Change x-synthetic-trusted-server header to x-psid-ts (#66)

Author: ChristianPavilonis

crates/common/README.md

@@ -51,8 +51,8 @@ Behavior is covered by an extensive test suite in `crates/common/src/creative.rs
 
 - `synthetic.rs` generates a deterministic synthetic identifier per user request and exposes helpers:
   - `generate_synthetic_id` — creates a fresh HMAC-based ID using request signals.
-  - `get_synthetic_id` — extracts an existing ID from the `X-Synthetic-Trusted-Server` header or `synthetic_id` cookie.
+  - `get_synthetic_id` — extracts an existing ID from the `x-psid-ts` header or `synthetic_id` cookie.
   - `get_or_generate_synthetic_id` — reuses the existing ID when present, otherwise creates one.
-- `publisher.rs::handle_publisher_request` stamps proxied origin responses with `X-Synthetic-Fresh`, `X-Synthetic-Trusted-Server`, and (when absent) issues the `synthetic_id` cookie so the browser keeps the identifier on subsequent requests.
+- `publisher.rs::handle_publisher_request` stamps proxied origin responses with `X-Synthetic-Fresh`, `x-psid-ts`, and (when absent) issues the `synthetic_id` cookie so the browser keeps the identifier on subsequent requests.
 - `proxy.rs::handle_first_party_proxy` replays the identifier to third-party creative origins by appending `synthetic_id=<value>` to the reconstructed target URL, follows redirects (301/302/303/307/308) up to four hops, and keeps downstream fetches linked to the same user scope.
 - `proxy.rs::handle_first_party_click` adds `synthetic_id=<value>` to outbound click redirect URLs so analytics endpoints can associate clicks with impressions without third-party cookies.

crates/common/src/constants.rs

@@ -3,8 +3,7 @@ use http::header::HeaderName;
 pub const HEADER_SYNTHETIC_FRESH: HeaderName = HeaderName::from_static("x-synthetic-fresh");
 pub const HEADER_SYNTHETIC_PUB_USER_ID: HeaderName = HeaderName::from_static("x-pub-user-id");
 pub const HEADER_X_PUB_USER_ID: HeaderName = HeaderName::from_static("x-pub-user-id");
-pub const HEADER_SYNTHETIC_TRUSTED_SERVER: HeaderName =
-    HeaderName::from_static("x-synthetic-trusted-server");
+pub const HEADER_SYNTHETIC_TRUSTED_SERVER: HeaderName = HeaderName::from_static("x-psid-ts");
 pub const HEADER_X_CONSENT_ADVERTISING: HeaderName =
     HeaderName::from_static("x-consent-advertising");
 pub const HEADER_X_FORWARDED_FOR: HeaderName = HeaderName::from_static("x-forwarded-for");

crates/common/src/synthetic.rs

@@ -83,7 +83,7 @@ pub fn generate_synthetic_id(
 /// Gets or creates a synthetic ID from the request.
 ///
 /// Attempts to retrieve an existing synthetic ID from:
-/// 1. The `X-Synthetic-Trusted-Server` header
+/// 1. The `x-psid-ts` header
 /// 2. The `synthetic_id` cookie
 ///
 /// If neither exists, generates a new synthetic ID.

crates/js/README.md

@@ -111,7 +111,7 @@ The Rust services (`trusted-server-common`) expose several proxy entry points th
 
 - Endpoint: `handle_publisher_request` (`crates/common/src/publisher.rs`).
 - Retrieves or generates the trusted synthetic identifier before Fastly consumes the request body.
-- Always stamps the proxied response with `X-Synthetic-Fresh` and `X-Synthetic-Trusted-Server` headers and, when the browser does not already present one, sets the `synthetic_id=<value>` cookie (Secure + SameSite=Lax) bound to the configured publisher domain.
+- Always stamps the proxied response with `X-Synthetic-Fresh` and `x-psid-ts` headers and, when the browser does not already present one, sets the `synthetic_id=<value>` cookie (Secure + SameSite=Lax) bound to the configured publisher domain.
 - Result: downstream assets fetched through the same first-party origin automatically include the synthetic ID header/cookie so subsequent proxy layers can read it.
 
 ### Creative Asset Proxy