feat(tui): add centered session width

packages/ai/src/route/executor.ts

@@ -297,7 +297,7 @@ export const classifyHttpFailure = (input: {
   })
 }
 
-export const mapHttpError = (error: unknown, redactedNames: ReadonlyArray<string | RegExp>) => {
+const toHttpError = (redactedNames: ReadonlyArray<string | RegExp>) => (error: unknown) => {
   const transportError = (input: {
     readonly message: string
     readonly kind?: string | undefined
@@ -314,35 +314,23 @@ export const mapHttpError = (error: unknown, redactedNames: ReadonlyArray<string
       }),
     })
 
-  const cause =
-    HttpClientError.isHttpClientError(error) && "cause" in error.reason
-      ? error.reason.cause
-      : error instanceof Error
-        ? error.cause
-        : undefined
-  const code = [cause, error]
-    .map((value) => (typeof value === "object" && value !== null ? Reflect.get(value, "code") : undefined))
-    .find((value): value is string => typeof value === "string")
-  const request = HttpClientError.isHttpClientError(error) && "request" in error ? error.request : undefined
-  const raw = cause instanceof Error ? cause.message : error instanceof Error ? error.message : undefined
-  const detail = raw && request ? redactBody(raw, secretValues(request)) : raw
-  const message = code && detail && !detail.includes(code) ? `${code}: ${detail}` : detail
-
-  if (Cause.isTimeoutError(error) || Cause.isTimeoutError(cause))
-    return transportError({ message: message ?? "HTTP transport timed out", kind: code ?? "Timeout", request })
-  if (!HttpClientError.isHttpClientError(error)) {
-    return transportError({ message: message ?? "HTTP transport failed", kind: code, request })
+  if (Cause.isTimeoutError(error)) {
+    return transportError({ message: error.message, kind: "Timeout" })
   }
+  if (!HttpClientError.isHttpClientError(error)) {
+    return transportError({ message: error instanceof Error ? error.message : "HTTP transport failed" })
+  }
+  const request = "request" in error ? error.request : undefined
   if (error.reason._tag === "TransportError") {
     return transportError({
-      message: message ?? error.reason.description ?? "HTTP transport failed",
-      kind: code ?? error.reason._tag,
+      message: error.reason.description ?? "HTTP transport failed",
+      kind: error.reason._tag,
       request,
     })
   }
   return transportError({
-    message: message ?? `HTTP transport failed: ${error.reason._tag}`,
-    kind: code ?? error.reason._tag,
+    message: `HTTP transport failed: ${error.reason._tag}`,
+    kind: error.reason._tag,
     request,
   })
 }
@@ -355,16 +343,15 @@ export const layer: Layer.Layer<Service, never, HttpClient.HttpClient> = Layer.e
       Effect.gen(function* () {
         const redactedNames = yield* Headers.CurrentRedactedNames
         if (!middleware)
-          return yield* http.execute(request).pipe(
-            Effect.mapError((error) => mapHttpError(error, redactedNames)),
-            Effect.flatMap(statusError(request, redactedNames)),
-          )
+          return yield* http
+            .execute(request)
+            .pipe(Effect.mapError(toHttpError(redactedNames)), Effect.flatMap(statusError(request, redactedNames)))
 
         const response = yield* middleware(request, (input) =>
           http
             .execute(input)
             .pipe(Effect.mapError((cause) => (cause instanceof Error ? cause : new Error(String(cause))))),
-        ).pipe(Effect.mapError((error) => mapHttpError(error, redactedNames)))
+        ).pipe(Effect.mapError(toHttpError(redactedNames)))
         return yield* statusError(response.request, redactedNames)(response)
       })
     return Service.of({

