a4s-context-expert (Claude Code plugin)

Jev-guided deterministic compaction for Claude Code. It replaces Claude's native /compact summary with a keep / truncate / drop transcript scored by TypeSafe Jev, and auto-compacts once the context window crosses a threshold — the Claude analog of Pi's pi-context-expert with trigger.mode: "auto".

This directory is the self-contained marketplace plugin. It bundles its own copy of the host-neutral core (core/), kept byte-identical to the canonical packages/context-expert/core/ by scripts/sync-core.mjs and anchored by the claude-bundle-parity test, because the marketplace installs only this directory.

What it does

• session.compact — runs the shared core over the live transcript. Jev scores each tool call/result; items below the keep threshold are dropped (calls) or truncated (results), the first message and the most recent N are pinned, and the rebuilt message array replaces the native summary. If the estimated reduction is below minReductionRatio, or anything fails, it falls back to the native summary via next(event) — a failure never degrades the session.
• turn.complete — the Jev-decided auto-compact trigger. It does not compact at a fixed percentage. Past a local floor (minimumContextRatio), and subject to a cooldown and an available credential, it asks Jev — with a text-free state — whether now is the ideal moment to compact, and acts only when Jev chooses compact. triggerMode controls what then happens: auto compacts, hint only suggests /compact, off disables it. This is the Claude analog of pi-context-expert's trigger.mode.

Credentials

The TypeSafe Jev key resolves, in order, from the plugin apiKey userConfig, then TYPESAFE_API_KEY, then the plugin settings env, and finally Pi's native credential provider (~/.pi/agent/auth.json → typesafe.key) — the source the A4S way-of-working sanctions (do_work.credentials). The key is read in-process only; it is never logged, written to disk, or copied elsewhere.

Install (from the A4S marketplace)

claude plugin marketplace add pablontiv/a4s
claude plugin install a4s-context-expert@a4s

Or load it directly from a checkout:

claude --plugin-dir packages/context-expert/adapters/claude

Configuration (userConfig)

| Key | Default | Meaning | | --- | --- | --- | | triggerMode | auto | auto (Jev decides, then compacts), hint (suggest /compact), or off. | | minimumContextRatio | 0.5 | Context-window fill (0..1) below which the trigger never asks Jev. | | minReductionRatio | 0.25 | Minimum estimated reduction to replace history; below it, native summary. | | keepThreshold | 0.5 | Minimum Jev probability to keep a tool call/result. | | preserveRecentMessages | 6 | Newest messages pinned from compaction. | | maxStateTokens / maxRequestTokens | 25000 / 30000 | Jev request token budgets. | | truncateHeadChars | 300 | Characters of a truncated tool result kept. | | model | jev-latest | TypeSafe Jev model. | | apiKey | — | TypeSafe key override (sensitive); otherwise resolved as above. |

To turn the auto-compact trigger off, set triggerMode to off.

Derived from fast-jev-compaction (MIT) — see NOTICE.