fix(subagent): address background-first review

examples/acp-agent/tests/snapshots/advanced-toolchain/session.1.jsonl

@@ -6,7 +6,7 @@
 {"type":"subagent/descriptor","seq":4,"time":1786357538308,"data":{"version":2,"mode":"one-shot","provider":"spawn","label":"Check direct child"}}
 {"type":"step/start","seq":5,"time":1786357538310,"data":{"turn":1,"step":1}}
 {"type":"user/message","seq":6,"time":1785730458555,"data":{"content":[{"type":"text","text":"Reply with exactly DIRECT_CHILD_OK and nothing else."}],"source":{"kind":"user"},"role":"user","id":"ebe0cfa0-a909-47e0-8294-28ad84a8fe77"},"surfaceOp":"append"}
-{"type":"user/message","seq":7,"time":1786357538310,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"1f81ee1b-b08e-4fba-a075-426e41dd03d4"},"surfaceOp":"append"}
+{"type":"user/message","seq":7,"time":1786357538310,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"10c6c81d-85a2-4c50-a8c2-2f58f309f070"},"surfaceOp":"append"}
 {"type":"session/title","seq":8,"time":1786357538310,"data":{"title":"Reply with exactly DIRECT_CHILD_OK and","messageSeqs":[6],"source":{"kind":"fallback"}}}
 {"type":"request/header","seq":9,"time":1785730458555,"data":{"header":{"config":{"provider":"deepseek-official","model":"deepseek-v4-flash"},"system":"{{system}}","tools":"{{tools}}"},"reason":"initial"}}
 {"type":"request/context","seq":10,"time":1785730458555,"data":{"provider":"deepseek-official","model":"deepseek-v4-flash"}}

examples/acp-agent/tests/snapshots/advanced-toolchain/session.2.jsonl

@@ -6,7 +6,7 @@
 {"type":"subagent/descriptor","seq":4,"time":1786357538469,"data":{"version":2,"mode":"one-shot","provider":"spawn"}}
 {"type":"step/start","seq":5,"time":1786357538470,"data":{"turn":1,"step":1}}
 {"type":"user/message","seq":6,"time":1785730458703,"data":{"content":[{"type":"text","text":"Reply with exactly WORKFLOW_CHILD_OK and nothing else."}],"source":{"kind":"user"},"role":"user","id":"2ac2cc54-9bce-4cfa-a569-a64f51bc30a7"},"surfaceOp":"append"}
-{"type":"user/message","seq":7,"time":1786357538471,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"dbf0fe20-f0e0-4700-b0fc-d192f5e7b1ca"},"surfaceOp":"append"}
+{"type":"user/message","seq":7,"time":1786357538471,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"5a8c5ad7-352c-475a-9356-87510cc6b1a8"},"surfaceOp":"append"}
 {"type":"session/title","seq":8,"time":1786357538471,"data":{"title":"Reply with exactly WORKFLOW_CHILD_OK and","messageSeqs":[6],"source":{"kind":"fallback"}}}
 {"type":"request/header","seq":9,"time":1785730458703,"data":{"header":{"config":{"provider":"deepseek-official","model":"deepseek-v4-flash"},"system":"{{system}}","tools":"{{tools}}"},"reason":"initial"}}
 {"type":"request/context","seq":10,"time":1785730458703,"data":{"provider":"deepseek-official","model":"deepseek-v4-flash"}}

examples/acp-agent/tests/snapshots/advanced-toolchain/system-prompt.expected.md

@@ -21,7 +21,7 @@ Use the workflow tool ONLY when the user explicitly asks for a workflow or for l
 
 Use the ralph tool ONLY when the direct human explicitly asks for a Ralph loop or fresh-agent iterative execution. Each Ralph round starts a fresh child with no conversation seed and uses the shared workspace as durable memory. Completion and blockers are worker reports, not independent evaluation. Use same-session goal tools for ordinary long-running objectives, and plain subagents or workflows for bounded delegation and fan-out.
 
-Use subagent's continuable background route by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when you cannot take your next action without that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.
+Use subagent in the background by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when your next action depends on that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.
 
 ## Writing code for run_code
 
@@ -134,13 +134,13 @@ interface ToolArgsMap {
     /** The exact skill name from the available skills list. */
     name: string;
   } & Record<string, JsonValue>;
-  /** Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool uses its continuable background route by default and immediately returns a durable subagent id. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` to use a foreground run only when you must receive its result before taking your next action. */
+  /** Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result. */
   subagent: {
     /** A short (3-5 word) description of the delegated task, for display. */
     description: string;
     /** The complete, self-contained task for the subagent. It does not share this conversation's context, so include everything it needs. */
     prompt: string;
-    /** Whether to use the continuable background route. Defaults to true. Set false to run in the foreground and wait only when your next action depends on its result. */
+    /** Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it. */
     run_in_background?: boolean;
   } & Record<string, JsonValue>;
   /** Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn). Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive its result, not its intermediate steps. This call waits for the subagent and returns its result. */

examples/acp-agent/tests/snapshots/advanced-toolchain/tool-schemas.expected.json

@@ -309,7 +309,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool uses its continuable background route by default and immediately returns a durable subagent id. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` to use a foreground run only when you must receive its result before taking your next action.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -323,7 +323,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Whether to use the continuable background route. Defaults to true. Set false to run in the foreground and wait only when your next action depends on its result."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [

examples/acp-agent/tests/snapshots/both-mode-turn/tool-schemas.expected.json

@@ -252,7 +252,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool uses its continuable background route by default and immediately returns a durable subagent id. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` to use a foreground run only when you must receive its result before taking your next action.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -266,7 +266,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Whether to use the continuable background route. Defaults to true. Set false to run in the foreground and wait only when your next action depends on its result."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [

examples/acp-agent/tests/snapshots/code-mode-turn/system-prompt.expected.md

@@ -21,7 +21,7 @@ Use the workflow tool ONLY when the user explicitly asks for a workflow or for l
 
 Use the ralph tool ONLY when the direct human explicitly asks for a Ralph loop or fresh-agent iterative execution. Each Ralph round starts a fresh child with no conversation seed and uses the shared workspace as durable memory. Completion and blockers are worker reports, not independent evaluation. Use same-session goal tools for ordinary long-running objectives, and plain subagents or workflows for bounded delegation and fan-out.
 
