ignore: v2 experiments

11 files changed, 1306 insertions, 120 deletions

diff --git a/.opencode/.gitignore b/.opencode/.gitignore
index d3bf7f8d3..c072cfe07 100644
--- a/.opencode/.gitignore
+++ b/.opencode/.gitignore
@@ -3,4 +3,5 @@ plans
 package.json
 bun.lock
 .gitignore
-package-lock.json
\ No newline at end of file
+package-lock.json
+references/
diff --git a/.opencode/skills/effect/SKILL.md b/.opencode/skills/effect/SKILL.md
new file mode 100644
index 000000000..475814637
--- /dev/null
+++ b/.opencode/skills/effect/SKILL.md
@@ -0,0 +1,21 @@
+---
+name: effect
+description: Answer questions about the Effect framework
+---
+
+# Effect
+
+This codebase uses Effect, a framework for writing typescript.
+
+## How to Answer Effect Questions
+
+1. Clone the Effect repository: `https://github.com/Effect-TS/effect-smol` to
+   `.opencode/references/effect-smol` in this project NOT the skill folder.
+2. Use the explore agent to search the codebase for answers about Effect patterns, APIs, and concepts
+3. Provide responses based on the actual Effect source code and documentation
+
+## Guidelines
+
+- Always use the explore agent with the cloned repository when answering Effect-related questions
+- Reference specific files and patterns found in the Effect codebase
+- Do not answer from memory - always verify against the source
diff --git a/bun.lock b/bun.lock
index 2a73798c9..8fb3362e2 100644
--- a/bun.lock
+++ b/bun.lock
@@ -386,6 +386,7 @@
         "hono": "catalog:",
         "hono-openapi": "catalog:",
         "ignore": "7.0.5",
+        "immer": "11.1.4",
         "jsonc-parser": "3.3.1",
         "mime-types": "3.0.2",
         "minimatch": "10.0.3",
@@ -3336,6 +3337,8 @@
 
     "image-q": ["[email protected]", "", { "dependencies": { "@types/node": "16.9.1" } }, "sha512-PfJGVgIfKQJuq3s0tTDOKtztksibuUEbJQIYT3by6wctQo+Rdlh7ef4evJ5NCdxY4CfMbvFkocEwbl4BF8RlJw=="],
 
+    "immer": ["[email protected]", "", {}, "sha512-XREFCPo6ksxVzP4E0ekD5aMdf8WMwmdNaz6vuvxgI40UaEiu6q3p8X52aU6GdyvLY3XXX/8R7JOTXStz/nBbRw=="],
+
     "import-local": ["[email protected]", "", { "dependencies": { "pkg-dir": "^4.2.0", "resolve-cwd": "^3.0.0" }, "bin": { "import-local-fixture": "fixtures/cli.js" } }, "sha512-2SPlun1JUPWoM6t3F0dw0FkCF/jWY8kttcY4f599GLTSjh2OCuuhdTkJQsEcZzBqbXZGKMK2OqW1oZsjtf/gQA=="],
 
     "import-meta-resolve": ["[email protected]", "", {}, "sha512-Iqv2fzaTQN28s/FwZAoFq0ZSs/7hMAHJVX+w8PZl3cY19Pxk6jFFalxQoIfW2826i/fDLXv8IiEZRIT0lDuWcg=="],
diff --git a/packages/opencode/package.json b/packages/opencode/package.json
index 19c600f56..beb77d75f 100644
--- a/packages/opencode/package.json
+++ b/packages/opencode/package.json
@@ -143,6 +143,7 @@
     "hono": "catalog:",
     "hono-openapi": "catalog:",
     "ignore": "7.0.5",
+    "immer": "11.1.4",
     "jsonc-parser": "3.3.1",
     "mime-types": "3.0.2",
     "minimatch": "10.0.3",
diff --git a/packages/opencode/src/id/id.ts b/packages/opencode/src/id/id.ts
index d86b99250..3d4cddf53 100644
--- a/packages/opencode/src/id/id.ts
+++ b/packages/opencode/src/id/id.ts
@@ -27,16 +27,16 @@ export namespace Identifier {
   let counter = 0
 
   export function ascending(prefix: keyof typeof prefixes, given?: string) {
-    return generateID(prefix, false, given)
+    return generateID(prefix, "ascending", given)
   }
 
   export function descending(prefix: keyof typeof prefixes, given?: string) {
-    return generateID(prefix, true, given)
+    return generateID(prefix, "descending", given)
   }
 
-  function generateID(prefix: keyof typeof prefixes, descending: boolean, given?: string): string {
+  function generateID(prefix: keyof typeof prefixes, direction: "descending" | "ascending", given?: string): string {
     if (!given) {
-      return create(prefix, descending)
+      return create(prefixes[prefix], direction)
     }
 
     if (!given.startsWith(prefixes[prefix])) {
@@ -55,7 +55,7 @@ export namespace Identifier {
     return result
   }
 
-  export function create(prefix: keyof typeof prefixes, descending: boolean, timestamp?: number): string {
+  export function create(prefix: string, direction: "descending" | "ascending", timestamp?: number): string {
     const currentTimestamp = timestamp ?? Date.now()
 
     if (currentTimestamp !== lastTimestamp) {
@@ -66,14 +66,14 @@ export namespace Identifier {
 
     let now = BigInt(currentTimestamp) * BigInt(0x1000) + BigInt(counter)
 
-    now = descending ? ~now : now
+    now = direction === "descending" ? ~now : now
 
     const timeBytes = Buffer.alloc(6)
     for (let i = 0; i < 6; i++) {
       timeBytes[i] = Number((now >> BigInt(40 - 8 * i)) & BigInt(0xff))
     }
 
-    return prefixes[prefix] + "_" + timeBytes.toString("hex") + randomBase62(LENGTH - 12)
+    return prefix + "_" + timeBytes.toString("hex") + randomBase62(LENGTH - 12)
   }
 
   /** Extract timestamp from an ascending ID. Does not work with descending IDs. */
diff --git a/packages/opencode/src/tool/truncate.ts b/packages/opencode/src/tool/truncate.ts
index fa9e0bcab..e6bab1a16 100644
--- a/packages/opencode/src/tool/truncate.ts
+++ b/packages/opencode/src/tool/truncate.ts
@@ -48,7 +48,9 @@ export namespace Truncate {
       const fs = yield* AppFileSystem.Service
 
       const cleanup = Effect.fn("Truncate.cleanup")(function* () {
-        const cutoff = Identifier.timestamp(Identifier.create("tool", false, Date.now() - Duration.toMillis(RETENTION)))
+        const cutoff = Identifier.timestamp(
+          Identifier.create("tool", "ascending", Date.now() - Duration.toMillis(RETENTION)),
+        )
         const entries = yield* fs.readDirectory(TRUNCATION_DIR).pipe(
           Effect.map((all) => all.filter((name) => name.startsWith("tool_"))),
           Effect.catch(() => Effect.succeed([])),
diff --git a/packages/opencode/src/v2/session-common.ts b/packages/opencode/src/v2/session-common.ts
new file mode 100644
index 000000000..556bd79b6
--- /dev/null
+++ b/packages/opencode/src/v2/session-common.ts
@@ -0,0 +1 @@
+export namespace SessionCommon {}
diff --git a/packages/opencode/src/v2/session-entry.ts b/packages/opencode/src/v2/session-entry.ts
index 03c8a85b0..a60d8c6c7 100644
--- a/packages/opencode/src/v2/session-entry.ts
+++ b/packages/opencode/src/v2/session-entry.ts
@@ -1,114 +1,51 @@
-import { Identifier } from "@/id/id"
-import { Database } from "@/node"
-import type { SessionID } from "@/session/schema"
-import { SessionEntryTable } from "@/session/session.sql"
-import { withStatics } from "@/util/schema"
-import { Context, DateTime, Effect, Layer, Schema } from "effect"
-import { eq } from "../storage/db"
+import { Schema } from "effect"
+import { SessionEvent } from "./session-event"
+import { produce } from "immer"
 
