The craft
behind the work.
Practical techniques for thinking, building,
and creating with AI. Precise enough to test.
Small enough to put to work today.
Make the acceptance
condition executable. ↗
A fluent answer can still break the contract. Separate the candidate from the predicate that checks it—and make the result inspectable.
const withinCapacity = items.length ≤ k; const unique = distinct(items); accept = withinCapacity ∧ unique;
Find your next technique.
32 practical field notes. Each with a formulation, a working example, and a counterexample.
Separate pure plans from released effects
ESS & agentic engineering · A two-mode checker that keeps pure planning distinct from authorized execution.
Transfer Rust ownership at a task boundary
Rust & agentic engineering · A browser transfer model and compile-fail Rust ownership example for a single task packet.
Make parse failure explicit with Rust Result
Rust & reliable interfaces · A browser-aligned parser and compile-tested Rust Result example with explicit failure variants.
Encode review state with Rust typestate
Rust & agentic engineering · A browser model and compile-tested Rust typestate example for draft and reviewed articles.
Cap deterministic retry backoff
Reliable software systems · A deterministic retry calculator with an explicit attempt budget and delay cap.
Do not redispatch an indeterminate model step
Exocore & reliable workflows · A pedagogical lifecycle checker that holds redispatch after a model step becomes indeterminate.
Detect idempotency-key conflicts
Exocore & reliable workflows · A deterministic idempotency check that distinguishes new requests, replay, conflict and duplicate history.
Check producer and consumer compatibility
ESS & software architecture · A bounded required-field compatibility check for a typed producer-consumer seam.
Return a loss report with every projection
ESS & knowledge engineering · A shallow scalar projection checker that compares actual and declared loss.
Keep capability separate from permission
ESS & agentic engineering · A checker that prevents technical capability or adjacent scope from becoming authority.
Fail closed when a guard state is unknown
ESS & agentic engineering · A tri-state guard checker that treats unknown as a hold with visible evidence.
Reject stale retrieval evidence at an explicit boundary
Knowledge & synthesis · Reject evidence that exceeds a stated maximum age while accepting the exact boundary.
Separate evidence confidence from release status
Knowledge & synthesis · Keep evidence confidence and release lifecycle in independent fields rather than deriving one from the other.
Explain a revision with set differences
Knowledge & synthesis · Use added and removed set members to give a compact, reproducible revision explanation.
Preserve source offsets when extracting spans
Knowledge & synthesis · Check extracted spans against JavaScript UTF-16 code-unit offsets, including surrogate-pair boundaries.
Select context by relevance under a token budget
Knowledge & synthesis · A deterministic greedy selector that prioritizes relevance while keeping within a declared token budget.
Detect cycles in a dependency graph
Knowledge & synthesis · Use depth-first traversal to identify a directed dependency cycle before scheduling work.
Preserve minority conclusions during synthesis
Knowledge & synthesis · A retention check that keeps every supplied conclusion, including minority positions, in a synthesis record.
Separate contradiction from missing evidence
Knowledge & synthesis · Classify unsupported records separately from records that assert incompatible values for the same claim.
Require every claim to name its evidence
Knowledge & synthesis · A claim-to-evidence checker that rejects claims with no named supporting record.
Detect source revision drift with explicit identity
Knowledge & synthesis · A small explicit check for source revision drift without treating a version label as cryptographic proof.
Check design contrast with the WCAG formula
Design with AI · Calculate relative luminance and compare a synthetic color pair with a declared contrast threshold.
Choose a diverse concept set with declared tags
Creative practice · Check a synthetic concept set for unique identities, required tags and a declared diversity floor.
Separate the fixed brief from optional variation
Creative practice · Check that a synthetic creative candidate keeps fixed brief fields and uses only declared optional fields and values.
Vary one creative parameter at a time
Creative practice · Compare two synthetic creative candidates and require exactly one declared parameter to differ.
Score a creative candidate with declared criteria
Creative practice · Apply explicit weighted criteria to a synthetic creative candidate without calling the score a quality verdict.
Carry the constraints across a handoff
Agentic engineering · Check that required and optional task constraints survive a synthetic handoff.
Stop refinement at a declared budget
Agentic engineering · Verify that a refinement trace stays within its iteration budget and records one entry per iteration.
Keep a simple baseline in the comparison
Evaluation practice · Compare declared numeric criteria with a baseline and an explicit margin.
Check output shape before the next step
Agentic engineering · Reject missing fields and wrong item types before a downstream operation reads an output.
Treat prompt fields as data, not separators
Prompt craft · Test whether a prompt transport preserves items that contain its separator.
Make the acceptance condition executable
ESS & agentic engineering · One independent acceptance predicate, a runnable example, and a counterexample.
TO THE FIELD JOURNAL
Ideas become useful
when you can work with them.
Fieldcraft is the Hearth & Code notebook for that moment: the small method, the explicit assumption, the example you can run. Across engineering, knowledge and creative work, we show the technique—and the limits of what it demonstrates.
Inspect the source ↗