fix(background-task): clarify task id contracts

src/agents/atlas/atlas-prompt.test.ts

@@ -126,6 +126,13 @@ describe("Atlas prompts use task_id (not session_id) for retries", () => {
       expect(prompt, `${name}: missing task_id retry reference`).toMatch(/task_id/)
     }
   })
+
+  test("all variants should separate background ids from continuation task ids", () => {
+    for (const [name, prompt] of ALL_VARIANTS) {
+      expect(prompt, `${name}: missing bg result collection contract`).toContain('background_output(task_id="bg_...")')
+      expect(prompt, `${name}: missing ses continuation contract`).toContain('task(task_id="ses_..."')
+    }
+  })
 })
 
 describe("Atlas prompts no-excuses retry policy", () => {

src/agents/atlas/default-prompt-sections.ts

@@ -243,6 +243,6 @@ export const DEFAULT_ATLAS_CRITICAL_RULES = `<critical_overrides>
 - Run lsp_diagnostics after every delegation
 - Pass inherited wisdom to every subagent
 - Verify with your own tools
-- **Store task_id from every delegation output**
-- **Use \`task_id="{task_id}"\` for retries, fixes, and follow-ups**
+- **Store continuation task_id (\`ses_...\`) from every delegation output**
+- **Use \`task(task_id="ses_...", prompt="...")\` for retries, fixes, and follow-ups**
 </critical_overrides>`

src/agents/atlas/kimi-prompt-sections.ts

@@ -216,6 +216,6 @@ export const KIMI_ATLAS_CRITICAL_RULES = `<critical_overrides>
 - Run lsp_diagnostics after every delegation
 - Pass inherited wisdom to every subagent
 - Verify with your own tools
-- **Store task_id from every delegation output**
-- **Use \`task_id="{task_id}"\` for retries, fixes, and follow-ups**
+- **Store continuation task_id (\`ses_...\`) from every delegation output**
+- **Use \`task(task_id="ses_...", prompt="...")\` for retries, fixes, and follow-ups**
 </critical_overrides>`

src/agents/atlas/opus-4-7-prompt-sections.ts

@@ -232,6 +232,6 @@ export const OPUS_47_ATLAS_CRITICAL_RULES = `<critical_overrides>
 - Run lsp_diagnostics after every delegation
 - Pass inherited wisdom to every subagent
 - Verify with your own tools
-- **Store task_id from every delegation output**
-- **Use \`task_id="{task_id}"\` for retries, fixes, and follow-ups**
+- **Store continuation task_id (\`ses_...\`) from every delegation output**
+- **Use \`task(task_id="ses_...", prompt="...")\` for retries, fixes, and follow-ups**
 </critical_overrides>`

src/agents/atlas/shared-prompt.ts

@@ -120,7 +120,8 @@ task(category="quick", load_skills=[], run_in_background=false, prompt="...task
 - **Task execution** (\`category="..."\`): \`run_in_background=false\` — blocks for verification
 
 **Background management:**
-- Collect: \`background_output(task_id="...")\`
+- Collect with background task IDs (\`bg_...\`): \`background_output(task_id="bg_...")\`
+- Continue follow-ups with continuation task IDs (\`ses_...\`): \`task(task_id="ses_...")\`
 - Cancel DISPOSABLE background tasks individually before final answer: \`background_cancel(taskId="bg_explore_xxx")\`
 - **NEVER \`background_cancel(all=true)\`** — it kills tasks whose output you have not collected.
 </parallel_by_default>`