diff --git a/apps/web/e2e/user-profile-edit.spec.ts b/apps/web/e2e/user-profile-edit.spec.ts
new file mode 100644
index 0000000..612ab13
--- /dev/null
+++ b/apps/web/e2e/user-profile-edit.spec.ts
@@ -0,0 +1,74 @@
+/**
+ * E2E: Settings → About you edits a fact in place: its wording, category and the spaces it
+ * shows in.
+ */
+import { expect, test } from "@playwright/test";
+import type { UserProfileState } from "@rakazo/contracts";
+import { captureScreenshot, completeOnboarding, openUserSettings, rpc, signup } from "./helpers";
+
+test("a fact's wording, category and spaces are edited in place", async ({ page }, testInfo) => {
+  const stamp = Date.now();
+  await signup(page, `profile-edit-${stamp}@rakazo.test`, "password12", "Edit Tester");
+  await completeOnboarding(page);
+  const side = await rpc<{ id: string }>(page, "spaces/create", { name: "Side project" });
+  await rpc(page, "profile/update", {
+    addFacts: [{ category: "preferences", value: "Prefers tea" }],
+  });
+
+  const settings = await openUserSettings(page, "profile");
+  const profile = settings.getByTestId("user-profile-settings");
+  const tea = profile.getByTestId("user-fact").filter({ hasText: "Prefers tea" });
+  await tea.getByRole("button", { name: "Edit" }).click();
+
+  const editor = profile.getByTestId("user-fact-editor");
+  const wording = editor.getByRole("textbox", { name: "Fact" });
+  await expect(wording).toBeFocused();
+  await wording.fill("Prefers green tea");
+  await editor.getByRole("combobox", { name: "Category" }).selectOption("habits");
+  await editor.getByRole("button", { name: "All spaces" }).click();
+  await page.getByRole("menuitemcheckbox", { name: "Side project" }).click();
+  await expect(page.getByRole("menuitemcheckbox", { name: "All spaces" })).not.toBeChecked();
+  await page.keyboard.press("Escape");
+  await expect(editor.getByRole("button", { name: "Side project" })).toBeVisible();
+  await captureScreenshot(page, testInfo, "user-profile-edit");
+
+  await editor.getByRole("button", { name: "Save", exact: true }).click();
+  await expect(editor).toHaveCount(0);
+  const edited = profile
+    .getByTestId("user-facts-habits")
+    .getByTestId("user-fact")
+    .filter({ hasText: "Prefers green tea" });
+  await expect(edited).toContainText("Side project");
+  await expect(tea).toHaveCount(0);
+  const teaFact = async () =>
+    (await rpc<UserProfileState>(page, "profile/get", null)).facts.find((fact) =>
+      fact.value.includes("tea"),
+    );
+  expect(await teaFact()).toMatchObject({
+    value: "Prefers green tea",
+    category: "habits",
+    allSpaces: false,
+    spaceIds: [side.id],
+  });
+
+  // Escape leaves the fact as it was; showing it everywhere again clears the limit.
+  await edited.getByRole("button", { name: "Edit" }).click();
+  await editor.getByRole("textbox", { name: "Fact" }).fill("Discarded");
+  await page.keyboard.press("Escape");
+  await expect(editor).toHaveCount(0);
+  await expect(edited).toContainText("Prefers green tea");
+  await expect(settings).toBeVisible();
+
+  await edited.getByRole("button", { name: "Edit" }).click();
+  await editor.getByRole("button", { name: "Side project" }).click();
+  await page.getByRole("menuitemcheckbox", { name: "All spaces" }).click();
+  await page.keyboard.press("Escape");
+  await editor.getByRole("button", { name: "Save", exact: true }).click();
+  await expect(editor).toHaveCount(0);
+  await expect(edited).not.toContainText("Side project");
+  expect(await teaFact()).toMatchObject({
+    value: "Prefers green tea",
+    allSpaces: true,
+    spaceIds: [],
+  });
+});
diff --git a/apps/web/src/components/UserFactEditor.tsx b/apps/web/src/components/UserFactEditor.tsx
new file mode 100644
index 0000000..a7b7e9a
--- /dev/null
+++ b/apps/web/src/components/UserFactEditor.tsx
@@ -0,0 +1,129 @@
+import { Trans, useLingui } from "@lingui/react/macro";
+import type { UserFact, UserFactCategory } from "@rakazo/contracts";
+import { USER_FACT_CATEGORIES, USER_FACT_VALUE_MAX_LENGTH } from "@rakazo/contracts";
+import {
+  Button,
+  DropdownMenu,
+  DropdownMenuCheckboxItem,
+  DropdownMenuContent,
+  DropdownMenuSeparator,
+  DropdownMenuTrigger,
+  Input,
+  NativeSelect,
+  NativeSelectOption,
+} from "@rakazo/ui-web";
