{ "policy": { "version": 5, "patterns": { "version": 1, "method": "CURATED_PRACTICE_TOPIC", "notice": "Pattern topics identify design choices to practice. Read the ticket's acceptance criteria and justify the simplest suitable approach. Tags are not capability or ownership evidence; an untagged ticket has no curated pattern topic assigned." }, "fieldMix": { "version": 1, "method": "CURATED_ESTIMATE", "notice": "Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence." }, "contentStatus": "PRACTICE_BRIEF", "assessmentStatus": "NOT_QUALIFIED", "evidenceUse": "NONE", "aiPolicy": "AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior.", "notice": "Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included.", "outcomeEvidence": "Tests, patches, and runbooks are requested deliverables. They become Outcome Evidence only through a qualified Mission and immutable Evidence IDs.", "ownershipEvidence": "Independent adaptation must be observed under a declared verification policy and cite immutable Evidence IDs. Completing a planning ticket establishes no Ownership Evidence." }, "patternTopics": [ { "id": "factory-method", "label": "Factory Method", "group": "Creational" }, { "id": "abstract-factory", "label": "Abstract Factory", "group": "Creational" }, { "id": "builder", "label": "Builder", "group": "Creational" }, { "id": "prototype", "label": "Prototype", "group": "Creational" }, { "id": "singleton", "label": "Singleton", "group": "Creational" }, { "id": "adapter", "label": "Adapter", "group": "Structural" }, { "id": "bridge", "label": "Bridge", "group": "Structural" }, { "id": "composite", "label": "Composite", "group": "Structural" }, { "id": "decorator", "label": "Decorator", "group": "Structural" }, { "id": "facade", "label": "Facade", "group": "Structural" }, { "id": "flyweight", "label": "Flyweight", "group": "Structural" }, { "id": "proxy", "label": "Proxy", "group": "Structural" }, { "id": "chain-of-responsibility", "label": "Chain of Responsibility", "group": "Behavioral" }, { "id": "command", "label": "Command", "group": "Behavioral" }, { "id": "interpreter", "label": "Interpreter", "group": "Behavioral" }, { "id": "iterator", "label": "Iterator", "group": "Behavioral" }, { "id": "mediator", "label": "Mediator", "group": "Behavioral" }, { "id": "memento", "label": "Memento", "group": "Behavioral" }, { "id": "observer", "label": "Observer", "group": "Behavioral" }, { "id": "state", "label": "State", "group": "Behavioral" }, { "id": "strategy", "label": "Strategy", "group": "Behavioral" }, { "id": "template-method", "label": "Template Method", "group": "Behavioral" }, { "id": "visitor", "label": "Visitor", "group": "Behavioral" }, { "id": "ports-and-adapters", "label": "Ports and Adapters", "group": "Architectural" }, { "id": "cqrs", "label": "CQRS", "group": "Architectural" }, { "id": "strangler-fig", "label": "Strangler Fig", "group": "Architectural" }, { "id": "saga", "label": "Saga", "group": "Distributed and reliability" }, { "id": "transactional-outbox", "label": "Transactional Outbox", "group": "Distributed and reliability" }, { "id": "circuit-breaker", "label": "Circuit Breaker", "group": "Distributed and reliability" }, { "id": "bulkhead", "label": "Bulkhead", "group": "Distributed and reliability" } ], "projects": [ { "key": "SKERNEL", "title": "Build an operating-system boundary that fails predictably", "field": "Systems programming", "summary": "Wrap files, timers and readiness notifications with explicit partial-result and portability behavior.", "context": "A fictional local agent watches generated inbox files and schedules bounded processing. Direct system calls are scattered across the code, mishandle interrupted operations, and make tests platform-dependent. Build a Rust OS adapter with temporary fixture directories; no kernel module, elevated privilege, or production host modification is required.", "stack": [ "Rust", "Filesystem APIs", "Polling adapter", "Temporary directories" ], "prerequisites": [ "System calls", "File descriptors", "Monotonic clocks" ], "developerValue": "Practice OS error semantics, partial I/O, portability and deterministic abstraction boundaries.", "companyValue": "Review host-facing code whose retries, resource limits, and platform differences are explicit before packaging it as a local agent.", "delivery": "Ten linked tickets across three phases. Use