remove todo

can't find John's post on linkedin

Makefile

@@ -1,6 +1,6 @@
 # Makefile for Firehose monorepo
 
-.PHONY: check precommit deps compile test format
+.PHONY: check precommit deps compile test test-elisp format
 
 # Common check target that runs all static analysis
 check:
@@ -23,6 +23,10 @@ test:
 	@make -C app test
 	@make -C blogex test
 
+# Run Emacs Lisp tests for roam-export-blog (requires emacs on PATH)
+test-elisp:
+	emacs --batch -Q -l org -l ox-md -l scripts/roam-export-blog.el -l scripts/roam-export-blog-test.el -f ert-run-tests-batch-and-exit
+
 # Format code
 format:
 	@make -C app format

app/priv/blog/engineering/2026/10-08-will-it-blend.md

@@ -0,0 +1,50 @@
+%{
+  title: "Will It Blend?",
+  author: "Willem van den Ende",
+  tags: ~w(AI pi.dev ComprehensionMaxxing),
+  description: "Will it Blend was a series of videos promoting a blender brand, in which various unlikely objects were put in a blender to see if they would blend.",
+  image: "/images/blog/2026/will-it-blend.svg",
+  published: true
+}
+---
+
+**Problem** You find something interesting, but don't completely understand it, or are not sure where to start.
+
+**Solution** Point your coding agent at the thing you read (a blog post, research paper, product announcement) and build something so that you can play with it.
+
+Will it Blend was [a series of infomercials](https://en.wikipedia.org/wiki/Will_It_Blend%3F) promoting a blender brand, in which various unlikely objects, such as tablets, were put in a blender to see if they would blend.
+
+![will-it-blend](/images/blog/2026/will-it-blend.svg)
+
+I like it as a _metaphor_ for trying to get something to work that you have just come across. I often use it when reading about the new hot AI thing of the week (say decision models a couple of weeks ago). I’ll go and look for an open source implementation and have a play with it, asking my coding agent for help installing it and coming up with a micro project I can do with it.
+
+Worst case I lost half an hour to an hour, and put the idea back on the backburner. But more often than not, I get something out of it that I can take forward: working software and better, more grounded, understanding of a topic.
+
+
+## Examples of when I used this
+
+I use this all the time now. And so do other people, it is not that original. I want to encourage you to see if things blend too, only takes half an hour or so.
+
+### Decision models
+For instance, a day after [Jev](https://en.wikipedia.org/wiki/Jev_(AI_model))came out, Laya popped up on Reddit. I cloned the repository, opened Pi and asked some questions about what you could do with it. Then I had a look at the example code on the Laya page, used my coding agent to run it, had a chat about how I could use it in a coding agent, and had the agent make some sample questions with sample data. I also wondered why it was taking so long to start, got the coding agent to reduce startup by 40 times (28 seconds to about 0.6 seconds or so), and I learnt in the process that this was a BERT model with some pre-training. I had seen BERT’s but not played with one in the wild before. This enabled me to write some comments on LinkedIn, and learn, indirectly, about my mistakes :-). Not bad for an hour or two on a sunday afternoon.
+
+### Getting started with a local model in an open coding agent
+Another example would be John Nolan , who put [my post on a local coding agent on Mac OS](/blog/engineering/my-local-agentic-dev-setup-today) through his coding agent to get Pi + local llms set up on his machine. I liked this, because this is also how I got started with making my own coding agent, and later installing Pi. With a coding agent in hand, and some vigilance or sandboxing, this is not much time well spent.
+
+## Background
+
+I learnt this in the spring of 2025 through  Julia Turc, probably from her video on  [Mixture of Experts: How LLMs Are Getting Smarter Without Getting Slower](https://www.youtube.com/watch?v=7yR5ScbK1qk). In this video, Julia takes a 1991 research paper on mixture of experts, pulls it through ChatGPT (this is several hundred AI summer years ago) and creates an executable Collab Notebook out of it.
+
+I wrote a comment at the time:
+
+> +1. I was wondering if llms would make it easier to implement papers (something I haven’t done in a while), and later that day, youtube surfaced this video with a live demo. I came for the mixture of experts explanation and stayed for the implementation and paper reading. It is insightful to see what you look at in a paper.
+
+I was primed for this by  Katherine Breslin’s talk at Agile Manchester 2025 (spring, this is important in AI summer years), in which she mentioned making a voice assistant in an afternoon on her own, something which had taken the Alexa team (on which she worked) 150+ people and multiple years.
+
+## Your turn
+
+Do you have research papers, blog posts or videos that leave you wondering? Wonder no more. These days I often start with putting my question in a (gemini) notebook, getting a summary, finding more sources, and asking questions. Then I take a summary document to my coding agent, refer to that in an initial prompt and then it usually works.  I create a new git repository for every project, making small commits as  I go. Often [with tests](/blog/engineering/synthetic-tdd): they make it easy to get started, express expectations, and keep going if the experiment is a success.
+
+If you want specifics on what I use now: I use [Pi](/blog/engineering/tag/pi.dev) as coding agent. Models that I can run on a 64GB mac (e.g. Qwen 3.8 27B or 3.6 35B) are usually plenty. When I want it faster, or with less fan noise, I use a hosted GLM 5.3 Flash.
+
+I hope you find this useful and will see if something you are curious about will Blend. Happy blending!

