Opcode

Zero-token execution layer for AI agents. Define workflows once, run them free forever — persistent, scheduled, deterministic. 6 MCP tools over SSE. Supports DAG-based execution, 6 step types (action, condition, loop, parallel, wait, reasoning), 26 built-in actions, ${{}} interpolation, reasoning nodes for human-in-the-loop decisions, and secret vault. Use when defining workflows, running templates, checking status, sending signals, querying workflow history, or visualizing DAGs.

Execution runtime for AI agents. You reason, OPCODE executes — zero tokens per run after the first define. Workflows persist across sessions, run on schedules, and coordinate multiple agents. Persistent SSE daemon: 1 server, N agents, 1 database. JSON-defined DAGs, level-by-level execution, automatic parallelism. 6 MCP tools over SSE (JSON-RPC).

Why use OPCODE instead of reasoning through each step yourself? Every repeated workflow burns tokens re-reasoning decisions you already made. OPCODE templates your reasoning once and executes it deterministically — zero inference cost, identical output every run, survives context resets.

Which Tool?

I want to...	Tool
Create/update a workflow template	opcode.define
Execute a workflow	opcode.run
Check status or pending decisions	opcode.status
Resolve a decision / cancel / retry	opcode.signal
List workflows, events, or templates	opcode.query
Visualize a workflow DAG	opcode.diagram

Quick Start

Install:

go install github.com/rendis/opcode/cmd/opcode@latest

First-time setup (writes config and starts daemon):

opcode install --listen-addr :4100 --vault-key "my-passphrase"

Restart after stop: OPCODE_VAULT_KEY="my-passphrase" opcode

MCP client configuration:

{
  "mcpServers": {
  "mcpServers": {
    "opcode": {
      "type": "sse",
      "url": "http://localhost:4100/sse"
    }
  }
}

Each agent self-identifies via agent_id in tool calls. Opcode auto-registers unknown agents. Choose a stable ID per agent (e.g., "content-writer", "deploy-bot").

Workflows survive restarts. On startup, orphaned active workflows become suspended. Query with opcode.query({ "resource": "workflows", "filter": { "status": "suspended" } }), then resume or cancel via opcode.signal.

See operations.md for full configuration, subcommands, SIGHUP hot-reload, security model, web panel, and benchmarks.

MCP Tools

opcode.define

Registers a reusable workflow template. Version auto-increments (v1, v2, v3...).

Param	Type	Required	Description
name	string	yes	Template name
definition	object	yes	Workflow definition (see below)
agent_id	string	yes	Defining agent ID
description	string	no	Template description
input_schema	object	no	JSON Schema for input validation
output_schema	object	no	JSON Schema for output validation
triggers	object	no	Trigger config (seeworkflow-schema.md)

Returns: { "name": "...", "version": "v1" }

opcode.run

Executes a workflow from a registered template.

Param	Type	Required	Description
template_name	string	yes	Template to execute
agent_id	string	yes	Initiating agent ID
version	string	no	Version (default: latest)
params	object	no	Input parameters

Returns:

{
  "workflow_id": "uuid",
  "status": "completed | suspended | failed",
  "output": { ... },
  "started_at": "RFC3339",
  "completed_at": "RFC3339",
  "steps": {
    "step-id": { "step_id": "...", "status": "completed", "output": {...}, "duration_ms": 42 }
  }
}

If status is "suspended", call opcode.status to see pending_decisions.

opcode.status

Gets workflow execution status.

Param	Type	Required	Description
workflow_id	string	yes	Workflow to query

Returns:

{
  "workflow_id": "uuid",
  "status": "suspended",
  "steps": { "step-id": { "status": "...", "output": {...} } },
  "pending_decisions": [
    {
      "id": "uuid",
      "step_id": "reason-step",
      "context": { "prompt": "...", "data": {...} },
      "options": [ { "id": "approve", "description": "Proceed" } ],
      "timeout_at": "RFC3339",
      "fallback": "reject",
      "status": "pending"
    }
  ],
  "events": [ ... ]
}

Workflow statuses: pending, active, suspended, completed, failed, cancelled.

opcode.signal

Sends a signal to a suspended workflow.

