From e89527c9f0eba6c7aa866f3ba39ce9f6809023a7 Mon Sep 17 00:00:00 2001
From: Kevin Flansburg <kevin.flansburg@gmail.com>
Date: Thu, 2 Apr 2026 21:09:53 -0600
Subject: [PATCH] feat: Send x-session-affinity and x-parent-session-id headers
 (#20744)

---
 packages/opencode/src/session/llm.ts    | 3 +++
 packages/opencode/src/session/prompt.ts | 1 +
 2 files changed, 4 insertions(+)

diff --git a/packages/opencode/src/session/llm.ts b/packages/opencode/src/session/llm.ts
index dc89db409e..1813346cdc 100644
--- a/packages/opencode/src/session/llm.ts
+++ b/packages/opencode/src/session/llm.ts
@@ -25,6 +25,7 @@ export namespace LLM {
   export type StreamInput = {
     user: MessageV2.User
     sessionID: string
+    parentSessionID?: string
     model: Provider.Model
     agent: Agent.Info
     permission?: Permission.Ruleset
@@ -301,6 +302,8 @@ export namespace LLM {
               "x-opencode-client": Flag.OPENCODE_CLIENT,
             }
           : {
+              "x-session-affinity": input.sessionID,
+              ...(input.parentSessionID ? { "x-parent-session-id": input.parentSessionID } : {}),
               "User-Agent": `opencode/${Installation.VERSION}`,
             }),
         ...input.model.headers,
diff --git a/packages/opencode/src/session/prompt.ts b/packages/opencode/src/session/prompt.ts
index 8facf7aba7..e4709ef47e 100644
--- a/packages/opencode/src/session/prompt.ts
+++ b/packages/opencode/src/session/prompt.ts
@@ -1512,6 +1512,7 @@ NOTE: At any point in time through this workflow you should feel free to ask the
                   agent,
                   permission: session.permission,
                   sessionID,
+                  parentSessionID: session.parentID,
                   system,
                   messages: [...modelMsgs, ...(isLastStep ? [{ role: "assistant" as const, content: MAX_STEPS }] : [])],
                   tools,