diff --git a/snapshots/sdk/multi-turn/writer.expected.jsonl b/snapshots/sdk/multi-turn/writer.expected.jsonl
index 74570d2b3d..acc905fb9c 100644
--- a/snapshots/sdk/multi-turn/writer.expected.jsonl
+++ b/snapshots/sdk/multi-turn/writer.expected.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":4,"id":"{{session:1}}","createdAt":1783352113760,"cwd":"{{cwd}}","isSeeded":false,"delegationDepth":0}
+{"type":"session","version":3,"id":"{{session:1}}","createdAt":1783352113760,"cwd":"{{cwd}}","isSeeded":false,"delegationDepth":0}
 {"type":"permission/preset","data":{"preset":"danger-full-access"}}
 {"type":"sandbox/mode","data":{"mode":"danger-full-access"}}
 {"type":"approval/policy","data":{"policy":"never"}}
@@ -6,13 +6,13 @@
 {"type":"turn/start","data":{"turn":1}}
 {"type":"agent/inbox/spliced","data":{"target":"next-turn","start":0,"removedCount":1,"inserted":[]}}
 {"type":"step/start","data":{"turn":1,"step":1}}
-{"type":"system/message","data":{"turn":1,"step":1,"message":{"role":"system","content":[{"type":"text","text":"{{system}}"}],"source":{"kind":"system-prompt"},"id":"{{message:2}}"}},"surfaceOp":"append"}
+{"type":"system/message","data":{"turn":1,"step":1,"message":{"role":"system","content":[{"type":"text","text":"{{system}}"}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt"},"id":"{{message:2}}"}},"surfaceOp":"append"}
 {"type":"user/message","data":{"content":[{"type":"text","text":"Reply with exactly the word: ONE. No tools."}],"source":{"kind":"user"},"role":"user","id":"{{message:1}}"},"surfaceOp":"append"}
-{"type":"user/message","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`)."}],"source":{"kind":"runtime-context","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`)."}]},"role":"user","id":"{{message:3}}"},"surfaceOp":"append"}
+{"type":"user/message","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`)."}],"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`)."}]},"role":"user","id":"{{message:3}}"},"surfaceOp":"append"}
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 {"type":"request/context","data":{"provider":"deepseek-official","model":"deepseek-v4-flash"}}
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-{"type":"assistant/message","data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"reasoning","text":"The user wants me to reply with exactly the word \"ONE\" and use no tools."},{"type":"text","text":"ONE"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"{{message:4}}"},"usage":{"inputTokens":2864,"outputTokens":20,"cacheReadTokens":0,"reasoningTokens":18},"stream":[{"type":"chunk","time":1789821465760,"chunk":{"type":"block-start","index":0,"blockType":"reasoning"}},{"type":"reasoning-chunks","time0":1789821465760,"index":0,"dt":[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],"texts":["The"," user"," wants"," me"," to"," reply"," with"," exactly"," the"," word"," \"","ONE","\""," and"," use"," no"," tools","."]},{"type":"chunk","time":1789821465760,"chunk":{"type":"block-start","index":1,"blockType":"text"}},{"type":"text-chunks","time0":1789821465760,"index":1,"dt":[],"texts":["ONE"]},{"type":"chunk","time":1789821465760,"chunk":{"type":"block-end","index":0,"block":{"type":"reasoning","text":"The user wants me to reply with exactly the word \"ONE\" and use no tools."}}},{"type":"chunk","time":1789821465760,"chunk":{"type":"block-end","index":1,"block":{"type":"text","text":"ONE"}}},{"type":"chunk","time":1789821465760,"chunk":{"type":"usage","usage":{"inputTokens":2864,"outputTokens":20,"cacheReadTokens":0,"reasoningTokens":18}}},{"type":"chunk","time":1789821465760,"chunk":{"type":"finish","reason":{"kind":"stop"}}}]},"surfaceOp":"append"}
