incremental-implementation

name	incremental-implementation
description	Delivers changes incrementally (MeKnow-adapted, polyglot + OpenSpec). Use when implementing any feature or change that touches more than one file in this repo. Use when you're about to write a large amount of code at once, or when a task feels too big to land in one step. Each slice stays buildable and green under the resolver-selected gates (uv/go/pnpm as applicable + ci-free-gates.sh + solo-spec validate).
tags	[]

Incremental Implementation

Overview

Build in thin vertical slices — implement one piece, test it, verify it, then expand. Avoid implementing an entire feature in one pass. Each increment should leave the system in a working, testable state. This is the execution discipline that makes large features manageable, and it is exactly how /solo:implement works through an OpenSpec change's work-units: one unit, Red→Green→one commit (ticking tasks.md off), before the next.

When to Use

• Implementing any multi-file change
• Working through the work-units of an OpenSpec change (/solo:implement)
• Building a new feature from a task breakdown
• Refactoring existing code
• Any time you're tempted to write more than ~100 lines before testing

When NOT to use: Single-file, single-function changes where the scope is already minimal.

The Increment Cycle

┌──────────────────────────────────────┐
│                                      │
│   Implement ──→ Test ──→ Verify ──┐  │
│       ▲                           │  │
│       └───── Commit ◄─────────────┘  │
│              │                       │
│              ▼                       │
│          Next slice                  │
│                                      │
└──────────────────────────────────────┘

For each slice:

1. Implement the smallest complete piece of functionality
2. Test — run the narrow test target in the touched package's language; write the test first per test-driven-development
3. Verify — the resolver-selected gates stay green (uv/go/pnpm as applicable for the touched packages + ci-free-gates.sh on py/bench changes + solo-spec validate "<change>" --strict)
4. Commit — save progress with a descriptive message; tick off the matching tasks.md item if you're inside an OpenSpec change
5. Move to the next slice — carry forward, don't restart

Slicing Strategies

Vertical Slices (Preferred)

Build one complete path through the stack. In MeKnow, a "stack" is ingest → retrieve_kb → synthesize/cite/filter → API/portal:

Slice 1: filter stage refuses on missing citations   (rag-core filter.py + test_filter.py)
    → unit test passes, refuse_if no_citations enforced

Slice 2: retrieve_kb enforces tenant ACL server-side  (rag-core retrieve + pgvector test)
    → DB test passes, no chunk crosses tenant_id

Slice 3: synthesize emits memo_schema_ref-shaped output (agent-core, temperature==0)
    → deterministic test passes, raw chunks never leave the sub-agent

Slice 4: API surface exposes the answer endpoint        (apps/backend + generated portal types)
    → endpoint test passes, benchmark ladder green

Each slice delivers working end-to-end functionality.

Contract-First Slicing

When the backend and portal (or two packages) evolve in parallel, pin the contract first. OpenAPI is the API contract and portal types are generated, never hand-written:

Slice 0: Define the contract (OpenAPI schema in apps/backend; regenerate portal types)
Slice 1a: Implement the backend side against the spec + pytest tests
Slice 1b: Implement the portal side against the generated types + vitest tests
Slice 2: Integrate and exercise the real path (benchmark ladder / pnpm test:e2e)

For the MCP boundary, pin the kb.* tool contract (capability mcp-and-skills) first, then implement the embedded-transport tool and its caller against it.

Risk-First Slicing

Tackle the riskiest or most uncertain piece first:

Slice 1: Prove cross-tenant isolation holds in retrieve_kb under a cache-key collision (highest risk)
Slice 2: Build the citation/cite stage on the proven retrieval path
Slice 3: Add the synthesize + filter (refuse_if no_citations) stages on top

If Slice 1 fails, you discover it before investing in the later slices.

Implementation Rules

Rule 0: Simplicity First

Before writing any code, ask: "What is the simplest thing that could work?" After writing it, review against these checks — and if the answer is "simplify," reach for the code-simplification skill:

• Can this be done in fewer lines?
• Are these abstractions earning their complexity?
• Would a staff engineer say "why didn't you just..."?
• Am I building for hypothetical future requirements, or the current task?

