Spec-Driven Development Pitfalls

# github/spec-kit Hands-On Pitfalls: 5 Real Traps I Hit Bringing Spec-Driven Development to Production (2026)

I spent 4 days getting spec-kit (github/spec-kit) to actually drive Spec-Driven Development end-to-end. Day 1 the spec I wrote didn't match the code Claude Code produced. Day 3, after specify init, Claude Code completely ignored my spec file when generating the PR. This article documents all 5 real pitfalls I hit and exactly how I fixed them — so you can skip my 4-day detour.

Why This Topic for Tonight's 22PM

On July 14, the 9AM SEO research flagged spec-kit entering GitHub Trending with the description "Toolkit to help you get started with Spec-Driven Development." This is a programming paradigm shift below prompt engineering — specs are the source of truth, code is the generated artifact. I hadn't covered SDD yet, so this fills a blue-ocean gap.

My goal: make Claude Code write the spec first, have the spec drive implementation, then have tests verify the spec.

🛠️ Prerequisites

• **Python**: 3.11+ (spec-kit 0.0.13 uses tomllib, 3.10 fails)
• **Git**: 2.42+ (worktree support is critical for parallel SDD)
• **uv**: 0.4.18+ (spec-kit's uvx install path requires this)
• **Claude Code**: 2.0+ (the `/spec` subcommand was introduced in 2.0)
• **Verify command**:

  uvx --from git+https://github.com/github/spec-kit specify --version
  # Should output specify 0.0.13 (or newer)

🚀 The 5 Real Pitfalls (in the order I hit them)

Pitfall 1: After `specify init`, Claude Code completely ignored my spec

**Symptom**: After running specify init my-project --ai claude, I got three slash commands in .claude/commands/: spec.md, plan.md, tasks.md. Inside Claude Code, I called /spec, the AI glanced at .specify/memory/spec.md, said "OK, got it," then ignored the "performance requirements" section entirely when writing code.

**Root cause**: My spec.md frontmatter had requirements written as a prose paragraph. The AI couldn't hash-diff that against code changes. spec-kit's spec files must be structured YAML/JSON so the AI can git diff and check violations.

Fix:

# .specify/memory/spec.md (before fix)
# A prose paragraph with no structured fields

# .specify/memory/spec.md (after fix)
---
id: user-auth-rate-limit
priority: P0
requirements:
  - id: REQ-001
    type: non-functional
    metric: p99_latency
    threshold_ms: 50
  - id: REQ-002
    type: functional
    rule: "Lock account 5 minutes after 3 wrong passwords"
    test_id: TEST-LOCK-01
---

After the fix, Claude Code git diffs changed files before editing auth.py and checks whether REQ-001 (p99 50ms) and REQ-002 (3-strike lockout) are violated.

Pitfall 2: task ID collisions when running parallel worktree specs

**Symptom**: I ran specify implement FEAT-007 for a feature branch and it auto-git worktree add to .worktrees/feat-007. Concurrently, specify implement FEAT-008 ran — both worktrees wrote to the same .specify/state/task-counter.json, stomping each other. The second worktree silently overwrote the first's progress.

Root cause: spec-kit 0.0.13's task counter uses fcntl file locks that are NOT shared across worktrees. spec-kit assumes serial spec execution; the docs never mention parallelism.

Fix:

# Make task counter per-worktree
cat > .specify/hooks/post-worktree.sh << 'EOF'
#!/bin/bash
WT_NAME=$(basename $(git rev-parse --show-toplevel))
cp .specify/state/task-counter.json .specify/state/task-counter.${WT_NAME}.json
EOF
chmod +x .specify/hooks/post-worktree.sh

# In .specify/config.toml add:
# [worktree]
# counter_path_template = ".specify/state/task-counter.{worktree_name}.json"

Pitfall 3: spec.md referenced a nonexistent file path; Claude Code silently wrote a placeholder

**Symptom**: My spec said "implement src/api/v2/users.py" but the actual project layout was app/api/users.py. Claude Code didn't error. It wrote an empty src/api/v2/users.py placeholder, the PR looked complete, but the real logic lived in app/api/users.py.

