FazBrowse GitHub Viewer | Trending |
URL:
| Home
Tools: [Download Repo ZIP]   [Original HTTPS Page]

docs: chat sessions design (save every chat, resume any chat) by ndemianc · Pull Request #60 · levelcodeai/levelcode · GitHub

/ levelcode Public

docs: chat sessions design (save every chat, resume any chat) #60

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
ndemianc wants to merge 1 commit into from
Conversation 2 Commits 1 Checks 1 Files changed
Closed

docs: chat sessions design (save every chat, resume any chat) #60

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension .md  (1) All 1 file type selected
Viewed files
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Unified
Split
Hide whitespace
Diff view
Unified
Split
Hide whitespace
279 changes: 279 additions & 0 deletions docs/levelcode-chat-sessions-design.md
Show comments
View file
Open in desktop
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode characters
Show hidden characters
Original file line number Diff line number Diff line change
@@ -0,0 +1,279 @@
# Chat Sessions — design

**Status:** proposed · **Scope:** `extensions/levelcode-ai` (chat + agent) · **Depends on:** nothing new; reuses the M5 compaction machinery

The problem, in one sentence: **"New Chat" is destructive.** `conversation` and
`agentMessages` are module-level in-memory arrays; `newChat()` wipes them, and so does a
window reload or a crash. A user who starts a new chat — or whose editor restarts —
loses the old one forever. Every serious AI editor now treats a chat as a *session*:
saved automatically, listed, resumable.

---

## 1. Goals & non-goals

**Goals**

1. Every chat is **saved automatically, locally**, without the user doing anything.
2. "New Chat" starts a fresh session; the previous one appears in a **History** list.
3. Any listed session can be **resumed** — even one that no longer fits the model's
context window (that is where summarization enters, and *only* there).
4. Sessions survive window reloads, crashes, editor updates, and **folder renames**.
5. Everything is inspectable plain text on the user's disk — the hackable ethos, and
the BYOK privacy promise: nothing leaves the machine.

**Non-goals (for this milestone)**

- Cross-device sync (that is M9 / LevelCode Sync territory; this design feeds it).
- Sharing sessions (the LevelLinks concept builds on this file format later).
- Restoring *files* to a session's point in time — per-turn checkpoints already own
file restore and remain per-live-session.

---

## 2. Where we are today (grounded in the code)

- `extension.js`: `let conversation = []` (chat) and `agentMessages` (agent loop) are
in-memory only. `newChat()` resets both, kills background commands and MCP servers,
finalizes pending reviews, and posts `reset` to the webview. Nothing is written
anywhere.
- **Compaction already exists**: `compactAgentMemory()` summarizes the bulky head of a
live session into a briefing using `COMPACT_SYSTEM` / `COMPACT_INSTRUCTIONS`, cutting
only at a user-message boundary so tool_use/tool_result pairs are never orphaned.
This is exactly the machinery session resume needs — it just needs to run against a
*loaded* transcript, not only the live one.
- Keep/Undo pending reviews persist in `globalState` (`levelcode.ai.pendingReviews`)
and already survive reloads, keyed by file URI — orthogonal to sessions, but a
session must *reference* its pending-review era so resume tells the truth.
- The webview (`media/chat.html`) renders from posted messages; it can replay a
transcript it is fed. No storage of its own.

## 3. Prior art — what the three incumbents actually do

### VS Code Copilot Chat
- **Mechanics:** one JSON file per session under
`…/User/workspaceStorage/<workspace-hash>/chatSessions/`, plus a session index in
`state.vscdb`. History quick-pick + export/import commands.
- **What works:** plain JSON per session; per-workspace scoping; auto titles.
- **What fails — loudly, in public issues:** the workspace **hash** is derived from the
folder URI, so renaming/moving a folder, saving an untitled workspace, or reopening
in a dev container orphans every session (microsoft/vscode #285059, #301793,
#305818); a corrupted `state.vscdb` index hides sessions that still exist on disk
(community repair tools exist for exactly this). **Lesson: never make a URI-derived
hash the only key, and never let an index be load-bearing.**

