From 3e4d51c9f28d4c38592f43f666e3676c9d500daa Mon Sep 17 00:00:00 2001
From: Shantur Rathore <i@shantur.com>
Date: Thu, 25 Dec 2025 20:44:21 +0000
Subject: [PATCH] Surface runtime output in launch errors

---
 packages/server/src/workspaces/manager.ts |  6 ++--
 packages/server/src/workspaces/runtime.ts | 36 +++++++++++++++++++----
 2 files changed, 35 insertions(+), 7 deletions(-)

diff --git a/packages/server/src/workspaces/manager.ts b/packages/server/src/workspaces/manager.ts
index d2757bfa..cc76e9d8 100644
--- a/packages/server/src/workspaces/manager.ts
+++ b/packages/server/src/workspaces/manager.ts
@@ -306,9 +306,11 @@ export class WorkspaceManager {
     }
 
     const latestOutput = params.getLastOutput().trim()
-    const outputDetails = latestOutput ? ` Last output: ${latestOutput}` : ""
+    if (latestOutput) {
+      throw new Error(latestOutput)
+    }
     const reason = probeResult.reason ?? "Health check failed"
-    throw new Error(`Workspace ${params.workspaceId} failed health check: ${reason}.${outputDetails}`)
+    throw new Error(`Workspace ${params.workspaceId} failed health check: ${reason}.`)
   }
 
   private async probeInstance(workspaceId: string, port: number): Promise<{ ok: boolean; reason?: string }> {
diff --git a/packages/server/src/workspaces/runtime.ts b/packages/server/src/workspaces/runtime.ts
index c18b934e..ce6794d3 100644
--- a/packages/server/src/workspaces/runtime.ts
+++ b/packages/server/src/workspaces/runtime.ts
@@ -40,7 +40,23 @@ export class WorkspaceRuntime {
     const exitPromise = new Promise<ProcessExitInfo>((resolveExit) => {
       exitResolve = resolveExit
     })
-    let lastOutput = ""
+
+    // Store recent output for debugging - keep last 50 lines from each stream
+    const MAX_OUTPUT_LINES = 50
+    const recentStdout: string[] = []
+    const recentStderr: string[] = []
+    const getLastOutput = () => {
+      const combined: string[] = []
+      if (recentStderr.length > 0) {
+        combined.push("Error Stream")
+        combined.push(...recentStderr.slice(-10))
+      }
+      if (recentStdout.length > 0) {
+        combined.push("Output Stream")
+        combined.push(...recentStdout.slice(-10))
+      }
+      return combined.join("\n")
+    }
 
     return new Promise((resolve, reject) => {
       const commandLine = [options.binaryPath, ...args].join(" ")
@@ -108,7 +124,8 @@ export class WorkspaceRuntime {
           exitResolve = null
         }
         if (!portFound) {
-          const reason = stderrBuffer || `Process exited with code ${code}`
+          const recentOutput = getLastOutput().trim()
+          const reason = recentOutput || stderrBuffer || `Process exited with code ${code}`
           reject(new Error(reason))
         } else {
           options.onExit?.(exitInfo)
@@ -139,7 +156,12 @@ export class WorkspaceRuntime {
         for (const line of lines) {
           const trimmed = line.trim()
           if (!trimmed) continue
-          lastOutput = trimmed
+
+          recentStdout.push(trimmed)
+          if (recentStdout.length > MAX_OUTPUT_LINES) {
+            recentStdout.shift()
+          }
+
           this.emitLog(options.workspaceId, "info", line)
 
           if (!portFound) {
@@ -150,7 +172,6 @@ export class WorkspaceRuntime {
               child.removeListener("error", handleError)
               const port = parseInt(portMatch[1], 10)
               this.logger.info({ workspaceId: options.workspaceId, port }, "Workspace runtime allocated port")
-              const getLastOutput = () => lastOutput.trim()
               resolve({ pid: child.pid!, port, exitPromise, getLastOutput })
             }
           }
@@ -166,7 +187,12 @@ export class WorkspaceRuntime {
         for (const line of lines) {
           const trimmed = line.trim()
           if (!trimmed) continue
-          lastOutput = `[stderr] ${trimmed}`
+
+          recentStderr.push(trimmed)
+          if (recentStderr.length > MAX_OUTPUT_LINES) {
+            recentStderr.shift()
+          }
+
           this.emitLog(options.workspaceId, "error", line)
         }
       })