feat: add memory.patch, trim memory.get, unify the memory write path

memory.get no longer returns the embedding and content_tsv ---------------------------------------------------------- It used a bare select() and returned the raw DB row, while memory.list and memory.search already projected an explicit 9-field shape. On a ~13k-char memory those two internal columns were 55% of the response and pushed it past the MCP tool-output cap, so large memories could not be fetched inline at all. memory.get now returns the same 9 fields as its siblings; user_id is still selected for the authorization check and stripped before responding. memory.patch ------------ memory.update only accepts full replacement, so adding one line to a large document meant resending the whole document — expensive enough that edits were being skipped rather than risk silently truncating shared team documents. memory.patch replaces one exact occurrence of old_string. An absent or ambiguous match is an error, never a silent no-op and never an arbitrary pick; that refusal is what makes the operation safe to hand to an agent. The semantics live in lib/memory-patch.ts as a pure function, free of DB and auth, so both surfaces share them. Shared mutation layer --------------------- The MCP tools and the Web UI Server Actions each reimplemented authorize -> mutate -> re-embed -> CAS -> audit, and had drifted. Both now route through lib/memory-mutations.ts. BEHAVIOUR CHANGE: memory.delete over MCP skipped the project ACL whenever the caller authored the row, so a memory written while a share was rw stayed deletable by its author after an owner downgraded that share to ro. memory.update and the whole Web UI always checked. Authoring a row now grants no standing write privilege on any path. The one deliberate difference between the surfaces is injected as a ProjectResolver: MCP refuses an unknown project key so an agent cannot spawn near-miss projects off a typo, while the Web UI creates one because a person typing a name into a form means to. Tests and lint -------------- Adds vitest. The integration tests run against a real Postgres rather than a mocked DB. The embedder sidecar is the only stub and it is deterministic per-text, so re-embedding is verified by asserting the stored vector actually changed rather than that a mock was called. One test pins that content_tsv is a generated column and therefore cannot rot after a patch — only the embedding needs an explicit recompute. pnpm lint previously dropped into an interactive `next lint` setup prompt and exited 1; ESLint had never been configured here. Replaced with the ESLint CLI and a flat config bridging eslint-config-next through FlatCompat. Clean at --max-warnings=0. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
2026-08-11 14:58:11 -07:00
parent d9306884d3
commit c3bbea5134
20 changed files with 2435 additions and 527 deletions
@@ -0,0 +1,258 @@
+import { afterAll, beforeAll, beforeEach, describe, expect, test, vi } from "vitest";
+
+/**
+ * Integration tests for memory.get and memory.patch against a REAL
+ * Postgres (pgvector). See CONTRIBUTING/README for spinning up the test
+ * database; without it these tests fail to connect rather than silently
+ * passing.
+ *
+ * The embedder sidecar is the one thing stubbed — it's an external HTTP
+ * service running an ML model. The stub is deterministic per-text, which
+ * lets the re-embedding test assert on the STORED VECTOR CHANGING (real
+ * DB state) rather than on "was the mock called".
+ */
+vi.mock("@/lib/embedder", () => ({
+  embedText: async (text: string) => {
+    // Deterministic pseudo-vector: distinct texts produce distinct vectors.
+    let h = 0;
+    for (let i = 0; i < text.length; i++) h = (h * 31 + text.charCodeAt(i)) | 0;
+    return Array.from({ length: 384 }, (_, i) => ((h + i * 7919) % 1000) / 1000);
+  },
+  embedTexts: async (texts: string[]) => texts.map(() => Array(384).fill(0.1)),
+  embedderReady: async () => true,
+  EmbedderError: class extends Error {},
+}));
+
+const { db, pg } = await import("@/lib/db/client");
+const { memories, projects, users } = await import("@/lib/db/schema");
+const { toolMap } = await import("@/lib/mcp/tools");
+const { eq } = await import("drizzle-orm");
+type UserContext = import("@/lib/mcp/context").UserContext;
+
+const ORIGINAL = [
+  "# Roadmap",
+  "",
+  "## RECENTLY SHIPPED",
+  "- v1.0 initial release",
+  "",
+  "## IN PROGRESS",
+  "- patch primitive",
+  "",
+].join("\n");
+
+let userId: string;
+let projectId: string;
+let memoryId: string;
+let ctx: UserContext;
+
+async function seedMemory(content = ORIGINAL): Promise<string> {
+  const row = await db
+    .insert(memories)
+    .values({
+      userId,
+      projectId,
+      scope: "project",
+      content,
+      tags: ["roadmap"],
+      embedding: Array(384).fill(0.5),
+    })
+    .returning({ id: memories.id });
+  return row[0]!.id;
+}
+
+async function readContent(id: string): Promise<string> {
+  const r = await db
+    .select({ content: memories.content })
+    .from(memories)
+    .where(eq(memories.id, id));
+  return r[0]!.content;
+}
+
+beforeAll(async () => {
+  const u = await db
+    .insert(users)
+    .values({ oidcSub: "test-sub", oidcIss: "http://test", email: "t@example.com" })
+    .onConflictDoNothing()
+    .returning({ id: users.id });
+  userId =
+    u[0]?.id ??
+    (await db.select({ id: users.id }).from(users).limit(1))[0]!.id;
+
+  const p = await db
+    .insert(projects)
+    .values({ userId, key: "test-project", displayName: "Test Project" })
+    .onConflictDoNothing()
+    .returning({ id: projects.id });
+  projectId =
+    p[0]?.id ??
+    (await db.select({ id: projects.id }).from(projects).limit(1))[0]!.id;
+
+  ctx = {
+    userId,
+    sub: "test-sub",
+    iss: "http://test",
+    email: null,
+    name: null,
+    groups: [],
+  };
+});
+
+beforeEach(async () => {
+  memoryId = await seedMemory();
+});
+
+afterAll(async () => {
+  await db.delete(memories);
+  await pg.end();
+});
+
+describe("memory.get response shape (P1)", () => {
+  test("does not leak the embedding or the tsvector to the caller", async () => {
+    const res = await toolMap["memory.get"]!.handler({ id: memoryId }, ctx);
+    const fields = Object.keys(res.structuredContent as object);
+
+    expect(fields).not.toContain("embedding");
+    expect(fields).not.toContain("contentTsv");
+  });
+
+  test("returns exactly the same 9 fields as memory.list", async () => {
+    const res = await toolMap["memory.get"]!.handler({ id: memoryId }, ctx);
+    const fields = Object.keys(res.structuredContent as object).sort();
+
+    expect(fields).toEqual(
+      [
+        "content",
+        "createdAt",
+        "id",
+        "lastEditedBy",
+        "projectId",
+        "scope",
+        "tags",
+        "updatedAt",
+        "version",
+      ].sort(),
+    );
+  });
+
+  test("still returns the full content", async () => {
+    const res = await toolMap["memory.get"]!.handler({ id: memoryId }, ctx);
+    expect((res.structuredContent as { content: string }).content).toBe(ORIGINAL);
+  });
+});
+
+describe("memory.patch (P2)", () => {
+  test("applies a unique patch and increments version by exactly 1", async () => {
+    const before = await db
+      .select({ version: memories.version })
+      .from(memories)
+      .where(eq(memories.id, memoryId));
+
+    const res = await toolMap["memory.patch"]!.handler(
+      {
+        id: memoryId,
+        old_string: "## RECENTLY SHIPPED",
+        new_string: "## RECENTLY SHIPPED\n- v1.1 patch primitive",
+      },
+      ctx,
+    );
+
+    expect(res.isError).toBeFalsy();
+    const after = res.structuredContent as { version: number };
+    expect(after.version).toBe(before[0]!.version + 1);
+    expect(await readContent(memoryId)).toContain("- v1.1 patch primitive");
+    // The rest of the document survived.
+    expect(await readContent(memoryId)).toContain("- v1.0 initial release");
+    expect(await readContent(memoryId)).toContain("## IN PROGRESS");
+  });
+
+  test("refuses an absent old_string and leaves content byte-identical", async () => {
+    const res = await toolMap["memory.patch"]!.handler(
+      { id: memoryId, old_string: "## NOT PRESENT", new_string: "x" },
+      ctx,
+    );
+
+    expect(res.isError).toBe(true);
+    expect(await readContent(memoryId)).toBe(ORIGINAL);
+  });
+
+  test("refuses an ambiguous old_string, naming the count, leaving content unchanged", async () => {
+    const id = await seedMemory("alpha\nalpha\nbeta\n");
+
+    const res = await toolMap["memory.patch"]!.handler(
+      { id, old_string: "alpha", new_string: "gamma" },
+      ctx,
+    );
+
+    expect(res.isError).toBe(true);
+    expect(res.content[0]!.text).toMatch(/2/);
+    expect(await readContent(id)).toBe("alpha\nalpha\nbeta\n");
+  });
+
+  test("refuses a stale version and leaves content unchanged", async () => {
+    const current = await db
+      .select({ version: memories.version })
+      .from(memories)
+      .where(eq(memories.id, memoryId));
+
+    const res = await toolMap["memory.patch"]!.handler(
+      {
+        id: memoryId,
+        old_string: "## IN PROGRESS",
+        new_string: "## DONE",
+        version: current[0]!.version + 99,
+      },
+      ctx,
+    );
+
+    expect(res.isError).toBe(true);
+    expect(await readContent(memoryId)).toBe(ORIGINAL);
+  });
+
+  test("rejects a patch that would push content past the 64,000-char limit", async () => {
+    const id = await seedMemory("A".repeat(63_950) + "ANCHOR");
+
+    const res = await toolMap["memory.patch"]!.handler(
+      { id, old_string: "ANCHOR", new_string: "B".repeat(100) },
+      ctx,
+    );
+
+    expect(res.isError).toBe(true);
+    expect(await readContent(id)).toBe("A".repeat(63_950) + "ANCHOR");