scripts/.gitignore

@@ -0,0 +1 @@
+*.elc

scripts/roam-export-blog-test.el

@@ -0,0 +1,188 @@
+;;; roam-export-blog-test.el --- ERT tests for roam-export-blog -*- lexical-binding: t; -*-
+
+;;; Commentary:
+
+;; Run with:
+;;   emacs --batch -Q -l org -l ox-md -l scripts/roam-export-blog.el \
+;;     -l scripts/roam-export-blog-test.el -f ert-run-tests-batch-and-exit
+;;
+;; Tests use a fixture vault under scripts/test-fixtures/vault and write
+;; output into throw-away firehose repo skeletons under /tmp.
+
+;;; Code:
+
+(require 'ert)
+(require 'roam-export-blog)
+
+(defconst reb-test-dir
+  (directory-file-name (file-name-directory (or load-file-name default-directory))))
+
+(defconst reb-test-repo-root (expand-file-name ".." reb-test-dir))
+
+(defconst reb-test-vault (expand-file-name "test-fixtures/vault" reb-test-dir))
+
+(defun reb-test--file (name)
+  "Path to fixture file NAME in the test vault."
+  (expand-file-name name reb-test-vault))
+
+(defun reb-test--new-root ()
+  "Create a throw-away firehose repo skeleton and return its root."
+  (let ((root (make-temp-file "/tmp/reb-root-" t)))
+    (make-directory (expand-file-name "app/priv/blog/engineering" root) t)
+    (make-directory (expand-file-name "app/priv/static/images/blog" root) t)
+    root))
+
+(defun reb-test--setup-org-id ()
+  "Point org-id at a writable temp locations file and index the fixture vault."
+  (setq org-id-locations-file (make-temp-file "/tmp/reb-orgid-"))
+  (setq org-id-locations nil)
+  (org-id-update-id-locations
+   (mapcar #'reb-test--file '("note.org" "jev.org" "laya.org" "notitle.org")) t))
+
+(defmacro reb-test--with-export (root &rest body)
+  "Run BODY with a fresh repo ROOT and a pinned export date."
+  (declare (indent 1))
+  `(progn
+     (reb-test--setup-org-id)
+     (let ((roam-export-blog-firehose-root ,root)
+           (roam-export-blog--current-date '("2026" "10" "08")))
+       ,@body)))
+
+;;; Pure helpers
+
+(ert-deftest roam-export-blog/slug ()
+  (should (equal "will-it-blend" (roam-export-blog--slug "Will It Blend")))
+  (should (equal "improve-diagnostic-in-the-tdd-cycle"
+                 (roam-export-blog--slug "Improve Diagnostic in the TDD cycle")))
+  (should (equal "v0-2-0-rss-subscribe-links"
+                 (roam-export-blog--slug "v0.2.0 — RSS Subscribe Links"))))
+
+(ert-deftest roam-export-blog/truncate-description-short ()
+  (should (equal "Short paragraph."
+                 (roam-export-blog--truncate-description "Short paragraph."))))
+
+(ert-deftest roam-export-blog/truncate-description-at-word-boundary ()
+  (let* ((words (make-list 60 "word"))
+         (text (string-join words " "))
+         (result (roam-export-blog--truncate-description text)))
+    (should (<= (length result) (+ roam-export-blog-description-length 1)))
+    (should (string-suffix-p "…" result))
+    (should-not (string-suffix-p " " result))
+    (should (string-prefix-p "word word" result))))
+
+;;; Roam ref resolution
+
+(ert-deftest roam-export-blog/roam-refs ()
+  (reb-test--setup-org-id)
+  (should (equal "https://example.com/jev"
+                 (roam-export-blog--roam-refs (reb-test--file "jev.org"))))
+  (should (null (roam-export-blog--roam-refs (reb-test--file "laya.org")))))
+
+;;; Aborts
+
+(ert-deftest roam-export-blog/no-title-aborts ()
+  (let ((root (reb-test--new-root)))
+    (reb-test--with-export root
+      (should-error (roam-export-blog--export-file (reb-test--file "notitle.org"))
+                    :type 'user-error)
+      ;; Aborting must not have written any posts.
+      (should (null
+               (directory-files-recursively
+                (expand-file-name "app/priv/blog" root) "\\.md$"))))))
+
+(ert-deftest roam-export-blog/filename-collision-aborts ()
+  (let ((root (reb-test--new-root)))
+    (reb-test--with-export root
+      ;; Pre-create the exact target file.
+      (make-directory
+       (expand-file-name "app/priv/blog/engineering/2026" root) t)
+      (write-region "" nil
+                    (expand-file-name
+                     "app/priv/blog/engineering/2026/10-08-will-it-blend.md" root))
+      (should-error (roam-export-blog--export-file (reb-test--file "note.org"))
+                    :type 'user-error)
+      ;; Aborting must not have copied any images (no side effects).
+      (should (null