 export namespace SessionEntry {
-  export const ID = Schema.String.pipe(Schema.brand("Session.Entry.ID")).pipe(
-    withStatics((s) => ({
-      create: () => s.make(Identifier.ascending("entry")),
-      prefix: "ent",
-    })),
-  )
+  export const ID = SessionEvent.ID
   export type ID = Schema.Schema.Type<typeof ID>
 
   const Base = {
-    id: ID,
+    id: SessionEvent.ID,
     metadata: Schema.Record(Schema.String, Schema.Unknown).pipe(Schema.optional),
     time: Schema.Struct({
       created: Schema.DateTimeUtc,
     }),
   }
 
-  export class Source extends Schema.Class<Source>("Session.Entry.Source")({
-    start: Schema.Number,
-    end: Schema.Number,
-    text: Schema.String,
-  }) {}
-
-  export class FileAttachment extends Schema.Class<FileAttachment>("Session.Entry.File.Attachment")({
-    uri: Schema.String,
-    mime: Schema.String,
-    name: Schema.String.pipe(Schema.optional),
-    description: Schema.String.pipe(Schema.optional),
-    source: Source.pipe(Schema.optional),
-  }) {
-    static create(url: string) {
-      return new FileAttachment({
-        uri: url,
-        mime: "text/plain",
-      })
-    }
-  }
-
-  export class AgentAttachment extends Schema.Class<AgentAttachment>("Session.Entry.Agent.Attachment")({
-    name: Schema.String,
-    source: Source.pipe(Schema.optional),
-  }) {}
-
   export class User extends Schema.Class<User>("Session.Entry.User")({
     ...Base,
+    text: SessionEvent.Prompt.fields.text,
+    files: SessionEvent.Prompt.fields.files,
+    agents: SessionEvent.Prompt.fields.agents,
     type: Schema.Literal("user"),
-    text: Schema.String,
-    files: Schema.Array(FileAttachment).pipe(Schema.optional),
-    agents: Schema.Array(AgentAttachment).pipe(Schema.optional),
+    time: Schema.Struct({
+      created: Schema.DateTimeUtc,
+    }),
   }) {
-    static create(input: { text: User["text"]; files?: User["files"]; agents?: User["agents"] }) {
-      const msg = new User({
-        id: ID.create(),
+    static fromEvent(event: SessionEvent.Prompt) {
+      return new User({
+        id: event.id,
         type: "user",
-        ...input,
-        time: {
-          created: Effect.runSync(DateTime.now),
-        },
+        metadata: event.metadata,
+        text: event.text,
+        files: event.files,
+        agents: event.agents,
+        time: { created: event.timestamp },
       })
-      return msg
     }
   }
 
   export class Synthetic extends Schema.Class<Synthetic>("Session.Entry.Synthetic")({
+    ...SessionEvent.Synthetic.fields,
     ...Base,
     type: Schema.Literal("synthetic"),
-    text: Schema.String,
-  }) {}
-
-  export class Request extends Schema.Class<Request>("Session.Entry.Request")({
-    ...Base,
-    type: Schema.Literal("start"),
-    model: Schema.Struct({
-      id: Schema.String,
-      providerID: Schema.String,
-      variant: Schema.String.pipe(Schema.optional),
-    }),
-  }) {}
-
-  export class Text extends Schema.Class<Text>("Session.Entry.Text")({
-    ...Base,
-    type: Schema.Literal("text"),
-    text: Schema.String,
-    time: Schema.Struct({
-      ...Base.time.fields,
-      completed: Schema.DateTimeUtc.pipe(Schema.optional),
-    }),
-  }) {}
-
-  export class Reasoning extends Schema.Class<Reasoning>("Session.Entry.Reasoning")({
-    ...Base,
-    type: Schema.Literal("reasoning"),
-    text: Schema.String,
-    time: Schema.Struct({
-      ...Base.time.fields,
-      completed: Schema.DateTimeUtc.pipe(Schema.optional),
-    }),
   }) {}
 
   export class ToolStatePending extends Schema.Class<ToolStatePending>("Session.Entry.ToolState.Pending")({
     status: Schema.Literal("pending"),
-    input: Schema.Record(Schema.String, Schema.Unknown),
-    raw: Schema.String,
+    input: Schema.String,
   }) {}
 
   export class ToolStateRunning extends Schema.Class<ToolStateRunning>("Session.Entry.ToolState.Running")({
@@ -124,7 +61,7 @@ export namespace SessionEntry {
     output: Schema.String,
     title: Schema.String,
     metadata: Schema.Record(Schema.String, Schema.Unknown),
-    attachments: Schema.Array(FileAttachment).pipe(Schema.optional),
+    attachments: SessionEvent.FileAttachment.pipe(Schema.Array, Schema.optional),
   }) {}
 
   export class ToolStateError extends Schema.Class<ToolStateError>("Session.Entry.ToolState.Error")({
@@ -132,34 +69,42 @@ export namespace SessionEntry {
     input: Schema.Record(Schema.String, Schema.Unknown),
     error: Schema.String,
     metadata: Schema.Record(Schema.String, Schema.Unknown).pipe(Schema.optional),
-    time: Schema.Struct({
-      start: Schema.Number,
-      end: Schema.Number,
-    }),
   }) {}
 
   export const ToolState = Schema.Union([ToolStatePending, ToolStateRunning, ToolStateCompleted, ToolStateError])
   export type ToolState = Schema.Schema.Type<typeof ToolState>
 
-  export class Tool extends Schema.Class<Tool>("Session.Entry.Tool")({
-    ...Base,
+  export class AssistantTool extends Schema.Class<AssistantTool>("Session.Entry.Assistant.Tool")({
     type: Schema.Literal("tool"),
     callID: Schema.String,
     name: Schema.String,
     state: ToolState,
     time: Schema.Struct({
-      ...Base.time.fields,
+      created: Schema.DateTimeUtc,
       ran: Schema.DateTimeUtc.pipe(Schema.optional),
       completed: Schema.DateTimeUtc.pipe(Schema.optional),
       pruned: Schema.DateTimeUtc.pipe(Schema.optional),
     }),
   }) {}
 