-Use subagent's continuable background route by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when you cannot take your next action without that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.
+Use subagent in the background by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when your next action depends on that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.
 
 ## Writing code for run_code
 
@@ -117,13 +117,13 @@ interface ToolArgsMap {
     /** The exact skill name from the available skills list. */
     name: string;
   } & Record<string, JsonValue>;
-  /** Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool uses its continuable background route by default and immediately returns a durable subagent id. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` to use a foreground run only when you must receive its result before taking your next action. */
+  /** Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result. */
   subagent: {
     /** A short (3-5 word) description of the delegated task, for display. */
     description: string;
     /** The complete, self-contained task for the subagent. It does not share this conversation's context, so include everything it needs. */
     prompt: string;
-    /** Whether to use the continuable background route. Defaults to true. Set false to run in the foreground and wait only when your next action depends on its result. */
+    /** Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it. */
     run_in_background?: boolean;
   } & Record<string, JsonValue>;
   /** Delegate a task to a subagent that inherits this conversation: a child agent seeded with all completed turns so far (it does not see the current in-flight turn). Use this when the subtask builds on this conversation's context — a follow-up analysis, a review, a continuation — without consuming this conversation's context for the work itself. You receive its result, not its intermediate steps. This call waits for the subagent and returns its result. */

examples/acp-agent/tests/snapshots/lsp-definition/system-prompt.expected.md

@@ -23,4 +23,4 @@ Use the workflow tool ONLY when the user explicitly asks for a workflow or for l
 
 Use the ralph tool ONLY when the direct human explicitly asks for a Ralph loop or fresh-agent iterative execution. Each Ralph round starts a fresh child with no conversation seed and uses the shared workspace as durable memory. Completion and blockers are worker reports, not independent evaluation. Use same-session goal tools for ordinary long-running objectives, and plain subagents or workflows for bounded delegation and fan-out.
 
-Use subagent's continuable background route by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when you cannot take your next action without that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.
+Use subagent in the background by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when your next action depends on that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.

examples/acp-agent/tests/snapshots/lsp-definition/tool-schemas.expected.json

@@ -268,7 +268,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool uses its continuable background route by default and immediately returns a durable subagent id. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` to use a foreground run only when you must receive its result before taking your next action.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -282,7 +282,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Whether to use the continuable background route. Defaults to true. Set false to run in the foreground and wait only when your next action depends on its result."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [

examples/acp-agent/tests/snapshots/product-subagent-both/tool-schemas.expected.json

@@ -231,7 +231,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool uses its continuable background route by default and immediately returns a durable subagent id. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` to use a foreground run only when you must receive its result before taking your next action.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -245,7 +245,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Whether to use the continuable background route. Defaults to true. Set false to run in the foreground and wait only when your next action depends on its result."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [

examples/acp-agent/tests/snapshots/product-subagent-codex/system-prompt.expected.md

@@ -21,4 +21,4 @@ Use the workflow tool ONLY when the user explicitly asks for a workflow or for l
 
 Use the ralph tool ONLY when the direct human explicitly asks for a Ralph loop or fresh-agent iterative execution. Each Ralph round starts a fresh child with no conversation seed and uses the shared workspace as durable memory. Completion and blockers are worker reports, not independent evaluation. Use same-session goal tools for ordinary long-running objectives, and plain subagents or workflows for bounded delegation and fan-out.
 
-Use subagent's continuable background route by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when you cannot take your next action without that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.
+Use subagent in the background by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when your next action depends on that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.

examples/acp-agent/tests/snapshots/product-subagent-codex/tool-schemas.expected.json

@@ -231,7 +231,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool uses its continuable background route by default and immediately returns a durable subagent id. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` to use a foreground run only when you must receive its result before taking your next action.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -245,7 +245,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Whether to use the continuable background route. Defaults to true. Set false to run in the foreground and wait only when your next action depends on its result."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [

examples/acp-agent/tests/snapshots/pty-tools/system-prompt.expected.md

@@ -23,4 +23,4 @@ Use the workflow tool ONLY when the user explicitly asks for a workflow or for l
 
 Use the ralph tool ONLY when the direct human explicitly asks for a Ralph loop or fresh-agent iterative execution. Each Ralph round starts a fresh child with no conversation seed and uses the shared workspace as durable memory. Completion and blockers are worker reports, not independent evaluation. Use same-session goal tools for ordinary long-running objectives, and plain subagents or workflows for bounded delegation and fan-out.
 
-Use subagent's continuable background route by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when you cannot take your next action without that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.
+Use subagent in the background by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when your next action depends on that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.

examples/acp-agent/tests/snapshots/pty-tools/tool-schemas.expected.json

@@ -231,7 +231,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool uses its continuable background route by default and immediately returns a durable subagent id. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` to use a foreground run only when you must receive its result before taking your next action.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -245,7 +245,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Whether to use the continuable background route. Defaults to true. Set false to run in the foreground and wait only when your next action depends on its result."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [

examples/acp-agent/tests/snapshots/read-image/tool-schemas.expected.json

@@ -247,7 +247,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool uses its continuable background route by default and immediately returns a durable subagent id. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` to use a foreground run only when you must receive its result before taking your next action.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -261,7 +261,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Whether to use the continuable background route. Defaults to true. Set false to run in the foreground and wait only when your next action depends on its result."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [

examples/acp-agent/tests/snapshots/session-query-spill/system-prompt.expected.md

@@ -23,4 +23,4 @@ Use the workflow tool ONLY when the user explicitly asks for a workflow or for l
 
 Use the ralph tool ONLY when the direct human explicitly asks for a Ralph loop or fresh-agent iterative execution. Each Ralph round starts a fresh child with no conversation seed and uses the shared workspace as durable memory. Completion and blockers are worker reports, not independent evaluation. Use same-session goal tools for ordinary long-running objectives, and plain subagents or workflows for bounded delegation and fan-out.
 