+               (directory-files-recursively
+                (expand-file-name "app/priv/static/images/blog" root)
+                "."))))))
+
+;;; Full export
+
+(ert-deftest roam-export-blog/end-to-end ()
+  (let ((root (reb-test--new-root))
+        result path body)
+    (reb-test--with-export root
+      (setq result (roam-export-blog--export-file (reb-test--file "note.org"))))
+    (setq path (car result))
+    ;; Written at the agreed path.
+    (should (equal (expand-file-name
+                    "app/priv/blog/engineering/2026/10-08-will-it-blend.md" root)
+                   path))
+    (should (file-exists-p path))
+    ;; Image attachment copied into static images with unchanged content.
+    (let ((image (expand-file-name "app/priv/static/images/blog/2026/will-it-blend.svg" root)))
+      (should (file-exists-p image))
+      (should (equal (with-temp-buffer (insert-file-contents image) (buffer-string))
+                     (with-temp-buffer
+                       (insert-file-contents (reb-test--file ".attach/00/000000-0000-0000-0000-000000000001/will-it-blend.svg"))
+                       (buffer-string)))))
+    (setq body (with-temp-buffer (insert-file-contents path) (buffer-string)))
+    ;; Frontmatter.
+    (should (string-match-p "title: \"Will It Blend\"" body))
+    (should (string-match-p "author: \"Willem van den Ende\"" body))
+    (should (string-match-p "tags: ~w()" body))
+    (should (string-match-p
+             "description: \"Will it Blend was a series of videos promoting a blender brand.\""
+             body))
+    (should (string-match-p "image: \"/images/blog/2026/will-it-blend.svg\"" body))
+    (should (string-match-p "published: false" body))
+    ;; Markdown body.
+    (should (string-match-p "Will it Blend was a series of videos promoting a blender brand." body))
+    (should (string-match-p
+             (regexp-quote "![will-it-blend](/images/blog/2026/will-it-blend.svg)")
+             body))
+    (should (string-match-p (regexp-quote "[Jev](https://example.com/jev)") body))
+    (should (string-match-p "Laya popped up" body))
+    (should (string-match-p "a missing note vanished" body))
+    (should (string-match-p "TODO source needed (LinkedIn)" body))
+    (should (string-match-p "^## I learnt this from Julia$" body))
+    (should (string-match-p "^> A quoted comment.$" body))
+    (should (string-match-p "^```elixir$" body))
+    (should (string-match-p (regexp-quote "**bold**") body))
+    ;; Org syntax must not leak into the markdown.
+    (should-not (string-match-p "#\\+begin" body))
+    (should-not (string-match-p "attachment:" body))
+    (should-not (string-match-p "id:0000" body))
+    (should-not (string-match-p "A private comment that must not be exported" body))
+    ;; Warnings: dangling ref, ref without ROAM_REFS, ignored non-image
+    ;; attachment.
+    (should (= 3 (length (cdr result))))
+    (should (cl-some (lambda (w) (string-match-p "00000000-0000-0000-0000-000000009999" w))
+                     (cdr result)))
+    (should (cl-some (lambda (w) (string-match-p "00000000-0000-0000-0000-000000000003" w))
+                     (cdr result)))
+    (should (cl-some (lambda (w) (string-match-p "attached-notes.txt" w))
+                     (cdr result)))))
+
+(ert-deftest roam-export-blog/description-truncated-in-frontmatter ()
+  (let* ((root (reb-test--new-root))
+         (vault (make-temp-file "/tmp/reb-vault-" t))
+         (note (expand-file-name "longpar.org" vault))
+         (long-text (string-join (make-list 50 "lorem" ) " ")))
+    (with-temp-file note
+      (insert ":PROPERTIES:\n:ID:       00000000-0000-0000-0000-000000000005\n:END:\n"
+              "#+title: Long Paragraph\n\n" long-text "\n"))
+    (reb-test--with-export root
+      (let ((result (roam-export-blog--export-file note)))
+        (let ((body (with-temp-buffer
+                      (insert-file-contents (car result))
+                      (buffer-string))))
+          (string-match "description: \"\\([^\"]*\\)\"" body)
+          (let ((desc (match-string 1 body)))
+            (should (<= (length desc) (+ roam-export-blog-description-length 1)))
+            (should (string-suffix-p "…" desc))
+            (should (string-prefix-p "lorem lorem" desc))))))))
+
+(provide 'roam-export-blog-test)
+;;; roam-export-blog-test.el ends here

