specflo

Spec-driven software engineering for coding agents. specflo is a Python CLI plus a set of skills and hooks that give an AI agent a disciplined brainstorm -> spec -> plan -> execute loop, with every artifact (specs, plans, decisions, tasks) written to plain markdown on disk instead of living in the model's context window.

• State lives in files, not in the model's head. Phase state, validation gates, and one-task-at-a-time focus live in the CLI and on disk. That makes agentic development more reliable, and it makes real development practical with capable but smaller local models such as Qwen3.6 27B: the agent only has to reason about the next small, well-scoped, validated step, not hold an entire project in context.
• Multi-project by design. specflo tracks many projects in one repo with a single active project and switch-anytime, so a monorepo can carry several concurrent efforts without them stepping on each other. Each project keeps its own phase, artifacts, and resume checkpoint.
• Pluggable into any harness that can run a CLI and read markdown. Claude Code and pi are integrated out of the box (skills, session-start hook, a bundled pi extension); opencode and Hermes get the skills; anything else can drive the plain CLI.

specflo is built with itself: every feature since v0.1 has gone through its own brainstorm -> spec -> plan -> execute pipeline. The CHANGELOG is the development history. Pre-1.0, interfaces may still move; breaking changes are called out explicitly in the changelog.

Quick start

Requires Python 3.12+. Install from PyPI:

uv tool install specflo    # or: pipx install specflo / pip install specflo

Then set up the repo you want to work in:

specflo init             # scaffold .specflo/ config + the projects dir
specflo skills install   # install the workflow skills into your agent harness(es)
specflo hook install     # Claude Code: session-resume wiring (recommended)

That is the whole setup. Start your coding agent and say:

We use specflo here. Start a new specflo project for .

The brainstorm skill takes over - one question at a time, decisions recorded on disk - and hands off through spec and plan to task-by-task execution. Every step also works without an agent; see the command reference.

Using specflo with your agent

The installed skills make your agent able to drive specflo; a note in the project memory file (CLAUDE.md, AGENTS.md, ...) makes it routine. Paste:

## Development workflow

This repo uses specflo for feature development. Run `specflo guide` at the
start of a session to orient yourself; `specflo status` shows the active
project and phase. Features move through brainstorm -> spec -> plan -> execute
using the specflo skills, recording decisions, requirements, and tasks through
the specflo CLI rather than editing its artifacts by hand.

Prompts that map onto the workflow:

• "Start a new specflo project for X." - creates the project, opens the brainstorm.
• "continue" - after a fresh start or a context clear, resume from the checkpoint.
• "Where are we?" - the active project's phase and next step (specflo status).
• "Park this for now." / "Pick that back up." - shelve and resume a project.
• "Run it in auto mode." - explicit opt-in to an unattended run (see specflo auto).

specflo guide runs cold - before init, in any repo - and orients a fresh agent in one shot: what specflo is, the pipeline, the full command surface, and what to do next. When in doubt, tell your agent to run it.

The pipeline

Four phases, each gated by a validated artifact:

1. brainstorm - capture the idea; resolve open questions into recorded decisions (D-NN).
2. spec - synthesize testable requirements (REQ-NN), each traced to the decisions behind it.
3. plan - decompose into dependency-ordered tasks (T-NN), each with an acceptance criterion, a verify step, and the requirements it implements; optionally grouped into milestones (M-NN).
4. execute - work tasks one at a time; a reconcile gate confirms every task is done before the project completes.

specflo advance validates the current phase's artifact before moving on, so a hole in the spec stops the line early instead of surfacing mid-execution. Artifacts are plain markdown under docs/projects/<slug>/ (configurable):

$ specflo status
Project: Payment retries (payment-retries)
Dir:     docs/projects/payment-retries
Phase:   brainstorm
Next:    Brainstorm and research; capture decisions, then write the spec.
Resume:  specflo checkpoint

Clearing context is free at any point: checkpoint.md is rewritten after every state change, and specflo checkpoint prints the resume prompt that puts a fresh session back to work.

Command reference

Setup and orientation

• specflo --version - print the installed version and exit.
• specflo guide [--json] - orientation in one shot: what specflo is, the pipeline, the full command surface, and what to do next here. Runs cold (works before specflo init), so a fresh agent can get up to speed in any repo.
• specflo init - scaffold .specflo/config.yaml + the projects dir (default docs/projects/).