+  });
+
+  test("re-embeds: the stored vector changes after a patch", async () => {
+    const before = await pg<{ embedding: string }[]>`
+      SELECT embedding::text AS embedding FROM memories WHERE id = ${memoryId}
+    `;
+
+    await toolMap["memory.patch"]!.handler(
+      { id: memoryId, old_string: "- patch primitive", new_string: "- shipped it" },
+      ctx,
+    );
+
+    const after = await pg<{ embedding: string }[]>`
+      SELECT embedding::text AS embedding FROM memories WHERE id = ${memoryId}
+    `;
+
+    expect(after[0]!.embedding).not.toBe(before[0]!.embedding);
+  });
+
+  test("full-text index updates itself, because content_tsv is a generated column", async () => {
+    // This is the claim that a patch cannot rot FTS. Postgres maintains
+    // content_tsv; only the embedding needs an explicit recompute.
+    await toolMap["memory.patch"]!.handler(
+      {
+        id: memoryId,
+        old_string: "- patch primitive",
+        new_string: "- kumquat marmalade",
+      },
+      ctx,
+    );
+
+    const hit = await pg<{ n: number }[]>`
+      SELECT count(*)::int AS n FROM memories
+      WHERE id = ${memoryId} AND content_tsv @@ plainto_tsquery('english', 'kumquat')
+    `;
+    expect(hit[0]!.n).toBe(1);
+  });
+});
@@ -0,0 +1,244 @@
+import { afterAll, beforeAll, beforeEach, describe, expect, test, vi } from "vitest";
+
+/**
+ * Integration cover for the memory MUTATION paths (write / update / delete)
+ * against a real Postgres. These exist mainly as a safety net for the
+ * shared-mutation refactor: the MCP tools and the Web UI Server Actions
+ * used to reimplement the same authorize → CAS → re-embed → audit sequence
+ * separately, and these assertions pin the behaviour that must survive
+ * being pulled into one place.
+ */
+vi.mock("@/lib/embedder", () => ({
+  embedText: async (text: string) => {
+    let h = 0;
+    for (let i = 0; i < text.length; i++) h = (h * 31 + text.charCodeAt(i)) | 0;
+    return Array.from({ length: 384 }, (_, i) => ((h + i * 7919) % 1000) / 1000);
+  },
+  embedTexts: async (texts: string[]) => texts.map(() => Array(384).fill(0.1)),
+  embedderReady: async () => true,
+  EmbedderError: class extends Error {},
+}));
+
+const { db, pg } = await import("@/lib/db/client");
+const { memories, projects, users, groups, userGroups, projectShares } = await import(
+  "@/lib/db/schema"
+);
+const { toolMap } = await import("@/lib/mcp/tools");
+const { eq } = await import("drizzle-orm");
+type UserContext = import("@/lib/mcp/context").UserContext;
+
+const ISS = "http://test";
+
+let author: UserContext;
+let projectOwnerId: string;
+let ownProjectId: string;
+let sharedProjectId: string;
+let sharedGroupId: string;
+
+function ctxFor(userId: string, sub: string, groupNames: string[] = []): UserContext {
+  return { userId, sub, iss: ISS, email: null, name: null, groups: groupNames };
+}
+
+async function upsertUser(sub: string): Promise<string> {
+  const r = await db
+    .insert(users)
+    .values({ oidcSub: sub, oidcIss: ISS })
+    .onConflictDoUpdate({ target: [users.oidcIss, users.oidcSub], set: { oidcSub: sub } })
+    .returning({ id: users.id });
+  return r[0]!.id;
+}
+
+async function seedMemory(
+  userId: string,
+  projectId: string | null,
+  content = "seed content",
+): Promise<string> {
+  const r = await db
+    .insert(memories)
+    .values({
+      userId,
+      projectId,
+      scope: projectId ? "project" : "user",
+      content,
+      tags: [],
+      embedding: Array(384).fill(0.5),
+      lastEditedBy: userId,
+    })
+    .returning({ id: memories.id });
+  return r[0]!.id;
+}
+
+async function setShareAccess(access: "ro" | "rw") {
+  await db
+    .insert(projectShares)
+    .values({ projectId: sharedProjectId, groupId: sharedGroupId, access })
+    .onConflictDoUpdate({
+      target: [projectShares.projectId, projectShares.groupId],
+      set: { access },
+    });
+}
+
+async function isDeleted(id: string): Promise<boolean> {
+  const r = await db
+    .select({ deletedAt: memories.deletedAt })
+    .from(memories)
+    .where(eq(memories.id, id));
+  return r[0]!.deletedAt !== null;
+}
+
+beforeAll(async () => {
+  const authorId = await upsertUser("author-sub");
+  projectOwnerId = await upsertUser("owner-sub");
+
+  const own = await db
+    .insert(projects)
+    .values({ userId: authorId, key: "author-own", displayName: "Author Own" })
+    .onConflictDoNothing()
+    .returning({ id: projects.id });
+  ownProjectId =
+    own[0]?.id ??
+    (
+      await db
+        .select({ id: projects.id })
+        .from(projects)
+        .where(eq(projects.key, "author-own"))
+    )[0]!.id;
+
+  const shared = await db
+    .insert(projects)
+    .values({ userId: projectOwnerId, key: "team-shared", displayName: "Team Shared" })
+    .onConflictDoNothing()
+    .returning({ id: projects.id });
+  sharedProjectId =
+    shared[0]?.id ??
+    (
+      await db
+        .select({ id: projects.id })
+        .from(projects)
+        .where(eq(projects.key, "team-shared"))
+    )[0]!.id;
+
+  const g = await db
+    .insert(groups)
+    .values({ oidcIss: ISS, name: "team" })
+    .onConflictDoNothing()
+    .returning({ id: groups.id });
+  sharedGroupId =
+    g[0]?.id ??
+    (await db.select({ id: groups.id }).from(groups).where(eq(groups.name, "team")))[0]!
+      .id;
+
+  await db
+    .insert(userGroups)
+    .values({ userId: authorId, groupId: sharedGroupId })
+    .onConflictDoNothing();
+
+  author = ctxFor(authorId, "author-sub", ["team"]);
+});
+
+beforeEach(async () => {
+  await db.delete(memories);
+  await setShareAccess("rw");
+});
+
+afterAll(async () => {
+  await db.delete(memories);
+  await pg.end();
+});
+
+describe("memory.write", () => {
+  test("writes into a project the caller owns", async () => {
+    const res = await toolMap["memory.write"]!.handler(
+      { content: "hello", scope: "project", project: "author-own" },
+      author,
+    );
+    expect(res.isError).toBeFalsy();
+  });
+
+  test("refuses an unknown project rather than creating one", async () => {
+    const res = await toolMap["memory.write"]!.handler(
+      { content: "hello", scope: "project", project: "does-not-exist" },
+      author,
+    );
+
+    expect(res.isError).toBe(true);
+    expect(res.content[0]!.text).toMatch(/project\.identify/);
+  });
+});
+
+describe("memory.update", () => {
+  test("updates content and increments version", async () => {
+    const id = await seedMemory(author.userId, ownProjectId);
+    const before = await db
+      .select({ version: memories.version })
+      .from(memories)
+      .where(eq(memories.id, id));
+
+    const res = await toolMap["memory.update"]!.handler(
+      { id, content: "revised content" },
+      author,
+    );
+
+    expect(res.isError).toBeFalsy();
+    expect((res.structuredContent as { version: number }).version).toBe(
+      before[0]!.version + 1,
+    );
+  });
+
+  test("refuses a stale version", async () => {
+    const id = await seedMemory(author.userId, ownProjectId);
+
+    const res = await toolMap["memory.update"]!.handler(
+      { id, content: "revised", version: 99 },
+      author,
+    );
+
+    expect(res.isError).toBe(true);
+  });
+
+  test("denies updating a memory in a project shared read-only", async () => {
+    const id = await seedMemory(author.userId, sharedProjectId);
+    await setShareAccess("ro");
+
+    const res = await toolMap["memory.update"]!.handler(
+      { id, content: "sneaky edit" },
+      author,
+    );
+
+    expect(res.isError).toBe(true);
+  });
+});
+
+describe("memory.delete authorization", () => {
+  test("allows deleting a memory in a project shared read-write", async () => {
+    const id = await seedMemory(author.userId, sharedProjectId);
+
+    const res = await toolMap["memory.delete"]!.handler({ id }, author);
+
+    expect(res.isError).toBeFalsy();
+    expect(await isDeleted(id)).toBe(true);
+  });
+
+  test("denies deleting a memory in a project shared read-only, even to its author", async () => {
+    // The realistic path here: the memory was written while the share was
+    // rw, then an owner downgraded the group to ro. Authoring the row must
+    // not grant a standing write privilege the project ACL has revoked —
+    // memory.update already refuses this, and delete must agree.
+    const id = await seedMemory(author.userId, sharedProjectId);
+    await setShareAccess("ro");
+
+    const res = await toolMap["memory.delete"]!.handler({ id }, author);
+
+    expect(res.isError).toBe(true);
+    expect(await isDeleted(id)).toBe(false);
+  });
+
+  test("denies deleting another user's user-scope memory", async () => {
+    const id = await seedMemory(projectOwnerId, null);
+
+    const res = await toolMap["memory.delete"]!.handler({ id }, author);
+
+    expect(res.isError).toBe(true);
+    expect(await isDeleted(id)).toBe(false);
+  });
+});
@@ -11,6 +11,7 @@ import {
  MemoryIdInput,
  MemoryDeleteInput,
  MemoryListInput,
+  MemoryPatchInput,
  MemorySearchInput,
  MemoryUpdateInput,
  MemoryWriteInput,
@@ -20,20 +21,22 @@ import {
  SnippetListInput,
  SnippetDeleteInput,
 } from "@shared-memory/schemas";
-import { embedText } from "@/lib/embedder";
 import { searchMemories } from "@/lib/memories";
+import {
+  createMemory,
+  patchMemory,
+  softDeleteMemory,
+  updateMemory,
+  type Actor,
+  type ProjectResolver,
+} from "@/lib/memory-mutations";
 import {
  getSnippet,
  putSnippet,
  listSnippets,
  softDeleteSnippet,
 } from "@/lib/snippets";
-import {
-  CONCURRENT_EDIT_ERROR,
-  canWriteProject,
-  getProjectAccess,
-  readableProjectIds,
-} from "@/lib/access";
+import { getProjectAccess, readableProjectIds } from "@/lib/access";
 import type { UserContext } from "./context";

