ystack

A small autonomous coding team. yshifu (the manager) runs the shop in a Claude Code session: you approve specs, and yshifu spawns a Claude coder subagent to build and runs a Codex reviewer to review.

Claude Code + Codex + GitHub are the current default profile, not product requirements. The portable target architecture and rollout live in ROADMAP.md.

This repo is the control plane — it defines how the team works. Target product code normally lives in separate repos; ystack is intentionally its own target when the team is improving the control plane itself.

ystack — Yihan's stack for the AI-native SDLC: an autonomous coding team, gated by human judgment.

Get started → QUICKSTART.md · Direction → ROADMAP.md

The current default team

You talk only to yshifu, in a Claude Code session. yshifu orchestrates the other roles within that session — spawning the coder and running the reviewer — so there is no separate human channel to the workers. Claude and Codex never talk directly; the PR is the message bus.

Agent	Vendor	How it runs	Writes?
yshifu (manager)	Claude	You talk to it in a Claude Code chat (manager/CLAUDE.md)	issues only; never authors code/PRs; never merges (labels merge-ready, hands the PR to you)
Coder	Claude	A subagent yshifu spawns with the issue/PR context — two modes: build (routines/coder.md) then fix (routines/coder-revision.md)	yes (branches, PRs)
Manager-reviewer	Codex (OpenAI)	yshifu runs scripts/manager-review.sh at plan altitude, before coding — debates a proactive issue vs. the north star → PROCEED/REFINE/DROP	veto only / read-only (never labels or merges)
Code-reviewer	Codex (OpenAI)	yshifu runs scripts/codex-review.sh at code altitude, after coding — against the PR diff	comments only / read-only

The loop

The loop is in-session: yshifu drives every step from one Claude Code chat. There is exactly one coder launch per cleared issue, one review path, and one revision path.

  one-liner → yshifu drafts spec → opens issue
                                       │
        gate (front gate = at the north-star altitude):
          • user-directed issue → your one-liner is the request → yshifu drafts
              the spec → YOU approve that drafted spec → yshifu labels it `ready`
              (drafting alone never earns `ready`)
          • proactive issue → yshifu⇄Codex manager-debate CONSENSUS
              → yshifu removes `debating`, labels it `ready` (no per-issue ask)
          (yshifu alone never self-approves; the consensus IS the gate
           for proactive north-star work — see manager-review.md)
                                       ↓
              yshifu spawns [Coder] subagent  → opens PR (label round-0)
                                       ↓
              yshifu runs scripts/codex-review.sh  → Codex posts comments only
                                       ↓
              yshifu spawns [Coder, fix mode]  adopt reasonable / push back
                                       │              (bump round-N)
                          ┌── round < 3 ┘
                          ↺  yshifu re-runs codex-review.sh
                          └── round = 3 (cap) → SCOPE DOWN + FOLLOW-UP (productive):
                                 land the converged core (one scoped-down change →
                                 clean review → `merge-ready` → YOU merge) + open a
                                 follow-up issue for the contested remainder; only a
                                 genuine standoff / safety-rail / north-star →
                                 label `needs-human` → pings YOU
                                       ↓
              CI green + Codex clean at that head → yshifu labels the PR `merge-ready`
                 and hands it to YOU → YOU merge (yshifu never merges; a status scan
                 or brief only reports). New commits void `merge-ready` — re-review first.
                 (high-risk / escalations / rail changes / north-star → named at handoff)

Design decisions (the "why")

