subagents-discipline

name	subagents-discipline
description	Core engineering principles for implementation tasks

Implementation Principles

Rule 0: Read the Bead First

Before implementing anything, read the bead comments for investigation context:

bd show {BEAD_ID}
bd comments {BEAD_ID}

The orchestrator has already:

• Investigated the issue using Grep, Read, Glob
• Found the root cause (specific file, function, line)
• Documented related files that may need changes
• Noted gotchas and edge cases

Use this context. Don't re-investigate. The comments contain everything you need to implement confidently.

If no investigation comments exist, ask the orchestrator to provide context before proceeding.

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Rule 1: Look Before You Code

Before writing code that touches external data (API, database, file, config):

1. Fetch/read the ACTUAL data - run the command, see the output
2. Note exact field names, types, formats - not what docs say, what you SEE
3. Code against what you observed - not what you assumed

WITHOUT looking first:
  Assumed: column is "reference_images"
  Reality: column is "reference_image_url"
  Result:  Query fails

WITH looking first:
  Ran: SELECT column_name FROM information_schema.columns WHERE table_name = 'assets';
  Saw: reference_image_url
  Coded against: reference_image_url
  Result: Works

Rule 2: Test Both Levels

Component test catches: logic bugs, edge cases, type errors Feature test catches: integration bugs, auth issues, data flow problems

You built	Component test	Feature test
API endpoint	curl returns 200	UI calls API, displays result
Database change	Migration runs	App reads/writes correctly
Frontend component	Renders, no errors	User can see and interact
Full-stack feature	Each piece works alone	End-to-end flow works

Rule 3: Use Your Tools

Before claiming you can't fully test:

1. Check what MCP servers you have access to - list available tools
2. If any tool can help verify the feature works, use it
3. Be resourceful - browser automation, database inspection, API testing tools

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For Epic Children

If your BEAD_ID contains a dot (e.g., BD-001.2), you're implementing part of a larger feature:

1. Check for design doc: bd show {EPIC_ID} --json | jq -r '.[0].design'
2. Read it if it exists - this is your contract
3. Match it exactly - same field names, same types, same shapes

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Red Flags - Stop and Verify

When you catch yourself thinking:

• "This should work..." → run it and see
• "I assume the field is..." → look at the actual data
• "I'll test it later..." → test it now
• "It's too simple to break..." → verify anyway