diff --git a/docs/architecture/04-routing-and-events.md b/docs/architecture/04-routing-and-events.md
index 71f5c31..c73fc3e 100644
--- a/docs/architecture/04-routing-and-events.md
+++ b/docs/architecture/04-routing-and-events.md
@@ -51,14 +51,16 @@ picks a dataset itself when any exist, so the derived view immediately
 self-corrects to the `dataset-build` form.
 
 **One-shot action links are not view states.** A hash form that _requests an
-action_ (`#example-<id>`: add that gallery example and open it — spec §01E)
-stays out of the `ViewState` union: it is parsed by its own function in
-`url-hash.ts`, consumed once at startup (`orchestration/startup.ts`, after
-persistence wiring so the created record write-throughs, before `startRouting`),
-and then routing's settle step replaces the hash with the resulting view. It
-never serializes back and never participates in Back/Forward; `parseHash`
-degrades it like any unknown hash. Any future action link (e.g. a spec-payload
-link) follows the same shape rather than growing the view-state union.
+action_ — `#example-<id>` (add that gallery example) and `#spec-<payload>` (add
+the spec carried in the payload; `@core/spec-link` owns the base64url encoding,
+shared with the learn pages that build such links) — stays out of the
+`ViewState` union: each is parsed by its own function in `url-hash.ts`,
+consumed once at startup (`orchestration/startup.ts`, after persistence wiring
+so the created record write-throughs, before `startRouting`), and then
+routing's settle step replaces the hash with the resulting view. Action links
+never serialize back and never participate in Back/Forward; `parseHash`
+degrades them like any unknown hash. Any future action link follows the same
+shape rather than growing the view-state union.
 
 ### 1.2 The adapter: `infrastructure/url-hash.ts`
 
diff --git a/docs/spec/01-application-shell.md b/docs/spec/01-application-shell.md
index 34d2ea0..77512fd 100644
--- a/docs/spec/01-application-shell.md
+++ b/docs/spec/01-application-shell.md
@@ -102,7 +102,10 @@ Behavior:
 - On load, the app reads the hash and restores the corresponding state (selected snippet, Datasets list, a specific dataset, the new-dataset form, or the Chart Builder).
 - An empty/absent hash opens the default snippets view with no modal.
 
-**One-shot action link.** `#example-<id>` is not a view state but a request: on load, the app adds the matching gallery example (see _Snippet Library → First-Run & Empty Workspace_) as an ordinary snippet and opens it, then replaces the hash with the created snippet's view — so reloading does not re-add it, and the link never appears in Back/Forward history. Landing at it with an empty library skips the onboarding canvas and lays the workspace out at the same default split leaving the canvas would. An unknown id is ignored and the hash degrades to the default view. Each visit to such a link deliberately creates a new copy (same as pressing an example's **Add**). The landing uses these links (the hero's "Open in Astrolabe") to hand a visitor into the app carrying the chart they were just looking at.
+**One-shot action links.** Two hash forms are not view states but requests, consumed on load: the app adds a snippet, opens it, then replaces the hash with the created snippet's view — so reloading does not re-add it, and the link never appears in Back/Forward history. Landing at one with an empty library skips the onboarding canvas and lays the workspace out at the same default split leaving the canvas would. Each visit deliberately creates a new copy.
+
+- `#example-<id>` adds the matching gallery example (see _Snippet Library → First-Run & Empty Workspace_), named as in the gallery (same as pressing its **Add**). An unknown id is ignored and the hash degrades to the default view. The landing uses these links (the hero's "Open in Astrolabe") to hand a visitor into the app carrying the chart they were just looking at.
+- `#spec-<payload>` carries a spec's own text (base64url-encoded), so any sender — a lesson stage's "Open in Astrolabe", a shared link — can hand a self-contained spec into the app. The snippet's name derives from the spec (its `title`, else a "Mark chart of y by x" phrase, else "Shared spec"), like a pasted spec. A malformed payload is ignored and the hash degrades to the default view.
 
 ## F. Toast Notifications
 
diff --git a/src/app/infrastructure/url-hash.test.ts b/src/app/infrastructure/url-hash.test.ts
index d9ee460..3ce1450 100644
--- a/src/app/infrastructure/url-hash.test.ts
+++ b/src/app/infrastructure/url-hash.test.ts
@@ -2,6 +2,7 @@ import { describe, it, expect, beforeEach } from 'vitest';
 import {
   parseHash,
   parseExampleHash,
+  parseSpecHash,
   serializeHash,
   readView,
   replaceView,
@@ -94,6 +95,23 @@ describe('parseExampleHash', () => {
   });
 });
 
+describe('parseSpecHash', () => {
+  it('extracts the payload from the one-shot spec link', () => {
+    expect(parseSpecHash('#spec-eyJtYXJrIjoiYmFyIn0')).toBe('eyJtYXJrIjoiYmFyIn0');
+    expect(parseSpecHash('spec-AAAA')).toBe('AAAA'); // leading "#" optional
+  });
+
+  it('returns null for anything that is not a spec link', () => {
+    expect(parseSpecHash('')).toBeNull();
+    expect(parseSpecHash('#spec-')).toBeNull(); // empty payload
+    expect(parseSpecHash('#example-brush')).toBeNull();
+  });
+
+  it('is not a ViewState: parseHash degrades a spec link to the default view', () => {
+    expect(parseHash('#spec-eyJtYXJrIjoiYmFyIn0')).toEqual({ kind: 'snippets' });
+  });
+});
+
 describe('round-trip identity', () => {
   it('parseHash(serializeHash(v)) deep-equals v for every variant', () => {
     for (const v of ALL_VIEWS) {
diff --git a/src/app/infrastructure/url-hash.ts b/src/app/infrastructure/url-hash.ts
index 9626b52..b7ea028 100644
--- a/src/app/infrastructure/url-hash.ts
+++ b/src/app/infrastructure/url-hash.ts
@@ -107,6 +107,24 @@ export function readExampleId(): string | null {
   return parseExampleHash(window.location.hash);
 }
 
