abildtoft/kramme:code:incremental

Incremental Implementation

This skill edits files and commits each verified slice, so it runs only after explicit user invocation.

Deliver changes in small, verified slices with scope discipline, incremental verification between slices, and feature-flag guardrails for incomplete work. This is the procedural expression of the rule "don't add features beyond what the task requires": turn implementation into a loop of small, verified, rollback-friendly increments where out-of-scope observations are logged but never silently fixed.

When to use

• Implementing any change that spans more than one file or more than one logical commit.
• After kramme:siw:generate-phases or any planning step — each phase executes as a sequence of increments through this loop.
• Any time scope creep is a realistic risk, especially when touching files adjacent to the target area.
• Refactors where you want each intermediate state to be independently reviewable and revertible.

Do not use for: single-file one-line fixes, doc-only edits, dependency-version bumps, or any change whose entire diff fits in a single coherent commit. The loop's overhead outweighs the discipline at that size.

The Rules

Rule 0 — Simplicity First

Before writing any code, emit a SIMPLICITY CHECK marker stating the simplest version of the change that could satisfy the requirement. Only expand beyond that simplest version if a concrete requirement forces it.

SIMPLICITY CHECK: <one-line summary of the minimum viable change>

If the simplest version is not what you end up building, write a second line explaining what forced the expansion. If there is no forcing requirement, do the simplest version.

Rule 0.5 — Scope Discipline

When you notice something outside the scope of the current slice — a typo in an adjacent function, a missing null check three lines above, an import that could be cleaner — emit a NOTICED BUT NOT TOUCHING marker and move on. Do not silently fix, refactor, or modernize adjacent code, even if the fix is trivial.

NOTICED BUT NOT TOUCHING: <what you saw>
Why skipping: <out-of-scope / unrelated / deferred>

The canonical "do NOT" list (clean up adjacent code, refactor untouched imports, modernize syntax in files you only read, build abstractions before the third use case, etc.) and the rationale for each item live in references/scope-discipline.md. Read it before the first slice if scope creep is a known failure mode on this change.

Rule 1 — One thing at a time

One logical change per slice. If a slice is doing two things, split it. A slice can touch multiple files as long as they serve the same single logical change.

Signs you are doing two things:

• The commit message wants to use "and".
• The diff has two independent review paths.
• Reverting one part without the other still leaves a coherent state.

Rule 2 — Keep it compilable between slices

After every slice, the project builds, typechecks, and existing tests pass. Never commit a broken intermediate state — not even "temporarily." If a slice would break the build, it is too large; split it further, or gate the incomplete half behind a flag (Rule 3).

Rule 3 — Feature flags for incomplete features (conditional)

If the project uses feature flags, guard incomplete or in-progress work behind a flag so it can ship dark. This lets you land partial work through the normal release process without exposing it to users.

If the project has no flag infrastructure, do not introduce flag machinery just for this skill. Instead, keep slices small enough that each slice is independently releasable on its own. Prefer "smaller slices" over "introduce flags."

Rule 4 — Safe defaults

New flags, parameters, options, and config fields default to the old behavior. New code paths are opt-in, not opt-out. A user who upgrades and changes nothing should see no behavior change.

Rule 5 — Rollback-friendly commits

Each commit stands alone and can be reverted without breaking the build or leaving the codebase in a broken state. No "part 1 of 3" commits where part 1 alone is broken.

Rule of thumb: if git revert on any single commit would break main, the commit is not rollback-friendly.

The Increment Cycle

Each increment is one pass through this five-step loop:

1. Slice — pick one slicing strategy: vertical, contract-first, or risk-first. See references/slice-strategies.md for when to use each and concrete examples.
2. Implement — build the smallest version of the slice that is coherent and compilable. One logical change.
3. Verify — build, typecheck, lint, and run existing tests. Delegate to kramme:verify:run to execute the project's verification battery. If that skill is unavailable, or the project has no configured verification battery, invoke the project's build/typecheck/test commands directly (read them from package.json, Makefile, or equivalent) and log the missing battery as a NOTICED BUT NOT TOUCHING for a follow-up slice. Do not skip verification.
4. Commit — compose an atomic, descriptive commit message. Delegate to kramme:git:commit-message.
5. Move forward — carry state to the next slice. Do not restart the loop from scratch; the next slice builds on the committed state.

