diff --git a/apps/code/src/main/services/agent/service.ts b/apps/code/src/main/services/agent/service.ts
index ba8228961..b03024eb5 100644
--- a/apps/code/src/main/services/agent/service.ts
+++ b/apps/code/src/main/services/agent/service.ts
@@ -709,14 +709,17 @@ When creating pull requests, add the following footer at the end of the PR descr
       let configOptions: SessionConfigOption[] | undefined;
       let agentSessionId: string;
 
+      // Claude-specific: hydrate session JSONL from PostHog before resuming.
+      // If hydration finds no conversation to restore, skip the resume and
+      // fall through to creating a new session. This avoids a doomed
+      // unstable_resumeSession that would fail with "Resource not found"
       if (isReconnect && config.sessionId) {
         const existingSessionId = config.sessionId;
 
-        // Claude-specific: hydrate session JSONL from PostHog before resuming
         if (adapter !== "codex") {
           const posthogAPI = agent.getPosthogAPI();
           if (posthogAPI) {
-            await hydrateSessionJsonl({
+            const hasSession = await hydrateSessionJsonl({
               sessionId: existingSessionId,
               cwd: repoPath,
               taskId,
@@ -725,8 +728,19 @@ When creating pull requests, add the following footer at the end of the PR descr
               posthogAPI,
               log,
             });
+            if (!hasSession) {
+              log.info(
+                "No session JSONL to resume, creating new session instead",
+                { taskId, taskRunId },
+              );
+              config.sessionId = undefined;
+            }
           }
         }
+      }
+
+      if (isReconnect && config.sessionId) {
+        const existingSessionId = config.sessionId;
 
         // Both adapters implement unstable_resumeSession:
         // - Claude: delegates to SDK's resumeSession with JSONL hydration
diff --git a/packages/agent/src/adapters/claude/session/jsonl-hydration.ts b/packages/agent/src/adapters/claude/session/jsonl-hydration.ts
index 96fb66ec4..1805870a4 100644
--- a/packages/agent/src/adapters/claude/session/jsonl-hydration.ts
+++ b/packages/agent/src/adapters/claude/session/jsonl-hydration.ts
@@ -496,7 +496,7 @@ export async function hydrateSessionJsonl(params: {
   permissionMode?: string;
   posthogAPI: PostHogAPIClient;
   log: HydrationLog;
-}): Promise<void> {
+}): Promise<boolean> {
   const { posthogAPI, log } = params;
 
   try {
@@ -506,7 +506,7 @@ export async function hydrateSessionJsonl(params: {
       log.info("Local JSONL exists, skipping S3 hydration", {
         sessionId: params.sessionId,
       });
-      return;
+      return true;
     } catch {
       // File doesn't exist, proceed with hydration
     }
@@ -514,13 +514,13 @@ export async function hydrateSessionJsonl(params: {
     const taskRun = await posthogAPI.getTaskRun(params.taskId, params.runId);
     if (!taskRun.log_url) {
       log.info("No log URL, skipping JSONL hydration");
-      return;
+      return false;
     }
 
     const entries = await posthogAPI.fetchTaskRunLogs(taskRun);
     if (entries.length === 0) {
       log.info("No S3 log entries, skipping JSONL hydration");
-      return;
+      return false;
     }
 
     const entryCounts: Record<string, number> = {};
@@ -545,7 +545,7 @@ export async function hydrateSessionJsonl(params: {
     const allTurns = rebuildConversation(entries);
     if (allTurns.length === 0) {
       log.info("No conversation in S3 logs, skipping JSONL hydration");
-      return;
+      return false;
     }
 
     const maxTokens = supports1MContext(params.model ?? "")
@@ -577,10 +577,12 @@ export async function hydrateSessionJsonl(params: {
       turns: conversation.length,
       lines: jsonlLines.length,
     });
+    return true;
   } catch (err) {
     log.warn("Failed to hydrate session JSONL, continuing", {
       sessionId: params.sessionId,
       error: err instanceof Error ? err.message : String(err),
     });
+    return false;
   }
 }