library-worker

name	library-worker
description	Implements code changes in the Outfitter monorepo — bug fixes, utilities, testing primitives, refactors.

Library Worker

NOTE: Startup and cleanup are handled by worker-base. This skill defines the WORK PROCEDURE.

When to Use This Skill

Use for features that involve writing or modifying TypeScript code in the monorepo:

• Bug fixes in existing packages
• New utility functions and helpers
• Testing primitives and harnesses
• Refactors (e.g., centralizing logic, returning Result instead of throwing)

Work Procedure

1. Understand the Feature

• Read the feature description thoroughly — it references a Linear issue with specific requirements.
• Read AGENTS.md for mission boundaries, coding conventions, and key source files.
• Read the relevant source files listed in the feature's preconditions to understand existing code.
• Read .factory/library/architecture.md for cross-package patterns.

2. Write Failing Tests (Red Phase)

• Create or update test file at src/__tests__/<feature>.test.ts in the relevant package.
• Write tests that define the expected behavior from the feature description's expectedBehavior.
• Cover: happy path, error cases, edge cases, type narrowing (if applicable).
• Run bun test in the package directory to confirm tests FAIL (red).
• If tests pass before implementation, your tests aren't testing the new behavior.
• Type-only features: For features that only export types (no runtime code), import type in tests won't fail at runtime and package tsconfig excludes test files. Demonstrate the "red" phase by showing that importing the type from a non-test source file would fail typecheck, or write runtime assertion tests (e.g., verify type shape of objects conforming to the type).

3. Implement (Green Phase)

• Write the minimal code to make tests pass.
• Follow existing patterns in the package (check neighboring files for style).
• Use Result<T, E> from better-result, not exceptions.
• Use Bun-native APIs where applicable.
• Ensure the function is exported from the package's public API (add to src/index.ts or relevant subpath export).

4. Refactor

• Clean up while tests are green.
• Remove any dead code or unused imports.
• Ensure consistent naming with the rest of the package.

5. Verify

Do not use bun run check, bun run format:check, or bun run format:fix for validation in this repo — the formatter has a pre-existing tokio panic. Use lint + typecheck instead. If you need to format specific touched files, run bun x oxfmt --write <path>... only on the files you changed and note the fallback in your handoff.

Run these commands and report EXACT output in your handoff:

# Package-level tests
cd packages/<pkg> && bun test

# Full suite (catches cross-package breakage)
bun run test

# Type safety
bun run typecheck

# Lint
bun run lint

Fix any failures before completing. If bun run test surfaces known unrelated failures (e.g., logging test failures from other packages), fall back to package-scoped cd packages/<pkg> && bun test and note the fallback in your handoff.

6. Export Verification

Verify the new API is importable. Run from the package directory (not repo root) since workspace resolution doesn't work from root with bun -e:

cd packages/<pkg> && bun -e "const m = await import('./src/index.ts'); console.log(typeof m.<newExport>)"

Or verify the built output:

cd packages/<pkg> && bun -e "const m = await import('./dist/index.js'); console.log(typeof m.<newExport>)"

This must print function (or object for runtime namespace/enum exports). TypeScript type and interface exports are compile-time only and will print undefined at runtime — that is expected. For type-only exports, verify via .d.ts output or typecheck instead of runtime import checks. See .factory/library/user-testing.md for more verification patterns.

7. Changeset

If the change modifies a published package's runtime behavior or API:

# Interactive/local shells
bun changeset

Select the affected package(s), choose the appropriate bump level (patch for fixes, minor for new features), and write a concise description.

In non-interactive worker/exec mode, create the changeset file directly instead of invoking the prompt:

---
"@outfitter/<pkg>": <bump-level>
---

Describe the user-visible runtime or API change in one sentence.

Use patch for bug fixes, minor for new features, and major for breaking changes so the non-interactive flow matches the interactive prompt.

Save it as .changeset/<short-kebab-summary>.md, then validate the file with:

status=0
bun changeset status --output .changeset/.status-check.json || status=$?
rm -f .changeset/.status-check.json
(exit "$status")

Keep the interactive bun changeset flow for local/manual runs.

8. Commit

Commit with conventional commit format referencing the Linear issue:

feat(contracts): add parseInput() Zod-to-Result helper [OS-332]

Example Handoff

{
  "salientSummary": "Implemented parseInput<T>(schema, data) in @outfitter/contracts returning Result<T, ValidationError>. TDD: wrote 6 tests (valid input, invalid input, nested schema, optional fields, array schema, error message format), all passing. Verified export from @outfitter/contracts, full suite green (3280 pass), typecheck clean.",
  "whatWasImplemented": "parseInput<T>(schema, data) function in packages/contracts/src/validation.ts. Wraps Zod safeParse into Result<T, ValidationError> with formatted error messages. Exported from @outfitter/contracts root and @outfitter/contracts/validation subpath. Added changeset (minor bump).",
  "whatWasLeftUndone": "",
  "verification": {
    "commandsRun": [
      {
        "command": "cd packages/contracts && bun test",
        "exitCode": 0,
        "observation": "47 tests passed including 6 new parseInput tests"
      },
      {
        "command": "bun run test",
        "exitCode": 0,
        "observation": "3280 tests passed, 0 failed"
      },
      {
        "command": "bun run typecheck",
        "exitCode": 0,
        "observation": "No errors"
      },
      { "command": "bun run lint", "exitCode": 0, "observation": "Clean" },
      {
        "command": "bun -e \"const m = await import('@outfitter/contracts'); console.log(typeof m.parseInput)\"",
        "exitCode": 0,
        "observation": "function"
      }
    ],
    "interactiveChecks": []
  },
  "tests": {
    "added": [
      {
        "file": "packages/contracts/src/__tests__/parse-input.test.ts",
        "cases": [
          {
            "name": "returns Ok with parsed value for valid input",
            "verifies": "happy path"
          },
          {
            "name": "returns Err with ValidationError for invalid input",
            "verifies": "error case"
          },
          {
            "name": "preserves Zod error details in ValidationError message",
            "verifies": "error format"
          },
          {
            "name": "infers generic T from schema",
            "verifies": "type narrowing"
          },
          {
            "name": "handles nested object schemas",
            "verifies": "complex input"
          },
          {
            "name": "handles optional fields correctly",
            "verifies": "edge case"
          }
        ]
      }
    ]
  },
  "discoveredIssues": []
}

When to Return to Orchestrator

• Feature depends on an API or type that doesn't exist yet in a different package
• The existing code structure doesn't match what the feature description assumes (e.g., file doesn't exist, different API shape)
• Tests reveal a bug in a different package that blocks this feature
• The feature's scope is significantly larger than described (>200 LOC implementation)
• bun run test or bun run typecheck fails on unrelated code and you cannot proceed