First-PR Fast Lane

The problem: a new contributor opening their first issue in an unfamiliar repo spends hours just finding the right files, understanding conventions, and figuring out what's safe to touch, before writing a single line of code. That time is invisible to most tooling, and it burns senior developer time answering "where do I even start?" First-PR Fast Lane is a structured onboarding workflow built entirely around IBM Bob 2.0's core modes, run end-to-end on a real Node.js/Express repo (first-lane-demo) against a real good-first-issue: adding missing signup validation. The workflow has four phases: 1. Ask (read-only): Bob maps the repo, traces the request flow for POST /signup, and flags files that are safe vs. unsafe to touch, based on CONTRIBUTING.md and the architecture docs. 2. Plan: Bob turns the issue into a file-level implementation plan with no code: a goal statement, a file-by-file change list (modify/do-not-touch), a test plan, risk analysis, and a rollback checkpoint without writing anything yet. 3. Agent + Subagents: a Scout subagent researches existing code patterns and error-response conventions before any code is written; an Implementer subagent applies the fix to exactly one file, matching the approved plan; a Tester subagent adds 10 new test cases and confirms all 16 tests pass; a PR-writer subagent drafts the pull request description, commit message, and risk notes from the actual diff and actual test output. 4. Rollback: we deliberately introduced a one-character regression (a flipped comparison operator) after the fix was working, then re-ran Bob's "if tests fail" playbook. Bob diagnosed the failure as an implementation bug (not a bad test), correctly identified the downstream cascade it caused in two other test suites, rolled back to a pre-implementation git checkpoint, proposed the smallest possible fix, and re-verified all 16 tests passed again, all without touching any file outside the approved plan. Target users are engineering teams onboarding new contributors, and open-source maintainers who want a repeatable, auditable process for guiding first-time contributors through their first PR safely. This demonstrates measurable impact: the full Ask→Plan→Agent→Test→PR cycle completed in roughly 34 minutes, touching only the 2 files the plan named, with zero blocking review comments and zero scope creep, compared to the much longer, more error-prone unassisted path a first-time contributor typically takes.