@middlendian/omp-context-mode-extension

An oh-my-pi (OMP) extension that integrates context-mode — saving up to 98% of your context window through sandboxed execution and session continuity across compactions.

What it does

| Feature | How it works in OMP | |---------|---------------------| | Sandboxed execution | Spawns the context-mode MCP server; registers ctx_execute, ctx_batch_execute, ctx_execute_file, ctx_index, ctx_search, ctx_fetch_and_index, ctx_stats, ctx_doctor, ctx_upgrade as native OMP tools | | Routing enforcement | tool_call handler blocks raw curl/wget/WebFetch and redirects them to sandbox tools | | Session continuity | session_start / session_before_compact handlers persist events to SQLite and restore a prioritised snapshot after context compaction | | User prompt capture | input handler records each user turn (decisions, corrections) for retrieval via ctx_search | | Per-tool guidance | Injects context hints on Read and Grep tool calls, steering the model toward sandbox alternatives | | Sub-agent routing | Patches agent/task prompts to include routing instructions so child agents also use sandbox tools |

Requirements

• oh-my-pi installed (npm install -g @oh-my-pi/pi-coding-agent)
• Node.js ≥ 18 (for npm install / npm run build)
• context-mode reachable via npx (installed automatically on first use)

Installation

Option A — from npm (recommended)

npm install -g @middlendian/omp-context-mode-extension

The postinstall script automatically creates ~/.omp/agent/extensions/omp-context-mode-extension → <global-package-dir>.

Option B — from source

git clone https://github.com/middlendian/omp-context-mode-extension
cd omp-context-mode-extension
npm install && npm run build

The postinstall script creates .omp/extensions/omp-context-mode-extension inside the cloned directory, so OMP will auto-discover it when run from there.

For a single session only, use the -e flag instead:

omp -e ./dist/index.js

Option C — project-level (per-repo)

git clone https://github.com/middlendian/omp-context-mode-extension .omp/extensions/context-mode
cd .omp/extensions/context-mode
npm install && npm run build

The postinstall script creates .omp/extensions/omp-context-mode-extension in the parent project. OMP auto-discovers all extensions under <cwd>/.omp/extensions/.

Verifying the installation

Start OMP and run /extensions to open the Extension Control Center. The omp-context-mode-extension entry should appear with a green enabled indicator. If it is missing, check that the symlink target exists and that dist/index.js is present (npm run build if not).

Skipping the postinstall script: npm install --ignore-scripts will bypass the symlink creation; run the manual ln -sf from Option B above in that case.

How it integrates with context-mode

The extension uses the MCP server from context-mode as-is — it is spawned as a subprocess via npx context-mode over stdio. No patching or forking is required.

Session data (~/.claude/context-mode/sessions/<project-hash>.db) is shared between:

• The MCP server subprocess (reads/writes via ctx_stats, ctx_search, etc.)
• The OMP extension hooks (write events on tool calls, read snapshot on resume)

This means ctx_stats accurately reflects the savings achieved within OMP sessions, and ctx_search can retrieve the full event history.

Available tools (registered in OMP)

| Tool | Description | |------|-------------| | ctx_execute | Run code in 11 languages in a subprocess; only stdout enters context | | ctx_execute_file | Process a file in sandbox without exposing raw content | | ctx_batch_execute | Run multiple shell commands / search queries in one call | | ctx_index | Chunk markdown into FTS5 database with BM25 ranking | | ctx_search | Query indexed content with fuzzy fallback (stemming, trigram, Levenshtein) | | ctx_fetch_and_index | Fetch a URL, convert to markdown, chunk and index | | ctx_stats | Show context savings and session metrics | | ctx_doctor | Runtime diagnostics | | ctx_upgrade | Update context-mode to the latest version |

Session continuity

The extension tracks five event types in SQLite:

| Event | Captured from | |-------|--------------| | file_modified | Edit, Write, MultiEdit tool results | | git_operation | git commit/push/pull/merge in Bash results | | error | Error patterns in Bash output | | task | TodoWrite tool calls | | decision | User prompts containing corrections/decisions | | user_prompt | All non-system user messages |

Before compaction, a <2 KB XML snapshot is saved. When the session resumes, the snapshot is injected automatically so the model continues exactly where it left off.

Configuration

No configuration is required. The extension auto-initialises on session_start.

To disable specific routing rules (e.g., allow direct WebFetch), you can fork src/events/tool-call.ts and remove the relevant handler.

Development

npm install
npm run dev      # watch mode
npm run build    # one-time build

Project layout

src/
├── index.ts              # Extension factory (OMP entry point)
├── types.ts              # OMP ExtensionAPI type stubs
├── routing.ts            # ROUTING_BLOCK, per-tool guidance, snapshot builder
├── mcp-server.ts         # Spawns context-mode MCP, registers ctx_* tools
├── session/
│   ├── db.ts             # SQLite session DB (schema-compatible with context-mode)
│   └── helpers.ts        # Path helpers, project hash, session ID derivation
└── events/
    ├── session-start.ts  # session_start → inject routing/snapshot (SessionStart)
    ├── tool-call.ts      # tool_call → routing/blocking (PreToolUse)
    ├── tool-result.ts    # tool_result → event capture (PostToolUse)
    ├── pre-compact.ts    # session_before_compact → snapshot (PreCompact)
    └── user-input.ts     # input → prompt capture (UserPromptSubmit)

Licence

GPLv3 — see LICENSE.

context-mode is licensed under Elastic-2.0.