test(snapshot): add the packed-chunks opt-in replay scenario

An overlay pair switches the acp demo's packChunks on; the authored fixture
(text-turn's recording refreshed through that overlay) commits a session.jsonl
whose reasoning run persists as one packed reasoning-chunks row while the
short text run stays verbatim. Keyless replay proves the packed fixture
derives the same model script (fixture reading is layout-blind) and the
re-persisted log packs identically — the transcript surface of the packChunks
switch is now pinned without touching any existing golden.

examples/acp-agent/packed-chunks.cordis.snapshot.yml

@@ -0,0 +1,45 @@
+# Keyless replay counterpart of packed-chunks.cordis.yml. Patches do not
+# compose across includes, so this applies the packChunks config and the
+# DeepSeek-to-replay swap directly to `cordis.yml`.
+- id: base
+  name: '@cordisjs/plugin-include'
+  config:
+    path: ./cordis.yml
+    patches:
+      - id: llm-deepseek
+        name: '@deepseek-ai/dsh-llm-deepseek'
+        disabled: true
+      - id: sandbox
+        name: '@deepseek-ai/dsh-sandbox-local'
+        config:
+          runnerCommand:
+            - bash
+            - -c
+            - while [ "$1" != "--" ]; do shift; done; shift; exec "$@"
+            - passthrough-runner
+          runnerFailureSignatures:
+            - 'passthrough-runner: profile rejected'
+      - id: acp-agent
+        name: '@deepseek-ai/dsh-acp-demo'
+        config:
+          provider: deepseek
+          model: deepseek-v4-flash
+          persistenceRoot: !!js process.env.DSH_SNAPSHOT_SESSIONS_ROOT ?? './.sessions'
+          persistenceCompression: 'none'
+          packChunks: true
+          workspaceContext:
+            maxBytes: 65536
+          persona: |
+            You are a coding assistant powered by the {{model}} model. Your working directory is {{cwd}}. Your bash tool runs under a file sandbox — a `[sandbox: file access denied …]` result is policy, not a command bug.
+
+            Verify your work by running the code or tests. Keep answers brief and factual.
+      - insert:
+          - id: llm-replay
+            name: '@deepseek-ai/dsh-llm-replay'
+            config:
+              providers:
+                - id: deepseek
+                  name: DeepSeek
+                  models:
+                    - id: deepseek-v4-flash
+                    - id: deepseek-v4-pro

examples/acp-agent/packed-chunks.cordis.yml

@@ -0,0 +1,23 @@
+# The packed-chunk-rows overlay: the base tree with the JSONL backend's
+# `packChunks` switched on, so delta-chunk runs persist as packed storage rows.
+# A config patch replaces the whole app config, so unchanged base fields are
+# restated below.
+- id: base
+  name: '@cordisjs/plugin-include'
+  config:
+    path: ./cordis.yml
+    patches:
+      - id: acp-agent
+        name: '@deepseek-ai/dsh-acp-demo'
+        config:
+          provider: deepseek
+          model: deepseek-v4-flash
+          persistenceRoot: !!js process.env.DSH_SNAPSHOT_SESSIONS_ROOT ?? './.sessions'
+          persistenceCompression: !!js "process.env.DSH_SNAPSHOT === undefined ? 'zstd' : 'none'"
+          packChunks: true
+          workspaceContext:
+            maxBytes: 65536
+          persona: |
+            You are a coding assistant powered by the {{model}} model. Your working directory is {{cwd}}. Your bash tool runs under a file sandbox — a `[sandbox: file access denied …]` result is policy, not a command bug.
+
+            Verify your work by running the code or tests. Keep answers brief and factual.

examples/acp-agent/tests/acp.snapshot.ts

@@ -31,6 +31,7 @@ const WORKSPACE_CONTEXT_CONFIG = fileURLToPath(new URL('../workspace-context.cor
 const ADVANCED_CONFIG = fileURLToPath(new URL('../advanced.cordis.yml', import.meta.url))
 const FS_CONFIG = fileURLToPath(new URL('../fs.cordis.yml', import.meta.url))
 const DEPTH_TWO_CONFIG = fileURLToPath(new URL('../depth-two.cordis.yml', import.meta.url))
+const PACKED_CHUNKS_CONFIG = fileURLToPath(new URL('../packed-chunks.cordis.yml', import.meta.url))
 const LSP_CONFIG = fileURLToPath(new URL('./lsp.cordis.yml', import.meta.url))
 
