IABTechLab · prk-Jr · Jul 28, 2026 · Jul 29, 2026 · Jul 29, 2026
diff --git a/crates/trusted-server-core/src/config.rs b/crates/trusted-server-core/src/config.rs
@@ -18,8 +18,9 @@ use crate::error::TrustedServerError;
 use crate::integrations::{
     adserver_mock::AdServerMockConfig, aps::ApsConfig, datadome::DataDomeConfig,
     didomi::DidomiIntegrationConfig, google_tag_manager::GoogleTagManagerConfig, gpt::GptConfig,
-    lockr::LockrConfig, nextjs::NextJsIntegrationConfig, osano::OsanoConfig,
-    permutive::PermutiveConfig, prebid, sourcepoint::SourcepointConfig, testlight::TestlightConfig,
+    gpt_diagnostics::GptDiagnosticsConfig, lockr::LockrConfig, nextjs::NextJsIntegrationConfig,
+    osano::OsanoConfig, permutive::PermutiveConfig, prebid, sourcepoint::SourcepointConfig,
+    testlight::TestlightConfig,
 };
 use crate::settings::{IntegrationConfig, Settings};
 
@@ -39,6 +40,7 @@ const DEPLOY_VALIDATED_INTEGRATION_IDS: &[&str] = &[
     "google_tag_manager",
     "datadome",
     "gpt",
+    "gpt_diagnostics",
 ];
 
 /// Typed app-config root used by the `ts` CLI.
@@ -155,6 +157,7 @@ fn validate_enabled_integrations(
     validate_integration::<GoogleTagManagerConfig>(settings, "google_tag_manager")?;
     validate_integration::<DataDomeConfig>(settings, "datadome")?;
     validate_integration::<GptConfig>(settings, "gpt")?;
+    validate_integration::<GptDiagnosticsConfig>(settings, "gpt_diagnostics")?;
 
     Ok(enabled_auction_providers)
 }

diff --git a/crates/trusted-server-core/src/html_processor.rs b/crates/trusted-server-core/src/html_processor.rs
@@ -792,6 +792,56 @@ mod tests {
         );
     }
 
+    #[test]
+    fn gpt_diagnostics_bootstrap_precedes_immediate_bundle_once() {
+        let html = "<html><head><title>Test</title></head><body></body></html>";
+        let mut settings = create_test_settings();
+        settings
+            .integrations
+            .insert_config("gpt_diagnostics", &json!({ "enabled": true }))
+            .expect("should insert GPT diagnostics config");
+
+        let mut config = create_test_config();
+        config.integrations =
+            IntegrationRegistry::new(&settings).expect("should build integration registry");
+
+        let processor = create_html_processor(config);
+        let pipeline_config = PipelineConfig {
+            input_compression: Compression::None,
+            output_compression: Compression::None,
+            chunk_size: 8192,
+        };
+        let mut pipeline = StreamingPipeline::new(pipeline_config, processor);
+        let mut output = Vec::new();
+
+        pipeline
+            .process(Cursor::new(html.as_bytes()), &mut output)
+            .expect("should process HTML");
+        let processed = String::from_utf8(output).expect("should produce valid UTF-8");
+        let bootstrap_marker = "__tsjs_gpt_diagnostics_active";
+        let bundle_marker = "id=\"trustedserver-js\"";
+
+        assert_eq!(
+            processed.matches(bootstrap_marker).count(),
+            1,
+            "should inject the diagnostics bootstrap once"
+        );
+        assert_eq!(
+            processed.matches(bundle_marker).count(),
+            1,
+            "should inject the immediate TSJS bundle once"
+        );
+        assert!(
+            processed
+                .find(bootstrap_marker)
+                .expect("should include diagnostics bootstrap")
+                < processed
+                    .find(bundle_marker)
+                    .expect("should include immediate TSJS bundle"),
+            "should activate diagnostics before the immediate bundle executes"
+        );
+    }
+
     #[test]
     fn test_create_html_processor_url_replacement() {
         let config = create_test_config();

