diff --git a/lib/deno.json b/lib/deno.json
index 4279c56053e6fc0b149e21827b0d27d0282382ba..35caa360c6cc3f625900892cf06782641dcf1fdb 100644
--- a/lib/deno.json
+++ b/lib/deno.json
@@ -1,15 +1,15 @@
 {
   "name": "@clo/lib",
   "description": "high quality typescript libraries",
-  "version": "5.0.0",
+  "version": "7.0.0",
   "license": "MIT",
   "exports": {
     "./arrays": "./arrays.ts",
     "./assert": "./assert.ts",
     "./async": "./async.ts",
     "./bytes": "./bytes.ts",
-    "./error": "./error.ts",
     "./Events": "./Events.ts",
+    "./exception": "./exception.ts",
     "./http": "./http.ts",
     "./log": "./log.ts",
     "./log/stack": "./log/stack.ts",
diff --git a/lib/meta.test.ts b/lib/meta.test.ts
index 75f753c7fe1c88c067cd9a6fe9212cdb45c4c90f..063d12c4fcc37998a23320b2f759d68b3dd552aa 100644
--- a/lib/meta.test.ts
+++ b/lib/meta.test.ts
@@ -16,6 +16,16 @@ describe("title", () => {
     const out = meta.toHtml(T, { title: "<b>Hi</b>" });
     assert.ok(out.startsWith("<title>&lt;b&gt;Hi&lt;/b&gt;</title>"));
   });
+
+  test("omitted title emits no title entry", () => {
+    const tags = meta.toTags(T, { canonical: "/page" });
+    assert.ok(!tags.meta.some((m) => "title" in m));
+  });
+
+  test("toHtml without title emits no <title>", () => {
+    const out = meta.toHtml(T, { description: "hi" });
+    assert.ok(!out.includes("<title>"));
+  });
 });
 
 describe("basic meta fields", () => {
@@ -69,10 +79,15 @@ describe("basic meta fields", () => {
     assert.ok(tags.meta.some((m) => m.name === "robots" && m.content === "noindex,nofollow"));
   });
 
-  test("denyRobots: false on meta does not override template true", () => {
-    // null/undefined opts out; false is falsy so it also doesn't block
+  test("denyRobots: false on meta overrides template true", () => {
+    // explicit false unsets the template; only undefined inherits.
     const tags = meta.toTags({ ...T, denyRobots: true }, { title: "T", denyRobots: false });
-    assert.ok(tags.meta.some((m) => m.name === "robots"));
+    assert.ok(!tags.meta.some((m) => m.name === "robots"));
+  });
+
+  test("denyRobots: null on meta unsets template true", () => {
+    const tags = meta.toTags({ ...T, denyRobots: true }, { title: "T", denyRobots: null });
+    assert.ok(!tags.meta.some((m) => m.name === "robots"));
   });
 
   test("viewport defaults to mobile-friendly value", () => {
@@ -88,6 +103,19 @@ describe("basic meta fields", () => {
     const tags = meta.toTags(T, { title: "T", viewport: "width=device-width" });
     assert.ok(tags.meta.some((m) => m.name === "viewport" && m.content === "width=device-width"));
   });
+
+  test("viewport: null omits the default tag", () => {
+    const tags = meta.toTags(T, { title: "T", viewport: null });
+    assert.ok(!tags.meta.some((m) => m.name === "viewport"));
+  });
+
+  test("null unsets a template field; undefined inherits it", () => {
+    const template: meta.Template = { base, publisher: "Acme" };
+    const unset = meta.toTags(template, { title: "T", publisher: null });
+    assert.ok(!unset.meta.some((m) => m.name === "publisher"));
+    const inherited = meta.toTags(template, { title: "T" });
+    assert.ok(inherited.meta.some((m) => m.name === "publisher" && m.content === "Acme"));
+  });
 });
 
 describe("links", () => {
@@ -173,60 +201,83 @@ describe("embed", () => {
 
   test("thumbnail resolved and applied to both og:image and twitter:image", () => {
     const tags = meta.toTags(T, { title: "T", embed: { thumbnail: "/img.png" } });
-    assert.ok(tags.meta.some((m) => m.name === "og:image" && m.content === "https://example.com/img.png"));
+    assert.ok(tags.meta.some((m) => m.property === "og:image" && m.content === "https://example.com/img.png"));
     assert.ok(tags.meta.some((m) => m.name === "twitter:image" && m.content === "https://example.com/img.png"));
   });
 