+import { ChevronDownIcon } from "lucide-react";
+import { useState } from "react";
+import type { UserFactDraft } from "../lib/user-profile-view";
+import { factSpaceNames, toggleFactSpace, userFactDraft } from "../lib/user-profile-view";
+
+/** Edits one fact in place: its wording, category and, with more than one space, where it shows. */
+export function UserFactEditor({
+  fact,
+  spaces,
+  categoryLabels,
+  busy,
+  onSave,
+  onCancel,
+}: {
+  fact: UserFact;
+  /** The user's spaces; the visibility control appears with more than one. */
+  spaces: ReadonlyArray<{ id: string; name: string }>;
+  categoryLabels: Record<UserFactCategory, string>;
+  busy: boolean;
+  onSave: (draft: UserFactDraft) => void;
+  onCancel: () => void;
+}) {
+  const { t } = useLingui();
+  const [draft, setDraft] = useState(() => userFactDraft(fact));
+  const allSpaces = t`All spaces`;
+  const showSpaces = spaces.length > 1 || draft.spaceIds !== null;
+
+  return (
+    <li data-testid="user-fact-editor">
+      <form
+        className="space-y-2"
+        onSubmit={(event) => {
+          event.preventDefault();
+          if (draft.value.trim()) onSave(draft);
+        }}
+        onKeyDown={(event) => {
+          // The spaces menu renders in a portal; its Escape only closes the menu.
+          if (event.key === "Escape" && event.currentTarget.contains(event.target as Node)) {
+            event.stopPropagation();
+            onCancel();
+          }
+        }}
+      >
+        <Input
+          autoFocus
+          aria-label={t`Fact`}
+          value={draft.value}
+          maxLength={USER_FACT_VALUE_MAX_LENGTH}
+          onChange={(event) => setDraft({ ...draft, value: event.target.value })}
+        />
+        <div className="flex flex-wrap items-center gap-2">
+          <NativeSelect
+            size="sm"
+            aria-label={t`Category`}
+            value={draft.category}
+            onChange={(event) =>
+              setDraft({ ...draft, category: event.target.value as UserFactCategory })
+            }
+          >
+            {USER_FACT_CATEGORIES.map((category) => (
+              <NativeSelectOption key={category} value={category}>
+                {categoryLabels[category]}
+              </NativeSelectOption>
+            ))}
+          </NativeSelect>
+          {showSpaces ? (
+            <DropdownMenu>
+              <DropdownMenuTrigger
+                render={<Button type="button" variant="outline" size="sm" className="max-w-56" />}
+              >
+                <span className="truncate">
+                  {factSpaceNames(draft.spaceIds, spaces).join(", ") || allSpaces}
+                </span>
+                <ChevronDownIcon aria-hidden="true" />
+              </DropdownMenuTrigger>
+              <DropdownMenuContent className="w-auto min-w-44">
+                <DropdownMenuCheckboxItem
+                  checked={draft.spaceIds === null}
+                  onCheckedChange={() => setDraft({ ...draft, spaceIds: null })}
+                >
+                  {allSpaces}
+                </DropdownMenuCheckboxItem>
+                <DropdownMenuSeparator />
+                {spaces.map((space) => (
+                  <DropdownMenuCheckboxItem
+                    key={space.id}
+                    checked={draft.spaceIds?.includes(space.id) ?? false}
+                    onCheckedChange={(checked) =>
+                      setDraft({
+                        ...draft,
+                        spaceIds: toggleFactSpace(draft.spaceIds, space.id, checked),
+                      })
+                    }
+                  >
+                    <span className="truncate" dir="auto">
+                      {space.name}
+                    </span>
+                  </DropdownMenuCheckboxItem>
+                ))}
+              </DropdownMenuContent>
+            </DropdownMenu>
+          ) : null}
+          <div className="ms-auto flex items-center gap-1">
+            <Button type="button" variant="ghost" size="sm" disabled={busy} onClick={onCancel}>
+              <Trans>Cancel</Trans>
+            </Button>
+            <Button type="submit" size="sm" disabled={busy || !draft.value.trim()}>
+              <Trans>Save</Trans>
+            </Button>
+          </div>
