context-anchor
Pin the facts, decisions and constraints that must survive context compaction, and get them back word for word the moment a long session resumes.
Claude Code
Developer Tools
Open Source$ claude --plugin-dir ./context-anchor > /context-anchor:pin "don't touch the auth module, it's mid-refactor" pinned · 1 anchor in .claude/context-anchor/anchors.jsonl > /context-anchor:pin "staging DB is read-only until Friday" pinned · 2 anchors … 3h later, context compacted … context-anchor restored 2 pinned anchors: · don't touch the auth module, it's mid-refactor · staging DB is read-only until Friday
- slash commands
- 3
- lifecycle hooks
- 2
- licensed
- MIT
The idea
When a Claude Code session runs long, the transcript gets summarized to stay inside the context window. That's necessary, but summaries are lossy. A constraint stated early on, like "don't touch the auth module", "the deadline is Friday" or "we decided X, not Y", can be smoothed over or dropped.
context-anchor gives you an explicit way to pin something so it survives that boundary intact. Pinned anchors are re-injected as a reminder on the first turn after a compaction, instead of relying on the summary to have kept them.
What it does
Pin verbatim
/context-anchor:pin appends your text with a timestamp to a per-project anchors file. Nothing is paraphrased.
PreCompact hook
Fires right before compaction, flushes anchors to disk and logs the trigger and anchor count.
SessionStart re-injection
Fires when a session resumes after compaction and puts every pinned anchor back in view on the next turn.
Scoped to the project
Anchors live under the project directory, not a single session. List or clear them at any time.
How it works
- 01
Pin
State a constraint once with /context-anchor:pin.
- 02
Compact
The PreCompact hook persists anchors before the transcript is summarized.
- 03
Resume
The SessionStart hook re-injects them word for word after compaction.
Built with
- Claude Code
- Hooks
- Shell
- JSONL