+  test("thumbnailAlt emits og:image:alt and twitter:image:alt", () => {
+    const tags = meta.toTags(T, { title: "T", embed: { thumbnail: "/img.png", thumbnailAlt: "a cat" } });
+    assert.ok(tags.meta.some((m) => m.property === "og:image:alt" && m.content === "a cat"));
+    assert.ok(tags.meta.some((m) => m.name === "twitter:image:alt" && m.content === "a cat"));
+  });
+
+  test("thumbnailAlt without thumbnail emits nothing", () => {
+    const tags = meta.toTags(T, { title: "T", embed: { thumbnailAlt: "a cat" } });
+    assert.ok(!tags.meta.some((m) => m.content === "a cat"));
+  });
+
   test("embed title falls back to page title for og", () => {
     const tags = meta.toTags(T, { title: "My Page", embed: {} });
-    assert.ok(tags.meta.some((m) => m.name === "og:title" && m.content === "My Page"));
+    assert.ok(tags.meta.some((m) => m.property === "og:title" && m.content === "My Page"));
   });
 
   test("embed title overrides page title for og", () => {
     const tags = meta.toTags(T, { title: "My Page", embed: { title: "Share Title" } });
-    assert.ok(tags.meta.some((m) => m.name === "og:title" && m.content === "Share Title"));
+    assert.ok(tags.meta.some((m) => m.property === "og:title" && m.content === "Share Title"));
   });
 
   test("embed description falls back to page description", () => {
     const tags = meta.toTags(T, { title: "T", description: "page desc", embed: {} });
-    assert.ok(tags.meta.some((m) => m.name === "og:description" && m.content === "page desc"));
+    assert.ok(tags.meta.some((m) => m.property === "og:description" && m.content === "page desc"));
   });
 
   test("siteTitle sets og:site_name", () => {
     const tags = meta.toTags(T, { title: "T", embed: { siteTitle: "My Site" } });
-    assert.ok(tags.meta.some((m) => m.name === "og:site_name" && m.content === "My Site"));
+    assert.ok(tags.meta.some((m) => m.property === "og:site_name" && m.content === "My Site"));
   });
 
   test("canonical sets og:url when embed active", () => {
     const tags = meta.toTags(T, { title: "T", canonical: "/page", embed: {} });
-    assert.ok(tags.meta.some((m) => m.name === "og:url" && m.content === "https://example.com/page"));
+    assert.ok(tags.meta.some((m) => m.property === "og:url" && m.content === "https://example.com/page"));
   });
 
   test("no canonical → no og:url injected by embed", () => {
     const tags = meta.toTags(T, { title: "T", embed: {} });
-    assert.ok(!tags.meta.some((m) => m.name === "og:url"));
+    assert.ok(!tags.meta.some((m) => m.property === "og:url"));
   });
 
   test("explicit openGraph fields override embed defaults", () => {
     const tags = meta.toTags(T, { title: "T", embed: { title: "Embed" }, openGraph: { title: "Explicit" } });
-    assert.ok(tags.meta.some((m) => m.name === "og:title" && m.content === "Explicit"));
-    assert.equal(tags.meta.filter((m) => m.name === "og:title").length, 1);
+    assert.ok(tags.meta.some((m) => m.property === "og:title" && m.content === "Explicit"));
+    assert.equal(tags.meta.filter((m) => m.property === "og:title").length, 1);
   });
 
   test("embed sets og:type = website", () => {
     const tags = meta.toTags(T, { title: "T", embed: {} });
-    assert.ok(tags.meta.some((m) => m.name === "og:type" && m.content === "website"));
+    assert.ok(tags.meta.some((m) => m.property === "og:type" && m.content === "website"));
   });
 });
 
