commit cfa64a51f05ad53e17b7ece424a1b0739898a046
Author: fenix <fenix@librebits.info>
Date:   Mon Mar 16 12:28:01 2026 +0100

    Let's evolve our skills with Claude Code help

diff --git a/.claude-plugin/marketplace.json b/.claude-plugin/marketplace.json
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+{
+  "name": "fenix-skills",
+  "owner": {
+    "name": "Fénix",
+    "email": "fenix@local"
+  },
+  "metadata": {
+    "description": "Fénix's Claude Code skills — Emacs integration (forked from xenodium/emacs-skills) + custom productivity tools",
+    "version": "1.0.0"
+  },
+  "plugins": [
+    {
+      "name": "fenix-tools",
+      "description": "Fénix's Emacs integration and productivity skills for Claude Code",
+      "source": "./",
+      "strict": false,
+      "skills": [
+        "./skills/d2",
+        "./skills/describe",
+        "./skills/dired",
+        "./skills/emacsclient",
+        "./skills/extract-pdf-pages",
+        "./skills/file-links",
+        "./skills/gnuplot",
+        "./skills/highlight",
+        "./skills/mermaid",
+        "./skills/open",
+        "./skills/plantuml",
+        "./skills/select"
+      ]
+    }
+  ]
+}
diff --git a/README.md b/README.md
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+# Fenix Skills — Claude Code Plugin
+
+Custom Claude Code skills for Fénix's workflow.
+Includes all [xenodium/emacs-skills](https://github.com/xenodium/emacs-skills) (forked & rebranded) plus Fénix's own productivity tools.
+
+---
+
+## Plugin Structure
+
+```
+~/Emacs/fenix-skills/
+├── .claude-plugin/
+│   └── marketplace.json              # Plugin manifest
+├── README.md
+└── skills/
+    ├── d2/                           # /d2 — Create D2 diagrams
+    ├── describe/                     # /describe — Emacs describe-* lookups
+    ├── dired/                        # /dired — Open files in dired buffer
+    ├── emacsclient/                  # (auto) Always use emacsclient, not emacs
+    ├── extract-pdf-pages/            # /extract-pdf-pages — Extract page ranges with pdftk
+    ├── file-links/                   # (auto) Format file refs as markdown #L links
+    ├── gnuplot/                      # /gnuplot — Plot data with gnuplot
+    ├── highlight/                    # /highlight — Highlight regions in Emacs
+    ├── mermaid/                      # /mermaid — Create Mermaid diagrams
+    ├── open/                         # /open — Open files in Emacs buffers
+    ├── plantuml/                     # /plantuml — Create PlantUML diagrams
+    └── select/                       # /select — Select regions in Emacs
+```
+
+## Registration
+
+Registered in `~/.claude/settings.json` as:
+
+```json
+"extraKnownMarketplaces": {
+  "fenix-skills": {
+    "source": {
+      "source": "directory",
+      "path": "/home/fenix/Emacs/fenix-skills"
+    }
+  }
+}
+```
+
+```json
+"enabledPlugins": {
+  "fenix-tools@fenix-skills": true
+}
+```
+
+## Usage
+
+All slash-command skills are available **system-wide** in any Claude Code session:
+
+| Skill | Invocation | Description |
+|:---|:---:|:---|
+| **d2** | `/d2` | Create diagrams with D2 |
+| **describe** | `/describe` | Look up Emacs docs (functions, variables, keys) |
+| **dired** | `/dired` | Open recent files in Emacs dired buffer |
+| **emacsclient** | _(auto)_ | Always prefer `emacsclient` over `emacs` |
+| **extract-pdf-pages** | `/extract-pdf-pages` | Extract page range from PDF via `pdftk` |
+| **file-links** | _(auto)_ | Format file references as `file.py#L42` links |
+| **gnuplot** | `/gnuplot` | Plot data with gnuplot |
+| **highlight** | `/highlight` | Highlight line regions in Emacs buffers |
+| **mermaid** | `/mermaid` | Create Mermaid diagrams |
+| **open** | `/open` | Open files in Emacs (with optional line jump) |
+| **plantuml** | `/plantuml` | Create PlantUML diagrams |
+| **select** | `/select` | Select (mark) regions in Emacs buffers |
+
+## Origin
+
+- **Emacs skills** (d2, describe, dired, emacsclient, file-links, gnuplot, highlight, mermaid, open, plantuml, select) — forked from [xenodium/emacs-skills](https://github.com/xenodium/emacs-skills) by Alvaro Ramirez
+- **extract-pdf-pages** — original, requires `pdftk` (`apt install pdftk`)
+
+## Requirements
+
+- GNU Emacs with running server daemon (`emacsclient` accessible)
+- `pdftk` for PDF extraction skill
+- Claude Code with plugins enabled
diff --git a/skills/d2/SKILL.md b/skills/d2/SKILL.md
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+++ b/skills/d2/SKILL.md
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+---
+name: d2
+description: 'This skill should be used when the user invokes "/d2" to create a diagram from the current context using D2 and output the resulting image path.'