 /**
@@ -151,6 +154,27 @@ function withDefaultProject(
  return { ...obj, project: ctx.defaultProjectKey };
 }

+/** Adapt an MCP request context to the shared mutation layer. */
+function mcpActor(ctx: UserContext): Actor {
+  return { userId: ctx.userId, groups: ctx.groups, via: "mcp" };
+}
+
+/**
+ * Project resolution for MCP writes. Unlike the Web UI, the MCP surface
+ * never auto-creates a project — an unknown key is an error telling the
+ * caller to run project.identify first, which keeps agents from silently
+ * spawning near-miss projects off a typo'd key.
+ */
+function mcpProjectResolver(ctx: UserContext): ProjectResolver {
+  return async (key: string) => {
+    const id = await resolveProjectId(ctx, key);
+    if (!id) {
+      return { ok: false, error: `unknown project '${key}'; call project.identify first` };
+    }
+    return { ok: true, value: id };
+  };
+}
+
 // ---------- tools ----------

 const projectIdentify: ToolDef = {
@@ -373,55 +397,18 @@ const memoryWrite: ToolDef = {
    const parsed = MemoryWriteInput.safeParse(withDefaultProject(args, ctx));
    if (!parsed.success) return err(parsed.error.message);

-    const scope = parsed.data.scope;
-    let projectId: string | null = null;
-    let projectKey: string | undefined = undefined;
-    if (scope === "project") {
-      projectKey = projectKeyOrDefault(ctx, parsed.data.project);
-      if (!projectKey) {
-        return err("scope=project requires `project` key (or X-Project-Key header)");
-      }
-      projectId = await resolveProjectId(ctx, projectKey);
-      if (!projectId) {
-        return err(`unknown project '${projectKey}'; call project.identify first`);
-      }
-      // Authorize write. Owner always allowed; otherwise require rw.
-      const allowed = await canWriteProject(ctx.userId, ctx.groups, projectId);
-      if (!allowed) {
-        return err(`no write access to project '${projectKey}'`);
-      }
+    // Fold the X-Project-Key fallback in before the shared path sees it.
+    const input = {
+      ...parsed.data,
+      project: projectKeyOrDefault(ctx, parsed.data.project),
+    };
+    if (input.scope === "project" && !input.project) {
+      return err("scope=project requires `project` key (or X-Project-Key header)");
    }

-    // Embed inline so the new memory is searchable immediately. Slower
-    // writes (~50–150 ms) are an acceptable price for that guarantee; if
-    // embedder pressure ever forces an async path, only this section
-    // needs to change.
-    const embedding = await embedText(parsed.data.content);
-
-    const inserted = await db
-      .insert(memories)
-      .values({
-        userId: ctx.userId,
-        projectId,
-        scope,
-        content: parsed.data.content,
-        tags: parsed.data.tags ?? [],
-        embedding,
-        lastEditedBy: ctx.userId,
-      })
-      .returning({ id: memories.id, createdAt: memories.createdAt });
-
-    const m = inserted[0]!;
-    await db.insert(auditLog).values({
-      userId: ctx.userId,
-      actor: "mcp",
-      action: "memory.write",
-      entityType: "memory",
-      entityId: m.id,
-      payload: { scope, projectKey: projectKey ?? null, tags: parsed.data.tags ?? [] },
-    });
-
-    return ok({ id: m.id, createdAt: m.createdAt }, `wrote memory ${m.id}`);
+    const res = await createMemory(mcpActor(ctx), input, mcpProjectResolver(ctx));
+    if (!res.ok) return err(res.error);
+    return ok(res.value, `wrote memory ${res.value.id}`);
  },
 };

@@ -508,8 +495,28 @@ const memoryGet: ToolDef = {
    const parsed = MemoryIdInput.safeParse(args);
    if (!parsed.success) return err(parsed.error.message);

+    // Project explicitly rather than `select()`-ing the raw row. The
+    // table carries `embedding` (384 floats) and `content_tsv` (the full
+    // lexeme index, which outgrows `content` itself on large memories) —
+    // both are Postgres retrieval internals that no MCP client can use,
+    // and together they were the majority of every response. Returning
+    // them also pushed large memories past the tool-output cap. This is
+    // the same 9-field shape memory.list and memory.search return.
    const row = await db
-      .select()
+      .select({
+        id: memories.id,
+        scope: memories.scope,
+        projectId: memories.projectId,
+        content: memories.content,
+        tags: memories.tags,
+        version: memories.version,
+        lastEditedBy: memories.lastEditedBy,
+        createdAt: memories.createdAt,
+        updatedAt: memories.updatedAt,
+        // Needed for the authorization check below; stripped before the
+        // response so the payload matches list/search exactly.
+        userId: memories.userId,
+      })
      .from(memories)
      .where(and(eq(memories.id, parsed.data.id), isNull(memories.deletedAt)))
      .limit(1);
@@ -518,8 +525,8 @@ const memoryGet: ToolDef = {

    // Authorize read: own row, OR project-scope row in an accessible
    // project. Anything else looks "not found" to the caller.
-    const m = row[0];
-    if (m.userId !== ctx.userId) {
+    const { userId, ...m } = row[0];
+    if (userId !== ctx.userId) {
      if (!m.projectId) return err("not found");
      const access = await getProjectAccess(ctx.userId, ctx.groups, m.projectId);
      if (access === null) return err("not found");
@@ -550,57 +557,9 @@ const memoryDelete: ToolDef = {
    const parsed = MemoryDeleteInput.safeParse(args);
    if (!parsed.success) return err(parsed.error.message);

-    // Look up the row first to authorize and capture its current version
-    // for the CAS. Shared-project writes need a per-project access check.
-    const target = await db
-      .select({
-        id: memories.id,
-        userId: memories.userId,
-        projectId: memories.projectId,
-        scope: memories.scope,
-        version: memories.version,
-      })
-      .from(memories)
-      .where(and(eq(memories.id, parsed.data.id), isNull(memories.deletedAt)))
-      .limit(1);
-    const m = target[0];
-    if (!m) return err("not found");
-
-    if (m.userId !== ctx.userId) {
-      // Not the owner. User-scope memories can only be deleted by their
-      // owner; project-scope require rw access on the project.
-      if (m.scope === "user" || !m.projectId) return err("not found");
-      const allowed = await canWriteProject(ctx.userId, ctx.groups, m.projectId);
-      if (!allowed) return err("no write access to this project");
-    }
-
-    // Optimistic-lock CAS: pin to the caller-supplied version when given,
-    // else the version we just read in this handler. The 0-row response
-    // tells us a peer raced us.
-    const expectedVersion = parsed.data.version ?? m.version;
-    const updated = await db
-      .update(memories)
-      .set({ deletedAt: new Date(), lastEditedBy: ctx.userId })
-      .where(
-        and(
-          eq(memories.id, parsed.data.id),
-          eq(memories.version, expectedVersion),
-          isNull(memories.deletedAt),
-        ),
-      )
-      .returning({ id: memories.id });
-
-    if (!updated[0]) return err(CONCURRENT_EDIT_ERROR);
-
-    await db.insert(auditLog).values({
-      userId: ctx.userId,
-      actor: "mcp",
-      action: "memory.delete",
-      entityType: "memory",
-      entityId: updated[0].id,
-    });
-
-    return ok({ id: updated[0].id, deleted: true }, `deleted memory ${updated[0].id}`);
+    const res = await softDeleteMemory(mcpActor(ctx), parsed.data);
+    if (!res.ok) return err(res.error);
+    return ok({ id: res.value.id, deleted: true }, `deleted memory ${res.value.id}`);
  },
 };

@@ -638,124 +597,51 @@ const memoryUpdate: ToolDef = {
    const parsed = MemoryUpdateInput.safeParse(withDefaultProject(args, ctx));
    if (!parsed.success) return err(parsed.error.message);

-    const existingRows = await db
-      .select({
-        id: memories.id,
-        content: memories.content,
-        scope: memories.scope,
-        projectId: memories.projectId,
-        projectKey: projects.key,
-        version: memories.version,
-        userId: memories.userId,
-      })
-      .from(memories)
-      .leftJoin(projects, eq(memories.projectId, projects.id))
-      .where(and(eq(memories.id, parsed.data.id), isNull(memories.deletedAt)))
-      .limit(1);
-    const existing = existingRows[0];
-    if (!existing) return err("not found");
+    const res = await updateMemory(mcpActor(ctx), parsed.data, mcpProjectResolver(ctx));
+    if (!res.ok) return err(res.error);
+    return ok(res.value, `updated memory ${res.value.id}`);
+  },
+};

