diff --git a/apps/web/src/components/ComposerPromptEditorTiptap.tsx b/apps/web/src/components/ComposerPromptEditorTiptap.tsx
index 0fff87e76851..4fd3022e6d8d 100644
--- a/apps/web/src/components/ComposerPromptEditorTiptap.tsx
+++ b/apps/web/src/components/ComposerPromptEditorTiptap.tsx
@@ -62,7 +62,7 @@ import {
   groupUndoByChangeKind,
   markAsClipboardEdit,
 } from "~/composer-undo-grouping";
-import { setTypingMarksAfterPaste } from "~/composer-paste-marks";
+import { ComposerTypingMarksExtension } from "~/composer-typing-marks";
 import { collectInlineContextIds } from "~/lib/composerContextReferences";
 import { cn, isMacPlatform } from "~/lib/utils";
 import { basenameOfPath } from "~/pierre-icons";
@@ -833,6 +833,7 @@ function ComposerPromptEditorTiptapInner(props: ComposerPromptEditorProps) {
         ComposerMarkersExtension,
         ...(richText
           ? [
+              ComposerTypingMarksExtension,
               ComposerCodeExtension,
               TaskList,
               ComposerTaskItemExtension.extend({
@@ -1073,10 +1074,6 @@ function ComposerPromptEditorTiptapInner(props: ComposerPromptEditorProps) {
                 .insertContent(content)
                 .run();
             });
-            if (richText) {
-              const resetMarks = setTypingMarksAfterPaste(editorInstance.state);
-              if (resetMarks) editorInstance.view.dispatch(resetMarks);
-            }
             scrollTiptapCaretIntoView(editorInstance);
           }
           return true;
diff --git a/apps/web/src/composer-paste-marks.test.ts b/apps/web/src/composer-paste-marks.test.ts
deleted file mode 100644
index e8b4b57242e8..000000000000
--- a/apps/web/src/composer-paste-marks.test.ts
+++ /dev/null
@@ -1,52 +0,0 @@
-import { Schema } from "@tiptap/pm/model";
-import { EditorState, TextSelection } from "@tiptap/pm/state";
-import { describe, expect, it } from "vite-plus/test";
-
-import { serializeEditorDoc } from "./composer-rich-text-doc";
-import { setTypingMarksAfterPaste } from "./composer-paste-marks";
-
-const schema = new Schema({
-  nodes: {
-    doc: { content: "block+" },
-    paragraph: { content: "inline*", group: "block" },
-    text: { group: "inline" },
-  },
-  marks: { bold: {}, italic: {} },
-});
-
-describe("typing after pasted formatting", () => {
-  it("continues in plain text after a bold paste at the end of a line", () => {
-    const doc = schema.node("doc", null, [
-      schema.node("paragraph", null, [schema.text("bold", [schema.marks.bold!.create()])]),
-    ]);
-    const state = EditorState.create({ doc, selection: TextSelection.create(doc, 5) });
-
-    expect(serializeEditorDoc(state.apply(state.tr.insertText(" plain")).doc).value).toBe(
-      "**bold plain**",
-    );
-    const continued = state.apply(setTypingMarksAfterPaste(state)!);
-    expect(serializeEditorDoc(continued.apply(continued.tr.insertText(" plain")).doc).value).toBe(
-      "**bold** plain",
-    );
-  });
-
-  it("uses the formatting of following text when pasting in the middle", () => {
-    const doc = schema.node("doc", null, [
-      schema.node("paragraph", null, [
-        schema.text("bold", [schema.marks.bold!.create()]),
-        schema.text("tail", [schema.marks.italic!.create()]),
-      ]),
-    ]);
-    const state = EditorState.create({ doc, selection: TextSelection.create(doc, 5) });
-    const continued = state.apply(setTypingMarksAfterPaste(state)!);
-    const withText = continued.apply(continued.tr.insertText("x")).doc;
-
-    expect(withText.child(0).child(1).text).toBe("xtail");
-    expect(
-      withText
-        .child(0)
-        .child(1)
-        .marks.map((mark) => mark.type.name),
-    ).toEqual(["italic"]);
-  });
-});
diff --git a/apps/web/src/composer-paste-marks.ts b/apps/web/src/composer-paste-marks.ts
deleted file mode 100644
index 9517bc5698d1..000000000000
--- a/apps/web/src/composer-paste-marks.ts
+++ /dev/null
@@ -1,7 +0,0 @@
-import type { EditorState, Transaction } from "@tiptap/pm/state";
-