packages/ai/src/route/transport/http.ts

@@ -2,7 +2,6 @@ import { Effect, Stream } from "effect"
 import { Headers, HttpClientRequest } from "effect/unstable/http"
 import { Auth } from "../auth"
 import { render as renderEndpoint } from "../endpoint"
-import { mapHttpError } from "../executor"
 import { Framing } from "../framing"
 import type { HttpMiddleware, Transport, TransportPrepareInput } from "./index"
 import * as ProviderShared from "../../protocols/shared"
@@ -87,16 +86,20 @@ export const httpJson = <Body, Frame>(input: HttpJsonInput<Body, Frame>): HttpJs
         middleware: prepareInput.middleware,
       }
     }),
-  frames: (prepared, _request, runtime) =>
+  frames: (prepared, request, runtime) =>
     Stream.unwrap(
       runtime.http
         .execute(prepared.request, prepared.middleware)
         .pipe(
           Effect.map((response) =>
-            Stream.unwrap(
-              Effect.map(Headers.CurrentRedactedNames, (redactedNames) =>
-                prepared.framing.frame(
-                  response.stream.pipe(Stream.mapError((error) => mapHttpError(error, redactedNames))),
+            prepared.framing.frame(
+              response.stream.pipe(
+                Stream.mapError((error) =>
+                  ProviderShared.eventError(
+                    `${request.model.provider}/${request.model.route.id}`,
+                    `Failed to read ${request.model.provider}/${request.model.route.id} stream`,
+                    ProviderShared.errorText(error),
+                  ),
                 ),
               ),
             ),

packages/ai/test/lib/http.ts

@@ -63,14 +63,14 @@ export const dynamicResponse = (handler: Handler) => runtimeLayer(handlerLayer(h
  * Layer that emits the supplied SSE chunks and then aborts mid-stream. Used to
  * exercise transport errors that surface during parsing.
  */
-export const truncatedStream = (chunks: ReadonlyArray<string>, error: Error = new Error("connection reset")) =>
+export const truncatedStream = (chunks: ReadonlyArray<string>) =>
   dynamicResponse((input) =>
     Effect.sync(() => {
       const encoder = new TextEncoder()
       const stream = new ReadableStream({
         start(controller) {
           for (const chunk of chunks) controller.enqueue(encoder.encode(chunk))
-          controller.error(error)
+          controller.error(new Error("connection reset"))
         },
       })
       return input.respond(stream, { headers: SSE_HEADERS })

packages/ai/test/provider/openai-chat.test.ts

@@ -1221,18 +1221,12 @@ describe("OpenAI Chat route", () => {
 
   it.effect("surfaces transport errors that occur mid-stream", () =>
     Effect.gen(function* () {
-      const layer = truncatedStream(
-        [`data: ${JSON.stringify(deltaChunk({ role: "assistant", content: "Hello" }))}\n\n`],
-        Object.assign(new Error("socket closed unexpectedly"), { code: "ECONNRESET" }),
-      )
+      const layer = truncatedStream([
+        `data: ${JSON.stringify(deltaChunk({ role: "assistant", content: "Hello" }))}\n\n`,
+      ])
       const error = yield* LLMClient.generate(request).pipe(Effect.provide(layer), Effect.flip)
 
-      expect(error.reason).toMatchObject({
-        _tag: "Transport",
-        message: "ECONNRESET: socket closed unexpectedly",
-        kind: "ECONNRESET",
-        url: "https://api.openai.test/v1/chat/completions",
-      })
+      expect(error.message).toContain("Failed to read openai/openai-chat stream")
     }),
   )
 

packages/app/src/context/server-session-v2-reducer.test.ts

@@ -69,63 +69,6 @@ describe("v2 session reducer", () => {
     })
   })
 
