bot/docs/tools/flow.md

title, summary, description, read_when

title	summary	description	read_when
Flow	Typed workflow runtime for Hanzo Bot with resumable approval gates.	Typed workflow runtime for Hanzo Bot — composable pipelines with approval gates.	You want deterministic multi-step workflows with explicit approvals You need to resume a workflow without re-running earlier steps

Flow

Flow is a workflow shell that lets Hanzo Bot run multi-step tool sequences as a single, deterministic operation with explicit approval checkpoints.

Hook

Your assistant can build the tools that manage itself. Ask for a workflow, and 30 minutes later you have a CLI plus pipelines that run as one call. Flow is the missing piece: deterministic pipelines, explicit approvals, and resumable state.

Why

Today, complex workflows require many back-and-forth tool calls. Each call costs tokens, and the LLM has to orchestrate every step. Flow moves that orchestration into a typed runtime:

• One call instead of many: Hanzo Bot runs one Flow tool call and gets a structured result.
• Approvals built in: Side effects (send email, post comment) halt the workflow until explicitly approved.
• Resumable: Halted workflows return a token; approve and resume without re-running everything.

Why a DSL instead of plain programs?

Flow is intentionally small. The goal is not "a new language," it's a predictable, AI-friendly pipeline spec with first-class approvals and resume tokens.

• Approve/resume is built in: A normal program can prompt a human, but it can’t pause and resume with a durable token without you inventing that runtime yourself.
• Determinism + auditability: Pipelines are data, so they’re easy to log, diff, replay, and review.
• Constrained surface for AI: A tiny grammar + JSON piping reduces “creative” code paths and makes validation realistic.
• Safety policy baked in: Timeouts, output caps, sandbox checks, and allowlists are enforced by the runtime, not each script.
• Still programmable: Each step can call any CLI or script. If you want JS/TS, generate .flow files from code.

How it works

Hanzo Bot launches the local flow CLI in tool mode and parses a JSON envelope from stdout. If the pipeline pauses for approval, the tool returns a resumeToken so you can continue later.

Pattern: small CLI + JSON pipes + approvals

Build tiny commands that speak JSON, then chain them into a single Flow call. (Example command names below — swap in your own.)

inbox list --json
inbox categorize --json
inbox apply --json

{
  "action": "run",
  "pipeline": "exec --json --shell 'inbox list --json' | exec --stdin json --shell 'inbox categorize --json' | exec --stdin json --shell 'inbox apply --json' | approve --preview-from-stdin --limit 5 --prompt 'Apply changes?'",
  "timeoutMs": 30000
}

If the pipeline requests approval, resume with the token:

{
  "action": "resume",
  "token": "<resumeToken>",
  "approve": true
}

AI triggers the workflow; Flow executes the steps. Approval gates keep side effects explicit and auditable.

Example: map input items into tool calls:

gog.gmail.search --query 'newer_than:1d' \
  | bot.invoke --tool message --action send --each --item-key message --args-json '{"provider":"telegram","to":"..."}'

JSON-only LLM steps (llm-task)

For workflows that need a structured LLM step, enable the optional llm-task plugin tool and call it from Flow. This keeps the workflow deterministic while still letting you classify/summarize/draft with a model.

Enable the tool:

{
  "plugins": {
    "entries": {
      "llm-task": { "enabled": true }
    }
  },
  "agents": {
    "list": [
      {
        "id": "main",
        "tools": { "allow": ["llm-task"] }
      }
    ]
  }
}

Use it in a pipeline:

bot.invoke --tool llm-task --action json --args-json '{
  "prompt": "Given the input email, return intent and draft.",
  "input": { "subject": "Hello", "body": "Can you help?" },
  "schema": {
    "type": "object",
    "properties": {
      "intent": { "type": "string" },
      "draft": { "type": "string" }
    },
    "required": ["intent", "draft"],
    "additionalProperties": false
  }
}'

See LLM Task for details and configuration options.

Workflow files (.flow)

Flow can run YAML/JSON workflow files with name, args, steps, env, condition, and approval fields. In Hanzo Bot tool calls, set pipeline to the file path.

name: inbox-triage
args:
  tag:
    default: "family"
steps:
  - id: collect
    command: inbox list --json
  - id: categorize
    command: inbox categorize --json
    stdin: $collect.stdout
  - id: approve
    command: inbox apply --approve
    stdin: $categorize.stdout
    approval: required
  - id: execute
    command: inbox apply --execute
    stdin: $categorize.stdout
    condition: $approve.approved

Notes:

• stdin: $step.stdout and stdin: $step.json pass a prior step’s output.
• condition (or when) can gate steps on $step.approved.

Install Flow

Install the Flow CLI on the same host that runs the Hanzo Bot Gateway (see the Flow repo), and ensure flow is on PATH. If you want to use a custom binary location, pass an absolute flowPath in the tool call.

