Sonnet 4.5 blows my mind

Sunday, October 5th 2025
So, I'm building a multiplaye game you can play in the termial with Claude Code.
With most of the project in place, I decided to add rate limiting.

TLDR;
I am amazed by Claude approach to this task:
  1. What is this project I am looking at?
  2. Is there anything already in place I can use?
  3. What are the existing dependencies?
  4. Let me try YOLO it
  5. Ok, let me read the docs
  6. Actually, let me try YOLO it again
  7. Ok, let me read the docs
  8. Nope... I need some example
  9. Can't find example, let me look it up
  10. Mmmh... Nope... I'm missing something, let me take a look at the public interface of the crate
  11. Oh I see
  12. Cool, let me clean up
  13. Done, and oh, btw, here's a summary and some notes I left you
All of this in the time it took me to smoke a cigarette while hanging out in my yard, taking in the morning sun.
It's so, damn, cool.

The following is the (abbreviated) log of what Claude did, with some comments:
> let's implement api rate limiting 

⏺ I'll help you implement API rate limiting. Let me first examine your codebase to understand the current API structure.

⏺ Search(pattern: "**/*.py")
⏺ Search(pattern: "**/requirements*.txt")
⏺ Search(pattern: "**/pyproject.toml")
⏺ Bash(find /Users/curzel/dev/battld -type f -name "*.py" | head -20)
⏺ Read(server/install.py)
It got fooled into thinking this is a python codebase due to install.py being open in Visual Studio Code, but that's actually a script that sets up the server, and after reading it, it know knows this is a Rust codebase: 
⏺ Bash(ls -la /Users/curzel/dev/battld)
⏺ Bash(ls -la /Users/curzel/dev/battld/server)
⏺ Bash(ls -la /Users/curzel/dev/battld/server/src)
⏺ Read(server/src/main.rs)
⏺ Read(server/Cargo.toml)

⏺ I'll implement API rate limiting using tower-governor, a popular rate limiting middleware for Axum. Let me start by adding the
  dependency.
Nothing unusual so far, it sniffed around the project, found tower was being used for other things and opted for tower-governor: 
⏺ Update(server/Cargo.toml)
Skipping over the detail of the actual implementation here, but at a certain points it decides to see if the codebase builds correctly: 
⏺ Update(server/src/rate_limit.rs)
⏺ Bash(cargo build --bin server 2>&1 | tail -50)
  ⎿     Compiling server v0.1.0 (/Users/curzel/dev/battld/server)                                  
     error[E0412]: cannot find type `DefaultDirectRateLimiter` in module `tower_governor::governor`
       --> server/src/rate_limit.rs:11:94
     … +7 lines (ctrl+o to expand)
Build fails, seems it hallucinated some API 
⏺ Let me check the tower_governor documentation to find the correct type:

⏺ Update(server/src/rate_limit.rs)

⏺ Bash(cargo build --bin server 2>&1 | tail -50)
  ⎿  error[E0425]: cannot find function, tuple struct or tuple variant `Json` in this scope
       --> server/src/rate_limit.rs:32:9
        |
     … +47 lines (ctrl+o to expand)
It said "let me check the documentation", but doesn't look like it actually did, he just tried some other approach instead, but let's continue 

⏺ Read(server/src/rate_limit.rs)
⏺ Write(server/src/rate_limit.rs)

⏺ Bash(cargo build --bin server 2>&1 | tail -50)
  ⎿    --> /Users/curzel/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tower_governor-0.4.3/src/lib.rs:30:8
        |
     27 | pub struct GovernorLayer<K, M>
     … +53 lines (ctrl+o to expand)

⏺ Let me use a simpler approach with tower_governor:
Simpler approach is always welcome as a solution, worth a shot (but still didn't read the docs) 
⏺ Write(server/src/rate_limit.rs)

⏺ Bash(cargo build --bin server 2>&1 | grep -A 5 "error\|Finished")
  ⎿  error[E0412]: cannot find type `DefaultDirectRateLimiter` in module `tower_governor::governor`
       --> server/src/rate_limit.rs:10:94
        |
     … +6 lines (ctrl+o to expand)

⏺ Let me check the tower_governor version and use the correct API:

⏺ Fetch(https://docs.rs/tower_governor/0.4.0/tower_governor/)
  ⎿  Received 38KB (200 OK)

⏺ Perfect! Now I understand the correct API:
Omg it did it! 
⏺ Write(server/src/rate_limit.rs)
⏺ Bash(cargo build --bin server 2>&1 | grep -E "(error|warning:|Finished)" | head -20)
⏺ Bash(cargo build --bin server 2>&1 | grep -A 10 "error\[")
⏺ Write(server/src/rate_limit.rs)

⏺ Bash(cargo build --bin server 2>&1 | grep -E "(error|warning:|Finished)")
  ⎿  error[E0433]: failed to resolve: could not find `middleware` in `governor`
     error[E0433]: failed to resolve: could not find `clock` in `governor`
     For more information about this error, try `rustc --explain E0433`.
     error: could not compile `server` (bin "server") due to 2 previous errors
Still something wrong, it now tries a slightly different approach 
⏺ Let me use type inference instead:

⏺ Write(server/src/rate_limit.rs)
  ⎿  Updated server/src/rate_limit.rs with 1 addition and 1 removal                                                
        ...

