diff --git a/packages/client/src/promise/generated/types.ts b/packages/client/src/promise/generated/types.ts
index 460117b99ab2..9439a461c8ff 100644
--- a/packages/client/src/promise/generated/types.ts
+++ b/packages/client/src/promise/generated/types.ts
@@ -2232,7 +2232,7 @@ export type SessionInfo = {
   cost: MoneyUSD
   tokens: TokenUsageInfo
   outcome?: "succeeded" | "failed" | "interrupted"
-  time: { created: number; updated: number; idle?: number; viewed?: number; archived?: number }
+  time: { created: number; updated: number; busy?: number; idle?: number; viewed?: number; archived?: number }
   title?: string
   subpath?: RelativePath
   metadata?: SessionMetadata
@@ -3685,6 +3685,7 @@ export type ExperimentalSessionImportInput = {
     readonly time: {
       readonly created: number
       readonly updated: number
+      readonly busy?: number
       readonly idle?: number
       readonly viewed?: number
       readonly archived?: number
diff --git a/packages/client/src/solid/data.ts b/packages/client/src/solid/data.ts
index 17c8bbb1227e..30aee4392362 100644
--- a/packages/client/src/solid/data.ts
+++ b/packages/client/src/solid/data.ts
@@ -1108,6 +1108,10 @@ export function createData(config: CreateDataInput) {
         return
       case "session.execution.started":
         setSessionActive(event.data.sessionID, "running")
+        // Revalidate so `time.busy` follows the projected execution start.
+        if (!store.session.info[event.data.sessionID] && !sync.has(`session:${event.data.sessionID}`)) return
+        result.session.invalidate(event.data.sessionID)
+        refresh(() => result.session.sync(event.data.sessionID))
         return
       case "session.compaction.started":
         if (event.data.inputID) removePending(event.data.sessionID, event.data.inputID)
diff --git a/packages/client/test/solid-data.test.ts b/packages/client/test/solid-data.test.ts
index 53d536ca746f..69dea99a2455 100644
--- a/packages/client/test/solid-data.test.ts
+++ b/packages/client/test/solid-data.test.ts
@@ -330,6 +330,50 @@ test("omits inline tool-result file payloads from read and live tool results whe
   }
 })
 
+test("refreshes a loaded session's execution start when it starts running", async () => {
+  const listeners = new Set<Parameters<CreateDataInput["event"]["listen"]>[0]>()
+  const api = OpenCode.make({
+    baseUrl: "http://opencode.local",
+    fetch: async (input, init) => {
+      const request = input instanceof Request ? input : new Request(input, init)
+      if (!request.url.endsWith("/api/session/ses_refresh")) throw new Error(`Unexpected request: ${request.url}`)
+      return Response.json({ data: { ...session(2), time: { ...session(2).time, busy: 3 } } })
+    },
+  })
+  const event: CreateDataInput["event"] = {
+    on:
+      <Type extends OpenCodeEvent["type"]>(
+        _type: Type,
+        _handler: (event: Extract<OpenCodeEvent, { type: Type }>) => void,
+      ) =>
+      () => {},
+    listen(handler) {
+      listeners.add(handler)
+      return () => listeners.delete(handler)
+    },
+  }
+  const setup = createRoot((dispose) => ({
+    data: createData({ api: () => api, directory: "/project", event, connection: { status: () => "connected" } }),
+    dispose,
+  }))
+
+  try {
+    setup.data.session.remember(session(2))
+    const started: OpenCodeEvent = {
+      id: "evt_started",
+      created: 3,
+      type: "session.execution.started",
+      durable: { aggregateID: "ses_refresh", seq: 1, version: 1 },
+      data: { sessionID: "ses_refresh" },
+    }
+    listeners.forEach((listener) => listener({ name: started.type, details: started }))
+    expect(setup.data.session.status("ses_refresh")).toBe("running")
+    await wait(() => setup.data.session.get("ses_refresh")?.time.busy === 3)
+  } finally {
+    setup.dispose()
+  }
+})
+
 test("revalidates after an event overtakes an active session read", async () => {
   let release!: () => void
   const gate = new Promise<void>((resolve) => (release = resolve))
diff --git a/packages/core/schema.json b/packages/core/schema.json
