01
Decide.
Bring the goal, current state, and available tools. Router chooses a next step from that set.
pre_decisionThe decision layer for agent harnesses
Your agent.
A better
next move.
Give every tool call a little more direction. Harness Router chooses the next tool, uses the result, and keeps your agent moving.
Open sourcePython 3.11+MIT licensed
Current observation
The failing test points to src/parser.py.
Selected next toolread_file
0.93confidence
01 / The loop
A little direction. Every iteration.Good decisions
come full circle.
A tool result changes what your agent knows. Feed that observation into the next choice, and routing becomes part of the whole workflow.
02
Execute.
Your harness builds the arguments, checks its permissions, and carries out the tool call.
host harness03
Observe.
Turn the result into the next observation. Recompute the next tool as the task progresses.
post_tool_useNew observation. New decision.
Your harness keeps its planning, permissions, approvals, and execution policy.
02 / The decision stack
The right depth
for the next step.
Reuse a known choice. Ask Jev when tools overlap. Look ahead when downstream outcomes matter.
Inside the router01CacheReuse
A compatible state can reuse a previous decision. The hook cache includes the goal, observation, last action, and tool catalog.
same statecached choice
02JevChoose
Resolve a closed choice among available tools through OpenRouter. Large registries can be narrowed by category before selecting a tool.
available toolsnext tool
03MCTSLook ahead
Search a supplied, side-effect-free state graph when the first choice depends on later outcomes. Simulate the possibilities, then return the first action.
simulated pathsfirst action
MCTS is optional and needs a simulator. A fallback hands the choice back to the planner.
03 / Integrations
One router. Five ways in.A native place
in your workflow.
Each adapter works with the lifecycle its host exposes. Your tools and execution controls stay with the harness.
Codex
Prompt and result hooks precompute the next tool. Local validation can request a re-plan.
Native hooksSet upClaude Code
Discover native and MCP tools, then connect prompt, tool-result, and validation callbacks.
Native hooksSet upohmypi
Route from the live tool registry and expose the selected tool through the active tool set.
ExtensionSet upAntigravity
Use invocation and result callbacks to prepare decisions, then validate before execution.
Hooks + MCPSet upDeepSeek
Connect through the Codex hook bridge with a supplied tool catalog and current goal.
Hook bridgeSet upBuilding your own loop?
Call Router directly with the Python API, CLI, or MCP server.
Read the API guide04 / Get started
Python 3.11+ · OpenRouter API keyMake the connection.
Install the router, add your key, and connect the harness you use.
01 Install the router
Terminaluv tool install --force --with 'mcp>=2,<3' \
'git+https://github.com/Protocol-Lattice/harness-router.git@main'02 Set your provider key
export OPENROUTER_API_KEY="your-key"Make the key available to the harness process before starting a session.
03 Connect Codex
Git project rootcurl -fsSL https://raw.githubusercontent.com/Protocol-Lattice/harness-router/main/scripts/install_hook.py \
| python3 - --provider codexFinish installing the adapters
The current Codex and Claude Code installer also needs these two adapter files. Run this after installing the hook.
for hook in pre_decision stop; do
curl -fsSL "https://raw.githubusercontent.com/Protocol-Lattice/harness-router/main/.codex/hooks/${hook}.py" \
-o ".codex/hooks/${hook}.py"
doneStart a fresh Codex session
The startup hook discovers tools. Prompt and result callbacks then prepare the next choice for local validation.
Integration guideThe installer merges settings and backs up changed files. Add .harness-router/ to your project's .gitignore for shared session state.
Open source. Open possibilities.