Enable the tool

Flow is an optional plugin tool (not enabled by default).

Recommended (additive, safe):

{
  "tools": {
    "alsoAllow": ["flow"]
  }
}

Or per-agent:

{
  "agents": {
    "list": [
      {
        "id": "main",
        "tools": {
          "alsoAllow": ["flow"]
        }
      }
    ]
  }
}

Avoid using tools.allow: ["flow"] unless you intend to run in restrictive allowlist mode.

Note: allowlists are opt-in for optional plugins. If your allowlist only names plugin tools (like flow), Hanzo Bot keeps core tools enabled. To restrict core tools, include the core tools or groups you want in the allowlist too.

Example: Email triage

Without Flow:

User: "Check my email and draft replies"
→ hanzo-bot calls gmail.list
→ LLM summarizes
→ User: "draft replies to #2 and #5"
→ LLM drafts
→ User: "send #2"
→ hanzo-bot calls gmail.send
(repeat daily, no memory of what was triaged)

With Flow:

{
  "action": "run",
  "pipeline": "email.triage --limit 20",
  "timeoutMs": 30000
}

Returns a JSON envelope (truncated):

{
  "ok": true,
  "status": "needs_approval",
  "output": [{ "summary": "5 need replies, 2 need action" }],
  "requiresApproval": {
    "type": "approval_request",
    "prompt": "Send 2 draft replies?",
    "items": [],
    "resumeToken": "..."
  }
}

User approves → resume:

{
  "action": "resume",
  "token": "<resumeToken>",
  "approve": true
}

One workflow. Deterministic. Safe.

Tool parameters

run

Run a pipeline in tool mode.

{
  "action": "run",
  "pipeline": "gog.gmail.search --query 'newer_than:1d' | email.triage",
  "cwd": "/path/to/workspace",
  "timeoutMs": 30000,
  "maxStdoutBytes": 512000
}

Run a workflow file with args:

{
  "action": "run",
  "pipeline": "/path/to/inbox-triage.flow",
  "argsJson": "{\"tag\":\"family\"}"
}

resume

Continue a halted workflow after approval.

{
  "action": "resume",
  "token": "<resumeToken>",
  "approve": true
}

Optional inputs

• flowPath: Absolute path to the Flow binary (omit to use PATH).
• cwd: Working directory for the pipeline (defaults to the current process working directory).
• timeoutMs: Kill the subprocess if it exceeds this duration (default: 20000).
• maxStdoutBytes: Kill the subprocess if stdout exceeds this size (default: 512000).
• argsJson: JSON string passed to flow run --args-json (workflow files only).

Output envelope

Flow returns a JSON envelope with one of three statuses:

• ok → finished successfully
• needs_approval → paused; requiresApproval.resumeToken is required to resume
• cancelled → explicitly denied or cancelled

The tool surfaces the envelope in both content (pretty JSON) and details (raw object).

Approvals

If requiresApproval is present, inspect the prompt and decide:

• approve: true → resume and continue side effects
• approve: false → cancel and finalize the workflow

Use approve --preview-from-stdin --limit N to attach a JSON preview to approval requests without custom jq/heredoc glue. Resume tokens are now compact: Flow stores workflow resume state under its state dir and hands back a small token key.

OpenProse

OpenProse pairs well with Flow: use /prose to orchestrate multi-agent prep, then run a Flow pipeline for deterministic approvals. If a Prose program needs Flow, allow the flow tool for sub-agents via tools.subagents.tools. See OpenProse.

Safety

• Local subprocess only — no network calls from the plugin itself.
• No secrets — Flow doesn't manage OAuth; it calls Hanzo Bot tools that do.
• Sandbox-aware — disabled when the tool context is sandboxed.
• Hardened — flowPath must be absolute if specified; timeouts and output caps enforced.

Troubleshooting

• flow subprocess timed out → increase timeoutMs, or split a long pipeline.
• flow output exceeded maxStdoutBytes → raise maxStdoutBytes or reduce output size.
• flow returned invalid JSON → ensure the pipeline runs in tool mode and prints only JSON.
• flow failed (code …) → run the same pipeline in a terminal to inspect stderr.

Learn more

• Plugins
• Plugin tool authoring

Case study: community workflows

One public example: a “second brain” CLI + Flow pipelines that manage three Markdown vaults (personal, partner, shared). The CLI emits JSON for stats, inbox listings, and stale scans; Flow chains those commands into workflows like weekly-review, inbox-triage, memory-consolidation, and shared-task-sync, each with approval gates. AI handles judgment (categorization) when available and falls back to deterministic rules when not.

• Thread: https://x.com/plattenschieber/status/2014508656335770033
• Repo: https://github.com/bloomedai/brain-cli