-  test("prefers durable selection predecessors and derives them for older events", () => {
-    const source: SessionMessageInfo[] = [
-      { id: "msg_previous_agent", type: "agent-switched", agent: "build", time: { created: 1 } },
-      {
-        id: "msg_previous_model",
-        type: "model-switched",
-        model: { id: "old", providerID: "provider" },
-        time: { created: 1 },
-      },
-    ]
-    const reducer = createV2SessionReducer()
-
-    const agent = reducer.reduce(
-      source,
-      event({
-        ...base,
-        id: "evt_agent",
-        type: "session.agent.selected",
-        data: { sessionID: "ses_1", agent: "plan", previous: "review" },
-      }),
-    )
-    const model = reducer.reduce(
-      source,
-      event({
-        ...base,
-        id: "evt_model",
-        type: "session.model.selected",
-        data: {
-          sessionID: "ses_1",
-          model: { id: "new", providerID: "provider" },
-          previous: { id: "durable", providerID: "provider" },
-        },
-      }),
-    )
-    const legacyAgent = reducer.reduce(
-      source,
-      event({
-        ...base,
-        id: "evt_legacy_agent",
-        type: "session.agent.selected",
-        data: { sessionID: "ses_1", agent: "plan" },
-      }),
-    )
-
-    expect(agent?.messages.at(-1)).toMatchObject({ type: "agent-switched", agent: "plan", previous: "review" })
-    expect(model?.messages.at(-1)).toMatchObject({
-      type: "model-switched",
-      model: { id: "new" },
-      previous: { id: "durable" },
-    })
-    expect(legacyAgent?.messages.at(-1)).toMatchObject({
-      type: "agent-switched",
-      agent: "plan",
-      previous: "build",
-    })
-  })
-
   test("folds tool, retry, and completion events", () => {
     const reducer = createV2SessionReducer()
     let messages: SessionMessageInfo[] = []

packages/app/src/context/server-session-v2-reducer.ts

@@ -61,12 +61,6 @@ export function createV2SessionReducer() {
           type: "agent-switched",
           metadata: event.metadata,
           agent: event.data.agent,
-          previous:
-            event.data.previous ??
-            source.findLast(
-              (item): item is Extract<SessionMessageInfo, { type: "agent-switched" | "assistant" }> =>
-                item.type === "agent-switched" || item.type === "assistant",
-            )?.agent,
           time: { created: event.created },
         })
       case "session.model.selected":
@@ -75,12 +69,10 @@ export function createV2SessionReducer() {
           type: "model-switched",
           metadata: event.metadata,
           model: event.data.model,
-          previous:
-            event.data.previous ??
-            source.findLast(
-              (item): item is Extract<SessionMessageInfo, { type: "model-switched" | "assistant" }> =>
-                item.type === "model-switched" || item.type === "assistant",
-            )?.model,
+          previous: source.findLast(
+            (item): item is Extract<SessionMessageInfo, { type: "model-switched" | "assistant" }> =>
+              item.type === "model-switched" || item.type === "assistant",
+          )?.model,
           time: { created: event.created },
         })
       case "session.synthetic":

packages/client/src/effect/api/api.ts

@@ -339,11 +339,7 @@ export type Endpoint5_31Output =
           readonly type: "session.agent.selected"
           readonly durable: { readonly aggregateID: string; readonly seq: Event.Seq; readonly version: Event.Version }
           readonly location?: Location.Ref | undefined
-          readonly data: {
-            readonly sessionID: Session.ID
-            readonly agent: Agent.ID
-            readonly previous?: Agent.ID | undefined
-          }
+          readonly data: { readonly sessionID: Session.ID; readonly agent: Agent.ID }
         }
       | {
           readonly id: Event.ID
@@ -352,11 +348,7 @@ export type Endpoint5_31Output =
           readonly type: "session.model.selected"
           readonly durable: { readonly aggregateID: string; readonly seq: Event.Seq; readonly version: Event.Version }
           readonly location?: Location.Ref | undefined
-          readonly data: {
-            readonly sessionID: Session.ID
-            readonly model: Model.Ref
-            readonly previous?: Model.Ref | undefined
-          }
+          readonly data: { readonly sessionID: Session.ID; readonly model: Model.Ref }
         }
       | {
           readonly id: Event.ID

packages/client/src/promise/generated/types.ts

@@ -436,7 +436,7 @@ export type SessionAgentSelected = {
   type: "session.agent.selected"
   durable: { aggregateID: string; seq: number; version: 1 }
   location?: LocationRef
-  data: { sessionID: string; agent: string; previous?: string }
+  data: { sessionID: string; agent: string }
 }
 
