learn-prompt-engineering-with-phoebe / Builder session 1 of 10
Learn Prompt Engineering with Phoebe · Builder track · Session 1 of 10

The 2026 map: where prompting fits now

Before you learn a single technique, learn the terrain. What order the pros actually work in, where the prompt sits inside the wider context, and the one question that decides which advice applies to your model at all.

🟢 Builder track Practitioners: DA · DE · DS · engineers Any model or API Start here
0-3 · Welcome 3-20 · The map 20-42 · Build-along: TriageBot v0 42-45 · Q&A
Part 0

How this track works

Ten hands-on sessions for people who ship things: analysts, data engineers, data scientists, software engineers. Everything is tool-agnostic - every prompt here runs in any chat UI or any API. And everything is one project: across the whole track we build and harden TriageBot, a support-ticket triage system for Meridian Retail that classifies, summarizes, and routes customer tickets. It starts naive today and ends production-grade in session 10.

Live - presented in session Self-study - read after class ★ Build-along - bring a laptop Any model · any API
★ What you walk out with today The official working order (criteria before prompts, evals before techniques), a clean mental model of where prompting sits inside context engineering, a decision tree that tells you which 2023 advice to unlearn for reasoning models, the six shifts that reshaped this craft - and TriageBot v0, drafted against written success criteria instead of vibes.
Part 1 · the method

Success criteria before prompts 5 min live

Anthropic's prompt engineering docs open with a funnel, not a technique: define success criteria, build empirical evals, draft a prompt - and only then start engineering it. Their official Skilljar API course makes the same move: the evals module comes before the techniques module. That ordering is deliberate, and it is the single biggest habit difference between hobbyists and practitioners.

1 · Define success criteria What does good look like, in numbers? Accuracy, length, tone, latency, cost. 2 · Build empirical evals A test set plus a way to grade it. Even 10 labeled cases beats vibes. 3 · Draft your first prompt Only now. A rough draft is fine - the evals will catch it. 4 · Engineer against evals Iterate with a scoreboard, not a mood. Most people start at step 3 and never leave it. The funnel is the course method: sessions 8-9 build the eval layer in full.
🔍 Click to zoom - the official funnel: criteria → evals → draft → engineer
LiveWhy criteria come first - the practitioner's reason3 min▶

Without written criteria, "better prompt" means "the output I happened to like this afternoon". You will tweak forever because there is no finish line. With criteria, prompt engineering becomes normal engineering:

  • You know when to stop. "Category accuracy at 90% on the test set" is done or not done.
  • You can compare fairly. Two prompt versions, same 10 tickets, count the wins. No memory bias.
  • You can change models safely. When a new model ships, rerun the set. Criteria outlive any one model.
The 10-case rule You do not need an eval framework today. Ten realistic inputs with expected answers, in a spreadsheet, is a legitimate eval. Anthropic's own eval docs say volume of test cases matters more than grading sophistication. We start exactly that small in the build-along.
Self-studyWhere fine-tuning fits - the decision boundary2 min read▶

One boundary mention, once, so it never distracts again: prompting is almost always the first tool, because it is instant, cheap, and reversible. Fine-tuning enters only when you have strong evals proving that prompting has plateaued, plus thousands of examples and a stable task. If you cannot measure the gap, you are not ready to fine-tune - which is another reason the funnel starts with criteria. This track does not cover fine-tuning further; the funnel is the point.

Part 2 · the terrain

Prompting inside context engineering 5 min live

Anthropic's 2025 framing renamed the wider game: context engineering is curating everything that lands in the model's context window - system prompt, retrieved documents, tool outputs, conversation history - aiming for the smallest set of high-signal tokens that gets the job done. The prompt did not get less important. It got a precise job title: it is the one layer of the context you fully control.

The context window - every token the model sees this call Your prompt System + task. The layer you fully control. This course. Retrieved docs RAG chunks, files, search results. Session 5. Tool outputs API results, code runs, DB rows. Session 6. History Earlier turns, notes, compacted summaries. The model Sees only the window. Nothing else exists. Goal per Anthropic: the smallest set of high-signal tokens that maximizes the chance of the outcome you want.
🔍 Click to zoom - the context window and its layers; your prompt is the layer you fully control
LiveWhy the industry renamed the game3 min▶

Three practical consequences of the context-engineering frame, before we zoom back into the prompt layer for the next few sessions:

  • Signal over volume. Stuffing the window hurts. Every irrelevant token competes with the relevant ones. Curation - choosing what NOT to include - is real work.
  • The prompt is the constant. Retrieval varies per query, history grows per turn, tools return whatever they return. Your prompt is the stable contract holding it together - which is why it deserves engineering discipline.
  • Techniques still work. What died was the standalone "prompt engineer" job title, not the skill. The skill got absorbed into every builder role, the way SQL did.
Self-studyThree words you will hear later: compaction, just-in-time retrieval, subagents2 min read▶

Anthropic's context-engineering post names three techniques for keeping windows lean. Today, names only - each gets real treatment later in the track:

  • Compaction: summarizing older history into a short note so long conversations do not drown the window. Session 5.
  • Just-in-time retrieval: fetching documents at the moment they are needed instead of preloading everything. Session 5.
  • Subagents: handing a subtask its own fresh context window and getting back only the conclusion. Session 6.
Part 3 · the fork in the road

Which model class am I prompting? 6 min live

This is the question that decides which advice applies. Reasoning models plan internally before answering; classic prompting tricks that induce planning can now actively hurt them. Standard models still respond to those tricks exactly as the 2023 playbook says. Ask this question first, every time, or you will apply the right technique to the wrong model.

Does the model plan internally? Thinking / reasoning mode on, or a reasoning-first model Yes → reasoning model Keep the prompt simple. State goal + constraints. NO "think step by step" - it plans on its own. Zero-shot first; few-shot examples can HURT. Control depth via effort / reasoning params, not via prompt wording. Full story in session 4. No → standard model The classic playbook works as written. Induced CoT ("think step by step") helps. Few-shot examples: 3-5, diverse, in tags. Explicit structure and detailed instructions pay off. Sessions 2-3 live here. Same task, opposite advice. When output quality surprises you, check which side of this tree you are on first.
🔍 Click to zoom - the model-class decision tree; ask it before applying any technique
Live2023 advice vs 2026 advice, side by side3 min▶
2023 said2026 says (reasoning models)
Always add "think step by step"Never add it - the model plans internally; the phrase can degrade output
More examples = betterZero-shot first; OpenAI measured reasoning models doing worse WITH examples
Spell out the method in detailState the goal, constraints, and success bar; let it choose the method
Tune temperature and top_pUse effort / reasoning parameters; some current models reject sampling params outright
Long elaborate role-play personasShort domain framing; heavy personas demoted by Anthropic's own guidance
Real world

The classic failure: a team upgrades to a reasoning model, keeps their lovingly tuned 2023 mega-prompt full of "think carefully, step 1, step 2" scaffolding - and quality drops. They blame the model. The prompt was fighting the model's own planning. Deleting half the prompt fixed it.

Part 4 · the changelog

The six shifts that reshaped this craft 4 min live

If you learned prompting from a 2023 blog post, here is the diff. One line each - every shift gets its full session later in the track.

#ShiftOne lineWhere
1Reasoning models invert 2023 adviceNo induced CoT, few-shot can hurt, goal over procedure, effort params are the new leverSession 4
2Prompt engineering → context engineeringCurate the whole token ecosystem; the job title died, the skill spread everywhereToday + session 5
3Agentic prompting replaced scaffold promptingNative tool calling killed hand-rolled ReAct loops; the skill is now tool descriptions and harness promptsSession 6
4Security is architecture, not wording"Ignore malicious instructions" is not a defense; injection needs design-level answersSession 10
5Evals are the core practitioner skillPrompt changes are code changes and need regression tests; tips without evals are obsoleteSessions 8-9
6Automated prompt optimization is emergingMetaprompting descendants can draft and improve prompts; a tool to know, not a pillarSession 10
Build-along

Meet TriageBot: criteria first, then v0 ★ 22 min · laptops open

Meridian Retail's support inbox gets hundreds of tickets a day. Our job across this track: a prompt system that classifies each ticket, summarizes it, and routes it - reliably enough to trust. Today we practice the funnel from Part 1 on it: criteria before prompt.

LiveThe raw material: 10 Meridian tickets3 min▶

Your working test set - real inbox energy, typos and rage included. Keep these; they follow us to session 10.

  1. "Charged twice for order #48210, refund one please"
  2. "Where is my parcel?? Ordered 9 days ago, tracking frozen since Tuesday"
  3. "The kettle arrived dented, I want to send it back"
  4. "Your website charged my card but shows no order confirmation???"
  5. "Jacket is lovely but too small - how do I exchange for a size up?"
  6. "Driver left the box in the rain, everything inside is soaked"
  7. "I keep getting someone else's invoices by email, this is the third time"
  8. "Cancel my order if it has not shipped, otherwise ignore this"
  9. "hi"
  10. "Store staff were great but the app deleted my loyalty points AND my last order shows twice on my statement"

Notice tickets 8, 9, and 10: conditional, empty, and genuinely two-category. Every real inbox has them. They exist to punish naive prompts.

