kanban-codex-lane

name	kanban-codex-lane
description	Use when a Mangaba Kanban worker wants to run Codex CLI as an isolated implementation lane while Mangaba keeps ownership of task lifecycle, reconciliation, testing, and handoff.
version	1.0.0
author	Mangaba Agent
license	MIT
metadata	{"mangaba":{"tags":["kanban","codex","worktrees","autonomous-agents","prediction-market-bot"],"related_skills":["kanban-worker","codex","mangaba-agent"]}}

Kanban Codex Lane

Overview

This skill defines the lightweight Mangaba+Codex dual-lane convention for Kanban workers. Mangaba is always the task owner: it calls kanban_show, decides whether Codex is appropriate, creates or selects an isolated workspace, starts and monitors Codex, reconciles any diff, runs verification, and writes the final kanban_complete or kanban_block handoff. Codex is an input lane only. Codex output is not a task completion signal, not a trusted reviewer, and not allowed to write durable Kanban state directly.

The convention exists so a Mangaba worker can use Codex for bounded implementation help without changing the dispatcher. The dispatcher must still spawn Mangaba workers. A worker may optionally spawn Codex inside its own run, then accept, partially accept, or reject the lane after independent review and tests.

When to Use

Use the Codex lane when all of these are true:

• The Kanban task is a coding, refactor, documentation, test, or mechanical migration task with clear acceptance criteria.
• A bounded diff can be evaluated by Mangaba in one run.
• The repo can be copied or checked out in an isolated git worktree/branch.
• Mangaba can run the relevant tests itself after Codex exits.
• The prompt can state all safety constraints and files that must not change.

Do not use the Codex lane when any of these are true:

• The task requires human judgment that is not already captured in the Kanban body.
• The worker lacks repo access, Codex auth, or time to reconcile the result.
• The change touches secrets, credential stores, private user data, or production order-entry systems.
• A small direct edit is faster and safer than spawning another agent.
• The task is research-only and should produce a written handoff rather than a diff.
• The worker would be tempted to mark Done based only on Codex self-report.

Ownership Rules

1. Mangaba owns the Kanban lifecycle. Codex must never call kanban_complete, kanban_block, kanban_create, gateway messaging, or any Mangaba board CLI as a substitute for the worker.
2. Mangaba owns final acceptance. Treat Codex commits/diffs as untrusted patches until reviewed and verified.
3. Mangaba owns test execution. Codex may run tests, but those runs are advisory; repeat required verification from Mangaba with the repo's canonical wrapper.
4. Mangaba owns safety. If Codex changes safety boundaries, risk gates, live trading behavior, or secrets handling, reject the lane even if tests pass.
5. Mangaba owns cleanup. Kill stuck Codex processes and remove temporary worktrees when they are no longer needed.

Required Worktree and Branch Pattern

Never run Codex directly in a shared dirty checkout. Use a branch/worktree name that ties the lane to the Kanban task and keeps untrusted edits isolated.

Recommended variables:

TASK_ID="${MANGABA_KANBAN_TASK:-t_manual}"
REPO="/path/to/repo"
BASE="$(git -C "$REPO" rev-parse --abbrev-ref HEAD)"
SAFE_TASK="$(printf '%s' "$TASK_ID" | tr -cd '[:alnum:]_-')"
BRANCH="codex/${SAFE_TASK}/$(date -u +%Y%m%d%H%M%S)"
WORKTREE="/tmp/${SAFE_TASK}-codex-lane"

Create the isolated lane:

git -C "$REPO" fetch --all --prune
git -C "$REPO" worktree add -b "$BRANCH" "$WORKTREE" "$BASE"
git -C "$WORKTREE" status --short --branch

If the current Kanban workspace is already an isolated git worktree created for this task, you may create a sibling Codex branch inside it only if git status --short is clean except for intentional Mangaba edits. Otherwise create a separate temporary worktree and cherry-pick or copy accepted commits back after reconciliation.