+        </div>
+      </form>
+    </li>
+  );
+}
diff --git a/apps/web/src/components/UserProfileSettings.tsx b/apps/web/src/components/UserProfileSettings.tsx
index 6a8e2e3..3811a9a 100644
--- a/apps/web/src/components/UserProfileSettings.tsx
+++ b/apps/web/src/components/UserProfileSettings.tsx
@@ -10,7 +10,7 @@ import {
   AlertDialogTitle,
   Button,
 } from "@rakazo/ui-web";
-import { XIcon } from "lucide-react";
+import { PencilIcon, XIcon } from "lucide-react";
 import type { ReactNode } from "react";
 import { useEffect, useId, useState } from "react";
 import { getActiveUiLocale } from "../lib/i18n";
@@ -20,9 +20,12 @@ import {
   CLEARED_PROFILE_FIELD,
   displayLanguageTag,
   displayRegionTag,
+  factSpaceNames,
   filledProfileFields,
   groupUserFacts,
+  userFactEdit,
 } from "../lib/user-profile-view";
+import { UserFactEditor } from "./UserFactEditor";
 
 function Row({
   value,
@@ -51,14 +54,30 @@ function Row({
   );
 }
 
-/** Everything the user's bots know about the user, with consent and forget controls. */
+/** Everything the user's bots know about the user, with edit, consent and forget controls. */
 export function UserProfileSettings() {
   const { t } = useLingui();
   const [state, setState] = useState<UserProfileState | null>(null);
+  const [spaces, setSpaces] = useState<Array<{ id: string; name: string }>>([]);
+  const [editingId, setEditingId] = useState<string | null>(null);
   const [busy, setBusy] = useState(false);
   const [error, setError] = useState<string | null>(null);
   const [forgetOpen, setForgetOpen] = useState(false);
 
+  useEffect(() => {
+    let cancelled = false;
+    // Only names a fact's spaces; without them the profile still works.
+    rpc.spaces
+      .list()
+      .then((navigation) => {
+        if (!cancelled) setSpaces(navigation.spaces.map(({ id, name }) => ({ id, name })));
+      })
+      .catch(() => undefined);
+    return () => {
+      cancelled = true;
+    };
+  }, []);
+
   useEffect(() => {
     let cancelled = false;
     rpc.profile
@@ -74,14 +93,16 @@ export function UserProfileSettings() {
     };
   }, [t]);
 
-  async function apply(change: () => Promise<UserProfileState>) {
-    if (busy) return;
+  async function apply(change: () => Promise<UserProfileState>): Promise<boolean> {
+    if (busy) return false;
     setBusy(true);
     setError(null);
     try {
       setState(await change());
+      return true;
     } catch (err) {
       setError(err instanceof Error ? err.message : t`Couldn't save`);
+      return false;
     } finally {
       setBusy(false);
     }
@@ -178,36 +199,75 @@ export function UserProfileSettings() {
             {categoryLabels[group.category]}
           </h3>
           <ul className="mt-3 space-y-3">
-            {group.facts.map((fact) => (
-              <Row
-                key={fact.id}
-                testId="user-fact"
-                status={fact.status}
-                value={fact.value}
-                detail={sourceLabels[fact.source]}
-                actions={(describedBy) => (
-                  <>
-                    {fact.status === "pending" ? (
+            {group.facts.map((fact) =>
+              fact.id === editingId ? (
+                <UserFactEditor
+                  key={fact.id}
+                  fact={fact}
+                  spaces={spaces}
+                  categoryLabels={categoryLabels}
+                  busy={busy}
+                  onCancel={() => setEditingId(null)}
+                  onSave={(draft) => {
+                    const edit = userFactEdit(fact, draft);
+                    if (!edit) {
+                      setEditingId(null);
+                      return;
+                    }
+                    void apply(() => rpc.profile.update({ editFacts: [edit] })).then((saved) => {
+                      if (saved) setEditingId(null);
+                    });
+                  }}
+                />
+              ) : (
+                <Row
+                  key={fact.id}
+                  testId="user-fact"
+                  status={fact.status}
+                  value={fact.value}
+                  detail={[
+                    sourceLabels[fact.source],
+                    factSpaceNames(fact.allSpaces ? null : fact.spaceIds, spaces).join(", "),