-/** Continue after pasted formatting with the text on the right, or plain at a line end. */
-export function setTypingMarksAfterPaste(state: EditorState): Transaction | null {
-  if (!state.selection.empty) return null;
-  return state.tr.setStoredMarks(state.selection.$from.nodeAfter?.marks ?? []);
-}
diff --git a/apps/web/src/composer-typing-marks.test.ts b/apps/web/src/composer-typing-marks.test.ts
new file mode 100644
index 000000000000..e6026874a2d0
--- /dev/null
+++ b/apps/web/src/composer-typing-marks.test.ts
@@ -0,0 +1,163 @@
+import { getSchema } from "@tiptap/core";
+import StarterKit from "@tiptap/starter-kit";
+import { history, redo, undo } from "@tiptap/pm/history";
+import { EditorState, TextSelection } from "@tiptap/pm/state";
+import { describe, expect, it } from "vite-plus/test";
+
+import { buildDocJson, ComposerCodeExtension, serializeEditorDoc } from "./composer-rich-text-doc";
+import { createComposerTypingMarksPlugin } from "./composer-typing-marks";
+
+const schema = getSchema([StarterKit.configure({ code: false }), ComposerCodeExtension]);
+
+function createState(value: string, cursor: number) {
+  const doc = schema.nodeFromJSON(buildDocJson(value, () => ({ label: "", description: null })));
+  return EditorState.create({
+    doc,
+    selection: TextSelection.create(doc, cursor),
+    plugins: [createComposerTypingMarksPlugin(), history()],
+  });
+}
+
+function move(state: EditorState, cursor: number) {
+  return state.applyTransaction(state.tr.setSelection(TextSelection.create(state.doc, cursor)))
+    .state;
+}
+
+function type(state: EditorState, text: string) {
+  for (const character of text)
+    state = state.applyTransaction(state.tr.insertText(character)).state;
+  return state;
+}
+
+function value(state: EditorState) {
+  return serializeEditorDoc(state.doc).value;
+}
+
+describe("composer typing marks after moving the caret", () => {
+  it.each(["**b**", "*b*", "~~b~~", "`b`", "***b***", "**`b`**"])(
+    "types plain text after navigating away from and back to %s",
+    (markdown) => {
+      let state = createState(markdown, 2);
+      state = state.applyTransaction(state.tr.setStoredMarks([])).state;
+      state = move(move(state, 1), 2);
+      expect(value(type(state, " plain"))).toBe(`${markdown} plain`);
+    },
+  );
+
+  it("covers caret placement after a controlled rewrite, including an unchanged position", () => {
+    let state = createState("x", 2);
+    const content = schema.nodeFromJSON(
+      buildDocJson("**b**", () => ({ label: "", description: null })),
+    );
+    state = state.applyTransaction(
+      state.tr.replaceWith(0, state.doc.content.size, content.content),
+    ).state;
+    state = move(state, 2);
+    expect(value(type(state, " plain"))).toBe("**b** plain");
+  });
+
+  it("resets typing marks after a paste and subsequent navigation", () => {
+    let state = createState("", 1);
+    const content = schema.nodeFromJSON(
+      buildDocJson("**b**", () => ({ label: "", description: null })),
+    );
+    state = state.applyTransaction(
+      state.tr.replaceSelectionWith(content.firstChild!, false).setMeta("uiEvent", "paste"),
+    ).state;
+    expect(value(type(state, " plain"))).toBe("**b** plain");
+    state = move(move(state, 1), 2);
+    expect(value(type(state, " plain"))).toBe("**b** plain");
+  });
+
+  it("continues the following span after pasting in the middle of a line", () => {
+    let state = createState("tail", 1);
+    state = state.applyTransaction(
+      state.tr
+        .insertText("b")
+        .addMark(1, 2, schema.marks.bold!.create())
+        .setMeta("uiEvent", "paste"),
+    ).state;
+    expect(value(type(state, "xy"))).toBe("**b**xytail");
+  });
+
+  it("types plain after cutting back to a closing boundary", () => {
+    let state = createState("**b** plain", 8);
+    state = state.applyTransaction(
+      state.tr
+        .setSelection(TextSelection.create(state.doc, 2, 8))
+        // Tiptap's deleteSelection command uses deleteRange without ensureMarks.
