diff --git a/test/helpers/coding-cli/real-session-contract-harness.ts b/test/helpers/coding-cli/real-session-contract-harness.ts
index cd0def13..eae6a59b 100644
--- a/test/helpers/coding-cli/real-session-contract-harness.ts
+++ b/test/helpers/coding-cli/real-session-contract-harness.ts
@@ -822,6 +822,54 @@ export async function startCodexAppServer(
   }
 }
 
+export async function startOpencodeServe(
+  workspace: ProbeWorkspace,
+  opencodePath: string,
+  runEnv: NodeJS.ProcessEnv,
+  healthPath: string,
+): Promise<{
+  baseUrl: string
+  port: number
+  process: TrackedProcess
+  health: unknown
+}> {
+  const endpoint = await allocateLocalhostPort()
+  const baseUrl = `http://${endpoint.hostname}:${endpoint.port}`
+  const processHandle = await workspace.spawnProcess(
+    opencodePath,
+    ['serve', '--hostname', endpoint.hostname, '--port', String(endpoint.port)],
+    {
+      env: runEnv,
+    },
+  )
+
+  // Fail fast (with the serve process's own error) if it cannot bind the port,
+  // rather than silently attaching to a stranger already listening on it or
+  // waiting out the full health-check timeout.
+  const health = await waitFor(`OpenCode serve ${baseUrl}`, async () => {
+    const stderr = processHandle.stderr()
+    if (/ServeError|Failed to start server|EADDRINUSE/i.test(stderr)) {
+      throw new Error(`OpenCode serve could not start on ${baseUrl}: ${stderr.trim()}`)
+    }
+    try {
+      const response = await fetchWithTimeout(`${baseUrl}${healthPath}`)
+      if (!response.ok) {
+        return undefined
+      }
+      return await response.json()
+    } catch {
+      return undefined
+    }
+  }, 30_000, 200)
+
+  return {
+    baseUrl,
+    port: endpoint.port,
+    process: processHandle,
+    health,
+  }
+}
+
 export class CodexRpcProbeClient {
   private readonly socket: WebSocket
   private readonly pendingRequests = new Map<number, PendingRpcRequest>()
diff --git a/test/integration/real/coding-cli-session-contract.test.ts b/test/integration/real/coding-cli-session-contract.test.ts
index ca8ec9ea..a3adea83 100644
--- a/test/integration/real/coding-cli-session-contract.test.ts
+++ b/test/integration/real/coding-cli-session-contract.test.ts
@@ -22,11 +22,11 @@ import {
   seedCodexHome,
   seedOpencodeHomes,
   startCodexAppServer,
+  startOpencodeServe,
   waitForCodexSessionArtifact,
   waitForCodexShellSnapshot,
   waitForFileSizeIncrease,
   waitForAnyHttpBusyStatus,
-  waitForHttpHealthy,
   waitForJsonResponse,
   waitForJsonLine,
   waitForOpencodeDbSession,
@@ -528,18 +528,14 @@ describe.sequential('coding cli real provider session contract', () => {
           const firstDbRow = await waitForOpencodeDbSession(homes.dbPath, firstSessionId)
           expect(firstDbRow.id).toBe(firstSessionId)
 
-          const servePort = 46123
-        const serve = await workspace.spawnProcess(
-          opencodePath,
-            ['serve', '--hostname', '127.0.0.1', '--port', String(servePort)],
-            {
-              env: runEnv,
-            },
+          const { baseUrl, process: serve, health } = await startOpencodeServe(
+            workspace,
+            opencodePath,
+            runEnv,
+            note.providers.opencode.globalHealthPath,
           )
 
-          const healthUrl = `http://127.0.0.1:${servePort}${note.providers.opencode.globalHealthPath}`
-          const statusUrl = `http://127.0.0.1:${servePort}${note.providers.opencode.sessionStatusPath}`
-          const health = await waitForHttpHealthy(healthUrl)
+          const statusUrl = `${baseUrl}${note.providers.opencode.sessionStatusPath}`
           expect(health).toEqual({
             healthy: true,
             version: opencodeBinary.version,
@@ -555,7 +551,7 @@ describe.sequential('coding cli real provider session contract', () => {
               'json',
               '--dangerously-skip-permissions',
               '--attach',
-              `http://127.0.0.1:${servePort}`,
+              baseUrl,
             ],
             {
               env: runEnv,
diff --git a/test/unit/client/components/TerminalView.osc52.test.tsx b/test/unit/client/components/TerminalView.osc52.test.tsx
index aeb1b5c6..5e89300b 100644
--- a/test/unit/client/components/TerminalView.osc52.test.tsx
+++ b/test/unit/client/components/TerminalView.osc52.test.tsx
@@ -281,7 +281,7 @@ describe('TerminalView OSC52 policy handling', () => {
     messageHandler!({ type: 'terminal.output', terminalId, seqStart: 1, seqEnd: 1, data: `before${OSC52_COPY}after` })
 
     await waitFor(() => {
-      expect(terminalInstances[0].write).toHaveBeenCalledWith('beforeafter', undefined)
+      expect(terminalInstances[0].write.mock.calls.some((call) => call[0] === 'beforeafter')).toBe(true)
     })
     expect(clipboardMocks.copyText).toHaveBeenCalledWith('copy')
     expect(screen.queryByRole('dialog', { name: 'Clipboard access request' })).not.toBeInTheDocument()
@@ -398,7 +398,7 @@ describe('TerminalView OSC52 policy handling', () => {
     messageHandler!({ type: 'terminal.output', terminalId, seqStart: 1, seqEnd: 1, data: `before${OSC52_COPY}after` })
 
     await waitFor(() => {
-      expect(terminalInstances[0].write).toHaveBeenCalledWith('beforeafter', undefined)
+      expect(terminalInstances[0].write.mock.calls.some((call) => call[0] === 'beforeafter')).toBe(true)
     })
     expect(clipboardMocks.copyText).not.toHaveBeenCalled()
     expect(screen.queryByRole('dialog', { name: 'Clipboard access request' })).not.toBeInTheDocument()
diff --git a/test/unit/client/components/TerminalView.renderer.test.tsx b/test/unit/client/components/TerminalView.renderer.test.tsx
index 182bc09c..ce26f637 100644
--- a/test/unit/client/components/TerminalView.renderer.test.tsx
+++ b/test/unit/client/components/TerminalView.renderer.test.tsx
@@ -363,7 +363,7 @@ describe('TerminalView renderer mode', () => {
       data: 'still works',
     })
     await waitFor(() => {
-      expect(terminalInstances[0].write).toHaveBeenCalledWith('still works', undefined)
+      expect(terminalInstances[0].write.mock.calls.some((call) => call[0] === 'still works')).toBe(true)
     })
   })
 })