⏺ Bash(cargo build --bin server 2>&1 | tail -20)
  ⎿  error[E0277]: `<impl Layer<Route> as Layer<Route>>::Service` cannot be sent between threads safely
        --> server/src/main.rs:76:16
         |
     … +18 lines (ctrl+o to expand)

⏺ Let me check the latest tower_governor examples more carefully:
The docs didn't help, so now it searches for an example. 
⏺ Fetch(https://github.com/benwis/tower-governor/blob/main/tower-governor/examples/axum.rs)
  ⎿  Error: Request failed with status code 404
Likely an hallucinated or old link 
⏺ Web Search("tower_governor axum 0.4 example GovernorLayer usage")
  ⎿  Did 1 search in 17s
Nice! 
⏺ Now I understand - I need to use .into_make_service_with_connect_info::<SocketAddr>() and the simple configuration. Let me update
   the code:

⏺ Write(server/src/rate_limit.rs)
⏺ Now I need to update the main.rs to use into_make_service_with_connect_info:
⏺ Read(server/src/main.rs)
⏺ Update(server/src/main.rs)
⏺ Update(server/src/main.rs)
⏺ Update(server/src/main.rs)
⏺ Bash(cargo build --bin server 2>&1 | tail -30)
⏺ Write(server/src/rate_limit.rs)
⏺ Bash(cargo build --bin server 2>&1 | grep -E "(error|warning:|Finished)")
⏺ Let me check the actual tower_governor source to find the correct middleware type:
⏺ Bash(cargo tree -p tower_governor 2>&1 | head -5)
⏺ Bash(cargo doc --package tower_governor --no-deps --open 2>&1 | head -20) timeout: 1m 0s
⏺ Let me simplify and use the type inference properly:
⏺ Write(server/src/rate_limit.rs)
⏺ Bash(cargo build --bin server 2>&1 | grep -A 3 "error\[")
  ⎿  error[E0433]: failed to resolve: could not find `middleware` in `governor`
      --> server/src/rate_limit.rs:6:93
       |
     … +6 lines (ctrl+o to expand)
It failed again! But it still has one ace up the sleeve.... 

⏺ Let me check what's actually exposed by the crate:

⏺ Bash(cat /Users/curzel/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tower_governor-0.4.3/src/lib.rs | head -100)
  ⎿  #![doc = include_str!("../README.md")]

     #[cfg(test)]
     … +97 lines (ctrl+o to expand)

⏺ I see! The NoOpMiddleware is re-exported from ::governor, not tower_governor::governor. Let me fix this:
I'm loving this. 
⏺ Write(server/src/rate_limit.rs)
⏺ Bash(cargo build --bin server 2>&1 | grep -E "(error|warning:|Finished)")
⏺ I need to add the governor crate dependency:
⏺ Update(server/Cargo.toml)
⏺ Bash(cargo build --bin server 2>&1 | tail -20)
  ⎿     Compiling server v0.1.0 (/Users/curzel/dev/battld/server)
     warning: unused import: `ConnectInfo`
      --> server/src/main.rs:6:21
     … +8 lines (ctrl+o to expand)
  ⎿  Found 2 new diagnostic issues in 1 file (ctrl-o to expand)

⏺ Excellent! It compiled! Let me clean up the code I wrote:
Finally! 
⏺ Update(server/src/main.rs)
⏺ Bash(cargo build --bin server 2>&1 | tail -5) timeout: 1m 0s
⏺ Perfect! Now let me create a brief documentation comment in the .notes file to explain how to configure the rate limiting:
⏺ Read(.notes)
⏺ Update(.notes)
⏺ Perfect! API rate limiting has been successfully implemented. Here's a summary of what was done:
Good sport, thanks 

  Implementation Summary

  ✅ Added Dependencies
  - tower_governor = "0.4" for rate limiting middleware
  - governor = "0.6" for the rate limiting algorithm

  ✅ Created Rate Limiting Module (server/src/rate_limit.rs:1-26)
  - Configurable via RATE_LIMIT_RPS environment variable
  - Default: 10 requests per second per IP address
  - Burst size: 2x the rate limit (20 requests by default)
  - Uses PeerIpKeyExtractor to identify clients by IP address

  ✅ Applied to API Routes (server/src/main.rs:68-85)
  - Rate limiting applied to all API endpoints:
    - /player (POST & GET)
    - /player/current
    - /player/:id
    - /matches/active
    - /stats
    - /leaderboard
  - WebSocket and static file routes are not rate limited
  - Updated server to use into_make_service_with_connect_info::<SocketAddr>() for IP extraction

  ✅ Configuration
  - Added RATE_LIMIT_RPS option to .env file
  - Default of 10 requests/second if not configured
  - Easy to adjust per environment

  The rate limiter tracks requests per IP address and will return a 429 Too Many Requests response when the limit is exceeded.
All tests passing, runs, works. One-shotted!