# Site

## Pages

- [Page not found](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/404/): That page doesn't exist, or it has moved since you last looked
- [Assessment](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/assessments/): Every piece of graded work in the course, what it is worth, and when it is due.
- [Broken Service Investigation](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/assessments/broken-service-investigation/): An unfamiliar multi-module service, no onboarding document, and a symptom report rather than a diagnosis — with at least two plausible root causes waiting in the evidence.
- [Debugging Field Notes](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/assessments/debugging-field-notes/): Four short, staged entries across Weeks 1–4 — the transition from guided practice to graded investigation, on systems small enough to read in full.
- [Final Unknown System](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/assessments/final-unknown-system/): A previously unseen inherited system, no instructor framing of what matters, and a short live defence of the entire evidence trail.
- [Incident Reconstruction](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/assessments/incident-reconstruction/): A system that looks fine now, a bundle of historical and operational artefacts, and a requirement to reason across time before touching anything.
- [Course Overview](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/course/): Why diagnosing someone else's software is a distinct skill, the method the course teaches it through, who it's for, and what it deliberately leaves out.
- [Lectures](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/lectures/): What is covered, week by week, and which topics each lecture draws on.
- [Observation Before Explanation](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/lectures/week-01/): What this course is, why it is shaped as an investigation rather than a syllabus, and what a student needs to have ready before Week 1's session.
- [Proving a Hypothesis Wrong on Purpose](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/lectures/week-02/): Why a hypothesis needs a disconfirming test to count as one, and how Debugging Field Notes turns that habit into the semester's first graded work.
- [A Model Is a Claim, Not a Map](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/lectures/week-03/): How to build a working model of a system's intended behaviour when there is no one left to explain it, and why structural reading has to do the work documentation used to.
- [Instrumentation Is a Hypothesis Too](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/lectures/week-04/): What runtime evidence can tell you that reading the code cannot, and why instrumentation only counts as investigation when a structural model decided where to place it.
- [Timing Is a Lead, Not a Verdict](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/lectures/week-05/): Why a system's history counts as evidence, and why the change that sits closest in time to a failure is not automatically the change that caused it.
- [Discriminating Between Explanations](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/lectures/week-06/): How to choose between two explanations that both fit the evidence you already have, by asking what each one predicts under a change you control rather than what each is merely consistent with.
- [A Fact Needs a Source Before a Verdict](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/lectures/week-07/): What to do when two pieces of evidence contradict each other — and why that is a different problem from two hypotheses that both fit the same, trustworthy evidence.
- [The Blast Radius of a Fix](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/lectures/week-08/): Why removing a symptom is not the same as knowing a fix is safe, and how to reason about what an intervention might disturb before applying it.
- [What Does This Test Actually Prove?](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/lectures/week-09/): Why a disappeared symptom and a passing smoke test are evidence for a narrower claim than "the diagnosed cause is fixed," and how to verify the claim that actually matters.
- [Choosing Where to Begin](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/lectures/week-10/): How to plan an investigation into a large, unfamiliar system when nobody tells you which component, file, or evidence source to start with.
- [How Much Should You Trust the System?](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/lectures/week-11/): What changes when the system's own evidence cannot be trusted at face value — and why the answer is calibrated confidence, not blanket distrust.
- [The Weakest Link in the Chain](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/lectures/week-12/): What it means to defend an investigation rather than merely present one, and how to find the weakest link in a reasoning chain — including your own.
- [People](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/people/): Who teaches the course, and how to reach them.
- [Idris Fenn](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/people/idris-fenn/): A tutor working across the course's first reviews and the practical work that follows them.
- [Marisol Quaye](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/people/marisol-quaye/): The founding convenor, responsible for the course's shape and its weekly teaching programme.
- [Policies and support](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/policies/): The course-wide rules for late work, extensions, academic integrity and getting help.
- [Naming What You See](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/sessions/01-naming-what-you-see/): What is the difference between an observation and an assumption? The semester's first session works on a system small enough to read in one sitting, so the discipline — not the difficulty — is the point.
- [A Hypothesis That Could Be Wrong](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/sessions/02-a-hypothesis-that-could-be-wrong/): What makes a hypothesis useful, as opposed to merely plausible? A reproducible failure with two similar-looking causes forces a real choice, and the choice has to be committed to before it's tested.
- [Reading a System You Weren't Given a Map To](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/sessions/03-reading-a-system-you-werent-given-a-map-to/): How do you build a working model of a system's intended behaviour when no one is going to explain it to you? Documentation stops being a reliable evidence source from this session onward.
- [Evidence That Isn't Static Text](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/sessions/04-evidence-that-isnt-static-text/): What can runtime evidence tell you that reading the code cannot? The fault this week only shows up under specific runtime conditions, so evidence has to be generated, not just read.
- [What the System Used to Be](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/sessions/05-what-the-system-used-to-be/): Can a fault be explained by something that is no longer in the code at all? This session treats version history and prior configuration as first-class evidence, not background.
- [Two Explanations, One Fault](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/sessions/06-two-explanations-one-fault/): How do you choose between two hypotheses that both fit the evidence you have so far? This session's failure has two genuinely plausible causes, and stopping at the first one that fits is the mistake being taught against.
- [When the Evidence Disagrees](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/sessions/07-when-the-evidence-disagrees/): What do you do when two pieces of evidence appear to contradict each other? This session's evidence itself is unreliable in places, which is a different problem from an unresolved hypothesis.
- [The Fix That Isn't Safe](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/sessions/08-the-fix-that-isnt-safe/): How do you decide whether an available fix is acceptable, not just whether it makes the symptom go away? The diagnosis this week is deliberately easy to reach; the risk is entirely in the fix.
- [Verifying You Didn't Just Move the Problem](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/sessions/09-verifying-you-didnt-just-move-the-problem/): How do you know an intervention actually resolved the cause, rather than relocating or masking the symptom? This session's fix looks like it worked — closer verification is what the week is actually testing.
- [No One Left to Ask](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/sessions/10-no-one-left-to-ask/): How do you investigate a system when the people who built it, and much of its context, are simply gone? Scaffolding drops substantially from this session onward.
- [The System That Fights Back](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/sessions/11-the-system-that-fights-back/): How do you keep the investigation disciplined when the system itself resists being understood — through unreliable documentation, inconsistent reproduction, or an environment where a careless intervention makes things worse?
- [Defending the Trail](https://comp4020-agentic-coding-studio.github.io/comp4020-ass2-wanghanbo73-create/sessions/12-defending-the-trail/): Can every step of your investigation withstand informed challenge? The final session is a live defence of a complete, unassisted investigation of a system you have never seen before.