Fix Codex resume failure due to improper --last usage

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Project	Deployment	Preview	Comments	Updated (UTC)
coding-agent-platform	Ready	Preview	Comment	Oct 25, 2025 5:57pm

[vercel]

The codex resume command is missing the session identifier or --last flag, which means the CLI won't know which session to resume. This breaks session resumption for continued conversations.

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📝 Patch Details

diff --git a/lib/sandbox/agents/codex.ts b/lib/sandbox/agents/codex.ts
index 8e3d93e..37a1823 100644
--- a/lib/sandbox/agents/codex.ts
+++ b/lib/sandbox/agents/codex.ts
@@ -283,10 +283,18 @@ url = "${server.baseUrl}"
 
     if (isResumed) {
       // Use resume command instead of exec
-      // Note: codex resume takes the prompt directly without --last flag when continuing
-      codexCommand = 'codex resume'
-      if (logger) {
-        await logger.info('Resuming previous Codex conversation')
+      if (sessionId) {
+        // Resume specific session by ID
+        codexCommand = `codex resume ${sessionId}`
+        if (logger) {
+          await logger.info('Resuming specific Codex chat session')
+        }
+      } else {
+        // Resume most recent session if no specific sessionId provided
+        codexCommand = 'codex resume --last'
+        if (logger) {
+          await logger.info('Resuming previous Codex conversation')
+        }
       }
     }
 

Analysis

Missing session identifier in codex resume command

What fails: The executeCodexInSandbox() function in lib/sandbox/agents/codex.ts (lines 283-297) builds a codex resume command that doesn't specify which session to resume when continuing a conversation in a kept-alive sandbox.

How to reproduce:

1. Call executeCodexInSandbox() with isResumed=true and a valid sessionId parameter
2. The generated command will be codex resume (no session identifier)
3. In a non-interactive sandbox, this fails because codex resume with no arguments opens an interactive picker

Result: The Codex CLI fails to resume the session. According to Codex documentation:

• codex resume = opens interactive picker (fails in non-interactive sandbox)
• codex resume --last = resumes most recent session
• codex resume <SESSION_ID> = resumes specific session by ID

The sessionId parameter is passed to the function (line 35) and available, but was never used after commit 5d8487e removed the --last flag without adding sessionId support.

Expected:

• When sessionId is provided: use codex resume <sessionId>
• When sessionId is not provided: fall back to codex resume --last

This follows the pattern used by other agents (Claude, Cursor, Copilot) that also handle session resumption.