diff --git a/apps/app/src/components/ui/markdown-message-directives.test.ts b/apps/app/src/components/ui/markdown-message-directives.test.ts
index 27dad6b4c..358873b04 100644
--- a/apps/app/src/components/ui/markdown-message-directives.test.ts
+++ b/apps/app/src/components/ui/markdown-message-directives.test.ts
@@ -81,4 +81,9 @@ describe("normalizeDirectiveAttributes / reconstructDirectiveSource", () => {
       reconstructDirectiveSource("inline-vis", { file: 'demo"x".html' }),
     ).toBe('::inline-vis{file="demo\\"x\\".html"}');
   });
+
+  it("uses the supplied marker for non-leaf directive kinds", () => {
+    expect(reconstructDirectiveSource("30", {}, ":")).toBe(":30");
+    expect(reconstructDirectiveSource("note", {}, ":::")).toBe(":::note");
+  });
 });
diff --git a/apps/app/src/components/ui/markdown-message-directives.test.tsx b/apps/app/src/components/ui/markdown-message-directives.test.tsx
index 3fe9a6700..9a2eda2f3 100644
--- a/apps/app/src/components/ui/markdown-message-directives.test.tsx
+++ b/apps/app/src/components/ui/markdown-message-directives.test.tsx
@@ -215,6 +215,56 @@ describe("MarkdownPreview message directives", () => {
     expect(screen.getByText('::inline-vis{file="still-streaming')).toBeTruthy();
   });
 
+  it("renders incidental prose colons literally without dropping text", () => {
+    // Regression: `remark-directive` parses `13:30`, `a:b`, and `:D` as text
+    // directives. Before the fix these fell through to mdast-util-to-hast as
+    // empty block `<div>`s, which split the paragraph and deleted the colon
+    // text — e.g. "next run 13:30." rendered as "next run 13" + a stray line
+    // break + ". ...".
+    const registry = buildMessageDirectiveRegistry([
+      slot({ id: "inline-vis", pluginId: "demo", component: InlineVis }),
+    ]);
+    const sentence =
+      "Watchdog runs every 30 min UTC, next run 13:30. It checks a:b and :D too.";
+    const { container } = render(
+      <MarkdownPreview
+        content={sentence}
+        messageDirectives={{
+          registry,
+          message: MESSAGE,
+          openWorkspaceFile: null,
+        }}
+      />,
+    );
+
+    const paragraphs = container.querySelectorAll("p");
+    expect(paragraphs).toHaveLength(1);
+    // Exact text preserved: no dropped `:30` / `:b` / `:D`.
+    expect(paragraphs[0]?.textContent).toBe(sentence);
+    // No block element was injected mid-paragraph to break the line.
+    expect(paragraphs[0]?.querySelector("div")).toBeNull();
+    expect(screen.queryByTestId("inline-vis")).toBeNull();
+  });
+
+  it("renders a container directive as literal source text", () => {
+    const registry = buildMessageDirectiveRegistry([
+      slot({ id: "inline-vis", pluginId: "demo", component: InlineVis }),
+    ]);
+    render(
+      <MarkdownPreview
+        content={":::note\nhello\n:::"}
+        messageDirectives={{
+          registry,
+          message: MESSAGE,
+          openWorkspaceFile: null,
+        }}
+      />,
+    );
+
+    expect(screen.queryByTestId("inline-vis")).toBeNull();
+    expect(screen.getByText(/:::note/)).toBeTruthy();
+  });
+
   it("falls back to original directive text when the plugin component crashes", () => {
     const registry = buildMessageDirectiveRegistry([
       slot({ id: "inline-vis", pluginId: "demo", component: CrashVis }),
diff --git a/apps/app/src/components/ui/markdown-message-directives.tsx b/apps/app/src/components/ui/markdown-message-directives.tsx
index f598e17ca..a65392f1a 100644
--- a/apps/app/src/components/ui/markdown-message-directives.tsx
+++ b/apps/app/src/components/ui/markdown-message-directives.tsx
@@ -76,8 +76,18 @@ export interface ResolvedMessageDirectives {
   registry: MessageDirectiveRegistry;
 }
 
-interface LeafDirectiveNode {
-  type: "leafDirective";
+/**
+ * `remark-directive` emits three node kinds from a single `:` grammar. Only the
+ * leaf form (`::name`) mounts a plugin component; the text and container forms
+ * are handled solely to rewrite them back to literal prose.
+ */
+type DirectiveNodeType =
+  | "textDirective"
+  | "leafDirective"
+  | "containerDirective";
+
+interface DirectiveNode {
+  type: DirectiveNodeType;
   name?: string;
   attributes?: Record<string, string | null | undefined> | null;
   children?: unknown[];
@@ -87,6 +97,13 @@ interface LeafDirectiveNode {
   };
 }
 