Param	Type	Required	Description
workflow_id	string	yes	Target workflow
signal_type	enum	yes	decision / data / cancel / retry / skip
payload	object	yes	Signal payload (see below)
step_id	string	no	Target step
agent_id	string	no	Signaling agent
reasoning	string	no	Agent's reasoning

Payload by signal type:

Signal	step_id	Payload	Behavior
decision	required	{ "choice": "<option_id>" }	Resolves decision, auto-resumes
data	optional	{ "key": "value", ... }	Injects data into workflow
cancel	no	{}	Cancels workflow
retry	required	{}	Retries failed step
skip	required	{}	Skips failed step

Returns (decision): { "ok": true, "resumed": true, "status": "completed", ... } Returns (other): { "ok": true, "workflow_id": "...", "signal_type": "..." }

opcode.query

Queries workflows, events, or templates.

Param	Type	Required	Description
resource	enum	yes	workflows / events / templates
filter	object	no	Filter criteria

Filter fields by resource:

Resource	Fields
workflows	status, agent_id, since (RFC3339), limit
events	workflow_id, step_id, event_type, since, limit
templates	name, agent_id, limit

Note: event queries require either event_type or workflow_id in filter.

Returns: { "<resource>": [...] } -- results wrapped in object keyed by resource type.

opcode.diagram

Generates a visual DAG diagram from a template or running workflow.

Param	Type	Required	Description
template_name	string	no*	Template to visualize (structure preview)
version	string	no	Template version (default: latest)
workflow_id	string	no*	Workflow to visualize (with runtime status)
format	enum	yes	ascii / mermaid / image
include_status	bool	no	Show runtime status overlay (default: true if workflow_id)

* One of template_name or workflow_id required.

• template_name -- preview DAG structure before execution
• workflow_id -- visualize with live step status
• format: "ascii" -- CLI-friendly text with box-drawing characters
• format: "mermaid" -- markdown-embeddable flowchart syntax
• format: "image" -- base64-encoded PNG for visual channels

Returns: { "format": "ascii", "diagram": "..." }

Workflow Definition

{
  "steps": [ ... ],
  "inputs": { "key": "value or ${{secrets.KEY}}" },
  "context": { "intent": "...", "notes": "..." },
  "timeout": "5m",
  "on_timeout": "fail | suspend | cancel",
  "on_complete": { /* step definition */ },
  "on_error": { /* step definition */ },
  "metadata": {}
}

Field	Type	Required	Description
steps	StepDefinition[]	yes	Workflow steps
inputs	object	no	Input parameters (supports ${{}})
context	object	no	Workflow context, accessible via ${{context.*}}
timeout	string	no	Workflow deadline (e.g.,"5m", "1h")
on_timeout	string	no	fail (default), suspend, cancel
on_complete	StepDefinition	no	Hook step after completion
on_error	StepDefinition	no	Hook step on workflow failure
metadata	object	no	Arbitrary metadata

Step Definition

{
  "id": "step-id",
  "type": "action | condition | loop | parallel | wait | reasoning",
  "action": "http.get",
  "params": { ... },
  "depends_on": ["other-step"],
  "condition": "CEL guard expression",
  "timeout": "30s",
  "retry": { "max": 3, "backoff": "exponential", "delay": "1s", "max_delay": "30s" },
  "on_error": { "strategy": "ignore | fail_workflow | fallback_step | retry", "fallback_step": "id" },
  "config": { /* type-specific */ }
}

type defaults to action. See workflow-schema.md for all config blocks.

Step Types

action (default)

Executes a registered action. Set action to the action name, params for input.

condition

Evaluates a CEL expression and branches.

{
  "id": "route",
  "type": "condition",
  "config": {
    "expression": "inputs.env",
    "branches": { "prod": [...], "staging": [...] },
    "default": [...]
  }
}

loop

Iterates over a collection or condition. Loop variables: ${{loop.item}}, ${{loop.index}}.

{
  "id": "process-items",
  "type": "loop",
  "config": {
    "mode": "for_each",
    "over": "[\"a\",\"b\",\"c\"]",
    "body": [
      {
        "id": "hash",
        "action": "crypto.hash",
        "params": { "data": "${{loop.item}}" }
      }
    ],
    "max_iter": 100
  }
}

Modes: for_each (iterate over), while (loop while condition true), until (loop until condition true).

parallel

Executes branches concurrently.

{
  "id": "fan-out",
  "type": "parallel",
  "config": {
    "mode": "all",
    "branches": [
      [{ "id": "a", "action": "http.get", "params": {...} }],
      [{ "id": "b", "action": "http.get", "params": {...} }]
    ]
  }
}

Modes: all (wait for all branches), race (first branch wins).

wait

Delays execution or waits for a named signal.

