backlog: share MCP/viewer access and schema primitives

[ZeR020]

Status

Private backlog on this fork only. Do not implement until the pi 8-layer stack is on upstream main (or abandoned). Do not add commits to stack/1…stack/8.

Do not mention this issue on upstream PRs.

What this is

kunickiaj’s review of the original pi PR listed an important follow-up (not one of the seven blockers):

MCP/viewer memory access and schema behavior should share core primitives to avoid authorization and contract drift.

His stack sketch put this in layer 1: “Shared spool/memory-access refactors.”

We already shipped spool + the kind catalog in layer 1. We did not ship shared access helpers. This issue is the rest of that follow-up.

Plain language: MCP and viewer HTTP are two doors into the same notebook. The rules for “what kinds exist” and “may this caller see/write this note” must live in @codemem/core. Each door calls those rules. They must not keep their own copies.

Already done (do not redo)

• packages/core/src/memory-kinds.ts — kinds + validateMemoryKind
• MCP memory-kinds.ts re-exports core
• Viewer remember routes import REMEMBER_MEMORY_KINDS
• Bounded JSON parser exported from viewer helpers; L3 POSTs use it
• Auth check both doors already use is store.timeline(..., filters)

Still to do

Schema (contract)

1. MCP memoryKindSchema in packages/mcp-server/src/schemas.ts must be derived from REMEMBER_MEMORY_KINDS. Delete the handwritten z.enum(["discovery", …]).
2. One filter-key list in @codemem/core. Viewer SCHEMA_FILTER_NAMES and MCP filterNames both come from it. No second hand-sorted array.

Access (authorization)

Move the twins into core. Callers pass only what differs:

• getVisibleMemory(store, id, filters) → store.timeline(null, id, 0, 0, filters).find(...)
• getVisibleMemories / forgetVisibleMemory the same way
• rememberVisibleMemory(store, input, { toolVersion, metadata, envProject, cwd, user, now })

MCP keeps toolVersion: "mcp-ts", metadata: { mcp: true }.
Viewer keeps toolVersion: "viewer-api", metadata: { viewer: true }.

Existing MCP tests in memory-access.test.ts should keep passing against the core functions (or thin aliases).

Must not change (regression guards)

Sharing primitives does not mean sharing defaults.

• Viewer read project default stays null. Do not inject process cwd / CODEMEM_PROJECT on HTTP.
• MCP read may still default project from cwd/env. Pass defaultProject in; do not pick one policy for both.
• Writes on both doors already honor explicit project or env only. Keep that.
• Do not extract expandMemories, distill file loading, HTTP parseGetFilters, or the retrieval ledger.

When to implement

1. Layer 1 is on upstream main.
2. Prefer waiting until layer 3 (viewer routes) is also there, so one PR can switch both doors.
3. Branch from upstream main, not from stack/8.
4. Do not shrink this back to “lists only.”

Verification

• pnpm exec vitest run packages/mcp-server/src/memory-access.test.ts packages/mcp-server/src/server.test.ts
• CODEMEM_EMBEDDING_DISABLED=1 pnpm exec vitest run packages/viewer-server/src/routes/memory-tools.test.ts
• MCP kind enum === REMEMBER_MEMORY_KINDS
• Viewer schema filter names === MCP filterNames === core list
• Nested-cwd / no-implicit-project tests on the viewer still pass
• tool_version / session metadata still mcp-ts vs viewer-api