• Responsibilities are stable; adapters are replaceable. Add a role only for a distinct job + trigger + tool surface — not per discipline. The current profile maps those responsibilities to Claude and Codex.
• Cross-vendor review is a preference, not a requirement. The requirement is an independent reviewer identity, context, and permission boundary. A different vendor is the preferred default because it can reduce common blind spots.
• Reviewer is read-only, comments only, never the author. Non-negotiable.
• Judgment lives at the direction (front gate at the north-star altitude), not the diff. You approve the north star — each target repo's own committed .ystack/north-star.md (when the target is this control-plane repo, that file is the root NORTH_STAR.md — ystack is its own target) — and yshifu pursues it autonomously — you stop reading diffs line by line (you still merge every PR, but on the strength of merge-ready), and for proactive work you stop approving each issue. Two paths clear an issue to run: a user-directed issue where your one-liner is the request — yshifu drafts the spec, you still approve that drafted spec, and that approval is the gate yshifu records with ready (drafting alone does not earn ready; user-directed issues are not exempt from per-spec approval); a proactive issue on yshifu⇄Codex manager-debate consensus — on consensus yshifu removes debating and applies ready itself, no per-issue ask (this is the only path with no per-issue approval, and it is conditional on your having explicitly approved the active north star). yshifu acting alone never self-approves; for proactive north-star work the cross-vendor consensus is the gate (see reviewer/manager-review.md). For proactive work you are pulled back in only at the north-star altitude: north-star achieved, goal drift / transition, and needs-human escalations — user-directed issues still come to you for the drafted-spec approval. The accepted roadmap adds a risk-tiered plan gate after intake: high-risk proactive or user-directed work will return to you for plan approval before code. That gate is not wired into the current manager yet; ready must not be described as plan approval.
• CI is the hard gate — ground truth. Autonomy rests on tests first, diverse reviewer second.
• yshifu never merges — it labels, then hands you the PR. Merging is the operator's, always. main's branch ruleset requires a pull request plus one approving review, the Codex reviewer is comments-only and never approves, and no agent has a bypass — so there is no agent merge path at all. What yshifu does instead: when a PR's current head is CI-green and the reviewer passed that same head, yshifu applies merge-ready — a label that means only "this head passed Codex review" — and hands the PR to you, naming anything you should weigh. You merge. merge-ready is void the moment new commits land: GitHub keeps the label across a head change, so yshifu clears it, re-runs codex-review.sh on the new head, and re-applies it only on a fresh pass — a stale label is a false green. A later status/Tracking scan and the brief only surface merge-ready PRs (read-only) — they never merge either. High-risk PRs are handed over with the risk named even when CI-green and Codex-clean (auth, DB/schema migrations, shared/production repos, security-sensitive or other operator-judgment changes); merge-ready records a clean review, it never means "merge without looking." Gate-creating bootstrap PRs get no merge-ready at all — an "add PR CI" PR or a greenfield 0→1 scaffold creates the gate, so no real gate yet exists to certify it, and the new workflow can self-report green on its own PR; you approve and merge those by hand. You're also brought in for needs-human/round-cap escalations, safety-rail changes, and north-star milestones / goal drift. scripts/merge-pr.sh stays in the repo for your own use — it reads the reviewed head+base SHAs from the authenticated codex-review.sh marker and refuses if either moved, gates on the base branch's required status checks (falling back to ≥1 real passing CI check with none failing when none are defined — optional checks like preview deploys are informational), refuses a PR that still needs an approving review (reviewDecision=REVIEW_REQUIRED), stays scoped to the target repo, and merges with a repo-permitted method (squash if allowed) pinned via --match-head-commit. yshifu never runs it, on any PR.
• One rounds counter (~3), and the cap is productive. Comments resolved or disagreement burned both count; a single push-back doesn't escalate. At the ~3-round cap yshifu scopes down + splits rather than dead-ending: land the part the reviewer is satisfied with (one scoped-down final change → clean review → merge-ready → you merge the core) and open a follow-up issue for the contested remainder (logged, not lost). needs-human is reserved for when even the scoped-down core is contested, it's a genuine coder↔reviewer standoff, or it's a safety-rail / north-star decision — only then does the cap reach you. The cap count is unchanged; only how it resolves.
• The current profile projects state into labels, not memory. Each coder is a fresh subagent, so round-0..3, needs-human, and merge-ready currently survive in forge labels. The portable core moves canonical stage, retry, stale, and decision state into durable records; labels remain a UI projection rather than a second state machine.
• Runs on the plan in an ordinary Claude Code session (Claude coder subagents) plus Codex's built-in review via scripts/codex-review.sh — compliant ordinary use, metered. Prototype on personal repos; apply terms diligence before any work/shared repo.

Autonomous write is paused for re-planning. The artifact spine is useful, but draft PR #146 bound the lane to one harness/forge and exposed missing credential, eval, and reconciliation controls. It must not merge. The portable core and control foundation in ROADMAP.md come before any autonomous write is enabled.