+                  ]
+                    .filter(Boolean)
+                    .join(" · ")}
+                  actions={(describedBy) => (
+                    <>
+                      {fact.status === "pending" ? (
+                        <Button
+                          variant="outline"
+                          size="sm"
+                          aria-describedby={describedBy}
+                          disabled={busy}
+                          onClick={() =>
+                            void apply(() => rpc.profile.update({ confirmFactIds: [fact.id] }))
+                          }
+                        >
+                          <Trans>Confirm</Trans>
+                        </Button>
+                      ) : null}
                       <Button
-                        variant="outline"
-                        size="sm"
+                        variant="ghost"
+                        size="icon-sm"
+                        aria-label={t`Edit`}
                         aria-describedby={describedBy}
                         disabled={busy}
-                        onClick={() =>
-                          void apply(() => rpc.profile.update({ confirmFactIds: [fact.id] }))
-                        }
+                        onClick={() => {
+                          setError(null);
+                          setEditingId(fact.id);
+                        }}
                       >
-                        <Trans>Confirm</Trans>
+                        <PencilIcon />
                       </Button>
-                    ) : null}
-                    {deleteButton(
-                      describedBy,
-                      () => void apply(() => rpc.profile.forget({ factIds: [fact.id] })),
-                    )}
-                  </>
-                )}
-              />
-            ))}
+                      {deleteButton(
+                        describedBy,
+                        () => void apply(() => rpc.profile.forget({ factIds: [fact.id] })),
+                      )}
+                    </>
+                  )}
+                />
+              ),
+            )}
           </ul>
         </section>
       ))}
diff --git a/apps/web/src/lib/user-profile-view.test.ts b/apps/web/src/lib/user-profile-view.test.ts
index 0843590..0f774c6 100644
--- a/apps/web/src/lib/user-profile-view.test.ts
+++ b/apps/web/src/lib/user-profile-view.test.ts
@@ -3,8 +3,12 @@ import { describe, expect, it } from "vitest";
 import {
   displayLanguageTag,
   displayRegionTag,
+  factSpaceNames,
   filledProfileFields,
   groupUserFacts,
+  toggleFactSpace,
+  userFactDraft,
+  userFactEdit,
 } from "./user-profile-view";
 
 function fact(overrides: Partial<UserFact> & Pick<UserFact, "id">): UserFact {
@@ -74,3 +78,43 @@ describe("user profile view", () => {
     expect(displayRegionTag("not a tag", "en")).toBe("not a tag");
   });
 });
+
+describe("user fact editing", () => {
+  const tea = fact({ id: "tea", value: "Prefers tea", category: "preferences" });
+  const limited = fact({ id: "lin", allSpaces: false, spaceIds: ["space-b", "space-a"] });
+
+  it("sends only what changed, or nothing", () => {
+    expect(userFactEdit(tea, userFactDraft(tea))).toBeNull();
+    expect(userFactEdit(tea, { ...userFactDraft(tea), value: "  Prefers tea " })).toBeNull();
+    expect(
+      userFactEdit(limited, { ...userFactDraft(limited), spaceIds: ["space-a", "space-b"] }),
+    ).toBeNull();
+    expect(
+      userFactEdit(tea, { value: " Prefers green tea ", category: "habits", spaceIds: null }),
+    ).toEqual({ id: "tea", value: "Prefers green tea", category: "habits" });
+    expect(userFactEdit(tea, { ...userFactDraft(tea), spaceIds: ["space-a"] })).toEqual({
+      id: "tea",
+      spaceIds: ["space-a"],
+    });
+    expect(userFactEdit(limited, { ...userFactDraft(limited), spaceIds: null })).toEqual({
+      id: "lin",
+      spaceIds: null,
+    });
+  });
+
+  it("limits a fact to checked spaces and shows it everywhere when none is left", () => {
+    expect(toggleFactSpace(null, "space-a", true)).toEqual(["space-a"]);
+    expect(toggleFactSpace(["space-a"], "space-b", true)).toEqual(["space-a", "space-b"]);
+    expect(toggleFactSpace(["space-a", "space-b"], "space-a", false)).toEqual(["space-b"]);
