diff --git a/.agents/implementation/2026-04-16/worker-script-redirect-params/implementation.md b/.agents/implementation/2026-04-16/worker-script-redirect-params/implementation.md
new file mode 100644
index 00000000..72b8810d
--- /dev/null
+++ b/.agents/implementation/2026-04-16/worker-script-redirect-params/implementation.md
@@ -0,0 +1,29 @@
+# Fix: Worker Script Redirect Query Parameter Merging
+
+## Problem
+
+When `redirect: "manual"` was added to the Cloudflare worker script (to properly handle redirects without auto-following), the redirect handling code unconditionally overwrote the redirect Location's query string with the original request's query string:
+
+```js
+if (url.search) {
+    target.search = url.search;
+}
+```
+
+This caused any query parameters added by the upstream (e.g., OAuth `code`/`state` params on `/callback?code=abc&state=xyz`) to be lost and replaced by the original request's params.
+
+## Root Cause
+
+With the old `fetch(request, {})` (default `redirect: "follow"`), the browser/runtime followed redirects automatically, so most redirects never reached the redirect-handling code. After switching to `redirect: "manual"`, all redirect responses are intercepted, and the blanket overwrite of `target.search` now destroys upstream-added query parameters.
+
+## Fix
+
+Changed `pkg/clouds/pulumi/cloudflare/registrar.go` (the worker script template) to **merge** query parameters instead of overwriting:
+
+- Parse both the original request's params and the redirect target's params using `URLSearchParams`
+- Iterate over original params and only append those not already present in the redirect's URL
+- Redirect params take precedence over original request params
+
+## Files Changed
+
+- `pkg/clouds/pulumi/cloudflare/registrar.go` — lines 252-263 (worker script template)
diff --git a/pkg/clouds/pulumi/cloudflare/registrar.go b/pkg/clouds/pulumi/cloudflare/registrar.go
index 3e257675..94c6af12 100644
--- a/pkg/clouds/pulumi/cloudflare/registrar.go
+++ b/pkg/clouds/pulumi/cloudflare/registrar.go
@@ -249,9 +249,17 @@ async function handleRequest(origRequest) {
 		if (location) {
 			const target = new URL(location, url);
 
-			// re-append original query string
+			// merge original query string with redirect's own query params
+			// redirect params take precedence over original request params
 			if (url.search) {
-				target.search = url.search;
+				const origParams = new URLSearchParams(url.search);
+				const targetParams = new URLSearchParams(target.search);
+				for (const [key, value] of origParams) {
+					if (!targetParams.has(key)) {
+						targetParams.append(key, value);
+					}
+				}
+				target.search = targetParams.toString();
 			}
 
 			// Only rewrite hostname if redirect is to our target upstream (overrideHost)