Cleanup after reconciliation:

git -C "$REPO" worktree remove "$WORKTREE"
git -C "$REPO" branch -D "$BRANCH"  # only after accepted commits were copied/cherry-picked or intentionally rejected

Keep the worktree if it is needed as an artifact for review; record it in codex_lane.artifacts and mention it in the handoff.

Codex Capability Checks

Run these before spawning Codex. Missing Codex is a normal reason to skip the lane, not a task blocker if Mangaba can do the task directly.

command -v codex
codex --version
codex features list | grep -i goals || true

If /goal support is required, enable or launch with the feature flag only after checking availability:

codex features enable goals || true
codex --enable goals --version

Authentication can be via OPENAI_API_KEY or the Codex CLI OAuth state (often ~/.codex/auth.json). Do not print token files. A missing OPENAI_API_KEY is not proof that auth is unavailable.

Mode Selection

Use codex exec for bounded one-shot edits where Codex should exit on its own:

terminal(
    command="codex exec --full-auto '$(cat /tmp/codex_prompt.md)'",
    workdir=WORKTREE,
    background=True,
    pty=True,
    notify_on_complete=True,
)

Use Codex /goal only for broader multi-step work that benefits from durable objective tracking. Launch interactively in a PTY/tmux session or with codex --enable goals if the feature is disabled by default. Keep the goal objective self-contained: repo path, task id, safety constraints, allowed scope, acceptance criteria, tests, and commit expectations.

Example /goal objective text to paste into Codex:

/goal Work in this repository only: <WORKTREE>. Task: <TASK_ID> <TITLE>.
Mangaba owns the Kanban lifecycle; do not call Mangaba kanban tools or messaging.
Create small commits on branch <BRANCH>. Follow the PMB safety constraints in the prompt.
Run the requested verification commands and report exact outputs. Stop after producing a diff and summary.

Do not use --yolo for prediction-market-bot or safety-sensitive repos. Prefer --full-auto inside the isolated worktree, then rely on Mangaba reconciliation.

Prompt Construction

Use the linked template at templates/pmb-codex-lane-prompt.md for prediction-market-bot work. For other repos, keep the same structure and replace the PMB-specific safety block with repo-specific invariants.

Every Codex prompt must include:

• task_id, title, and full Kanban acceptance criteria.
• Repo path, worktree path, branch name, and allowed file scope.
• Explicit statement: Mangaba owns Kanban lifecycle; Codex is an input lane only.
• Required output: concise summary, files changed, commits, tests run, and known risks.
• Prohibited actions: secrets access, external messaging, board mutation, unrelated refactors, dependency upgrades unless required.
• Verification commands Codex may run and commands Mangaba will run afterward.

For PMB, include these mandatory safety constraints verbatim:

PMB safety constraints:
- live-SIM is paper-only; do not add or enable live REST order entry.
- Never use market orders.
- Do not add execution crossing or bypass price/risk checks.
- Do not fake passive fills, fills, PnL, order states, or reconciliation evidence.
- Do not weaken risk gates, limits, kill switches, or fail-closed behavior.
- Keep research/selection outside the C++ hot path unless explicitly requested.
- Do not read, print, write, or require secrets/tokens/credentials.

Monitoring, Timeout, and Kill Behavior

Start long Codex lanes in the background with PTY and completion notification:

result = terminal(
    command="codex exec --full-auto '$(cat /tmp/codex_prompt.md)'",
    workdir=WORKTREE,
    background=True,
    pty=True,
    notify_on_complete=True,
)
session_id = result["session_id"]

Monitor without interfering:

process(action="poll", session_id=session_id)
process(action="log", session_id=session_id, limit=200)
process(action="wait", session_id=session_id, timeout=300)

Send a Kanban heartbeat every few minutes for lanes longer than two minutes, e.g. kanban_heartbeat(note="Codex lane running in <WORKTREE>; waiting for tests/diff").