+tools: Bash
+disable-model-invocation: true
+---
+
+# Create diagrams with D2
+
+Create a diagram from the most recent interaction context using D2. Generate a PNG image and output it as a markdown image so it renders inline.
+
+## How to create a diagram
+
+1. Extract or derive diagrammable data from the current context.
+2. If the Emacs foreground color and background mode are not already known from a previous diagram in this session, query them:
+   ```sh
+   emacsclient --eval '(face-foreground (quote default))'
+   emacsclient --eval '(frame-parameter nil (quote background-mode))'
+   ```
+   The first returns a hex color like `"#eeffff"`. The second returns `dark` or `light`. Reuse both for all subsequent diagrams.
+3. Write a D2 file to a temporary file using the foreground color.
+4. Run D2 with `--theme 200` if background mode is `dark`, or `--theme 0` if `light`.
+5. Output the result as a markdown image on its own line:
+   ```
+   ![description](/tmp/agent-diagram-XXXX.png)
+   ```
+
+```sh
+# Use --theme 200 for dark, --theme 0 for light
+d2 --theme 200 --pad 40 /tmp/agent-diagram-XXXX.d2 /tmp/agent-diagram-XXXX.png
+```
+
+## D2 template
+
+Use `--theme 200` for dark or `--theme 0` for light, based on the Emacs background mode. Apply the queried foreground color to `style.font-color` and `style.stroke` on nodes and edges.
+
+```d2
+direction: right
+
+node1: Label {
+  style.font-color: "#eeffff"
+  style.fill: "#2d3748"
+  style.stroke: "#eeffff"
+}
+
+node2: Label {
+  style.font-color: "#eeffff"
+  style.fill: "#2d3748"
+  style.stroke: "#eeffff"
+}
+
+node1 -> node2: label {style.stroke: "#eeffff"; style.font-color: "#eeffff"}
+```
+
+## Rules
+
+- Query the Emacs foreground color once per session and reuse it for all subsequent diagrams. Only query again if the color is not already known.
+- Query the Emacs background mode once per session via `(frame-parameter nil 'background-mode)`. Use `--theme 200` for `dark` or `--theme 0` for `light`. Always use `--pad 40`.
+- Always use a timestamp in the filename (e.g., `/tmp/agent-diagram-$(date +%s).png`). Never use descriptive names.
+- Set the queried foreground color on `style.font-color` and `style.stroke` for all nodes and edges so the diagram is readable on the user's Emacs background.
+- Use meaningful fill colors to distinguish different types of elements.
+- After D2 runs successfully, output a markdown image (`![description](path)`) on its own line.
+- Choose an appropriate layout direction and structure for the data.
+- Include labels on edges when they add clarity.
+- If no diagrammable data exists in the recent context, inform the user.
diff --git a/skills/describe/SKILL.md b/skills/describe/SKILL.md
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+---
+name: describe
+description: 'This skill should be used when the user invokes "/describe" to look up Emacs documentation via emacsclient.'
+tools: Bash
+disable-model-invocation: true
+---
+
+# Look up Emacs documentation
+
+Look up Emacs documentation using `emacsclient --eval` and summarize the findings. The query is searched across multiple mechanisms (function, variable, face, key binding, and apropos) in one call, returning all findings as a single string.
+
+First, locate `agent-skill-describe.el` which lives alongside this skill file at `skills/describe/agent-skill-describe.el` in the emacs-skills plugin directory.
+
+```sh
+emacsclient --eval '
+(progn
+  (load "/path/to/skills/describe/agent-skill-describe.el" nil t)
+  (agent-skill-describe :query "dired-mark"))'
+```
+
+## Rules
+
+- Summarize the returned documentation for the user in the conversation.
+- Locate `agent-skill-describe.el` relative to this skill file's directory.
+- Run the `emacsclient --eval` command via the Bash tool.
diff --git a/skills/describe/agent-skill-describe.el b/skills/describe/agent-skill-describe.el
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+++ b/skills/describe/agent-skill-describe.el
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+(require 'cl-lib)
+
+(cl-defun agent-skill-describe (&key query)
+  "Look up QUERY across multiple Emacs documentation mechanisms.
+
+Searches for QUERY as a function, variable, and via apropos,
+returning all findings in a single string."
+  (let ((sym (intern-soft query))
+        (sections nil))
+    ;; Function documentation
+    (when (and sym (fboundp sym))
+      (push (format "## Function: %s\n\n%s\n\nSignature: %s\n\n%s"
+                    query
+                    (cond ((subrp (symbol-function sym)) "Built-in function")
+                          ((macrop sym) "Macro")
+                          ((commandp sym) "Interactive command")
+                          (t "Function"))
+                    (or (help-function-arglist sym t) "()")
+                    (or (documentation sym t) "No documentation available."))