Emit a SIMPLICITY CHECK marker at the start of step 2, and a NOTICED BUT NOT TOUCHING marker any time during the loop when you see something out-of-scope.

Increment checklist (exit criterion)

Before marking a slice done, confirm every box:

• [ ] Does one thing.
• [ ] Existing tests pass.
• [ ] Build succeeds.
• [ ] Typecheck passes.
• [ ] Lint passes.
• [ ] New functionality works.
• [ ] Committed with descriptive message.

If any box is unchecked, the slice is not done. Fix the gap or split the slice.

Refactor mode

When this skill runs against refactor work — explicit --refactor flag, invocation directly after kramme:code:refactor-opportunities, or any user ask phrased as "refactor X" — produce a different output shape on top of the same rules: an interview-driven Decision Document plus an ordered tiny-commits plan.

When this mode applies — opt-in. Trigger on --refactor, on a refactor candidate handed off from kramme:code:refactor-opportunities, or on the user phrase "refactor X" / "consolidate Y" / "extract Z". Feature work does not need this mode.

How it works — the increment loop runs a 7-step interview before the first slice (problem statement → verify in code → alternatives considered → scope hammer → test coverage check → tiny-commits plan → file Decision Document), then executes the slices through the standard cycle. Each commit must leave the codebase in a working state — Fowler's bar — and revertible with git revert without breaking main. Decision Document goes to siw/REFACTOR_DECISIONS.md if SIW is active, otherwise inline as a markdown block in the body (not the subject line) of the first commit, which carries rationale for the whole stack — reviewers should expect to scan the first commit's body, not its title. The full interview, template, and per-commit checklist live in references/refactor-mode.md.

Relationship to the rules — refactor mode does not relax any rule. Rule 0 (Simplicity), 0.5 (Scope Discipline), 1 (One thing), 2 (Compilable), 4 (Safe defaults), and 5 (Rollback-friendly) all apply per slice. Rule 3 (Feature flags) is usually inapplicable during a refactor since behavior is unchanged; if the refactor temporarily forks behavior, flag it as for any other in-progress feature.

Sibling skills. kramme:code:refactor-pass is the simplification-loop sibling — use it when the goal is to shrink or clarify recently changed code without restructuring. Use refactor mode here when the goal is structural change (depth, seams, locality) with a documented rationale that should outlive the diff.

Integration with other skills

• Upstream: typically invoked after kramme:siw:generate-phases — each generated phase becomes a sequence of slices through this loop. Any planning skill that produces a phased plan can feed into this one.
• Step 3 (Verify): delegates to kramme:verify:run for the project's verification battery.
• Step 4 (Commit): delegates to kramme:git:commit-message for commit composition.
• Sibling: kramme:code:refactor-pass follows the same slice discipline — refactors are a different flavor of increment but obey the same rules.

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Common Rationalizations

These are the lies you will tell yourself to justify scope creep. Each one has a correct response:

• "It's just a one-line cleanup while I'm here." → Emit NOTICED BUT NOT TOUCHING. Log it for a future slice.
• "The abstraction is obvious, I'll build it now." → Rule of three. Wait for the third use case.
• "This test is flaky, let me rewrite it." → Unrelated slice. File separately and continue with the current slice.
• "I'll split the commit later." → You won't. Split it now.
• "The build is broken anyway, one more broken commit doesn't matter." → It matters for bisect and revert. Fix the build before the next commit.
• "This change is too small to need a flag." → Then it's too small to be incomplete. Finish it or flag it.

Red Flags

If you notice any of these, stop and re-slice:

• More than 100 lines of change without running tests.
• Multiple unrelated changes in a single increment.
• "Let me just quickly add this too."
• Touching files "while I'm here."
• Building an abstraction before the third use case.
• Commit message uses "and" to join two independent clauses.
• Reverting the last commit would not leave main in a green state.

Verification

Before declaring the whole feature done, self-check:

• Does every commit build independently? (Spot-check with git bisect or by checking out a few commits.)
• Is there a NOTICED BUT NOT TOUCHING log for every out-of-scope observation?
• Does each commit message describe exactly one thing?
• If the feature shipped behind a flag, does the flag default to the old behavior?
• Would a reviewer who looks at commits one-by-one understand the progression without reading the whole diff?

If any answer is no, finish the gap before declaring done.