-Use subagent's continuable background route by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when you cannot take your next action without that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.
+Use subagent in the background by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when your next action depends on that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.

examples/acp-agent/tests/snapshots/session-query-spill/tool-schemas.expected.json

@@ -435,7 +435,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool uses its continuable background route by default and immediately returns a durable subagent id. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` to use a foreground run only when you must receive its result before taking your next action.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -449,7 +449,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Whether to use the continuable background route. Defaults to true. Set false to run in the foreground and wait only when your next action depends on its result."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [

examples/acp-agent/tests/snapshots/subagent-child-question-rejection/tool-schemas.expected.json

@@ -294,7 +294,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool uses its continuable background route by default and immediately returns a durable subagent id. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` to use a foreground run only when you must receive its result before taking your next action.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -308,7 +308,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Whether to use the continuable background route. Defaults to true. Set false to run in the foreground and wait only when your next action depends on its result."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [

examples/acp-agent/tests/snapshots/subagent-continuable-inheritance/system-prompt.1.expected.md

@@ -21,6 +21,6 @@ Use the workflow tool ONLY when the user explicitly asks for a workflow or for l
 
 Use the ralph tool ONLY when the direct human explicitly asks for a Ralph loop or fresh-agent iterative execution. Each Ralph round starts a fresh child with no conversation seed and uses the shared workspace as durable memory. Completion and blockers are worker reports, not independent evaluation. Use same-session goal tools for ordinary long-running objectives, and plain subagents or workflows for bounded delegation and fan-out.
 
-Use subagent's continuable background route by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when you cannot take your next action without that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.
+Use subagent in the background by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when your next action depends on that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.
 
 Deliver your result with the report tool before you finish: call it once with a self-contained answer. The agent that started you shares your workspace but does not automatically receive your transcript, tool output, or reasoning, so a closing remark such as "done" leaves it nothing it can use. Report earlier as well whenever a partial finding changes what that agent should do next; reporting never ends your turn.

examples/acp-agent/tests/snapshots/subagent-continuable-inheritance/tool-schemas.1.expected.json

@@ -247,7 +247,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool uses its continuable background route by default and immediately returns a durable subagent id. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` to use a foreground run only when you must receive its result before taking your next action.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -261,7 +261,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Whether to use the continuable background route. Defaults to true. Set false to run in the foreground and wait only when your next action depends on its result."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [

examples/acp-agent/tests/snapshots/subagent-continuable/system-prompt.1.expected.md

@@ -21,6 +21,6 @@ Use the workflow tool ONLY when the user explicitly asks for a workflow or for l
 
 Use the ralph tool ONLY when the direct human explicitly asks for a Ralph loop or fresh-agent iterative execution. Each Ralph round starts a fresh child with no conversation seed and uses the shared workspace as durable memory. Completion and blockers are worker reports, not independent evaluation. Use same-session goal tools for ordinary long-running objectives, and plain subagents or workflows for bounded delegation and fan-out.
 
-Use subagent's continuable background route by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when you cannot take your next action without that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.
+Use subagent in the background by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when your next action depends on that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.
 
 Deliver your result with the report tool before you finish: call it once with a self-contained answer. The agent that started you shares your workspace but does not automatically receive your transcript, tool output, or reasoning, so a closing remark such as "done" leaves it nothing it can use. Report earlier as well whenever a partial finding changes what that agent should do next; reporting never ends your turn.

examples/acp-agent/tests/snapshots/subagent-continuable/tool-schemas.1.expected.json

@@ -247,7 +247,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool uses its continuable background route by default and immediately returns a durable subagent id. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` to use a foreground run only when you must receive its result before taking your next action.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -261,7 +261,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Whether to use the continuable background route. Defaults to true. Set false to run in the foreground and wait only when your next action depends on its result."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [

examples/acp-agent/tests/snapshots/subagent-depth-two-rejection/session.1.jsonl

@@ -6,7 +6,7 @@
 {"type":"subagent/descriptor","seq":4,"time":1786357533600,"data":{"version":2,"mode":"one-shot","provider":"spawn","label":"Start depth one"}}
 {"type":"step/start","seq":5,"time":1786357533602,"data":{"turn":1,"step":1}}
 {"type":"user/message","seq":6,"time":1785730456014,"data":{"content":[{"type":"text","text":"Call subagent once. Ask that child to attempt one further subagent call, then report the result."}],"source":{"kind":"user"},"role":"user","id":"a8129357-1bde-4cbd-90b4-6b8ad51d52e1"},"surfaceOp":"append"}
-{"type":"user/message","seq":7,"time":1786357533602,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"212db1ef-823c-46f6-8a3b-ccc4f5e92bc5"},"surfaceOp":"append"}
+{"type":"user/message","seq":7,"time":1786357533602,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"837ea332-428c-4e4a-b3f1-df24dd20c93a"},"surfaceOp":"append"}
 {"type":"session/title","seq":8,"time":1786357533602,"data":{"title":"Call subagent once. Ask that","messageSeqs":[6],"source":{"kind":"fallback"}}}
 {"type":"request/header","seq":9,"time":1785730456014,"data":{"header":{"config":{"provider":"deepseek-official","model":"deepseek-v4-flash"},"system":"{{system}}","tools":"{{tools}}"},"reason":"initial"}}
 {"type":"request/context","seq":10,"time":1785730456014,"data":{"provider":"deepseek-official","model":"deepseek-v4-flash"}}