synthetic inputs and a local harness; provide source, focused tests, measurements where requested, and a recovery note.", "phases": [ { "id": "model", "title": "Establish the machine contract", "goal": "Make representation, ownership and failure boundaries explicit." }, { "id": "control", "title": "Control resources and concurrency", "goal": "Implement bounded behavior under realistic interleavings." }, { "id": "operate", "title": "Prove recovery and handoff", "goal": "Measure, diagnose and safely replace the component." } ], "tickets": [ { "id": "151c3e66-8557-4dc3-a4d3-05856c347d91", "key": "SKERNEL-101", "title": "Read a file completely across short system calls", "type": "TASK", "priority": "MEDIUM", "difficulty": "FOUNDATIONAL", "estimateMinutes": 90, "phaseId": "model", "dependsOn": [], "scenario": "The adapter assumes one read fills the requested buffer and silently truncates a generated manifest after an injected short read.", "acceptanceCriteria": [ "Loop until EOF, declared length, or typed error", "Return bytes already read only when the contract permits partial results", "Zero-progress reads cannot spin forever" ], "implementationNotes": [ "Use a controllable local read adapter; never require privileged system-call interception." ], "verification": [ "Read the same manifest through one-byte and irregular chunk schedules.", "Return zero progress before EOF and confirm bounded failure." ], "deliverables": [ "Complete-read primitive and short-read tests" ], "rollout": "Route manifest reads through the helper before larger files.", "skills": [ "System calls", "Partial I/O" ], "fieldMix": [ { "field": "Systems programming", "percentage": 70 }, { "field": "Storage systems", "percentage": 30 } ], "patterns": [] }, { "id": "421f63ac-b16f-4489-a9aa-005d9fb8c1f2", "key": "SKERNEL-102", "title": "Write a durable replacement without exposing a half file", "type": "BUG", "priority": "MEDIUM", "difficulty": "FOUNDATIONAL", "estimateMinutes": 90, "phaseId": "model", "dependsOn": [], "scenario": "A crash between truncation and write leaves the agent configuration empty.", "acceptanceCriteria": [ "Write to a unique file in the destination directory", "Flush file content before atomic replacement where the platform supports it", "Document directory durability and unsupported-platform behavior" ], "implementationNotes": [ "Preserve permissions intentionally and reject symlink destination surprises." ], "verification": [ "Replace an existing fixture and observe either old or complete new content.", "Interrupt before rename and confirm the destination remains unchanged." ], "deliverables": [ "Atomic-replace adapter and interruption cases" ], "rollout": "Retain backups only under an explicit bounded retention policy.", "skills": [ "Filesystem durability", "Atomic replacement" ], "fieldMix": [ { "field": "Systems programming", "percentage": 60 }, { "field": "Storage systems", "percentage": 40 } ], "patterns": [] }, { "id": "0c01553a-b00d-40eb-a862-6026bd1828c6", "key": "SKERNEL-103", "title": "Retry interrupted calls without hiding cancellation", "type": "STORY", "priority": "MEDIUM", "difficulty": "INTERMEDIATE", "estimateMinutes": 150, "phaseId": "model", "dependsOn": [ "SKERNEL-101" ], "scenario": "Every interrupted call is retried automatically, so a cancelled operation keeps waiting after shutdown begins.", "acceptanceCriteria": [ "Retry only declared interrupt errors", "Check cancellation and deadline between attempts", "Preserve noninterrupt error identity" ], "implementationNotes": [ "Retry policy belongs beside the operation contract, not in a catch-all error loop." ], "verification": [ "Inject two interrupts followed by success before deadline.", "Cancel between interrupts and verify no further system call is attempted." ], "deliverables": [ "Interrupt-aware retry helper and cancellation tests" ], "rollout": "Adopt per operation after its retry safety is reviewed.", "skills": [ "Error handling", "Cancellation" ], "fieldMix": [ { "field": "Systems programming", "percentage": 70 }, { "field": "Real-time systems", "percentage": 30 } ], "patterns": [] }, { "id": "98330fc6-80e8-44e1-8ae6-d9014865a065", "key": "SKERNEL-104", "title": "Keep wall-clock changes out of elapsed-time deadlines", "type": "CHORE", "priority": "MEDIUM", "difficulty": "INTERMEDIATE", "estimateMinutes": 150, "phaseId": "control", "dependsOn": [], "scenario": "An