Projects

• specflo new <name> - create a project and make it active.
• specflo list [--json] - list all projects, marking the active one and its phase.
• specflo switch <name> - make another project active (by slug or name).
• specflo status [--json] - show the active project, its phase, and what's next.
• specflo shelve [<name>] [--reason ...] - set a project aside: status shelved, phase untouched.
• specflo resume [<name>] - pick a shelved project back up at the phase where it was paused.

Phase artifacts

• specflo brainstorm start [--json] - create (or locate) the active project's brainstorm.md.
• specflo decision add --text ... [--rationale ...] [--supersedes D-NN] - append a decision (D-NN) to the brainstorm.
• specflo spec start [--json] - create (or locate) the active project's spec.md.
• specflo requirement add --text ... --acceptance ... [--from D-NN] [--supersedes REQ-NN] - append a requirement (REQ-NN) to the spec.
• specflo plan start [--json] - create (or locate) the active project's plan.md.
• specflo task add --text ... --acceptance ... --verify ... --from REQ-NN [--from REQ-NN ...] [--depends-on T-NN ...] [--supersedes T-NN] - append a task (T-NN) to the plan. --from (repeatable, required) links to the requirement(s) the task implements; --depends-on (repeatable) declares execution ordering; --acceptance is a behavioural pass/fail criterion; --verify is the command or step to confirm it.
• specflo milestone add --text ... --exit ... [--exit ...] - append a milestone (M-NN) with its Exit checklist to the plan; milestone list and milestone show report rollup and the current milestone.
• specflo validate brainstorm|spec|plan [--json] - lint the phase's artifact and report readiness. The plan lint checks bidirectional REQ<->task coverage, that every task has acceptance + verification, and that dependencies resolve and are acyclic.

Working the plan

• specflo task start <T-NN> / task done <T-NN> - mark a task in_progress / done.
• specflo task block <T-NN> [--reason ...] / task reopen <T-NN> - mark a task blocked (optionally recording why) / return it to pending.
• specflo task list [--json] - all tasks with their progress state and the deps-aware next-actionable marker.
• specflo task show [<T-NN>] [--json] - a task's brief: acceptance criterion, cited requirements, and constraints. Defaults to the next actionable task.
• specflo validate execute [--json] - reconcile gate: confirms all tasks are done before the project can be completed.
• specflo advance [--json] - validate the current phase's artifact, then move the active project to the next phase (brainstorm -> spec -> plan -> execute).
• specflo reopen [<phase>] - the inverse of advance: move the phase pointer backward (bare reopen goes one phase back, reopen <phase> jumps to a named earlier phase). A pure pointer move; no artifact is rewritten.
• specflo checkpoint [--json] - print the active project's resume prompt (which phase, what to read, what to do next) and refresh checkpoint.md. The file is also rewritten automatically after every state-mutating command, so a freshly-cleared agent can jump back in with one command.

Session-start and unattended runs

• specflo hook reseed [--format text|claude] [--continue] - emit the clear-and-continue payload for the active project: a confirmation-gate directive (do not start work; present the checkpoint and ask whether to continue) followed by the verbatim checkpoint. Prints nothing for no active project. Always exits 0, reads no stdin, makes no network calls - safe to wire into a session-start hook unconditionally.
  • --format claude wraps the payload as Claude Code SessionStart JSON: the payload as additionalContext (re-grounds the agent) plus a user-visible systemMessage that tells you what to type to kick it off (Claude can't make the agent take a turn on its own). The default --format text stays portable plain text for any harness.
  • --continue swaps the confirmation gate for a direct carry out the next step now directive, and inlines the current task's brief - for a caller that cleared context on purpose and has already answered "keep going".
• specflo hook install - idempotently merge the SessionStart wiring into Claude Code's .claude/settings.json, preserving all existing content; a previously-installed (older) reseed entry is rewired in place rather than duplicated. The wiring calls specflo hook reseed --format claude on the startup, clear, and resume sources (compact excluded - its digest is retained).
• specflo hook print - print that same wiring as a JSON fragment on stdout (pipeable), either to merge into Claude Code's settings yourself or as a starting point to adapt for another harness (opencode, OpenAI Codex, ...); a stderr note marks it as a fragment and points at specflo hook install as the safe merge. pi needs no wiring - the bundled pi extension reseeds on its own (see The pi extension). (hook print --install remains as a deprecated alias of hook install.)
• specflo auto [--autonomy safe|autonomous|yolo] [--max-passes N] [--off|--on] [--json] - emit the auto-mode handoff payload: an explicit, per-invocation opt-in that starts or continues an unattended run from the current phase toward project completion, emitting a bootstrap directive (autonomy policy + guardrail stop-conditions) instead of the ask-first pause. specflo only prints the payload - it drives no loop, spawns no nested agent, and never clears context; the clear-and-reseed trigger is the outer harness's job. Strictly additive - the default hook reseed / checkpoint behavior is unchanged.
  • --autonomy sets how far it runs unattended: safe (the default) and autonomous stop and hand off on any irreversible or outbound step; yolo permits them. Overrides the .specflo config default.
  • --max-passes is a runaway backstop: each invocation counts as one pass in a durable per-project run-state file, and on reaching the cap (default 50) the run escalates to the human instead of continuing. Overrides the config default.
  • --off sets the durable kill switch (the next pass halts); --on clears it.
  • --json reports the pass as an object - its payload text, a boolean stop, and the reason that stopped it (kill-switch, pass-cap, stall, project-complete, or unavailable; null while the run continues) - so a machine caller reads loop control from the CLI instead of deciding it.