 export type SessionModelSelected = {
@@ -446,7 +446,7 @@ export type SessionModelSelected = {
   type: "session.model.selected"
   durable: { aggregateID: string; seq: number; version: 1 }
   location?: LocationRef
-  data: { sessionID: string; model: ModelRef; previous?: ModelRef }
+  data: { sessionID: string; model: ModelRef }
 }
 
 export type SessionMoved = {

packages/core/src/session.ts

@@ -716,11 +716,10 @@ const layer = Layer.effect(
             .pipe(Effect.ignore, Effect.forkIn(scope, { startImmediately: true }), Effect.asVoid)
       }),
       switchAgent: Effect.fn("Session.switchAgent")(function* (input) {
-        const session = yield* result.get(input.sessionID)
+        yield* result.get(input.sessionID)
         yield* bus.publish(SessionEvent.AgentSelected, {
           sessionID: input.sessionID,
           agent: input.agent,
-          previous: session.agent,
         })
       }),
       switchModel: Effect.fn("Session.switchModel")(function* (input) {
@@ -734,7 +733,6 @@ const layer = Layer.effect(
         yield* bus.publish(SessionEvent.ModelSelected, {
           sessionID: input.sessionID,
           model: input.model,
-          previous: session.model,
         })
       }),
       rename: Effect.fn("Session.rename")(function* (input) {

packages/core/src/session/message-updater.ts

@@ -61,7 +61,7 @@ export function update(adapter: Adapter, event: SessionEvent.DurableEvent) {
       "session.usage.recorded": () => Effect.void,
       "session.agent.selected": (event) => {
         return Effect.gen(function* () {
-          const previous = event.data.previous ?? (yield* adapter.getAgent())
+          const previous = yield* adapter.getAgent()
           yield* adapter.appendMessage(
             SessionMessage.AgentSelected.make({
               id: SessionMessage.ID.fromEvent(event.id),
@@ -76,7 +76,7 @@ export function update(adapter: Adapter, event: SessionEvent.DurableEvent) {
       },
       "session.model.selected": (event) => {
         return Effect.gen(function* () {
-          const previous = event.data.previous ?? (yield* adapter.getModel())
+          const previous = yield* adapter.getModel()
           yield* adapter.appendMessage(
             SessionMessage.ModelSelected.make({
               id: SessionMessage.ID.fromEvent(event.id),

packages/core/test/session-create.test.ts

@@ -654,7 +654,7 @@ describe("Session.create", () => {
       expect(yield* session.get(created.id)).toMatchObject({ agent: "plan" })
       expect(
         Array.from(yield* logEvents(session, created.id, true).pipe(Stream.drop(1), Stream.take(1), Stream.runCollect)),
-      ).toMatchObject([{ type: "session.agent.selected", data: { agent: "plan", previous: "build" } }])
+      ).toMatchObject([{ type: "session.agent.selected", data: { agent: "plan" } }])
       expect(yield* session.messages({ sessionID: created.id, order: "asc" })).toMatchObject([
         { type: "agent-switched", agent: "plan", previous: "build" },
       ])
@@ -678,12 +678,7 @@ describe("Session.create", () => {
   it.effect("switches the selected model through the durable Session event", () =>
     Effect.gen(function* () {
       const session = yield* Session.Service
-      const previous = Model.Ref.make({
-        id: Model.ID.make("haiku"),
-        providerID: Provider.ID.anthropic,
-        variant: Model.VariantID.make("default"),
-      })
-      const created = yield* session.create({ location, model: previous })
+      const created = yield* session.create({ location })
       const model = Model.Ref.make({
         id: Model.ID.make("sonnet"),
         providerID: Provider.ID.anthropic,
@@ -697,10 +692,7 @@ describe("Session.create", () => {
         yield* logEvents(session, created.id, true).pipe(Stream.drop(1), Stream.take(1), Stream.runCollect),
       )
       expect(bus).toMatchObject([{ type: "session.model.selected" }])
-      expect(bus[0]?.data).toEqual({ sessionID: created.id, model, previous })
-      expect(yield* session.messages({ sessionID: created.id, order: "asc" })).toMatchObject([
-        { type: "model-switched", model, previous },
-      ])
+      expect(bus[0]?.data).toEqual({ sessionID: created.id, model })
     }),
   )
 