examples/acp-agent/tests/snapshots/subagent-depth-two-rejection/session.2.jsonl

@@ -6,7 +6,7 @@
 {"type":"subagent/descriptor","seq":4,"time":1786357533628,"data":{"version":2,"mode":"one-shot","provider":"spawn","label":"Start depth two"}}
 {"type":"step/start","seq":5,"time":1786357533630,"data":{"turn":1,"step":1}}
 {"type":"user/message","seq":6,"time":1785730456041,"data":{"content":[{"type":"text","text":"Attempt one subagent call beyond the configured cap, then report the rejection."}],"source":{"kind":"user"},"role":"user","id":"d4dc5a16-e542-4dd9-8e82-e6b7829cfc4b"},"surfaceOp":"append"}
-{"type":"user/message","seq":7,"time":1786357533630,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"db7bb37e-3447-4ac8-82cd-2566300acea1"},"surfaceOp":"append"}
+{"type":"user/message","seq":7,"time":1786357533630,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"a62cf283-f87f-4f6f-be16-a00978557f99"},"surfaceOp":"append"}
 {"type":"session/title","seq":8,"time":1786357533630,"data":{"title":"Attempt one subagent call beyond","messageSeqs":[6],"source":{"kind":"fallback"}}}
 {"type":"request/header","seq":9,"time":1785730456041,"data":{"header":{"config":{"provider":"deepseek-official","model":"deepseek-v4-flash"},"system":"{{system}}","tools":"{{tools}}"},"reason":"initial"}}
 {"type":"request/context","seq":10,"time":1785730456042,"data":{"provider":"deepseek-official","model":"deepseek-v4-flash"}}

examples/acp-agent/tests/snapshots/subagent-list-agents/system-prompt.1.expected.md

@@ -21,6 +21,6 @@ Use the workflow tool ONLY when the user explicitly asks for a workflow or for l
 
 Use the ralph tool ONLY when the direct human explicitly asks for a Ralph loop or fresh-agent iterative execution. Each Ralph round starts a fresh child with no conversation seed and uses the shared workspace as durable memory. Completion and blockers are worker reports, not independent evaluation. Use same-session goal tools for ordinary long-running objectives, and plain subagents or workflows for bounded delegation and fan-out.
 
-Use subagent's continuable background route by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when you cannot take your next action without that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.
+Use subagent in the background by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when your next action depends on that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.
 
 Deliver your result with the report tool before you finish: call it once with a self-contained answer. The agent that started you shares your workspace but does not automatically receive your transcript, tool output, or reasoning, so a closing remark such as "done" leaves it nothing it can use. Report earlier as well whenever a partial finding changes what that agent should do next; reporting never ends your turn.

examples/acp-agent/tests/snapshots/subagent-list-agents/tool-schemas.1.expected.json

@@ -247,7 +247,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool uses its continuable background route by default and immediately returns a durable subagent id. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` to use a foreground run only when you must receive its result before taking your next action.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -261,7 +261,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Whether to use the continuable background route. Defaults to true. Set false to run in the foreground and wait only when your next action depends on its result."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [

examples/acp-agent/tests/snapshots/subagent-mixed/session.1.jsonl

@@ -6,7 +6,7 @@
 {"type":"subagent/descriptor","seq":4,"time":1786443013990,"data":{"version":2,"mode":"one-shot","provider":"spawn","label":"Reply ALPHA only"}}
 {"type":"step/start","seq":5,"time":1786443013993,"data":{"turn":1,"step":1}}
 {"type":"user/message","seq":6,"time":1786443013993,"data":{"content":[{"type":"text","text":"Reply with exactly the word ALPHA and nothing else."}],"source":{"kind":"user"},"role":"user","id":"73ce401a-faaf-408a-879e-7485380d537d"},"surfaceOp":"append"}
-{"type":"user/message","seq":7,"time":1786357524755,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"64e0fe5e-a3a5-44f1-bf43-b7dc74fad046"},"surfaceOp":"append"}
+{"type":"user/message","seq":7,"time":1786357524755,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"b5f31276-8b68-4182-8f90-32a3eb710968"},"surfaceOp":"append"}
 {"type":"session/title","seq":8,"time":1786357524755,"data":{"title":"Reply with exactly the word","messageSeqs":[6],"source":{"kind":"fallback"}}}
 {"type":"request/header","seq":9,"time":1786443013994,"data":{"header":{"config":{"provider":"deepseek-official","model":"deepseek-v4-flash"},"system":"{{system}}","tools":"{{tools}}"},"reason":"initial"}}
 {"type":"request/context","seq":10,"time":1786443013994,"data":{"provider":"deepseek-official","model":"deepseek-v4-flash"}}

examples/acp-agent/tests/snapshots/subagent-mixed/session.2.jsonl

@@ -27,7 +27,7 @@
 {"type":"subagent/descriptor","seq":41,"time":1786357524800,"data":{"version":2,"mode":"one-shot","provider":"fork","label":"Recall project codeword"}}
 {"type":"step/start","seq":42,"time":1786357524803,"data":{"turn":2,"step":1}}
 {"type":"user/message","seq":43,"time":1786357524803,"data":{"content":[{"type":"text","text":"What is the project codeword mentioned earlier in this conversation? Reply with exactly that one word and nothing else."}],"source":{"kind":"user"},"role":"user","id":"86e9f144-764f-460d-b72b-262cffe43d77"},"surfaceOp":"append"}
-{"type":"user/message","seq":44,"time":1786358036899,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"822cdf7d-2a4d-4e51-9a7b-212db77f8b94"},"surfaceOp":"append"}
+{"type":"user/message","seq":44,"time":1786358036899,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"3cf7eb4d-7ce0-4021-b477-ecb16b62ba60"},"surfaceOp":"append"}
 {"type":"request/header","seq":45,"time":1786358036900,"data":{"header":{"config":{"provider":"deepseek-official","model":"deepseek-v4-flash"},"system":"{{system}}","tools":"{{tools}}"},"reason":"resume"}}
 {"type":"assistant/chunk","seq":46,"time":1783352148077,"data":{"turn":2,"step":1,"chunk":{"type":"block-start","index":0,"blockType":"reasoning"}}}
 {"type":"reasoning-chunks","seq0":47,"time0":1783352148077,"data":{"turn":2,"step":1,"index":0,"dt":[0,0,29,0,0,0,35,0,0,0,0,26,29,31,0,30,0,0,27,1,27,0,1,0,0,31,1,0,0,1790157964],"texts":["The"," user"," is"," asking"," me"," to"," recall"," the"," project"," cod","ew","ord"," that"," was"," mentioned"," earlier"," in"," the"," conversation","."," I"," was"," told"," to"," remember"," it",":"," SA","FF","RON","."]}}

