The request depends on a session
An access token can expire or depend on a refresh token, cookie, account role, or device session. Copying the final request skips the steps that created that state.
Check the full login and refresh sequence. Record when each value is issued and which calls consume it. A successful public endpoint does not prove access to private account data.
Signed headers change with the request
A signature can depend on the method, path, body, timestamp, nonce, or session. Editing one field changes the input to the signature.
Compare requests with controlled changes to one input at a time. Keep the exact bytes used to build the request. JSON spacing, field order, and character encoding matter when the signing scheme includes the raw body.
The device is part of the flow
Some services check device state or integrity results before accepting a call. These values are part of the request flow and need to be tested in the intended setup.
A token copied from one device is not proof that a server client can create a fresh valid session. Keep device-bound and server-side behavior separate in the delivery notes.
Encrypted bodies need the right context
The app can encrypt a payload before sending it. The key, nonce, initialization vector, encoding, and session context determine the final body.
Reading plaintext before encryption explains the data structure. It does not prove that a rebuilt client produces the same accepted payload. Test the full request and response path.
Read the failure before changing the code
A 401 response directs attention to authentication, but read the API error as well. A 403 can reflect access rules or a rejected request context. A 400 points to request validation. A 429 calls for the service’s retry policy. A 5xx response needs comparison with a working app request at the same time.
These codes narrow the investigation; they do not name the root cause by themselves. Some APIs return an error object inside HTTP 200. Save the body shape and request ID, then test the hypothesis against a known working request.
For a repeatable comparison, keep the account, endpoint, input, and test time fixed. Change one dependency and record the result. A fresh session working while the old one fails is stronger evidence than five retries with the same token.
Use errors to narrow the cause
Record the status code, response body, request ID, and timing. Remove secrets before sharing logs. Compare a known working request with the failing one.
Test one change at a time: fresh session, unchanged body, correct content type, then required headers. Repeating the same failing request hides the missing dependency.
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