-  export class Complete extends Schema.Class<Complete>("Session.Entry.Complete")({
+  export class AssistantText extends Schema.Class<AssistantText>("Session.Entry.Assistant.Text")({
+    type: Schema.Literal("text"),
+    text: Schema.String,
+  }) {}
+
+  export class AssistantReasoning extends Schema.Class<AssistantReasoning>("Session.Entry.Assistant.Reasoning")({
+    type: Schema.Literal("reasoning"),
+    text: Schema.String,
+  }) {}
+
+  export const AssistantContent = Schema.Union([AssistantText, AssistantReasoning, AssistantTool])
+  export type AssistantContent = Schema.Schema.Type<typeof AssistantContent>
+
+  export class Assistant extends Schema.Class<Assistant>("Session.Entry.Assistant")({
     ...Base,
-    type: Schema.Literal("complete"),
-    cost: Schema.Number,
-    reason: Schema.String,
+    type: Schema.Literal("assistant"),
+    content: AssistantContent.pipe(Schema.Array),
+    cost: Schema.Number.pipe(Schema.optional),
     tokens: Schema.Struct({
       input: Schema.Number,
       output: Schema.Number,
@@ -168,30 +113,174 @@ export namespace SessionEntry {
         read: Schema.Number,
         write: Schema.Number,
       }),
+    }).pipe(Schema.optional),
+    error: Schema.String.pipe(Schema.optional),
+    time: Schema.Struct({
+      created: Schema.DateTimeUtc,
+      completed: Schema.DateTimeUtc.pipe(Schema.optional),
     }),
   }) {}
 
-  export class Retry extends Schema.Class<Retry>("Session.Entry.Retry")({
-    ...Base,
-    type: Schema.Literal("retry"),
-    attempt: Schema.Number,
-    error: Schema.String,
-  }) {}
-
   export class Compaction extends Schema.Class<Compaction>("Session.Entry.Compaction")({
-    ...Base,
+    ...SessionEvent.Compacted.fields,
     type: Schema.Literal("compaction"),
-    auto: Schema.Boolean,
-    overflow: Schema.Boolean.pipe(Schema.optional),
+    ...Base,
   }) {}
 
-  export const Entry = Schema.Union([User, Synthetic, Request, Tool, Text, Reasoning, Complete, Retry, Compaction], {
-    mode: "oneOf",
-  })
+  export const Entry = Schema.Union([User, Synthetic, Assistant, Compaction])
+
   export type Entry = Schema.Schema.Type<typeof Entry>
 
   export type Type = Entry["type"]
 