-    // Authorize write.
-    if (existing.scope === "user") {
-      if (existing.userId !== ctx.userId) return err("not found");
-    } else if (existing.projectId) {
-      const allowed = await canWriteProject(ctx.userId, ctx.groups, existing.projectId);
-      if (!allowed) return err("no write access to this project");
-    }
+const memoryPatch: ToolDef = {
+  name: "memory.patch",
+  description:
+    "Replace one exact snippet of a memory's content, leaving the rest untouched — the same mental model as editing a file. Use this INSTEAD of memory.update whenever you're making a small edit to a large memory: adding an entry under a heading, correcting a line, updating a status. memory.update requires you to resend the entire document, which risks silently dropping content you didn't mean to touch; memory.patch only needs the fragment you're changing. `old_string` must appear EXACTLY once — if it's missing or ambiguous the call fails and nothing is changed, so include enough surrounding context to make it unique. Pass an empty `new_string` to delete the matched text. Re-embeds automatically, preserves the memory's id, and accepts `version` for the same concurrent-edit protection as memory.update.",
+  inputSchema: {
+    type: "object",
+    properties: {
+      id: { type: "string", format: "uuid" },
+      old_string: {
+        type: "string",
+        description:
+          "The exact text to replace. Must occur exactly once in the memory's content — include surrounding lines if the fragment alone would be ambiguous.",
+      },
+      new_string: {
+        type: "string",
+        description:
+          "The replacement text. May be empty to delete the matched text (the memory itself may not be left empty).",
+      },
+      version: {
+        type: "integer",
+        minimum: 0,
+        description:
+          "Optimistic-locking token from memory.get / memory.list. When supplied, the patch is rejected if the row was edited by someone else since you read it.",
+      },
+    },
+    required: ["id", "old_string", "new_string"],
+  },
+  async handler(args, ctx) {
+    const parsed = MemoryPatchInput.safeParse(args);
+    if (!parsed.success) return err(parsed.error.message);

-    const update: Record<string, unknown> = {
-      updatedAt: new Date(),
-      lastEditedBy: ctx.userId,
-      version: existing.version + 1,
-    };
-    if (parsed.data.tags !== undefined) update.tags = parsed.data.tags;
-    if (parsed.data.content !== undefined && parsed.data.content !== existing.content) {
-      update.content = parsed.data.content;
-      update.embedding = await embedText(parsed.data.content);
-    }
+    const res = await patchMemory(mcpActor(ctx), parsed.data);
+    if (!res.ok) return err(res.error);

-    let scopeChanged = false;
-    let projectChanged = false;
-    let newProjectKey: string | null = existing.projectKey ?? null;
-
-    if (parsed.data.scope !== undefined) {
-      if (parsed.data.scope === "user") {
-        if (existing.scope !== "user") {
-          update.scope = "user";
-          scopeChanged = true;
-        }
-        if (existing.projectId !== null) {
-          update.projectId = null;
-          projectChanged = true;
-          newProjectKey = null;
-        }
-      } else {
-        // scope === 'project' — schema refine guarantees `project` is set.
-        const projectKey = parsed.data.project!;
-        const projectId = await resolveProjectId(ctx, projectKey);
-        if (!projectId) {
-          return err(`unknown project '${projectKey}'; call project.identify first`);
-        }
-        // Moving INTO a project requires write access there.
-        const allowedTarget = await canWriteProject(ctx.userId, ctx.groups, projectId);
-        if (!allowedTarget) {
-          return err(`no write access to project '${projectKey}'`);
-        }
-        if (existing.scope !== "project") {
-          update.scope = "project";
-          scopeChanged = true;
-        }
-        if (existing.projectId !== projectId) {
-          update.projectId = projectId;
-          projectChanged = true;
-          newProjectKey = projectKey;
-        }
-      }
-    }
-
-    const expectedVersion = parsed.data.version ?? existing.version;
-    const updated = await db
-      .update(memories)
-      .set(update)
-      .where(
-        and(
-          eq(memories.id, parsed.data.id),
-          eq(memories.version, expectedVersion),
-        ),
-      )
-      .returning({
-        id: memories.id,
-        updatedAt: memories.updatedAt,
-        version: memories.version,
-      });
-
-    if (!updated[0]) return err(CONCURRENT_EDIT_ERROR);
-
-    const auditFields = Object.keys(update).filter(
-      (k) => k !== "updatedAt" && k !== "version" && k !== "lastEditedBy",
+    const { id, delta, contentLength } = res.value;
+    return ok(
+      res.value,
+      `patched memory ${id} (${delta >= 0 ? "+" : ""}${delta} chars, now ${contentLength})`,
    );
-    const auditPayload: Record<string, unknown> = { fields: auditFields };
-    if (scopeChanged || projectChanged) {
-      auditPayload.scope = {
-        from: existing.scope,
-        to: update.scope ?? existing.scope,
-      };
-      auditPayload.projectKey = {
-        from: existing.projectKey ?? null,
-        to: newProjectKey,
-      };
-    }
-
-    await db.insert(auditLog).values({
-      userId: ctx.userId,
-      actor: "mcp",
-      action: "memory.update",
-      entityType: "memory",
-      entityId: updated[0]!.id,
-      payload: auditPayload,
-    });
-
-    return ok(updated[0]!, `updated memory ${updated[0]!.id}`);
  },
 };

@@ -1113,6 +999,7 @@ export const tools: ToolDef[] = [
  projectIdentify,
  memoryWrite,
  memoryUpdate,
+  memoryPatch,
  memoryList,
  memoryGet,
  memorySearch,
@@ -2,37 +2,36 @@

 import { revalidatePath } from "next/cache";
 import { redirect } from "next/navigation";
-import { and, eq, inArray, isNull } from "drizzle-orm";
+import { and, eq, inArray } from "drizzle-orm";
 import { auth } from "@/auth";
 import { db } from "@/lib/db/client";
-import { memories, projects, auditLog } from "@/lib/db/schema";
-import { embedText } from "@/lib/embedder";
+import { projects } from "@/lib/db/schema";
 import { resolveProjectId, upsertProject } from "@/lib/projects";
 import {
  MemoryWriteInput,
  MemoryUpdateInput,
  MemoryDeleteInput,
 } from "@shared-memory/schemas";
+import { getUserGroupNames, readableProjectIds } from "@/lib/access";
 import {
-  CONCURRENT_EDIT_ERROR,
-  canWriteProject,
-  getUserGroupNames,
-  readableProjectIds,
-} from "@/lib/access";
+  createMemory,
+  softDeleteMemory,
+  updateMemory,
+  type Actor,
+  type Outcome,
+  type ProjectResolver,
+} from "@/lib/memory-mutations";

 /**
- * Server Actions for memory CRUD from the Web UI. Mirrors the MCP tools
- * but writes through the same DB layer, so updates and deletes here are
- * indistinguishable from those made via Claude Code.
+ * Server Actions for memory CRUD from the Web UI.
+ *
+ * These are thin adapters: form parsing, then `lib/memory-mutations`,
+ * then revalidate/redirect. The authorize → mutate → re-embed → CAS →
+ * audit sequence lives in that shared module so this surface and the MCP
+ * tools cannot drift apart — they previously did, and the sharing rules
+ * ended up subtly different between them.
 *
 * `actor` is "web" in audit_log so we can tell the two paths apart later.
- *
- * Sharing: project-scope memories may live under projects shared with
- * the user's groups. Reads include those projects; writes require the
- * user to own the project or have an `rw` share. Cross-user concurrent
- * edits use the `version` column for optimistic locking — if the stored
- * version no longer matches what the form submitted, we surface
- * `CONCURRENT_EDIT_ERROR` rather than clobber.
 */

 async function requireUserId(): Promise<string> {
@@ -41,6 +40,52 @@ async function requireUserId(): Promise<string> {
  return session.user.id;
 }

+/** Server Actions signal failure by throwing; the shared layer returns Outcome. */
+function must<T>(outcome: Outcome<T>): T {
+  if (!outcome.ok) throw new Error(outcome.error);
+  return outcome.value;
+}
+
+async function webActor(): Promise<{ actor: Actor; resolveProject: ProjectResolver }> {
+  const userId = await requireUserId();
+  const groups = await getUserGroupNames(userId);
+  return {
+    actor: { userId, groups, via: "web" },
+    resolveProject: webProjectResolver(userId, groups),
+  };
+}
+
+/**
+ * Project resolution for Web UI writes. Unlike the MCP surface, an
+ * unknown key is CREATED rather than rejected — a person typing a project
+ * name into a form means to make one. Shared projects are matched only
+ * within the set the user can actually read, because `projects.key` is
+ * unique per user rather than globally: an unscoped key match could
+ * otherwise select someone else's project.
+ *
+ * Write access to whatever this returns is enforced centrally by the
+ * mutation layer, so it deliberately isn't re-checked here.
+ */
+function webProjectResolver(userId: string, groupNames: string[]): ProjectResolver {
+  return async (key: string) => {
+    const owned = await resolveProjectId(userId, key);
+    if (owned) return { ok: true, value: owned };
+
+    const readableIds = await readableProjectIds(userId, groupNames);
+    const shared =
+      readableIds.length > 0
+        ? await db
+            .select({ id: projects.id })
+            .from(projects)
+            .where(and(eq(projects.key, key), inArray(projects.id, readableIds)))
+            .limit(1)
+        : [];
+    if (shared[0]) return { ok: true, value: shared[0].id };
+
+    return { ok: true, value: await upsertProject(userId, key) };
+  };
+}
+
 function parseTags(raw: FormDataEntryValue | null): string[] {
  if (typeof raw !== "string") return [];
  return raw
@@ -50,95 +95,26 @@ function parseTags(raw: FormDataEntryValue | null): string[] {
 }

 export async function createMemoryAction(formData: FormData) {
-  const userId = await requireUserId();
-  const groupNames = await getUserGroupNames(userId);
+  const { actor, resolveProject } = await webActor();