TriageBot v0 - the naive draft everyone writes firstCategorize this support ticket: [paste ticket here]
TriageBot v0.1 - the same ask with criteria baked inYou are TriageBot, the support-ticket triage assistant for Meridian Retail. Read the ticket below and output exactly this: Category: one of BILLING, SHIPPING, RETURNS, UNSURE Summary: one sentence, max 25 words, neutral tone Rules: - Use only facts stated in the ticket. Never invent order numbers, names, or amounts. - If the ticket fits no category, fits two equally, or lacks enough information, output UNSURE. Ticket: [paste one ticket here]

Read the 10 raw tickets. Before writing anything, decide what categories even exist. We settle on BILLING, SHIPPING, RETURNS, and UNSURE for everything else - small on purpose.

Write success criteria FIRST. Ours: category accuracy 9/10 or better on the test set · summary 25 words or fewer · neutral tone even when the customer is furious · zero invented order numbers or amounts. Write yours down before touching the prompt.

Draft v0, the naive one. Run the bad box above on tickets 2, 9, and 10. Watch it invent categories you never defined, guess on "hi", and pick one category for ticket 10 without telling you it dropped the other.

Write v0.1 with criteria baked in. Role, enumerated categories, output format, and the UNSURE escape hatch. Run the same three tickets and compare against your written criteria - not against your mood.

Save both versions and the criteria. A file, a gist, anywhere durable. In session 8 those criteria become a real eval, and v0 becomes your baseline to beat on a scoreboard.

The habit this plants Nothing about v0.1 is clever - no technique from later sessions appears in it. It is better purely because the success criteria existed before the prompt did. That ordering, not any phrasing trick, is today's takeaway.
Homework

Three things before session 2 ◐ 25 min total

Source material

What this session covers

Builder-level coverage of the sources below. Official certificates, videos, and quizzes stay with the vendors - links live in the course map.

✓Anthropic docs - prompt engineering overview funnelPart 1 · criteria → evals → draft → engineer (platform.claude.com)
✓Anthropic Skilljar API course - evals module ordered before techniquesPart 1 · the deliberate ordering (anthropic.skilljar.com)
✓Anthropic context engineering post (2025)Part 2 · smallest set of high-signal tokens; compaction / JIT retrieval / subagents named
✓OpenAI reasoning best practices - model-class splitPart 3 · the decision tree; full reasoning treatment in session 4
✓The six 2026 framing shiftsPart 4 · one line each, sessions assigned
◐Fine-tuning vs prompting decision boundaryPart 1 self-study · mention only, by design; not covered further in this track
Check yourself

Three questions before you go 🎯 ◐ 90 seconds

1 · Anthropic's official working order for prompt development is...

The funnel runs criteria → evals → draft → engineer. Their Skilljar course even teaches evals before techniques - the ordering is the method, not an accident.

2 · You are prompting a reasoning model. Which habit should you drop?

Reasoning models plan internally: induced CoT is redundant-to-harmful, and few-shot examples can measurably hurt. Go zero-shot first and steer depth with effort or reasoning parameters.

3 · Context engineering is best described as...

It is the wider discipline of managing the whole token ecosystem. The prompt remains the one layer you fully control - which is exactly why this course exists inside that bigger frame.

Builder session 1 cheat sheet · pin this

The funnelCriteria → evals → draft → engineer. Never start at draft; you will never leave it.
The 10-case ruleTen labeled inputs in a spreadsheet is a real eval. Volume beats grading sophistication.
Context engineeringCurate the whole window - prompt, docs, tools, history - for the smallest high-signal token set.
Your layerThe prompt is the one context layer you fully control. It is the stable contract; engineer it like one.
The treeAsk "does it plan internally?" before any technique. Reasoning and standard models take opposite advice.
Reasoning modelsSimple prompts, goal + constraints, zero-shot first, no "think step by step", steer via effort params.
Standard modelsThe classic playbook holds: induced CoT, 3-5 few-shot examples, explicit structure. Sessions 2-3.
TriageBot v0 lessonv0.1 beat v0 with zero technique - only because written criteria existed first. Criteria are the technique.