+  export type History = {
+    entries: Entry[]
+    pending: Entry[]
+  }
+
+  export function step(old: History, event: SessionEvent.Event): History {
+    return produce(old, (draft) => {
+      const lastAssistant = draft.entries.findLast((x) => x.type === "assistant")
+      const pendingAssistant = lastAssistant && !lastAssistant.time.completed ? lastAssistant : undefined
+
+      switch (event.type) {
+        case "prompt": {
+          if (pendingAssistant) {
+            // @ts-expect-error
+            draft.pending.push(User.fromEvent(event))
+            break
+          }
+          // @ts-expect-error
+          draft.entries.push(User.fromEvent(event))
+          break
+        }
+        case "step.started": {
+          if (pendingAssistant) pendingAssistant.time.completed = event.timestamp
+          draft.entries.push({
+            id: event.id,
+            type: "assistant",
+            time: {
+              created: event.timestamp,
+            },
+            content: [],
+          })
+          break
+        }
+        case "text.started": {
+          if (!pendingAssistant) break
+          pendingAssistant.content.push({
+            type: "text",
+            text: "",
+          })
+          break
+        }
+        case "text.delta": {
+          if (!pendingAssistant) break
+          const match = pendingAssistant.content.findLast((x) => x.type === "text")
+          if (match) match.text += event.delta
+          break
+        }
+        case "text.ended": {
+          break
+        }
+        case "tool.input.started": {
+          if (!pendingAssistant) break
+          pendingAssistant.content.push({
+            type: "tool",
+            callID: event.callID,
+            name: event.name,
+            time: {
+              created: event.timestamp,
+            },
+            state: {
+              status: "pending",
+              input: "",
+            },
+          })
+          break
+        }
+        case "tool.input.delta": {
+          if (!pendingAssistant) break
+          const match = pendingAssistant.content.findLast((x) => x.type === "tool")
+          if (match) match.state.input += event.delta
+          break
+        }
+        case "tool.input.ended": {
+          break
+        }
+        case "tool.called": {
+          if (!pendingAssistant) break
+          const match = pendingAssistant.content.findLast((x) => x.type === "tool")
+          if (match) {
+            match.time.ran = event.timestamp
+            match.state = {
+              status: "running",
+              input: event.input,
+            }
+          }
+          break
+        }
+        case "tool.success": {
+          if (!pendingAssistant) break
+          const match = pendingAssistant.content.findLast((x) => x.type === "tool")
+          if (match && match.state.status === "running") {
+            match.state = {
+              status: "completed",
+              input: match.state.input,
+              output: event.output ?? "",
+              title: event.title,
+              metadata: event.metadata ?? {},
+              // @ts-expect-error
+              attachments: event.attachments ?? [],
+            }
+          }
+          break
+        }
+        case "tool.error": {
+          if (!pendingAssistant) break
+          const match = pendingAssistant.content.findLast((x) => x.type === "tool")
+          if (match && match.state.status === "running") {
+            match.state = {
+              status: "error",
+              error: event.error,
+              input: match.state.input,
+              metadata: event.metadata ?? {},
+            }
+          }
+          break
+        }
+        case "reasoning.started": {
+          if (!pendingAssistant) break
+          pendingAssistant.content.push({
+            type: "reasoning",
+            text: "",
+          })
+          break
+        }
+        case "reasoning.delta": {
+          if (!pendingAssistant) break
+          const match = pendingAssistant.content.findLast((x) => x.type === "reasoning")
+          if (match) match.text += event.delta
+          break
+        }
+        case "reasoning.ended": {
+          if (!pendingAssistant) break
+          const match = pendingAssistant.content.findLast((x) => x.type === "reasoning")
+          if (match) match.text = event.text
+          break
+        }
+        case "step.ended": {
+          if (!pendingAssistant) break
+          pendingAssistant.time.completed = event.timestamp
+          pendingAssistant.cost = event.cost
+          pendingAssistant.tokens = event.tokens
+          break
+        }
+      }
+    })
+  }
+
+  /*
   export interface Interface {
     readonly decode: (row: typeof SessionEntryTable.$inferSelect) => Entry
     readonly fromSession: (sessionID: SessionID) => Effect.Effect<Entry[], never>
@@ -224,4 +313,5 @@ export namespace SessionEntry {
       })
     }),
   )
+  */
 }
diff --git a/packages/opencode/src/v2/session-event.ts b/packages/opencode/src/v2/session-event.ts
new file mode 100644
index 000000000..f662f05e7
--- /dev/null
+++ b/packages/opencode/src/v2/session-event.ts
@@ -0,0 +1,443 @@
+import { Identifier } from "@/id/id"
+import { withStatics } from "@/util/schema"
+import * as DateTime from "effect/DateTime"
+import { Schema } from "effect"
+
+export namespace SessionEvent {
+  export const ID = Schema.String.pipe(
+    Schema.brand("Session.Event.ID"),
+    withStatics((s) => ({
+      create: () => s.make(Identifier.create("evt", "ascending")),
+    })),
+  )
+  export type ID = Schema.Schema.Type<typeof ID>
+  type Stamp = Schema.Schema.Type<typeof Schema.DateTimeUtc>
+  type BaseInput = {
+    id?: ID
+    metadata?: Record<string, unknown>
+    timestamp?: Stamp
+  }
+
+  const Base = {
+    id: ID,
+    metadata: Schema.Record(Schema.String, Schema.Unknown).pipe(Schema.optional),
+    timestamp: Schema.DateTimeUtc,
+  }
+
+  export class Source extends Schema.Class<Source>("Session.Event.Source")({
+    start: Schema.Number,
+    end: Schema.Number,
+    text: Schema.String,
+  }) {}
+
+  export class FileAttachment extends Schema.Class<FileAttachment>("Session.Event.FileAttachment")({
+    uri: Schema.String,
+    mime: Schema.String,
+    name: Schema.String.pipe(Schema.optional),
+    description: Schema.String.pipe(Schema.optional),
+    source: Source.pipe(Schema.optional),
+  }) {
+    static create(input: FileAttachment) {
+      return new FileAttachment({
+        ...input,
+      })
+    }
+  }
+
+  export class AgentAttachment extends Schema.Class<AgentAttachment>("Session.Event.AgentAttachment")({
+    name: Schema.String,
+    source: Source.pipe(Schema.optional),
+  }) {}
+
+  export class Prompt extends Schema.Class<Prompt>("Session.Event.Prompt")({
+    ...Base,
+    type: Schema.Literal("prompt"),
+    text: Schema.String,
+    files: Schema.Array(FileAttachment).pipe(Schema.optional),
+    agents: Schema.Array(AgentAttachment).pipe(Schema.optional),
+  }) {
+    static create(input: BaseInput & { text: string; files?: FileAttachment[]; agents?: AgentAttachment[] }) {
+      return new Prompt({
+        id: input.id ?? ID.create(),
+        type: "prompt",
+        timestamp: input.timestamp ?? DateTime.makeUnsafe(Date.now()),
+        metadata: input.metadata,
+        text: input.text,
+        files: input.files,
+        agents: input.agents,
+      })
+    }
+  }
+
+  export class Synthetic extends Schema.Class<Synthetic>("Session.Event.Synthetic")({
+    ...Base,
+    type: Schema.Literal("synthetic"),
+    text: Schema.String,
+  }) {
+    static create(input: BaseInput & { text: string }) {
+      return new Synthetic({
+        id: input.id ?? ID.create(),
+        type: "synthetic",
+        timestamp: input.timestamp ?? DateTime.makeUnsafe(Date.now()),
+        metadata: input.metadata,
+        text: input.text,
+      })
+    }
+  }
+
+  export namespace Step {
+    export class Started extends Schema.Class<Started>("Session.Event.Step.Started")({
+      ...Base,
+      type: Schema.Literal("step.started"),
+      model: Schema.Struct({
+        id: Schema.String,
+        providerID: Schema.String,
+        variant: Schema.String.pipe(Schema.optional),
+      }),
+    }) {
+      static create(input: BaseInput & { model: { id: string; providerID: string; variant?: string } }) {
+        return new Started({
