From 6272c8006778e16e0964d87c71d80440a9a2aa20 Mon Sep 17 00:00:00 2001
From: Jeff Verkoeyen <jeff@clutch.engineering>
Date: Tue, 10 Feb 2026 02:28:31 -0500
Subject: [PATCH] feat: send x-session-id and x-parent-session-id headers in
 LLM API requests

Forward opencode session identifiers as HTTP headers on all outgoing LLM
API requests. This enables OpenAI-compatible servers to correlate requests
belonging to the same session and reconstruct parent/child agent trees
(e.g. when the task tool spawns sub-agents).

Two new headers are sent:
- x-session-id: always present, identifies the current session
- x-parent-session-id: present only for sub-agent sessions, identifies
  the parent session that spawned this one

This is a minimal, non-breaking change:
- parentSessionID is optional on StreamInput
- Existing callers (summary, title) that don't pass it simply omit the
  parent header
- Headers are additive and ignored by providers that don't use them

Closes anomalyco/opencode#12930
---
 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 4be6e2538f7..dcfdca97d7a 100644
--- a/packages/opencode/src/session/llm.ts
+++ b/packages/opencode/src/session/llm.ts
@@ -31,6 +31,7 @@ export namespace LLM {
   export type StreamInput = {
     user: MessageV2.User
     sessionID: string
+    parentSessionID?: string
     model: Provider.Model
     agent: Agent.Info
     system: string[]
@@ -228,6 +229,8 @@ export namespace LLM {
                 "User-Agent": `opencode/${Installation.VERSION}`,
               }
             : undefined),
+        "x-session-id": input.sessionID,
+        ...(input.parentSessionID ? { "x-parent-session-id": input.parentSessionID } : undefined),
         ...input.model.headers,
         ...headers,
       },
diff --git a/packages/opencode/src/session/prompt.ts b/packages/opencode/src/session/prompt.ts
index d7f73b4f609..9b5f6eb1e44 100644
--- a/packages/opencode/src/session/prompt.ts
+++ b/packages/opencode/src/session/prompt.ts
@@ -625,6 +625,7 @@ export namespace SessionPrompt {
         agent,
         abort,
         sessionID,
+        parentSessionID: session.parentID,
         system: [...(await SystemPrompt.environment(model)), ...(await InstructionPrompt.system())],
         messages: [
           ...MessageV2.toModelMessages(sessionMessages, model),