-  const payload = {
+  const parsed = MemoryWriteInput.safeParse({
    content: String(formData.get("content") ?? "").trim(),
    scope: (formData.get("scope") as "project" | "user") || "project",
    project: (formData.get("project") as string | null)?.trim() || undefined,
    tags: parseTags(formData.get("tags")),
-  };
-  const parsed = MemoryWriteInput.safeParse(payload);
+  });
  if (!parsed.success) {
    throw new Error(parsed.error.issues.map((i) => i.message).join("; "));
  }

-  let projectId: string | null = null;
-  if (parsed.data.scope === "project") {
-    if (!parsed.data.project) throw new Error("scope=project requires `project`");
-    // Same priority as memory.update's reclassification path: prefer an
-    // owned project; otherwise check for a shared one we have rw on;
-    // otherwise auto-upsert as owner.
-    const owned = await resolveProjectId(userId, parsed.data.project);
-    if (owned) {
-      projectId = owned;
-    } else {
-      // Restrict the by-key lookup to projects the user can actually
-      // read. Without this, a different user's project with the same
-      // key string could be selected (`projects.key` is unique per user,
-      // not globally), opening a cross-user write hazard.
-      const readableIds = await readableProjectIds(userId, groupNames);
-      const sharedRow =
-        readableIds.length > 0
-          ? await db
-              .select({ id: projects.id })
-              .from(projects)
-              .where(
-                and(
-                  eq(projects.key, parsed.data.project),
-                  inArray(projects.id, readableIds),
-                ),
-              )
-              .limit(1)
-          : [];
-      if (sharedRow[0]) {
-        const allowed = await canWriteProject(userId, groupNames, sharedRow[0].id);
-        if (!allowed) {
-          throw new Error(`no write access to project '${parsed.data.project}'`);
-        }
-        projectId = sharedRow[0].id;
-      } else {
-        projectId = await upsertProject(userId, parsed.data.project);
-      }
-    }
-  }
-
-  const embedding = await embedText(parsed.data.content);
-
-  const inserted = await db
-    .insert(memories)
-    .values({
-      userId,
-      projectId,
-      scope: parsed.data.scope,
-      content: parsed.data.content,
-      tags: parsed.data.tags ?? [],
-      embedding,
-      lastEditedBy: userId,
-    })
-    .returning({ id: memories.id });
-
-  await db.insert(auditLog).values({
-    userId,
-    actor: "web",
-    action: "memory.write",
-    entityType: "memory",
-    entityId: inserted[0]!.id,
-    payload: {
-      scope: parsed.data.scope,
-      projectKey: parsed.data.project ?? null,
-      tags: parsed.data.tags ?? [],
-    },
-  });
+  const created = must(await createMemory(actor, parsed.data, resolveProject));

  revalidatePath("/memories");
-  redirect(`/memories/${inserted[0]!.id}`);
+  redirect(`/memories/${created.id}`);
 }

 export async function updateMemoryAction(formData: FormData) {
-  const userId = await requireUserId();
-  const groupNames = await getUserGroupNames(userId);
+  const { actor, resolveProject } = await webActor();

  const id = String(formData.get("id") ?? "");
  const rawScope = formData.get("scope");
@@ -164,153 +140,7 @@ export async function updateMemoryAction(formData: FormData) {
    throw new Error(parsed.error.issues.map((i) => i.message).join("; "));
  }

-  // Fetch the row regardless of ownership — we may be editing a shared
-  // memory. Authorization is enforced below against the project, not
-  // by `user_id`.
-  const existingRows = await db
-    .select({
-      id: memories.id,
-      content: memories.content,
-      scope: memories.scope,
-      projectId: memories.projectId,
-      projectKey: projects.key,
-      version: memories.version,
-      userId: memories.userId,
-    })
-    .from(memories)
-    .leftJoin(projects, eq(memories.projectId, projects.id))
-    .where(and(eq(memories.id, parsed.data.id), isNull(memories.deletedAt)))
-    .limit(1);
-  const existing = existingRows[0];
-  if (!existing) throw new Error("not found");
-
-  // Authorize write. For user-scope memories, only the owner can edit.
-  // For project-scope memories, owner OR a group with rw access.
-  if (existing.scope === "user") {
-    if (existing.userId !== userId) throw new Error("not found");
-  } else if (existing.projectId) {
-    const allowed = await canWriteProject(userId, groupNames, existing.projectId);
-    if (!allowed) {
-      throw new Error("you don't have write access to this project");
-    }
-  }
-
-  const update: Record<string, unknown> = {
-    updatedAt: new Date(),
-    lastEditedBy: userId,
-    version: existing.version + 1,
-  };
-  if (parsed.data.tags !== undefined) update.tags = parsed.data.tags;
-  if (parsed.data.content !== undefined && parsed.data.content !== existing.content) {
-    update.content = parsed.data.content;
-    update.embedding = await embedText(parsed.data.content);
-  }
-
-  let scopeChanged = false;
-  let projectChanged = false;
-  let newProjectKey: string | null = existing.projectKey ?? null;
-
-  if (parsed.data.scope !== undefined) {
-    if (parsed.data.scope === "user") {
-      if (existing.scope !== "user") {
-        update.scope = "user";
-        scopeChanged = true;
-      }
-      if (existing.projectId !== null) {
-        update.projectId = null;
-        projectChanged = true;
-        newProjectKey = null;
-      }
-    } else {
-      // scope === 'project' — schema refine guarantees project is set.
-      // Moving INTO a project requires write access there. Owners get
-      // a fresh project upsert; non-owners must target an existing one
-      // they have rw on.
-      const projectKey = parsed.data.project!;
-      let projectId: string;
-      const existingId = await resolveProjectId(userId, projectKey);
-      if (existingId) {
-        projectId = existingId;
-      } else {
-        // Restrict the shared-project lookup to projects the user can
-        // actually read (`projects.key` is unique per user, not globally,
-        // so an unscoped key match could resolve another user's project).
-        const readableIds = await readableProjectIds(userId, groupNames);
-        const sharedRow =
-          readableIds.length > 0
-            ? await db
-                .select({ id: projects.id })
-                .from(projects)
-                .where(
-                  and(eq(projects.key, projectKey), inArray(projects.id, readableIds)),
-                )
-                .limit(1)
-            : [];
-        if (sharedRow[0]) {
-          const allowed = await canWriteProject(userId, groupNames, sharedRow[0].id);
-          if (!allowed) {
-            throw new Error(`no write access to project '${projectKey}'`);
-          }
-          projectId = sharedRow[0].id;
-        } else {
-          // Auto-upsert as owner — user becomes the project owner of a
-          // brand-new private project.
-          projectId = await upsertProject(userId, projectKey);
-        }
-      }
-      if (existing.scope !== "project") {
-        update.scope = "project";
-        scopeChanged = true;
-      }
-      if (existing.projectId !== projectId) {
-        update.projectId = projectId;
-        projectChanged = true;
-        newProjectKey = projectKey;
-      }
-    }
-  }
-
-  // Optimistic-locking guard. When `version` is supplied, the UPDATE
-  // matches on (id, version); a 0-row result means the caller's view
-  // is stale. When `version` is NOT supplied, we still match on the
-  // pre-fetched version to keep behaviour deterministic.
-  const expectedVersion = parsed.data.version ?? existing.version;
-  const updated = await db
-    .update(memories)
-    .set(update)
-    .where(
-      and(
-        eq(memories.id, parsed.data.id),
-        eq(memories.version, expectedVersion),
-      ),
-    )
-    .returning({ id: memories.id });
-
-  if (!updated[0]) throw new Error(CONCURRENT_EDIT_ERROR);
-
-  const auditFields = Object.keys(update).filter(
-    (k) => k !== "updatedAt" && k !== "version" && k !== "lastEditedBy",
-  );
-  const auditPayload: Record<string, unknown> = { fields: auditFields };
-  if (scopeChanged || projectChanged) {
-    auditPayload.scope = {
-      from: existing.scope,
-      to: update.scope ?? existing.scope,
-    };
-    auditPayload.projectKey = {
-      from: existing.projectKey ?? null,
-      to: newProjectKey,
-    };
-  }
-
-  await db.insert(auditLog).values({
-    userId,
-    actor: "web",
-    action: "memory.update",
-    entityType: "memory",
-    entityId: parsed.data.id,
-    payload: auditPayload,
-  });
+  must(await updateMemory(actor, parsed.data, resolveProject));

  revalidatePath(`/memories/${parsed.data.id}`);
  revalidatePath("/memories");
@@ -318,8 +148,7 @@ export async function updateMemoryAction(formData: FormData) {
 }

 export async function deleteMemoryAction(formData: FormData) {
-  const userId = await requireUserId();
-  const groupNames = await getUserGroupNames(userId);
+  const { actor } = await webActor();
  const id = String(formData.get("id") ?? "");
  const rawVersion = formData.get("version");
  const version =
@@ -332,53 +161,7 @@ export async function deleteMemoryAction(formData: FormData) {
  });
  if (!parsed.success) throw new Error(parsed.error.issues[0]!.message);

