Fix Issue #1428: Deny bash permission for Prometheus agent

- Change PROMETHEUS_PERMISSION bash from 'allow' to 'deny' to prevent unrestricted bash execution
- Prometheus is a read-only planner and should not execute bash commands
- The prometheus-md-only hook provides additional blocking as backup

src/features/background-agent/spawner/background-session-creator.ts

@@ -0,0 +1,46 @@
+import type { OpencodeClient } from "../constants"
+import type { ConcurrencyManager } from "../concurrency"
+import type { LaunchInput } from "../types"
+import { log } from "../../../shared"
+
+export async function createBackgroundSession(options: {
+  client: OpencodeClient
+  input: LaunchInput
+  parentDirectory: string
+  concurrencyManager: ConcurrencyManager
+  concurrencyKey: string
+}): Promise<string> {
+  const { client, input, parentDirectory, concurrencyManager, concurrencyKey } = options
+
+  const body = {
+    parentID: input.parentSessionID,
+    title: `Background: ${input.description}`,
+    permission: [{ permission: "question", action: "deny" as const, pattern: "*" }],
+  }
+
+  const createResult = await client.session
+    .create({
+      body,
+      query: {
+        directory: parentDirectory,
+      },
+    })
+    .catch((error) => {
+      concurrencyManager.release(concurrencyKey)
+      throw error
+    })
+
+  if (createResult.error) {
+    concurrencyManager.release(concurrencyKey)
+    throw new Error(`Failed to create background session: ${createResult.error}`)
+  }
+
+  if (!createResult.data?.id) {
+    concurrencyManager.release(concurrencyKey)
+    throw new Error("Failed to create background session: API returned no session ID")
+  }
+
+  const sessionID = createResult.data.id
+  log("[background-agent] Background session created", { sessionID })
+  return sessionID
+}

src/features/background-agent/spawner/concurrency-key-from-launch-input.ts

@@ -0,0 +1,7 @@
+import type { LaunchInput } from "../types"
+
+export function getConcurrencyKeyFromLaunchInput(input: LaunchInput): string {
+  return input.model
+    ? `${input.model.providerID}/${input.model.modelID}`
+    : input.agent
+}

src/features/background-agent/spawner/parent-directory-resolver.ts

@@ -0,0 +1,21 @@
+import type { OpencodeClient } from "../constants"
+import { log } from "../../../shared"
+
+export async function resolveParentDirectory(options: {
+  client: OpencodeClient
+  parentSessionID: string
+  defaultDirectory: string
+}): Promise<string> {
+  const { client, parentSessionID, defaultDirectory } = options
+
+  const parentSession = await client.session
+    .get({ path: { id: parentSessionID } })
+    .catch((error) => {
+      log(`[background-agent] Failed to get parent session: ${error}`)
+      return null
+    })
+
+  const parentDirectory = parentSession?.data?.directory ?? defaultDirectory
+  log(`[background-agent] Parent dir: ${parentSession?.data?.directory}, using: ${parentDirectory}`)
+  return parentDirectory
+}

src/features/background-agent/spawner/tmux-callback-invoker.ts

@@ -0,0 +1,39 @@
+import type { OnSubagentSessionCreated } from "../constants"
+import { TMUX_CALLBACK_DELAY_MS } from "../constants"
+import { log } from "../../../shared"
+import { isInsideTmux } from "../../../shared/tmux"
+
+export async function maybeInvokeTmuxCallback(options: {
+  onSubagentSessionCreated?: OnSubagentSessionCreated
+  tmuxEnabled: boolean
+  sessionID: string
+  parentID: string
+  title: string
+}): Promise<void> {
+  const { onSubagentSessionCreated, tmuxEnabled, sessionID, parentID, title } = options
+
+  log("[background-agent] tmux callback check", {
+    hasCallback: !!onSubagentSessionCreated,
+    tmuxEnabled,
+    isInsideTmux: isInsideTmux(),
+    sessionID,
+    parentID,
+  })
+
+  if (!onSubagentSessionCreated || !tmuxEnabled || !isInsideTmux()) {
+    log("[background-agent] SKIP tmux callback - conditions not met")
+    return
+  }
+
+  log("[background-agent] Invoking tmux callback NOW", { sessionID })
+  await onSubagentSessionCreated({
+    sessionID,
+    parentID,
+    title,
+  }).catch((error) => {
+    log("[background-agent] Failed to spawn tmux pane:", error)
+  })
+
+  log("[background-agent] tmux callback completed, waiting")
+  await new Promise<void>((resolve) => setTimeout(resolve, TMUX_CALLBACK_DELAY_MS))
+}