Add PACE to an Existing Project

This tutorial walks you through adding PACE to a repository that already has production code. Unlike the Quickstart, which assumes a mostly greenfield setup, this path is for teams that want to run PACE sprints on top of existing work.

What makes an existing project different?

When you initialise PACE on an existing codebase, two things are different from a greenfield start:

1. SCRIBE already has material to work with. Your existing source files, README, CI workflows, and architecture docs give SCRIBE real facts to write into engineering.md, security.md, and devops.md. The context documents it produces will be specific and accurate from Day 1, rather than mostly stubs.

2. Your sprint plan targets features, not foundations. plan.yaml should describe work that builds on top of what already exists — new endpoints, extended functionality, refactored modules — not setting up project infrastructure that is already in place.

Step 1: Install PACE

Copy the pace/ directory and .github/workflows/pace.yml into your repository root. This is identical to the Quickstart:

cp -r pace-framework-starter/pace ./pace
cp -r pace-framework-starter/.github ./.github
cp -r pace-framework-starter/.pace ./.pace

Do not replace your existing src/, tests, CI workflows, or any application code.

Step 2: Configure pace.config.yaml

Open pace/pace.config.yaml and fill in the fields that describe your existing project:

product:
  name: "Payments API"
  description: >
    A REST API for processing card payments. Handles authorisation,
    capture, refunds, and webhook delivery. Python 3.12 / FastAPI.
  github_org: "my-org"

sprint:
  duration_days: 30

source:
  dirs:
    # List the directories FORGE is allowed to write into.
    # For an existing project, include only the directories you want PACE to modify.
    - name: "api"
      path: "src/api/"
      language: "Python"
      description: "FastAPI route handlers and middleware"
    - name: "services"
      path: "src/services/"
      language: "Python"
      description: "Business logic and external integrations"

  # Optional: point SCRIBE to an external documentation folder.
  # Useful if your team maintains architecture docs, ADRs, or product specs
  # outside the code repository (e.g. a separate docs repo or wiki export).
  # docs_dir: "../my-product-docs"
  docs_dir: null

tech:
  primary_language: "Python 3.12"
  ci_system: "GitHub Actions"
  test_command: "pytest -v --tb=short"
  build_command: null

platform:
  type: github

llm:
  provider: anthropic
  model: claude-sonnet-4-6

Scope FORGE’s access carefully

The source.dirs list controls where FORGE writes code. For existing projects, be explicit. If you only want PACE to extend src/api/, do not list src/core/ — FORGE will stay out of it.

Step 3: Point SCRIBE to your existing docs (optional)

If your team maintains product, architecture, or security documentation outside the code repo (a separate docs/ repo, a Notion export, an ADR folder), set docs_dir in pace.config.yaml:

source:
  docs_dir: "../my-product-docs"

SCRIBE will read from both the code repo and this folder when generating context documents. It specifically looks for files named:

Document	What SCRIBE looks for in docs_dir
product.md	Files with mvp, vision, persona, roadmap, strategy in the name
engineering.md	Files with architecture, tech_stack, api, contracts, adr
security.md	Files with security, threat, stride, compliance, audit
devops.md	Files with ci, deployment, devops, runbook, onboarding

The path can be relative (resolved from the repository root’s parent) or absolute.

Step 4: Run SCRIBE to generate context documents

SCRIBE runs automatically the first time the orchestrator runs (Day 1), but you can also trigger it manually before your first sprint to review what it produces:

cd pace
python -c "from agents.scribe import run_scribe; run_scribe()"

Review the four files SCRIBE writes to .pace/context/:

.pace/context/
  product.md      ← vision, personas, MVP scope, success metrics
  engineering.md  ← module map, tech stack, architecture, test patterns
  security.md     ← sensitive data inventory, threat model, security requirements
  devops.md       ← CI/CD topology, env vars, deployment, runbook

Read each file. If SCRIBE missed something important (a subtle security invariant, a non-obvious deployment step, a data-privacy constraint), edit the file directly. These are living documents — you own them and can edit them at any time. To regenerate a specific document from scratch, delete it and re-run the orchestrator.

