opencode-active-context

Active Context Manager for OpenCode — model-driven context compression with a clean MIT implementation.

The model decides when and what to compress — not a hard limit.

Install

opencode plugin opencode-active-context@latest --global

Or add to your opencode config:

{
    "plugin": ["opencode-active-context@latest"]
}

Important: Disable OpenCode's built-in auto-compaction — ACM handles context management itself.

{ "compaction": { "auto": false } }

How It Works

ACM gives the model a compress tool. When context grows, the model compresses consumed ranges into summaries. The model is 100% responsible for deciding when and what to compress.

Tools

| Tool | Description | |------|-------------| | compress | Replace a contiguous message range with a summary block | | decompress | Restore a compressed block's original content | | search_context | Search compressed block summaries by keyword | | acm_status | Inspect context usage, compressible ranges, and block details | | acm_context_recap | System tool — injects compression summaries as tool-results |

Nudge System

When context grows beyond the threshold, ACM injects a nudge showing:

• Context usage breakdown (tool / summaries / text / code)
• Compressible ranges grouped by conversation turn
• Compression philosophy and HOW TO COMPRESS rules

The nudge frequency adapts to the model's context window (5% of limit, halved after first nudge if model doesn't compress).

Configuration

Config file: ~/.config/opencode/acm.jsonc

{
    "enabled": true,
    "debug": false,
    "notification": "detailed",
    "compress": {
        "permission": "allow",
        "maxContextLimit": "55%",
        "minContextLimit": "45%",
        "nudgeFrequency": 5,
        "protectedTools": ["skill"],
        "keepEmbedMaxChars": 2000,
        "maxSummaryLength": 10000,
        "minCompressRange": 2000
    },
    "gc": {
        "promotionThreshold": 5,
        "maxBlockAge": 15,
        "maxOldGenSummaryLength": 3000
    }
}

KEEP/REF Markers

Summaries can reference original content without retyping it:

• [[KEEP:m00065]] — auto-expanded to original message content inline (truncated to keepEmbedMaxChars)
• [[REF:m00065|description]] — compact link [→ m00065: description]

Commands

ACM provides an /acm slash command:

| Command | Description | |---------|-------------| | /acm context | Token usage breakdown | | /acm stats | Cumulative compression statistics |

Storage

| What | Path | |------|------| | State | $XDG_DATA_HOME/opencode/storage/plugin/acm/{sessionId}.json | | Config | ~/.config/opencode/acm.jsonc | | Logs | ~/.config/opencode/logs/acm/ |

License

MIT — see LICENSE.