+{"type":"assistant/message","data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"reasoning","text":"The user wants me to reply with exactly the word \"ONE\" and use no tools."},{"type":"text","text":"ONE"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"{{message:4}}"},"usage":{"inputTokens":2864,"outputTokens":20,"cacheReadTokens":0,"reasoningTokens":18},"stream":[{"type":"chunk","time":1788699455946,"chunk":{"type":"block-start","index":0,"blockType":"reasoning"}},{"type":"reasoning-chunks","time0":1788699455946,"index":0,"dt":[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],"texts":["The"," user"," wants"," me"," to"," reply"," with"," exactly"," the"," word"," \"","ONE","\""," and"," use"," no"," tools","."]},{"type":"chunk","time":1788699455946,"chunk":{"type":"block-start","index":1,"blockType":"text"}},{"type":"text-chunks","time0":1788699455946,"index":1,"dt":[],"texts":["ONE"]},{"type":"chunk","time":1788699455946,"chunk":{"type":"block-end","index":0,"block":{"type":"reasoning","text":"The user wants me to reply with exactly the word \"ONE\" and use no tools."}}},{"type":"chunk","time":1788699455946,"chunk":{"type":"block-end","index":1,"block":{"type":"text","text":"ONE"}}},{"type":"chunk","time":1788699455946,"chunk":{"type":"usage","usage":{"inputTokens":2864,"outputTokens":20,"cacheReadTokens":0,"reasoningTokens":18}}},{"type":"chunk","time":1788699455946,"chunk":{"type":"finish","reason":{"kind":"stop"}}}]},"surfaceOp":"append"}
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 {"type":"turn/end","data":{"turn":1,"reason":{"kind":"completed"}}}
 {"type":"agent/inbox/spliced","data":{"target":"next-turn","start":0,"inserted":[{"content":[{"type":"text","text":"Reply with exactly the word: TWO. No tools."}],"source":{"kind":"user"},"role":"user","id":"{{message:5}}"}]}}
@@ -20,6 +20,6 @@
 {"type":"agent/inbox/spliced","data":{"target":"next-turn","start":0,"removedCount":1,"inserted":[]}}
 {"type":"step/start","data":{"turn":2,"step":1}}
 {"type":"user/message","data":{"content":[{"type":"text","text":"Reply with exactly the word: TWO. No tools."}],"source":{"kind":"user"},"role":"user","id":"{{message:5}}"},"surfaceOp":"append"}
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+{"type":"assistant/message","data":{"turn":2,"step":1,"message":{"role":"assistant","content":[{"type":"reasoning","text":"The user wants me to reply with exactly the word \"TWO\" and no tools."},{"type":"text","text":"TWO"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"{{message:6}}"},"usage":{"inputTokens":64,"outputTokens":21,"cacheReadTokens":2816,"reasoningTokens":18},"stream":[{"type":"chunk","time":1788699455964,"chunk":{"type":"block-start","index":0,"blockType":"reasoning"}},{"type":"reasoning-chunks","time0":1788699455964,"index":0,"dt":[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],"texts":["The"," user"," wants"," me"," to"," reply"," with"," exactly"," the"," word"," \"","T","WO","\""," and"," no"," tools","."]},{"type":"chunk","time":1788699455964,"chunk":{"type":"block-start","index":1,"blockType":"text"}},{"type":"text-chunks","time0":1788699455964,"index":1,"dt":[0],"texts":["T","WO"]},{"type":"chunk","time":1788699455964,"chunk":{"type":"block-end","index":0,"block":{"type":"reasoning","text":"The user wants me to reply with exactly the word \"TWO\" and no tools."}}},{"type":"chunk","time":1788699455964,"chunk":{"type":"block-end","index":1,"block":{"type":"text","text":"TWO"}}},{"type":"chunk","time":1788699455964,"chunk":{"type":"usage","usage":{"inputTokens":64,"outputTokens":21,"cacheReadTokens":2816,"reasoningTokens":18}}},{"type":"chunk","time":1788699455964,"chunk":{"type":"finish","reason":{"kind":"stop"}}}]},"surfaceOp":"append"}