Review security.md closely

SCRIBE generates security.md from what it can read in source files and docs. Sensitive invariants that live only in institutional knowledge — “we never log card numbers”, “all PII must stay in the EU region” — must be added manually. SENTINEL reads security.md on every day of the sprint.

Step 5: Write plan.yaml for your existing codebase

plan.yaml targets work that extends your existing system. Write targets that assume the current code is already there:

sprint:
  name: "Payments API — Sprint 4"
  goal: "Add webhook retry logic, refund partial-capture support, and rate-limit the authorisation endpoint"
  duration_days: 15

days:
  - day: 1
    target: "Add idempotency key support to POST /authorise — store keys in Redis with 24h TTL"
  - day: 2
    target: "Write integration tests for idempotency: duplicate request returns cached response"
  - day: 3
    target: "Add rate limiting to POST /authorise: 100 req/min per API key using slowapi"
  - day: 4
    target: "Implement webhook retry queue: exponential backoff, max 5 attempts, dead-letter after final failure"
  - day: 5
    theme: "Mid-sprint advisory clearance"
    human_gate: false
    target: "Clearance day — resolve all open SENTINEL and CONDUIT advisories"
  - day: 6
    target: "Add partial-capture refund: allow refunding less than the captured amount"
  ...

Note that Day 1 says “add idempotency key support to POST /authorise” — it assumes the route already exists. PRIME will read engineering.md to understand where the route lives before generating the story card. FORGE will read it to know which file to modify.

Step 6: Handle your existing CI with CONDUIT

CONDUIT reviews your CI/CD configuration on every day. If your existing CI has patterns it flags (pinned to @master, missing dependency caching, test steps that aren’t pinned), it will raise advisories. On Day 1 this may generate several findings about pre-existing issues.

This is intentional. You can handle them in one of two ways:

1. Fix them on Day 1 before running PACE — run through your CI config and address any obvious pinning or configuration issues first.
2. Let them accumulate to the first clearance day — CONDUIT advisories are non-blocking. They’ll appear in the advisory backlog and must be cleared on the clearance day (every 7th day by default, or any day you mark in plan.yaml).

Step 7: Run Day 1

Set the required environment variables and trigger the workflow:

# Locally
PACE_DAY=1 ANTHROPIC_API_KEY=your-key python pace/orchestrator.py

# Or push to main to trigger .github/workflows/pace.yml
# (set ANTHROPIC_API_KEY in repository secrets)

On Day 1, the orchestrator will:

1. Preflight: check for context documents. Since this is Day 1, SCRIBE runs (unless you already ran it manually in Step 4).
2. PRIME: read product.md and the sprint plan to generate a story card for Day 1’s target.
3. FORGE: read engineering.md to understand the module map, then implement the story using a tool-calling loop.
4. GATE: run your existing test suite (tech.test_command) and evaluate each acceptance criterion.
5. SENTINEL: review the implementation against security.md.
6. CONDUIT: review CI configuration against devops.md.

Regenerating context documents mid-sprint

You can force SCRIBE to regenerate any context document at any time:

# Regenerate engineering.md after a significant refactor
rm .pace/context/engineering.md
PACE_DAY=<next-day> python pace/orchestrator.py
# SCRIBE runs automatically during preflight

Or regenerate all four documents:

rm .pace/context/*.md
python -c "from agents.scribe import run_scribe; run_scribe()"

Regenerating context does not reset the sprint or advisory backlog — only the context documents are affected.

Common issues on existing projects

FORGE modifies the wrong files. Tighten source.dirs in pace.config.yaml to restrict FORGE’s working directory to only the areas you want it to touch.

GATE fails because the test suite is slow or requires services. Set a focused test_command that runs only the tests relevant to the sprint (e.g. pytest tests/api/ -v --tb=short). Full integration tests that require a running database should be in a separate CI step, not the one GATE evaluates.

SCRIBE generates generic sections for security.md because there are no security docs. Edit .pace/context/security.md manually and add your actual threat model. SENTINEL uses this file to calibrate what it checks.

CONDUIT flags many pre-existing CI issues on Day 1. Either fix them before starting (recommended) or accept that they’ll accumulate as advisories and be force-cleared on your first clearance day.