SIMPLICITY CHECK:
✗ A generic agent-framework layer wrapping the LLM
✓ The thin BotPolicy interpreter on anthropic-sdk-python directly (no LangChain)

✗ A new interpreter branch for a new bot behavior
✓ A new BotVersion/BotPolicy row + prompt file (config, not code)

✗ An interface with a single implementation, added "for testing"
✓ The concrete type plus a stubbed LLM transport at the boundary

Three similar lines is better than a premature abstraction. Implement the naive, obviously-correct version first. Optimize only after correctness is proven with tests.

Rule 0.5: Scope Discipline

Touch only what the task requires.

Do NOT:

• "Clean up" code adjacent to your change
• Reorder imports in files you're not modifying
• Remove comments you don't fully understand
• Add features not in the spec because they "seem useful"
• Modernize syntax in files you're only reading

If you notice something worth improving outside scope, note it — don't fix it:

NOTICED BUT NOT TOUCHING:
- packages/ingest-core has an unused helper (unrelated to this task)
- The retrieve_kb log lines could be clearer (separate task)
→ Want me to open a follow-up OpenSpec change for these?

Rule 1: One Thing at a Time

Each increment changes one logical thing. Don't mix concerns.

Bad: one commit that adds a new BotPolicy stage, refactors the retrieve_kb ACL path, and edits an Alembic migration.

Good: three separate commits — one per change.

Rule 2: Keep It Buildable

After each increment, the touched packages must still build and their existing tests pass — uv --directory D run pyright + pytest -q for Python, go build ./... for a Go module, pnpm typecheck for the portal. Don't leave a package in a broken state between slices. Remember a new bot/capability is a new BotVersion/BotPolicy row + prompt file, not a code change, and a new engine capability is a lobe/path registry row, never an interpreter branch — so those slices shouldn't drag code changes along with them.

Rule 3: Guard Incomplete Behavior

If a capability isn't ready but you want to land increments, keep it inert behind config rather than half-wired into the live path. Example: a new BotPolicy row can exist without being the active BotVersion, or a behavior can be gated on a policy/config flag that defaults off, so the live retrieval and answer paths stay unchanged until it's complete.

Rule 4: Safe Defaults

New code defaults to safe, conservative behavior. Honor the invariants:

# Safe: tenant_id is mandatory and threaded through; citations-mandatory means
# the default outcome of an answer path is to refuse, not to emit ungrounded text.
def answer(*, query: str, tenant_id: str, acl: Acl) -> Answer:
    hits = retrieve_kb(query=query, tenant_id=tenant_id, acl=acl)  # ACL server-side
    memo = synthesize(hits, tenant_id=tenant_id)                  # temperature == 0
    result = filter_answer(memo, tenant_id=tenant_id)             # refuse_if no_citations
    return result  # refuses by default when ungrounded

Rule 5: Rollback-Friendly

Each increment should be independently revertable:

• Additive changes (new files, new functions, new BotPolicy row, new lobe registry row) are easy to revert
• Modifications to existing code should be minimal and focused
• Alembic migrations must have a matching downgrade so they can roll back, and KB/Bot versions are append-only — never mutate a prior version in place
• Avoid deleting and replacing in the same commit — separate them

Working with Agents

When directing an agent to implement incrementally:

"Let's implement Task 3 from the OpenSpec change.

Start with just the retrieve_kb ACL check and its pytest. Don't touch the
synthesize stage yet — that's the next increment.

Write the failing test first (per test-driven-development), then implement.
After implementing, run the resolver-selected gates for the touched package
(uv ruff/format/pyright/pytest, plus ci-free-gates.sh and solo-spec validate)
to verify nothing is broken. If DB-dependent tests skip, bring up pgvector
with docker compose -f docker-compose.dev.yml and set DATABASE_URL."

Be explicit about what's in scope and what's NOT in scope for each increment.

Increment Checklist

After each increment, verify:

• The change does one thing and does it completely
• All existing tests in the touched package(s) still pass
• The touched package(s) still build/typecheck (pyright / go build ./... / pnpm typecheck)
• Lint/format are clean (ruff check + ruff format --check / go vet / pnpm lint)
• bash benchmarks/ci-free-gates.sh is green if a py/bench file changed
• solo-spec validate "<change>" --strict passes
• The new functionality works as expected (narrow test green)
• If inside an OpenSpec change, the matching tasks.md item is ticked
• The change is committed with a descriptive message

Note: Run each verification command after a change that could affect it. After a successful run, don't repeat the same command unless the code has changed since. A DATABASE_URL-skip is not a failure, but it's also not coverage — bring up pgvector for DB-dependent slices.