+            sections))
+    ;; Variable documentation
+    (when (and sym (boundp sym))
+      (let ((val (symbol-value sym)))
+        (push (format "## Variable: %s\n\nCurrent value: %s\n\n%s"
+                      query
+                      (let ((printed (format "%S" val)))
+                        (if (> (length printed) 200)
+                            (concat (substring printed 0 200) "...")
+                            printed))
+                      (or (documentation-property sym 'variable-documentation t)
+                          "No documentation available."))
+              sections)))
+    ;; Face documentation
+    (when (and sym (facep sym))
+      (push (format "## Face: %s\n\n%s"
+                    query
+                    (or (documentation-property sym 'face-documentation t)
+                        "No documentation available."))
+            sections))
+    ;; Key binding (if it looks like a key sequence)
+    (when (string-match-p "\\`[CMSs]-\\|\\`<" query)
+      (let* ((keyseq (ignore-errors (kbd query)))
+             (binding (and keyseq (key-binding keyseq))))
+        (when binding
+          (push (format "## Key binding: %s\n\n%s runs `%s'\n\n%s"
+                        query query binding
+                        (or (documentation binding t)
+                            "No documentation available."))
+                sections))))
+    ;; Apropos matches (up to 20)
+    (let ((matches nil))
+      (mapatoms
+       (lambda (s)
+         (when (and (string-match-p (regexp-quote query) (symbol-name s))
+                    (not (eq s sym))
+                    (or (fboundp s) (boundp s)))
+           (push (format "  %s%s"
+                         (symbol-name s)
+                         (cond ((and (fboundp s) (boundp s))
+                                " [function, variable]")
+                               ((fboundp s) " [function]")
+                               (t " [variable]")))
+                 matches))))
+      (when matches
+        (let ((sorted (sort matches #'string<)))
+          (push (format "## Related symbols\n\n%s%s"
+                        (mapconcat #'identity (seq-take sorted 20) "\n")
+                        (if (> (length sorted) 20)
+                            (format "\n  ... and %d more" (- (length sorted) 20))
+                          ""))
+                sections))))
+    (if sections
+        (mapconcat #'identity (nreverse sections) "\n\n")
+      (format "No documentation found for \"%s\"." query))))
+
+(provide 'agent-skill-describe)
diff --git a/skills/dired/SKILL.md b/skills/dired/SKILL.md
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+---
+name: dired
+description: 'This skill should be used when the user invokes "/dired" to open files from the latest interaction in an Emacs dired buffer via emacsclient.'
+tools: Bash
+disable-model-invocation: true
+---
+
+# Open files in Emacs dired
+
+Open files from the most recent interaction in an Emacs dired buffer using `emacsclient --eval`. Only include files relevant to the latest interaction (files just generated, edited, listed, or produced by the most recent tool output), not all files mentioned throughout the conversation.
+
+## Strategy
+
+Determine whether the relevant files all reside in the same directory or span multiple directories, then call `agent-skill-dired` accordingly.
+
+- **Same directory**: `:dir` is the directory, `:files` are basenames. Opens dired at that directory with the files marked in context.
+- **Multiple directories**: `:dir` is the common ancestor, `:files` are relative paths. Creates a curated `*agent-files*` buffer with all files marked.
+
+First, locate `agent-skill-dired.el` which lives alongside this skill file at `skills/dired/agent-skill-dired.el` in the emacs-skills plugin directory.
+
+```sh
+emacsclient --eval '
+(progn
+  (load "/path/to/skills/dired/agent-skill-dired.el" nil t)
+  (agent-skill-dired
+    :dir "/path/to/directory"
+    :files (quote ("file1.txt"
+                   "file2.txt"
+                   "file3.txt"))))'
+```
+
+## Rules
+
+- Use relative paths in `:files` relative to `:dir`.
+- Locate `agent-skill-dired.el` relative to this skill file's directory.
+- If no relevant files exist in the recent interaction, inform the user.
+- Run the `emacsclient --eval` command via the Bash tool.
diff --git a/skills/dired/agent-skill-dired.el b/skills/dired/agent-skill-dired.el
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+++ b/skills/dired/agent-skill-dired.el
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+(require 'cl-lib)
+(require 'dired)
+
+(cl-defun agent-skill-dired (&key dir files)
+  "Open a dired buffer at DIR with FILES marked.
+
+When all files share the same parent directory, DIR is that
+directory and FILES are basenames shown in context.
+
+When files span multiple directories, DIR is the common ancestor
+and FILES are relative paths.  A curated `*agent-files*' buffer
+is created instead."
+  (let ((same-dir-p (cl-every (lambda (f) (not (string-match-p "/" f))) files)))
+    (if same-dir-p
+        (progn
+          (dired dir)
+          (dired-unmark-all-marks)
+          (dolist (file files)
+            (dired-goto-file (expand-file-name file dir))
+            (dired-mark 1)))
+      (let ((default-directory (file-name-as-directory dir)))
+        (dired (cons "*agent-files*" files))
+        (dired-unmark-all-marks)
+        (dired-toggle-marks)))))
+
+(provide 'agent-skill-dired)
diff --git a/skills/emacsclient/SKILL.md b/skills/emacsclient/SKILL.md
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+++ b/skills/emacsclient/SKILL.md
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+---
+name: emacsclient
+description: 'Always use emacsclient instead of emacs. This applies to all Emacs operations: user requests, byte compilation, check-parens, running ERT tests, and any other elisp evaluation.'