 {"type":"step/end","data":{"turn":2,"step":1}}
 {"type":"turn/end","data":{"turn":2,"reason":{"kind":"completed"}}}
diff --git a/snapshots/sdk/persistent-tools/notifications.expected.jsonl b/snapshots/sdk/persistent-tools/notifications.expected.jsonl
index 46c776a3d9..45dd7fabd0 100644
--- a/snapshots/sdk/persistent-tools/notifications.expected.jsonl
+++ b/snapshots/sdk/persistent-tools/notifications.expected.jsonl
@@ -11,37 +11,37 @@
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+{"method":"session.event","params":{"sessionId":"{{sessionId}}","event":{"type":"tool/result","seq":32,"time":0,"data":{"turn":1,"step":5,"message":{"source":{"kind":"tool","callId":"editor-view"},"content":[{"type":"text","text":"Here's the content of {{cwd}}/note.txt with line numbers (which has a total of 3 lines):\n     1  target:\n     2  \told\n     3  \n"}],"role":"tool","toolCallId":"editor-view","isError":false,"id":"{{sessionId}}"}},"sourceEventSeqs":[31],"surfaceOp":"append"}}}
 {"method":"session.event","params":{"sessionId":"{{sessionId}}","event":{"type":"step/end","seq":33,"time":0,"data":{"turn":1,"step":5}}}}
 {"method":"session.event","params":{"sessionId":"{{sessionId}}","event":{"type":"step/start","seq":34,"time":0,"data":{"turn":1,"step":6}}}}
 {"method":"session.event","params":{"sessionId":"{{sessionId}}","event":{"type":"assistant/message","seq":35,"time":0,"data":{"turn":1,"step":6,"message":{"role":"assistant","content":[{"type":"tool-call","id":"editor-replace","name":"str_replace_editor","arguments":"{\"command\":\"str_replace\",\"path\":\"{{cwd}}/note.txt\",\"old_str\":\"\\told\",\"new_str\":\"\\tnew\",\"file_text\":null,\"insert_line\":null,\"view_range\":null}"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"{{sessionId}}"},"usage":{"inputTokens":3,"outputTokens":3},"stream":[{"type":"chunk","time":0,"chunk":{"type":"block-start","index":0,"blockType":"tool-call"}},{"type":"tool-call-chunks","time0":0,"index":0,"dt":[],"id":"editor-replace","name":"str_replace_editor","args":["{\"command\":\"str_replace\",\"path\":\"{{cwd}}/note.txt\",\"old_str\":\"\\told\",\"new_str\":\"\\tnew\",\"file_text\":null,\"insert_line\":null,\"view_range\":null}"]},{"type":"chunk","time":0,"chunk":{"type":"block-end","index":0,"block":{"type":"tool-call","id":"editor-replace","name":"str_replace_editor","arguments":"{\"command\":\"str_replace\",\"path\":\"{{cwd}}/note.txt\",\"old_str\":\"\\told\",\"new_str\":\"\\tnew\",\"file_text\":null,\"insert_line\":null,\"view_range\":null}"}}},{"type":"chunk","time":0,"chunk":{"type":"usage","usage":{"inputTokens":3,"outputTokens":3}}},{"type":"chunk","time":0,"chunk":{"type":"finish","reason":{"kind":"tool-calls"}}}]},"surfaceOp":"append"}}}
 {"method":"session.event","params":{"sessionId":"{{sessionId}}","event":{"type":"tool/call","seq":36,"time":0,"data":{"turn":1,"step":6,"callId":"editor-replace","name":"str_replace_editor","arguments":"{\"command\":\"str_replace\",\"path\":\"{{cwd}}/note.txt\",\"old_str\":\"\\told\",\"new_str\":\"\\tnew\",\"file_text\":null,\"insert_line\":null,\"view_range\":null}"}}}}
-{"method":"session.event","params":{"sessionId":"{{sessionId}}","event":{"type":"tool/result","seq":37,"time":0,"data":{"turn":1,"step":6,"message":{"role":"tool","source":{"kind":"tool","callId":"editor-replace"},"toolCallId":"editor-replace","content":[{"type":"text","text":"The file {{cwd}}/note.txt has been edited successfully."}],"isError":false,"id":"{{sessionId}}"}},"sourceEventSeqs":[36],"surfaceOp":"append"}}}