scripts/roam-export-blog.el

@@ -0,0 +1,453 @@
+;;; roam-export-blog.el --- Export an org-roam note as a firehose blog post -*- lexical-binding: t; -*-
+
+;;; Commentary:
+
+;; M-x roam-export-blog, run from an org-roam note, converts the note to
+;; markdown and writes it directly into the firehose repo as a draft post:
+;;
+;;   <repo>/app/priv/blog/engineering/<YYYY>/<MM>-<DD>-<slug>.md
+;;
+;; with `published: false' frontmatter, so the repo's git diff acts as the
+;; review mechanism.
+;;
+;; What happens during export:
+;;
+;; - `[[id:<uuid>][text]]' roam refs are resolved via org-id.  When the
+;;   target note carries a :ROAM_REFS: property, the link becomes a
+;;   markdown link to the first URL; otherwise it degrades to plain text.
+;; - `[[attachment:...]]' links are resolved via the org-attach ID scheme
+;;   (.attach/<xx>/<rest-of-id>/<file>).  Images are copied into
+;;   app/priv/static/images/blog/<YYYY>/ and referenced with the
+;;   /images/blog/... web path.  Non-image attachments are ignored.
+;; - Org syntax is converted to markdown with a derived ox-md backend
+;;   (fenced code blocks with language, H2 top-level headings, no TOC).
+;; - Dropped refs, ignored attachments and unhandled constructs are
+;;   reported as warnings.
+
+;;; Code:
+
+(require 'org)
+(require 'ox-md)
+(require 'org-id)
+(require 'cl-lib)
+
+(defgroup roam-export-blog nil
+  "Export org-roam notes as firehose blog posts."
+  :group 'org)
+
+(defcustom roam-export-blog-firehose-root "/Users/willem/dev/elixir/firehose"
+  "Path to the firehose repository root."
+  :type 'directory)
+
+(defcustom roam-export-blog-author "Willem van den Ende"
+  "Author name written into generated frontmatter."
+  :type 'string)
+
+(defcustom roam-export-blog-description-length 200
+  "Maximum length of the generated description (before the ellipsis)."
+  :type 'integer)
+
+(defcustom roam-export-blog-image-extensions
+  '("svg" "png" "jpg" "jpeg" "gif" "webp" "avif")
+  "Attachment extensions that count as images."
+  :type '(repeat string))
+
+(defvar roam-export-blog--current-date nil
+  "Override for the export date during tests, as a list (YEAR MONTH DAY).")
+
+;;; Derived markdown backend
+
+(defun roam-export-blog-md-src-block (src-block _contents info)
+  "Transcode SRC-BLOCK into a fenced markdown code block with language."
+  (let ((lang (org-element-property :language src-block))
+        (value (org-export-format-code-default src-block info)))
+    (concat "```" (or lang "") "\n" value "```")))
+
+(defun roam-export-blog-md-link (link desc info)
+  "Transcode LINK; file links to images become markdown images.
+
+Everything else is delegated to `org-md-link'."
+  (let* ((type (org-element-property :type link))
+         (path (org-element-property :path link)))
+    (if (and (equal type "file") (roam-export-blog--image-p path))
+        (format "![%s](%s)"
+                (or (and desc (string-trim (substring-no-properties desc)))
+                    (file-name-base path))
+                path)
+      (org-md-link link desc info))))
+
+(org-export-define-derived-backend 'firehose-md 'md
+  :translate-alist '((src-block . roam-export-blog-md-src-block)
+                     (link . roam-export-blog-md-link)))
+
+(defconst roam-export-blog--export-options
+  '(:with-toc nil :section-numbers nil :md-toplevel-hlevel 2))
+
+;;; Small helpers
+
+(defun roam-export-blog--slug (title)
+  "Derive a filename slug from TITLE."
+  (let* ((lower (downcase title))
+         (slugged (replace-regexp-in-string "[^a-z0-9]+" "-" lower)))
+    (replace-regexp-in-string "\\`-+\\|-+\\'" "" slugged)))
+
+(defun roam-export-blog--date-parts ()
+  "Export date as a list of strings (YEAR MONTH DAY)."
+  (or roam-export-blog--current-date
+      (list (format-time-string "%Y")
+            (format-time-string "%m")
+            (format-time-string "%d"))))
+
+(defun roam-export-blog--escape-elixir-string (text)
+  "Escape TEXT for embedding in an Elixir double-quoted string."
+  (replace-regexp-in-string
+   "\"" "\\\\\""
+   (replace-regexp-in-string "\\\\" "\\\\\\\\" text)))
+
+(defun roam-export-blog--truncate-description (text)
+  "Truncate TEXT to about `roam-export-blog-description-length' characters."
+  (let ((max roam-export-blog-description-length))
+    (if (<= (length text) max)
+        text
+      (let ((cut (cl-position ?\s (substring text 0 max) :from-end t)))
+        (concat (if cut (substring text 0 cut) (substring text 0 max))
+                "…")))))
+
+(defun roam-export-blog--plain-text (element)
+  "Return a plain-text approximation of org ELEMENT."
+  (cond
+   ((stringp element) element)
+   ((memq (org-element-type element) '(code verbatim inline-src-block))
+    (or (org-element-property :value element) ""))
+   ((eq (org-element-type element) 'entity)