-  // Authorize delete: same rule as update — owner OR rw on the project.
-  const existing = await db
-    .select({
-      id: memories.id,
-      scope: memories.scope,
-      projectId: memories.projectId,
-      userId: memories.userId,
-      version: memories.version,
-    })
-    .from(memories)
-    .where(and(eq(memories.id, parsed.data.id), isNull(memories.deletedAt)))
-    .limit(1);
-  const row = existing[0];
-  if (!row) throw new Error("not found");
-
-  if (row.scope === "user") {
-    if (row.userId !== userId) throw new Error("not found");
-  } else if (row.projectId) {
-    const allowed = await canWriteProject(userId, groupNames, row.projectId);
-    if (!allowed) throw new Error("you don't have write access to this project");
-  }
-
-  // CAS on version so a peer's concurrent edit can't be silently overwritten
-  // by this delete. Form may or may not supply version; fall back to the row
-  // we just read to keep behaviour deterministic.
-  const expectedVersion = parsed.data.version ?? row.version;
-  const updated = await db
-    .update(memories)
-    .set({ deletedAt: new Date(), lastEditedBy: userId })
-    .where(
-      and(
-        eq(memories.id, parsed.data.id),
-        eq(memories.version, expectedVersion),
-        isNull(memories.deletedAt),
-      ),
-    )
-    .returning({ id: memories.id });
-
-  if (!updated[0]) throw new Error(CONCURRENT_EDIT_ERROR);
-
-  await db.insert(auditLog).values({
-    userId,
-    actor: "web",
-    action: "memory.delete",
-    entityType: "memory",
-    entityId: updated[0].id,
-  });
+  must(await softDeleteMemory(actor, parsed.data));

