diff --git a/.goreleaser.yaml b/.goreleaser.yaml
index af29cfe..c8376f1 100644
--- a/.goreleaser.yaml
+++ b/.goreleaser.yaml
@@ -2,7 +2,7 @@ version: 2
 
 before:
   hooks:
-    - just manpage
+    - just manpage {{ .Version }}
 
 builds:
   - id: mdview
diff --git a/CLAUDE.md b/CLAUDE.md
index da5e9ac..1c10d43 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -10,7 +10,7 @@ default browser. It's essentially one file, `main.go`, plus a handful of embedde
 
 ## Build & run
 
-Requires Go (see `go.mod`/`mise.toml` for version) and, for packaging, `just`, `pandoc`, and
+Requires Go (see `go.mod` for the version) and, for packaging, `just`, `pandoc`, and
 [`goreleaser`](https://goreleaser.com/).
 
 - Quick local build: `go build` (produces `./mdview`)
@@ -23,7 +23,7 @@ Requires Go (see `go.mod`/`mise.toml` for version) and, for packaging, `just`, `
   - `just check` — validates `.goreleaser.yaml`
   - `just snap` — build snap package via `snapcraft` (kept separate; goreleaser doesn't build snaps)
   - `just clean` — remove build artifacts (`dist/`, `mdview.1`, `*.snap`)
-  - `just manpage` regenerates `mdview.1` from `mdview.1.md` via pandoc; goreleaser runs this automatically as a `before.hooks` step.
+  - `just manpage [version]` regenerates `mdview.1` from `mdview.1.md` via pandoc, replacing the `@VERSION@` placeholder in the man page header with `version` (default: `git describe --tags --always`). goreleaser runs this automatically as a `before.hooks` step and passes `{{ .Version }}`. Never write a literal app version in a source or packaging file; use a placeholder that the build replaces.
   - Versioning is read directly from git tags by goreleaser (embedded via `-ldflags -X main.appVersion={{.Version}}`) — there's no `VERSION` env var to pass anymore.
 - Run tests with `go test ./...`. There is no lint target configured; `go vet ./...` and `gofmt` are reasonable sanity checks before committing.
 
@@ -47,6 +47,13 @@ Everything happens in `main()` in `main.go`, in a straight-line pipeline:
 
 Output location resolution order: `MDVIEW_DIR` env var → (if running as a Snap, per `SNAP_USER_COMMON` env var) `~/mdview-temp` → OS default temp dir. `MDVIEW_DIR` and `~/mdview-temp` are created with `MkdirAll`. Before writing a temp file, `removeStaleTempFiles` deletes generated `mdview<32 hex>.html` files older than 24 hours from that directory (the browser reads the new file after mdview exits, so mdview cannot delete it right away). This exists because Snap-sandboxed browsers (e.g. Snap Firefox) can't read from `/tmp`, only from the user's home directory — `check()` writes errors to stderr, names the failing path, and prints a Snap-specific hint for permission and not-found errors for this reason.
 
+### Vendored `mermaid.min.js`
+
+`mermaid.min.js` is a vendored copy of the Mermaid library, embedded with `//go:embed`. Print its
+version with `grep -o 'version:"[0-9.]*"' mermaid.min.js`. To update it, download
+`https://cdn.jsdelivr.net/npm/mermaid@<version>/dist/mermaid.min.js` over the file, render a markdown
+file with a mermaid block (light and dark mode), and commit the new file.
+
 ### Packaging
 
 `.goreleaser.yaml` drives cross-platform binary builds, archives (`.tar.gz`/`.zip`), and `.deb`/
diff --git a/justfile b/justfile
index 506033f..8ea0f18 100644
--- a/justfile
+++ b/justfile
@@ -24,5 +24,6 @@ clean:
 
 	# snapcraft clean mdview -s pull
 
-manpage:
-	pandoc --standalone --to man mdview.1.md -o mdview.1
\ No newline at end of file
+# The version defaults to the latest git tag; goreleaser passes its own.
+manpage version=`git describe --tags --always`:
+	sed 's|@VERSION@|{{version}}|g' mdview.1.md | pandoc --standalone --to man -o mdview.1
diff --git a/mdview.1.md b/mdview.1.md
index 67d3f43..93fc816 100644
--- a/mdview.1.md
+++ b/mdview.1.md
@@ -1,4 +1,4 @@
-% MDVIEW(1) Version 1.4.0 | "Markdown View" Documentation
+% MDVIEW(1) Version @VERSION@ | "Markdown View" Documentation
 
 # NAME
 
@@ -6,21 +6,27 @@
 
 # SYNOPSIS
 
-**mdview** _filename_  
-**mdview** **-**  
-**mdview** \[**-h**|**--help**|**-v**|**--version**]
+**mdview** \[**-b**] \[**-o** _output_] _filename_  
+**mdview** \[**-b**] \[**-o** _output_] **-**  
+**mdview** **-h**|**-help**|**-v**|**-version**
 
 # DESCRIPTION
 
 Formats a markdown file as HTML, writes it to a temporary file and
 then launches that file in the default web browser. By default, it will
 use the operating system's default temporary directory unless the
-environment variable MDVIEW_DIR is set.
+environment variable MDVIEW_DIR is set. Generated temporary files that
+are more than 24 hours old are removed from that directory the next
+time mdview writes one.
 
 If _filename_ is a single dash (**-**), the markdown is read from
 standard input. Relative image paths are then resolved against the
 current working directory.
 
+Options can be given before or after _filename_, with one or two
+leading dashes (for example **-help** or **--help**). Use **--** to end
+the options.
+
 ## Options
 
 **-b**, **-bare**
@@ -31,7 +37,7 @@ Bare HTML with no style applied.
 
 Prints mdview help message.
 
-**-o** _filename_
+**-o** _output_
 
 Output filename. (Optional)