Modules

Every capability in HarnessWeaver is a module: a port (a typed interface), a default provider, the middleware it installs on hook points, and its section of the spec. Apps pick modules by writing their sections; modules pick providers with use:. Swapping a provider never changes the hook points, the trace or the rest of the spec.

Module	Spec section	Port(s)	Built-in and first-party providers	Planned	Hook points
Models	models	ModelProvider	scripted; plugins: openai.chat, anthropic.messages	Bedrock and Vertex through LiteLLM	model.*, stream.chunk
Routing	routing	Decider, Embedder	rules, lexical, semantic (with semantic.hashing), llm, any @hw.decider	semantic-router, RouteLLM	route.decide
Context and memory	context, memory	ContextProvider, Memory	memory, passthrough; in-process memory store	pgvector, OpenSearch, Qdrant	context.after
Guardrails	guardrails	Guardrail	pii.regex, secrets.scan, injection.heuristic, regex.deny, size.limit, topic.deny, grounded.citations, llm.judge	Presidio, Llama Guard, Prompt Guard	input.before, context.after, tool.after, output.before, stream.chunk
Validation	validation, tasks.*.output	-	Pydantic parsing with bounded repair, cel-lite business rules	groundedness scorers	output.before
Tools	tools, manifests	ToolBackend, ToolGovernor, Sandbox	Manifest registry, the nine-step governor, native, http and code transports; plugin: monty.sandbox	MCP transport	tool.before, tool.after
Policy	policy	PolicyEngine	cel_lite; plugin: cel.policy	Cedar, OPA, OpenFGA	tool.before, run.start
Approvals	approvals, tasks.*.approvals	ApprovalChannel	memory, callback, console, webhook	Slack, e-mail, an approval page	tool.before, output.before, approval.resolved
State and replay	state	StateStore	memory, sqlite	Postgres, Redis	run.*, approval.resolved
Observability	observability	Telemetry	OpenTelemetry API spans and metrics, the in-memory RunTrace; plugin: otel.sdk	Langfuse, Phoenix, Logfire exporters	all
Evals	evals	Evaluator	exact, field_equals, numeric_close, contains, regex, schema_valid, citation_present, guard_fired, status, llm_judge	promptfoo, DeepEval, Ragas	run.end

Two more pieces are part of the core rather than modules: budgets (Envelope, labels and budgets) and prompts (section reference).

Providers and determinism

Every provider declares whether it is deterministic (the same input always gives the same answer). This matters for trust: probabilistic components, such as LLM judges and semantic routers, may route a decision or tighten it (raise it to approval or block), but they never grant anything. A PolicyEngine must be deterministic (RULES R3).

Deterministic	Probabilistic
pii.regex, secrets.scan, injection.heuristic, regex.deny, size.limit, topic.deny, grounded.citations, cel_lite, rules, lexical, semantic (with the hashing embedder), the deterministic graders	llm.judge, the llm routing stage, the llm_judge grader

Writing your own

Any module's port can be implemented by a plugin, in your own repository, and selected with use: <namespace>.<name>. See Providers and ports.