### Cursor
- **Mechanics:** everything in SQLite (`state.vscdb`) — global `cursorDiskKV` table
with `composerData:<id>` (session metadata) and `bubbleId:<composerId>:<bubbleId>`
(每 message), workspace DBs for the rest. History panel, checkpoints, long-context
condensation.
- **What works:** robust incremental writes (one row per bubble); global storage means
sessions survive workspace-identity changes; snappy history UI.
- **What fails:** the store is **opaque** — users need third-party exporter tools to
read their own history, WAL/corruption incidents lock people out, and nothing is
greppable. **Lesson: an AI editor's memory should not need a reverse-engineered
schema to read.**

### Claude Code
- **Mechanics:** one **JSONL file per session** under
`~/.claude/projects/<project-path-slug>/<session-id>.jsonl` — append-only events,
one JSON object per line. `--continue` resumes the last session, `--resume` shows a
picker; sessions are titled; when a resumed/long session approaches the context
limit it is **auto-compacted**: the head is summarized, recent turns stay verbatim.
- **What works — and why this is the model to copy:** append-only = crash-safe by
construction (a crash costs at most the line being written); the project *path slug*
is human-readable and survives editor reinstalls; plain JSONL means `grep`, `jq`,
and third-party tooling work day one; storage is verbatim and lossless while
summarization is reserved for the one place it is needed — fitting an old
conversation back into a finite context window.

### The synthesis LevelCode adopts

| Decision | Choice | Because |
|---|---|---|
| Storage format | Append-only JSONL, one file per session | Crash-safe, greppable, hackable (Claude Code); no opaque DB (anti-Cursor) |
| Location | `~/.levelcode/sessions/<project-slug>/` | Survives reinstalls & workspace-identity churn (anti-Copilot); `dataFolderName` is already `.levelcode` |
| Keying | Human-readable project path slug **plus** the real path stored inside each file | A renamed folder degrades to "listed under old name", never to "lost" |
| Index | `index.json` per project, **rebuildable by scanning** | An index may cache, it must never be load-bearing (anti-Copilot #vscdb-corruption) |
| What gets summarized | **Nothing at rest.** Transcripts are stored verbatim | Disk is free; tokens are not. Summarizing to store pays money to lose information |
| Where summarization IS used | (a) resume when the transcript exceeds the context budget — reuse `compactAgentMemory`; (b) async title generation | The user's instinct ("summarize with an LLM") lands here, not in storage |
| Privacy | Local files only; never uploaded | The BYOK promise; M9 sync may later offer opt-in encrypted sync of this same format |

## 4. Data model

```
~/.levelcode/sessions/
<project-slug>/ e.g. -Users-ada-code-thin-ly (path, slashes → dashes)
index.json cache: [{id, title, createdAt, updatedAt, turns, model, preview}]
2026-07-28T09-12-33-8f3k.jsonl
2026-07-28T14-02-10-p9q2.jsonl
```

**Session file = one meta line + append-only events** (schema-versioned):

```jsonl
{"kind":"meta","v":1,"id":"2026-07-28T09-12-33-8f3k","project":"/Users/ada/code/thin.ly","createdAt":"…","title":null}
{"kind":"user","t":"…","content":"Add idempotency to RefundService…","contextFiles":["app/services/refund.rb"]}
{"kind":"assistant","t":"…","content":[…provider content blocks, verbatim…]}
{"kind":"agent","t":"…","messages":[…the agentMessages delta for this turn…]}
{"kind":"event","t":"…","type":"checkpoint","n":3}
{"kind":"title","t":"…","title":"Idempotent refunds via Redis keys"}
{"kind":"compact","t":"…","briefing":"…","coversThrough":41}
```

Rules:

- **Verbatim provider shapes.** `conversation` and `agentMessages` entries are stored
as-is (the same objects sent to the provider), so resume rebuilds byte-identical
arrays — no lossy re-parsing. Schema `v` guards future migrations.
- **Append-only.** One `fs.appendFile` per turn (debounced 500ms), fsync'd. Never
rewrite the file except `compact` events, which are *also appended* — a compaction
is an event in the history, not a rewrite of it.
Comment on lines +129 to +131
- **The meta line is written at session birth**, so even a one-message crash leaves a
listable session.
- **Caps:** a session file is soft-capped (default 20 MB — huge tool outputs are
already truncated upstream); beyond it, oldest `agent` tool-result payloads are
elided on load (they are never resent to the model anyway once compacted).
- `index.json` is written atomically (tmp + rename) after each turn; on any read
error or mismatch it is **rebuilt by scanning the directory** — self-healing.

