screenshot-rename/SKILL.md

---
name: screenshot-rename
description: Use when renaming a folder of screenshots, images, or short clips with AI-generated descriptive names — particularly CleanShot exports or any directory of images named only by timestamp. Triggers on requests like "rename these screenshots based on their content", "describe each of these images and rename it", or batch rename of files by visual content.
---

# Screenshot Rename

## Overview

Rename a directory of timestamp-named images (PNG / GIF / MP4 / PDF) to include AI-generated content descriptions, dispatched as parallel Haiku subagents from this Claude Code session. Each rename has the form:

```
<original prefix> - <Title Cased Description> - <original timestamp>.<ext>
```

The pipeline is **prep → batch → describe (parallel agents) → validate plan → execute renames** with hard data-loss guards at every stage.

**Core principle:** *Plan in memory, validate exhaustively, then mutate the filesystem in a single pass with `os.rename` and pre-existence checks.* Never let `mv` overwrite — that's how you lose files.

## When to Use

- Renaming CleanShot / screenshot folders by content
- Any image batch where the source filenames are timestamps and the user wants them human-scannable
- ≥ ~10 files (otherwise just rename them inline)
- Files include PNG/GIF and optionally MP4 or PDF (pipeline handles all four)
- Both `CleanShot ...` and Apple `Screenshot ...` filename prefixes are recognized in the same pass
- Files with a leading user-typed keyword prefix (e.g. `jojo travel CleanShot 2026-...png`) are recognized; the keywords are preserved and merged into the new name
- Files already in the renamed form (`App - Description - timestamp.ext`) are detected and skipped — re-running the skill on a folder is safe and idempotent

**Don't use for:**
- Code or text files — vision isn't needed
- Files where the name pattern is already meaningful
- Single-file rename (just do it directly)

## Workflow

```
1. Prep
   ├─ Extract first frame from each .mp4 (ffmpeg) and .pdf (sips) to /tmp/frames/<base>.jpg
   ├─ Resize every source image to max 1568px on long edge → /tmp/small/<base>.jpg
   └─ Build manifest TSV: <small_image_path>\t<original_filename>

2. Batch
   └─ Split manifest into N batches of ≤ 20 lines each (file: full-batch-NN)

3. Describe (parallel)
   └─ Dispatch N Haiku subagents (model: "haiku") in a single message
      Each agent: reads its batch manifest, uses Read on each image_path,
      writes desc-full-NN.tsv with: <original_filename>\t<6-8 word description>

4. Plan (Python)
   ├─ Aggregate all desc-*.tsv into desc-all.tsv
   ├─ Validate every line: 6+ words, alnum+space only, source exists, target doesn't,
   │  no plan-internal collisions
   ├─ Truncate descriptions to 8 words max, title-case
   └─ Write plan-full.tsv: <original>\t<new_name>

5. Execute (Python, NEVER bash)
   ├─ Read plan, for each line: pre-check src exists & dst doesn't, then os.rename
   ├─ Audit before/after file count — must be equal
   └─ Log failures, report ok/fail counts
```

## The Critical Gotchas (every one of these caused real pain)

1. **Read tool has an image-size cap.** Original Retina screenshots can exceed it. **Always downscale** to ≤ 1568px before handing to a subagent. Use `sips -Z 1568 -s format jpeg`.

2. **Vision API can't read .mp4 or multi-page .pdf directly.** Extract the first frame to a JPEG first (`ffmpeg -ss 1 -i in.mp4 -frames:v 1 out.jpg`, `sips -s format jpeg in.pdf --out out.jpg`).

3. **Bash regex with `[[ =~ ]]` + `BASH_REMATCH` does NOT work in zsh.** zsh uses `$match[1]` etc. instead. Pattern silently fails, target name becomes empty, multiple `mv`s collide on the same empty target, files vanish. **Use Python for any filename mutation.** No exceptions.

4. **`mv` silently overwrites.** A loop that constructs target names from a buggy parse will happily destroy your data. Use `mv -n` (no-clobber) in shell, or `os.rename` after `os.path.exists(dst)` check in Python. Never bare `mv`.