+        .deleteRange(2, 8)
+        .setMeta("uiEvent", "cut"),
+    ).state;
+    expect(value(state)).toBe("**b**");
+    expect(value(type(state, " plain"))).toBe("**b** plain");
+  });
+
+  it("preserves formatting while typing inside a span", () => {
+    const state = move(createState("**bold**", 5), 3);
+    expect(value(type(state, "xy"))).toBe("**boxyld**");
+  });
+
+  it("adopts following text marks at a boundary", () => {
+    const state = move(createState("**b***tail*", 6), 2);
+    expect(value(type(state, "xy"))).toBe("**b***xytail*");
+  });
+
+  it("matches the opening marker when placing the caret before formatted text", () => {
+    const state = move(createState("x **bold**", 7), 3);
+    expect(value(type(state, "xy"))).toBe("x **xybold**");
+  });
+
+  it("preserves explicit formatting on and off over several keystrokes", () => {
+    let state = move(createState("**b**", 2), 2);
+    state = state.applyTransaction(state.tr.addStoredMark(schema.marks.bold!.create())).state;
+    state = type(state, "xy");
+    expect(value(state)).toBe("**bxy**");
+    state = state.applyTransaction(state.tr.removeStoredMark(schema.marks.bold!)).state;
+    expect(value(type(state, " plain"))).toBe("**bxy** plain");
+  });
+
+  it("preserves an explicit mark decision in a selection transaction", () => {
+    let state = createState("**b**", 1);
+    state = state.applyTransaction(
+      state.tr
+        .setSelection(TextSelection.create(state.doc, 2))
+        .addStoredMark(schema.marks.italic!.create()),
+    ).state;
+    expect(value(type(state, "xy"))).toBe("**b*xy***");
+  });
+
+  it("does not alter ranged selection replacement", () => {
+    let state = createState("**bold**", 5);
+    state = state.applyTransaction(
+      state.tr.setSelection(TextSelection.create(state.doc, 2, 4)),
+    ).state;
+    expect(value(type(state, "x"))).toBe("**bxd**");
+  });
+
+  it("leaves normal typing transactions alone", () => {
+    const state = createState("**b**", 2);
+    expect(value(type(state, "xy"))).toBe("**bxy**");
+    expect(state.applyTransaction(state.tr.scrollIntoView()).transactions).toHaveLength(1);
+  });
+
+  it("adds no undo step and preserves undo/redo content and selection", () => {
+    let state = move(move(createState("**b**", 2), 1), 2);
+    state = type(state, " plain");
+    expect(
+      undo(state, (transaction) => {
+        state = state.applyTransaction(transaction).state;
+      }),
+    ).toBe(true);
+    expect(value(state)).toBe("**b**");
+    expect(state.selection.from).toBe(2);
+    expect(value(type(state, " again"))).toBe("**b** again");
+    expect(
+      redo(state, (transaction) => {
+        state = state.applyTransaction(transaction).state;
+      }),
+    ).toBe(true);
+    expect(value(state)).toBe("**b** plain");
+    expect(state.selection.from).toBe(8);
+  });
+});
diff --git a/apps/web/src/composer-typing-marks.ts b/apps/web/src/composer-typing-marks.ts
new file mode 100644
index 000000000000..7607f1b961ce
--- /dev/null
+++ b/apps/web/src/composer-typing-marks.ts
@@ -0,0 +1,38 @@
+import { Extension } from "@tiptap/core";
+import { isHistoryTransaction } from "@tiptap/pm/history";
+import { Mark } from "@tiptap/pm/model";
+import { Plugin } from "@tiptap/pm/state";
+
+/**
+ * Follow the text on the right when moving the caret, or type plain at a line end.
+ * Keep inclusive marks during edits so explicit formatting shortcuts continue typing.
+ */
+export function createComposerTypingMarksPlugin() {
+  return new Plugin({
+    appendTransaction(transactions, _oldState, state) {
+      if (
+        !state.selection.empty ||
+        state.storedMarks !== null ||
+        !transactions.some(
+          (transaction) =>
+            (transaction.selectionSet && !transaction.docChanged) ||
+            isHistoryTransaction(transaction) ||
+            transaction.getMeta("uiEvent") === "paste" ||
+            transaction.getMeta("uiEvent") === "cut",
+        )
+      ) {
+        return null;
+      }
+      const marks = state.selection.$from.nodeAfter?.marks ?? [];
+      if (Mark.sameSet(marks, state.selection.$from.marks())) return null;
+      return state.tr.setStoredMarks(marks);
+    },
+  });
+}
+
+export const ComposerTypingMarksExtension = Extension.create({
+  name: "composer-typing-marks",
+  addProseMirrorPlugins() {
+    return [createComposerTypingMarksPlugin()];
+  },
+});