packages/protocol/openapi.json

@@ -14373,9 +14373,6 @@
               },
               "agent": {
                 "type": "string"
-              },
-              "previous": {
-                "type": "string"
               }
             },
             "required": ["sessionID", "agent"],
@@ -14444,9 +14441,6 @@
               },
               "model": {
                 "$ref": "#/components/schemas/Model.Ref"
-              },
-              "previous": {
-                "$ref": "#/components/schemas/Model.Ref"
               }
             },
             "required": ["sessionID", "model"],

packages/schema/src/session-event.ts

@@ -69,7 +69,6 @@ export const AgentSelected = Event.durable({
   schema: {
     ...Base,
     agent: Agent.ID,
-    previous: Agent.ID.pipe(optional),
   },
 })
 export type AgentSelected = typeof AgentSelected.Type
@@ -80,7 +79,6 @@ export const ModelSelected = Event.durable({
   schema: {
     ...Base,
     model: Model.Ref,
-    previous: Model.Ref.pipe(optional),
   },
 })
 export type ModelSelected = typeof ModelSelected.Type

packages/tui/src/component/dialog-config.tsx

@@ -60,6 +60,15 @@ export const settings: Setting[] = [
     labels: ["off", "on"],
     keywords: ["scroll bar"],
   },
+  {
+    title: "Max width",
+    category: "Session",
+    path: ["session", "max_width"],
+    default: "auto",
+    values: ["auto", 80, 100, 120],
+    labels: ["auto", "80 columns", "100 columns", "120 columns"],
+    keywords: ["transcript", "composer", "centered", "reading width"],
+  },
   {
     title: "Thinking",
     category: "Session",

packages/tui/src/config/index.tsx

@@ -125,6 +125,11 @@ export const Info = Schema.Struct({
         description: "Session sidebar visibility; 'auto' shows it when space permits",
       }),
       scrollbar: Schema.optional(Schema.Boolean).annotate({ description: "Show the session transcript scrollbar" }),
+      max_width: Schema.optional(
+        Schema.Union([Schema.Int.check(Schema.isGreaterThan(4)), Schema.Literal("auto")]),
+      ).annotate({
+        description: "Session transcript and composer max width, or 'auto' to use the available width",
+      }),
       thinking: Schema.optional(Schema.Literals(["show", "hide"])).annotate({
         description: "Show or hide model reasoning by default",
       }),

packages/tui/src/routes/session/index.tsx

@@ -68,7 +68,7 @@ import { errorMessage } from "../../util/error"
 import { useToast } from "../../ui/toast"
 import stripAnsi from "strip-ansi"
 import { usePromptRef } from "../../context/prompt"
-import { sessionTabsFitVertically, SESSION_SIDEBAR_WIDTH } from "../../ui/layout"
+import { sessionContentWidth, sessionTabsFitVertically, SESSION_SIDEBAR_WIDTH } from "../../ui/layout"
 import { projectedPromptInput } from "../../prompt/codec"
 import { deduplicateVisibleImages } from "../../prompt/attachment"
 import { useEpilogue } from "../../context/epilogue"
@@ -225,6 +225,7 @@ export function Session() {
   const thinkingMode = createMemo<ThinkingMode>(() => config.session?.thinking ?? "hide")
   const showThinking = createMemo(() => true)
   const showScrollbar = createMemo(() => config.session?.scrollbar ?? false)
+  const maxWidth = createMemo(() => config.session?.max_width ?? "auto")
   const markdownMode = createMemo(() => config.session?.markdown ?? "rendered")
   const diffWrapMode = createMemo(() => config.diffs?.wrap ?? "word")
   const groupExploration = createMemo(() => config.session?.grouping !== "none")
@@ -243,7 +244,7 @@ export function Session() {
     if (sidebar() === "auto" && wide()) return true
     return false
   })
-  const contentWidth = createMemo(() => availableWidth() - (sidebarVisible() ? 42 : 0) - 4)
+  const contentWidth = createMemo(() => sessionContentWidth(availableWidth(), sidebarVisible(), maxWidth()))
   const models = createMemo(() => data.location.model.list(location()) ?? [])
 