5. **Pre-flight the full plan in memory** before mutating the filesystem. Build a list of `(orig, new)` tuples; verify every `new` is unique within the plan, doesn't collide with anything in the destination directory, and that every `orig` exists. Only then start renaming.

6. **File-count audit.** Record `len(os.listdir(DEST))` before and after — must be equal. Any drop = data loss.

7. **iCloud-synced trees and Time Machine local snapshots:** files in the snapshot are *file-provider stubs*, not the bytes. `cat` / `cp` from a snapshot path inside an iCloud-synced folder returns "Operation timed out" with a 0-byte file. **External backups (Backblaze, Time Machine to a real disk) are the actual recovery source for iCloud data**, not local APFS snapshots.

8. **Bash background jobs in the Claude Code Bash tool can die silently.** A `while read` loop redirected from a file may exit immediately when run in the background. **Run renames foreground via Python** — it's the same code path locally and reliably runs to completion.

9. **Haiku occasionally returns the wrong filename extension** (the resized `.jpg` instead of the original `.png`). The plan-builder must accept that and try alternate extensions when the claimed source isn't found in the destination directory.

10. **Always preserve mp4/pdf source files** — the pipeline reads from the resized JPEG but renames the original mp4/pdf. Don't lose the source extension.

11. **macOS Screenshot files use U+202F (NARROW NO-BREAK SPACE) before AM/PM.** Apple's `Screenshot 2026-MM-DD at H.MM.SS PM.png` filenames have U+202F (not ASCII space) between the seconds and the meridiem marker. The Haiku subagent reliably normalizes it to ASCII space when echoing the filename into the desc TSV, so the desc-dictionary lookup fails silently — every Screenshot file is dropped from the plan with a misleading "NO_DESC" error and untouched on disk. **Fix:** normalize both sides of the lookup with `s.replace(" ", " ")` AND emit ASCII space in the new filename so the renamed file is keyboard-typable. Detect the offender with `python3 -c "import sys; print(repr(sys.argv[1]))" "filename"` — ` ` will appear in the output.

12. **Re-running the skill on a folder is safe iff the parser skips already-renamed files.** Without an `^App - .+ - timestamp\.ext$` skip rule, the parser will pile a second AI description into the name on every run. The pipeline detects and excludes these.

13. **Leading keyword prefix is part of the source signal.** When the user has hand-prefixed a file (e.g. `jojo travel flight ... CleanShot 2026-...png`), those keywords are user knowledge the AI doesn't have. Title-case them and prepend them to the AI description before assembling the new name. Don't drop them.

## Quick Reference

| Step | Command |
|---|---|
| Extract mp4 frame | `ffmpeg -y -ss 1 -i "$f" -frames:v 1 -q:v 3 "$out"` |
| Convert pdf to jpg | `sips -s format jpeg "$f" --out "$out"` |
| Resize for vision | `sips -Z 1568 -s format jpeg "$f" --out "$out"` |
| Split TSV into batches of 20 | `awk -v w=DIR 'BEGIN{n=1;c=0} {print > sprintf("%s/batch-%02d", w, n); c++; if(c>=20){c=0;n++}}'` |
| Dispatch agent | Agent tool, `subagent_type=general-purpose`, `model="haiku"`, `run_in_background=true` |
| Execute renames | Python `os.rename` with pre-existence check (NEVER bash `mv` in a loop) |

## Reusable Pipeline

The prep, plan, and rename phases are in `pipeline.py`. The dispatch phase is performed by Claude Code itself (Agent tool calls) and cannot be scripted from inside Python — that's the trade-off of option (b).