+    expect(toggleFactSpace(["space-a"], "space-a", false)).toBeNull();
+  });
+
+  it("names the spaces of a limited fact", () => {
+    const spaces = [
+      { id: "space-a", name: "Home" },
+      { id: "space-b", name: "Side project" },
+    ];
+    expect(factSpaceNames(["space-b", "gone"], spaces)).toEqual(["Side project"]);
+    expect(factSpaceNames(null, spaces)).toEqual([]);
+  });
+});
diff --git a/apps/web/src/lib/user-profile-view.ts b/apps/web/src/lib/user-profile-view.ts
index 97877dc..623e9be 100644
--- a/apps/web/src/lib/user-profile-view.ts
+++ b/apps/web/src/lib/user-profile-view.ts
@@ -1,6 +1,15 @@
-import type { UserFact, UserFactCategory, UserProfile } from "@rakazo/contracts";
+import type { UpdateUserProfile, UserFact, UserFactCategory, UserProfile } from "@rakazo/contracts";
 import { USER_FACT_CATEGORIES } from "@rakazo/contracts";
 
+/** What the fact editor holds: null spaces means every space. */
+export interface UserFactDraft {
+  value: string;
+  category: UserFactCategory;
+  spaceIds: string[] | null;
+}
+
+type UserFactEdit = NonNullable<UpdateUserProfile["editFacts"]>[number];
+
 export type ProfileField = "timeZone" | "language" | "locale" | "communicationStyle" | "summary";
 
 const PROFILE_FIELDS: ProfileField[] = [
@@ -75,3 +84,49 @@ export function displayRegionTag(tag: string, uiLocale: string): string {
     return tag;
   }
 }
+
+export function userFactDraft(fact: UserFact): UserFactDraft {
+  return {
+    value: fact.value,
+    category: fact.category,
+    spaceIds: fact.allSpaces ? null : fact.spaceIds,
+  };
+}
+
+/** The `editFacts` entry for what changed in the draft, or null when nothing did. */
+export function userFactEdit(fact: UserFact, draft: UserFactDraft): UserFactEdit | null {
+  const edit: UserFactEdit = { id: fact.id };
+  const value = draft.value.trim();
+  if (value !== fact.value) edit.value = value;
+  if (draft.category !== fact.category) edit.category = draft.category;
+  const before = userFactDraft(fact).spaceIds;
+  const sameSpaces =
+    before === null || draft.spaceIds === null
+      ? before === draft.spaceIds
+      : before.length === draft.spaceIds.length &&
+        draft.spaceIds.every((spaceId) => before.includes(spaceId));
+  if (!sameSpaces) edit.spaceIds = draft.spaceIds;
+  return Object.keys(edit).length > 1 ? edit : null;
+}
+
+/** Checks or unchecks one space; unchecking the last one shows the fact everywhere again. */
+export function toggleFactSpace(
+  spaceIds: string[] | null,
+  spaceId: string,
+  checked: boolean,
+): string[] | null {
+  const current = spaceIds ?? [];
+  const next = checked
+    ? [...current.filter((id) => id !== spaceId), spaceId]
+    : current.filter((id) => id !== spaceId);
+  return next.length > 0 ? next : null;
+}
+
+/** Names of the spaces a limited fact shows in, in the order of `spaces`; unknown ids are skipped. */
+export function factSpaceNames(
+  spaceIds: string[] | null,
+  spaces: ReadonlyArray<{ id: string; name: string }>,
+): string[] {
+  if (!spaceIds) return [];
+  return spaces.filter((space) => spaceIds.includes(space.id)).map((space) => space.name);
+}
diff --git a/packages/db/src/user-profile.postgres.test.ts b/packages/db/src/user-profile.postgres.test.ts
index 03e10b0..d1c218c 100644
--- a/packages/db/src/user-profile.postgres.test.ts
+++ b/packages/db/src/user-profile.postgres.test.ts
@@ -179,6 +179,66 @@ describePostgres("user profile (PostgreSQL)", () => {
     });
   });
 
+  it("edits a fact in place, refusing a wording another fact already has", async () => {
+    const { userId, homeSpaceId } = await newUser();
+    const work = await createSpaceForMember(prisma, {
+      currentSpaceId: homeSpaceId,
+      userId,
+      name: "Work",
+    });
+    const [tea, coffee] = await updateUserProfile(prisma, userId, {
+      addFacts: [
+        { category: "preferences", value: "Prefers tea", source: "user" },
+        { category: "preferences", value: "Drinks coffee at work", source: "conversation" },
+      ],
+    });
+    await prisma.userFact.update({
+      where: { id: tea!.id },
+      data: { embedding: [0.1, 0.2], embeddingModel: "test-embedding" },
+    });
+
+    // Same wording, new category and visibility: the embedding still fits.