   const scrollAcceleration = createMemo(() => getScrollAcceleration(config))
@@ -1037,103 +1038,107 @@ export function Session() {
       }}
     >
       <box flexDirection="row" flexGrow={1} minHeight={0}>
-        <box
-          flexGrow={1}
-          minHeight={0}
-          paddingBottom={1}
-          paddingLeft={dimensions().width < 44 ? 1 : 2}
-          paddingRight={dimensions().width < 44 ? 1 : 2}
-          gap={1}
-        >
-          <Show when={session()}>
-            <scrollbox
-              ref={(r) => (scroll = r)}
-              viewportOptions={{
-                paddingRight: showScrollbar() ? 1 : 0,
-              }}
-              verticalScrollbarOptions={{
-                paddingLeft: 1,
-                visible: showScrollbar(),
-                trackOptions: {
-                  backgroundColor: theme.raise(theme.background.surface.offset),
-                  foregroundColor: theme.border.default,
-                },
-              }}
-              stickyScroll={!navigationMessage()}
-              stickyStart="bottom"
-              flexGrow={1}
-              scrollAcceleration={scrollAcceleration()}
-            >
-              <For each={visibleRows()}>
-                {(row, index) => (
-                  <SessionRowView
-                    row={row}
-                    message={(messageID) => data.session.message.get(route.sessionID, messageID)}
-                    boundaryID={boundaries()[index() + hidden()]}
+        <box flexGrow={1} minHeight={0} alignItems="center">
+          <box
+            width="100%"
+            maxWidth={maxWidth() === "auto" ? undefined : maxWidth()}
+            flexGrow={1}
+            minHeight={0}
+            paddingBottom={1}
+            paddingLeft={dimensions().width < 44 ? 1 : 2}
+            paddingRight={dimensions().width < 44 ? 1 : 2}
+            gap={1}
+          >
+            <Show when={session()}>
+              <scrollbox
+                ref={(r) => (scroll = r)}
+                viewportOptions={{
+                  paddingRight: showScrollbar() ? 1 : 0,
+                }}
+                verticalScrollbarOptions={{
+                  paddingLeft: 1,
+                  visible: showScrollbar(),
+                  trackOptions: {
+                    backgroundColor: theme.raise(theme.background.surface.offset),
+                    foregroundColor: theme.border.default,
+                  },
+                }}
+                stickyScroll={!navigationMessage()}
+                stickyStart="bottom"
+                flexGrow={1}
+                scrollAcceleration={scrollAcceleration()}
+              >
+                <For each={visibleRows()}>
+                  {(row, index) => (
+                    <SessionRowView
+                      row={row}
+                      message={(messageID) => data.session.message.get(route.sessionID, messageID)}
+                      boundaryID={boundaries()[index() + hidden()]}
+                    />
+                  )}
+                </For>
+                <BackgroundToolHint messages={messages()} />
+                <Show when={session()?.revert?.messageID}>
+                  <RevertMessage
+                    count={messagesFromRevert().filter((message) => message.type === "user").length}
+                    files={session()!.revert!.files ?? []}
                   />
-                )}
-              </For>
-              <BackgroundToolHint messages={messages()} />
-              <Show when={session()?.revert?.messageID}>
-                <RevertMessage
-                  count={messagesFromRevert().filter((message) => message.type === "user").length}
-                  files={session()!.revert!.files ?? []}
+                </Show>
+                <Show when={navigationSlack()}>
+                  {(height) => <box id={NAVIGATION_SLACK_ID} height={height()} flexShrink={0} />}
+                </Show>
+              </scrollbox>
+              <box flexShrink={0}>
+                <Show when={!composer.open && !disabled() && queuedPrompts().length > 0}>
+                  <QueuedPromptDock prompts={queuedPrompts()} onOpen={openQueuedPrompts} />
+                </Show>
+                <PluginSlot name="session.composer.top" input={{ sessionID: route.sessionID }} mode="all" />
+                <Composer
+                  sessionID={route.sessionID}
+                  open={composer.open || (!!session()?.parentID && forms().length === 0)}