+/** Source marker for each directive kind (used to reconstruct literal text). */
+const DIRECTIVE_MARKERS: Record<DirectiveNodeType, string> = {
+  textDirective: ":",
+  leafDirective: "::",
+  containerDirective: ":::",
+};
+
 interface RemarkMessageDirectiveFile {
   value: unknown;
 }
@@ -177,22 +194,24 @@ export function normalizeDirectiveAttributes(
 export function reconstructDirectiveSource(
   name: string,
   attributes: Readonly<Record<string, string>>,
+  marker = "::",
 ): string {
   const keys = Object.keys(attributes);
   if (keys.length === 0) {
-    return `::${name}`;
+    return `${marker}${name}`;
   }
   const body = keys
     .map((key) => `${key}=${JSON.stringify(attributes[key] ?? "")}`)
     .join(" ");
-  return `::${name}{${body}}`;
+  return `${marker}${name}{${body}}`;
 }
 
 function directiveSourceFromNode(
-  node: LeafDirectiveNode,
+  node: DirectiveNode,
   markdownSource: string,
   name: string,
   attributes: Readonly<Record<string, string>>,
+  marker: string,
 ): string {
   const start = node.position?.start?.offset;
   const end = node.position?.end?.offset;
@@ -205,7 +224,7 @@ function directiveSourceFromNode(
   ) {
     return markdownSource.slice(start, end);
   }
-  return reconstructDirectiveSource(name, attributes);
+  return reconstructDirectiveSource(name, attributes, marker);
 }
 
 function messageDirectiveMountNode(index: number): RootContent {
@@ -221,25 +240,46 @@ function messageDirectiveMountNode(index: number): RootContent {
   };
 }
 
-function literalDirectiveNode(source: string): RootContent {
+function literalDirectiveNode(
+  type: DirectiveNodeType,
+  source: string,
+): RootContent {
+  // A text directive lives inside phrasing content (e.g. mid-paragraph), so it
+  // must be rewritten to an inline text node — not a block paragraph, which
+  // would split the surrounding text onto its own line. Leaf and container
+  // directives are block-level, so a paragraph is the correct literal stand-in.
+  if (type === "textDirective") {
+    return { type: "text", value: source };
+  }
   return {
     type: "paragraph",
     children: [{ type: "text", value: source }],
   };
 }
 
-function isLeafDirective(node: unknown): node is LeafDirectiveNode {
-  return (
-    typeof node === "object" &&
-    node !== null &&
-    (node as { type?: unknown }).type === "leafDirective"
-  );
+function asDirectiveNode(node: unknown): DirectiveNode | null {
+  if (typeof node !== "object" || node === null) {
+    return null;
+  }
+  const type = (node as { type?: unknown }).type;
+  if (
+    type === "textDirective" ||
+    type === "leafDirective" ||
+    type === "containerDirective"
+  ) {
+    return node as DirectiveNode;
+  }
+  return null;
 }
 
 /**
- * Remark transformer: rewrite recognized leaf directives into indexed custom
- * elements; leave unknown / collision / over-limit directives as literal
- * source text. Must run after `remark-directive` has produced leaf nodes.
+ * Remark transformer: rewrite recognized leaf directives (`::name`) into indexed
+ * custom elements; leave unknown / collision / over-limit leaf directives as
+ * literal source text. Text directives (`:name`) and container directives
+ * (`:::name`) never mount and are always rewritten to their literal source, so
+ * incidental prose colons (`13:30`, `key:value`, `:D`) render verbatim instead
+ * of collapsing into `mdast-util-to-hast`'s empty-`<div>` fallback. Must run
+ * after `remark-directive` has produced the directive nodes.
  *
  * Mutates `mounts` in document order so indices stay stable when later text
  * streams in after an already-complete directive.
@@ -256,35 +296,63 @@ export function remarkMessageDirectives(args: {
     // array reference does not accumulate duplicate indices.
     mounts.length = 0;
     visit(tree, (node, index, parent: Parent | undefined) => {
-      if (
-        !isLeafDirective(node) ||
-        parent === undefined ||
-        index === undefined
-      ) {
+      const directive = asDirectiveNode(node);
+      if (directive === null || parent === undefined || index === undefined) {
         return;
       }
-      const name = typeof node.name === "string" ? node.name : "";
-      const attributes = normalizeDirectiveAttributes(node.attributes);
+      const marker = DIRECTIVE_MARKERS[directive.type];
+      const name = typeof directive.name === "string" ? directive.name : "";
+      const attributes = normalizeDirectiveAttributes(directive.attributes);
       const source = directiveSourceFromNode(
-        node,
+        directive,
         markdownSource,
         name,
         attributes,
+        marker,
       );
 
+      // Only leaf directives (`::name`) mount a plugin component. Text
+      // directives (`:name`) and container directives (`:::name`) are almost
+      // always incidental parses of ordinary prose — a time like `13:30`, a
+      // `key:value` pair, an emoticon like `:D`. Left in the tree they reach
+      // `mdast-util-to-hast`, which renders an unknown directive as an empty
+      // block `<div>`; nested inside a paragraph that both drops the directive's
+      // text and injects a stray line break. Rewrite them back to literal
+      // source so the prose renders verbatim.
+      if (directive.type !== "leafDirective") {
+        parent.children.splice(
+          index,
+          1,
+          literalDirectiveNode(directive.type, source),
+        );
+        return index;
+      }
+
       if (name.length === 0) {
-        parent.children.splice(index, 1, literalDirectiveNode(source));
+        parent.children.splice(
+          index,
+          1,
+          literalDirectiveNode(directive.type, source),
+        );
         return index;
       }
 
       const entry = registry.get(name);
       if (entry === undefined || entry.status === "collision") {
-        parent.children.splice(index, 1, literalDirectiveNode(source));
+        parent.children.splice(
+          index,
+          1,
+          literalDirectiveNode(directive.type, source),
+        );
         return index;
       }
 
       if (mounts.length >= MESSAGE_DIRECTIVE_MOUNT_LIMIT) {
-        parent.children.splice(index, 1, literalDirectiveNode(source));
+        parent.children.splice(
+          index,
+          1,
+          literalDirectiveNode(directive.type, source),
+        );
         return index;
       }