Fix Claude Lazy Code: How to Stop Truncated Code Blocks

When using Claude for software engineering, you may notice the model occasionally gets "lazy." Instead of outputting a fully functional script, it will write a partial file and truncate the rest using placeholders like // TODO: implement helper functions here, // ... rest of your code ..., or /* insert code here */.

This behavior is highly frustrating when you need a clean, copy-pasteable script. It usually happens because Claude is trying to conserve its output token limit or because the conversation context has grown too large. Here is how to force Claude to write complete, un-truncated code.

Why Claude Uses Code Placeholders

Claude is trained to be highly efficient. Generating long, repetitive blocks of code consumes a significant amount of compute and time. If Claude detects that a portion of the code has not changed from your previous prompt, it will replace it with a comment to save output tokens. While this is helpful for brief edits, it breaks your workflow when you need complete files for deployment or testing.

How to Force Claude to Write Complete Code

Follow these sequential troubleshooting steps to stop Claude from skipping code blocks.

1. Use the "No Omissions" Directive Add a highly specific constraint to your prompt that explicitly bans the use of comments as placeholders. You must be firm and unambiguous.

• Copy-paste this constraint to your prompt: "Write the entire file out completely. Do not use placeholders, comments like '// ... rest of code', or 'TODOs'. Every single line of code must be fully written out from start to finish. Do not omit any helper functions or imports."

2. Configure a Custom Instruction in Projects If you are using Claude Pro, you can set up a Project and add a custom instruction. This ensures that every chat within that project automatically enforces complete code generation.

1. Open your Project in Claude.ai.
2. Click on Project Instructions in the right-hand panel.
3. Paste the following instruction: *"The user requires production-ready, fully written code. Never use placeholder comments, elliptical code blocks, or 'left as an exercise' notes. Always output the entire file containing both modified and unmodified sections."*
4. Click Save.
5. Start a new chat inside that project to apply the changes.

3. Clear Chat History (Reduce Context Load) As a chat session grows longer, Claude's attention window becomes saturated. To save processing power and keep its response speed high, it will naturally start summarizing and truncating code.

• Action: If Claude starts skipping code in a long chat, copy your current codebase, click New Chat, paste the code, and ask for your next edits in a fresh session. Clearing the context window instantly reduces the model's tendency to truncate outputs.

4. Request Modular Code Blocks If you ask Claude to write a 1,000-line file all at once, it will almost certainly use placeholders because it is approaching its maximum output token limit (which is typically 4,096 or 8,192 tokens depending on the model version).

• Action: Instead of asking for the whole file, break your request into modular components. For example, ask Claude to:
• "Write the interface and data models first."
• "Now, write the API client implementation for those models."
• "Write the test cases for the API client."

5. Run a "Refill" Follow-up Prompt If Claude has already outputted a lazy code block with placeholders, do not try to manually write the missing parts. You can command Claude to fill in its own gaps.

• Prompt: "In your previous response, you used placeholders in lines 45-60. Rewrite that entire code block now, but write out the complete, actual code for those lines without any placeholders or abbreviations."

When to Escalate

If Claude consistently fails to output complete code despite strict instructions, you may be hitting hard technical constraints.

• Verify Model Version: Ensure you are using Claude 3.5 Sonnet rather than Claude 3 Haiku, as Sonnet has a much larger output capacity and is far better at adhering to complex, multi-step instructions.
• Check Output Token Limits: If your requested file is extremely large, Claude may be physically running out of output tokens before it can finish writing. In this case, you must design your software architecture to be more modular so files stay under 300–400 lines of code.