{ "id": "pause", "type": "wait", "config": { "duration": "5s" } }

reasoning

Suspends workflow for agent decision. Empty options = free-form (any choice accepted).

{
  "id": "review",
  "type": "reasoning",
  "config": {
    "prompt_context": "Review data and decide",
    "options": [
      { "id": "approve", "description": "Proceed" },
      { "id": "reject", "description": "Stop" }
    ],
    "data_inject": { "analysis": "steps.analyze.output" },
    "timeout": "1h",
    "fallback": "reject",
    "target_agent": ""
  }
}

Variable Interpolation

Syntax: ${{namespace.path}}

Namespace	Example	Available fields
steps	${{steps.fetch.output.body}}	<id>.output.*, <id>.status
inputs	${{inputs.api_key}}	Keys from params in opcode.run
workflow	${{workflow.run_id}}	run_id, name, template_name, template_version, agent_id
context	${{context.intent}}	Keys from context in workflow definition
secrets	${{secrets.DB_PASS}}	Keys stored in vault
loop	${{loop.item}}, ${{loop.index}}	item (current element), index (0-based)

Two-pass resolution: non-secrets first, then secrets via AES-256-GCM vault.

CEL gotcha: loop is a reserved word in CEL. Use iter.item / iter.index in CEL expressions. The ${{loop.item}} interpolation syntax is unaffected.

See expressions.md for CEL, GoJQ, Expr engine details.

Built-in Actions

Category	Actions
HTTP	http.request, http.get, http.post
Filesystem	fs.read, fs.write, fs.append, fs.delete, fs.list, fs.stat, fs.copy, fs.move
Shell	shell.exec
Crypto	crypto.hash, crypto.hmac, crypto.uuid
Assert	assert.equals, assert.contains, assert.matches, assert.schema
Expression	expr.eval
Workflow	workflow.run, workflow.emit, workflow.context, workflow.fail, workflow.log, workflow.notify

Quick reference (most-used actions):

• http.get: url (req), headers, timeout, fail_on_error_status -- output: { status_code, headers, body, duration_ms }

• shell.exec: command (req), args, stdin, timeout, env, workdir -- output: { stdout, stderr, exit_code, killed }

• fs.read: path (req), encoding -- output: { path, content, encoding, size }

• workflow.notify: message (req), data -- output: { notified: true/false } -- pushes real-time notification to agent via MCP SSE (best-effort)

• expr.eval: expression (req), data -- output: { result: <value> } -- evaluates Expr expression against workflow scope (steps, inputs, workflow, context)

See actions.md for full parameter specs of all 26 actions.

Scripting with shell.exec

shell.exec auto-parses JSON stdout. Convention: stdin=JSON, stdout=JSON, stderr=errors, non-zero exit=failure. Use stdout_raw for unprocessed text.

See patterns.md for language-specific templates (Bash, Python, Node, Go).

Reasoning Node Lifecycle

1. Workflow reaches a reasoning step

2. Executor creates PendingDecision, emits decision_requested event

3. Workflow status becomes suspended

4. Agent calls opcode.status to see pending decision with context and options

5. Agent resolves via opcode.signal:

   {
     "workflow_id": "...",
     "signal_type": "decision",
     "step_id": "reason-step",
     "payload": { "choice": "approve" }
   }
   

6. Workflow auto-resumes after signal

7. If timeout expires: fallback option auto-selected, or step fails if no fallback

Common Patterns

See patterns.md for full JSON examples: linear pipeline, conditional branching, for-each loop, parallel fan-out, human-in-the-loop, error recovery, sub-workflows, and MCP lifecycle.

Error Handling

Strategy	Behavior
ignore	Step skipped, workflow continues
fail_workflow	Entire workflow fails
fallback_step	Execute fallback step
retry	Defer to retry policy

Backoff: none, linear, exponential, constant. Non-retryable errors (validation, permission, assertion) are never retried.

See error-handling.md for circuit breakers, timeout interactions, error codes.

Performance

10-step parallel workflows complete in ~50µs, 500-step in ~2.4ms. The event store sustains ~15k appends/sec with <12% drop under 100 concurrent writers. Worker pool overhead is ~0.85µs/task (>1M tasks/sec at any pool size).

Full benchmark charts, per-scenario breakdowns, and methodology: docs/benchmarks.md.