Model policy

Spend by leverage, not by volume. A run touches far more producer tokens (the coder writing code) than gate tokens (a reviewer judging a diff), so naively giving everything the same model either overspends on volume or underspends on judgment. ystack instead routes by the leverage of the decision, not by how much text it produces:

• Gates decide → always max. The code-review gate (scripts/codex-review.sh) and the manager-debate gate (scripts/manager-review.sh) run at maximum reasoning effort, always — there is no per-task/class routing that would lower them. A bad gate call (approving a broken PR, debating a proposal against the wrong bar) is expensive to unwind later, so gates never get a cheaper tier.
• Producers type → fixed ceilings. The coder subagent and "hands" work (mechanical, low-judgment steps) run at a fixed model ceiling, set once and never escalated at runtime — not even when a task looks hard. A task that seems to need a bigger model is a signal to decompose the task or fix the spec upstream, not to reach for more horsepower mid-run. Producer volume is what makes cost add up, so this is where the fixed ceiling lives.
• Frontier thinks, never types. The most capable models are reserved for judgment (gates), not generation (producers) — the opposite of routing by output volume.

Config: config/models.conf. Shell-sourceable (POSIX KEY=value, no bashisms) shipped defaults, read by any script here via . config/models.conf:

Key	Default	Meaning
YSTACK_CODER_MODEL	sonnet	Claude coder subagent model. A floating alias tracks that alias's latest release; a full model ID pins an exact snapshot. Fixed ceiling by design — never escalated at runtime.
YSTACK_HANDS_MODEL	haiku	Model for mechanical "hands" work. Same never-escalated principle, cheaper ceiling.
YSTACK_CODEX_MODEL	(empty)	Codex model for the review/debate gates. Empty means inherit the operator's Codex CLI / ~/.codex/config.toml default (whatever frontier codex that resolves to). Set only to pin a specific model — gates are never downgraded by task class.
YSTACK_REVIEW_EFFORT	high	Reasoning effort for the code-review gate. Always max.
YSTACK_DEBATE_EFFORT	high	Reasoning effort for the manager-debate gate. Always max.

Per-target override. A target repo may commit its own .ystack/models.conf (same format, same keys — copy it from templates/.ystack/models.conf) to override the producer/model keys only (YSTACK_CODER_MODEL, YSTACK_HANDS_MODEL, YSTACK_CODEX_MODEL) for that repo — YSTACK_REVIEW_EFFORT / YSTACK_DEBATE_EFFORT are never target-overridable; a target can never lower or otherwise change its own review/debate gate. This mirrors where the north star lives (a target's own .ystack/ directory — see templates/.ystack/north-star.md and the "Judgment lives at the direction" design decision above), so both kinds of per-target committed state — the goal and the model policy — live in the same place, owned by the target repo, not the ystack control-plane clone. The review/debate gates (scripts/codex-review.sh / scripts/manager-review.sh) apply it after the shipped defaults, so it only needs to set the keys it wants to change, and it is a static per-repo commitment — set once and committed, never a per-task rescue. Because it is target-committed content, the gates parse it as data (scripts/lib/models-conf.sh) — never source/./eval it — and codex-review.sh reads it from the repo's gh-bound default branch (fetched fresh), never the untrusted PR head under review. scripts/doctor.sh check (k) validates the shipped defaults (config/models.conf present, sourceable, coder/hands values non-empty) and check (l) warns if CLAUDE_CODE_SUBAGENT_MODEL is set in the environment (it would silently override a per-spawn model argument).

