https://softwareobservatory.com New entries in the catalog of epistemic sensors for software correctness. en Content licensed CC BY-SA 4.0 — Justin Abrahms justin@abrah.ms (Justin Abrahms) justin@abrah.ms (Justin Abrahms) https://softwareobservatory.com/og.png https://softwareobservatory.com Tue, 25 Aug 2026 00:00:00 +0000 https://softwareobservatory.com/sensors/theorem-proving/ https://softwareobservatory.com/sensors/theorem-proving/ Tue, 25 Aug 2026 00:00:00 +0000 justin@abrah.ms (Justin Abrahms) Justin Abrahms A machine-checked proof that a property holds for all inputs, not just the ones a test happened to exercise. Structural https://softwareobservatory.com/sensors/model-checking/ https://softwareobservatory.com/sensors/model-checking/ Tue, 25 Aug 2026 00:00:00 +0000 justin@abrah.ms (Justin Abrahms) Justin Abrahms Exhaustive exploration of a system’s reachable states against a temporal property. Where a type checker proves a property holds for one step, and statically checked invariants prove a property holds… Structural https://softwareobservatory.com/sensors/static-analysis/ https://softwareobservatory.com/sensors/static-analysis/ Mon, 24 Aug 2026 00:00:00 +0000 justin@abrah.ms (Justin Abrahms) Justin Abrahms Pattern-matching and dataflow analysis over the source without executing it. Covers the space between a linter (style and local patterns) and a type checker (type soundness): null dereferences… Structural https://softwareobservatory.com/sensors/property-based-testing/ https://softwareobservatory.com/sensors/property-based-testing/ Mon, 24 Aug 2026 00:00:00 +0000 justin@abrah.ms (Justin Abrahms) Justin Abrahms You state a property that should hold for every input, and the tool generates inputs trying to break it. Adversarial https://softwareobservatory.com/sensors/load-testing/ https://softwareobservatory.com/sensors/load-testing/ Mon, 24 Aug 2026 00:00:00 +0000 justin@abrah.ms (Justin Abrahms) Justin Abrahms Does the system behave under the traffic it claims to handle? A load test drives generated requests at a target rate and measures what breaks — latency, errors, throughput — before real users do. Runtime https://softwareobservatory.com/sensors/ab-testing/ https://softwareobservatory.com/sensors/ab-testing/ Mon, 24 Aug 2026 00:00:00 +0000 justin@abrah.ms (Justin Abrahms) Justin Abrahms Did users actually behave differently? An A/B test splits traffic between two versions and measures whether the treatment changes a user outcome metric — click-through, conversion, retention… Change https://softwareobservatory.com/sensors/type-checker/ https://softwareobservatory.com/sensors/type-checker/ Sun, 23 Aug 2026 00:00:00 +0000 justin@abrah.ms (Justin Abrahms) Justin Abrahms A Rust compiler saying expected Option<Foo>, found Foo is vastly more useful to an agent than “please reconsider whether this is correct.” This is the first and strongest form of computational… Structural https://softwareobservatory.com/sensors/time-to-repair/ https://softwareobservatory.com/sensors/time-to-repair/ Sun, 23 Aug 2026 00:00:00 +0000 justin@abrah.ms (Justin Abrahms) Justin Abrahms When this component breaks, how long does it take to restore? A sensor of maintainability measured in hours, not in subjective assessment. Evolution https://softwareobservatory.com/sensors/synthetic-monitoring/ https://softwareobservatory.com/sensors/synthetic-monitoring/ Sun, 23 Aug 2026 00:00:00 +0000 justin@abrah.ms (Justin Abrahms) Justin Abrahms Scripted user flows run against the production system around the clock: log in, search, add to cart, check out. Behavioral https://softwareobservatory.com/sensors/statically-checked-invariants/ https://softwareobservatory.com/sensors/statically-checked-invariants/ Sun, 23 Aug 2026 00:00:00 +0000 justin@abrah.ms (Justin Abrahms) Justin Abrahms Invariants the compiler refuses to let you violate: Dafny invariant clauses, Frama-C annotations, JML