 describe("openGraph nested/array fields", () => {
+  test("og tags use property= and twitter tags use name=", () => {
+    const tags = meta.toTags(T, {
+      title: "T",
+      openGraph: { title: "OG" },
+      twitter: { card: "summary", title: "TW" },
+    });
+    const og = tags.meta.find((m) => m.content === "OG")!;
+    const tw = tags.meta.find((m) => m.content === "TW")!;
+    assert.deepEqual(og, { property: "og:title", content: "OG" });
+    assert.deepEqual(tw, { name: "twitter:title", content: "TW" });
+  });
+
   test("nested object emits namespaced tags", () => {
     const tags = meta.toTags(
       T,
       { title: "T", openGraph: { image: { url: "https://example.com/img.png", width: "800" } } },
     );
-    assert.ok(tags.meta.some((m) => m.name === "og:image:url" && m.content === "https://example.com/img.png"));
-    assert.ok(tags.meta.some((m) => m.name === "og:image:width" && m.content === "800"));
+    assert.ok(tags.meta.some((m) => m.property === "og:image:url" && m.content === "https://example.com/img.png"));
+    assert.ok(tags.meta.some((m) => m.property === "og:image:width" && m.content === "800"));
   });
 
   test("array value emits duplicate tags", () => {
@@ -234,12 +285,12 @@ describe("openGraph nested/array fields", () => {
       T,
       { title: "T", openGraph: { image: ["https://a.com/1.png", "https://a.com/2.png"] } },
     );
-    assert.equal(tags.meta.filter((m) => m.name === "og:image").length, 2);
+    assert.equal(tags.meta.filter((m) => m.property === "og:image").length, 2);
   });
 
   test("null field is skipped", () => {
     const tags = meta.toTags(T, { title: "T", openGraph: { image: null } });
-    assert.ok(!tags.meta.some((m) => m.name === "og:image"));
+    assert.ok(!tags.meta.some((m) => m.property === "og:image"));
   });
 });
 
@@ -382,6 +433,13 @@ describe("extra", () => {
     assert.equal(entry.bogus, undefined);
   });
 
+  test("toHtml renders an extra meta carrying a title attribute as <meta>", () => {
+    const out = meta.toHtml(T, { title: "Page", extra: [{ tag: "meta", name: "x", title: "tip", content: "y" }] });
+    assert.ok(out.includes("<title>Page</title>"));
+    assert.ok(out.includes(`title=tip`) && out.includes(`name=x`));
+    assert.equal(out.match(/<title>/g)?.length, 1);
+  });
+
   test("falls back to template extra", () => {
     const tags = meta.toTags({ ...T, extra: [{ tag: "meta", name: "tmpl", content: "yes" }] }, { title: "T" });
     assert.ok(tags.meta.some((m) => m.name === "tmpl" && m.content === "yes"));
@@ -401,6 +459,7 @@ interface HtmlAttributes {
 }
 interface MetaAttributes extends HtmlAttributes {
   name?: string;
+  property?: string;
   content?: string;
   charSet?: string;
   httpEquiv?: string;
diff --git a/lib/meta.ts b/lib/meta.ts
index 4b76007da717699e9e4beb06c927cb520d054e63..b3eafe92e48cc28768c8388c6ed8450c3f6c90e1 100644
--- a/lib/meta.ts
+++ b/lib/meta.ts
@@ -1,13 +1,14 @@
+/** `null` unsets something, `undefined` falls back to what the template says. */
 export interface Meta {
-  /** required for all pages. `<title>{content}</title>` */
-  title: string;
+  /** recommended for all pages. `<title>{content}</title>` */
+  title?: string | null;
   /** recommended for all pages. `<meta name="description" content="{...}" />` */
   description?: string | null;
   /** automatically added for static renders from the 'pages' folders. */
   canonical?: string | null;
   /** add `<link rel="alternate" ... />`. Object keys are interpretted as
    * mime types if they contain a slash, otherwise seen as an alternative language. */
-  alternates?: Alternate[] | Record<string, string>;
+  alternates?: Alternate[] | Record<string, string> | null;
 
