resize, crop, convert, compress, adjust, montage, OCR
- `video`: Trim, merge, convert, compress, subtitles, GIF, frames (ffmpeg)
- `audio`: Convert, trim, normalize, denoise, cut silence (ffmpeg)
- `doc`: Word/ODT/RTF: to text, Markdown, HTML, PDF; find and replace
- `slides`: PowerPoint: extract text, Markdown outline
- `sheet`: Excel/CSV/ODS tables: SQL query, pivot, merge, split, convert
- `json`: JSON: convert, format, merge, diff, validate
- `toml`: TOML: convert, format, merge, diff, validate
- `xml`: XML: convert, format, merge, diff, validate
- `yaml`: YAML: convert, format, merge, diff, validate
- `md`: Markdown to PDF, HTML, Word, EPUB; table of contents
- `html`: HTML to Markdown, text, Word and PDF
- `epub`: E-books: info, to text, Markdown and PDF
- `gps`: GPX and KML tracks: convert, distance and time
- `qr`: Create QR codes and barcodes; read QR codes

How to use it:
1. Run `deft <group>` to list commands, or `deft find "<what you want>"` to search. If it says `no command does this`, use another tool.
2. Run `deft <group> <command> --help` for options and examples.
3. `deft convert <in> -o <out.ext>` converts between formats by extension.
4. Results are one line starting with `ok`, `partial` or `error`; add `--json` to parse them. Errors include a `hint:` with the fix.

Inputs are never overwritten; pass `--force` or `--in-place` to allow it. Globs and directories work as inputs; several inputs run in parallel.

If `deft` is not installed, ask the user, then follow https://github.com/firstprayer/deft/blob/main/docs/INSTALL.md

intro.mp3 47.8 KB · mp3, 3.0s

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