 function snapshotModeFromEnv(value: string | undefined): SnapshotSuiteOptions['mode'] {
@@ -57,6 +58,13 @@ const SCENARIOS: Scenario[] = [
   // Its prompt and tool-schema sidecars pin the composed header.
   { name: 'text-turn', hasModelTurn: true, recorded: true, pinsHeader: true },
   { name: 'tool-call-turn', hasModelTurn: true, recorded: true },
+  // Authored from text-turn's recording: the same single text turn persisted
+  // through the packChunks overlay. The committed session.jsonl carries a
+  // packed `reasoning-chunks` row (the reasoning stream is the ≥3-delta run;
+  // the two text deltas stay verbatim), so replay proves a packed fixture
+  // derives the same model script (reading is layout-blind) and the
+  // re-persisted log packs identically.
+  { name: 'packed-chunks', hasModelTurn: true, recorded: false, configPath: PACKED_CHUNKS_CONFIG },
   // The fs overlay only adds the spill stack (the sandboxed filesystem tools
   // live in the base tree), so these scenarios share the default header class.
   {

examples/acp-agent/tests/snapshots/packed-chunks/input.json

@@ -0,0 +1,7 @@
+{
+  "steps": [
+    { "op": "initialize" },
+    { "op": "newSession" },
+    { "op": "prompt", "text": "Reply with exactly the word: PONG. Do not use any tools." }
+  ]
+}

examples/acp-agent/tests/snapshots/packed-chunks/session.jsonl

@@ -0,0 +1,18 @@
+{"type":"session","version":0,"id":"539aa64c-7f37-40ff-abd8-ed45b717be1b","createdAt":1783600629539,"cwd":"/var/folders/bn/vj1dvck95yd5jh3x4wskflxm0000gn/T/acp-snap-cwd-ka5r8w","delegationDepth":0}
+{"type":"turn/start","seq":0,"time":1783600629541,"data":{"turn":1,"trigger":{"kind":"message","source":{"kind":"user"}}}}
+{"type":"user/message","seq":1,"time":1783600629541,"data":{"content":[{"type":"text","text":"Reply with exactly the word: PONG. Do not use any tools."}],"source":{"kind":"user"}},"surfaceOp":"append"}
+{"type":"session/title","seq":2,"time":1783600629541,"data":{"title":"Reply with exactly the word:","messageSeqs":[1],"source":{"kind":"fallback"}}}
+{"type":"step/start","seq":3,"time":1783600629542,"data":{"turn":1,"step":1}}
+{"type":"request/header","seq":4,"time":1783600629542,"data":{"header":{"config":{"provider":"deepseek","model":"deepseek-v4-flash"},"system":"{{system}}","tools":"{{tools}}"},"reason":"initial"}}
+{"type":"assistant/chunk","seq":5,"time":1783600630819,"data":{"turn":1,"step":1,"chunk":{"type":"block-start","index":0,"blockType":"reasoning"}}}
+{"type":"reasoning-chunks","seq0":6,"time0":1784709770168,"data":{"turn":1,"step":1,"index":0,"dt":[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0],"texts":["The"," user"," wants"," me"," to"," reply"," with"," exactly"," the"," word"," \"","P","ONG","\""," and"," not"," use"," any"," tools","."]}}
+{"type":"assistant/chunk","seq":26,"time":1783600630822,"data":{"turn":1,"step":1,"chunk":{"type":"block-start","index":1,"blockType":"text"}}}
+{"type":"assistant/chunk","seq":27,"time":1783600630852,"data":{"turn":1,"step":1,"chunk":{"type":"text-delta","index":1,"text":"P"}}}
+{"type":"assistant/chunk","seq":28,"time":1783600630852,"data":{"turn":1,"step":1,"chunk":{"type":"text-delta","index":1,"text":"ONG"}}}
+{"type":"assistant/chunk","seq":29,"time":1783600630852,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":0,"block":{"type":"reasoning","text":"The user wants me to reply with exactly the word \"PONG\" and not use any tools."}}}}
+{"type":"assistant/chunk","seq":30,"time":1783600630852,"data":{"turn":1,"step":1,"chunk":{"type":"block-end","index":1,"block":{"type":"text","text":"PONG"}}}}
+{"type":"assistant/chunk","seq":31,"time":1783600630885,"data":{"turn":1,"step":1,"chunk":{"type":"usage","usage":{"inputTokens":3091,"outputTokens":23,"cacheReadTokens":0,"reasoningTokens":20}}}}
+{"type":"assistant/chunk","seq":32,"time":1783600630886,"data":{"turn":1,"step":1,"chunk":{"type":"finish","reason":{"kind":"stop"}}}}
+{"type":"assistant/message","seq":33,"time":1784709770169,"data":{"turn":1,"step":1,"content":[{"type":"reasoning","text":"The user wants me to reply with exactly the word \"PONG\" and not use any tools."},{"type":"text","text":"PONG"}],"provenance":{"provider":"deepseek","model":"deepseek-v4-flash"},"usage":{"inputTokens":3091,"outputTokens":23,"cacheReadTokens":0,"reasoningTokens":20}},"sourceEventSeqs":[5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32],"surfaceOp":"append"}
+{"type":"step/end","seq":34,"time":1784709770170,"data":{"turn":1,"step":1}}
+{"type":"turn/end","seq":35,"time":1784709770170,"data":{"turn":1,"reason":{"kind":"completed"}}}