+    (or (org-element-property :utf8 element) ""))
+   (t (mapconcat #'roam-export-blog--plain-text (org-element-contents element) ""))))
+
+;;; Reading the note
+
+(defun roam-export-blog--title (buffer)
+  "Return the #+TITLE: keyword value in BUFFER, or nil."
+  (with-current-buffer buffer
+    (cadr (assoc "TITLE" (org-collect-keywords '("TITLE"))))))
+
+(defun roam-export-blog--first-paragraph-text (buffer)
+  "Return the plain text of the first paragraph in BUFFER."
+  (with-current-buffer buffer
+    (let ((para (org-element-map (org-element-parse-buffer) 'paragraph
+                  #'identity nil t)))
+      (when para
+        (replace-regexp-in-string
+         "[ \t\n]+" " "
+         (string-trim
+          (substring-no-properties (roam-export-blog--plain-text para))))))))
+
+(defun roam-export-blog--roam-refs (file)
+  "Return the first :ROAM_REFS: URL of the note in FILE, or nil."
+  (with-current-buffer (find-file-noselect file)
+    (org-with-wide-buffer
+     (goto-char (point-min))
+     (let ((value (org-entry-get (point) "ROAM_REFS")))
+       (when value (car (split-string value "[ \t]+")))))))
+
+(defun roam-export-blog--note-title (file)
+  "Return the #+TITLE: of the note in FILE, or nil."
+  (roam-export-blog--title (find-file-noselect file)))
+
+;;; Link processing
+
+(defun roam-export-blog--vault-attach-dir (file)
+  "Return the .attach directory dominating FILE, or nil."
+  (when-let* ((root (locate-dominating-file file ".attach")))
+    (expand-file-name ".attach" root)))
+
+(defun roam-export-blog--image-p (file)
+  "Return non-nil when FILE looks like an image attachment."
+  (member (downcase (file-name-extension file))
+          roam-export-blog-image-extensions))
+
+(defun roam-export-blog--link-description (link)
+  "Return the description text of LINK, or nil."
+  (let ((begin (org-element-property :contents-begin link))
+        (end (org-element-property :contents-end link)))
+    (when (and begin end)
+      (buffer-substring-no-properties begin end))))
+
+(defun roam-export-blog--desc-or (desc fallback)
+  "Return trimmed DESC, or FALLBACK when DESC is nil or empty.
+
+An empty string is truthy in Elisp, so descriptions must be
+treated as absent explicitly."
+  (let ((trimmed (when desc (string-trim desc))))
+    (if (and trimmed (not (string-empty-p trimmed)))
+        trimmed
+      fallback)))
+
+(defun roam-export-blog--desc-verbatim-or (desc fallback)
+  "Return DESC unchanged, or FALLBACK when DESC is nil or blank.
+
+Used for plain-text replacements: a description like \"Jev \"
+may carry the spacing that separated it from surrounding text in
+the org source."
+  (if (and desc (not (string-empty-p (string-trim desc))))
+      desc
+    fallback))
+
+(defun roam-export-blog--attachment-path (link vault-attach-dir note-id)
+  "Return the absolute source path of attachment LINK, or nil.
+
+Handles three shapes: file links already normalized by org to an
+absolute path under the vault's .attach directory, plain
+attachment: links and fuzzy links carrying an attachment: prefix.
+Resolution follows the org-attach ID scheme:
+.attach/<first two ID chars>/<rest of ID>/<path>."
+  (let* ((type (org-element-property :type link))
+         (path (org-element-property :path link))
+         (bare (if (and (equal type "fuzzy")
+                        (string-prefix-p "attachment:" path))
+                   (substring path (length "attachment:"))
+                 path)))
+    (cond
+     ((and (equal type "file") (file-name-absolute-p path)
+           vault-attach-dir
+           (string-prefix-p vault-attach-dir (expand-file-name path)))
+      (expand-file-name path))
+     ((and vault-attach-dir note-id bare
+           (>= (length note-id) 2))
+      (let ((candidate (expand-file-name
+                        (concat (substring note-id 0 2)
+                                "/" (substring note-id 2)
+                                "/" bare)
+                        vault-attach-dir)))
+        (when (file-exists-p candidate) candidate)))
+     (t nil))))
+
+(defun roam-export-blog--resolve-id (id)
+  "Return the file containing org ID, or nil."
+  (ignore-errors (org-id-find id)))
+
+(defun roam-export-blog--link-replacement (link vault-attach-dir note-id)
+  "Compute the replacement for LINK.
+
+Return (REPLACEMENT WARNINGS IMAGES), where REPLACEMENT is org
+syntax to substitute for the link (nil leaves the link alone),
+WARNINGS is a list of warning strings and IMAGES is a list of
+(SOURCE . DEST) file copies to perform."
+  (let* ((type (org-element-property :type link))
+         (path (org-element-property :path link))
+         (desc (roam-export-blog--link-description link))
+         (replacement nil)
+         (warnings nil)
+         (images nil))
+    (cond
+     ;; Roam refs: [[id:uuid][text]]
+     ((equal type "id")