Harness integration

• specflo skills install|status|update|uninstall [--scope user|project] [--harness NAME[:SCOPE]] - install specflo's bundled workflow skills into the agent harnesses on your machine, and keep them current. See Skills.
• specflo extension install [--scope user|project] - install the bundled pi extension into pi's extension directory: ~/.pi/agent/extensions/specflo by default, ./.pi/extensions/specflo with --scope project. A plain local copy with a version stamp - no npm, no network - and pi discovers the directory on its own, so no pi settings are read or written. Re-run to update. See The pi extension.

Session-start integration (clear-and-continue)

An agent can't clear its own context or remember what to do across a /clear - the continuation must come from outside the conversation. specflo hook reseed is that bridge: install it once (specflo hook install), and on a fresh start, after a /clear, or when you resume a session, Claude Code reorients from the on-disk checkpoint and asks before resuming, so you never re-explain where you were. Because a SessionStart hook can re-ground the agent but cannot make it speak first, the wiring also surfaces a short visible systemMessage telling you what to type (e.g. continue) to start the hand-off.

The installed wiring is Claude Code's. The payload itself is portable: another harness (opencode, OpenAI Codex, ...) can call the plain-text specflo hook reseed from its own session-start mechanism and inject the output as context. pi is the exception - it needs no wiring at all, because the bundled pi extension injects the reseed itself (see The pi extension).

Security posture: the reseed injects only trusted local state - the checkpoint is derived read-only from the project's own artifacts, never from external or network input - so running it at session start is benign.

The pi extension

For the pi coding agent, specflo goes further than the hook: a bundled pi extension performs the clear itself. It is a thin driver by design - every piece of state it acts on is the stdout of a specflo command, it keeps no durable state of its own, registers no model-callable tool, and never blocks a tool call. Install it once (pi 0.81+):

specflo extension install                  # -> ~/.pi/agent/extensions/specflo
specflo extension install --scope project  # -> ./.pi/extensions/specflo

pi discovers the directory on its own - nothing else to wire. Re-running is safe: an up-to-date install is reported as current, a stale one is replaced whole.

In an attended pi session:

• Cold start. When pi starts or resumes inside a specflo repo, the first turn is seeded with the specflo hook reseed payload, so the agent already knows where the project stands and asks before resuming. With no active project it injects nothing.
• Arming. At each turn's end the extension reads pi's own context-usage percent and arms once it reaches context_threshold_percent (default 75, set in .specflo/config.yaml).
• The seam. While armed it watches specflo status --json for a safe point to clear: the phase advancing, or a task reaching done. A task merely in progress is never a seam, so in-flight work is never discarded.
• The notice. An armed seam produces one passive notice naming the current usage, the seam that fired, and the command to run. Nothing clears on its own in an attended session.
• /specflo-continue. Clears the session and reseeds the direct-continuation payload - the checkpoint plus the current task brief - so the fresh session carries straight on.