examples/acp-agent/tests/snapshots/subagent-mixed/session.jsonl

@@ -50,8 +50,8 @@
 {"type":"tool/result","seq":214,"time":1786443014049,"data":{"turn":2,"step":2,"message":{"source":{"kind":"tool","callId":"call_00_JSr5rhREq23wSmwSkCP77184"},"content":[{"type":"tool-result","toolCallId":"call_00_JSr5rhREq23wSmwSkCP77184","content":[{"type":"text","text":"SAFFRON"}],"isError":false}],"role":"user","id":"4e5624d0-b633-4df7-ad19-db764e298422"}},"sourceEventSeqs":[213],"surfaceOp":"append"}
 {"type":"step/end","seq":215,"time":1786443014050,"data":{"turn":2,"step":2}}
 {"type":"step/start","seq":216,"time":1786443014055,"data":{"turn":2,"step":3}}
-{"type":"assistant/chunk","seq":217,"time":1786443014060,"data":{"turn":2,"step":3,"chunk":{"type":"block-start","index":0,"blockType":"reasoning"}}}
-{"type":"reasoning-chunks","seq0":218,"time0":1786437123085,"data":{"turn":2,"step":3,"index":0,"dt":[1,-3084973840,0,0,27,1,31,1,24,1,0,0,0,0,28,0,1,0,0,28,0,0,28,1,0,28,0,29,29,0,33,0,23,29,31,31,0,0,0,27,0,0,0,0,0,29,0,0,1,27,1,0,0,0,27,1,0,28,1,0,0,0,0],"texts":["Both"," sub","agents"," returned",":\n","1","."," First"," (","fresh"," child","):"," \"","AL","P","HA","\"\n","2","."," Second"," (","fork","ed"," child","):"," \"","SA","FF","RON","\""," -"," correctly"," inherited"," the"," conversation"," context"," where"," I"," was"," asked"," to"," remember"," the"," cod","ew","ord"," \"","SA","FF","RON","\".\n\n","Now"," I"," reply"," with"," \"","PAR","ENT","_D","ONE","\""," as"," instructed","."]}}
+{"type":"assistant/chunk","seq":217,"time":1783352149217,"data":{"turn":2,"step":3,"chunk":{"type":"block-start","index":0,"blockType":"reasoning"}}}
+{"type":"reasoning-chunks","seq0":218,"time0":1783352149246,"data":{"turn":2,"step":3,"index":0,"dt":[0,0,0,0,27,1,31,1,24,1,0,0,0,0,28,0,1,0,0,28,0,0,28,1,0,28,0,29,29,0,33,0,23,29,31,31,0,0,0,27,0,0,0,0,0,29,0,0,1,27,1,0,0,0,27,1,0,28,1,0,0,0,0],"texts":["Both"," sub","agents"," returned",":\n","1","."," First"," (","fresh"," child","):"," \"","AL","P","HA","\"\n","2","."," Second"," (","fork","ed"," child","):"," \"","SA","FF","RON","\""," -"," correctly"," inherited"," the"," conversation"," context"," where"," I"," was"," asked"," to"," remember"," the"," cod","ew","ord"," \"","SA","FF","RON","\".\n\n","Now"," I"," reply"," with"," \"","PAR","ENT","_D","ONE","\""," as"," instructed","."]}}
 {"type":"assistant/chunk","seq":282,"time":1783352149821,"data":{"turn":2,"step":3,"chunk":{"type":"block-start","index":1,"blockType":"text"}}}
 {"type":"text-chunks","seq0":283,"time0":1783352149821,"data":{"turn":2,"step":3,"index":1,"dt":[0,0,0],"texts":["PAR","ENT","_D","ONE"]}}
 {"type":"assistant/chunk","seq":287,"time":1785498797528,"data":{"turn":2,"step":3,"chunk":{"type":"block-end","index":0,"block":{"type":"reasoning","text":"Both subagents returned:\n1. First (fresh child): \"ALPHA\"\n2. Second (forked child): \"SAFFRON\" - correctly inherited the conversation context where I was asked to remember the codeword \"SAFFRON\".\n\nNow I reply with \"PARENT_DONE\" as instructed."}}}}

examples/acp-agent/tests/snapshots/subagent-multi/session.1.jsonl

@@ -6,7 +6,7 @@
 {"type":"subagent/descriptor","seq":4,"time":1786357521754,"data":{"version":2,"mode":"one-shot","provider":"spawn","label":"Return ALPHA only"}}
 {"type":"step/start","seq":5,"time":1786357521756,"data":{"turn":1,"step":1}}
 {"type":"user/message","seq":6,"time":1785730447828,"data":{"content":[{"type":"text","text":"Reply with exactly the word ALPHA and nothing else."}],"source":{"kind":"user"},"role":"user","id":"a287f842-f6f2-4a17-ab4c-820e41f498d5"},"surfaceOp":"append"}
-{"type":"user/message","seq":7,"time":1786357521756,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"a9ee240c-e856-4a1a-8b21-7540309c45d4"},"surfaceOp":"append"}
+{"type":"user/message","seq":7,"time":1786357521756,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"59d87d55-736f-4836-be4e-084a9f5cc7b1"},"surfaceOp":"append"}
 {"type":"session/title","seq":8,"time":1786357521756,"data":{"title":"Reply with exactly the word","messageSeqs":[6],"source":{"kind":"fallback"}}}
 {"type":"request/header","seq":9,"time":1785730447828,"data":{"header":{"config":{"provider":"deepseek-official","model":"deepseek-v4-flash"},"system":"{{system}}","tools":"{{tools}}"},"reason":"initial"}}
 {"type":"request/context","seq":10,"time":1785730447828,"data":{"provider":"deepseek-official","model":"deepseek-v4-flash"}}