+                  defaultTab={composer.tab ?? (session()?.parentID ? "subagents" : undefined)}
+                  onClose={() => setComposer("open", false)}
                 />
-              </Show>
-              <Show when={navigationSlack()}>
-                {(height) => <box id={NAVIGATION_SLACK_ID} height={height()} flexShrink={0} />}
-              </Show>
-            </scrollbox>
-            <box flexShrink={0}>
-              <Show when={!composer.open && !disabled() && queuedPrompts().length > 0}>
-                <QueuedPromptDock prompts={queuedPrompts()} onOpen={openQueuedPrompts} />
-              </Show>
-              <PluginSlot name="session.composer.top" input={{ sessionID: route.sessionID }} mode="all" />
-              <Composer
-                sessionID={route.sessionID}
-                open={composer.open || (!!session()?.parentID && forms().length === 0)}
-                defaultTab={composer.tab ?? (session()?.parentID ? "subagents" : undefined)}
-                onClose={() => setComposer("open", false)}
-              />
-              <Switch>
-                <Match when={composer.open || (!!session()?.parentID && forms().length === 0)}>{null}</Match>
-                <Match when={promptedPermissions().length > 0}>
-                  <Show when={promptedPermissions()[0]?.id} keyed>
-                    {(_) => {
-                      const request = promptedPermissions()[0]
-                      return request ? (
-                        <PermissionPrompt request={request} directory={session()?.location.directory} />
-                      ) : null
-                    }}
-                  </Show>
-                </Match>
-                <Match when={forms().length > 0}>
-                  <Show when={forms()[0]?.id} keyed>
-                    {(_) => {
-                      const form = forms()[0]
-                      return form ? <FormPrompt form={form} /> : null
-                    }}
-                  </Show>
-                </Match>
-                <Match when={!disabled()}>
-                  <Prompt
-                    visible={true}
-                    ref={bind}
-                    disabled={false}
-                    onSubmit={() => {
-                      toBottom()
-                    }}
-                    onEmptySubmit={async () => {
-                      const next = queuedPrompts()[0]
-                      if (!next) return false
-                      return mutatePending("steer", next.id)
-                    }}
-                    sessionID={route.sessionID}
-                  />
-                </Match>
-              </Switch>
-            </box>
-          </Show>
+                <Switch>
+                  <Match when={composer.open || (!!session()?.parentID && forms().length === 0)}>{null}</Match>
+                  <Match when={promptedPermissions().length > 0}>
+                    <Show when={promptedPermissions()[0]?.id} keyed>
+                      {(_) => {
+                        const request = promptedPermissions()[0]
+                        return request ? (
+                          <PermissionPrompt request={request} directory={session()?.location.directory} />
+                        ) : null
+                      }}
+                    </Show>
+                  </Match>
+                  <Match when={forms().length > 0}>
+                    <Show when={forms()[0]?.id} keyed>
+                      {(_) => {
+                        const form = forms()[0]
+                        return form ? <FormPrompt form={form} /> : null
+                      }}
+                    </Show>
+                  </Match>
+                  <Match when={!disabled()}>
+                    <Prompt
+                      visible={true}
+                      ref={bind}
+                      disabled={false}
+                      onSubmit={() => {
+                        toBottom()
+                      }}
+                      onEmptySubmit={async () => {
+                        const next = queuedPrompts()[0]
+                        if (!next) return false
+                        return mutatePending("steer", next.id)
+                      }}
+                      sessionID={route.sessionID}
+                    />
+                  </Match>
+                </Switch>
+              </box>
+            </Show>
+          </box>
         </box>
         <Show when={sidebarVisible()}>
           <Switch>