+tools: Bash
+---
+
+# Always use emacsclient
+
+The user has an Emacs server running. **All** Emacs operations must go through `emacsclient`, never `emacs` or `emacs --batch`. This includes both user-requested actions and agent-initiated operations like byte compilation, syntax checking, or running tests.
+
+## Examples
+
+- Open a file: `emacsclient --no-wait "/path/to/file"`
+- Evaluate elisp: `emacsclient --eval '(some-function)'`
+- Open at a line: `emacsclient --no-wait +42 "/path/to/file"`
+- Byte compile a file:
+  ```sh
+  emacsclient --eval '
+  (byte-compile-file "/path/to/file.el")'
+  ```
+- Check parentheses:
+  ```sh
+  emacsclient --eval '
+  (with-temp-buffer
+    (insert-file-contents "/path/to/file.el")
+    (check-parens))'
+  ```
+- Run ERT tests:
+  ```sh
+  emacsclient --eval '
+  (progn
+    (load "/path/to/test-file.el" nil t)
+    (ert-run-tests-batch-and-exit "pattern"))'
+  ```
+
+## Rules
+
+- Always use `emacsclient`, never `emacs` or `emacs --batch`.
+- Use `--no-wait` when opening files so the command returns immediately.
+- Use `--eval` when evaluating elisp.
+- Always format `--eval` elisp across multiple lines with proper indentation.
+- Run `emacsclient` commands via the Bash tool.
diff --git a/skills/extract-pdf-pages/SKILL.md b/skills/extract-pdf-pages/SKILL.md
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+++ b/skills/extract-pdf-pages/SKILL.md
@@ -0,0 +1,32 @@
+---
+name: extract-pdf-pages
+description: 'Use when the user invokes "/extract-pdf-pages" to extract a page range from a PDF file using pdftk.'
+tools: Bash
+disable-model-invocation: true
+---
+
+# Extract PDF Pages
+
+Extract a page range from a PDF file into a new PDF using `pdftk`.
+
+## Usage
+
+When invoked, ask the user for (if not already provided):
+1. **Source PDF** — absolute path to the input PDF file
+2. **Page range** — start and end pages (e.g., `200-204`)
+3. **Output filename** — name for the new PDF (defaults to current working directory)
+
+## Command
+
+```bash
+pdftk "<source_pdf>" cat <start>-<end> output "<output_path>"
+```
+
+## Rules
+
+- Always use absolute paths for both source and output files.
+- If the user provides only a filename (no directory), place the output in the current working directory.
+- If the output file already exists, warn the user before overwriting.
+- Support multiple extractions in a single invocation (run them in parallel).
+- After extraction, confirm with file size: `ls -lh "<output_path>"`
+- Requires `pdftk` to be installed (`apt install pdftk`).
diff --git a/skills/file-links/SKILL.md b/skills/file-links/SKILL.md
new file mode 100644
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--- /dev/null
+++ b/skills/file-links/SKILL.md
@@ -0,0 +1,48 @@
+---
+name: file-links
+description: 'When referencing files, format them as markdown links with line numbers using GitHub-style #L syntax.'
+---
+
+# Format file references as markdown links
+
+When referencing files in your output, always format them as markdown links. Use the GitHub-style `#L` fragment for line numbers.
+
+## Format
+
+With a line number:
+
+```
+[filename.el:42](relative/path/to/filename.el#L42)
+```
+
+With a line range:
+
+```
+[filename.el:42-50](relative/path/to/filename.el#L42-L50)
+```
+
+Without a line number:
+
+```
+[filename.el](relative/path/to/filename.el)
+```
+
+## Important
+
+- The link text uses `:` for line numbers (e.g., `filename.el:42`).
+- The URL uses `#L` for line numbers (e.g., `filename.el#L42`).
+- For ranges, the link text uses `-` (e.g., `filename.el:42-50`) and the URL uses `-L` (e.g., `filename.el#L42-L50`).
+- The range must appear in both the link text and the URL.
+
+Do NOT do this:
+
+```
+[filename.el#L42-L50](filename.el#L42)
+```
+
+## Rules
+
+- Use paths relative to the project root.
+- Include line numbers when they are relevant (e.g., error locations, function definitions, modified lines).
+- Use line ranges when referring to a block of code.
+- The link text should be the filename (or relative path if needed for clarity) followed by the line number.
diff --git a/skills/gnuplot/SKILL.md b/skills/gnuplot/SKILL.md
new file mode 100644
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--- /dev/null
+++ b/skills/gnuplot/SKILL.md
@@ -0,0 +1,60 @@
+---
+name: gnuplot
+description: 'This skill should be used when the user invokes "/gnuplot" to plot data from the current context using gnuplot and output the resulting image path.'