Wiring status: foundation + gates + coder spawn + hands all wired. The review and manager-debate gates (scripts/codex-review.sh / scripts/manager-review.sh) already read config/models.conf (and a target's .ystack/models.conf override) to resolve the Codex model + reasoning effort for every run. The coder spawn reads this config too (#111): yshifu's own instructions (manager/CLAUDE.md / templates/yshifu-command.md) read config/models.conf, then a target's committed .ystack/models.conf override if present, before every coder spawn (round-0 or fix-mode), and pass the resolved YSTACK_CODER_MODEL as an explicit model parameter — a fixed ceiling, never escalated at runtime, including on a bounced review round (see the bounce protocol in manager/CLAUDE.md, which replaces any notion of mid-round model escalation). The hands-work ceiling (YSTACK_HANDS_MODEL) is now wired too (#112): yshifu's instructions describe a delegation policy — context-heavy reads and multi-step polling (watching CI to completion, PR-diff summaries, review-thread collection, bulk gh queries) go to a YSTACK_HANDS_MODEL subagent via the same config-resolution mechanism, passed as the spawn's model parameter, while single quick writes (one comment, one label, one short handoff note) stay inline; hands agents must return key raw lines plus a summary, never a bare conclusion, so yshifu's decisions rest on evidence. This is a prompt-level wiring: it takes effect once scripts/install.sh regenerates the live /yshifu command, not merely by merging the doc change — doctor.sh's static validation is unaffected.

Layout

QUICKSTART.md              The ~10-min golden path: stand the team up from scratch
ROADMAP.md                 Portable architecture, control objectives, and rollout order
CLAUDE.md                  Repo conventions + self-modification safety rails (vs manager/CLAUDE.md = yshifu's persona)
manager/CLAUDE.md          yshifu's persistent role (paste into Claude Code)
routines/coder.md          Coder baseline instructions yshifu passes to a spawned coder subagent
routines/coder-revision.md Coder fix-mode instructions (handle review feedback)
routines/brief.md          Brief instructions yshifu can run (resurfacing; not auto-scheduled)
reviewer/codex-review.md   Codex reviewer mechanism + in-session review loop
reviewer/manager-review.md Codex manager-reviewer mechanism (issue-as-bus): rounds + consensus / veto-only
scripts/install.sh         Generate the /yshifu command with a repo-derived path (idempotent)
scripts/codex-review.sh    Codex reviewer harness: post `codex exec review` to a PR, verbatim (stamps Reviewed-head: marker)
scripts/manager-review.sh  Codex manager-reviewer harness: debate a proposed issue vs. the north star, post the verdict to the issue verbatim
scripts/merge-pr.sh        Safe merge harness for the OPERATOR's own use (yshifu never runs it): SHA-pin to reviewed head + repo-scope + required-checks gate + review-required refuse, then merge (repo-permitted method)
scripts/setup-target-repo.sh  Bootstrap a target repo's loop labels (idempotent)
scripts/lib/north-star.sh  Resolver: returns the active target repo's committed .ystack/north-star.md (or root NORTH_STAR.md when ystack itself is the target)
scripts/doctor.sh          Read-only restore + readiness self-check (install, auth, restore-critical files, north star, model config, ...)
config/models.conf         Shipped model-tiering defaults (coder/hands ceilings, gate models/effort) — see "Model policy" below
templates/yshifu-command.md Template for the /yshifu command (path placeholder)
templates/target-CLAUDE.md Drop into each target repo (conventions + PR-size rule)
templates/.ystack/north-star.md  Template each target copies to .ystack/north-star.md as its own committed north star
templates/.ystack/models.conf  Template each target may copy to .ystack/models.conf to override specific model-tiering keys
templates/repo-setup.md    Labels + branch protection checklist
NORTH_STAR.md              This repo's own target north star + done-signal + log — the resolver returns it only when ystack itself is the target; other targets keep theirs in .ystack/north-star.md
RESTORE.md                 Disaster-recovery runbook: rebuild the team from this repo

Rollout

• Phase 1 — prove the in-session loop on one seeded target repo. Front gate held the judgment; merge was manual while the loop earned trust.
• Phase 2 — live: the loop runs end to end in-session, and you merge at the gate. yshifu labels a PR merge-ready when its current head is CI-green and the reviewer passed that same head, then hands the PR to you — naming the risk on high-risk work, and escalating needs-human/round-cap, safety-rail changes, and north-star milestones / goal drift. Both the brief and a status / Tracking pass are read-only — they surface merge-ready PRs, they never merge. No agent merges: main needs a pull request plus an approving review the comments-only reviewer cannot give, and no agent has a bypass.
• Next — migrate the current profile behind portable adapters, establish the control/eval/reconciliation foundation, then enable bounded writes one stage at a time. ROADMAP.md is authoritative. The merge gate does not widen — the operator merges in every phase.