diff --git a/crates/trusted-server-core/src/integrations/gpt_diagnostics.rs b/crates/trusted-server-core/src/integrations/gpt_diagnostics.rs
@@ -0,0 +1,233 @@
+//! GPT runtime diagnostics integration.
+//!
+//! This integration only makes the browser diagnostics module available and
+//! injects its early tab-activation bootstrap. GPT observation and presentation
+//! remain entirely client-side and do not alter ad serving behavior.
+
+use std::sync::Arc;
+
+use error_stack::Report;
+use serde::Deserialize;
+use validator::Validate;
+
+use crate::error::TrustedServerError;
+use crate::settings::{IntegrationConfig, Settings};
+
+use super::{IntegrationHeadInjector, IntegrationHtmlContext, IntegrationRegistration};
+
+const GPT_DIAGNOSTICS_INTEGRATION_ID: &str = "gpt_diagnostics";
+const GPT_DIAGNOSTICS_BOOTSTRAP_JS: &str = include_str!("gpt_diagnostics_bootstrap.js");
+
+/// Configuration for the GPT runtime diagnostics integration.
+#[derive(Debug, Clone, Deserialize, Validate)]
+#[serde(deny_unknown_fields)]
+pub struct GptDiagnosticsConfig {
+    /// Whether the GPT diagnostics browser module is available.
+    #[serde(default)]
+    pub enabled: bool,
+}
+
+impl IntegrationConfig for GptDiagnosticsConfig {
+    fn is_enabled(&self) -> bool {
+        self.enabled
+    }
+}
+
+struct GptDiagnosticsIntegration;
+
+/// Register GPT diagnostics when explicitly enabled.
+///
+/// # Errors
+///
+/// Returns an error when the integration configuration cannot be parsed or
+/// fails validation.
+pub fn register(
+    settings: &Settings,
+) -> Result<Option<IntegrationRegistration>, Report<TrustedServerError>> {
+    let Some(_config) =
+        settings.integration_config::<GptDiagnosticsConfig>(GPT_DIAGNOSTICS_INTEGRATION_ID)?
+    else {
+        return Ok(None);
+    };
+
+    let integration = Arc::new(GptDiagnosticsIntegration);
+    Ok(Some(
+        IntegrationRegistration::builder(GPT_DIAGNOSTICS_INTEGRATION_ID)
+            .with_head_injector(integration)
+            .build(),
+    ))
+}
+
+impl IntegrationHeadInjector for GptDiagnosticsIntegration {
+    fn integration_id(&self) -> &'static str {
+        GPT_DIAGNOSTICS_INTEGRATION_ID
+    }
+
+    fn head_inserts(&self, _ctx: &IntegrationHtmlContext<'_>) -> Vec<String> {
+        vec![format!("<script>{GPT_DIAGNOSTICS_BOOTSTRAP_JS}</script>")]
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use serde_json::json;
+
+    use super::*;
+    use crate::integrations::{IntegrationDocumentState, IntegrationRegistry};
+    use crate::test_support::tests::create_test_settings;
+
+    #[test]
+    fn register_returns_none_without_config() {
+        let settings = create_test_settings();
+
+        let registration = register(&settings).expect("should evaluate diagnostics config");
+
+        assert!(
+            registration.is_none(),
+            "should not register diagnostics without explicit config"
+        );
+    }
+
+    #[test]
+    fn register_returns_none_when_disabled() {
+        let mut settings = create_test_settings();
+        settings
+            .integrations
+            .insert_config(GPT_DIAGNOSTICS_INTEGRATION_ID, &json!({ "enabled": false }))
+            .expect("should insert diagnostics config");
+
+        let registration = register(&settings).expect("should parse diagnostics config");
+
+        assert!(
+            registration.is_none(),
+            "should not register disabled diagnostics"
+        );
+    }
+
+    #[test]
+    fn register_adds_only_immediate_js_and_head_bootstrap() {
+        let mut settings = create_test_settings();
+        settings
+            .integrations
+            .insert_config(GPT_DIAGNOSTICS_INTEGRATION_ID, &json!({ "enabled": true }))
+            .expect("should insert diagnostics config");
+
+        let registration = register(&settings)
+            .expect("should parse diagnostics config")
+            .expect("should register enabled diagnostics");
+
+        assert_eq!(registration.integration_id, GPT_DIAGNOSTICS_INTEGRATION_ID);
+        assert!(
+            !registration.js_deferred,
+            "should load diagnostics immediately"
+        );
+        assert!(!registration.js_disabled, "should include diagnostics JS");
+        assert!(
+            registration.proxies.is_empty(),
+            "should register no proxy routes"
+        );
+        assert!(
+            registration.attribute_rewriters.is_empty(),
+            "should register no attribute rewriters"
+        );
+        assert!(
+            registration.script_rewriters.is_empty(),
+            "should register no script rewriters"
+        );
+        assert!(
+            registration.html_post_processors.is_empty(),
+            "should register no HTML post-processors"
+        );
+        assert!(
+            registration.request_filters.is_empty(),
+            "should register no request filters"
+        );
+        assert_eq!(
+            registration.head_injectors.len(),
+            1,
+            "should register one activation bootstrap"
+        );
+    }
+
+    #[test]
+    fn enabled_registry_includes_diagnostics_in_immediate_modules() {
+        let mut settings = create_test_settings();
+        settings
+            .integrations
+            .insert_config(GPT_DIAGNOSTICS_INTEGRATION_ID, &json!({ "enabled": true }))
