Compactable tool whitelist gating

SKILL: Compactable Tool Whitelist Gating

Domain: microcompaction
Trigger: Apply when cache-editing compacts conversation transcripts and must avoid deleting outputs from tools that cannot be safely re-run or are non-text. Source Pattern: Distilled from reviewed session memory, compaction, and context-budgeting implementations.

Core Method

Define a fixed set of safe tools whose outputs can be trimmed via cached microcompact. Compose the set from shell tools, file read/write utilities, grep/glob/web fetch/search, and optionally other text-generating helpers. The microcompact path consults this set to decide whether to register a tool result for deletion, so no unsupported or stateful tools ever get silently mutated.

Key Rules

• Build the whitelist as a static Set once so permission checks stay fast and deterministic.
• Include only tools whose outputs are recoverable or purely text (shell commands, grep/glob, file read/write, fetch/search, etc.).
• Skip tools not on the list so cache edits never attempt to delete specialized state (APIs that mutate files, image tools, etc.).
• Document that new tools must be evaluated before being added to the whitelist to avoid breaking reads.
• Keep the set close to the microcompact path and highlight it in comments so the gating logic stays obvious.

Example Application

When cached microcompact inspects assistant messages, it only registers tool uses whose names appear in compactable tools, ensuring the summarizer never tries to delete non-text or stateful outputs like MCP connectors or tool search metadata.

Anti-Patterns (What NOT to do)

• Do not treat all tools equally—many produce binary or stateful outputs that cannot be safely recompiled from cache edits.
• Do not mutate the whitelist at runtime; it must remain a static, vetted guardrail for cached compaction.