refactor(task): drop session_id resume alias

src/plugin/tool-execute-before.test.ts

@@ -143,7 +143,7 @@ describe("createToolExecuteBeforeHandler", () => {
       expect(output.args.subagent_type).toBe("sisyphus-junior")
     })
 
-    test("resolves subagent_type from session first message when session_id provided without subagent_type", async () => {
+    test("resolves subagent_type from session first message when task_id is provided without subagent_type", async () => {
       //#given
       const ctx = createCtxWithSessionMessages([
         { info: { role: "user" } },
@@ -152,7 +152,7 @@ describe("createToolExecuteBeforeHandler", () => {
       ])
       const handler = createToolExecuteBeforeHandler({ ctx, hooks: emptyHooks })
       const input = { tool: "task", sessionID: "ses_123", callID: "call_1" }
-      const output = { args: { session_id: "ses_abc123", description: "Continue task", prompt: "fix it" } as Record<string, unknown> }
+      const output = { args: { task_id: "ses_abc123", description: "Continue task", prompt: "fix it" } as Record<string, unknown> }
 
       //#when
       await handler(input, output)
@@ -186,7 +186,7 @@ describe("createToolExecuteBeforeHandler", () => {
       ])
       const handler = createToolExecuteBeforeHandler({ ctx, hooks: emptyHooks })
       const input = { tool: "task", sessionID: "ses_123", callID: "call_1" }
-      const output = { args: { session_id: "ses_abc123", description: "Continue task", prompt: "fix it" } as Record<string, unknown> }
+      const output = { args: { task_id: "ses_abc123", description: "Continue task", prompt: "fix it" } as Record<string, unknown> }
 
       //#when
       await handler(input, output)
@@ -195,12 +195,12 @@ describe("createToolExecuteBeforeHandler", () => {
       expect(output.args.subagent_type).toBe("continue")
     })
 
-    test("preserves subagent_type when session_id is provided with explicit subagent_type", async () => {
+    test("preserves subagent_type when task_id is provided with explicit subagent_type", async () => {
       //#given
       const ctx = createCtxWithSessionMessages()
       const handler = createToolExecuteBeforeHandler({ ctx, hooks: emptyHooks })
       const input = { tool: "task", sessionID: "ses_123", callID: "call_1" }
-      const output = { args: { session_id: "ses_abc123", subagent_type: "explore", description: "Continue explore" } as Record<string, unknown> }
+      const output = { args: { task_id: "ses_abc123", subagent_type: "explore", description: "Continue explore" } as Record<string, unknown> }
 
       //#when
       await handler(input, output)
@@ -223,7 +223,7 @@ describe("createToolExecuteBeforeHandler", () => {
       expect(output.args.subagent_type).toBeUndefined()
     })
 
-    test("does not set subagent_type when neither category nor session_id is provided and subagent_type is present", async () => {
+    test("does not set subagent_type when neither category nor task_id is provided and subagent_type is present", async () => {
       //#given
       const ctx = createCtxWithSessionMessages()
       const handler = createToolExecuteBeforeHandler({ ctx, hooks: emptyHooks })

src/plugin/tool-execute-before.ts

@@ -100,16 +100,7 @@ export function createToolExecuteBeforeHandler(args: {
       const argsObject = output.args
       const category = typeof argsObject.category === "string" ? argsObject.category : undefined
       const subagentType = typeof argsObject.subagent_type === "string" ? argsObject.subagent_type : undefined
-      const taskId =
-        typeof argsObject.task_id === "string"
-          ? argsObject.task_id
-          : typeof argsObject.session_id === "string"
-            ? argsObject.session_id
-            : undefined
-
-      if (taskId && typeof argsObject.task_id !== "string") {
-        argsObject.task_id = taskId
-      }
+      const taskId = typeof argsObject.task_id === "string" ? argsObject.task_id : undefined
 
       if (category) {
         argsObject.subagent_type = "sisyphus-junior"

src/tools/delegate-task/AGENTS.md

@@ -32,7 +32,7 @@
 sync-task.ts → sync-session-creator.ts → sync-prompt-sender.ts → sync-session-poller.ts → sync-result-fetcher.ts
 ```
 
-Each file handles one step. `sync-continuation.ts` handles session continuation (resume with session_id).
+Each file handles one step. `sync-continuation.ts` handles session continuation (resume with task_id).
 
 ## BACKGROUND EXECUTION
 
@@ -40,7 +40,7 @@ Each file handles one step. `sync-continuation.ts` handles session continuation
 background-task.ts → BackgroundManager.launch() → (async polling) → background-continuation.ts
 ```
 
-`background-continuation.ts` handles `session_id` resume for existing background tasks.
+`background-continuation.ts` handles `task_id` resume for existing background tasks.
 
