fix(executors): forward X-Session-ID/X-Title agent metadata headers (#7104)

* fix(executors): forward X-Session-ID/X-Title agent metadata headers (port from 9router#2413)

Custom agent clients (e.g. non-OpenCode providers) commonly send X-Session-ID and X-Title headers for upstream request tracking/attribution, but forwardOpencodeClientHeaders() only forwarded x-opencode-* keys plus User-Agent, silently dropping these for every client. Extends the existing case-insensitive allowlist forwarding path with x-session-id/x-title.

Reported-by: Atikur Rahman Chitholian (@chitholian) (https://github.com/decolua/9router/issues/2413)

* chore(changelog): move #2413 entry to changelog.d fragment

Consistency with the repo's canonical changelog.d/fixes/ workflow (avoids
merge-storm re-conflicts from editing CHANGELOG.md directly).

changelog.d/fixes/2413-preserve-agent-headers.md

@@ -0,0 +1 @@
+- **fix(executors):** forward agent-supplied `X-Session-ID`/`X-Title` metadata headers to upstream providers — previously dropped for every client outside the `x-opencode-*` allowlist. (thanks @chitholian) (#7104)

open-sse/utils/opencodeHeaders.ts

@@ -12,6 +12,15 @@ const OPENCODE_HEADER_KEYS = [
   "x-opencode-client",
 ] as const;
 
+/**
+ * Common agent-metadata headers used by non-OpenCode clients (custom agents/
+ * providers) for upstream request tracking and attribution. Forwarded the same
+ * way as the x-opencode-* set: case-insensitive lookup, client value wins.
+ * Added for 9router#2413 — these were previously dropped for every client
+ * outside the OpenCode allowlist.
+ */
+const AGENT_METADATA_HEADER_KEYS = ["x-session-id", "x-title"] as const;
+
 /**
  * Case-insensitive lookup for a header in a headers record.
  */
@@ -26,6 +35,8 @@ function findHeader(headers: Record<string, string>, name: string): string | und
  * 1. Forwards User-Agent from clientHeaders via `setUserAgentHeader()`
  * 2. Forwards x-opencode-session, x-opencode-request, x-opencode-project,
  *    x-opencode-client headers (case-insensitive match)
+ * 3. Forwards x-session-id, x-title agent-metadata headers (case-insensitive
+ *    match) — common conventions used by non-OpenCode agent clients (9router#2413)
  *
  * @param headers - The outbound headers record to mutate
  * @param clientHeaders - The client-provided headers to forward from
@@ -60,6 +71,14 @@ export function forwardOpencodeClientHeaders(
     }
   }
 
+  // 2b. Forward agent-metadata headers (x-session-id, x-title) — 9router#2413
+  for (const headerName of AGENT_METADATA_HEADER_KEYS) {
+    const value = findHeader(clientHeaders, headerName);
+    if (value) {
+      headers[headerName] = value;
+    }
+  }
+
   // 3. OpencodeExecutor-only: synthesize session/request id from fallback headers
   if (options?.synthesizeRequestId && !headers["x-opencode-session"]) {
     const sessionAffinity =

tests/unit/refactor-opencodeHeaders.test.ts

@@ -116,6 +116,43 @@ describe("forwardOpencodeClientHeaders – x-opencode-* headers", () => {
   });
 });
 
+// ── agent metadata headers (X-Session-ID / X-Title) — 9router#2413 ─────────
+// Non-OpenCode agent clients (e.g. custom providers) commonly send X-Session-ID
+// and X-Title for upstream request tracking/attribution. These were previously
+// dropped for every client outside the x-opencode-* allowlist.
+
+describe("forwardOpencodeClientHeaders – X-Session-ID / X-Title", () => {
+  it("forwards X-Session-ID from client headers", () => {
+    const headers = h();
+    const clientHeaders = { "X-Session-ID": "sess-xyz" };
+    forwardOpencodeClientHeaders(headers, clientHeaders);
+    assert.equal(headers["x-session-id"], "sess-xyz");
+  });
+
+  it("forwards X-Title from client headers", () => {
+    const headers = h();
+    const clientHeaders = { "X-Title": "My Agent" };
+    forwardOpencodeClientHeaders(headers, clientHeaders);
+    assert.equal(headers["x-title"], "My Agent");
+  });
+
+  it("matches X-Session-ID / X-Title case-insensitively", () => {
+    const headers = h();
+    const clientHeaders = { "x-session-id": "sess-lower", "x-title": "lower title" };
+    forwardOpencodeClientHeaders(headers, clientHeaders);
+    assert.equal(headers["x-session-id"], "sess-lower");
+    assert.equal(headers["x-title"], "lower title");
+  });
+
+  it("still does NOT forward unrelated unknown headers", () => {
+    const headers = h();
+    const clientHeaders = { "X-Session-ID": "sess-1", "X-Random-Other": "nope" };
+    forwardOpencodeClientHeaders(headers, clientHeaders);
+    assert.equal(headers["x-session-id"], "sess-1");
+    assert.equal(headers["X-Random-Other"], undefined);
+  });
+});
+
 // ── synthesizeRequestId ─────────────────────────────────────────────────────
 
 describe("forwardOpencodeClientHeaders – synthesizeRequestId", () => {