Run order:

```bash
# 1. Prep + batch
python3 ~/.claude/skills/screenshot-rename/pipeline.py prep \
    --src "/path/to/folder" --batch-size 19

# Now dispatch one Haiku Agent per /tmp/screenshot-rename/full-batch-NN file
# (Claude Code does this — see SKILL.md "Workflow" step 3)

# 2. After all desc-full-NN.tsv files exist:
python3 ~/.claude/skills/screenshot-rename/pipeline.py plan \
    --src "/path/to/folder"

# 3. Review the plan, then:
python3 ~/.claude/skills/screenshot-rename/pipeline.py execute \
    --src "/path/to/folder"
```

## Subagent Prompt Template

Use exactly this prompt for each batch (substitute the batch number):

```
Describe screenshots so they can be renamed.

Read the manifest at `/tmp/screenshot-rename/full-batch-NN`. Each line: `image_path<TAB>original_filename`.

For EACH line:
1. Use Read on `image_path` (first column) to view the image.
2. Generate a description of EXACTLY 6, 7, or 8 words describing "what app is shown and what the content is". Count your words. Be specific about app names when visible. Use only ASCII letters, numbers, and spaces — NO slashes, colons, dashes, quotes, special characters. Lowercase. 6-8 words.

Output: write `/tmp/screenshot-rename/desc-full-NN.tsv` via Write tool. Each line: `original_filename<TAB>description`. <count> lines total.

Then run `wc -l` on the output file to verify the line count.

Return only "DONE: <count> lines" or an error report.
```

Dispatch all batches **in a single message with multiple Agent tool calls** so they run in parallel. Use `run_in_background=true` so you can keep working.

## Common Mistakes

| Mistake | What goes wrong | Fix |
|---|---|---|
| `mv $f $newname` in a bash loop | One bug → silent overwrite → data loss | `os.rename` in Python with pre-existence check |
| Building target name with bash regex | zsh doesn't populate BASH_REMATCH; empty targets | Use Python `os.path.splitext` and string ops |
| Sending original Retina images to Read | "Image too large" error mid-batch, partial output | Resize to 1568px first |
| Sending .mp4 to vision | Read fails | Extract first frame to JPEG first |
| Skipping the file-count audit | Silent data loss goes unnoticed | `len(os.listdir(DEST))` before & after — must be equal |
| Trusting Haiku's filename column | 30%+ of entries may have wrong extension | Plan-builder tries alt extensions |
| Running rename loop in background `Bash run_in_background=true` | Background `while read` may exit immediately, 0 progress | Run via Python foreground (it's fast — `os.rename` is just a syscall) |
| Looking up Haiku's filename column verbatim | Apple Screenshot files contain U+202F (narrow no-break space); Haiku echoes it as ASCII space, lookup misses every Screenshot file | Normalize U+202F → ASCII space on both sides of the desc dict |
| Hardcoding a single `--prefix` (e.g. `CleanShot`) | Apple Screenshot files and user-prefixed files get silently excluded from the manifest | Parser accepts both `CleanShot` and `Screenshot` and an optional leading keyword phrase |
| Re-running the skill without an already-renamed skip rule | Each run prepends another description; names balloon | Detect `^App - .+ - timestamp\.ext$` and skip |

## Recovery — if something does go wrong

1. **Check `~/Library/Application Support/CleanShot/media/`** — CleanShot keeps a recent media history.
2. **Check external backups (Backblaze, Time Machine to physical disk)** — these contain real file bytes.
3. **Local APFS Time Machine snapshots are NOT useful for iCloud-synced files** — they store file-provider stubs that time out on read.
4. **Check icloud.com → Drive → Recently Deleted** — iCloud keeps deleted files for ~30 days, but `mv` overwrites are NOT "deletes" from iCloud's perspective and may not appear there.
5. **If a Screenshot rename appeared to fail silently** — check for U+202F in the source filename: `python3 -c "import os; [print(repr(n)) for n in os.listdir('.') if 'Screenshot' in n]"`. The ` ` shows up in the repr; the parser must normalize it.

## Real-World Impact

First run on 196 CleanShot files lost 4 of them due to the bash-regex-in-zsh gotcha (rule #3). After the rebuild with Python and `mv -n`, second run renamed 189 files cleanly with zero loss.

Third run (20 mixed CleanShot + Apple Screenshot + one user-prefixed file) hit the U+202F gotcha (rule #11) on first plan attempt — every Screenshot file was dropped from the plan with a NO_DESC error despite the description being present. Diagnosed via `repr()` of the live filename. After adding U+202F normalization, multi-prefix support, and keyword preservation, all 20 renamed in one pass.

This skill exists so those don't happen again.