+          id: input.id ?? ID.create(),
+          type: "step.started",
+          timestamp: input.timestamp ?? DateTime.makeUnsafe(Date.now()),
+          metadata: input.metadata,
+          model: input.model,
+        })
+      }
+    }
+
+    export class Ended extends Schema.Class<Ended>("Session.Event.Step.Ended")({
+      ...Base,
+      type: Schema.Literal("step.ended"),
+      reason: Schema.String,
+      cost: Schema.Number,
+      tokens: Schema.Struct({
+        input: Schema.Number,
+        output: Schema.Number,
+        reasoning: Schema.Number,
+        cache: Schema.Struct({
+          read: Schema.Number,
+          write: Schema.Number,
+        }),
+      }),
+    }) {
+      static create(input: BaseInput & { reason: string; cost: number; tokens: Ended["tokens"] }) {
+        return new Ended({
+          id: input.id ?? ID.create(),
+          type: "step.ended",
+          timestamp: input.timestamp ?? DateTime.makeUnsafe(Date.now()),
+          metadata: input.metadata,
+          reason: input.reason,
+          cost: input.cost,
+          tokens: input.tokens,
+        })
+      }
+    }
+  }
+
+  export namespace Text {
+    export class Started extends Schema.Class<Started>("Session.Event.Text.Started")({
+      ...Base,
+      type: Schema.Literal("text.started"),
+    }) {
+      static create(input: BaseInput = {}) {
+        return new Started({
+          id: input.id ?? ID.create(),
+          type: "text.started",
+          timestamp: input.timestamp ?? DateTime.makeUnsafe(Date.now()),
+          metadata: input.metadata,
+        })
+      }
+    }
+
+    export class Delta extends Schema.Class<Delta>("Session.Event.Text.Delta")({
+      ...Base,
+      type: Schema.Literal("text.delta"),
+      delta: Schema.String,
+    }) {
+      static create(input: BaseInput & { delta: string }) {
+        return new Delta({
+          id: input.id ?? ID.create(),
+          type: "text.delta",
+          timestamp: input.timestamp ?? DateTime.makeUnsafe(Date.now()),
+          metadata: input.metadata,
+          delta: input.delta,
+        })
+      }
+    }
+
+    export class Ended extends Schema.Class<Ended>("Session.Event.Text.Ended")({
+      ...Base,
+      type: Schema.Literal("text.ended"),
+      text: Schema.String,
+    }) {
+      static create(input: BaseInput & { text: string }) {
+        return new Ended({
+          id: input.id ?? ID.create(),
+          type: "text.ended",
+          timestamp: input.timestamp ?? DateTime.makeUnsafe(Date.now()),
+          metadata: input.metadata,
+          text: input.text,
+        })
+      }
+    }
+  }
+
+  export namespace Reasoning {
+    export class Started extends Schema.Class<Started>("Session.Event.Reasoning.Started")({
+      ...Base,
+      type: Schema.Literal("reasoning.started"),
+    }) {
+      static create(input: BaseInput = {}) {
+        return new Started({
+          id: input.id ?? ID.create(),
+          type: "reasoning.started",
+          timestamp: input.timestamp ?? DateTime.makeUnsafe(Date.now()),
+          metadata: input.metadata,
+        })
+      }
+    }
+
+    export class Delta extends Schema.Class<Delta>("Session.Event.Reasoning.Delta")({
+      ...Base,
+      type: Schema.Literal("reasoning.delta"),
+      delta: Schema.String,
+    }) {
+      static create(input: BaseInput & { delta: string }) {
+        return new Delta({
+          id: input.id ?? ID.create(),
+          type: "reasoning.delta",
+          timestamp: input.timestamp ?? DateTime.makeUnsafe(Date.now()),
+          metadata: input.metadata,
+          delta: input.delta,
+        })
+      }
+    }
+
+    export class Ended extends Schema.Class<Ended>("Session.Event.Reasoning.Ended")({
+      ...Base,
+      type: Schema.Literal("reasoning.ended"),
+      text: Schema.String,
+    }) {
+      static create(input: BaseInput & { text: string }) {
+        return new Ended({
+          id: input.id ?? ID.create(),
+          type: "reasoning.ended",
+          timestamp: input.timestamp ?? DateTime.makeUnsafe(Date.now()),
+          metadata: input.metadata,
+          text: input.text,
+        })
+      }
+    }
+  }
+
+  export namespace Tool {
+    export namespace Input {
+      export class Started extends Schema.Class<Started>("Session.Event.Tool.Input.Started")({
+        ...Base,
+        callID: Schema.String,
+        name: Schema.String,
+        type: Schema.Literal("tool.input.started"),
+      }) {
+        static create(input: BaseInput & { callID: string; name: string }) {
+          return new Started({
+            id: input.id ?? ID.create(),
+            type: "tool.input.started",
+            timestamp: input.timestamp ?? DateTime.makeUnsafe(Date.now()),
+            metadata: input.metadata,
+            callID: input.callID,
+            name: input.name,
+          })
+        }
+      }
+
+      export class Delta extends Schema.Class<Delta>("Session.Event.Tool.Input.Delta")({
+        ...Base,
+        callID: Schema.String,
+        type: Schema.Literal("tool.input.delta"),
+        delta: Schema.String,
+      }) {
+        static create(input: BaseInput & { callID: string; delta: string }) {
+          return new Delta({
+            id: input.id ?? ID.create(),
+            type: "tool.input.delta",
+            timestamp: input.timestamp ?? DateTime.makeUnsafe(Date.now()),
+            metadata: input.metadata,
+            callID: input.callID,
+            delta: input.delta,
+          })
+        }
+      }
+
+      export class Ended extends Schema.Class<Ended>("Session.Event.Tool.Input.Ended")({
+        ...Base,
+        callID: Schema.String,
+        type: Schema.Literal("tool.input.ended"),
+        text: Schema.String,
+      }) {
+        static create(input: BaseInput & { callID: string; text: string }) {
+          return new Ended({
+            id: input.id ?? ID.create(),
+            type: "tool.input.ended",
+            timestamp: input.timestamp ?? DateTime.makeUnsafe(Date.now()),
+            metadata: input.metadata,
+            callID: input.callID,
+            text: input.text,
+          })
+        }
+      }
+    }
+
+    export class Called extends Schema.Class<Called>("Session.Event.Tool.Called")({
+      ...Base,
+      type: Schema.Literal("tool.called"),
+      callID: Schema.String,
+      tool: Schema.String,
+      input: Schema.Record(Schema.String, Schema.Unknown),
+      provider: Schema.Struct({
+        executed: Schema.Boolean,
+        metadata: Schema.Record(Schema.String, Schema.Unknown).pipe(Schema.optional),
+      }),
+    }) {
+      static create(
+        input: BaseInput & {
+          callID: string
+          tool: string
+          input: Record<string, unknown>
+          provider: Called["provider"]
+        },
+      ) {
+        return new Called({
+          id: input.id ?? ID.create(),
+          type: "tool.called",
+          timestamp: input.timestamp ?? DateTime.makeUnsafe(Date.now()),
+          metadata: input.metadata,
+          callID: input.callID,
+          tool: input.tool,
+          input: input.input,
+          provider: input.provider,
+        })
+      }
+    }
+
+    export class Success extends Schema.Class<Success>("Session.Event.Tool.Success")({
+      ...Base,
+      type: Schema.Literal("tool.success"),
+      callID: Schema.String,
+      title: Schema.String,
+      output: Schema.String.pipe(Schema.optional),
+      attachments: Schema.Array(FileAttachment).pipe(Schema.optional),
+      provider: Schema.Struct({
+        executed: Schema.Boolean,
+        metadata: Schema.Record(Schema.String, Schema.Unknown).pipe(Schema.optional),
+      }),
+    }) {
+      static create(
+        input: BaseInput & {
+          callID: string
+          title: string
+          output?: string
+          attachments?: FileAttachment[]
+          provider: Success["provider"]
+        },
+      ) {
+        return new Success({
+          id: input.id ?? ID.create(),
+          type: "tool.success",
+          timestamp: input.timestamp ?? DateTime.makeUnsafe(Date.now()),
+          metadata: input.metadata,
+          callID: input.callID,
+          title: input.title,
+          output: input.output,
+          attachments: input.attachments,
+          provider: input.provider,
+        })
+      }
+    }
+
+    export class Error extends Schema.Class<Error>("Session.Event.Tool.Error")({
