From c6d43a1a251d27d739b415505ec772d5b15b1d66 Mon Sep 17 00:00:00 2001
From: Charles Packer <packercharles@gmail.com>
Date: Thu, 15 Jan 2026 19:18:37 -0800
Subject: [PATCH] fix: auto-create missing skills blocks when resuming older
 agents (#559)

Co-authored-by: Letta <noreply@letta.com>
---
 src/agent/memory.ts | 63 +++++++++++++++++++++++++++++++++++++++++++++
 src/headless.ts     |  8 +++++-
 src/index.ts        |  8 +++++-
 3 files changed, 77 insertions(+), 2 deletions(-)

diff --git a/src/agent/memory.ts b/src/agent/memory.ts
index 56dbe3f..f469f18 100644
--- a/src/agent/memory.ts
+++ b/src/agent/memory.ts
@@ -144,3 +144,66 @@ export async function getDefaultMemoryBlocks(): Promise<CreateBlock[]> {
   }
   return cachedMemoryBlocks;
 }
+
+/**
+ * Ensure an agent has the required skills blocks (skills, loaded_skills).
+ * If missing, creates them with default values and attaches to the agent.
+ * This is needed for backwards compatibility with agents created before skills were added.
+ *
+ * @param agentId - The agent ID to check/update
+ * @returns Array of block labels that were created (empty if all existed)
+ */
+export async function ensureSkillsBlocks(agentId: string): Promise<string[]> {
+  const { getClient } = await import("./client");
+  const client = await getClient();
+
+  // Get current blocks on the agent
+  // Response may be paginated or an array depending on SDK version
+  const blocksResponse = await client.agents.blocks.list(agentId);
+  const blocks = Array.isArray(blocksResponse)
+    ? blocksResponse
+    : (blocksResponse as { items?: Array<{ label?: string }> }).items || [];
+  const existingLabels = new Set(blocks.map((b) => b.label));
+
+  const createdLabels: string[] = [];
+
+  // Check each required skills block
+  for (const label of ISOLATED_BLOCK_LABELS) {
+    if (existingLabels.has(label)) {
+      continue;
+    }
+
+    // Load the default block definition from .mdx
+    const content = MEMORY_PROMPTS[`${label}.mdx`];
+    if (!content) {
+      console.warn(`Missing embedded prompt file for ${label}.mdx`);
+      continue;
+    }
+
+    const { frontmatter, body } = parseMdxFrontmatter(content);
+
+    const blockData: CreateBlock = {
+      label,
+      value: body,
+      read_only: true, // Skills blocks are read-only (managed by Skill tool)
+    };
+
+    if (frontmatter.description) {
+      blockData.description = frontmatter.description;
+    }
+
+    if (frontmatter.limit) {
+      const limit = parseInt(frontmatter.limit, 10);
+      if (!Number.isNaN(limit) && limit > 0) {
+        blockData.limit = limit;
+      }
+    }
+
+    // Create the block and attach to agent
+    const createdBlock = await client.blocks.create(blockData);
+    await client.agents.blocks.attach(createdBlock.id, { agent_id: agentId });
+    createdLabels.push(label);
+  }
+
+  return createdLabels;
+}
diff --git a/src/headless.ts b/src/headless.ts
index 937aa45..a2f06bd 100644
--- a/src/headless.ts
+++ b/src/headless.ts
@@ -16,7 +16,7 @@ import {
 import { getClient } from "./agent/client";
 import { initializeLoadedSkillsFlag, setAgentContext } from "./agent/context";
 import { createAgent } from "./agent/create";
-import { ISOLATED_BLOCK_LABELS } from "./agent/memory";
+import { ensureSkillsBlocks, ISOLATED_BLOCK_LABELS } from "./agent/memory";
 import { sendMessageStream } from "./agent/message";
 import { getModelUpdateArgs } from "./agent/model";
 import { SessionStats } from "./agent/stats";
@@ -529,6 +529,12 @@ export async function handleHeadlessCommand(
     conversationId,
   });
 
+  // Ensure the agent has the required skills blocks (for backwards compatibility)
+  const createdBlocks = await ensureSkillsBlocks(agent.id);
+  if (createdBlocks.length > 0) {
+    console.log("Created missing skills blocks for agent compatibility");
+  }
+
   // Set agent context for tools that need it (e.g., Skill tool, Task tool)
   setAgentContext(agent.id, skillsDirectory);
   await initializeLoadedSkillsFlag();
diff --git a/src/index.ts b/src/index.ts
index 3f350a9..63a5ef8 100755
--- a/src/index.ts
+++ b/src/index.ts
@@ -7,7 +7,7 @@ import { getResumeData, type ResumeData } from "./agent/check-approval";
 import { getClient } from "./agent/client";
 import { initializeLoadedSkillsFlag, setAgentContext } from "./agent/context";
 import type { AgentProvenance } from "./agent/create";
-import { ISOLATED_BLOCK_LABELS } from "./agent/memory";
+import { ensureSkillsBlocks, ISOLATED_BLOCK_LABELS } from "./agent/memory";
 import { LETTA_CLOUD_API_URL } from "./auth/oauth";
 import { ConversationSelector } from "./cli/components/ConversationSelector";
 import type { ApprovalRequest } from "./cli/helpers/stream";
@@ -1227,6 +1227,12 @@ async function main(): Promise<void> {
         settingsManager.updateLocalProjectSettings({ lastAgent: agent.id });
         settingsManager.updateSettings({ lastAgent: agent.id });
 
+        // Ensure the agent has the required skills blocks (for backwards compatibility)
+        const createdBlocks = await ensureSkillsBlocks(agent.id);
+        if (createdBlocks.length > 0) {
+          console.log("Created missing skills blocks for agent compatibility");
+        }
+
         // Set agent context for tools that need it (e.g., Skill tool)
         setAgentContext(agent.id, skillsDirectory);
         await initializeLoadedSkillsFlag();