Common Rationalizations

Rationalization	Reality
"I'll test it all at the end"	Bugs compound. A bug in Slice 1 makes Slices 2-4 wrong. Test each slice.
"It's faster to do it all at once"	It feels faster until something breaks and you can't find which of 500 changed lines caused it.
"These changes are too small to commit separately"	Small commits are free. Large commits hide bugs and make rollbacks painful.
"I'll wire the new behavior into the live path now and gate it later"	If it isn't complete, keep it inert (inactive BotVersion / flag off) so the live retrieval and answer paths stay safe.
"This refactor is small enough to include"	Refactors mixed with features make both harder to review and debug. Split them (see code-simplification).
"I'll skip the downgrade migration for now"	Without a matching Alembic downgrade, the increment isn't rollback-friendly. Write it now.
"Let me run the gates again just to be sure"	After a successful run with no intervening edits, re-running adds nothing. Run them again after the next change.

Red Flags

• More than 100 lines written without running tests
• Multiple unrelated changes in a single increment
• "Let me just quickly add this too" scope expansion
• Skipping the test/verify step to move faster
• Build, typecheck, or tests broken between increments
• An Alembic migration without a matching downgrade, or an in-place mutation of an append-only version
• A code change sneaking into a slice that should only add a BotPolicy/lobe-registry row
• A slice that drops tenant_id from a query, cache key, or log line
• Large uncommitted changes accumulating
• Building abstractions before the third use case demands it
• Touching files outside the task scope "while I'm here"
• Re-running the same gate command with no intervening code change

Verification

After completing all increments for a task:

• Each increment was individually tested and committed
• The resolver-selected gates pass for every touched package (uv/go/pnpm as applicable + ci-free-gates.sh + solo-spec validate "<change>" --strict)
• The feature works end-to-end as specified (exercise the benchmark ladder / pnpm test:e2e if it touches the answer pipeline or portal)
• No uncommitted changes remain

MeKnow notes

• OpenSpec lifecycle. Start non-trivial work with /solo:propose, quality-gate with /solo:spec, merge the contract with /solo:spec-pr (sync delta→canonical + the human-merged SPEC PR), then implement unit-by-unit with /solo:implement (ship-plan groups the units, ship-code runs each Red→Green→one commit, ticking tasks.md as you go), which reconciles the delta vs canonical and /solo:archive when the code PR merges. The autonomous /solo:implement pipeline plans → implements → verifies → reconciles → opens the CODE PR; its Test(Red) phase pairs naturally with thin slices — one failing test, minimal code, repeat (see test-driven-development). All of this happens inside the platform/ submodule.
• Invariants to keep intact across slices: multi-tenant by default (tenant_id on every table/query/cache key/log line; cross-tenant joins are bugs); citations mandatory (filter stage carries refuse_if: no_citations); temperature == 0 on synthesize/cite/filter; ACL enforced server-side in retrieve_kb with caller identity inherited; versions append-only (BotVersion/KBVersion — new child with a parent pointer); compression invariant (only memo_schema_ref-shaped objects cross stage boundaries); MCP as the internal tool boundary (kb.*, embedded transport); no LangChain/LangGraph/Haystack/LlamaIndex; OpenAPI is the API contract (portal types generated); new bot/capability = new BotVersion/BotPolicy row + prompt file; new engine capability = a lobe/path registry row, never an interpreter branch.
• Test-deliverable file patterns per slice: tests/test_<feature>.py (pytest) for Python, <feature>_test.go (table-driven) for Go, apps/portal/src/**/<feature>.test.ts(x) (vitest) for TypeScript — in the touched package's language.
• DB-dependent pytest needs DATABASE_URL/TEST_DATABASE_URL pointing at a pgvector instance (local docker compose -f docker-compose.dev.yml; CI pgvector/pgvector:pg16). Absent a DB those tests skip (recorded, not failed) — bring up pgvector for DB-dependent slices.