+      ...Base,
+      type: Schema.Literal("tool.error"),
+      callID: Schema.String,
+      error: Schema.String,
+      provider: Schema.Struct({
+        executed: Schema.Boolean,
+        metadata: Schema.Record(Schema.String, Schema.Unknown).pipe(Schema.optional),
+      }),
+    }) {
+      static create(input: BaseInput & { callID: string; error: string; provider: Error["provider"] }) {
+        return new Error({
+          id: input.id ?? ID.create(),
+          type: "tool.error",
+          timestamp: input.timestamp ?? DateTime.makeUnsafe(Date.now()),
+          metadata: input.metadata,
+          callID: input.callID,
+          error: input.error,
+          provider: input.provider,
+        })
+      }
+    }
+  }
+
+  export class Retried extends Schema.Class<Retried>("Session.Event.Retried")({
+    ...Base,
+    type: Schema.Literal("retried"),
+    error: Schema.String,
+  }) {
+    static create(input: BaseInput & { error: string }) {
+      return new Retried({
+        id: input.id ?? ID.create(),
+        type: "retried",
+        timestamp: input.timestamp ?? DateTime.makeUnsafe(Date.now()),
+        metadata: input.metadata,
+        error: input.error,
+      })
+    }
+  }
+
+  export class Compacted extends Schema.Class<Compacted>("Session.Event.Compated")({
+    ...Base,
+    type: Schema.Literal("compacted"),
+    auto: Schema.Boolean,
+    overflow: Schema.Boolean.pipe(Schema.optional),
+  }) {
+    static create(input: BaseInput & { auto: boolean; overflow?: boolean }) {
+      return new Compacted({
+        id: input.id ?? ID.create(),
+        type: "compacted",
+        timestamp: input.timestamp ?? DateTime.makeUnsafe(Date.now()),
+        metadata: input.metadata,
+        auto: input.auto,
+        overflow: input.overflow,
+      })
+    }
+  }
+
+  export const Event = Schema.Union(
+    [
+      Prompt,
+      Synthetic,
+      Step.Started,
+      Step.Ended,
+      Text.Started,
+      Text.Delta,
+      Text.Ended,
+      Tool.Input.Started,
+      Tool.Input.Delta,
+      Tool.Input.Ended,
+      Tool.Called,
+      Tool.Success,
+      Tool.Error,
+      Reasoning.Started,
+      Reasoning.Delta,
+      Reasoning.Ended,
+      Retried,
+      Compacted,
+    ],
+    {
+      mode: "oneOf",
+    },
+  )
+  export type Event = Schema.Schema.Type<typeof Event>
+  export type Type = Event["type"]
+}
diff --git a/packages/opencode/test/session/session-entry.test.ts b/packages/opencode/test/session/session-entry.test.ts
new file mode 100644
index 000000000..7eba3900d
--- /dev/null
+++ b/packages/opencode/test/session/session-entry.test.ts
@@ -0,0 +1,624 @@
+import { describe, expect, test } from "bun:test"
+import * as DateTime from "effect/DateTime"
+import * as FastCheck from "effect/testing/FastCheck"
+import { SessionEntry } from "../../src/v2/session-entry"
+import { SessionEvent } from "../../src/v2/session-event"
+
+const time = (n: number) => DateTime.makeUnsafe(n)
+
+const word = FastCheck.string({ minLength: 1, maxLength: 8 })
+const text = FastCheck.string({ maxLength: 16 })
+const texts = FastCheck.array(text, { maxLength: 8 })
+const val = FastCheck.oneof(FastCheck.boolean(), FastCheck.integer(), FastCheck.string({ maxLength: 12 }))
+const dict = FastCheck.dictionary(word, val, { maxKeys: 4 })
+const files = FastCheck.array(
+  word.map((x) => SessionEvent.FileAttachment.create({ uri: `file://${encodeURIComponent(x)}`, mime: "text/plain" })),
+  { maxLength: 2 },
+)
+
+function maybe<A>(arb: FastCheck.Arbitrary<A>) {
+  return FastCheck.oneof(FastCheck.constant(undefined), arb)
+}
+
+function assistant() {
+  return new SessionEntry.Assistant({
+    id: SessionEvent.ID.create(),
+    type: "assistant",
+    time: { created: time(0) },
+    content: [],
+  })
+}
+
+function history() {
+  const state: SessionEntry.History = {
+    entries: [],
+    pending: [],
+  }
+  return state
+}
+
+function active() {
+  const state: SessionEntry.History = {
+    entries: [assistant()],
+    pending: [],
+  }
+  return state
+}
+
+function run(events: SessionEvent.Event[], state = history()) {
+  return events.reduce<SessionEntry.History>((state, event) => SessionEntry.step(state, event), state)
+}
+
+function last(state: SessionEntry.History) {
+  const entry = [...state.pending, ...state.entries].reverse().find((x) => x.type === "assistant")
+  expect(entry?.type).toBe("assistant")
+  return entry?.type === "assistant" ? entry : undefined
+}
+
+function texts_of(state: SessionEntry.History) {
+  const entry = last(state)
+  if (!entry) return []
+  return entry.content.filter((x): x is SessionEntry.AssistantText => x.type === "text")
+}
+
+function reasons(state: SessionEntry.History) {
+  const entry = last(state)
+  if (!entry) return []
+  return entry.content.filter((x): x is SessionEntry.AssistantReasoning => x.type === "reasoning")
+}
+
+function tools(state: SessionEntry.History) {
+  const entry = last(state)
+  if (!entry) return []
+  return entry.content.filter((x): x is SessionEntry.AssistantTool => x.type === "tool")
+}
+
+function tool(state: SessionEntry.History, callID: string) {
+  return tools(state).find((x) => x.callID === callID)
+}
+
+describe("session-entry step", () => {
+  describe("seeded pending assistant", () => {
+    test("stores prompts in entries when no assistant is pending", () => {
+      FastCheck.assert(
+        FastCheck.property(word, (body) => {
+          const next = SessionEntry.step(history(), SessionEvent.Prompt.create({ text: body, timestamp: time(1) }))
+          expect(next.entries).toHaveLength(1)
+          expect(next.entries[0]?.type).toBe("user")
+          if (next.entries[0]?.type !== "user") return
+          expect(next.entries[0].text).toBe(body)
+        }),
+        { numRuns: 50 },
+      )
+    })
+
+    test("stores prompts in pending when an assistant is pending", () => {
+      FastCheck.assert(
+        FastCheck.property(word, (body) => {
+          const next = SessionEntry.step(active(), SessionEvent.Prompt.create({ text: body, timestamp: time(1) }))
+          expect(next.pending).toHaveLength(1)
+          expect(next.pending[0]?.type).toBe("user")
+          if (next.pending[0]?.type !== "user") return
+          expect(next.pending[0].text).toBe(body)
+        }),
+        { numRuns: 50 },
+      )
+    })
+
+    test("accumulates text deltas on the latest text part", () => {
+      FastCheck.assert(
+        FastCheck.property(texts, (parts) => {
+          const next = parts.reduce(
+            (state, part, i) =>
+              SessionEntry.step(state, SessionEvent.Text.Delta.create({ delta: part, timestamp: time(i + 2) })),
+            SessionEntry.step(active(), SessionEvent.Text.Started.create({ timestamp: time(1) })),
+          )
+
+          expect(texts_of(next)).toEqual([
+            {
+              type: "text",
+              text: parts.join(""),
+            },
+          ])
+        }),
+        { numRuns: 100 },
+      )
+    })
+
+    test("routes later text deltas to the latest text segment", () => {
+      FastCheck.assert(
+        FastCheck.property(texts, texts, (a, b) => {
+          const next = run(
+            [
+              SessionEvent.Text.Started.create({ timestamp: time(1) }),
+              ...a.map((x, i) => SessionEvent.Text.Delta.create({ delta: x, timestamp: time(i + 2) })),
+              SessionEvent.Text.Started.create({ timestamp: time(a.length + 2) }),
+              ...b.map((x, i) => SessionEvent.Text.Delta.create({ delta: x, timestamp: time(i + a.length + 3) })),
+            ],
+            active(),
+          )
+
+          expect(texts_of(next)).toEqual([
+            { type: "text", text: a.join("") },
+            { type: "text", text: b.join("") },
+          ])
+        }),
+        { numRuns: 50 },
+      )
+    })
+
+    test("reasoning.ended replaces buffered reasoning text", () => {
+      FastCheck.assert(
+        FastCheck.property(texts, text, (parts, end) => {
+          const next = run(
+            [
+              SessionEvent.Reasoning.Started.create({ timestamp: time(1) }),
+              ...parts.map((x, i) => SessionEvent.Reasoning.Delta.create({ delta: x, timestamp: time(i + 2) })),
+              SessionEvent.Reasoning.Ended.create({ text: end, timestamp: time(parts.length + 2) }),
+            ],
+            active(),
+          )
+
+          expect(reasons(next)).toEqual([
+            {