+tools: Bash
+disable-model-invocation: true
+---
+
+# Plot data with gnuplot
+
+Plot data from the most recent interaction context using gnuplot. Generate a PNG image with a transparent background and output it as a markdown image so it renders inline.
+
+## How to plot
+
+1. Extract or derive plottable data from the current context.
+2. If the Emacs foreground color is not already known from a previous plot in this session, query it:
+   ```sh
+   emacsclient --eval '
+   (face-foreground (quote default))'
+   ```
+   This returns a hex color like `"#eeffff"`. Reuse it for all subsequent plots.
+3. Write a gnuplot script to a temporary file using that color.
+4. Run gnuplot on the script.
+5. Output the result as a markdown image on its own line:
+   ```
+   ![description](/tmp/agent-plot-XXXX.png)
+   ```
+
+```sh
+gnuplot /tmp/agent-plot-XXXX.gp
+```
+
+## Gnuplot script template
+
+```gnuplot
+set terminal pngcairo transparent enhanced size 800,500
+set output "/tmp/agent-plot-XXXX.png"
+
+FG = "#eeffff"  # from emacsclient query
+set border lc rgb FG
+set key textcolor rgb FG
+set xlabel textcolor rgb FG
+set ylabel textcolor rgb FG
+set title textcolor rgb FG
+set xtics textcolor rgb FG
+set ytics textcolor rgb FG
+
+# ... plot commands using the data ...
+```
+
+## Rules
+
+- Query the Emacs foreground color once per session and reuse it for all subsequent plots. Only query again if the color is not already known.
+- Always use `pngcairo transparent` terminal for transparent background.
+- Always use a timestamp in the filename (e.g., `/tmp/agent-plot-$(date +%s).png`). Never use descriptive names like `agent-plot-lorenz.png`.
+- Use inline data (`$DATA << EOD ... EOD`) when practical. For large datasets, write a separate data file.
+- After gnuplot runs successfully, output a markdown image (`![description](path)`) on its own line.
+- Choose an appropriate plot type for the data (lines, bars, histogram, scatter, etc.).
+- Include a title, axis labels, and a legend when they add clarity.
+- Use `enhanced` text mode for subscripts/superscripts when needed.
+- If no plottable data exists in the recent context, inform the user.
diff --git a/skills/highlight/SKILL.md b/skills/highlight/SKILL.md
new file mode 100644
index 0000000..2b26d67
--- /dev/null
+++ b/skills/highlight/SKILL.md
@@ -0,0 +1,39 @@
+---
+name: highlight
+description: 'This skill should be used when the user invokes "/highlight" to highlight relevant regions in one or more files in Emacs via emacsclient.'
+tools: Bash
+disable-model-invocation: true
+---
+
+# Highlight regions in Emacs
+
+Highlight relevant regions in one or more files in Emacs using `emacsclient --eval`. Files are opened in a temporary read-only minor mode with highlighted overlays. The user presses `q` to exit the mode and remove all highlights in that buffer.
+
+Determine the relevant files and line ranges from the most recent interaction context.
+
+## How to highlight
+
+First, determine the path to `agent-skill-highlight.el`. It lives alongside this skill file at `skills/highlight/agent-skill-highlight.el` in the emacs-skills plugin directory.
+
+```sh
+emacsclient --eval '
+(progn
+  (load "/path/to/skills/highlight/agent-skill-highlight.el" nil t)
+  (agent-skill-highlight
+    :files (quote (("/path/to/file1.el"
+                    :regions ((:start 90 :lines 18)
+                              (:start 114 :lines 49)))
+                   ("/path/to/file2.el"
+                    :regions ((:start 94 :lines 18)))))))'
+```
+
+- `:start` is the 1-indexed line number.
+- `:lines` is the number of lines to highlight from that start line.
+- Add as many files and regions as needed.
+
+## Rules
+
+- Use absolute paths for files.
+- Locate `agent-skill-highlight.el` relative to this skill file's directory.
+- If no relevant files or regions exist in the recent interaction, inform the user.
+- Run the `emacsclient --eval` command via the Bash tool.
diff --git a/skills/highlight/agent-skill-highlight.el b/skills/highlight/agent-skill-highlight.el
new file mode 100644
index 0000000..6fe1a9f
--- /dev/null
+++ b/skills/highlight/agent-skill-highlight.el
@@ -0,0 +1,53 @@
+(eval-when-compile
+  (require 'cl-lib))
+(require 'hi-lock)
+
+(defvar-local agent-skill-highlight--overlays nil)
+(defvar-local agent-skill-highlight--was-read-only nil)
+
+(defun agent-skill-highlight--remove-overlays ()
+  (mapc #'delete-overlay agent-skill-highlight--overlays)
+  (setq agent-skill-highlight--overlays nil))
+
+(defun agent-skill-highlight-exit ()
+  (interactive)
+  (agent-skill-highlight-mode -1))
+
+(define-minor-mode agent-skill-highlight-mode
+  "Temporary read-only mode with highlighted regions. Press q to exit."
