feat(athena): add prepare_council_prompt tool for faster council launches

Athena saves the analysis prompt to a temp file once, then launches each
council member with a short "Read <path> for your instructions" prompt.
This eliminates repeated prompt text across N task calls while preserving
individual clickable task panes in the TUI.

src/agents/AGENTS.md

@@ -35,7 +35,7 @@ Agent factories following `createXXXAgent(model) → AgentConfig` pattern. Each
 | Atlas | task, call_omo_agent |
 | Momus | write, edit, task |
 | Athena | write, edit, call_omo_agent |
-| Council-Member | write, edit, task, call_omo_agent, switch_agent, background_wait |
+| Council-Member | write, edit, task, call_omo_agent, switch_agent, background_wait, prepare_council_prompt |
 
 ## STRUCTURE
 

src/agents/athena/agent.ts

@@ -73,14 +73,17 @@ Step 2: Resolve the selected member list:
 - If user selected "All Members", resolve to every member from your available council members listed below.
 - Otherwise resolve to the explicitly selected member labels.
 
-Step 3: Launch each selected member via the task tool with run_in_background=true:
-- For each selected member, call the task tool with:
+Step 3: Save the prompt, then launch members with short references:
+
+Step 3a: Call prepare_council_prompt with the user's original question as the prompt parameter. This saves it to a temp file and returns the file path.
+
+Step 3b: For each selected member, call the task tool with:
   - subagent_type: the exact member name from your available council members listed below (e.g., "Council: Claude Opus 4.6")
   - run_in_background: true
-  - prompt: the user's original question
+  - prompt: "Read <path> for your instructions." (where <path> is the file path from Step 3a)
   - load_skills: []
   - description: the member name (e.g., "Council: Claude Opus 4.6")
-- Launch ALL selected members FIRST (one task call per member, all in parallel) before collecting any results.
+- Launch ALL selected members before collecting any results.
 - Track every returned task_id and member mapping.
 - IMPORTANT: Use EXACTLY the subagent_type names listed in your available council members below — they must match precisely.
 

src/agents/athena/council-member-agent.ts

@@ -32,6 +32,7 @@ export function createCouncilMemberAgent(model: string): AgentConfig {
     "call_omo_agent",
     "switch_agent",
     "background_wait",
+    "prepare_council_prompt",
   ])
 
   const base = {

src/plugin-handlers/tool-config-handler.ts

@@ -26,6 +26,7 @@ export function applyToolConfig(params: {
     LspCodeActionResolve: false,
     "task_*": false,
     teammate: false,
+    prepare_council_prompt: false,
     ...(params.pluginConfig.experimental?.task_system
       ? { todowrite: false, todoread: false }
       : {}),
@@ -106,6 +107,7 @@ export function applyToolConfig(params: {
     athena.permission = {
       ...athena.permission,
       task: "allow",
+      prepare_council_prompt: "allow",
       question: questionPermission,
     };
   }

src/plugin/tool-registry.ts

@@ -26,6 +26,7 @@ import {
   createTaskList,
   createTaskUpdateTool,
   createHashlineEditTool,
+  createPrepareCouncilPromptTool,
 } from "../tools"
 import { getMainSessionID } from "../features/claude-code-session-state"
 import { filterDisabledTools } from "../shared/disabled-tools"
@@ -138,6 +139,7 @@ export function createToolRegistry(args: {
     interactive_bash,
     ...taskToolsRecord,
     ...hashlineToolsRecord,
+    prepare_council_prompt: createPrepareCouncilPromptTool(),
   }
 
   const filteredTools = filterDisabledTools(allTools, pluginConfig.disabled_tools)

src/shared/agent-tool-restrictions.ts

@@ -63,6 +63,7 @@ const AGENT_RESTRICTIONS: Record<string, Record<string, boolean>> = {
     call_omo_agent: false,
     switch_agent: false,
     background_wait: false,
+    prepare_council_prompt: false,
   },
 }
 

src/tools/index.ts

@@ -46,6 +46,7 @@ export {
   createTaskUpdateTool,
 } from "./task"
 export { createHashlineEditTool } from "./hashline-edit"
+export { createPrepareCouncilPromptTool } from "./prepare-council-prompt"
 
 export function createBackgroundTools(manager: BackgroundManager, client: OpencodeClient): Record<string, ToolDefinition> {
   const outputManager: BackgroundOutputManager = manager

src/tools/prepare-council-prompt/index.ts

@@ -0,0 +1 @@
+export { createPrepareCouncilPromptTool } from "./tools"

src/tools/prepare-council-prompt/tools.ts

@@ -0,0 +1,47 @@
+import { tool, type ToolDefinition } from "@opencode-ai/plugin"
+import { writeFile, unlink } from "node:fs/promises"
+import { join } from "node:path"
+import { tmpdir } from "node:os"
+import { log } from "../../shared/logger"
+
+const CLEANUP_DELAY_MS = 30 * 60 * 1000
+
+export function createPrepareCouncilPromptTool(): ToolDefinition {
+  const description = `Save a council analysis prompt to a temp file so council members can read it.
+
+Athena-only tool. Saves the prompt once, then each council member task() call uses a short
+"Read <path>" instruction instead of repeating the full question. This keeps task() calls
+fast and small.
+
+Returns the file path to reference in subsequent task() calls.`
+
+  return tool({
+    description,
+    args: {
+      prompt: tool.schema.string().describe("The full analysis prompt/question for council members"),
+    },
+    async execute(args: { prompt: string }) {
+      if (!args.prompt?.trim()) {
+        return "Prompt cannot be empty."
+      }
+
+      const filename = `athena-council-${crypto.randomUUID().slice(0, 8)}.md`
+      const filePath = join(tmpdir(), filename)
+
+      await writeFile(filePath, args.prompt, "utf-8")
+
+      setTimeout(() => {
+        unlink(filePath).catch(() => {})
+      }, CLEANUP_DELAY_MS)
+
+      log("[prepare-council-prompt] Saved prompt", { filePath, length: args.prompt.length })
+
+      return `Council prompt saved to: ${filePath}
+
+Use this path in each council member's task() call:
+- prompt: "Read ${filePath} for your instructions."
+
+The file auto-deletes after 30 minutes.`
+    },
+  })
+}