+{"method":"session.event","params":{"sessionId":"{{sessionId}}","event":{"type":"tool/result","seq":37,"time":0,"data":{"turn":1,"step":6,"message":{"source":{"kind":"tool","callId":"editor-replace"},"content":[{"type":"text","text":"The file {{cwd}}/note.txt has been edited successfully."}],"role":"tool","toolCallId":"editor-replace","isError":false,"id":"{{sessionId}}"}},"sourceEventSeqs":[36],"surfaceOp":"append"}}}
 {"method":"session.event","params":{"sessionId":"{{sessionId}}","event":{"type":"step/end","seq":38,"time":0,"data":{"turn":1,"step":6}}}}
 {"method":"session.event","params":{"sessionId":"{{sessionId}}","event":{"type":"step/start","seq":39,"time":0,"data":{"turn":1,"step":7}}}}
 {"method":"session.event","params":{"sessionId":"{{sessionId}}","event":{"type":"assistant/message","seq":40,"time":0,"data":{"turn":1,"step":7,"message":{"role":"assistant","content":[{"type":"tool-call","id":"bash-exit","name":"bash","arguments":"{\"command\":\"exit 9\"}"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"{{sessionId}}"},"usage":{"inputTokens":3,"outputTokens":3},"stream":[{"type":"chunk","time":0,"chunk":{"type":"block-start","index":0,"blockType":"tool-call"}},{"type":"tool-call-chunks","time0":0,"index":0,"dt":[],"id":"bash-exit","name":"bash","args":["{\"command\":\"exit 9\"}"]},{"type":"chunk","time":0,"chunk":{"type":"block-end","index":0,"block":{"type":"tool-call","id":"bash-exit","name":"bash","arguments":"{\"command\":\"exit 9\"}"}}},{"type":"chunk","time":0,"chunk":{"type":"usage","usage":{"inputTokens":3,"outputTokens":3}}},{"type":"chunk","time":0,"chunk":{"type":"finish","reason":{"kind":"tool-calls"}}}]},"surfaceOp":"append"}}}
 {"method":"session.event","params":{"sessionId":"{{sessionId}}","event":{"type":"tool/call","seq":41,"time":0,"data":{"turn":1,"step":7,"callId":"bash-exit","name":"bash","arguments":"{\"command\":\"exit 9\"}"}}}}
-{"method":"session.event","params":{"sessionId":"{{sessionId}}","event":{"type":"tool/result","seq":42,"time":0,"data":{"turn":1,"step":7,"message":{"role":"tool","source":{"kind":"tool","callId":"bash-exit"},"toolCallId":"bash-exit","content":[{"type":"text","text":"exit\n[shell exited: code 9]\nThe persistent bash shell was reset; the next bash call starts from the workspace with a fresh current directory and environment."}],"isError":false,"id":"{{sessionId}}"}},"sourceEventSeqs":[41],"surfaceOp":"append"}}}
+{"method":"session.event","params":{"sessionId":"{{sessionId}}","event":{"type":"tool/result","seq":42,"time":0,"data":{"turn":1,"step":7,"message":{"source":{"kind":"tool","callId":"bash-exit"},"content":[{"type":"text","text":"exit\n[shell exited: code 9]\nThe persistent bash shell was reset; the next bash call starts from the workspace with a fresh current directory and environment."}],"role":"tool","toolCallId":"bash-exit","isError":false,"id":"{{sessionId}}"}},"sourceEventSeqs":[41],"surfaceOp":"append"}}}
 {"method":"session.event","params":{"sessionId":"{{sessionId}}","event":{"type":"step/end","seq":43,"time":0,"data":{"turn":1,"step":7}}}}
 {"method":"session.event","params":{"sessionId":"{{sessionId}}","event":{"type":"step/start","seq":44,"time":0,"data":{"turn":1,"step":8}}}}
 {"method":"session.event","params":{"sessionId":"{{sessionId}}","event":{"type":"assistant/message","seq":45,"time":0,"data":{"turn":1,"step":8,"message":{"role":"assistant","content":[{"type":"text","text":"PERSISTENT_TOOLS_OK"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"{{sessionId}}"},"usage":{"inputTokens":3,"outputTokens":3},"stream":[{"type":"chunk","time":0,"chunk":{"type":"block-start","index":0,"blockType":"text"}},{"type":"text-chunks","time0":0,"index":0,"dt":[],"texts":["PERSISTENT_TOOLS_OK"]},{"type":"chunk","time":0,"chunk":{"type":"block-end","index":0,"block":{"type":"text","text":"PERSISTENT_TOOLS_OK"}}},{"type":"chunk","time":0,"chunk":{"type":"usage","usage":{"inputTokens":3,"outputTokens":3}}},{"type":"chunk","time":0,"chunk":{"type":"finish","reason":{"kind":"stop"}}}]},"surfaceOp":"append"}}}
