spec-driven-implementation

Drive a spec-first workflow for substantial features in Warp.

Overview

Use this skill for significant features where a written spec will improve implementation quality, reduce ambiguity, or make review easier. Be pragmatic: not every change needs specs.

Specs should usually live in:

```
specs/<linear-ticket-number>/PRODUCT.md
```
```
specs/<linear-ticket-number>/TECH.md
```

For example:

```
specs/APP-1234/PRODUCT.md
```
```
specs/APP-1234/TECH.md
```

specs/

should contain only ticket-named directories as direct children. Do not create engineer-named subdirectories or feature-slug directories there.

If a relevant Linear issue does not already exist, create one before writing specs. Use the Linear MCP tools directly:

```
list_teams
```
to find the appropriate team
```
list_issue_labels
```
to inspect the expected labels/tags
```
save_issue
```
to create the issue with the appropriate team and labels

If the correct team or labels are not obvious from the request and surrounding context, use

ask_user_question

to clarify rather than guessing.

These specs should largely be written by agents, not by hand, and should be checked into source control so they can be reviewed and kept current with the code.

When specs are required

Strongly prefer specs when the change is substantial, such as:

product or architectural ambiguity
expected implementation size around 1k+ LOC
deep or cross-cutting stack changes
risky behavior changes where regressions would be expensive
work where agent quality will improve materially from clearer inputs

Specs are often unnecessary for:

small, local bug fixes
straightforward refactors
narrow UI tweaks with little ambiguity

For pure UI changes, the product spec is often useful while the tech spec may be unnecessary.

Workflow

1. Decide whether the feature needs specs

Evaluate the size, ambiguity, and risk of the feature. If specs will not meaningfully improve execution or review, skip them and focus on verification instead.

2. Write the product spec first

Before implementation, create

PRODUCT.md

describing the desired user-facing behavior.

Use the

write-product-spec

skill to produce it. The product spec should define:

what problem is being solved
the desired user experience
invariants and edge cases
success criteria
how the behavior will be validated

If the feature has UI or interaction design, ask for a Figma mock if one exists. If there is no mock, continue but call that out explicitly in the product spec.

Reference the Linear issue in the spec when one exists. Because specs live under

specs/<linear-ticket-number>/...

, this should usually be straightforward.

3. Write the tech spec when warranted

Use the

write-tech-spec

skill for substantial or ambiguous implementation work.

Prefer a tech spec when:

the implementation spans multiple subsystems
architecture or extensibility matters
there are meaningful tradeoffs to document
reviewers will benefit more from reviewing the plan than the raw code

It is acceptable to write the tech spec after an e2e prototype if that leads to a more accurate implementation plan. Do not force a premature tech spec when the implementation details are still too uncertain.

4. Implement approved specs

After the specs are approved, use the

implement-specs

skill to build from the approved

PRODUCT.md

and

TECH.md

The implementation can often be pushed in the same PR as the product and tech specs. As the engineer iterates, keep

PRODUCT.md

TECH.md

, code changes, and tests in that same PR so the review reflects the feature that will actually ship.

For large features, the implementer may optionally offer:

```
PROJECT_LOG.md
```
to track explored paths, checkpoints, and current implementation state
```
DECISIONS.md
```
to capture concrete product and technical decisions made during design and implementation

These are optional aids, not required outputs.

5. Keep specs current during implementation

If implementation changes from the spec, update the spec rather than leaving it stale.

Update

PRODUCT.md

when:

user-facing behavior changes
success criteria change
UX details or edge cases change

Update

TECH.md

when:

the implementation approach changes
architectural boundaries move
risks, dependencies, or rollout details change
the testing or validation plan changes

The checked-in specs should describe the feature that actually ships, not just the initial intent. Keep those spec updates in the same PR as the related code changes whenever practical.

6. Verify behavior against the spec

Before considering the work complete, make sure verification maps back to the specs. Prefer tests and artifacts that validate the product behavior directly:

unit tests and regression coverage that follow the repository's local testing conventions
integration tests for critical user flows
loom walkthroughs or equivalent feature demonstrations when appropriate
screenshots or videos when useful for UI-heavy work

Best Practices

Be pragmatic above all else.
Write specs to improve input quality for agents, not as ceremony.
Keep product specs behavior-oriented and implementation-light.
Keep tech specs implementation-oriented and grounded in current codebase patterns.
Use review time to validate specs and behavior, not to over-index on code style nits.

Related Skills

```
implement-specs
```
```
write-product-spec
```
```
write-tech-spec
```

spec-driven-implementation

NPX Install

Tags

SKILL.md Content

spec-driven-implementation

Overview

When specs are required

Workflow

1. Decide whether the feature needs specs

2. Write the product spec first

3. Write the tech spec when warranted

4. Implement approved specs

5. Keep specs current during implementation

6. Verify behavior against the spec

Best Practices

Related Skills