examples/acp-agent/tests/snapshots/subagent-multi/session.2.jsonl

@@ -6,7 +6,7 @@
 {"type":"subagent/descriptor","seq":4,"time":1786357521799,"data":{"version":2,"mode":"one-shot","provider":"spawn","label":"Return BETA only"}}
 {"type":"step/start","seq":5,"time":1786357521801,"data":{"turn":1,"step":1}}
 {"type":"user/message","seq":6,"time":1785730447881,"data":{"content":[{"type":"text","text":"Reply with exactly the word BETA and nothing else."}],"source":{"kind":"user"},"role":"user","id":"53f6419d-8ddc-4eee-8803-5b68411336f9"},"surfaceOp":"append"}
-{"type":"user/message","seq":7,"time":1786357521802,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"92e19923-3254-41fb-8f0f-af86432de7e2"},"surfaceOp":"append"}
+{"type":"user/message","seq":7,"time":1786357521802,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"1cc862ff-09a2-496d-817a-c4281b4540d7"},"surfaceOp":"append"}
 {"type":"session/title","seq":8,"time":1786357521802,"data":{"title":"Reply with exactly the word","messageSeqs":[6],"source":{"kind":"fallback"}}}
 {"type":"request/header","seq":9,"time":1785730447881,"data":{"header":{"config":{"provider":"deepseek-official","model":"deepseek-v4-flash"},"system":"{{system}}","tools":"{{tools}}"},"reason":"initial"}}
 {"type":"request/context","seq":10,"time":1785730447881,"data":{"provider":"deepseek-official","model":"deepseek-v4-flash"}}

examples/acp-agent/tests/snapshots/subagent-parallel/session.1.jsonl

@@ -1,18 +1,18 @@
 {"type":"session","version":0,"id":"bbbbbbbb-0000-4000-8000-000000000002","createdAt":1783352127000,"cwd":"{{cwd}}","parentSession":"aaaaaaaa-0000-4000-8000-000000000001","origin":"subagent","delegationDepth":1}
 {"type":"approval/policy","seq":0,"time":1786373947132,"data":{"policy":"never","source":"delegation"}}
-{"type":"agent/inbox/spliced","seq":1,"time":1786373947134,"data":{"target":"next-turn","start":0,"inserted":[{"content":[{"type":"text","text":"Reply with exactly the word ALPHA and nothing else."}],"source":{"kind":"user"},"role":"user","id":"e706be76-fc34-43dd-bea8-932a44ab7296"}]}}
+{"type":"agent/inbox/spliced","seq":1,"time":1786373947134,"data":{"target":"next-turn","start":0,"inserted":[{"content":[{"type":"text","text":"Reply with exactly the word ALPHA and nothing else."}],"source":{"kind":"user"},"role":"user","id":"fcb407e0-2c85-4875-81cf-ad18fd96e3dc"}]}}
 {"type":"turn/start","seq":2,"time":1786373947134,"data":{"turn":1}}
 {"type":"agent/inbox/spliced","seq":3,"time":1786373947134,"data":{"target":"next-turn","start":0,"removedCount":1,"inserted":[]}}
 {"type":"subagent/descriptor","seq":4,"time":1786373947165,"data":{"version":2,"mode":"one-shot","provider":"spawn","label":"Say the word ALPHA"}}
 {"type":"step/start","seq":5,"time":1786373947168,"data":{"turn":1,"step":1}}
-{"type":"user/message","seq":6,"time":1786338530759,"data":{"content":[{"type":"text","text":"Reply with exactly the word ALPHA and nothing else."}],"source":{"kind":"user"},"role":"user","id":"e706be76-fc34-43dd-bea8-932a44ab7296"},"surfaceOp":"append"}
-{"type":"user/message","seq":7,"time":1786373947168,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"258b6b8c-c0ef-4157-9cf5-77ac13dc9202"},"surfaceOp":"append"}
+{"type":"user/message","seq":6,"time":1786338530759,"data":{"content":[{"type":"text","text":"Reply with exactly the word ALPHA and nothing else."}],"source":{"kind":"user"},"role":"user","id":"fcb407e0-2c85-4875-81cf-ad18fd96e3dc"},"surfaceOp":"append"}
+{"type":"user/message","seq":7,"time":1786373947168,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"43134073-e26c-4314-a019-95f39d40ab19"},"surfaceOp":"append"}
 {"type":"session/title","seq":8,"time":1786373947168,"data":{"title":"Reply with exactly the word","messageSeqs":[6],"source":{"kind":"fallback"}}}
 {"type":"request/header","seq":9,"time":1786338530759,"data":{"header":{"config":{"provider":"deepseek-official","model":"deepseek-v4-flash"},"system":"{{system}}","tools":"{{tools}}"},"reason":"initial"}}
 {"type":"request/context","seq":10,"time":1786338530759,"data":{"provider":"deepseek-official","model":"deepseek-v4-flash"}}
 {"type":"assistant/chunk","seq":11,"time":1786338530769,"data":{"turn":1,"step":1,"chunk":{"type":"block-start","index":0,"blockType":"text"}}}
 {"type":"assistant/chunk","seq":12,"time":1786338530769,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":0,"block":{"type":"text","text":"ALPHA"}}}}
 {"type":"assistant/chunk","seq":13,"time":1786338530769,"data":{"turn":1,"step":1,"chunk":{"type":"finish","reason":{"kind":"stop"}}}}
-{"type":"assistant/message","seq":14,"time":1786338530769,"data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"text","text":"ALPHA"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"237c74c5-2a50-4200-80e4-711e2d8fbd18"}},"sourceEventSeqs":[11,12,13],"surfaceOp":"append"}
+{"type":"assistant/message","seq":14,"time":1786338530769,"data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"text","text":"ALPHA"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"4923daf1-fb8a-4278-b173-477ff3e36df0"}},"sourceEventSeqs":[11,12,13],"surfaceOp":"append"}
 {"type":"step/end","seq":15,"time":1786338530769,"data":{"turn":1,"step":1}}
 {"type":"turn/end","seq":16,"time":1786338530769,"data":{"turn":1,"reason":{"kind":"completed"}}}