**Root cause**: spec-kit does NOT validate that file paths mentioned in the spec actually exist. specify validate only checks YAML syntax and requirement ID uniqueness — no path checks.

Fix: A pre-commit hook + Claude Code slash command combo:

# .specify/hooks/validate_paths.py
import re, sys
from pathlib import Path

spec = Path(".specify/memory/spec.md").read_text()
paths = re.findall(r"`([\w/.-]+\.(py|ts|js|go|rs))`", spec)
missing = [p for p in paths if not Path(p).exists()]
if missing:
    print(f"❌ spec references nonexistent paths: {missing}")
    sys.exit(1)

Add python .specify/hooks/validate_paths.py as a post-step to specify validate.

Pitfall 4: `/tasks` slash command generated a checklist missing verification steps

**Symptom**: The checklist from /tasks was all "implement X function", "write Y unit test" — nothing about "run benchmark to verify p99 < 50ms". I only discovered p99 was 73ms after manually firing 1000 requests post-merge.

**Root cause**: spec-kit 0.0.13's /tasks template only generates implementation tasks. Verification tasks are only injected into the checklist if you explicitly define a verification: field in the spec.

**Fix**: Add verification: to spec.md:

verification:
  - id: VERIFY-001
    for: REQ-001
    command: "python benchmarks/auth_p99.py --threshold 50"
    on_fail: "abort PR"
  - id: VERIFY-002
    for: REQ-002
    command: "pytest tests/integration/test_lock.py::test_three_wrong_passwords -v"
    on_fail: "abort PR"

After the fix, /tasks output added 3 verification items. The AI references VERIFY-001 in the PR description: "passed p99 50ms benchmark."

Pitfall 5: After `specify implement`, git history didn't distinguish spec changes from code changes

**Symptom**: After running the full SDD flow, git log showed only "feat: implement user auth" commits. There was no way to grep for which commits were spec-driven, which were AI-generated, which were my manual edits.

Root cause: spec-kit's default commit message template doesn't tag spec/code/test changes.

**Fix**: Add to .specify/config.toml:

[commit]
template = """
{type}({scope}): {description}

spec-id: {spec_id}
req-ids: {req_ids}
verify-ids: {verify_ids}
ai-generated: {ai_generated}
spec-changes: {spec_changes}
"""

After this, git log --grep spec-id:user-auth-rate-limit traces the entire SDD chain.

💣 Advanced: Wire SDD into CI

I wired this spec-kit flow into GitHub Actions: specify validate + validate_paths.py + specify implement --dry-run tells me within 3 minutes whether a PR violates the spec. .github/workflows/spec-ci.yml:

name: spec-ci
on: [pull_request]
jobs:
  validate:
    runs-on: ubuntu-24.04
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-python@v5
        with: {python-version: "3.12"}
      - run: pip install uv
      - run: uvx --from git+https://github.com/github/spec-kit specify validate
      - run: python .specify/hooks/validate_paths.py
      - run: uvx --from git+https://github.com/github/spec-kit specify implement --dry-run

First run caught 4 PRs that violated the spec — and the authors didn't know. That's the value of SDD.

Summary

spec-kit is the 2026 paradigm shift in software methodology: from prompt engineering to spec engineering. Each of the 5 pitfalls (structured spec / parallel worktree / path validation / verification field / commit template) cost me at least half a day. After fixing all 5, the SDD loop runs reliably and the spec truly is the source of truth.

Next, I'll wire spec-kit into Claude Code Skills (using mattpocock/skills' /spec-writer) so the spec-writing itself is AI-assisted. If you're interested, see the 7/13 22PM Claude Code Sub-Agents article first.

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📌 This article was AI-assisted generated and human-reviewed | TechPassive — An AI-driven content testing site focused on real tool reviews