In an auto run:

• /specflo-continue auto starts or continues an unattended run from inside pi - the same explicit opt-in specflo auto is, counting a pass in the same run state - and delivers that pass's payload into a fresh session.
• The unattended fire. After one clear has run, every armed seam clears and reseeds by itself: the extension fetches the next specflo auto pass and delivers its payload verbatim. No dialog, no confirmation, no input.
• Joining a run cold. If the run was started outside pi (specflo auto in a terminal, then pi opened), the first armed seam prints a bootstrap notice asking you to type /specflo-continue auto once; every seam after that is unattended.
• Stopping. Loop control lives in the CLI, never the extension: on the kill switch (specflo auto --off), the pass cap, a stall, or project completion, nothing clears and the CLI's own stop directive is shown as a notice. specflo auto --on clears the kill switch again.

Skills

specflo ships its seven workflow skills inside the package and installs them into whatever agent harness it finds on your machine (Claude Code, pi, Hermes, opencode). Let the CLI do it - no copying or symlinking by hand:

specflo skills install     # into the user skills dir of every detected harness
specflo skills status      # what is installed, and whether it is current
specflo skills update      # bring stale installs up to the bundled version
specflo skills uninstall   # remove the ones specflo's stamp owns

On an interactive terminal, install asks which harnesses and scopes to use; pass --no-input (with --harness/--scope) to script it. Every verb takes --scope user|project - user (the default) is the harness's user-level skills dir such as ~/.claude/skills/, and project is the repo-local one such as ./.claude/skills/ - plus a repeatable --harness NAME[:SCOPE] to target one harness instead of all detected ones.

Each install is a plain copy carrying a specflo provenance stamp, so update and uninstall only ever touch skills specflo itself installed, and a skill you have edited locally is never overwritten without --force. When an installed skill falls behind the bundled version, any specflo command prints a single advisory line on stderr pointing at specflo skills update. It is notice-only: it never prompts, never updates anything, and never changes the exit code. Silence it by setting CI or AGENTSQUIRE_NO_UPDATE_CHECK.

The seven skills:

• brainstorm (skills/brainstorm/SKILL.md) - drives the brainstorm phase over the CLI above (one question at a time, captures decisions, validates, hands off to the spec phase).
• spec (skills/spec/SKILL.md) - drives the spec phase (synthesize testable REQ-NN requirements from the brainstorm, validate, hand off to the plan phase).
• plan (skills/plan/SKILL.md) - drives the plan phase (decompose the validated spec into dependency-ordered, testable T-NN tasks, validate, hand off to the execute phase).
• execute (skills/execute/SKILL.md) - drives the execute phase (work tasks one at a time with task show/task start/task done, validate with validate execute, complete the project with advance).
• research (skills/research/SKILL.md) - a research subagent the brainstorm skill dispatches to ground decisions in current facts: an upfront landscape scan (what tools/SDKs/clients/frameworks already exist) plus opportunistic assumption-checks. Wiki-integrated - searches the Agent Wiki first and saves findings back (soft dependency).
• shelve (skills/shelve/SKILL.md) - recognizes "park this for now" / "let's pick that back up" and maps them to specflo shelve and specflo resume, so a project can be set aside and reclaimed without losing its phase or artifacts.
• auto (skills/auto/SKILL.md) - recognizes an unattended-run intent ("auto mode", "autopilot", "keep going without me") and maps it to specflo auto, then follows the emitted payload. Thin by design: the CLI carries the loop, autonomy policy, and guardrails; the skill only triggers it and hands the directives to the loop.

Working on the skills themselves

If you are editing specflo's own skills from a checkout, symlink them instead so your edits take effect immediately. specflo recognizes a symlinked live-edit install and stays quiet about updates for it:

ln -s "$PWD/skills/brainstorm" ~/.claude/skills/brainstorm

Install from source

From a checkout, with uv installed (curl -LsSf https://astral.sh/uv/install.sh | sh):

uv tool install .              # install `specflo` globally, from the repo root
uv tool install --reinstall .  # update after pulling changes
uv tool uninstall specflo      # remove

pipx install . and pip install . work the same way if you prefer them.

To build distributables instead, uv build writes the wheel and sdist into dist/; install the wheel anywhere with uv tool install ./dist/specflo-<version>-py3-none-any.whl (no source checkout needed).

Development

uv sync                    # create the venv and install deps (incl. dev group)
uv run pytest              # run the tests
uv run specflo --help      # run the CLI without installing it

License

GPL-3.0-or-later. Copyright (C) 2026 TacoTakumi.