+              type: "reasoning",
+              text: end,
+            },
+          ])
+        }),
+        { numRuns: 100 },
+      )
+    })
+
+    test("tool.success completes the latest running tool", () => {
+      FastCheck.assert(
+        FastCheck.property(
+          word,
+          word,
+          dict,
+          maybe(text),
+          maybe(dict),
+          maybe(files),
+          texts,
+          (callID, title, input, output, metadata, attachments, parts) => {
+            const next = run(
+              [
+                SessionEvent.Tool.Input.Started.create({ callID, name: "bash", timestamp: time(1) }),
+                ...parts.map((x, i) =>
+                  SessionEvent.Tool.Input.Delta.create({ callID, delta: x, timestamp: time(i + 2) }),
+                ),
+                SessionEvent.Tool.Called.create({
+                  callID,
+                  tool: "bash",
+                  input,
+                  provider: { executed: true },
+                  timestamp: time(parts.length + 2),
+                }),
+                SessionEvent.Tool.Success.create({
+                  callID,
+                  title,
+                  output,
+                  metadata,
+                  attachments,
+                  provider: { executed: true },
+                  timestamp: time(parts.length + 3),
+                }),
+              ],
+              active(),
+            )
+
+            const match = tool(next, callID)
+            expect(match?.state.status).toBe("completed")
+            if (match?.state.status !== "completed") return
+
+            expect(match.time.ran).toEqual(time(parts.length + 2))
+            expect(match.state.input).toEqual(input)
+            expect(match.state.output).toBe(output ?? "")
+            expect(match.state.title).toBe(title)
+            expect(match.state.metadata).toEqual(metadata ?? {})
+            expect(match.state.attachments).toEqual(attachments ?? [])
+          },
+        ),
+        { numRuns: 50 },
+      )
+    })
+
+    test("tool.error completes the latest running tool with an error", () => {
+      FastCheck.assert(
+        FastCheck.property(word, dict, word, maybe(dict), (callID, input, error, metadata) => {
+          const next = run(
+            [
+              SessionEvent.Tool.Input.Started.create({ callID, name: "bash", timestamp: time(1) }),
+              SessionEvent.Tool.Called.create({
+                callID,
+                tool: "bash",
+                input,
+                provider: { executed: true },
+                timestamp: time(2),
+              }),
+              SessionEvent.Tool.Error.create({
+                callID,
+                error,
+                metadata,
+                provider: { executed: true },
+                timestamp: time(3),
+              }),
+            ],
+            active(),
+          )
+
+          const match = tool(next, callID)
+          expect(match?.state.status).toBe("error")
+          if (match?.state.status !== "error") return
+
+          expect(match.time.ran).toEqual(time(2))
+          expect(match.state.input).toEqual(input)
+          expect(match.state.error).toBe(error)
+          expect(match.state.metadata).toEqual(metadata ?? {})
+        }),
+        { numRuns: 50 },
+      )
+    })
+
+    test("tool.success is ignored before tool.called promotes the tool to running", () => {
+      FastCheck.assert(
+        FastCheck.property(word, word, (callID, title) => {
+          const next = run(
+            [
+              SessionEvent.Tool.Input.Started.create({ callID, name: "bash", timestamp: time(1) }),
+              SessionEvent.Tool.Success.create({
+                callID,
+                title,
+                provider: { executed: true },
+                timestamp: time(2),
+              }),
+            ],
+            active(),
+          )
+          const match = tool(next, callID)
+          expect(match?.state).toEqual({
+            status: "pending",
+            input: "",
+          })
+        }),
+        { numRuns: 50 },
+      )
+    })
+
+    test("step.ended copies completion fields onto the pending assistant", () => {
+      FastCheck.assert(
+        FastCheck.property(FastCheck.integer({ min: 1, max: 1000 }), (n) => {
+          const event = SessionEvent.Step.Ended.create({
+            reason: "stop",
+            cost: 1,
+            tokens: {
+              input: 1,
+              output: 2,
+              reasoning: 3,
+              cache: {
+                read: 4,
+                write: 5,
+              },
+            },
+            timestamp: time(n),
+          })
+          const next = SessionEntry.step(active(), event)
+          const entry = last(next)
+          expect(entry).toBeDefined()
+          if (!entry) return
+
+          expect(entry.time.completed).toEqual(event.timestamp)
+          expect(entry.cost).toBe(event.cost)
+          expect(entry.tokens).toEqual(event.tokens)
+        }),
+        { numRuns: 50 },
+      )
+    })
+  })
+
+  describe("known reducer gaps", () => {
+    test("prompt appends immutably when no assistant is pending", () => {
+      FastCheck.assert(
+        FastCheck.property(word, (body) => {
+          const old = history()
+          const next = SessionEntry.step(old, SessionEvent.Prompt.create({ text: body, timestamp: time(1) }))
+          expect(old).not.toBe(next)
+          expect(old.entries).toHaveLength(0)
+          expect(next.entries).toHaveLength(1)
+        }),
+        { numRuns: 50 },
+      )
+    })
+
+    test("prompt appends immutably when an assistant is pending", () => {
+      FastCheck.assert(
+        FastCheck.property(word, (body) => {
+          const old = active()
+          const next = SessionEntry.step(old, SessionEvent.Prompt.create({ text: body, timestamp: time(1) }))
+          expect(old).not.toBe(next)
+          expect(old.pending).toHaveLength(0)
+          expect(next.pending).toHaveLength(1)
+        }),
+        { numRuns: 50 },
+      )
+    })
+
+    test("step.started creates an assistant consumed by follow-up events", () => {
+      FastCheck.assert(
+        FastCheck.property(texts, (parts) => {
+          const next = run([
+            SessionEvent.Step.Started.create({
+              model: {
+                id: "model",
+                providerID: "provider",
+              },
+              timestamp: time(1),
+            }),
+            SessionEvent.Text.Started.create({ timestamp: time(2) }),
+            ...parts.map((x, i) => SessionEvent.Text.Delta.create({ delta: x, timestamp: time(i + 3) })),
+            SessionEvent.Step.Ended.create({
+              reason: "stop",
+              cost: 1,
+              tokens: {
+                input: 1,
+                output: 2,
+                reasoning: 3,
+                cache: {
+                  read: 4,
+                  write: 5,
+                },
+              },
+              timestamp: time(parts.length + 3),
+            }),
+          ])
+          const entry = last(next)
+
+          expect(entry).toBeDefined()
+          if (!entry) return
+
+          expect(entry.content).toEqual([
+            {
+              type: "text",
+              text: parts.join(""),
+            },
+          ])
+          expect(entry.time.completed).toEqual(time(parts.length + 3))
+        }),
+        { numRuns: 100 },
+      )
+    })
+
+    test("replays prompt -> step -> text -> step.ended", () => {
+      FastCheck.assert(
+        FastCheck.property(word, texts, (body, parts) => {
+          const next = run([
+            SessionEvent.Prompt.create({ text: body, timestamp: time(0) }),
+            SessionEvent.Step.Started.create({
+              model: {
+                id: "model",
+                providerID: "provider",
+              },
+              timestamp: time(1),
+            }),
+            SessionEvent.Text.Started.create({ timestamp: time(2) }),
+            ...parts.map((x, i) => SessionEvent.Text.Delta.create({ delta: x, timestamp: time(i + 3) })),
+            SessionEvent.Step.Ended.create({
+              reason: "stop",
+              cost: 1,
+              tokens: {
+                input: 1,
+                output: 2,
+                reasoning: 3,
+                cache: {
+                  read: 4,
+                  write: 5,
+                },