specs, type-level witnesses like NonEmptyList. Invariants https://softwareobservatory.com/sensors/static-security-analysis/ https://softwareobservatory.com/sensors/static-security-analysis/ Sun, 23 Aug 2026 00:00:00 +0000 justin@abrah.ms (Justin Abrahms) Justin Abrahms Attacking the code before it runs. Taint tracking, dataflow analysis, and pattern-based scanners (Semgrep, CodeQL) ask: “is there any path through this program where an adversary’s input reaches a… Adversarial https://softwareobservatory.com/sensors/snapshot-tests/ https://softwareobservatory.com/sensors/snapshot-tests/ Sun, 23 Aug 2026 00:00:00 +0000 justin@abrah.ms (Justin Abrahms) Justin Abrahms Did observable output change? Not “is it correct” but “did it change” — a sensor for detecting unintended drift in externally observable artifacts. Behavioral https://softwareobservatory.com/sensors/smoke-tests/ https://softwareobservatory.com/sensors/smoke-tests/ Sun, 23 Aug 2026 00:00:00 +0000 justin@abrah.ms (Justin Abrahms) Justin Abrahms The cheapest behavioral check against a live deployment: hit /health, create one record, read it back, delete it. If any step fails, roll back. Behavioral https://softwareobservatory.com/sensors/shadow-traffic/ https://softwareobservatory.com/sensors/shadow-traffic/ Sun, 23 Aug 2026 00:00:00 +0000 justin@abrah.ms (Justin Abrahms) Justin Abrahms Run the new implementation against real inputs without affecting users. A sensor that produces differential evidence with zero user risk. Change https://softwareobservatory.com/sensors/second-agent-review/ https://softwareobservatory.com/sensors/second-agent-review/ Sun, 23 Aug 2026 00:00:00 +0000 justin@abrah.ms (Justin Abrahms) Justin Abrahms An independent agent reviews the first agent’s output. A sensor that applies adversarial pressure to AI-generated code without human-in-the-loop latency. Human Comprehension https://softwareobservatory.com/sensors/schema-validator/ https://softwareobservatory.com/sensors/schema-validator/ Sun, 23 Aug 2026 00:00:00 +0000 justin@abrah.ms (Justin Abrahms) Justin Abrahms Structural coherence at the boundary of the system. OpenAPI/GraphQL schema validation, Terraform plan, Kubernetes admission validation, SQL parser/type checker — all of these answer: is this a valid… Structural https://softwareobservatory.com/sensors/runtime-invariants/ https://softwareobservatory.com/sensors/runtime-invariants/ Sun, 23 Aug 2026 00:00:00 +0000 justin@abrah.ms (Justin Abrahms) Justin Abrahms You don’t need to know how the payment service works. You can observe: “5,213 payments occurred; 17 have no corresponding order transition.” That’s a sensor of correctness without understanding the… Invariants https://softwareobservatory.com/sensors/revert-rate/ https://softwareobservatory.com/sensors/revert-rate/ Sun, 23 Aug 2026 00:00:00 +0000 justin@abrah.ms (Justin Abrahms) Justin Abrahms How often does this area get reverted? A black-box sensor of maintainability — you don’t need to understand FooManagerFactoryImpl, you can observe: 27 changes in six months, 8 reverts, 4 incidents… Evolution https://softwareobservatory.com/sensors/resource-telemetry/ https://softwareobservatory.com/sensors/resource-telemetry/ Sun, 23 Aug 2026 00:00:00 +0000 justin@abrah.ms (Justin Abrahms) Justin Abrahms CPU, memory, IO, network, GC, queues. Traditional monitoring — useful but limited. Low cardinality, low dimensionality, predetermined questions. Resource telemetry is the weakest runtime sensor. Runtime https://softwareobservatory.com/sensors/pre-promotion-invariant-gates/ https://softwareobservatory.com/sensors/pre-promotion-invariant-gates/ Sun, 23 Aug 2026 00:00:00 +0000 justin@abrah.ms (Justin Abrahms) Justin Abrahms Invariants checked at the moment of promotion, before a change can reach users: migrations must be backward-compatible, no PII column may be added without an encryption flag, the new schema must… Invariants