claude-shrink

claude-shrink

A Claude Code plugin for safe context shrinking. Audits loose ends, categorizes items, saves session context, and prepares the compact/clear command.

Usage

/claude-shrink:shrink [--doc] [--clear] [--force]
/claude-shrink:show-session-id

Skill	Description
shrink	Audit loose ends and prepare a compact/clear command
show-session-id	Report the current session-id from three sources for debugging

Flags for shrink:

Flag	Description
--doc	Include undocumented locked ends in audit
--clear	Use /clear instead of /compact
--force	Force /clear even if C items exist
--log	Force devlog write (requires DEVLOG_DIR)
--keep	Preserve session-context.md after compact/clear (debugging)

Installation

Register as a local plugin for testing:

claude --plugin-dir /path/to/claude-shrink

Known Limitations

${CLAUDE_CODE_TMPDIR} does not expand in Write() allowed-tools patterns when the environment variable is unset. The variable falls back to empty string rather than the /tmp default, causing a permission prompt when writing session-context.md and compact-instruction.txt. The allowed-tools declarations follow the documented API correctly — this is a Claude Code platform limitation. DCI scripts handle the fallback correctly via shell default syntax (${CLAUDE_CODE_TMPDIR:-/tmp}), but allowed-tools frontmatter has no equivalent mechanism.

Hooks cannot trigger slash commands. Hooks can react to events (inject context, block actions) but cannot invoke /compact, /clear, or other commands. The use case of auto-triggering shrink and compact on branch switch is not possible.

Prompt suggestions are not programmable. Claude Code's Tab-to-accept suggestions are auto-generated with no configuration API. Custom suggestions (e.g., suggest reading session context after shrink) cannot be implemented.

Concurrent same-repo sessions are supported via PID-keyed session-id distribution. The SessionStart hook writes ~/.claude/tmp/session-by-pid/<claude-pid> with the current session-id on every event source (startup, compact, clear, resume). Skill scripts walk the PPID chain to find the file written by their parent Claude process; the PID is globally unique so concurrent sessions cannot collide. Resolution order is env $SESSION_ID → PID file → mktemp suffix. The last resort suffix is isolated but not discoverable by the PreCompact hook without a breadcrumb file.

Claude Code only sources $CLAUDE_ENV_FILE on SessionStart:startup, so the env var stays correct across /compact (the session-id does not change) but goes stale after /clear and --resume. The PID file fallback covers those cases. Run /claude-shrink:show-session-id to inspect all three sources.