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What Castellan is / is not

Castellan is

  • A coordination runtime — pressure-field scheduler, typed blackboard, episode logs
  • A plugin harness boundary — CastellanPlugin::verify_goal drives the default castellan run loop
  • An in-tree multiplexer — NDJSON socket API + PTY panes (MUX)
  • A topology evolution loop — castellan evolve mutates wake maps from episodes
  • Governance-aware — castellan.toml hooks, tool pipeline, drift-check manifest

Default castellan run uses deterministic plugins (gridworld, shell). The scheduler wakes agents from substrate signals — not a manager LLM.

Castellan is not

  • A drop-in coding agent with dozens of model providers on the hot path
  • A wrapper around external harness binaries — Castellan is the coordination runtime
  • A meta-harness composition layer that shells out to opaque coding agents as black boxes
  • A workflow DSL — coordination is the pressure field, not hand-drawn graphs
  • A chat router — agent-to-agent NL handoffs are intentionally forbidden

Honest scope: Castellan optimizes multi-agent coordination geometry — scheduler ticks, pheromone deposits, topology evolution, and multiplexer panes. Vocabulary: Conventions. Landscape peers (for maintainers only): Frontier positioning.

Comparison snapshot

NeedCastellanTypical coding agent
Daily coding agentUse castellan acp or editor + MCPPrimary product
Multi-pane agentsIn-tree multiplexer + dashboardExternal tmux scripts
Topology evolutioncastellan evolve + archiveUsually out of scope
Stigmergy / pressure fieldCore schedulerUsually out of scope
Provider matrixOptional verify-path LLM onlyOften hot-path feature

Honest adoption path

NeedUse
Prove coordination thesiscastellan run, swarm-demo, meeting-sched benches in verify.sh
Editor integrationcastellan acp (stdio + prompt → engine)
External tool bridgecastellan mcp or castellan run --mcp
Remote mux panescastellan remote --plugin <name> with governance
Cursor / Claude daily driverPair Castellan multiplexer with agent hooks

Castellan deliberately does not chase coding-agent feature parity — coordination runtime and honest scope are the product.