+  :lighter " Highlight"
+  :keymap (let ((map (make-sparse-keymap)))
+            (define-key map (kbd "q") #'agent-skill-highlight-exit)
+            map)
+  (if agent-skill-highlight-mode
+      (progn
+        (setq agent-skill-highlight--was-read-only buffer-read-only)
+        (read-only-mode 1)
+        (message "Press q to exit highlights"))
+    (agent-skill-highlight--remove-overlays)
+    (unless agent-skill-highlight--was-read-only
+      (read-only-mode -1))))
+
+(cl-defun agent-skill-highlight (&key files)
+  "Highlight regions in FILES.
+
+FILES is a list of (FILE-PATH :regions REGIONS) where REGIONS is
+a list of (:start LINE :lines COUNT)."
+  (dolist (file-spec files)
+    (let ((file-path (car file-spec))
+          (regions (plist-get (cdr file-spec) :regions)))
+      (find-file file-path)
+      (dolist (region regions)
+        (let* ((start-line (plist-get region :start))
+               (num-lines (plist-get region :lines))
+               (ov (make-overlay
+                    (progn (goto-char (point-min))
+                           (forward-line (1- start-line))
+                           (point))
+                    (progn (forward-line num-lines)
+                           (point)))))
+          (overlay-put ov 'face 'hi-yellow)
+          (push ov agent-skill-highlight--overlays)))
+      (agent-skill-highlight-mode 1))))
+
+(provide 'agent-skill-highlight)
diff --git a/skills/mermaid/SKILL.md b/skills/mermaid/SKILL.md
new file mode 100644
index 0000000..ee65f9f
--- /dev/null
+++ b/skills/mermaid/SKILL.md
@@ -0,0 +1,86 @@
+---
+name: mermaid
+description: 'This skill should be used when the user invokes "/mermaid" to create a diagram from the current context using Mermaid and output the resulting image path.'
+tools: Bash
+disable-model-invocation: true
+---
+
+# Create diagrams with Mermaid
+
+Create a diagram from the most recent interaction context using Mermaid. Generate a PNG image with a transparent background and output it as a markdown image so it renders inline.
+
+## How to create a diagram
+
+1. Extract or derive diagrammable data from the current context.
+2. If the Emacs foreground color and background mode are not already known from a previous diagram in this session, query them:
+   ```sh
+   emacsclient --eval '(face-foreground (quote default))'
+   emacsclient --eval '(frame-parameter nil (quote background-mode))'
+   ```
+   The first returns a hex color like `"#eeffff"`. The second returns `dark` or `light`. Reuse both for all subsequent diagrams.
+3. Write a Mermaid file to a temporary file.
+4. Write a JSON config file that overrides theme variables with the queried foreground color. Set `"theme"` to `"dark"` or `"default"` based on the background mode.
+5. Run `mmdc` with `-t dark` if background mode is `dark`, or `-t default` if `light`.
+6. Output the result as a markdown image on its own line:
+   ```
+   ![description](/tmp/agent-diagram-XXXX.png)
+   ```
+
+```sh
+# Use -t dark for dark, -t default for light
+PUPPETEER_EXECUTABLE_PATH=/opt/homebrew/bin/chromium mmdc \
+  -i /tmp/agent-diagram-XXXX.mmd \
+  -o /tmp/agent-diagram-XXXX.png \
+  -t dark -b transparent --scale 2 \
+  --configFile /tmp/agent-diagram-XXXX-config.json
+```
+
+## Mermaid config template
+
+Write this JSON config file to apply the Emacs foreground color. Replace `#eeffff` with the queried color. Set `"theme"` to `"dark"` or `"default"` based on the Emacs background mode.
+
+```json
+{
+  "theme": "dark",
+  "themeVariables": {
+    "primaryTextColor": "#eeffff",
+    "secondaryTextColor": "#eeffff",
+    "tertiaryTextColor": "#eeffff",
+    "primaryBorderColor": "#eeffff",
+    "lineColor": "#eeffff",
+    "textColor": "#eeffff",
+    "actorTextColor": "#eeffff",
+    "actorBorder": "#eeffff",
+    "signalColor": "#eeffff",
+    "signalTextColor": "#eeffff",
+    "labelTextColor": "#eeffff",
+    "loopTextColor": "#eeffff",
+    "noteTextColor": "#eeffff",
+    "noteBorderColor": "#eeffff",
+    "sectionTextColor": "#eeffff",
+    "titleColor": "#eeffff"
+  }
+}
+```
+
+## Mermaid diagram template
+
+```mermaid
+sequenceDiagram
+    participant a as Alice
+    participant b as Bob
+    a->>b: Hello
+    b-->>a: Hi back
+```
+
+## Rules
+
+- Query the Emacs foreground color once per session and reuse it for all subsequent diagrams. Only query again if the color is not already known.