## 5. Lifecycle

### Autosave (the default state of the world)
Every turn appends its events. There is no Save button and no dirty state. The live
session id lives in `workspaceState` so a window reload re-opens the same session
(webview replays the transcript; background commands/MCP are *not* resurrected — a
`event:"reload"` line records the discontinuity honestly).

### New Chat
`newChat()` keeps its reaping semantics (kill commands/MCP, finalize reviews, drop
checkpoints) but first **seals the current session** (final index update, kick off
async title generation if still untitled) and then opens a fresh file. Nothing is
lost — the old session is one click away in History.

### Titles
On seal (or after the 2nd user turn, whichever first): if untitled, generate one
asynchronously with the **fast/cheap lane** (the same per-provider fast model routing
autocomplete uses; ≤ 200 tokens: "6 words, imperative, no punctuation"). Failure or
BYOK-frugal mode falls back to the first user message, truncated. Titles are events,
so retitling is append-not-rewrite; a manual **Rename** writes the same event.

### Resume — the three-tier rule
Let `T` = stored transcript tokens (estimated as today, chars/4), `W` = model context
window, `B` = the context budget resume may spend (default 40% of `W`):

1. **T ≤ B — verbatim resume.** Arrays rebuilt exactly; the model sees the same
conversation it left. No summarization, no cost.
2. **T > B, has prior `compact` event — incremental.** Load the last briefing + turns
after `coversThrough`; if still over budget, fall through to (3) on the remainder.
3. **T > B — compact-on-resume.** Run `compactAgentMemory()`'s exact machinery over
the head (cut at a user-message boundary, never orphaning tool pairs), keep the
last N turns verbatim, append the `compact` event, resume on briefing + tail. One
visible line in the chat says so: *"Resumed from summary — full transcript in
History."* The full verbatim history remains on disk and in the History view;
only the model's working context is summarized. **This is the honest version of
"save by summarizing": summarize to *fit*, never to *store*.*

Cost note: tier 3 costs one summarization call on the user's key/plan — the UI says
so before running it when the estimated input exceeds a threshold (default 50k
tokens), with "Resume from summary" / "Start fresh instead" choices.

### Pending work at switch time
- **Keep/Undo reviews:** already survive independently; the session records which
eras it owns. Switching sessions with pending reviews keeps today's `newChat()`
behavior (finalize = keep files, drop UI) but says so in one status line.
- **Running agent:** switching aborts it (as `newChat()` does today); the abort is
recorded as an event so a resumed session shows *"(run interrupted)"* rather than
a silent cliff.
- **Background commands / MCP servers:** reaped, recorded as events. Never
auto-restarted on resume — the resumed chat *tells* the model what died via the
reload/interrupt events, so the agent re-establishes state deliberately.

### Retention
Defaults: keep everything (it is the user's disk, and text is small). Settings for
max sessions per project and max age; deletion from the History UI is per-session
(move to OS trash, not unlink, for one level of oops-protection).

## 6. UI (classic, minimal)

- **History** button in the chat header (clock icon) → in-webview list, newest first:
title · relative time · turn count · model. Click = resume; hover actions:
Rename, Delete, "Copy as Markdown".
- **New Chat** unchanged in placement; after it, a one-line toast: *"Previous chat
saved to History."* — teaches the feature exactly once (dismiss = never again).
- Command palette: `LevelCode: New Chat`, `LevelCode: Chat History`,
`LevelCode: Resume Last Chat` (the `--continue` analog), `LevelCode: Export Chat
as Markdown`.
- Multi-window: two windows on the same project each get their own live session;
the History list shows both. A session file is owned by one window at a time
(lockfile beside it, stale-lock timeout 30s) — the second window resuming the
same session gets a read-only "open a copy?" prompt. No merge semantics.

