Known limitations

Claude Code is a powerful tool, but it has real limitations. Knowing them will save you frustration and help you get the most out of every session.

Context window

Claude Code uses a 200,000 token context window (roughly 150,000 words). That sounds huge, but in practice, this window fills up fast.

What consumes context:

• File contents read by Claude
• Conversation history
• Responses generated by Claude itself
• MCP tools called and their results

The real problem: on a project with more than 50 files, Claude can't keep everything in memory. At the end of a long session, it "forgets" what it read at the beginning.

Hallucinations

Claude can make up information with confidence. This is the most serious problem with any language model, and Claude Code is no exception.

Concrete examples:

• Inventing an API or method that doesn't exist in a library
• Generating code that references a nonexistent npm package
• Claiming a file contains a particular function when it doesn't
• Citing official documentation with incorrect information

The risk: if you accept generated code without verifying it, you introduce subtle bugs that can pass unit tests (because the tests can be hallucinated too).

Code execution and system access

Claude Code can read and write files, execute shell commands, and interact with your system. But there are important limits.

What Claude Code cannot do:

• Access the internet directly (without a dedicated MCP)
• Interact with graphical interfaces (clicking, scrolling)
• Reliably launch long-running background processes
• Handle interactive sessions (like vim or less)
• Access files outside the working directory (unless explicitly configured)

What can go wrong:

• A destructive command (rm -rf, git reset --hard) executed too quickly if you've enabled auto-accept mode
• Cascading file changes that break project consistency
• Shell commands that fail silently, and Claude continues on a wrong basis

Latency and speed

Claude Code is not instant. Every request makes a round trip to Anthropic's servers, and long responses take time to generate.

Typical observed times:

Aggravating factors:

• Extended Thinking adds reasoning time before the response
• More powerful models (Opus) are slower than Sonnet or Haiku
• MCPs add additional network calls
• Throttling on Pro and Max plans limits requests per period

Costs

Claude Code is not free, and costs can climb quickly if you're not careful.

Pricing structure (March 2026):

What gets expensive:

• Long sessions (accumulated context = more tokens)
• Extended Thinking (reasoning tokens billed as output)
• Premium models (Opus costs 5x more than Sonnet)
• MCPs that inject lots of data into the context

Language support

Claude Code understands most popular programming languages, but its competence level varies.

Excellent (comparable to a senior dev):

• Python, TypeScript, JavaScript
• HTML, CSS, SQL
• Bash, shell scripting

Good (comparable to a mid-level dev):

• Java, C#, Go, Rust, C/C++
• Ruby, PHP, Swift, Kotlin

Adequate but limited:

• Rarer languages (Haskell, Erlang, Elixir, Clojure)
• Very recent or niche frameworks
• Proprietary DSLs

The problem: Claude Code was trained on data up to a certain date. Libraries, frameworks, or APIs released after that date are poorly known or unknown. That's where hallucinations are most frequent.

Reasoning limitations

Claude Code can solve complex problems, but it has blind spots.

Where it can fail:

• Subtle bugs involving race conditions or parallelism
• Performance optimizations that require real profiling
• Architectural decisions that depend on unstated business constraints
• Massive refactoring where it loses track of overall consistency
• Complex mathematics or precision numerical computations

The classic pattern: Claude Code excels at the first 80% of a task. The last 20%, the part that demands judgment, experience, or understanding of business context, remains your responsibility.

Summary

Next steps

• Compare Claude Code with alternatives: vs GitHub Copilot and vs Cursor
• Discover situations where another tool would be a better fit: When NOT to use Claude Code
• Learn to work around limitations with better prompts: Prompting basics