NTP correction moves wall time backwards and extends a file-processing deadline by several minutes.", "acceptanceCriteria": [ "Elapsed deadlines use an injected monotonic clock", "User-facing timestamps remain UTC wall time", "Conversion between the two clock domains is prohibited" ], "implementationNotes": [ "Tests advance fake clocks; they do not alter the host clock." ], "verification": [ "Expire a deadline through monotonic advancement.", "Move wall time forward and backward and prove elapsed behavior is unchanged." ], "deliverables": [ "Clock boundary and time-jump tests" ], "rollout": "Migrate deadline call sites before changing displayed timestamps.", "skills": [ "Clocks", "Time modeling" ], "fieldMix": [ { "field": "Systems programming", "percentage": 70 }, { "field": "Real-time systems", "percentage": 30 } ], "patterns": [] }, { "id": "78ac8352-98b8-4f0c-b718-823fae29f5fc", "key": "SKERNEL-105", "title": "Normalize watcher bursts into a bounded rescan request", "type": "TASK", "priority": "HIGH", "difficulty": "ADVANCED", "estimateMinutes": 240, "phaseId": "control", "dependsOn": [ "SKERNEL-102", "SKERNEL-104" ], "scenario": "One editor save produces create, rename, and modify events; the agent processes the same file three times and misses changes after queue overflow.", "acceptanceCriteria": [ "Events trigger idempotent directory reconciliation rather than direct truth", "Burst coalescing has a maximum delay", "Overflow schedules a full bounded rescan and remains visible" ], "implementationNotes": [ "Do not promise identical watcher events across operating systems." ], "verification": [ "Replay create-via-rename and direct-write event sequences with one final reconciliation.", "Overflow the event buffer and confirm a rescan restores the fixture state." ], "deliverables": [ "Watcher reconciliation loop and platform event fixtures" ], "rollout": "Keep periodic scans as a fallback during watcher rollout.", "skills": [ "Filesystem watchers", "Reconciliation", "Portability" ], "fieldMix": [ { "field": "Systems programming", "percentage": 60 }, { "field": "Platform engineering", "percentage": 40 } ], "patterns": [] }, { "id": "caccf725-e955-4cff-a109-f66448a660f8", "key": "SKERNEL-106", "title": "Bound open descriptors while scanning a deep inbox", "type": "BUG", "priority": "HIGH", "difficulty": "ADVANCED", "estimateMinutes": 240, "phaseId": "control", "dependsOn": [ "SKERNEL-101", "SKERNEL-105" ], "scenario": "Recursive scanning opens every subdirectory before closing any, exhausting the process descriptor limit.", "acceptanceCriteria": [ "Traversal has an explicit descriptor and work-queue bound", "Directory handles close on success, skip, and error", "Unreadable entries are reported without aborting unrelated roots" ], "implementationNotes": [ "Use a generated tree and configured low limit; do not change host-wide limits." ], "verification": [ "Scan a deep and wide tree while measuring peak open handles.", "Inject an unreadable directory and repeated short reads, then check cleanup." ], "deliverables": [ "Bounded scanner and descriptor accounting test" ], "rollout": "Start with one configured root and expose incomplete scans.", "skills": [ "Resource bounds", "Directory traversal", "Cleanup" ], "fieldMix": [ { "field": "Systems programming", "percentage": 70 }, { "field": "Performance engineering", "percentage": 30 } ], "patterns": [] }, { "id": "5fce6797-7c0f-451b-84b8-ee5e2ff1ab9d", "key": "SKERNEL-107", "title": "Prevent path traversal through a watched-root handle", "type": "STORY", "priority": "HIGH", "difficulty": "EXPERT", "estimateMinutes": 360, "phaseId": "control", "dependsOn": [ "SKERNEL-102", "SKERNEL-106" ], "scenario": "A path is validated under the inbox, then a directory is replaced with a symlink before open, escaping the allowed root.", "acceptanceCriteria": [ "Operations resolve relative to an already opened trusted root", "Traversal rejects symlinks or verifies each component under declared policy", "Validation and use cannot be separated by an attacker-controlled rename" ], "implementationNotes": [ "Use temporary synthetic directories and no elevated privileges." ], "verification": [ "Open and replace normal nested fixture files through the root handle.", "Race a directory-to-symlink swap and confirm no outside file is read or changed." ], "deliverables": [ "Root-relative filesystem adapter and race regression" ], "rollout": "Fail closed on platforms where the required safe primitive is unavailable.", "skills": [ "Filesystem security", "TOCTOU", "Path handling" ], "fieldMix": [ { "field": "Systems programming", "percentage": 65 }, { "field": "Security", "percentage": 35 } ], "patterns": [] }, { "id": "e34489e6-9281-463d-a64d-613056a4f8cd", "key": "SKERNEL-108", "title": "Expose platform capability instead of silently changing semantics", "type": "CHORE", "priority": "HIGH", "difficulty": "ADVANCED", "estimateMinutes": 240, "phaseId": "operate", "dependsOn": [ "SKERNEL-102", "SKERNEL-105" ], "scenario": "The Windows fixture cannot provide the same directory-flush guarantee as the Unix adapter, but both report durable replacement.", "acceptanceCriteria": [ "Adapter reports exact supported capabilities", "Callers can require a capability and fail before mutation", "Fallback semantics have distinct result codes and documentation" ], "implementationNotes": [ "Do not erase platform differences behind a boolean success value." ], "verification": [ "Run the shared contract against two declared capability fixtures.", "Require directory durability from an unsupported fixture and confirm no replacement starts." ], "deliverables": [ "OS capability model and cross-adapter contract suite" ], "rollout": "Gate each deployment profile on its required capability set.", "skills": [ "Portability", "Capability modeling", "Contract testing" ], "fieldMix": [ { "field": "Systems programming", "percentage": 70 }, { "field": "Platform engineering", "percentage": 30 } ], "patterns": [] }, { "id": "09c90ea3-c784-4dac-b27d-082534c5dbe3", "key": "SKERNEL-109", "title": "Recover an orphaned temporary replacement after restart", "type": "TASK", "priority": "HIGH", "difficulty": "EXPERT", "estimateMinutes": 360, "phaseId": "operate", "dependsOn": [ "SKERNEL-102", "SKERNEL-107", "SKERNEL-108" ], "scenario": "A crash leaves temporary files beside the destination; startup cannot tell whether they are incomplete writes or a replacement ready to finish.", "acceptanceCriteria": [ "Temporary name binds operation identity and expected content hash", "Recovery verifies destination and temporary content before action", "Ambiguous or foreign files remain untouched and visible" ], "implementationNotes": [ "Cleanup is scoped to the opened trusted root and never follows links." ], "verification": [ "Recover before-rename and after-rename crash fixtures idempotently.", "Place a foreign matching-looking file and confirm the agent records but does not delete it." ], "deliverables": [ "Replacement journal and startup reconciliation drill" ], "rollout": "Run recovery in report-only mode before enabling scoped cleanup.", "skills": [ "Crash consistency", "Reconciliation", "Filesystem safety" ], "fieldMix": [ { "field": "Systems programming", "percentage": 70 }, { "field": "Site reliability", "percentage": 30 } ], "patterns": [] }, { "id": "2ecab357-7137-4aa9-a3ae-991a3b30a03e", "key": "SKERNEL-110", "title": "Package the OS adapter without requesting unnecessary privilege", "type": "BUG", "priority": "MEDIUM", "difficulty": "INTERMEDIATE", "estimateMinutes": 150, "phaseId": "operate", "dependsOn": [ "SKERNEL-107", "SKERNEL-108", "SKERNEL-109" ], "scenario": "An installer manifest requests administrator access even though the agent operates only inside a user-selected directory.", "acceptanceCriteria": [ "Document required paths, handles, notifications, and permissions", "Default installation runs as an unprivileged user", "Unavailable optional watcher capability falls back visibly to polling" ], "implementationNotes": [ "Do not install services, modify the registry, or request real privilege in the exercise." ], "verification": [ "Run the packaged local fixture under a restricted temporary account profile.", "Remove watcher capability and verify bounded polling without elevated fallback." ], "deliverables": [ "Privilege inventory, packaging manifest, and fallback test" ], "rollout": "Keep installation local and reversible until platform review is complete.", "skills": [ "Least privilege", "Packaging", "Operational documentation" ], "fieldMix": [ { "field": "Systems programming", "percentage": 70 }, { "field": "DevOps", "percentage": 30 } ], "patterns": [] } ], "id": "4b77692b-e1a3-4649-874d-e84670d9a8ce" } ] }