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Am I the only one who spends more time debugging prompts than writing chain logic?

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(@code_reviewer_anna_v2)
Estimable Member
Joined: 3 months ago
Posts: 126
Topic starter   [#17833]

Okay, I have to ask... is anyone else in this boat? 🙋‍♀️ I started using LangChain to *save* time on orchestration, but lately I feel like I'm spending 80% of my effort just tweaking and debugging prompts, not building cool chains.

My chain logic is clean! But then I plug in a `ChatPromptTemplate` and the LLM goes off-script. It's a cycle of: run chain, get weird output, add another line to the system prompt to forbid that behavior, repeat. It feels like whack-a-mole.

For example, I built a simple extraction chain. The logic to format the schema and parse the output is maybe 20 lines. But getting the prompt right took forever. Here's the kind of iterative debugging I mean:

**Prompt Attempt 1 (Too vague):**
```python
system_template = "Extract the entities from the user's text."
# LLM responded with: "Here are the entities I found: ..." and then narration.
```

**Prompt Attempt 3 (Better, but not perfect):**
```python
system_template = """
Extract entities. Return ONLY a valid JSON object. Use the keys "people" and "companies".
Do not add any explanatory text.
Example: {"people": ["Alice"], "companies": ["ACME Corp"]}
"""
# LLM mostly worked, but sometimes added a trailing comma causing JSON decode errors.
```

I've started keeping a "prompt debugging" journal with failed outputs and the fixes. Best practices I'm trying to stick to now:
* **Be exhaustively explicit** about format, even stating "no markdown, no code fences."
* **Use structured output parsers (Pydantic)** wherever possibleβ€”they help a ton.
* **Include negative instructions** ("Do not...") based on past failures.
* **Write multi-shot examples** that cover edge cases I've encountered.

It's powerful when it works, but the prompt engineering feels like a separate, fragile layer. Are you all having the same experience? What's your process for stabilizing prompts? Do you just accept this as the core task now?

Happy coding!


Clean code, happy life


   
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(@integration_tinkerer)
Estimable Member
Joined: 3 months ago
Posts: 104
 

Oh yeah, that cycle is way too familiar. I've started treating prompt engineering like a separate integration layer, almost like tuning an API connector.

One thing that's helped me is building a small "prompt test harness" for each chain - a simple script that runs the same prompt across 5-10 edge case inputs and logs the failures. Saves you from the manual run/tweak loop.

Also, I've found that sometimes it's not the prompt, it's the temperature setting. I'll burn an hour on wording, then realize dropping from 0.7 to 0.3 fixes 90% of the "going off-script" issues. 😅



   
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