+    await updateUserProfile(prisma, userId, {
+      editFacts: [{ id: tea!.id, value: " Prefers tea ", category: "habits", spaceIds: [work.id] }],
+    });
+    expect(await prisma.userFact.findUniqueOrThrow({ where: { id: tea!.id } })).toMatchObject({
+      value: "Prefers tea",
+      category: "habits",
+      allSpaces: false,
+      embedding: [0.1, 0.2],
+      embeddingModel: "test-embedding",
+    });
+    expect(
+      (await getUserProfileState(prisma, userId)).facts.find((fact) => fact.id === tea!.id),
+    ).toMatchObject({ allSpaces: false, spaceIds: [work.id] });
+
+    for (const value of ["“prefers TEA!”", "..."]) {
+      await expect(
+        updateUserProfile(prisma, userId, {
+          editFacts: [
+            { id: coffee!.id, category: "work" },
+            { id: coffee!.id, value },
+          ],
+        }),
+      ).rejects.toBeInstanceOf(InvalidUserFactError);
+    }
+    // The whole update failed, the category change included.
+    expect(await prisma.userFact.findUniqueOrThrow({ where: { id: coffee!.id } })).toMatchObject({
+      value: "Drinks coffee at work",
+      category: "preferences",
+    });
+
+    // A fact may take a wording that an earlier edit in the same update gave up.
+    await updateUserProfile(prisma, userId, {
+      editFacts: [
+        { id: tea!.id, value: "Prefers green tea" },
+        { id: coffee!.id, value: "prefers tea" },
+      ],
+    });
+    const values = (await getUserProfileState(prisma, userId)).facts.map((fact) => fact.value);
+    expect(values.sort()).toEqual(["Prefers green tea", "prefers tea"]);
+  });
+
   it("limits a fact to the user's own spaces", async () => {
     const owner = await newUser();
     const other = await newUser("Grace");
diff --git a/packages/db/src/user-profile.ts b/packages/db/src/user-profile.ts
index c8f80f3..da24418 100644
--- a/packages/db/src/user-profile.ts
+++ b/packages/db/src/user-profile.ts
@@ -250,36 +250,54 @@ async function addFacts(
   return results;
 }
 
-async function editFact(
+/**
+ * Applies the user's fact edits in order. A new wording must still say something and must not
+ * repeat another fact, compared the way new facts are.
+ */
+async function editFacts(
   tx: Prisma.TransactionClient,
   userId: string,
-  edit: UserFactEdit,
+  edits: UserFactEdit[],
 ): Promise<void> {
-  const fact = await tx.userFact.findFirst({
-    where: { id: edit.id, userId },
-    select: { id: true },
+  if (edits.length === 0) return;
+  const facts = await tx.userFact.findMany({
+    where: { userId },
+    select: { id: true, value: true },
   });
-  if (!fact) throw new UserFactNotFoundError();
-  const data: Prisma.UserFactUpdateInput = {};
-  if (edit.category !== undefined) {
-    data.category = edit.category;
-    data.sensitive = isSensitiveUserFactCategory(edit.category);
+  const values = new Map(facts.map((fact) => [fact.id, fact.value]));
+  for (const edit of edits) {
+    const current = values.get(edit.id);
+    if (current === undefined) throw new UserFactNotFoundError();
+    const data: Prisma.UserFactUpdateInput = {};
+    if (edit.category !== undefined) {
+      data.category = edit.category;
+      data.sensitive = isSensitiveUserFactCategory(edit.category);
+    }
+    if (edit.value !== undefined && edit.value.trim() !== current) {
+      const value = edit.value.trim();
+      const key = normalizeUserFactValue(value);
+      if (!key) throw new InvalidUserFactError("Fact is empty");
+      for (const [id, other] of values) {
+        if (id !== edit.id && normalizeUserFactValue(other) === key) {
+          throw new InvalidUserFactError("This fact already exists");
+        }
+      }
+      values.set(edit.id, value);
+      data.value = value;
+      // The stored embedding described the old wording.