+- Query the Emacs background mode once per session via `(frame-parameter nil 'background-mode)`. Use `-t dark` for `dark` or `-t default` for `light`. Always use `-b transparent --scale 2`.
+- Always use `PUPPETEER_EXECUTABLE_PATH=/opt/homebrew/bin/chromium` when invoking `mmdc`.
+- Always write a JSON config file with `themeVariables` set to the queried foreground color and pass it via `--configFile`.
+- Always use a timestamp in the filename (e.g., `/tmp/agent-diagram-$(date +%s).png`). Never use descriptive names.
+- After mmdc runs successfully, output a markdown image (`![description](path)`) on its own line.
+- Choose an appropriate diagram type for the data (sequence, flowchart, class, state, er, gantt, etc.).
+- Include a title when it adds clarity.
+- If no diagrammable data exists in the recent context, inform the user.
diff --git a/skills/open/SKILL.md b/skills/open/SKILL.md
new file mode 100644
index 0000000..3f8018c
--- /dev/null
+++ b/skills/open/SKILL.md
@@ -0,0 +1,35 @@
+---
+name: open
+description: 'This skill should be used when the user invokes "/open" to open files from the latest interaction in Emacs buffers via emacsclient.'
+tools: Bash
+disable-model-invocation: true
+---
+
+# Open files in Emacs
+
+Open files from the most recent interaction in Emacs buffers using `emacsclient --eval`. Only include files relevant to the latest interaction (files just generated, edited, listed, or produced by the most recent tool output), not all files mentioned throughout the conversation.
+
+## How to open
+
+First, locate `agent-skill-open.el` which lives alongside this skill file at `skills/open/agent-skill-open.el` in the emacs-skills plugin directory.
+
+Each file spec in `:files` is either a string (file path) or a plist with `:file` and optional `:line`.
+
+```sh
+emacsclient --eval '
+(progn
+  (load "/path/to/skills/open/agent-skill-open.el" nil t)
+  (agent-skill-open
+    :files (quote ((:file "/path/to/file1.txt"
+                    :line 42)
+                   "/path/to/file2.txt"
+                   "/path/to/file3.txt"))))'
+```
+
+## Rules
+
+- Use absolute paths for files.
+- Use `:line` when a specific line is relevant (e.g., an error location or a newly added function).
+- Locate `agent-skill-open.el` relative to this skill file's directory.
+- If no relevant files exist in the recent interaction, inform the user.
+- Run the `emacsclient --eval` command via the Bash tool.
diff --git a/skills/open/agent-skill-open.el b/skills/open/agent-skill-open.el
new file mode 100644
index 0000000..924a786
--- /dev/null
+++ b/skills/open/agent-skill-open.el
@@ -0,0 +1,18 @@
+(require 'cl-lib)
+
+(cl-defun agent-skill-open (&key files)
+  "Open FILES in Emacs buffers.
+
+FILES is a list of file specs.  Each spec is either a string
+\(file path) or a plist (:file PATH :line LINE)."
+  (dolist (spec files)
+    (if (stringp spec)
+        (find-file spec)
+      (let ((file (plist-get spec :file))
+            (line (plist-get spec :line)))
+        (find-file file)
+        (when line
+          (goto-char (point-min))
+          (forward-line (1- line)))))))
+
+(provide 'agent-skill-open)
diff --git a/skills/plantuml/SKILL.md b/skills/plantuml/SKILL.md
new file mode 100644
index 0000000..841c5df
--- /dev/null
+++ b/skills/plantuml/SKILL.md
@@ -0,0 +1,82 @@
+---
+name: plantuml
+description: 'This skill should be used when the user invokes "/plantuml" to create a diagram from the current context using PlantUML and output the resulting image path.'
+tools: Bash
+disable-model-invocation: true
+---
+
+# Create diagrams with PlantUML
+
+Create a diagram from the most recent interaction context using PlantUML. Generate a PNG image with a transparent background and output it as a markdown image so it renders inline.
+
+## How to create a diagram
+
+1. Extract or derive diagrammable data from the current context.
+2. If the Emacs foreground color is not already known from a previous diagram in this session, query it:
+   ```sh
+   emacsclient --eval '
+   (face-foreground (quote default))'
+   ```
+   This returns a hex color like `"#eeffff"`. Reuse it for all subsequent diagrams.
+3. Write a PlantUML file to a temporary file using that color.
+4. Run PlantUML on the file.