Kill conditions:

• No useful output for the task's remaining runtime budget.
• Codex requests secrets, production credentials, or external permissions.
• Codex attempts to modify files outside the worktree.
• Codex starts unrelated rewrites or dependency churn.
• Codex is still running near the worker timeout and no safe partial artifact exists.

Kill command:

process(action="kill", session_id=session_id)

After kill, inspect git status --short, preserve useful patches only if safe, and record codex_lane.result: timed_out or rejected with a concrete rejected_reason.

Reconciliation Checklist

Mangaba must perform this checklist before accepting any Codex lane result:

• git -C <WORKTREE> status --short --branch shows only expected files.
• git -C <WORKTREE> diff --stat and git diff were reviewed by Mangaba.
• No secrets, credentials, generated caches, unrelated data, or local artifacts are included.
• PMB safety constraints were preserved: no live REST order entry, no market orders, no execution crossing, no fake passive fills/PnL, no risk-gate weakening, no secrets.
• Codex commits are small enough to cherry-pick or squash cleanly.
• Mangaba ran the canonical tests itself, using scripts/run_tests.sh for Mangaba Agent or the repo's documented wrapper for other repos.
• Any Codex-run tests are listed separately from Mangaba-run tests.
• Accepted commits/diffs were applied to the Mangaba-owned workspace/branch.
• Rejected or partial work has a concrete reason and artifact path if useful.

Acceptance outcomes:

• accepted: Codex diff/commits were reviewed, applied, and verified.
• partial: Some Codex work was accepted after edits or cherry-picks; rejected parts are documented.
• rejected: No Codex changes were accepted; reason is documented.
• timed_out: Codex exceeded the lane budget; useful artifacts may or may not exist.

kanban_complete Metadata Schema

Include this object under metadata.codex_lane for every task where the lane was considered. If Codex was not used, set used: false and explain why in rejected_reason or a sibling notes field.

{
  "codex_lane": {
    "used": true,
    "mode": "exec | goal | skipped",
    "worktree": "/absolute/path/to/codex/worktree",
    "branch": "codex/t_caa69668/20260508100000",
    "command": "codex exec --full-auto ...",
    "result": "accepted | rejected | partial | timed_out",
    "accepted_commits": ["<sha1>", "<sha2>"],
    "rejected_reason": "empty when fully accepted; otherwise concrete reason",
    "tests_run": [
      {"command": "scripts/run_tests.sh tests/tools/test_x.py", "exit_code": 0, "owner": 
           
    
     
  

For tasks that intentionally skip Codex:

{
  "codex_lane": {
    "used": false,
    "mode": "skipped",
    "worktree": null,
    "branch": null,
    "command": null,
    "result": "rejected",
    "accepted_commits": [],
    "rejected_reason": "Direct Mangaba edit was smaller and safer than spawning Codex.",
    "tests_run": [],
    "artifacts": []
  }
}

Common Pitfalls

1. Treating Codex self-report as verification. Always inspect the diff and rerun tests from Mangaba.
2. Running Codex in the user's dirty main checkout. Always isolate in a worktree/branch.
3. Letting Codex own Kanban. Codex may summarize progress, but Mangaba writes board state.
4. Forgetting PMB safety invariants in the prompt. Missing safety text is a lane setup failure.
5. Using /goal for quick edits. Prefer codex exec unless durable multi-step continuation is needed.
6. Killing a stuck lane without recording why. rejected_reason must explain the decision.
7. Accepting broad unrelated cleanup because tests pass. Reject or cherry-pick only the scoped changes.

Verification Checklist

• Codex was skipped or started only after command -v codex, codex --version, and optional goals feature checks.
• Codex ran only in an isolated worktree/branch.
• Prompt included task scope, ownership rules, PMB safety constraints when applicable, and verification commands.
• Mangaba reviewed git diff and safety-sensitive files.
• Mangaba ran canonical tests independently.
• kanban_complete.metadata.codex_lane follows the schema above.
• Temporary processes and unnecessary worktrees were cleaned up.