+      data.embedding = [];
+      data.embeddingModel = null;
+    }
+    if (edit.spaceIds !== undefined) {
+      const spaces = visibleSpacesOf(edit.spaceIds);
+      data.allSpaces = spaces === null;
+      data.visibleSpaces = {
+        deleteMany: {},
+        ...(spaces ? { create: spaces.map((spaceId) => ({ spaceId })) } : {}),
+      };
+    }
+    if (Object.keys(data).length > 0) await tx.userFact.update({ where: { id: edit.id }, data });
   }
-  if (edit.value !== undefined) {
-    data.value = edit.value.trim();
-    // The stored embedding described the old wording.
-    data.embedding = [];
-    data.embeddingModel = null;
-  }
-  if (edit.spaceIds !== undefined) {
-    const spaces = visibleSpacesOf(edit.spaceIds);
-    data.allSpaces = spaces === null;
-    data.visibleSpaces = {
-      deleteMany: {},
-      ...(spaces ? { create: spaces.map((spaceId) => ({ spaceId })) } : {}),
-    };
-  }
-  await tx.userFact.update({ where: { id: fact.id }, data });
 }
 
 async function confirmFacts(
@@ -341,7 +359,7 @@ export async function updateUserProfile(
       });
     }
     const added = await addFacts(tx, userId, update.addFacts ?? []);
-    for (const edit of update.editFacts ?? []) await editFact(tx, userId, edit);
+    await editFacts(tx, userId, update.editFacts ?? []);
     await confirmFacts(tx, userId, update.confirmFactIds ?? []);
     return added;
   });
diff --git a/packages/testkit/src/user-profile.postgres.test.ts b/packages/testkit/src/user-profile.postgres.test.ts
index 11b3ede..462e461 100644
--- a/packages/testkit/src/user-profile.postgres.test.ts
+++ b/packages/testkit/src/user-profile.postgres.test.ts
@@ -161,6 +161,47 @@ describeWithDatabase("user profile through the API and the main bot", () => {
     expect(forgotten.facts).toEqual([]);
     expect(forgotten.profile).toMatchObject({ timeZone: null, language: null, summary: "" });
   });
+
+  it("edits a fact's wording, category and spaces for its owner only", async () => {
+    const cookie = await signup(app, `profile-edit-${stamp}@rakazo.test`, "Profile Edit");
+    const intruder = await signup(app, `profile-edit-other-${stamp}@rakazo.test`, "Intruder");
+    const side = await rpc<{ id: string }>(app, cookie, "spaces/create", { name: "Side" });
+    const elsewhere = await rpc<{ id: string }>(app, intruder, "spaces/create", { name: "Theirs" });
+    const added = await rpc<UserProfileState>(app, cookie, "profile/update", {
+      addFacts: [
+        { category: "preferences", value: "Prefers tea" },
+        { category: "work", value: "Works late" },
+      ],
+    });
+    const tea = added.facts.find((fact) => fact.value === "Prefers tea")!;
+
+    const edited = await rpc<UserProfileState>(app, cookie, "profile/update", {
+      editFacts: [
+        { id: tea.id, value: "Prefers green tea", category: "habits", spaceIds: [side.id] },
+      ],
+    });
+    expect(edited.facts.find((fact) => fact.id === tea.id)).toMatchObject({
+      value: "Prefers green tea",
+      category: "habits",
+      allSpaces: false,
+      spaceIds: [side.id],
+    });
+
+    const edit = (body: unknown, who = cookie) => raw(app, who, "profile/update", body);
+    expect((await edit({ editFacts: [{ id: tea.id, value: "works late!" }] })).status).toBe(400);
+    expect((await edit({ editFacts: [{ id: tea.id, spaceIds: [elsewhere.id] }] })).status).toBe(
+      400,
+    );
+    expect((await edit({ editFacts: [{ id: tea.id, value: "Stolen" }] }, intruder)).status).toBe(
+      404,
+    );
+    expect((await rpc<UserProfileState>(app, intruder, "profile/get")).facts).toEqual([]);
+    expect(
+      (await rpc<UserProfileState>(app, cookie, "profile/get")).facts.find(
+        (fact) => fact.id === tea.id,
+      ),
+    ).toMatchObject({ value: "Prefers green tea", spaceIds: [side.id] });
+  });
 });
 
 async function signup(app: App, email: string, name: string) {