+      (let* ((target (roam-export-blog--resolve-id path))
+             (refs (when target (roam-export-blog--roam-refs (car target)))))        (cond
+         ((and target refs)
+          (setq replacement (format "[[%s][%s]]"
+                                    refs (roam-export-blog--desc-or desc refs))))
+         (target
+          (setq replacement (roam-export-blog--desc-verbatim-or
+                             desc (or (roam-export-blog--note-title (car target))
+                                      "")))
+          (push (format "dropped ref: id %s has no ROAM_REFS, kept plain text %S"
+                        path replacement)
+                warnings))
+         (t
+          (setq replacement (roam-export-blog--desc-verbatim-or desc ""))
+          (push (format "dropped ref: unresolved id %s, kept plain text %S"
+                        path replacement)
+                warnings)))))
+     ;; Attachments (and file links that org normalized from attachments)
+     ((and vault-attach-dir
+           (or (member type '("file" "attachment"))
+               (and (equal type "fuzzy")
+                    (string-prefix-p "attachment:" path))))
+      (let ((source (roam-export-blog--attachment-path link vault-attach-dir note-id)))
+        (cond
+         ((and source (file-exists-p source) (roam-export-blog--image-p source))
+          (let* ((name (file-name-nondirectory source))
+                 (year (car (roam-export-blog--date-parts)))
+                 (web-path (format "/images/blog/%s/%s" year name))
+                 (dest (expand-file-name
+                        (format "app/priv/static/images/blog/%s/%s" year name)
+                        roam-export-blog-firehose-root)))
+            (setq images (list (cons source dest)))
+            (setq replacement
+                  (format "[[file:%s][%s]]" web-path
+                          (roam-export-blog--desc-or desc
+                                                     (file-name-base name))))))
+         ((and source (file-exists-p source))
+          (setq replacement (roam-export-blog--desc-verbatim-or desc ""))
+          (push (format "ignored attachment (not an image): %s"
+                        (file-name-nondirectory source))
+                warnings))
+         (t
+          (setq replacement (roam-export-blog--desc-verbatim-or desc ""))
+          (push (format "unhandled link dropped: %s:%s" type path)
+                warnings)))))
+     ;; Any other file: link points into the vault, not the blog.
+     ((equal type "file")
+      (setq replacement (roam-export-blog--desc-verbatim-or desc ""))
+      (push (format "unhandled link dropped: file:%s" path) warnings))
+     ;; Everything else (https, mailto, ...) passes through untouched.
+     (t nil))
+    (list replacement warnings images)))
+
+(defun roam-export-blog--process-links (buffer vault-attach-dir)
+  "Rewrite id/attachment/file links in BUFFER's text.
+
+BUFFER is not modified; a processed copy of its text is returned.
+Return (TEXT WARNINGS IMAGES) where IMAGES is an alist of
+(SOURCE . DEST) image copies to perform."
+  (with-current-buffer buffer
+    (let ((text (buffer-string))
+          (note-id (org-entry-get (point-min) "ID"))
+          (warnings nil)
+          (all-images nil))
+      (let* ((tree (org-element-parse-buffer))
+             (replacements
+              (reverse
+               (org-element-map tree 'link
+                 (lambda (link)
+                   (let* ((result (roam-export-blog--link-replacement
+                                   link vault-attach-dir note-id))
+                          (replacement (nth 0 result))
+                          (warns (nth 1 result))
+                          (images (nth 2 result)))
+                     (setq warnings (append warnings warns)
+                           all-images (append all-images images))
+                     (when replacement
+                       (list (org-element-property :begin link)
+                             ;; :end includes :post-blank (trailing
+                             ;; whitespace); exclude it from the
+                             ;; replaced region.
+                             (- (org-element-property :end link)
+                                (or (org-element-property :post-blank link) 0))
+                             replacement))))
+                 nil nil nil))))
+        (dolist (r replacements)
+          (let ((begin (nth 0 r))
+                (end (nth 1 r))
+                (replacement (nth 2 r)))
+            (setq text (concat (substring text 0 (1- begin))
+                               replacement
+                               (substring text (1- end))))))
+        (list text warnings all-images)))))
+
+;;; Markdown generation
+
+(defun roam-export-blog--to-markdown (text)