   /** automatically generate both OpenGraph and Twitter meta tags */
   embed?: AutoEmbed | null;
@@ -18,11 +19,11 @@ export interface Meta {
   /** add 'twitter:*' meta tags */
   twitter?: Twitter | null;
   /** refer to an oEmbed file. See https://oembed.com */
-  oEmbed?: string;
+  oEmbed?: string | null;
   /** add arbitrary scripts to the document head */
-  scripts?: Array<{ content: string } | ExternalScript>;
+  scripts?: Array<{ content: string } | ExternalScript> | null;
   /** add arbitrary styles to the document head */
-  styles?: Array<{ content: string } | ExternalStylesheet>;
+  styles?: Array<{ content: string } | ExternalStylesheet> | null;
   /**
    * '@clo/lib/meta' intentionally excludes a lot of exotic tags.
    * Use `{ tag, ...attrs }` to add arbitrary head elements:
@@ -34,14 +35,14 @@ export interface Meta {
    * ],
    * ```
    */
-  extra?: Array<ExtraItem>;
+  extra?: Array<ExtraItem> | null;
 
   /** adds `<meta name="author" content="{...}" />` */
-  authors?: string[];
+  authors?: string[] | null;
   /** credit your framework or toolchain */
   generator?: string | null;
   /** adds `<meta name="keywords" content="{keywords.join(', ')}" />` */
-  keywords?: string[];
+  keywords?: string[] | null;
   /** URL to a manifest; https://developer.mozilla.org/en-US/docs/Web/Manifest */
   manifest?: string | null;
   /** adds `<meta name="publisher" content="{...}" />` */
@@ -51,7 +52,7 @@ export interface Meta {
   /** adds `<meta name="theme-color" content="{...}" />` */
   themeColor?: string | { dark: string; light: string } | null;
   /** defaults to `width=device-width, initial-scale=1` for mobile compatibility. */
-  viewport?: string;
+  viewport?: string | null;
 }
 export interface ExternalStylesheet {
   rel?: "stylesheet";
@@ -77,8 +78,10 @@ export interface AutoEmbed {
   title?: string | null;
   /* defaults to the top level page description. */
   description?: string | null;
-  /* add an image to the embed card. */
+  /* add an image url to the embed card. */
   thumbnail?: string | null;
+  /** describe the embed image. */
+  thumbnailAlt?: string | null;
   /** @default "banner", which applies twitter:card = "summary_large_image" */
   thumbnailSize?: "banner" | "icon" | null;
   /** @default null - no site title */
@@ -158,34 +161,39 @@ export function toTags(template: Template, meta: Meta): Tags {
   const { titleTemplate, base } = template;
   const resolve = (str: string) => new URL(str, base).href;
 
-  const title = titleTemplate ? titleTemplate(meta.title) : meta.title;
+  const title = meta.title == null ? null : titleTemplate ? titleTemplate(meta.title) : meta.title;
   const description = meta.description ?? null;
   const canonical = meta.canonical ? resolve(meta.canonical) : null;
-  const denyRobots = Boolean(meta.denyRobots || template.denyRobots);
-  const authors = meta.authors ?? template.authors ?? null;
-  let generator = meta.generator ?? template.generator ?? null;
-  const keywords = meta.keywords ?? template.keywords ?? null;
-  const manifest = meta.manifest ?? template.manifest ?? null;
-  const publisher = meta.publisher ?? template.publisher ?? null;
-  const referrer = meta.referrer ?? template.referrer ?? null;
-  const themeColor = meta.themeColor ?? template.themeColor ?? null;
-  const viewport = meta.viewport ?? template.viewport
-    ?? "width=device-width, initial-scale=1, maximum-scale=1";
+  const denyRobots = Boolean(pick(meta.denyRobots, template.denyRobots));
+  const authors = pick(meta.authors, template.authors);
+  const generator = pick(meta.generator, template.generator);
+  const keywords = pick(meta.keywords, template.keywords);
+  const manifest = pick(meta.manifest, template.manifest);
+  const publisher = pick(meta.publisher, template.publisher);
+  const referrer = pick(meta.referrer, template.referrer);
+  const themeColor = pick(meta.themeColor, template.themeColor);
+  const viewport = pick(
+    meta.viewport,
+    template.viewport,
+    "width=device-width, initial-scale=1, maximum-scale=1",
+  );
 