index c643c298402b..bb629130d75f 100644
--- a/packages/core/schema.json
+++ b/packages/core/schema.json
@@ -1,8 +1,8 @@
 {
   "version": "7",
   "dialect": "sqlite",
-  "id": "dc16dd12-cb76-432f-8108-0c3aadaf54bb",
-  "prevIds": ["23940db2-8b4e-4a5e-a404-70d785bd788c"],
+  "id": "e5daa0af-cae7-4057-919a-ebf44dfced0a",
+  "prevIds": ["dc16dd12-cb76-432f-8108-0c3aadaf54bb"],
   "ddl": [
     {
       "name": "account_state",
@@ -1672,6 +1672,16 @@
       "entityType": "columns",
       "table": "session_v2"
     },
+    {
+      "type": "integer",
+      "notNull": false,
+      "autoincrement": false,
+      "default": null,
+      "generated": null,
+      "name": "time_busy",
+      "entityType": "columns",
+      "table": "session_v2"
+    },
     {
       "type": "integer",
       "notNull": false,
diff --git a/packages/core/src/database/migration.gen.ts b/packages/core/src/database/migration.gen.ts
index 5438f244a777..f5afbd4fb6d5 100644
--- a/packages/core/src/database/migration.gen.ts
+++ b/packages/core/src/database/migration.gen.ts
@@ -55,6 +55,7 @@ import m52 from "./migration/20261025123711_blob.js"
 import m53 from "./migration/20261025154125_drop_session_pending.js"
 import m54 from "./migration/20261026223005_schedule.js"
 import m55 from "./migration/20261029002625_session_part.js"
+import m56 from "./migration/20261029073502_session_time_busy.js"
 
 export const migrations = [
   m00,
@@ -113,4 +114,5 @@ export const migrations = [
   m53,
   m54,
   m55,
+  m56,
 ] satisfies DatabaseMigration.Migration[]
diff --git a/packages/core/src/database/migration/20261029073502_session_time_busy.ts b/packages/core/src/database/migration/20261029073502_session_time_busy.ts
new file mode 100644
index 000000000000..b0bdd0ee1cfe
--- /dev/null
+++ b/packages/core/src/database/migration/20261029073502_session_time_busy.ts
@@ -0,0 +1,13 @@
+import { Effect } from "effect"
+import type { DatabaseMigration } from "../migration.js"
+
+const migration: DatabaseMigration.Migration = {
+  id: "20261029073502_session_time_busy",
+  up(tx) {
+    return Effect.gen(function* () {
+      yield* tx.run(`ALTER TABLE \`session_v2\` ADD \`time_busy\` integer;`)
+    })
+  },
+}
+
+export default migration
diff --git a/packages/core/src/database/schema.gen.ts b/packages/core/src/database/schema.gen.ts
index 6a7ef1601ab1..2cb123ff319b 100644
--- a/packages/core/src/database/schema.gen.ts
+++ b/packages/core/src/database/schema.gen.ts
@@ -258,6 +258,7 @@ const schema: Omit<DatabaseMigration.Migration, "id"> = {
           \`model\` text,
           \`time_created\` integer NOT NULL,
           \`time_updated\` integer NOT NULL,
+          \`time_busy\` integer,
           \`time_idle\` integer,
           \`time_viewed\` integer,
           \`idle_outcome\` text,
diff --git a/packages/core/src/session/info.ts b/packages/core/src/session/info.ts
index ab8a78c6c004..bde75487c249 100644
--- a/packages/core/src/session/info.ts
+++ b/packages/core/src/session/info.ts
@@ -52,6 +52,7 @@ export function fromRow(row: typeof SessionTable.$inferSelect): SessionSchema.In
     time: {
       created: DateTime.makeUnsafe(row.time_created),
       updated: DateTime.makeUnsafe(row.time_updated),
+      busy: row.time_busy === null ? undefined : DateTime.makeUnsafe(row.time_busy),
       idle: row.time_idle === null ? undefined : DateTime.makeUnsafe(row.time_idle),
       viewed: row.time_viewed === null ? undefined : DateTime.makeUnsafe(row.time_viewed),
       archived: row.time_archived === null ? undefined : DateTime.makeUnsafe(row.time_archived),
diff --git a/packages/core/src/session/projector.ts b/packages/core/src/session/projector.ts
index f15c07829f6d..0f0136c1768d 100644
--- a/packages/core/src/session/projector.ts
+++ b/packages/core/src/session/projector.ts
@@ -787,6 +787,14 @@ const layer = Layer.effectDiscard(
         delivery: event.data.delivery,
       }),
     )
+    yield* bus.project(SessionEvent.Execution.Started, (event) =>
+      db
+        .update(SessionTable)
+        .set({ time_busy: event.created, time_updated: sql`${SessionTable.time_updated}` })
