Giving up for now, probably won't revisit, I'm quite literally getting skill-diffed by some documentation and examples.

todo.md

@@ -1,6 +1,29 @@
 Okay I think I did everything, so to clean up:
 
-- [ ] Update the sync library
+# Fatal Bug
+When building the headers for the async request (_async::r2client::tests::test_create_headers), the final header list is missing the host header.
+
+Check and see if the `aws_signing` function `create_canonical_request_headers`'s output is getting tossed.
+The output of that function includes request and headers with the host headers in there.
+I imagine that, instead of parsing that string to turn into a header map or whatever the `signature` function returns, it is creating it's own "content-type" and "x-amz-date" headers and pushing them to it's own vector
+I needed to come here to think cause I'm tired and would've fucked it up if I just brute forced it instead of critically thought about it
+
+The expected solution is taking the "request", and turning in into a "HeaderMap", since we aren't low enough level to pass unsafe strings by ourselves.
+Technically the output of the canonical_request is correct:
+Request: `"PUT\n/bucket/key\n\ncontent-type:application/octet-stream\nhost:example.r2.cloudflarestorage.com\nx-amz-date:20250907T043710Z\n\ncontent-type;host;x-amz-date\ndeadbeef"`
+However it's not in the format of the vector of strings, and also I don't think there should be a new line after put, but there should be two before the content type. Not sure.
+But that's what the request looks like, then the headers that we could parse as well that the same function returns are as follows:
+Headers: `"content-type:application/octet-stream\nhost:example.r2.cloudflarestorage.com\nx-amz-date:20250907T043710Z\n"`
+Which seems to match up, however the final signature that the main `signature` function returns is:
+Headers: `[("content-type", "application/octet-stream"), ("x-amz-date", "20250907T043710Z"), ("authorization", "AWS4-HMAC-SHA256 Credential=AKIAEXAMPLE/20250907/us-east-1/s3/aws4_request, SignedHeaders=content-type;host;x-amz-date, Signature=cfbed04d8dbd8610b9f621c72d7e86f0dae2ffac3174835b4a1ff23ad072893f")]`
+So my assumption is that the `signature` function is making it's own headers and dropping the canonical ones instead of parsing one of the returned strings into one.
+This is happening before the "authorization" headers (the only headers that the main function should be adding itself) are pushed to the current vector
+I think the headers should be parsed into a Vec<(String, String)>, because that would allow the R2Client to turn the request into whatever header map it wants, or a string, which would hopefully make this AWS signing thing work for other services too, although I won't advertise it as it's own library or anything.
+
+Okay after saying all that, surely I could've just fixed it by now and will remember it in the later.
+
+- [X] Update the sync library
 - [X] Make a .env with test-bucket creds
 - [ ] Actually test the damn thing
 - [ ] Cry (ALL OF THAT WORK, FOR WHAT!? A SINGLE `main.rs` ON GITHUB!?)
+