 ## CATEGORY RESOLUTION
 

src/tools/delegate-task/background-continuation.test.ts

@@ -30,7 +30,7 @@ describe("executeBackgroundContinuation - subagent metadata", () => {
     }
 
     const args = {
-      session_id: "ses_resumed_123",
+      task_id: "ses_resumed_123",
       prompt: "continue working",
       description: "resume oracle",
       load_skills: [],
@@ -76,7 +76,7 @@ describe("executeBackgroundContinuation - subagent metadata", () => {
     }
 
     const args = {
-      session_id: "ses_resumed_456",
+      task_id: "ses_resumed_456",
       prompt: "continue",
       description: "resume task",
       load_skills: [],

src/tools/delegate-task/metadata-model-unification.test.ts

@@ -122,7 +122,7 @@ describe("metadata model unification", () => {
         const ctx = makeMockCtx()
         const args: DelegateTaskArgs = {
           description: "continue", prompt: "keep going",
-          load_skills: [], run_in_background: true, session_id: "ses_resumed",
+          load_skills: [], run_in_background: true, task_id: "ses_resumed",
         }
 
         await executeBackgroundContinuation(args, ctx, {
@@ -144,7 +144,7 @@ describe("metadata model unification", () => {
         const ctx = makeMockCtx()
         const args: DelegateTaskArgs = {
           description: "continue", prompt: "keep going",
-          load_skills: [], run_in_background: false, session_id: "ses_cont",
+          load_skills: [], run_in_background: false, task_id: "ses_cont",
         }
 
         const deps = {

src/tools/delegate-task/sync-continuation.test.ts

@@ -86,7 +86,7 @@ describe("executeSyncContinuation - toast cleanup error paths", () => {
     }
 
     const args = {
-      session_id: "ses_test_12345678",
+      task_id: "ses_test_12345678",
       prompt: "test prompt",
       description: "test task",
       load_skills: [],
@@ -148,7 +148,7 @@ describe("executeSyncContinuation - toast cleanup error paths", () => {
     }
 
     const args = {
-      session_id: "ses_test_12345678",
+      task_id: "ses_test_12345678",
       prompt: "test prompt",
       description: "test task",
       load_skills: [],
@@ -214,7 +214,7 @@ describe("executeSyncContinuation - toast cleanup error paths", () => {
     }
 
     const args = {
-      session_id: "ses_test_12345678",
+      task_id: "ses_test_12345678",
       prompt: "test prompt",
       description: "test task",
       load_skills: [],
@@ -278,7 +278,7 @@ describe("executeSyncContinuation - toast cleanup error paths", () => {
     }
 
     const args = {
-      session_id: "ses_test_12345678",
+      task_id: "ses_test_12345678",
       prompt: "test prompt",
       description: "test task",
       load_skills: [],
@@ -335,7 +335,7 @@ describe("executeSyncContinuation - toast cleanup error paths", () => {
     }
 
     const args = {
-      session_id: "ses_test_12345678",
+      task_id: "ses_test_12345678",
       prompt: "test prompt",
       description: "test task",
       load_skills: [],
@@ -395,7 +395,7 @@ describe("executeSyncContinuation - toast cleanup error paths", () => {
     }
 
     const args = {
-      session_id: "ses_test_12345678",
+      task_id: "ses_test_12345678",
       prompt: "continue working",
       description: "resume oracle task",
       load_skills: [],
@@ -449,7 +449,7 @@ describe("executeSyncContinuation - toast cleanup error paths", () => {
     }
 
     const args = {
-      session_id: "ses_test_12345678",
+      task_id: "ses_test_12345678",
       prompt: "continue working",
       description: "resume task",
       load_skills: [],
@@ -514,7 +514,7 @@ describe("executeSyncContinuation - toast cleanup error paths", () => {
     }
 
     const args = {
-      session_id: "ses_test_12345678",
+      task_id: "ses_test_12345678",
       prompt: "continue working",
       description: "resume explore task",
       load_skills: [],
@@ -584,7 +584,7 @@ describe("executeSyncContinuation - toast cleanup error paths", () => {
     }
 
     const args = {
-      session_id: "ses_test_12345678",
+      task_id: "ses_test_12345678",
       prompt: "continue researching",
       description: "resume librarian task",
       load_skills: [],
@@ -654,7 +654,7 @@ describe("executeSyncContinuation - toast cleanup error paths", () => {
     }
 
     const args = {
-      session_id: "ses_test_12345678",
+      task_id: "ses_test_12345678",
       prompt: "continue planning",
       description: "resume prometheus task",
       load_skills: [],

src/tools/delegate-task/task-id.ts

@@ -1,5 +1,5 @@
 import type { DelegateTaskArgs } from "./types"
 
-export function getTaskID(args: Pick<DelegateTaskArgs, "task_id" | "session_id">): string | undefined {
-  return args.task_id ?? args.session_id
+export function getTaskID(args: Pick<DelegateTaskArgs, "task_id">): string | undefined {
+  return args.task_id
 }

src/tools/delegate-task/tools.test.ts

@@ -1359,7 +1359,7 @@ describe("sisyphus-task", () => {
       )).rejects.toThrow("Invalid arguments: 'run_in_background' parameter is REQUIRED")
     })
 