examples/acp-agent/tests/snapshots/subagent-parallel/session.2.jsonl

@@ -1,18 +1,18 @@
 {"type":"session","version":0,"id":"cccccccc-0000-4000-8000-000000000003","createdAt":1783352127001,"cwd":"{{cwd}}","parentSession":"aaaaaaaa-0000-4000-8000-000000000001","origin":"subagent","delegationDepth":1}
 {"type":"approval/policy","seq":0,"time":1786373947132,"data":{"policy":"never","source":"delegation"}}
-{"type":"agent/inbox/spliced","seq":1,"time":1786373947133,"data":{"target":"next-turn","start":0,"inserted":[{"content":[{"type":"text","text":"Reply with exactly the word ALPHA and nothing else."}],"source":{"kind":"user"},"role":"user","id":"61226d6c-a359-4cdd-9eab-734557314ce9"}]}}
+{"type":"agent/inbox/spliced","seq":1,"time":1786373947133,"data":{"target":"next-turn","start":0,"inserted":[{"content":[{"type":"text","text":"Reply with exactly the word ALPHA and nothing else."}],"source":{"kind":"user"},"role":"user","id":"f768a0a8-04f9-4dbe-baf0-a55a2be33866"}]}}
 {"type":"turn/start","seq":2,"time":1786373947133,"data":{"turn":1}}
 {"type":"agent/inbox/spliced","seq":3,"time":1786373947134,"data":{"target":"next-turn","start":0,"removedCount":1,"inserted":[]}}
 {"type":"subagent/descriptor","seq":4,"time":1786373947170,"data":{"version":2,"mode":"one-shot","provider":"spawn","label":"Say the word ALPHA"}}
 {"type":"step/start","seq":5,"time":1786373947173,"data":{"turn":1,"step":1}}
-{"type":"user/message","seq":6,"time":1786338530749,"data":{"content":[{"type":"text","text":"Reply with exactly the word ALPHA and nothing else."}],"source":{"kind":"user"},"role":"user","id":"61226d6c-a359-4cdd-9eab-734557314ce9"},"surfaceOp":"append"}
-{"type":"user/message","seq":7,"time":1786373947174,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"cf708e7a-d3c3-477a-91ed-f25605439130"},"surfaceOp":"append"}
+{"type":"user/message","seq":6,"time":1786338530749,"data":{"content":[{"type":"text","text":"Reply with exactly the word ALPHA and nothing else."}],"source":{"kind":"user"},"role":"user","id":"f768a0a8-04f9-4dbe-baf0-a55a2be33866"},"surfaceOp":"append"}
+{"type":"user/message","seq":7,"time":1786373947174,"data":{"content":[{"type":"text","text":"Current runtime context. This snapshot supersedes earlier runtime-context snapshots.\n\nCurrent DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations.\n\nApproval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`).\n\nYou are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt","form":"snapshot","sections":[{"name":"sandbox:policy","text":"Current DSH file policy: danger-full-access. The DSH file sandbox does not restrict file modifications by available operations."},{"name":"approval:policy","text":"Approval prompts are disabled in this session: actions that require approval are rejected automatically — do not request sandbox escalation (do not set `sandbox_permissions`)."},{"name":"subagent:delegation","text":"You are a delegated subagent: your permission scope was fixed when you were started and cannot be widened from inside this session — operations that require approval are rejected automatically. When the task needs access beyond that scope, do not retry the denied operation; state the limitation in your reply so the delegating agent can handle it."}]},"role":"user","id":"2934ee83-26a7-4262-8517-e4fe8f97312a"},"surfaceOp":"append"}
 {"type":"session/title","seq":8,"time":1786373947174,"data":{"title":"Reply with exactly the word","messageSeqs":[6],"source":{"kind":"fallback"}}}
 {"type":"request/header","seq":9,"time":1786338530749,"data":{"header":{"config":{"provider":"deepseek-official","model":"deepseek-v4-flash"},"system":"{{system}}","tools":"{{tools}}"},"reason":"initial"}}
 {"type":"request/context","seq":10,"time":1786338530749,"data":{"provider":"deepseek-official","model":"deepseek-v4-flash"}}
 {"type":"assistant/chunk","seq":11,"time":1786338530759,"data":{"turn":1,"step":1,"chunk":{"type":"block-start","index":0,"blockType":"text"}}}
 {"type":"assistant/chunk","seq":12,"time":1786338530759,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":0,"block":{"type":"text","text":"ALPHA"}}}}
 {"type":"assistant/chunk","seq":13,"time":1786338530759,"data":{"turn":1,"step":1,"chunk":{"type":"finish","reason":{"kind":"stop"}}}}
-{"type":"assistant/message","seq":14,"time":1786338530759,"data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"text","text":"ALPHA"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"ed8a19d2-6095-44db-990c-9f1f9309c824"}},"sourceEventSeqs":[11,12,13],"surfaceOp":"append"}
+{"type":"assistant/message","seq":14,"time":1786338530759,"data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"text","text":"ALPHA"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"013bb4a7-f401-4d39-8552-15232d042d26"}},"sourceEventSeqs":[11,12,13],"surfaceOp":"append"}
 {"type":"step/end","seq":15,"time":1786338530760,"data":{"turn":1,"step":1}}
 {"type":"turn/end","seq":16,"time":1786338530760,"data":{"turn":1,"reason":{"kind":"completed"}}}

examples/acp-agent/tests/snapshots/subagent-report/system-prompt.1.expected.md

@@ -21,6 +21,6 @@ Use the workflow tool ONLY when the user explicitly asks for a workflow or for l
 
