From 7d5a0316e806bc715e3763e9b7a739a84e5f0bfe Mon Sep 17 00:00:00 2001
From: Griffin Long <griffinwork40@gmail.com>
Date: Thu, 27 Aug 2026 21:58:28 -0400
Subject: [PATCH] fix(subagent): sanitize id_prefix to prevent assertSafeJobId
 rejection (#1319)

---
 src/agent/subagent/fork-resolution.test.ts | 31 ++++++++++++++++++++++
 src/agent/subagent/fork-resolution.ts      |  3 ++-
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/src/agent/subagent/fork-resolution.test.ts b/src/agent/subagent/fork-resolution.test.ts
index 8d4b84d5..c9e1a4ca 100644
--- a/src/agent/subagent/fork-resolution.test.ts
+++ b/src/agent/subagent/fork-resolution.test.ts
@@ -329,6 +329,37 @@ describe('id and resume', () => {
     expect(resolveForkInputs(args).id).toMatch(/^my-prefix-/);
   });
 
+  it('sanitizes idPrefix by replacing disallowed characters with hyphens (#1319)', () => {
+    // A model-supplied id_prefix containing dots, spaces, or other chars outside
+    // [A-Za-z0-9_-] would cause assertSafeJobId to throw in SubagentLogWriter.
+    // Verify they are replaced with '-' before the id is assembled.
+    const args = makeArgs({
+      options: {
+        parent: { sessionId: 'sid' },
+        config: { model: 'sonnet' },
+        agentType: 'a',
+        idPrefix: 'research.agent',
+      },
+      counter: 1,
+    });
+
+    expect(resolveForkInputs(args).id).toMatch(/^research-agent-/);
+  });
+
+  it('sanitizes idPrefix with spaces', () => {
+    const args = makeArgs({
+      options: {
+        parent: { sessionId: 'sid' },
+        config: { model: 'sonnet' },
+        agentType: 'a',
+        idPrefix: 'my agent',
+      },
+      counter: 1,
+    });
+
+    expect(resolveForkInputs(args).id).toMatch(/^my-agent-/);
+  });
+
   it('defaults to "subagent" when idPrefix is omitted', () => {
     const args = makeArgs({
       options: {
diff --git a/src/agent/subagent/fork-resolution.ts b/src/agent/subagent/fork-resolution.ts
index 0c6965ce..ed4b7ffb 100644
--- a/src/agent/subagent/fork-resolution.ts
+++ b/src/agent/subagent/fork-resolution.ts
@@ -92,7 +92,8 @@ export interface ForkResolved {
 export function resolveForkInputs(args: ResolveForkInputsArgs): ForkResolved {
   const { options, counter, managerHookRegistry, parentTraceWriter, parentModel } = args;
 
-  const id = `${options.idPrefix ?? 'subagent'}-${Date.now()}-${counter}`;
+  const safePrefix = (options.idPrefix ?? 'subagent').replace(/[^A-Za-z0-9_-]/g, '-');
+  const id = `${safePrefix}-${Date.now()}-${counter}`;
   const resume = options.parent.sessionId;
 
   const registry =