+  "Export org TEXT to markdown with the firehose-md backend."
+  (with-temp-buffer
+    (insert text)
+    (org-mode)
+    (let ((out (org-export-to-buffer
+                   'firehose-md "*roam-export-blog export*"
+                 nil nil nil nil roam-export-blog--export-options)))
+      (with-current-buffer out (buffer-string)))))
+
+(defun roam-export-blog--cleanup (markdown)
+  "Collapse runs of blank lines in MARKDOWN."
+  (replace-regexp-in-string "\n\\(?:[ \t]*\n\\)+\\'" "\n"
+                            (replace-regexp-in-string "\n\\{3,\\}" "\n\n" markdown)))
+
+;;; Frontmatter and writing
+
+(defun roam-export-blog--frontmatter (title description image)
+  "Build the Elixir-term frontmatter for the post."
+  (concat "%{\n"
+          (format "  title: %S,\n" (roam-export-blog--escape-elixir-string title))
+          (format "  author: %S,\n" roam-export-blog-author)
+          "  tags: ~w(),\n"
+          (format "  description: %S,\n"
+                  (roam-export-blog--escape-elixir-string description))
+          (format "  image: %S,\n" image)
+          "  published: false\n"
+          "}\n---\n"))
+
+(defun roam-export-blog--post-path (slug)
+  "Return the target post path for SLUG."
+  (let ((year (car (roam-export-blog--date-parts)))
+        (month (nth 1 (roam-export-blog--date-parts)))
+        (day (nth 2 (roam-export-blog--date-parts))))
+    (expand-file-name
+     (format "app/priv/blog/engineering/%s/%s-%s-%s.md" year month day slug)
+     roam-export-blog-firehose-root)))
+
+(defun roam-export-blog--copy-images (images)
+  "Copy IMAGES (alist of SOURCE . DEST), warning on basename clashes."
+  (let ((copied nil)
+        (warnings nil))
+    (dolist (pair images)
+      (let ((source (car pair))
+            (dest (cdr pair)))
+        (cond
+         ((member dest copied)
+          (push (format "skipped duplicate image copy: %s"
+                        (file-name-nondirectory source))
+                warnings))
+         (t
+          (make-directory (file-name-directory dest) t)
+          (copy-file source dest t)
+          (push dest copied)))))
+    (nreverse warnings)))
+
+;;; The command
+
+(defun roam-export-blog--export-file (&optional file)
+  "Export org-roam note FILE to a firehose blog post.
+
+Return (OUTPUT-PATH . WARNINGS).  Abort with `user-error' when the
+note has no title or the target file already exists."
+  (setq file (or file (buffer-file-name)))
+  (unless file
+    (user-error "roam-export-blog: not visiting a file"))
+  (let* ((buffer (find-file-noselect file))
+         (title (roam-export-blog--title buffer)))
+    (unless title
+      (user-error "roam-export-blog: %s has no #+title: keyword, aborting" file))
+    (let* ((slug (roam-export-blog--slug title))
+           (post-path (roam-export-blog--post-path slug)))
+      (when (file-exists-p post-path)
+        (user-error "roam-export-blog: %s already exists, aborting" post-path))
+      (let* ((processed (roam-export-blog--process-links
+                         buffer (roam-export-blog--vault-attach-dir file)))
+             (text (nth 0 processed))
+             (link-warnings (nth 1 processed))
+             (images (nth 2 processed))
+             (copy-warnings (roam-export-blog--copy-images images))
+             (warnings (append (nreverse link-warnings) copy-warnings))
+             (image (when images
+                      (let ((static (expand-file-name
+                                     "app/priv/static"
+                                     roam-export-blog-firehose-root)))
+                        (string-remove-prefix static (cdr (car images))))))
+             (description (roam-export-blog--truncate-description
+                           (roam-export-blog--first-paragraph-text buffer)))
+             (markdown (roam-export-blog--cleanup (roam-export-blog--to-markdown text))))
+        (make-directory (file-name-directory post-path) t)
+        (with-temp-file post-path
+          (insert (roam-export-blog--frontmatter title description image)
+                  markdown))
+        (cons post-path warnings)))))
+
+;;;###autoload
+(defun roam-export-blog ()
+  "Export the current org-roam note as a firehose blog post."
+  (interactive)
+  (let ((result (roam-export-blog--export-file (buffer-file-name))))
+    (let ((path (car result))
+          (warnings (cdr result)))
+      (message "roam-export-blog: wrote %s%s" path
+               (if warnings
+                   (format " (%d warning%s)" (length warnings)
+                           (if (= 1 (length warnings)) "" "s"))
+                 ""))
+      (when warnings
+        (with-output-to-temp-buffer "*roam-export-blog warnings*"
+          (dolist (w warnings)
+            (princ (format "%s\n" w))))))))
+
+(provide 'roam-export-blog)
+;;; roam-export-blog.el ends here