diff --git a/snapshots/session/empty-response-retry/writer.expected.jsonl b/snapshots/session/empty-response-retry/writer.expected.jsonl
index f21c382865..941892bdbb 100644
--- a/snapshots/session/empty-response-retry/writer.expected.jsonl
+++ b/snapshots/session/empty-response-retry/writer.expected.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":4,"id":"{{session:1}}","createdAt":0,"cwd":"{{cwd}}","isSeeded":false,"delegationDepth":0}
+{"type":"session","version":3,"id":"{{session:1}}","createdAt":0,"cwd":"{{cwd}}","isSeeded":false,"delegationDepth":0}
 {"type":"permission/preset","data":{"preset":"danger-full-access"}}
 {"type":"sandbox/mode","data":{"mode":"danger-full-access"}}
 {"type":"approval/policy","data":{"policy":"never"}}
@@ -6,15 +6,15 @@
 {"type":"turn/start","data":{"turn":1}}
 {"type":"agent/inbox/spliced","data":{"target":"next-turn","start":0,"removedCount":1,"inserted":[]}}
 {"type":"step/start","data":{"turn":1,"step":1}}
-{"type":"system/message","data":{"turn":1,"step":1,"message":{"role":"system","content":[{"type":"text","text":"{{system}}"}],"source":{"kind":"system-prompt"},"id":"{{message:2}}"}},"surfaceOp":"append"}
+{"type":"system/message","data":{"turn":1,"step":1,"message":{"role":"system","content":[{"type":"text","text":"{{system}}"}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt"},"id":"{{message:2}}"}},"surfaceOp":"append"}
 {"type":"user/message","data":{"content":[{"type":"text","text":"This prompt first receives an empty completion, then a retried reply."}],"source":{"kind":"user"},"role":"user","id":"{{message:1}}"},"surfaceOp":"append"}
-{"type":"user/message","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`)."}],"source":{"kind":"runtime-context","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`)."}]},"role":"user","id":"{{message:3}}"},"surfaceOp":"append"}
+{"type":"user/message","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`)."}],"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`)."}]},"role":"user","id":"{{message:3}}"},"surfaceOp":"append"}
 {"type":"request/header","data":{"header":{"config":{"provider":"deepseek-official","model":"deepseek-v4-flash"},"tools":"{{tools}}"},"reason":"initial"}}
 {"type":"request/context","data":{"provider":"deepseek-official","model":"deepseek-v4-flash"}}
 {"type":"session/title","data":{"title":"This prompt first receives an","messageSeqs":[8],"source":{"kind":"fallback"}}}
-{"type":"assistant/attempt","data":{"turn":1,"step":1,"stream":[{"type":"chunk","time":1789821313609,"chunk":{"type":"usage","usage":{"inputTokens":0,"outputTokens":0}}},{"type":"chunk","time":1789821313609,"chunk":{"type":"finish","reason":{"kind":"error","failure":{"message":"model returned a completed response with no content","code":"EMPTY_RESPONSE"}}}}]}}
+{"type":"assistant/attempt","data":{"turn":1,"step":1,"stream":[{"type":"chunk","time":1788699355641,"chunk":{"type":"usage","usage":{"inputTokens":0,"outputTokens":0}}},{"type":"chunk","time":1788699355642,"chunk":{"type":"finish","reason":{"kind":"error","failure":{"message":"model returned a completed response with no content","code":"EMPTY_RESPONSE"}}}}]}}
 {"type":"llm/retry","data":{"retryId":"{{retry:1}}","turn":1,"step":1,"provider":"deepseek-official","mode":"normal","policyKey":"[\"normal\",2,[\"EMPTY_RESPONSE\",\"RATE_LIMIT\",\"SERVER\",\"TIMEOUT\",\"TRANSPORT\"],1,1,0]","retry":1,"maxRetries":2,"delayMs":1,"failure":{"message":"model returned a completed response with no content","code":"EMPTY_RESPONSE"}}}
 {"type":"llm/retry-started","data":{"retryId":"{{retry:1}}","turn":1,"step":1,"retry":1}}