-    test("#given session_id without run_in_background #when executing #then throws required parameter error", async () => {
+    test("#given task_id without run_in_background #when executing #then throws required parameter error", async () => {
       // given
       const { createDelegateTask } = require("./tools")
       const mockManager = { resume: async () => ({ id: "task-1", sessionID: "ses_1", status: "running" }) }
@@ -1381,14 +1381,14 @@ describe("sisyphus-task", () => {
         {
           description: "Continue without run flag",
           prompt: "Continue",
-          session_id: "ses_existing",
+          task_id: "ses_existing",
           load_skills: [],
         },
         { sessionID: "parent-session", messageID: "parent-message", agent: "sisyphus", abort: new AbortController().signal }
       )).rejects.toThrow("Invalid arguments: 'run_in_background' parameter is REQUIRED")
     })
 
-    test("#given no category no subagent_type no session_id and no run_in_background #when executing #then throws required parameter error", async () => {
+    test("#given no category no subagent_type no task_id and no run_in_background #when executing #then throws required parameter error", async () => {
       // given
       const { createDelegateTask } = require("./tools")
       const mockManager = { launch: async () => ({}) }
@@ -1719,8 +1719,8 @@ describe("sisyphus-task", () => {
     }, { timeout: 10000 })
   })
 
-  describe("session_id with background parameter", () => {
-  test("session_id with background=false should wait for result and return content", async () => {
+  describe("task_id with background parameter", () => {
+  test("task_id with background=false should wait for result and return content", async () => {
     // Note: This test needs extended timeout because the implementation has MIN_STABILITY_TIME_MS = 5000
     // given
     const { createDelegateTask } = require("./tools")
@@ -1808,7 +1808,7 @@ describe("sisyphus-task", () => {
        {
          description: "Continue test",
          prompt: "Continue the task",
-         session_id: "ses_continue_test",
+         task_id: "ses_continue_test",
          run_in_background: false,
          load_skills: ["git-master"],
        },
@@ -1905,7 +1905,7 @@ describe("sisyphus-task", () => {
       {
         description: "Continue with variant",
         prompt: "Continue the task",
-        session_id: "ses_var_test",
+        task_id: "ses_var_test",
         run_in_background: false,
         load_skills: [],
       },
@@ -1920,7 +1920,7 @@ describe("sisyphus-task", () => {
     expect(callArgs.body.model).toEqual({ providerID: "anthropic", modelID: "claude-opus-4-6" })
   }, { timeout: 10000 })
 
-  test("session_id with background=true should return immediately without waiting", async () => {
+  test("task_id with background=true should return immediately without waiting", async () => {
     // given
     const { createDelegateTask } = require("./tools")
     
@@ -1964,7 +1964,7 @@ describe("sisyphus-task", () => {
        {
          description: "Continue bg test",
          prompt: "Continue in background",
-         session_id: "ses_bg_continue",
+         task_id: "ses_bg_continue",
          run_in_background: true,
          load_skills: ["git-master"],
        },

src/tools/delegate-task/tools.ts

@@ -85,7 +85,6 @@ export function createDelegateTask(options: DelegateTaskToolOptions): ToolDefini
   - subagent_type: Use specific agent directly (explore, librarian, oracle, metis, momus)
   - run_in_background: REQUIRED. true=async (returns task_id), false=sync (waits). Use background=true ONLY for parallel exploration with 5+ independent queries.
   - task_id: Existing task to continue (from previous task output). Continues the same subagent session with FULL CONTEXT PRESERVED.
-  - session_id: Deprecated alias for task_id. Accepted for backward compatibility.
   - command: The command that triggered this task (optional, for slash command tracking).
   
   **WHEN TO USE task_id:**
@@ -105,14 +104,10 @@ export function createDelegateTask(options: DelegateTaskToolOptions): ToolDefini
       category: tool.schema.string().optional().describe(`REQUIRED if subagent_type not provided. Do NOT provide both category and subagent_type.`),
       subagent_type: tool.schema.string().optional().describe("REQUIRED if category not provided. Do NOT provide both category and subagent_type."),
       task_id: tool.schema.string().optional().describe("Existing task to continue. Canonical resume identifier."),
-      session_id: tool.schema.string().optional().describe("Deprecated alias for task_id. Existing task to continue."),
       command: tool.schema.string().optional().describe("The command that triggered this task"),
     },
     async execute(args: DelegateTaskArgs, toolContext) {
       const ctx = toolContext as ToolContextWithMetadata
-      if (!args.task_id && args.session_id) {
-        args.task_id = args.session_id
-      }
 
       if (args.category) {
         if (args.subagent_type && args.subagent_type !== SISYPHUS_JUNIOR_AGENT) {
@@ -163,7 +158,7 @@ export function createDelegateTask(options: DelegateTaskToolOptions): ToolDefini
 
       const parentContext = await resolveParentContext(ctx, options.client)
 
-      if (args.task_id || args.session_id) {
+      if (args.task_id) {
         if (runInBackground) {
           return executeBackgroundContinuation(args, ctx, options, parentContext)
         }

src/tools/delegate-task/types.ts

@@ -15,8 +15,6 @@ export interface DelegateTaskArgs {
   subagent_type?: string
   run_in_background: boolean
   task_id?: string
-  /** @deprecated Use task_id instead. */
-  session_id?: string
   command?: string
   load_skills: string[]
   execute?: {