examples/acp-agent/tests/snapshots/packed-chunks/stdout.expected.jsonl

@@ -0,0 +1,27 @@
+{"jsonrpc":"2.0","id":1,"result":{"protocolVersion":1,"agentInfo":{"name":"deepseek-harness-acp","version":"0.0.1"},"agentCapabilities":{"loadSession":true,"promptCapabilities":{"image":false,"audio":false,"embeddedContext":false}},"authMethods":[]}}
+{"jsonrpc":"2.0","id":2,"result":{"sessionId":"{{sessionId}}","configOptions":[{"id":"model","name":"Model","description":"Sets this session's provider and model.","category":"model","type":"select","currentValue":"[\"deepseek\",\"deepseek-v4-flash\"]","options":[{"value":"[\"deepseek\",\"deepseek-v4-flash\"]","name":"deepseek-v4-flash"},{"value":"[\"deepseek\",\"deepseek-v4-pro\"]","name":"deepseek-v4-pro"}]},{"id":"permission","name":"Permissions","description":"The session permission preset: each choice bundles a sandbox mode and an approval policy.","category":"mode","type":"select","currentValue":"danger-full-access","options":[{"value":"workspace-write","name":"workspace-write","description":"Write inside the workspace and permitted temporary directories; wider retries require approval."},{"value":"danger-full-access","name":"danger-full-access","description":"Full file access without approval prompts."}]}]}}
+{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"{{sessionId}}","update":{"sessionUpdate":"available_commands_update","availableCommands":[{"name":"goal","description":"set or view the goal for a long-running task","input":{"hint":"[<objective>|clear|edit <objective>|pause|resume]"}}]}}}
+{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"{{sessionId}}","update":{"sessionUpdate":"session_info_update","title":"Reply with exactly the word:","updatedAt":"{{updatedAt}}"}}}
+{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"{{sessionId}}","update":{"sessionUpdate":"agent_thought_chunk","content":{"type":"text","text":"The"}}}}
+{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"{{sessionId}}","update":{"sessionUpdate":"agent_thought_chunk","content":{"type":"text","text":" user"}}}}
+{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"{{sessionId}}","update":{"sessionUpdate":"agent_thought_chunk","content":{"type":"text","text":" wants"}}}}
+{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"{{sessionId}}","update":{"sessionUpdate":"agent_thought_chunk","content":{"type":"text","text":" me"}}}}
+{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"{{sessionId}}","update":{"sessionUpdate":"agent_thought_chunk","content":{"type":"text","text":" to"}}}}
+{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"{{sessionId}}","update":{"sessionUpdate":"agent_thought_chunk","content":{"type":"text","text":" reply"}}}}
+{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"{{sessionId}}","update":{"sessionUpdate":"agent_thought_chunk","content":{"type":"text","text":" with"}}}}
+{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"{{sessionId}}","update":{"sessionUpdate":"agent_thought_chunk","content":{"type":"text","text":" exactly"}}}}
+{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"{{sessionId}}","update":{"sessionUpdate":"agent_thought_chunk","content":{"type":"text","text":" the"}}}}
+{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"{{sessionId}}","update":{"sessionUpdate":"agent_thought_chunk","content":{"type":"text","text":" word"}}}}
+{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"{{sessionId}}","update":{"sessionUpdate":"agent_thought_chunk","content":{"type":"text","text":" \""}}}}
+{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"{{sessionId}}","update":{"sessionUpdate":"agent_thought_chunk","content":{"type":"text","text":"P"}}}}
+{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"{{sessionId}}","update":{"sessionUpdate":"agent_thought_chunk","content":{"type":"text","text":"ONG"}}}}
+{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"{{sessionId}}","update":{"sessionUpdate":"agent_thought_chunk","content":{"type":"text","text":"\""}}}}
+{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"{{sessionId}}","update":{"sessionUpdate":"agent_thought_chunk","content":{"type":"text","text":" and"}}}}
+{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"{{sessionId}}","update":{"sessionUpdate":"agent_thought_chunk","content":{"type":"text","text":" not"}}}}
+{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"{{sessionId}}","update":{"sessionUpdate":"agent_thought_chunk","content":{"type":"text","text":" use"}}}}
+{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"{{sessionId}}","update":{"sessionUpdate":"agent_thought_chunk","content":{"type":"text","text":" any"}}}}
+{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"{{sessionId}}","update":{"sessionUpdate":"agent_thought_chunk","content":{"type":"text","text":" tools"}}}}
+{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"{{sessionId}}","update":{"sessionUpdate":"agent_thought_chunk","content":{"type":"text","text":"."}}}}
+{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"{{sessionId}}","update":{"sessionUpdate":"agent_message_chunk","content":{"type":"text","text":"P"}}}}
+{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"{{sessionId}}","update":{"sessionUpdate":"agent_message_chunk","content":{"type":"text","text":"ONG"}}}}
+{"jsonrpc":"2.0","id":3,"result":{"stopReason":"end_turn"}}