-{"type":"assistant/message","data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"text","text":"Recovered."}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"{{message:4}}"},"usage":{"inputTokens":12,"outputTokens":3},"stream":[{"type":"chunk","time":1789821313618,"chunk":{"type":"block-start","index":0,"blockType":"text"}},{"type":"text-chunks","time0":1789821313618,"index":0,"dt":[],"texts":["Recovered."]},{"type":"chunk","time":1789821313618,"chunk":{"type":"block-end","index":0,"block":{"type":"text","text":"Recovered."}}},{"type":"chunk","time":1789821313618,"chunk":{"type":"usage","usage":{"inputTokens":12,"outputTokens":3}}},{"type":"chunk","time":1789821313618,"chunk":{"type":"finish","reason":{"kind":"stop"}}}]},"surfaceOp":"append"}
+{"type":"assistant/message","data":{"turn":1,"step":1,"message":{"role":"assistant","content":[{"type":"text","text":"Recovered."}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"{{message:4}}"},"usage":{"inputTokens":12,"outputTokens":3},"stream":[{"type":"chunk","time":1788699355649,"chunk":{"type":"block-start","index":0,"blockType":"text"}},{"type":"text-chunks","time0":1788699355649,"index":0,"dt":[],"texts":["Recovered."]},{"type":"chunk","time":1788699355649,"chunk":{"type":"block-end","index":0,"block":{"type":"text","text":"Recovered."}}},{"type":"chunk","time":1788699355649,"chunk":{"type":"usage","usage":{"inputTokens":12,"outputTokens":3}}},{"type":"chunk","time":1788699355649,"chunk":{"type":"finish","reason":{"kind":"stop"}}}]},"surfaceOp":"append"}
 {"type":"step/end","data":{"turn":1,"step":1}}
 {"type":"turn/end","data":{"turn":1,"reason":{"kind":"completed"}}}
diff --git a/snapshots/session/error-finish/writer.expected.jsonl b/snapshots/session/error-finish/writer.expected.jsonl
index 818b2c6cfa..21eac6615b 100644
--- a/snapshots/session/error-finish/writer.expected.jsonl
+++ b/snapshots/session/error-finish/writer.expected.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":4,"id":"{{session:1}}","createdAt":0,"cwd":"{{cwd}}","isSeeded":false,"delegationDepth":0}
+{"type":"session","version":3,"id":"{{session:1}}","createdAt":0,"cwd":"{{cwd}}","isSeeded":false,"delegationDepth":0}
 {"type":"permission/preset","data":{"preset":"danger-full-access"}}
 {"type":"sandbox/mode","data":{"mode":"danger-full-access"}}
 {"type":"approval/policy","data":{"policy":"never"}}
@@ -6,12 +6,12 @@
 {"type":"turn/start","data":{"turn":1}}
 {"type":"agent/inbox/spliced","data":{"target":"next-turn","start":0,"removedCount":1,"inserted":[]}}
 {"type":"step/start","data":{"turn":1,"step":1}}
-{"type":"system/message","data":{"turn":1,"step":1,"message":{"role":"system","content":[{"type":"text","text":"{{system}}"}],"source":{"kind":"system-prompt"},"id":"{{message:2}}"}},"surfaceOp":"append"}
+{"type":"system/message","data":{"turn":1,"step":1,"message":{"role":"system","content":[{"type":"text","text":"{{system}}"}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt"},"id":"{{message:2}}"}},"surfaceOp":"append"}
 {"type":"user/message","data":{"content":[{"type":"text","text":"This prompt triggers a recorded provider error."}],"source":{"kind":"user"},"role":"user","id":"{{message:1}}"},"surfaceOp":"append"}
-{"type":"user/message","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`)."}],"source":{"kind":"runtime-context","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`)."}]},"role":"user","id":"{{message:3}}"},"surfaceOp":"append"}
+{"type":"user/message","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`)."}],"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`)."}]},"role":"user","id":"{{message:3}}"},"surfaceOp":"append"}