  revalidatePath("/memories");
  redirect("/memories");
@@ -0,0 +1,263 @@
+import { afterAll, beforeAll, beforeEach, describe, expect, test, vi } from "vitest";
+
+/**
+ * Tests for the shared mutation layer itself — the code both the MCP
+ * tools and the Web UI Server Actions now route through.
+ *
+ * Two things matter here:
+ *   1. The ProjectResolver seam really is the ONLY behavioural difference
+ *      between the two surfaces.
+ *   2. The authorization rule is uniform across update / patch / delete.
+ *      It previously wasn't: delete-over-MCP let a row's author bypass the
+ *      project ACL.
+ */
+vi.mock("@/lib/embedder", () => ({
+  embedText: async (text: string) => {
+    let h = 0;
+    for (let i = 0; i < text.length; i++) h = (h * 31 + text.charCodeAt(i)) | 0;
+    return Array.from({ length: 384 }, (_, i) => ((h + i * 7919) % 1000) / 1000);
+  },
+  embedTexts: async (texts: string[]) => texts.map(() => Array(384).fill(0.1)),
+  embedderReady: async () => true,
+  EmbedderError: class extends Error {},
+}));
+
+const { db, pg } = await import("@/lib/db/client");
+const { memories, projects, users, groups, userGroups, projectShares } = await import(
+  "@/lib/db/schema"
+);
+const { createMemory, updateMemory, patchMemory, softDeleteMemory } = await import(
+  "@/lib/memory-mutations"
+);
+const { and, eq } = await import("drizzle-orm");
+type Actor = import("@/lib/memory-mutations").Actor;
+type ProjectResolver = import("@/lib/memory-mutations").ProjectResolver;
+
+const ISS = "http://test-mutations";
+
+let actor: Actor;
+let otherUserId: string;
+let sharedProjectId: string;
+let sharedGroupId: string;
+
+/** Mirrors the MCP surface: unknown project keys are refused. */
+const refusingResolver: ProjectResolver = async (key) => ({
+  ok: false,
+  error: `unknown project '${key}'; call project.identify first`,
+});
+
+/** Mirrors the Web UI surface: unknown project keys are created. */
+function creatingResolver(userId: string): ProjectResolver {
+  return async (key) => {
+    const existing = await db
+      .select({ id: projects.id })
+      .from(projects)
+      .where(and(eq(projects.key, key), eq(projects.userId, userId)))
+      .limit(1);
+    if (existing[0]) return { ok: true, value: existing[0].id };
+    const created = await db
+      .insert(projects)
+      .values({ userId, key, displayName: key })
+      .returning({ id: projects.id });
+    return { ok: true, value: created[0]!.id };
+  };
+}
+
+async function seedMemory(userId: string, projectId: string | null): Promise<string> {
+  const r = await db
+    .insert(memories)
+    .values({
+      userId,
+      projectId,
+      scope: projectId ? "project" : "user",
+      content: "line one\nline two\n",
+      tags: [],
+      embedding: Array(384).fill(0.5),
+      lastEditedBy: userId,
+    })
+    .returning({ id: memories.id });
+  return r[0]!.id;
+}
+
+async function setShareAccess(access: "ro" | "rw") {
+  await db
+    .insert(projectShares)
+    .values({ projectId: sharedProjectId, groupId: sharedGroupId, access })
+    .onConflictDoUpdate({
+      target: [projectShares.projectId, projectShares.groupId],
+      set: { access },
+    });
+}
+
+beforeAll(async () => {
+  const me = await db
+    .insert(users)
+    .values({ oidcSub: "mut-me", oidcIss: ISS })
+    .onConflictDoNothing()
+    .returning({ id: users.id });
+  const myId =
+    me[0]?.id ??
+    (
+      await db.select({ id: users.id }).from(users).where(eq(users.oidcSub, "mut-me"))
+    )[0]!.id;
+
+  const other = await db
+    .insert(users)
+    .values({ oidcSub: "mut-other", oidcIss: ISS })
+    .onConflictDoNothing()
+    .returning({ id: users.id });
+  otherUserId =
+    other[0]?.id ??
+    (
+      await db.select({ id: users.id }).from(users).where(eq(users.oidcSub, "mut-other"))
+    )[0]!.id;
+
+  const p = await db
+    .insert(projects)
+    .values({ userId: otherUserId, key: "mut-shared", displayName: "Shared" })
+    .onConflictDoNothing()
+    .returning({ id: projects.id });
+  sharedProjectId =
+    p[0]?.id ??
+    (
+      await db
+        .select({ id: projects.id })
+        .from(projects)
+        .where(eq(projects.key, "mut-shared"))
+    )[0]!.id;
+
+  const g = await db
+    .insert(groups)
+    .values({ oidcIss: ISS, name: "mut-team" })
+    .onConflictDoNothing()
+    .returning({ id: groups.id });
+  sharedGroupId =
+    g[0]?.id ??
+    (
+      await db.select({ id: groups.id }).from(groups).where(eq(groups.name, "mut-team"))
+    )[0]!.id;
+
+  await db
+    .insert(userGroups)
+    .values({ userId: myId, groupId: sharedGroupId })
+    .onConflictDoNothing();
+
+  actor = { userId: myId, groups: ["mut-team"], via: "mcp" };
+});
+
+beforeEach(async () => {
+  await db.delete(memories);
+  await setShareAccess("rw");
+});
+
+afterAll(async () => {
+  await db.delete(memories);
+  await pg.end();
+});
+
+describe("the ProjectResolver seam", () => {
+  test("a refusing resolver rejects an unknown project without creating one", async () => {
+    const res = await createMemory(
+      actor,
+      { content: "x", scope: "project", project: "brand-new-key", tags: [] },
+      refusingResolver,
+    );
+
+    expect(res.ok).toBe(false);
+    const rows = await db
+      .select({ id: projects.id })
+      .from(projects)
+      .where(eq(projects.key, "brand-new-key"));
+    expect(rows).toHaveLength(0);
+  });
+
+  test("a creating resolver makes the project and writes into it", async () => {
+    const res = await createMemory(
+      actor,
+      { content: "x", scope: "project", project: "made-on-demand", tags: [] },
+      creatingResolver(actor.userId),
+    );
+
+    expect(res.ok).toBe(true);
+    const rows = await db
+      .select({ id: projects.id })
+      .from(projects)
+      .where(eq(projects.key, "made-on-demand"));
+    expect(rows).toHaveLength(1);
+  });
+});
+
+describe("authorization is uniform across mutations", () => {
+  // Each of these seeds a memory the actor AUTHORED, then downgrades the
+  // share to read-only. Authoring must not survive as a write privilege.
+  test("update is denied on a read-only share", async () => {
+    const id = await seedMemory(actor.userId, sharedProjectId);
+    await setShareAccess("ro");
+
+    const res = await updateMemory(actor, { id, content: "edited" }, refusingResolver);
+
+    expect(res.ok).toBe(false);
+  });
+
+  test("patch is denied on a read-only share", async () => {
+    const id = await seedMemory(actor.userId, sharedProjectId);
+    await setShareAccess("ro");
+
+    const res = await patchMemory(actor, {
+      id,
+      old_string: "line one",
+      new_string: "line uno",
+    });
+
+    expect(res.ok).toBe(false);
+  });
+
+  test("delete is denied on a read-only share", async () => {
+    const id = await seedMemory(actor.userId, sharedProjectId);
+    await setShareAccess("ro");
+
+    const res = await softDeleteMemory(actor, { id });
+
+    expect(res.ok).toBe(false);
+  });
+
+  test("all three are allowed again once the share is read-write", async () => {
+    const id = await seedMemory(actor.userId, sharedProjectId);
+
+    expect((await updateMemory(actor, { id, content: "a\nb\n" }, refusingResolver)).ok).toBe(
+      true,
+    );
+    expect((await patchMemory(actor, { id, old_string: "a", new_string: "c" })).ok).toBe(
+      true,
+    );
+    expect((await softDeleteMemory(actor, { id })).ok).toBe(true);
+  });
+
+  test("another user's user-scope memory is invisible to all three", async () => {
+    const id = await seedMemory(otherUserId, null);
+
+    expect((await updateMemory(actor, { id, content: "x" }, refusingResolver)).ok).toBe(
+      false,
+    );
+    expect(
+      (await patchMemory(actor, { id, old_string: "line one", new_string: "y" })).ok,
+    ).toBe(false);
+    expect((await softDeleteMemory(actor, { id })).ok).toBe(false);
+  });
+});
+
+describe("audit trail records the originating surface", () => {
+  test("via: 'web' and via: 'mcp' are both preserved", async () => {
+    const webRes = await createMemory(
+      { ...actor, via: "web" },
+      { content: "from the web", scope: "user", tags: [] },
+      refusingResolver,
+    );
+    expect(webRes.ok).toBe(true);
+
+    const rows = await pg<{ actor: string }[]>`
+      SELECT actor FROM audit_log WHERE action = 'memory.write' ORDER BY created_at DESC LIMIT 1
+    `;
+    expect(rows[0]!.actor).toBe("web");
+  });
+});
@@ -0,0 +1,357 @@
+import { and, eq, isNull } from "drizzle-orm";
+import { db } from "@/lib/db/client";
+import { memories, projects, auditLog } from "@/lib/db/schema";
+import { embedText } from "@/lib/embedder";
+import { applyPatch } from "@/lib/memory-patch";
+import { CONCURRENT_EDIT_ERROR, canWriteProject } from "@/lib/access";
+import type {
+  MemoryDeleteInput,
+  MemoryPatchInput,
+  MemoryUpdateInput,
+  MemoryWriteInput,
+} from "@shared-memory/schemas";
+
+/**
+ * The single write path for memories.
+ *
+ * Both surfaces — the MCP tools and the Web UI Server Actions — used to
+ * reimplement authorize → mutate → re-embed → CAS → audit independently.
+ * They drifted: `memory.delete` over MCP skipped the project ACL whenever
+ * the caller happened to author the row, which `memory.update` and the
+ * whole Web UI did not. Consolidating here is what keeps those rules in
+ * one place, so a change to the sharing model can't be half-applied.
+ *
+ * Callers keep their own presentation concerns: MCP maps Outcome to a
+ * ToolResult, the Web UI throws and then revalidates/redirects.
+ */
+
+export interface Actor {
+  userId: string;
+  /** Group names, for project-share authorization. */
+  groups: string[];
+  /** Recorded as audit_log.actor so the two surfaces stay distinguishable. */
+  via: "web" | "mcp";
+}
+
+export type Outcome<T> = { ok: true; value: T } | { ok: false; error: string };
+
+const fail = (error: string): Outcome<never> => ({ ok: false, error });
+const succeed = <T>(value: T): Outcome<T> => ({ ok: true, value });
+
+/**
+ * Resolves a project key to an id for a write. Injected because this is
+ * the one place the two surfaces genuinely, deliberately differ: MCP
+ * refuses unknown projects (the caller is expected to run project.identify
+ * first), while the Web UI creates one owned by the user. Everything else
+ * about a write is identical.
+ */
+export type ProjectResolver = (key: string) => Promise<Outcome<string>>;
+
+interface WriteTarget {
+  scope: "project" | "user";
+  projectId: string | null;
+  userId: string;
+}
+
+/**
+ * The authorization rule for every mutating operation:
+ *   - user-scope  → only the owner may write (anything else reads as 404)
+ *   - project-scope → owner of the project, or a group with `rw`
+ *
+ * Authoring a row grants nothing on its own. A memory you wrote while a
+ * share was `rw` becomes read-only to you when an owner downgrades that
+ * share to `ro` — the project ACL is the authority, not the byline.
+ */
+async function authorizeWrite(actor: Actor, row: WriteTarget): Promise<Outcome<null>> {
+  if (row.scope === "user") {
+    return row.userId === actor.userId ? succeed(null) : fail("not found");
+  }
+  if (row.projectId) {
+    const allowed = await canWriteProject(actor.userId, actor.groups, row.projectId);
+    if (!allowed) return fail("no write access to this project");
+  }
+  return succeed(null);
+}
+
+export async function createMemory(
+  actor: Actor,
+  input: MemoryWriteInput,
+  resolveProject: ProjectResolver,
+): Promise<Outcome<{ id: string; createdAt: Date }>> {
+  let projectId: string | null = null;
+  const projectKey = input.scope === "project" ? input.project : undefined;
+
+  if (input.scope === "project") {
+    if (!projectKey) return fail("scope=project requires `project`");
+    const resolved = await resolveProject(projectKey);
+    if (!resolved.ok) return resolved;
+    projectId = resolved.value;
+    const allowed = await canWriteProject(actor.userId, actor.groups, projectId);
+    if (!allowed) return fail(`no write access to project '${projectKey}'`);
+  }
+
+  // Embed inline so the new memory is searchable immediately. Slower
+  // writes (~50–150 ms) are an acceptable price for that guarantee.
+  const embedding = await embedText(input.content);
+
+  const inserted = await db
+    .insert(memories)
+    .values({
+      userId: actor.userId,
+      projectId,
+      scope: input.scope,
+      content: input.content,
+      tags: input.tags ?? [],
+      embedding,
+      lastEditedBy: actor.userId,
+    })
+    .returning({ id: memories.id, createdAt: memories.createdAt });
+
+  const row = inserted[0]!;
+  await db.insert(auditLog).values({
+    userId: actor.userId,
+    actor: actor.via,
+    action: "memory.write",