## 7. Settings

| Setting | Default | Meaning |
|---|---|---|
| `levelcode.ai.sessions.enabled` | `true` | master switch (off = today's ephemeral behavior) |
| `levelcode.ai.sessions.dir` | `~/.levelcode/sessions` | hackability: point it anywhere (a dotfiles repo, an encrypted volume) |
| `levelcode.ai.sessions.autoTitle` | `true` | cheap-lane titles; off = first-message truncation |
| `levelcode.ai.sessions.resumeBudgetPct` | `40` | share of the context window resume may fill |
| `levelcode.ai.sessions.confirmCompactOverTokens` | `50000` | ask before a paid compact-on-resume |
| `levelcode.ai.sessions.maxPerProject` / `maxAgeDays` | `0` (unlimited) | retention |

## 8. Implementation phases

**Phase 1 — persistence spine** *(M)*
`sessionStore.js` (new, pure Node — unit-testable like `update.js`): slugging,
meta/append/read/scan/index, atomic index writes, lock files, schema versioning.
Wire `conversation`/`agentMessages`/checkpoint boundaries into per-turn appends;
live-session id in `workspaceState`; reload replays. *Exit test: kill -9 the editor
mid-turn; reopen; the session lists and resumes with at most the in-flight turn
missing.*

**Phase 2 — History UI + New Chat sealing** *(M)*
Webview list + actions, toast, palette commands, rename/delete/export. `newChat()`
seals + rotates. *Exit test: three chats in a row; all three listed, titled (fallback
titles), resumable; delete works; folder rename in Finder → sessions still listed
(under the stored real path) and resumable.*

**Phase 3 — resume tiers + titles** *(M)*
Three-tier resume with `compactAgentMemory` reuse; async cheap-lane titles; the
paid-compact confirmation; interrupted-run/reload honesty lines. *Exit test: a 200k-
token stored session resumes into a 128k-window model via tier 3, the briefing chat
line appears, and the next agent turn acts on state only present in the summarized
head (proving the briefing carried it).*

**Phase 4 — polish** *(S)*
Markdown export, retention settings, multi-window locks, `sessions.dir` relocation,
docs page + walkthrough entry. *Exit test: EXIT-TEST.md additions all green.*

**Deliberately later:** M9 encrypted sync of `~/.levelcode/sessions` (same format —
this design is the sync payload); LevelLinks "share a run" (same format — a session
file is the replay source); cross-session memory ("what did we decide last week?" —
search over JSONL is trivially greppable, an agent tool over it is a natural S-size
follow-up).

## 9. Test plan (beyond exit tests)

- `test/sessionStore.test.js`: slug edge cases (unicode paths, root, UNC), append/
scan roundtrip, index self-heal from deliberate corruption, lock stealing after
timeout, schema `v` forward-refusal, cap-elision determinism.
- Resume-tier unit tests with a fake tokenizer: boundary math at exactly `B`,
compact-event incremental path, tool-pair integrity across the cut (reuses the
existing boundary-picking function — test it directly).
- Manual matrix in EXIT-TEST.md: crash, reload, rename-folder, two-window, BYOK vs
gateway title/compact costs surfaced correctly.

## 10. Risks, honestly

- **Transcripts contain code.** They already transit the model; at rest they are
plain files in the user's home directory, same trust class as the code itself.
Anything that later *shares* a session (LevelLinks) must scrub — that is that
feature's burden, recorded here so it is not forgotten.
- **Compact-on-resume costs money** and briefings lose nuance. Mitigations: verbatim
tier preferred, explicit confirmation over the threshold, full transcript always
kept, briefing visibly marked in the chat.
- **Two windows, one project** is the only real concurrency surface; the lockfile +
read-only fallback keeps it boring.
- **Index drift** is a solved non-risk by construction: scanning is the source of
truth, the index is a cache.
Back | FazBrowse Home | New Git URL