+            .expect("should insert diagnostics config");
+
+        let registry = IntegrationRegistry::new(&settings).expect("should build registry");
+
+        assert!(
+            registry
+                .js_module_ids_immediate()
+                .contains(&GPT_DIAGNOSTICS_INTEGRATION_ID),
+            "should include diagnostics in the immediate JS bundle"
+        );
+        assert!(
+            !registry
+                .js_module_ids_deferred()
+                .contains(&GPT_DIAGNOSTICS_INTEGRATION_ID),
+            "should not defer diagnostics listener installation"
+        );
+    }
+
+    #[test]
+    fn head_bootstrap_only_exposes_private_activation_logic() {
+        let integration = GptDiagnosticsIntegration;
+        let document_state = IntegrationDocumentState::default();
+        let context = IntegrationHtmlContext {
+            request_host: "edge.example.com",
+            request_scheme: "https",
+            origin_host: "origin.example.com",
+            document_state: &document_state,
+        };
+
+        let inserts = integration.head_inserts(&context);
+
+        assert_eq!(inserts.len(), 1, "should emit one bootstrap script");
+        assert!(
+            inserts[0].contains("ts_console"),
+            "should read the activation query parameter"
+        );
+        assert!(
+            inserts[0].contains("sessionStorage"),
+            "should persist activation within the tab"
+        );
+        assert!(
+            inserts[0].contains("history.replaceState"),
+            "should remove recognized activation directives"
+        );
+        assert!(
+            inserts[0].contains("__tsjs_gpt_diagnostics_active"),
+            "should expose only the private document activation flag"
+        );
+        assert!(
+            !inserts[0].contains("gptDiagnostics ="),
+            "bootstrap should not expose the public diagnostics API"
+        );
+    }
+
+    #[test]
+    fn config_rejects_unknown_fields() {
+        let mut settings = create_test_settings();
+        settings
+            .integrations
+            .insert_config(
+                GPT_DIAGNOSTICS_INTEGRATION_ID,
+                &json!({ "enabled": true, "typo": true }),
+            )
+            .expect("should insert diagnostics config");
+
+        let error = settings
+            .integration_config::<GptDiagnosticsConfig>(GPT_DIAGNOSTICS_INTEGRATION_ID)
+            .expect_err("should reject unknown diagnostics config fields");
+        let error_text = format!("{error:?}");
+
+        assert!(
+            error_text.contains("typo") || error_text.contains("unknown field"),
+            "error should mention the unknown field: {error:?}"
+        );
+    }
+}
diff --git a/crates/trusted-server-core/src/integrations/gpt_diagnostics_bootstrap.js b/crates/trusted-server-core/src/integrations/gpt_diagnostics_bootstrap.js
@@ -0,0 +1,59 @@
+// Early activation bootstrap for the GPT diagnostics integration.
+//
+// This script intentionally owns only tab-local activation and one-time URL
+// cleanup. The TypeScript integration reads the document flag below and owns
+// all GPT observation, storage, API, and presentation behavior.
+(function () {
+    if (typeof window === "undefined") return;
+
+    var queryName = "ts_console";
+    var storageKey = "tsjs:gptDiagnostics:active";
+    var activeFlag = "__tsjs_gpt_diagnostics_active";
+    var active = false;
+    var directiveRecognized = false;
+    var url;
+
+    try {
+        url = new URL(window.location.href);
+        var value = url.searchParams.get(queryName);
+
+        if (value === "1" || value === "true") {
+            active = true;
+            directiveRecognized = true;
+        } else if (value === "0" || value === "false") {
+            active = false;
+            directiveRecognized = true;
+        }
+    } catch (_) {
+        url = undefined;
+    }
+
+    if (directiveRecognized) {
+        try {
+            window.sessionStorage.setItem(storageKey, active ? "1" : "0");
+        } catch (_) {
+            // The recognized directive still applies to this document.
+        }
+
+        if (url) {
+            url.searchParams.delete(queryName);
+            try {
+                window.history.replaceState(
+                    window.history.state,
+                    "",
+                    url.pathname + url.search + url.hash,
+                );
+            } catch (_) {
+                // URL cleanup is optional and must not block diagnostics activation.
+            }
+        }
+    } else {
+        try {
+            active = window.sessionStorage.getItem(storageKey) === "1";
+        } catch (_) {
+            active = false;
+        }
+    }
+
+    window[activeFlag] = active;
+})();
diff --git a/crates/trusted-server-core/src/integrations/mod.rs b/crates/trusted-server-core/src/integrations/mod.rs
@@ -17,6 +17,7 @@ pub mod datadome;
 pub mod didomi;
 pub mod google_tag_manager;
 pub mod gpt;
+pub mod gpt_diagnostics;
 pub mod lockr;
 pub mod nextjs;
 pub mod osano;
@@ -332,6 +333,10 @@ pub(crate) fn builders() -> &'static [IntegrationBuilder] {
             id: "gpt",
             build: gpt::register,
         },
+        IntegrationBuilder {
+            id: "gpt_diagnostics",
+            build: gpt_diagnostics::register,
+        },
     ]
 }