scripts/test-fixtures/vault/.attach/00/000000-0000-0000-0000-000000000001/attached-notes.txt

@@ -0,0 +1 @@
+some attached notes

scripts/test-fixtures/vault/.attach/00/000000-0000-0000-0000-000000000001/will-it-blend.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="10" height="10"><rect width="10" height="10"/></svg>

scripts/test-fixtures/vault/jev.org

@@ -0,0 +1,7 @@
+:PROPERTIES:
+:ID:       00000000-0000-0000-0000-000000000002
+:ROAM_REFS: https://example.com/jev
+:END:
+#+title: Jev
+
+Body of Jev.

scripts/test-fixtures/vault/laya.org

@@ -0,0 +1,6 @@
+:PROPERTIES:
+:ID:       00000000-0000-0000-0000-000000000003
+:END:
+#+title: Laya
+
+Body of Laya.

scripts/test-fixtures/vault/note.org

@@ -0,0 +1,26 @@
+:PROPERTIES:
+:ID:       00000000-0000-0000-0000-000000000001
+:END:
+#+title: Will It Blend
+
+Will it Blend was a series of videos promoting a blender brand.
+
+# A private comment that must not be exported.
+
+[[attachment:will-it-blend.svg]]
+
+For instance, a day after [[id:00000000-0000-0000-0000-000000000002][Jev]] came out, [[id:00000000-0000-0000-0000-000000000003][Laya]] popped up, and [[id:00000000-0000-0000-0000-000000009999][a missing note]] vanished. TODO source needed (LinkedIn)
+
+[[attachment:attached-notes.txt]]
+
+* I learnt this from Julia
+
+Body text with *bold*.
+
+#+begin_quote
+A quoted comment.
+#+end_quote
+
+#+begin_src elixir
+IO.puts("hi")
+#+end_src

scripts/test-fixtures/vault/notitle.org

@@ -0,0 +1,5 @@
+:PROPERTIES:
+:ID:       00000000-0000-0000-0000-000000000004
+:END:
+
+No title here.