+/**
+ * The second action link: `#spec-<payload>` carries a spec's text itself
+ * (base64url — `@core/spec-link` owns the encoding), so a lesson stage or any
+ * sender can hand a self-contained spec into the app. Same one-shot contract
+ * as `#example-<id>`. The base64url alphabet has no percent-escapes, so
+ * reading `location.hash` is safe even in Firefox (which returns the hash
+ * percent-decoded).
+ */
+export function parseSpecHash(rawHash: string): string | null {
+  const m = /^spec-(.+)$/.exec(rawHash.replace(/^#/, ''));
+  return m ? m[1] : null;
+}
+
+/** Read the one-shot spec payload from the current URL, if any. */
+export function readSpecPayload(): string | null {
+  return parseSpecHash(window.location.hash);
+}
+
 /** Read the current view from `window.location.hash`. */
 export function readView(): ViewState {
   return parseHash(window.location.hash);
diff --git a/src/app/orchestration/startup.ts b/src/app/orchestration/startup.ts
index 0aaa7c3..89db946 100644
--- a/src/app/orchestration/startup.ts
+++ b/src/app/orchestration/startup.ts
@@ -13,7 +13,9 @@ import type { Dataset } from '@core/dataset';
 import type { CustomTheme } from '@core/custom-theme';
 import type { FontAsset } from '@core/font-asset';
 import { CHART_EXAMPLES, exampleSpecText } from '@core/examples';
-import { readExampleId } from '../infrastructure/url-hash';
+import { deriveSnippetName } from '@core/snippet';
+import { decodeSpecPayload } from '@core/spec-link';
+import { readExampleId, readSpecPayload } from '../infrastructure/url-hash';
 import { loadSnippets } from '../infrastructure/snippet-store';
 import { loadDatasets } from '../infrastructure/dataset-store';
 import { loadCustomThemes } from '../infrastructure/theme-store';
@@ -98,29 +100,44 @@ export async function initApp(): Promise<void> {
   wireThemePersistence();
   wireFontPersistence();
 
-  // One-shot deep link (spec §01E): `#example-<id>` — the landing's hand-off
-  // links — adds that gallery example as an ordinary snippet and opens it. It
-  // runs after persistence wiring (so the new snippet write-throughs; anything
-  // created before wiring would be treated as loaded baseline and never saved)
-  // and before routing (whose settle step below replaces the hash with the
-  // created snippet's view, so a reload doesn't re-add it). An unknown id is
-  // ignored and the hash degrades to the default view.
+  // One-shot action links (spec §01E): `#example-<id>` (the landing's hand-off
+  // links) adds that gallery example; `#spec-<payload>` (lesson stages, shared
+  // links) carries the spec text itself. Both add an ordinary snippet and open
+  // it. They run after persistence wiring (so the new snippet write-throughs;
+  // anything created before wiring would be treated as loaded baseline and
+  // never saved) and before routing (whose settle step below replaces the hash
+  // with the created snippet's view, so a reload doesn't re-add it). An unknown
+  // id or malformed payload is ignored and the hash degrades to the default view.
   // TODO: the ordering constraints above (after wiring, before routing) have no
   // automated coverage — an initApp integration test (fake-indexeddb + stubbed
   // location.hash) would catch a reorder silently breaking the marketing links.
+  const addLinkedSnippet = (options: {
+    name: string;
+    spec: string;
+    nameSource?: 'auto' | 'user';
+  }): void => {
+    const firstSnippet = useSnippetStore.getState().snippets.length === 0;
+    useSnippetStore.getState().createSnippet(options);
+    // Entering the workspace directly, the onboarding canvas never shows — so
+    // give a first chart the same generous default split leaving it would
+    // (spec §02 → First-Run & Empty Workspace).
+    if (firstSnippet) usePanesStore.getState().applyOnboardingSplit(window.innerWidth);
+  };
   const exampleId = readExampleId();
-  if (exampleId) {
-    const example = CHART_EXAMPLES.find((e) => e.id === exampleId);
-    if (example) {
-      const firstSnippet = useSnippetStore.getState().snippets.length === 0;
-      useSnippetStore.getState().createSnippet({
-        name: example.name,
-        spec: exampleSpecText(example),
+  const example = exampleId ? CHART_EXAMPLES.find((e) => e.id === exampleId) : undefined;
+  if (example) {
+    // Same semantics as the gallery's Add: a curated name the user chose.
+    addLinkedSnippet({ name: example.name, spec: exampleSpecText(example) });
+  } else {
+    const payload = readSpecPayload();
+    const specText = payload !== null ? decodeSpecPayload(payload) : null;
+    if (specText !== null) {
+      // Same semantics as the paste door: derived name that tracks the spec.
+      addLinkedSnippet({
+        name: deriveSnippetName(specText) ?? 'Shared spec',
+        nameSource: 'auto',
+        spec: specText,
       });
-      // Entering the workspace directly, the onboarding canvas never shows — so
-      // give a first chart the same generous default split leaving it would
-      // (spec §02 → First-Run & Empty Workspace).
-      if (firstSnippet) usePanesStore.getState().applyOnboardingSplit(window.innerWidth);
     }
   }