+              },
+              timestamp: time(parts.length + 3),
+            }),
+          ])
+
+          expect(next.entries).toHaveLength(2)
+          expect(next.entries[0]?.type).toBe("user")
+          expect(next.entries[1]?.type).toBe("assistant")
+          if (next.entries[1]?.type !== "assistant") return
+
+          expect(next.entries[1].content).toEqual([
+            {
+              type: "text",
+              text: parts.join(""),
+            },
+          ])
+          expect(next.entries[1].time.completed).toEqual(time(parts.length + 3))
+        }),
+        { numRuns: 50 },
+      )
+    })
+
+    test("replays prompt -> step -> reasoning -> tool -> success -> step.ended", () => {
+      FastCheck.assert(
+        FastCheck.property(
+          word,
+          texts,
+          text,
+          dict,
+          word,
+          maybe(text),
+          maybe(dict),
+          maybe(files),
+          (body, reason, end, input, title, output, metadata, attachments) => {
+            const callID = "call"
+            const next = run([
+              SessionEvent.Prompt.create({ text: body, timestamp: time(0) }),
+              SessionEvent.Step.Started.create({
+                model: {
+                  id: "model",
+                  providerID: "provider",
+                },
+                timestamp: time(1),
+              }),
+              SessionEvent.Reasoning.Started.create({ timestamp: time(2) }),
+              ...reason.map((x, i) => SessionEvent.Reasoning.Delta.create({ delta: x, timestamp: time(i + 3) })),
+              SessionEvent.Reasoning.Ended.create({ text: end, timestamp: time(reason.length + 3) }),
+              SessionEvent.Tool.Input.Started.create({ callID, name: "bash", timestamp: time(reason.length + 4) }),
+              SessionEvent.Tool.Called.create({
+                callID,
+                tool: "bash",
+                input,
+                provider: { executed: true },
+                timestamp: time(reason.length + 5),
+              }),
+              SessionEvent.Tool.Success.create({
+                callID,
+                title,
+                output,
+                metadata,
+                attachments,
+                provider: { executed: true },
+                timestamp: time(reason.length + 6),
+              }),
+              SessionEvent.Step.Ended.create({
+                reason: "stop",
+                cost: 1,
+                tokens: {
+                  input: 1,
+                  output: 2,
+                  reasoning: 3,
+                  cache: {
+                    read: 4,
+                    write: 5,
+                  },
+                },
+                timestamp: time(reason.length + 7),
+              }),
+            ])
+
+            expect(next.entries.at(-1)?.type).toBe("assistant")
+            const entry = next.entries.at(-1)
+            if (entry?.type !== "assistant") return
+
+            expect(entry.content).toHaveLength(2)
+            expect(entry.content[0]).toEqual({
+              type: "reasoning",
+              text: end,
+            })
+            expect(entry.content[1]?.type).toBe("tool")
+            if (entry.content[1]?.type !== "tool") return
+            expect(entry.content[1].state.status).toBe("completed")
+            expect(entry.time.completed).toEqual(time(reason.length + 7))
+          },
+        ),
+        { numRuns: 50 },
+      )
+    })
+
+    test("starting a new step completes the old assistant and appends a new active assistant", () => {
+      const next = run(
+        [
+          SessionEvent.Step.Started.create({
+            model: {
+              id: "model",
+              providerID: "provider",
+            },
+            timestamp: time(1),
+          }),
+        ],
+        active(),
+      )
+      expect(next.entries).toHaveLength(2)
+      expect(next.entries[0]?.type).toBe("assistant")
+      expect(next.entries[1]?.type).toBe("assistant")
+      if (next.entries[0]?.type !== "assistant" || next.entries[1]?.type !== "assistant") return
+
+      expect(next.entries[0].time.completed).toEqual(time(1))
+      expect(next.entries[1].time.created).toEqual(time(1))
+      expect(next.entries[1].time.completed).toBeUndefined()
+    })
+
+    test("handles sequential tools independently", () => {
+      FastCheck.assert(
+        FastCheck.property(dict, dict, word, word, (a, b, title, error) => {
+          const next = run(
+            [
+              SessionEvent.Tool.Input.Started.create({ callID: "a", name: "bash", timestamp: time(1) }),
+              SessionEvent.Tool.Called.create({
+                callID: "a",
+                tool: "bash",
+                input: a,
+                provider: { executed: true },
+                timestamp: time(2),
+              }),
+              SessionEvent.Tool.Success.create({
+                callID: "a",
+                title,
+                output: "done",
+                provider: { executed: true },
+                timestamp: time(3),
+              }),
+              SessionEvent.Tool.Input.Started.create({ callID: "b", name: "grep", timestamp: time(4) }),
+              SessionEvent.Tool.Called.create({
+                callID: "b",
+                tool: "bash",
+                input: b,
+                provider: { executed: true },
+                timestamp: time(5),
+              }),
+              SessionEvent.Tool.Error.create({
+                callID: "b",
+                error,
+                provider: { executed: true },
+                timestamp: time(6),
+              }),
+            ],
+            active(),
+          )
+
+          const first = tool(next, "a")
+          const second = tool(next, "b")
+
+          expect(first?.state.status).toBe("completed")
+          if (first?.state.status !== "completed") return
+          expect(first.state.input).toEqual(a)
+          expect(first.state.output).toBe("done")
+          expect(first.state.title).toBe(title)
+
+          expect(second?.state.status).toBe("error")
+          if (second?.state.status !== "error") return
+          expect(second.state.input).toEqual(b)
+          expect(second.state.error).toBe(error)
+        }),
+        { numRuns: 50 },
+      )
+    })
+
+    test.failing("records synthetic events", () => {
+      FastCheck.assert(
+        FastCheck.property(word, (body) => {
+          const next = SessionEntry.step(history(), SessionEvent.Synthetic.create({ text: body, timestamp: time(1) }))
+          expect(next.entries).toHaveLength(1)
+          expect(next.entries[0]?.type).toBe("synthetic")
+          if (next.entries[0]?.type !== "synthetic") return
+          expect(next.entries[0].text).toBe(body)
+        }),
+        { numRuns: 50 },
+      )
+    })
+
+    test.failing("records compaction events", () => {
+      FastCheck.assert(
+        FastCheck.property(FastCheck.boolean(), maybe(FastCheck.boolean()), (auto, overflow) => {
+          const next = SessionEntry.step(
+            history(),
+            SessionEvent.Compacted.create({ auto, overflow, timestamp: time(1) }),
+          )
+          expect(next.entries).toHaveLength(1)
+          expect(next.entries[0]?.type).toBe("compaction")
+          if (next.entries[0]?.type !== "compaction") return
+          expect(next.entries[0].auto).toBe(auto)
+          expect(next.entries[0].overflow).toBe(overflow)
+        }),
+        { numRuns: 50 },
+      )
+    })
+  })
+})
diff --git a/packages/opencode/test/tool/truncation.test.ts b/packages/opencode/test/tool/truncation.test.ts
index 493cd9d7e..c9ef0d82a 100644
--- a/packages/opencode/test/tool/truncation.test.ts
+++ b/packages/opencode/test/tool/truncation.test.ts
@@ -181,8 +181,8 @@ describe("Truncate", () => {
 
         yield* fs.makeDirectory(Truncate.DIR, { recursive: true })
 
-        const old = path.join(Truncate.DIR, Identifier.create("tool", false, Date.now() - 10 * DAY_MS))
-        const recent = path.join(Truncate.DIR, Identifier.create("tool", false, Date.now() - 3 * DAY_MS))
+        const old = path.join(Truncate.DIR, Identifier.create("tool", "ascending", Date.now() - 10 * DAY_MS))
+        const recent = path.join(Truncate.DIR, Identifier.create("tool", "ascending", Date.now() - 3 * DAY_MS))
 
         yield* writeFileStringScoped(old, "old content")
         yield* writeFileStringScoped(recent, "recent content")