 Use the ralph tool ONLY when the direct human explicitly asks for a Ralph loop or fresh-agent iterative execution. Each Ralph round starts a fresh child with no conversation seed and uses the shared workspace as durable memory. Completion and blockers are worker reports, not independent evaluation. Use same-session goal tools for ordinary long-running objectives, and plain subagents or workflows for bounded delegation and fan-out.
 
-Use subagent's continuable background route by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when you cannot take your next action without that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.
+Use subagent in the background by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when your next action depends on that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.
 
 Deliver your result with the report tool before you finish: call it once with a self-contained answer. The agent that started you shares your workspace but does not automatically receive your transcript, tool output, or reasoning, so a closing remark such as "done" leaves it nothing it can use. Report earlier as well whenever a partial finding changes what that agent should do next; reporting never ends your turn.

examples/acp-agent/tests/snapshots/subagent-report/tool-schemas.1.expected.json

@@ -247,7 +247,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool uses its continuable background route by default and immediately returns a durable subagent id. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` to use a foreground run only when you must receive its result before taking your next action.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -261,7 +261,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Whether to use the continuable background route. Defaults to true. Set false to run in the foreground and wait only when your next action depends on its result."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [

examples/acp-agent/tests/snapshots/text-turn/system-prompt.expected.md

@@ -21,4 +21,4 @@ Use the workflow tool ONLY when the user explicitly asks for a workflow or for l
 
 Use the ralph tool ONLY when the direct human explicitly asks for a Ralph loop or fresh-agent iterative execution. Each Ralph round starts a fresh child with no conversation seed and uses the shared workspace as durable memory. Completion and blockers are worker reports, not independent evaluation. Use same-session goal tools for ordinary long-running objectives, and plain subagents or workflows for bounded delegation and fan-out.
 
-Use subagent's continuable background route by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when you cannot take your next action without that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.
+Use subagent in the background by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when your next action depends on that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.

examples/acp-agent/tests/snapshots/text-turn/tool-schemas.expected.json

@@ -231,7 +231,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool uses its continuable background route by default and immediately returns a durable subagent id. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` to use a foreground run only when you must receive its result before taking your next action.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -245,7 +245,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Whether to use the continuable background route. Defaults to true. Set false to run in the foreground and wait only when your next action depends on its result."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [

examples/acp-agent/tests/snapshots/web-fetch/system-prompt.expected.md

@@ -23,4 +23,4 @@ Use the workflow tool ONLY when the user explicitly asks for a workflow or for l
 
 Use the ralph tool ONLY when the direct human explicitly asks for a Ralph loop or fresh-agent iterative execution. Each Ralph round starts a fresh child with no conversation seed and uses the shared workspace as durable memory. Completion and blockers are worker reports, not independent evaluation. Use same-session goal tools for ordinary long-running objectives, and plain subagents or workflows for bounded delegation and fan-out.
 
-Use subagent's continuable background route by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when you cannot take your next action without that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.
+Use subagent in the background by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when your next action depends on that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.

examples/acp-agent/tests/snapshots/web-fetch/tool-schemas.expected.json

@@ -231,7 +231,7 @@
     },
     {
       "name": "subagent",
-      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool uses its continuable background route by default and immediately returns a durable subagent id. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` to use a foreground run only when you must receive its result before taking your next action.",
+      "description": "Delegate a self-contained task to a subagent (a separate agent that works in its own context) to offload focused, independent work — research, a scoped implementation, an analysis — so it does not consume this conversation's context. The subagent returns its result, not its intermediate steps. Give it a complete, standalone prompt: it does not see this conversation. This tool runs in the background by default, immediately returns a durable subagent id, and keeps the child conversation available for later turns. When that run settles, the runtime sends the parent a notice containing its outcome and any final assistant message; `send_message` starts a later turn in the same child conversation. Set `run_in_background: false` only when your next action depends on receiving the result.",
       "parameters": {
         "type": "object",
         "properties": {
@@ -245,7 +245,7 @@
           },
           "run_in_background": {
             "type": "boolean",
-            "description": "Whether to use the continuable background route. Defaults to true. Set false to run in the foreground and wait only when your next action depends on its result."
+            "description": "Whether to run in the background and return a durable subagent id immediately. Defaults to true. Set false to wait for the result when your next action depends on it."
           }
         },
         "required": [

examples/acp-agent/tests/snapshots/workspace-context/system-prompt.expected.md

@@ -21,4 +21,4 @@ Use the workflow tool ONLY when the user explicitly asks for a workflow or for l
 
 Use the ralph tool ONLY when the direct human explicitly asks for a Ralph loop or fresh-agent iterative execution. Each Ralph round starts a fresh child with no conversation seed and uses the shared workspace as durable memory. Completion and blockers are worker reports, not independent evaluation. Use same-session goal tools for ordinary long-running objectives, and plain subagents or workflows for bounded delegation and fan-out.
 
-Use subagent's continuable background route by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when you cannot take your next action without that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.
+Use subagent in the background by default. Start independent delegations together in one assistant message and continue useful work while they run. Set `run_in_background: false` only when your next action depends on that subagent's result. When a background run settles, the runtime sends you a notice containing its outcome and any final assistant message.