-  const alternates = meta.alternates ?? template.alternates ?? null;
-  const oEmbed = meta.oEmbed ?? template.oEmbed ?? null;
-  const embed = meta.embed ?? template.embed ?? null;
-  let openGraph = meta.openGraph ?? template.openGraph ?? null;
-  let twitter = meta.twitter ?? template.twitter ?? null;
+  const alternates = pick(meta.alternates, template.alternates);
+  const oEmbed = pick(meta.oEmbed, template.oEmbed);
+  const embed = pick(meta.embed, template.embed);
+  let openGraph = pick(meta.openGraph, template.openGraph);
+  let twitter = pick(meta.twitter, template.twitter);
   if (embed) {
-    const { thumbnail, thumbnailSize, siteTitle } = embed;
+    const { thumbnail, thumbnailSize, thumbnailAlt, siteTitle } = embed;
     openGraph = {
       type: "website",
-      title: embed.title ?? title,
+      title: embed.title ?? title ?? undefined,
       description: embed.description ?? description,
       ...openGraph,
     };
     twitter = {
+      title: embed.title ?? title ?? undefined,
+      description: embed.description ?? description ?? undefined,
       card: (thumbnailSize ?? (thumbnail ? "banner" : "icon")) === "banner"
         ? "summary_large_image"
         : "summary",
@@ -195,6 +203,10 @@ export function toTags(template: Template, meta: Meta): Tags {
       const resolved = new URL(thumbnail, template.base).href;
       openGraph.image = resolved;
       twitter.image = resolved;
+      if (thumbnailAlt) {
+        openGraph["image:alt"] = thumbnailAlt;
+        twitter["image:alt"] = thumbnailAlt;
+      }
     }
     if (siteTitle) {
       openGraph.site_name = siteTitle;
@@ -204,7 +216,7 @@ export function toTags(template: Template, meta: Meta): Tags {
     }
   }
 
-  const metaTags: Array<Record<string, string>> = [{ title }];
+  const metaTags: Array<Record<string, string>> = title == null ? [] : [{ title }];
   const links: Array<Record<string, string>> = [];
 
   if (description) metaTags.push({ name: "description", content: description });
@@ -246,7 +258,7 @@ export function toTags(template: Template, meta: Meta): Tags {
   const scriptTags: Array<Record<string, string | boolean>> = [];
   const styleTags: Array<Record<string, string>> = [];
 
-  for (const entry of meta.scripts ?? template.scripts ?? []) {
+  for (const entry of pick(meta.scripts, template.scripts) ?? []) {
     if ("content" in entry) {
       scriptTags.push({ children: String(entry.content) });
     } else {
@@ -259,7 +271,7 @@ export function toTags(template: Template, meta: Meta): Tags {
     }
   }
 
-  for (const entry of meta.styles ?? template.styles ?? []) {
+  for (const entry of pick(meta.styles, template.styles) ?? []) {
     if ("content" in entry) {
       const tag: Record<string, string> = { children: String(entry.content) };
       if ("media" in entry && entry.media) tag.media = entry.media;
@@ -274,7 +286,7 @@ export function toTags(template: Template, meta: Meta): Tags {
     }
   }
 