 {"type":"request/header","data":{"header":{"config":{"provider":"deepseek-official","model":"deepseek-v4-flash"},"tools":"{{tools}}"},"reason":"initial"}}
 {"type":"request/context","data":{"provider":"deepseek-official","model":"deepseek-v4-flash"}}
 {"type":"session/title","data":{"title":"This prompt triggers a recorded","messageSeqs":[8],"source":{"kind":"fallback"}}}
-{"type":"assistant/attempt","data":{"turn":1,"step":1,"stream":[{"type":"chunk","time":1789821316465,"chunk":{"type":"finish","reason":{"kind":"error","failure":{"message":"simulated provider error (HTTP 401)","code":"AUTH"}}}}]}}
+{"type":"assistant/attempt","data":{"turn":1,"step":1,"stream":[{"type":"chunk","time":1788699358252,"chunk":{"type":"finish","reason":{"kind":"error","failure":{"message":"simulated provider error (HTTP 401)","code":"AUTH"}}}}]}}
 {"type":"step/end","data":{"turn":1,"step":1}}
 {"type":"turn/end","data":{"turn":1,"reason":{"kind":"error","error":{"message":"simulated provider error (HTTP 401)","code":"AUTH"}}}}
diff --git a/snapshots/session/packed-chunks/writer.expected.jsonl b/snapshots/session/packed-chunks/writer.expected.jsonl
index b5ab3ef3c2..b81400cdf4 100644
--- a/snapshots/session/packed-chunks/writer.expected.jsonl
+++ b/snapshots/session/packed-chunks/writer.expected.jsonl
@@ -1,4 +1,4 @@
-{"type":"session","version":4,"id":"{{session:1}}","createdAt":1783352165190,"cwd":"{{cwd}}","isSeeded":false,"delegationDepth":0}
+{"type":"session","version":3,"id":"{{session:1}}","createdAt":1783352165190,"cwd":"{{cwd}}","isSeeded":false,"delegationDepth":0}
 {"type":"permission/preset","data":{"preset":"danger-full-access"}}
 {"type":"sandbox/mode","data":{"mode":"danger-full-access"}}
 {"type":"approval/policy","data":{"policy":"never"}}
@@ -6,19 +6,19 @@
 {"type":"turn/start","data":{"turn":1}}
 {"type":"agent/inbox/spliced","data":{"target":"next-turn","start":0,"removedCount":1,"inserted":[]}}
 {"type":"step/start","data":{"turn":1,"step":1}}
-{"type":"system/message","data":{"turn":1,"step":1,"message":{"role":"system","content":[{"type":"text","text":"{{system}}"}],"source":{"kind":"system-prompt"},"id":"{{message:2}}"}},"surfaceOp":"append"}
+{"type":"system/message","data":{"turn":1,"step":1,"message":{"role":"system","content":[{"type":"text","text":"{{system}}"}],"source":{"kind":"plugin","plugin":"@deepseek-ai/dsh-system-prompt"},"id":"{{message:2}}"}},"surfaceOp":"append"}
 {"type":"user/message","data":{"content":[{"type":"text","text":"Use the bash tool to run exactly: echo HELLO. Report the tool result you got back verbatim, then stop."}],"source":{"kind":"user"},"role":"user","id":"{{message:1}}"},"surfaceOp":"append"}
-{"type":"user/message","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`)."}],"source":{"kind":"runtime-context","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`)."}]},"role":"user","id":"{{message:3}}"},"surfaceOp":"append"}
+{"type":"user/message","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`)."}],"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`)."}]},"role":"user","id":"{{message:3}}"},"surfaceOp":"append"}
 {"type":"request/header","data":{"header":{"config":{"provider":"deepseek-official","model":"deepseek-v4-flash"},"tools":"{{tools}}"},"reason":"initial"}}
 {"type":"request/context","data":{"provider":"deepseek-official","model":"deepseek-v4-flash"}}
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diff --git a/snapshots/session/text-turn/writer.expected.jsonl b/snapshots/session/text-turn/writer.expected.jsonl
index b59dd14bf1..5b0e3fcb7e 100644
--- a/snapshots/session/text-turn/writer.expected.jsonl
+++ b/snapshots/session/text-turn/writer.expected.jsonl
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