+        .where(eq(SessionTable.id, event.data.sessionID))
+        .run()
+        .pipe(Effect.orDie),
+    )
     yield* bus.project(SessionEvent.Execution.Succeeded, (event) => projectIdle(db, event))
     yield* bus.project(SessionEvent.Execution.Failed, (event) => projectIdle(db, event))
     yield* bus.project(SessionEvent.Execution.Interrupted, (event) => projectIdle(db, event))
diff --git a/packages/core/src/session/sql.ts b/packages/core/src/session/sql.ts
index 0f02d94f38e9..8684925220d9 100644
--- a/packages/core/src/session/sql.ts
+++ b/packages/core/src/session/sql.ts
@@ -63,6 +63,7 @@ export const SessionTable = sqliteTable(
       variant?: string
     }>(),
     ...Timestamps,
+    time_busy: integer(),
     time_idle: integer(),
     time_viewed: integer(),
     idle_outcome: text().$type<NonNullable<Session.Info["outcome"]>>(),
diff --git a/packages/core/src/session/transfer.ts b/packages/core/src/session/transfer.ts
index 52e22a57402a..f123a20497e4 100644
--- a/packages/core/src/session/transfer.ts
+++ b/packages/core/src/session/transfer.ts
@@ -154,6 +154,13 @@ const layer = Layer.effect(
                       tokens_cache_write: input.data.info.tokens.cache.write,
                       time_created: DateTime.toEpochMillis(input.data.info.time.created),
                       time_updated: importedAt,
+                      time_busy:
+                        input.data.info.time.idle && input.data.info.time.busy
+                          ? Math.min(
+                              DateTime.toEpochMillis(input.data.info.time.idle),
+                              DateTime.toEpochMillis(input.data.info.time.busy),
+                            )
+                          : null,
                       time_idle: input.data.info.time.idle ? DateTime.toEpochMillis(input.data.info.time.idle) : null,
                       time_viewed:
                         input.data.info.time.idle && input.data.info.time.viewed
diff --git a/packages/core/test/session-create.test.ts b/packages/core/test/session-create.test.ts
index 41ed037b9b76..0caa7731b1d3 100644
--- a/packages/core/test/session-create.test.ts
+++ b/packages/core/test/session-create.test.ts
@@ -1438,6 +1438,7 @@ describe("SessionTransfer", () => {
             time: {
               ...template.time,
               updated: DateTime.makeUnsafe(100),
+              busy: DateTime.makeUnsafe(120),
               idle: DateTime.makeUnsafe(200),
               viewed: DateTime.makeUnsafe(150),
             },
@@ -1479,6 +1480,7 @@ describe("SessionTransfer", () => {
       })
       expect(imported.time).toMatchObject({
         updated: DateTime.makeUnsafe(1_000),
+        busy: DateTime.makeUnsafe(120),
         idle: DateTime.makeUnsafe(200),
         viewed: DateTime.makeUnsafe(150),
       })
@@ -1488,7 +1490,11 @@ describe("SessionTransfer", () => {
       ])
       expect(yield* Bus.latestSequence(db, sessionID)).toBe(2)
       const exported = yield* transfer.export({ sessionID })
-      expect(exported.info.time).toMatchObject({ idle: DateTime.makeUnsafe(200), viewed: DateTime.makeUnsafe(150) })
+      expect(exported.info.time).toMatchObject({
+        busy: DateTime.makeUnsafe(120),
+        idle: DateTime.makeUnsafe(200),
+        viewed: DateTime.makeUnsafe(150),
+      })
       expect(exported.messages).toEqual(messages)
       const sanitized = yield* transfer.export({ sessionID, sanitize: true })
       expect(sanitized.info.time).toMatchObject({ idle: DateTime.makeUnsafe(200), viewed: DateTime.makeUnsafe(150) })
@@ -1527,7 +1533,7 @@ describe("SessionTransfer", () => {
     }),
   )
 
-  it.effect("clamps an imported viewed watermark to its idle transition", () =>
+  it.effect("clamps imported busy and viewed watermarks to their idle transition", () =>
     Effect.gen(function* () {
       const session = yield* Session.Service
       const transfer = yield* SessionTransfer.Service
@@ -1540,6 +1546,7 @@ describe("SessionTransfer", () => {
             outcome: "succeeded",
             time: {
