fix(subagent): harden continuable persistence

examples/acp-agent/subagent-durability-failure.cordis.snapshot.yml

@@ -0,0 +1,45 @@
+# Keyless counterpart to subagent-durability-failure.cordis.yml: replace the
+# live adapter with replay and fail the provider-owned final child checkpoint.
+- id: base
+  name: '@cordisjs/plugin-include'
+  config:
+    path: ./cordis.yml
+    patches:
+      - id: llm-deepseek
+        name: '@deepseek-ai/dsh-llm-deepseek'
+        disabled: true
+      - id: acp-agent
+        name: '@deepseek-ai/dsh-acp-demo'
+        config:
+          provider: deepseek-official
+          model: deepseek-v4-flash
+          persistenceRoot: !!js process.env.DSH_SNAPSHOT_SESSIONS_ROOT ?? './.sessions'
+          persistenceCompression: none
+          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.
+      - 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'
+      - insert:
+          - id: llm-replay
+            name: '@deepseek-ai/dsh-llm-replay'
+            config:
+              providers:
+                - id: deepseek-official
+                  name: DeepSeek
+                  models:
+                    - id: deepseek-v4-flash
+                    - id: deepseek-v4-pro
+          - id: subagent-durability-failure
+            name: './tests/fixtures/subagent-durability-failure.ts'

examples/acp-agent/subagent-durability-failure.cordis.yml

@@ -0,0 +1,10 @@
+# Snapshot-only durability-failure overlay. The child turn's ordinary flush
+# succeeds; the provider-owned final confirmation fails deterministically.
+- id: base
+  name: '@cordisjs/plugin-include'
+  config:
+    path: ./cordis.yml
+    patches:
+      - insert:
+          - id: subagent-durability-failure
+            name: './tests/fixtures/subagent-durability-failure.ts'

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

@@ -41,6 +41,9 @@ const DEPTH_TWO_CONFIG = fileURLToPath(new URL('../depth-two.cordis.yml', import
 const SESSION_SANDBOX_ROOT_CONFIG = fileURLToPath(new URL('../session-sandbox-root.cordis.yml', import.meta.url))
 const RETRY_CONFIG = fileURLToPath(new URL('../retry.cordis.yml', import.meta.url))
 const SESSION_TITLE_CONFIG = fileURLToPath(new URL('../session-title.cordis.yml', import.meta.url))
+const SUBAGENT_DURABILITY_FAILURE_CONFIG = fileURLToPath(
+  new URL('../subagent-durability-failure.cordis.yml', import.meta.url),
+)
 const LSP_CONFIG = fileURLToPath(new URL('./lsp.cordis.yml', import.meta.url))
 const WEB_CONFIG = fileURLToPath(new URL('../web.cordis.yml', import.meta.url))
 const FS_SEARCH_CONFIG = fileURLToPath(new URL('./fs-search.cordis.yml', import.meta.url))
@@ -214,10 +217,15 @@ const SCENARIOS: Scenario[] = [
   { name: 'subagent-fork', hasModelTurn: true, recorded: true },
   { name: 'subagent-mixed', hasModelTurn: true, recorded: true },
   // Authored continuable-subagent transcript: a background delegation returns
-  // both the durable subagent id and its task id, task_output collects the
-  // child result after settlement, and send_message to an unknown subagent id
-  // starts a follow-up task that settles failed with the id unavailable.
-  { name: 'subagent-continuable', hasModelTurn: true, recorded: false },
+  // both the durable subagent id and its task id, a failed final durability
+  // confirmation reaches task_output with its diagnosis, and send_message to
+  // an unknown subagent id starts a follow-up task that settles unavailable.
+  {
+    name: 'subagent-continuable',
+    hasModelTurn: true,
+    recorded: false,
+    configPath: SUBAGENT_DURABILITY_FAILURE_CONFIG,
+  },
   {
     name: 'subagent-depth-two-rejection',
     hasModelTurn: true,

examples/acp-agent/tests/fixtures/subagent-durability-failure.ts

@@ -0,0 +1,14 @@
+import type { Context } from 'cordis'
+
+export const name = 'subagent-durability-failure'
+
+/** Fail a continuable child's provider-owned final durability confirmation. */
+export function apply(ctx: Context): void {
+  const flushedTurnEnds = new WeakSet<object>()
+  ctx.on('session/flush', (session) => {
+    if (session.header.parentSession === undefined) return
+    if (session.events.at(-1)?.type !== 'turn/end') return
+    if (flushedTurnEnds.has(session)) throw new Error('snapshot disk full')
+    flushedTurnEnds.add(session)
+  })
+}

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

@@ -23,7 +23,7 @@
 {"type":"assistant/chunk","seq":21,"time":1785517567391,"data":{"turn":1,"step":2,"chunk":{"type":"finish","reason":{"kind":"tool-calls"}}}}
 {"type":"assistant/message","seq":22,"time":1785517567392,"data":{"turn":1,"step":2,"message":{"role":"assistant","content":[{"type":"tool-call","id":"call_collect_1","name":"task_output","arguments":"{\"task_id\": \"subagent-1\", \"wait\": true}"}],"source":{"kind":"model","provider":"deepseek-official","model":"deepseek-v4-flash"},"id":"3fcea712-0e14-4f2d-909c-f7de70018053"},"usage":{"inputTokens":10,"outputTokens":5}},"sourceEventSeqs":[17,18,19,20,21],"surfaceOp":"append"}
 {"type":"tool/call","seq":23,"time":1785517567392,"data":{"turn":1,"step":2,"callId":"call_collect_1","name":"task_output","arguments":"{\"task_id\": \"subagent-1\", \"wait\": true}"}}
-{"type":"tool/result","seq":24,"time":1785517567419,"data":{"turn":1,"step":2,"message":{"source":{"kind":"tool","callId":"call_collect_1"},"content":[{"type":"tool-result","toolCallId":"call_collect_1","content":[{"type":"text","text":"CHILD_OK\n[status: completed]"}],"isError":false}],"role":"user","id":"ae79571a-fa78-4de0-9614-a10b5223230c"}},"sourceEventSeqs":[23],"surfaceOp":"append"}
+{"type":"tool/result","seq":24,"time":1785517567419,"data":{"turn":1,"step":2,"message":{"source":{"kind":"tool","callId":"call_collect_1"},"content":[{"type":"tool-result","toolCallId":"call_collect_1","content":[{"type":"text","text":"(no new output)\n[status: failed, subagent \"33333333-3333-4333-8333-333333333333\" durability checkpoint failed; the latest child state was not confirmed persisted and may be unavailable or stale on resume: snapshot disk full]"}],"isError":false}],"role":"user","id":"ae79571a-fa78-4de0-9614-a10b5223230c"}},"sourceEventSeqs":[23],"surfaceOp":"append"}
 {"type":"step/end","seq":25,"time":1785517567419,"data":{"turn":1,"step":2}}
 {"type":"step/start","seq":26,"time":1785517567425,"data":{"turn":1,"step":3}}
 {"type":"assistant/chunk","seq":27,"time":1789000000026,"data":{"turn":1,"step":3,"chunk":{"type":"block-start","index":0,"blockType":"tool-call"}}}