Files

T

retoorandClaude Sonnet 5 9dbd1fe667 Add plexer subsystem, container test infra, and last-resort opencode box backend

- Plexer: always-active terminal multiplexing. NativePlexerController/
  TmuxPlexerController share one interface, chosen by which env var is
  already set (TAI_PLEXER_SOCKET vs TMUX_PANE); NativePlexerBackend is
  the pty.fork()-based wrapper (raw mode, SIGWINCH resize forwarding,
  a Unix-socket control protocol, continuous session logging, a
  Ctrl+A prefix key distinct from tmux's own Ctrl+B). Auto-wraps new
  interactive shells via a .bashrc hook mirroring the existing
  command-not-found install pattern, gated on $TMUX/$TAI_PLEXER_ACTIVE/
  a $HOME/.tai-no-plexer bypass. New plexer_send/read/type/status
  tools, env-gated on a detected controller.
- tests/container.py + docker-compose.yml + tests/docker/Dockerfile:
  a disposable podman/docker image for the tests that must never touch
  a real machine (installing the plexer hook into a real ~/.bashrc, a
  live tmux session). Required suite (test_seal.py, test_tai.py,
  tests/plexer.py, tests/bashrc.py) gates the result; tests/rag.py
  runs as best-effort since its real-LLM dependency can't be satisfied
  inside a disposable container with no nested engine.
- tests/bashrc.py: real end-to-end hook install + bash -i auto-wrap,
  anti-recursion, tmux-active skip, non-interactive skip, a live
  TmuxPlexerController test, and an install/uninstall round-trip.
- tests/plexer.py: NativePlexerBackend under a real pty, plus a
  dedicated robustness pass (file permissions, >64KB payload framing,
  a malformed control request, a genuine self-deadlock fix in the
  write-to-child path).
- tai_test.py: the shared async process-driving framework (pipe/pty
  transport, group-wide kill-and-reap, a StdinBridge for --interactive)
  both test files build on.
- ChatClient last-resort backend: when there's no local opencode CLI
  but the sandbox box is already running, install opencode into it
  (official Node tarball, not apt -- apt's nodejs/npm pull in
  webpack/babel/jest as transitive deps) and route through it instead
  of giving up. Only reachable after the first retry round already
  failed everything else; never creates the box itself. TmuxPlexerController.status()
  fixed to use `list-panes` instead of `display-message -p`, which
  silently fell back to the default pane instead of erroring against
  a dead target.
- Fix 4 pre-existing test_tai.py bugs surfaced by running it in a
  clean environment for the first time: two stale mock signatures
  (subprocess.run's stdout= kwarg, Chat.complete's deadline= kwarg),
  one $TMUX-dependent catalog assertion, one tty-dependent color
  assertion.
- research/: a sourced research archive (Source Dossier/Citation
  Card/Conclusion tiers) backing the above design decisions, with its
  own audit.py consistency checker.
- .gitignore: fix a blanket *.md rule that was about to silently drop
  the entire research/ archive from version control; add __pycache__/
  and the one-off debug transcript this session started from.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

2026-10-10 04:36:05 +02:00

3.0 KiB

Raw Permalink Blame History

2Q Cache Management Algorithm

Metadata

Field	Value
Institute	Molodetz Institute — Research & Retrieval Division
Subject	agent-memory-recency-tracking
Document type	Source Dossier
Tier	1
Source title	2Q Cache Management Algorithm
Source URL	https://arpit.substack.com/p/2q-cache-management-algorithm
Source publisher / author	Arpit (Substack newsletter), explaining Johnson & Shasha's 1994 VLDB paper
Source type	blog post (explainer of a primary paper)
Source date (published)	Unknown — not stated
Date researched	2026-10-09
Researched by	tai (agent), model: Claude Sonnet 5, on behalf of retoor
Research method	web search synthesis
Confidence	High
Status	Active

Summary

An accessible explainer of Johnson & Shasha's 1994 "2Q" buffer-replacement algorithm — a constant-overhead, no-tuning alternative to full LRU that influenced real database buffer-pool design, most notably PostgreSQL's.

Key findings

2Q answers whether a constant-overhead-per-access scheme can match LRU/2 page-replacement performance; the 1994 paper's answer is yes, with no tuning required.
The design splits the buffer into three structures: a main LRU queue for confirmed-hot pages, a first-in (probationary) queue for newly-seen pages, and a ghost queue that stores only the identifiers of recently-evicted pages (not their data).
A page enters the probationary queue on first access; if it's re-referenced while still represented in the ghost queue, it gets promoted into the main queue.
This design is specifically scan-resistant: a one-time sequential scan fills and drains the probationary queue without ever polluting the main hot-page queue.
Per the source, 2Q's simplicity and effectiveness influenced PostgreSQL's own buffer-management design.

Pros / strengths

O(1), constant-overhead-per-access, no tuning parameters — directly addresses the "speed is important" constraint behind this entire research task, as a possible template if tai ever needs a real eviction policy rather than just tracking.
Real production lineage (PostgreSQL) gives confidence this isn't just an academic curiosity.

Cons / limitations / caveats

2Q's own main-LRU-queue component is itself expensive to make concurrent under high contention — this is exactly the weakness that arxiv-2511-21958-clock2q-plus.md (Clock2Q+) sets out to fix by replacing that component with a CLOCK-style structure.
2Q is an eviction-policy design for buffer pools; tai is not (yet) building eviction at all, only tracking — so 2Q is background context for a possible future phase, not something applicable today.

Relevance to tai

Background/comparative context only for this research pass — explicitly not part of the current proposal (which is tracking-only, no eviction), but recorded here so a future eviction-policy decision doesn't have to rediscover 2Q as a candidate from scratch.

Changelog

Date	Change
2026-10-09	Initial dossier created.

3.0 KiB Raw Permalink Blame History