               ...template.time,
+              busy: DateTime.makeUnsafe(300),
               idle: DateTime.makeUnsafe(200),
               viewed: DateTime.makeUnsafe(250),
             },
@@ -1549,7 +1556,11 @@ describe("SessionTransfer", () => {
         location,
       })
 
-      expect(imported.time).toMatchObject({ idle: DateTime.makeUnsafe(200), viewed: DateTime.makeUnsafe(200) })
+      expect(imported.time).toMatchObject({
+        busy: DateTime.makeUnsafe(200),
+        idle: DateTime.makeUnsafe(200),
+        viewed: DateTime.makeUnsafe(200),
+      })
       expect(imported.outcome).toBe("succeeded")
     }),
   )
diff --git a/packages/core/test/session-projector.test.ts b/packages/core/test/session-projector.test.ts
index 53458bbb31f5..ab50f233d935 100644
--- a/packages/core/test/session-projector.test.ts
+++ b/packages/core/test/session-projector.test.ts
@@ -600,6 +600,37 @@ describe("SessionProjector", () => {
     }),
   )
 
+  it.effect("records each execution's start, including a resume after shutdown", () =>
+    Effect.gen(function* () {
+      const db = yield* seedSession({ time_created: 0, time_updated: 0 })
+      const bus = yield* Bus.Service
+      const times = () =>
+        db
+          .select({ busy: SessionTable.time_busy, idle: SessionTable.time_idle, updated: SessionTable.time_updated })
+          .from(SessionTable)
+          .get()
+          .pipe(Effect.orDie)
+
+      yield* TestClock.setTime(10)
+      yield* bus.publish(SessionEvent.Execution.Started, { sessionID })
+      expect(yield* times()).toEqual({ busy: 10, idle: null, updated: 0 })
+
+      yield* TestClock.setTime(20)
+      yield* bus.publish(SessionEvent.Execution.Interrupted, { sessionID, reason: "shutdown" })
+      yield* TestClock.setTime(30)
+      yield* bus.publish(SessionEvent.Execution.Started, { sessionID })
+      expect(yield* times()).toEqual({ busy: 30, idle: null, updated: 0 })
+
+      yield* TestClock.setTime(40)
+      yield* bus.publish(SessionEvent.Execution.Succeeded, { sessionID })
+      expect(yield* times()).toEqual({ busy: 30, idle: 40, updated: 0 })
+
+      yield* TestClock.setTime(50)
+      yield* bus.publish(SessionEvent.Execution.Started, { sessionID })
+      expect(yield* times()).toEqual({ busy: 50, idle: 40, updated: 0 })
+    }),
+  )
+
   it.effect("updates only the newest incomplete assistant projection", () =>
     Effect.gen(function* () {
       const db = yield* seedSession()
diff --git a/packages/core/test/v1-migration.test.ts b/packages/core/test/v1-migration.test.ts
index 2bd411e9a439..adf925d076d6 100644
--- a/packages/core/test/v1-migration.test.ts
+++ b/packages/core/test/v1-migration.test.ts
@@ -66,6 +66,7 @@ const session = (
   model: null,
   time_created: 1,
   time_updated: 2,
+  time_busy: null,
   time_idle: null,
   time_viewed: null,
   idle_outcome: null,
diff --git a/packages/protocol/openapi.json b/packages/protocol/openapi.json
index 3d971b8dd7e8..082023339ecb 100644
--- a/packages/protocol/openapi.json
+++ b/packages/protocol/openapi.json
@@ -21856,6 +21856,9 @@
               "updated": {
                 "type": "number"
               },
+              "busy": {
+                "type": "number"
+              },
               "idle": {
                 "type": "number"
               },
diff --git a/packages/schema/src/session.ts b/packages/schema/src/session.ts
index 9f6cd0d71b0c..b03d42cf2965 100644
--- a/packages/schema/src/session.ts
+++ b/packages/schema/src/session.ts
@@ -46,6 +46,9 @@ export const Info = Schema.Struct({
   time: Schema.Struct({
     created: DateTimeUtcFromMillis,
     updated: DateTimeUtcFromMillis,
+    /** Start of the most recent execution. While it runs, `idle` still holds the previous execution's end. Resuming after a restart starts a new execution. */
+    busy: DateTimeUtcFromMillis.pipe(optional),
+    /** End of the most recent completed execution. */
     idle: DateTimeUtcFromMillis.pipe(optional),
     viewed: DateTimeUtcFromMillis.pipe(optional),
     archived: DateTimeUtcFromMillis.pipe(optional),