-  for (const { tag, ...attrs } of meta.extra ?? template.extra ?? []) {
+  for (const { tag, ...attrs } of pick(meta.extra, template.extra) ?? []) {
     const clean: Record<string, string | boolean> = {};
     for (const [k, v] of Object.entries(attrs)) {
       if (v != null && v !== false) clean[k] = v;
@@ -291,10 +303,13 @@ export function toTags(template: Template, meta: Meta): Tags {
 /* convert a metadata definition into HTML text. */
 export function toHtml(template: Template, meta: Meta): string {
   const tags = toTags(template, meta);
-  const [{ title }, ...metaTags] = tags.meta as [{ title: string }, ...Record<string, string>[]];
-  let out = `<title>${esc(title)}</title>`;
-  for (const attrs of metaTags) {
-    out += `<meta` + Object.entries(attrs).map(([k, v]) => ` ${k}=${attr(v)}`).join("") + `>`;
+  let out = "";
+  for (const attrs of tags.meta) {
+    if (Object.keys(attrs).length === 1 && "title" in attrs) {
+      out += `<title>${esc(attrs.title!)}</title>`;
+    } else {
+      out += `<meta` + Object.entries(attrs).map(([k, v]) => ` ${k}=${attr(v)}`).join("") + `>`;
+    }
   }
   for (const attrs of tags.links) {
     out += `<link` + Object.entries(attrs).map(([k, v]) => ` ${k}=${attr(v)}`).join("") + `>`;
@@ -324,9 +339,19 @@ function serializeAttrs(attrs: Record<string, string | boolean>): string {
   return out;
 }
 
+function pick<T>(value: T | null | undefined, template: T | null | undefined, fallback: T | null = null): T | null {
+  if (value !== undefined) return value;
+  if (template !== undefined) return template;
+  return fallback;
+}
+
 function collectOpenGraph(prefix: string, value: OpenGraphField): Array<Record<string, string>> {
   if (!value) return [];
-  if (typeof value === "string") return [{ name: prefix, content: value }];
+  if (typeof value === "string") {
+    // OG keys on `property`, twitter keys on `name`.
+    const key = prefix.startsWith("og:") ? "property" : "name";
+    return [{ [key]: prefix, content: value }];
+  }
   if (Array.isArray(value)) return value.flatMap((item) => collectOpenGraph(prefix, item));
   return Object.entries(value).flatMap(([key, item]) => collectOpenGraph(`${prefix}:${key}`, item));
 }
diff --git a/lib/readme.changes.md b/lib/readme.changes.md
index 48067405e35137742cfad5cff9c206e3df479d1b..0f40490c4dca90b0ac11b53ddedc42906dbc7d67 100644
--- a/lib/readme.changes.md
+++ b/lib/readme.changes.md
@@ -1,5 +1,27 @@
 # notable changes in clover's typescript library
 
+## v7
+
+### features
+
+- `meta`'s auto-embed feature now sets all the twitter tags, not just thumbnail.
+  sorry i might have been dumb when doing the first version of this.
+
+## v6
+
+### breaking
+
+- `meta` fields now distinguishes `undefined` and `null`. `null` acts as "unset"
+  and `undefined` acts as "fallthru to template".
+- rename `error` to `exception`
+
+### features
+
+- `meta`
+  - `title` can be optional for composition reasons.
+  - `embed.thumbnailAlt` sets `og:image:alt` + `twitter:image:alt`.
+  - emits `og:*` tags with `property=` instead of `name=`.
+
 ## v5
 
 ### breaking
diff --git a/lib/readme.md b/lib/readme.md
index 4622965780f42d10cc919bd5a77b6bba05aa04ba..a02c0c103afdb56dbcaa808198acb8e065b2d0ce 100644
--- a/lib/readme.md
+++ b/lib/readme.md
@@ -12,16 +12,17 @@ projects and at work.
 all top-level namespaces stand alone as their own projects, and generally do not
 depend on each other. there are no external dependencies; code is easy to audit.
 
-<!-- - `fs` - rebuilt api for `node:fs` -->
-
+- `array` - trivial helpers
 - `assert` - assertion and type narrowing functions
 - `async` - promise and asynchronous helpers
 - `bytes` - `Uint8Array` helpers
-- `error` - interop with the `unknown` type in error handlers
 - `Events` - typed event emitter
+- `exception` - interop with the `unknown` type in error handlers
+- `http` - basic http server and utilities
 - `log` - logging, terminal i/o, interactive widgets
 - `log/stack` - stack trace parse and formatter
 - `Lru` - least recently used cache
+- `math` - trivial helpers
 - `mime` - trimmed database of ext -> mime types
 - `node` - the Node.js javascript runtime
 - `progress` - cli progress bars, nesting status indication