+5. Output the result as a markdown image on its own line:
+   ```
+   ![description](/tmp/agent-diagram-XXXX.png)
+   ```
+
+```sh
+plantuml -tpng /tmp/agent-diagram-XXXX.puml
+```
+
+## PlantUML template
+
+```plantuml
+@startuml
+skinparam backgroundColor transparent
+skinparam shadowing true
+skinparam roundcorner 10
+skinparam defaultFontName "Helvetica"
+skinparam defaultFontColor #eeffff
+
+' Set foreground color on all element types
+skinparam titleFontColor #eeffff
+skinparam sequenceLifeLineBorderColor #eeffff
+skinparam sequenceArrowColor #eeffff
+skinparam sequenceGroupHeaderFontColor #eeffff
+skinparam sequenceGroupBorderColor #eeffff
+skinparam sequenceDividerFontColor #eeffff
+skinparam sequenceDividerBorderColor #eeffff
+skinparam actorBorderColor #eeffff
+skinparam actorFontColor #eeffff
+skinparam participantFontColor #eeffff
+skinparam participantBorderColor #eeffff
+skinparam collectionsFontColor #eeffff
+skinparam collectionsBorderColor #eeffff
+skinparam noteFontColor #eeffff
+skinparam noteBorderColor #eeffff
+skinparam arrowFontColor #eeffff
+skinparam classFontColor #eeffff
+skinparam classBorderColor #eeffff
+skinparam classAttributeFontColor #eeffff
+skinparam packageFontColor #eeffff
+skinparam packageBorderColor #eeffff
+skinparam componentFontColor #eeffff
+skinparam componentBorderColor #eeffff
+skinparam interfaceFontColor #eeffff
+skinparam interfaceBorderColor #eeffff
+
+' ... diagram content ...
+@enduml
+```
+
+## Rules
+
+- Query the Emacs foreground color once per session and reuse it for all subsequent diagrams. Only query again if the color is not already known.
+- Always use `skinparam backgroundColor transparent` for transparent background.
+- Always use a timestamp in the filename (e.g., `/tmp/agent-diagram-$(date +%s).png`). Never use descriptive names.
+- Set the queried foreground color on `defaultFontColor` and all relevant `skinparam` entries for borders, arrows, and text so the diagram is readable on the user's Emacs background.
+- After PlantUML runs successfully, output a markdown image (`![description](path)`) on its own line.
+- Choose an appropriate diagram type for the data (sequence, class, component, activity, state, etc.).
+- Include a title when it adds clarity.
+- If no diagrammable data exists in the recent context, inform the user.
diff --git a/skills/select/SKILL.md b/skills/select/SKILL.md
new file mode 100644
index 0000000..9eb49da
--- /dev/null
+++ b/skills/select/SKILL.md
@@ -0,0 +1,42 @@
+---
+name: select
+description: 'This skill should be used when the user invokes "/select" to open one or more files in Emacs and select a region relevant to the current discussion via emacsclient.'
+tools: Bash
+disable-model-invocation: true
+---
+
+# Select region in Emacs
+
+Open one or more files in Emacs and select (activate the region around) the code or text most relevant to the current discussion using `emacsclient --eval`. This allows the user to immediately act on the selection: narrow, copy, refactor, comment, etc.
+
+Determine the relevant files and line ranges from the most recent interaction context.
+
+## How to select
+
+First, locate `agent-skill-select.el` which lives alongside this skill file at `skills/select/agent-skill-select.el` in the emacs-skills plugin directory.
+
+```sh
+emacsclient --eval '
+(progn
+  (load "/path/to/skills/select/agent-skill-select.el" nil t)
+  (agent-skill-select
+    :selections (quote (("/path/to/file1.el"
+                         :start 10
+                         :end 25)
+                        ("/path/to/file2.el"
+                         :start 5
+                         :end 12)))))'
+```
+
+- `:start` is the 1-indexed start line.
+- `:end` is the 1-indexed end line.
+- The last file visited will have the visually active region. Other files have mark and point set (use `C-x C-x` to reactivate when switching to them).
+
+## Rules
+
+- Use absolute paths for files.
+- Choose the region most relevant to the current discussion (e.g., a function just modified, a block with an error, code just generated).
+- If no specific region is apparent, select the entire relevant function or block.
+- Locate `agent-skill-select.el` relative to this skill file's directory.
+- If no relevant files or regions exist in the recent interaction, inform the user.
+- Run the `emacsclient --eval` command via the Bash tool.
diff --git a/skills/select/agent-skill-select.el b/skills/select/agent-skill-select.el
new file mode 100644
index 0000000..167491e
--- /dev/null
+++ b/skills/select/agent-skill-select.el
@@ -0,0 +1,19 @@
+(require 'cl-lib)
+
+(cl-defun agent-skill-select (&key selections)
+  "Open files in Emacs and select a region in each.
+
+SELECTIONS is a list of (FILE :start LINE :end LINE)."
+  (dolist (sel selections)
+    (let ((file (car sel))
+          (start (plist-get (cdr sel) :start))
+          (end (plist-get (cdr sel) :end)))
+      (find-file file)
+      (goto-char (point-min))
+      (forward-line (1- start))
+      (set-mark (point))
+      (forward-line (- end start))
+      (end-of-line)
+      (activate-mark))))
+
+(provide 'agent-skill-select)