+    entityType: "memory",
+    entityId: row.id,
+    payload: {
+      scope: input.scope,
+      projectKey: projectKey ?? null,
+      tags: input.tags ?? [],
+    },
+  });
+
+  return succeed(row);
+}
+
+export interface MutatedMemory {
+  id: string;
+  updatedAt: Date;
+  version: number;
+}
+
+export async function updateMemory(
+  actor: Actor,
+  input: MemoryUpdateInput,
+  resolveProject: ProjectResolver,
+): Promise<Outcome<MutatedMemory>> {
+  const existingRows = await db
+    .select({
+      id: memories.id,
+      content: memories.content,
+      scope: memories.scope,
+      projectId: memories.projectId,
+      projectKey: projects.key,
+      version: memories.version,
+      userId: memories.userId,
+    })
+    .from(memories)
+    .leftJoin(projects, eq(memories.projectId, projects.id))
+    .where(and(eq(memories.id, input.id), isNull(memories.deletedAt)))
+    .limit(1);
+  const existing = existingRows[0];
+  if (!existing) return fail("not found");
+
+  const authorized = await authorizeWrite(actor, existing);
+  if (!authorized.ok) return authorized;
+
+  const update: Record<string, unknown> = {
+    updatedAt: new Date(),
+    lastEditedBy: actor.userId,
+    version: existing.version + 1,
+  };
+  if (input.tags !== undefined) update.tags = input.tags;
+  if (input.content !== undefined && input.content !== existing.content) {
+    update.content = input.content;
+    update.embedding = await embedText(input.content);
+  }
+
+  let scopeChanged = false;
+  let projectChanged = false;
+  let newProjectKey: string | null = existing.projectKey ?? null;
+
+  if (input.scope !== undefined) {
+    if (input.scope === "user") {
+      if (existing.scope !== "user") {
+        update.scope = "user";
+        scopeChanged = true;
+      }
+      if (existing.projectId !== null) {
+        update.projectId = null;
+        projectChanged = true;
+        newProjectKey = null;
+      }
+    } else {
+      // scope === 'project' — the schema refine guarantees `project` is set.
+      // Moving INTO a project requires write access there.
+      const projectKey = input.project!;
+      const resolved = await resolveProject(projectKey);
+      if (!resolved.ok) return resolved;
+      const targetId = resolved.value;
+      const allowed = await canWriteProject(actor.userId, actor.groups, targetId);
+      if (!allowed) return fail(`no write access to project '${projectKey}'`);
+
+      if (existing.scope !== "project") {
+        update.scope = "project";
+        scopeChanged = true;
+      }
+      if (existing.projectId !== targetId) {
+        update.projectId = targetId;
+        projectChanged = true;
+        newProjectKey = projectKey;
+      }
+    }
+  }
+
+  const updated = await casUpdate(input.id, update, input.version ?? existing.version);
+  if (!updated) return fail(CONCURRENT_EDIT_ERROR);
+
+  const auditFields = Object.keys(update).filter(
+    (k) => k !== "updatedAt" && k !== "version" && k !== "lastEditedBy",
+  );
+  const auditPayload: Record<string, unknown> = { fields: auditFields };
+  if (scopeChanged || projectChanged) {
+    auditPayload.scope = { from: existing.scope, to: update.scope ?? existing.scope };
+    auditPayload.projectKey = { from: existing.projectKey ?? null, to: newProjectKey };
+  }
+
+  await db.insert(auditLog).values({
+    userId: actor.userId,
+    actor: actor.via,
+    action: "memory.update",
+    entityType: "memory",
+    entityId: updated.id,
+    payload: auditPayload,
+  });
+
+  return succeed(updated);
+}
+
+export async function patchMemory(
+  actor: Actor,
+  input: MemoryPatchInput,
+): Promise<Outcome<MutatedMemory & { contentLength: number; delta: number }>> {
+  const existingRows = await db
+    .select({
+      content: memories.content,
+      scope: memories.scope,
+      projectId: memories.projectId,
+      version: memories.version,
+      userId: memories.userId,
+    })
+    .from(memories)
+    .where(and(eq(memories.id, input.id), isNull(memories.deletedAt)))
+    .limit(1);
+  const existing = existingRows[0];
+  if (!existing) return fail("not found");
+
+  const authorized = await authorizeWrite(actor, existing);
+  if (!authorized.ok) return authorized;
+
+  const patch = applyPatch(existing.content, input.old_string, input.new_string);
+  if (!patch.ok) return fail(patch.error);
+
+  const updated = await casUpdate(
+    input.id,
+    {
+      content: patch.content,
+      embedding: await embedText(patch.content),
+      updatedAt: new Date(),
+      lastEditedBy: actor.userId,
+      version: existing.version + 1,
+    },
+    input.version ?? existing.version,
+  );
+  if (!updated) return fail(CONCURRENT_EDIT_ERROR);
+
+  await db.insert(auditLog).values({
+    userId: actor.userId,
+    actor: actor.via,
+    action: "memory.patch",
+    entityType: "memory",
+    entityId: updated.id,
+    payload: {
+      fields: ["content"],
+      patch: {
+        offset: existing.content.indexOf(input.old_string),
+        removed: input.old_string.length,
+        added: input.new_string.length,
+      },
+    },
+  });
+
+  return succeed({
+    ...updated,
+    contentLength: patch.content.length,
+    delta: patch.content.length - existing.content.length,
+  });
+}
+
+export async function softDeleteMemory(
+  actor: Actor,
+  input: MemoryDeleteInput,
+): Promise<Outcome<{ id: string }>> {
+  const rows = await db
+    .select({
+      id: memories.id,
+      userId: memories.userId,
+      projectId: memories.projectId,
+      scope: memories.scope,
+      version: memories.version,
+    })
+    .from(memories)
+    .where(and(eq(memories.id, input.id), isNull(memories.deletedAt)))
+    .limit(1);
+  const existing = rows[0];
+  if (!existing) return fail("not found");
+
+  const authorized = await authorizeWrite(actor, existing);
+  if (!authorized.ok) return authorized;
+
+  const updated = await db
+    .update(memories)
+    .set({ deletedAt: new Date(), lastEditedBy: actor.userId })
+    .where(
+      and(
+        eq(memories.id, input.id),
+        eq(memories.version, input.version ?? existing.version),
+        isNull(memories.deletedAt),
+      ),
+    )
+    .returning({ id: memories.id });
+
+  if (!updated[0]) return fail(CONCURRENT_EDIT_ERROR);
+
+  await db.insert(auditLog).values({
+    userId: actor.userId,
+    actor: actor.via,
+    action: "memory.delete",
+    entityType: "memory",
+    entityId: updated[0].id,
+  });
+
+  return succeed(updated[0]);
+}
+
+/**
+ * Compare-and-set on `version`. A zero-row result means a peer edited the
+ * row between our read and this write. Callers that omit an explicit
+ * version pass the one they just read, which still closes the read-
+ * modify-write window inside a single handler.
+ */
+async function casUpdate(
+  id: string,
+  update: Record<string, unknown>,
+  expectedVersion: number,
+): Promise<MutatedMemory | null> {
+  const rows = await db
+    .update(memories)
+    .set(update)
+    .where(and(eq(memories.id, id), eq(memories.version, expectedVersion)))
+    .returning({
+      id: memories.id,
+      updatedAt: memories.updatedAt,
+      version: memories.version,
+    });
+  return rows[0] ?? null;
+}
@@ -0,0 +1,77 @@
+import { describe, expect, test } from "vitest";
+import { applyPatch } from "@/lib/memory-patch";
+
+describe("applyPatch", () => {
+  test("replaces an old_string that occurs exactly once", () => {
+    const result = applyPatch("alpha beta gamma", "beta", "BETA");
+
+    expect(result.ok).toBe(true);
+    if (result.ok) expect(result.content).toBe("alpha BETA gamma");
+  });
+
+  test("refuses when old_string is absent, rather than silently doing nothing", () => {
+    const result = applyPatch("alpha beta gamma", "delta", "DELTA");
+
+    expect(result.ok).toBe(false);
+    if (!result.ok) expect(result.error).toMatch(/not found/i);
+  });
+
+  test("refuses when old_string is ambiguous, and reports the match count", () => {
+    const result = applyPatch("x marks the spot, x marks it twice", "x", "y");
+
+    expect(result.ok).toBe(false);
+    if (!result.ok) {
+      expect(result.error).toMatch(/2/);
+      expect(result.error).toMatch(/match/i);
+    }
+  });
+
+  test("treats old_string literally, not as a regular expression", () => {
+    // A naive RegExp implementation would match "axb" here.
+    const result = applyPatch("axb and a.b", "a.b", "REPLACED");
+
+    expect(result.ok).toBe(true);
+    if (result.ok) expect(result.content).toBe("axb and REPLACED");
+  });
+
+  test("replaces a multi-line old_string, preserving surrounding text", () => {
+    const content = "## HEADING\n- one\n- two\n\n## OTHER\n";
+    const result = applyPatch(content, "## HEADING\n- one", "## HEADING\n- zero\n- one");
+
+    expect(result.ok).toBe(true);
+    if (result.ok) {
+      expect(result.content).toBe("## HEADING\n- zero\n- one\n- two\n\n## OTHER\n");
+    }
+  });
+
+  test("rejects a patch whose result would exceed the 64,000-char content limit", () => {
+    // The anchor must be unique, or the ambiguity check fires first and
+    // this stops testing the length limit at all.
+    const content = "A".repeat(63_950) + "ANCHOR";
+    const result = applyPatch(content, "ANCHOR", "B".repeat(100));
+
+    expect(result.ok).toBe(false);
+    if (!result.ok) expect(result.error).toMatch(/64,?000|limit/i);
+  });
+
+  test("rejects a no-op patch where new_string equals old_string", () => {
+    const result = applyPatch("alpha beta", "beta", "beta");
+
+    expect(result.ok).toBe(false);
+    if (!result.ok) expect(result.error).toMatch(/identical|no-op|unchanged/i);
+  });
+
+  test("allows a patch that deletes text by replacing with an empty string", () => {
+    const result = applyPatch("keep this, drop this", ", drop this", "");
+
+    expect(result.ok).toBe(true);
+    if (result.ok) expect(result.content).toBe("keep this");
+  });
+
+  test("rejects a patch that would empty the memory entirely", () => {
+    const result = applyPatch("all of it", "all of it", "");
+
+    expect(result.ok).toBe(false);
+    if (!result.ok) expect(result.error).toMatch(/empty/i);
+  });
+});
@@ -0,0 +1,76 @@
+import { MEMORY_CONTENT_MAX } from "@shared-memory/schemas";
+
+/**
+ * Pure string-level semantics for `memory.patch`.
+ *
+ * Kept free of any DB or auth dependency so both the MCP tool handler and
+ * the Web UI can share it, and so the refuse-rather-than-clobber rules
+ * below are directly testable.
+ *
+ * The contract mirrors the file-editing primitive coding agents already
+ * use: an `old_string` that is absent or ambiguous is an ERROR, never a
+ * silent no-op and never an arbitrary pick. That refusal is the property
+ * that makes the operation safe to hand to an agent editing a shared
+ * document it cannot afford to corrupt.
+ */
+export type PatchOutcome =
+  | { ok: true; content: string }
+  | { ok: false; error: string };
+
+function countOccurrences(haystack: string, needle: string): number {
+  let count = 0;
+  let from = 0;
+  for (;;) {
+    const at = haystack.indexOf(needle, from);
+    if (at === -1) return count;
+    count += 1;
+    // Advance past this match so overlapping matches aren't double-counted.
+    from = at + needle.length;
+  }
+}
+
+export function applyPatch(
+  content: string,
+  oldString: string,
+  newString: string,
+): PatchOutcome {
+  if (oldString === newString) {
+    return {
+      ok: false,
+      error: "old_string and new_string are identical; the patch would change nothing",
+    };
+  }
+
+  const first = content.indexOf(oldString);
+  if (first === -1) {
+    return {
+      ok: false,
+      error:
+        "old_string not found in the memory content; nothing was changed. Fetch the memory with memory.get and copy the exact text you mean to replace.",
+    };
+  }
+
+  // Only pay for a full count once we know there's more than one match.
+  if (content.indexOf(oldString, first + oldString.length) !== -1) {
+    const count = countOccurrences(content, oldString);
+    return {
+      ok: false,
+      error: `old_string matches ${count} times; it must match exactly once. Nothing was changed — include more surrounding context to identify the one you mean.`,
+    };
+  }
+
+  const patched =
+    content.slice(0, first) + newString + content.slice(first + oldString.length);
+
+  if (patched.length === 0) {
+    return { ok: false, error: "the patch would leave the memory empty" };
+  }
+  if (patched.length > MEMORY_CONTENT_MAX) {
+    return {
+      ok: false,
+      error: `the patched content would be ${patched.length.toLocaleString("en-US")} characters, over the ${MEMORY_CONTENT_MAX.toLocaleString("en-US")}-character limit`,
+    };
+  }
+
+  return { ok: true, content: patched };
+}