packages/tui/src/ui/layout.ts

@@ -1,6 +1,13 @@
 export const SESSION_SIDEBAR_WIDTH = 42
 const SESSION_CONTENT_MIN_WIDTH = 44
+const SESSION_CONTENT_PADDING = 4
 
 export function sessionTabsFitVertically(total: number) {
   return total >= SESSION_SIDEBAR_WIDTH + SESSION_CONTENT_MIN_WIDTH
 }
+
+export function sessionContentWidth(total: number, sidebar: boolean, maxWidth: number | "auto" = "auto") {
+  const available = total - (sidebar ? SESSION_SIDEBAR_WIDTH : 0) - SESSION_CONTENT_PADDING
+  if (maxWidth === "auto") return available
+  return Math.max(1, Math.min(available, maxWidth - SESSION_CONTENT_PADDING))
+}

packages/tui/test/config-v2.test.tsx

@@ -27,6 +27,15 @@ test("validates the session tabs setting", () => {
   expect(decode({ session: { image_preview: true } })).toEqual({ session: { image_preview: true } })
 })
 
+test("validates the session max width setting", () => {
+  const decode = Schema.decodeUnknownSync(Info)
+
+  expect(decode({ session: { max_width: "auto" } })).toEqual({ session: { max_width: "auto" } })
+  expect(decode({ session: { max_width: 100 } })).toEqual({ session: { max_width: 100 } })
+  expect(() => decode({ session: { max_width: 4 } })).toThrow()
+  expect(() => decode({ session: { max_width: 100.5 } })).toThrow()
+})
+
 test("resolves nested config and keybind defaults", () => {
   const config = resolve(
     {
@@ -53,6 +62,13 @@ test("shows resolved tab defaults in settings", () => {
   expect(settings.find((setting) => setting.path.join(".") === "tabs.layout")?.default).toBe("horizontal")
 })
 
+test("shows session max width presets in settings", () => {
+  const setting = settings.find((setting) => setting.path.join(".") === "session.max_width")
+
+  expect(setting?.default).toBe("auto")
+  expect(setting?.values).toEqual(["auto", 80, 100, 120])
+})
+
 test("provides config and its host interface", async () => {
   const config = resolve({}, { terminalSuspend: true })
   let current = {}

packages/tui/test/ui/layout.test.ts

@@ -1,8 +1,18 @@
 import { expect, test } from "bun:test"
-import { sessionTabsFitVertically, SESSION_SIDEBAR_WIDTH } from "../../src/ui/layout"
+import { sessionContentWidth, sessionTabsFitVertically, SESSION_SIDEBAR_WIDTH } from "../../src/ui/layout"
 
 test("vertical tabs match the session sidebar and preserve compact content width", () => {
   expect(SESSION_SIDEBAR_WIDTH).toBe(42)
   expect(sessionTabsFitVertically(86)).toBe(true)
   expect(sessionTabsFitVertically(85)).toBe(false)
 })
+
+test("session content uses available width by default", () => {
+  expect(sessionContentWidth(160, false)).toBe(156)
+  expect(sessionContentWidth(160, true)).toBe(114)
+})
+
+test("session content caps wide sessions and preserves narrow sessions", () => {
+  expect(sessionContentWidth(160, false, 100)).toBe(96)
+  expect(sessionContentWidth(80, false, 100)).toBe(76)
+})

packages/www/openapi.json

@@ -14373,9 +14373,6 @@
               },
               "agent": {
                 "type": "string"
-              },
-              "previous": {
-                "type": "string"
               }
             },
             "required": ["sessionID", "agent"],
@@ -14444,9 +14441,6 @@
               },
               "model": {
                 "$ref": "#/components/schemas/Model.Ref"
-              },
-              "previous": {
-                "$ref": "#/components/schemas/Model.Ref"
               }
             },
             "required": ["sessionID", "model"],

packages/www/public/openapi.json

@@ -14373,9 +14373,6 @@
               },
               "agent": {
                 "type": "string"
-              },
-              "previous": {
-                "type": "string"
               }
             },
             "required": ["sessionID", "agent"],
@@ -14444,9 +14441,6 @@
               },
               "model": {
                 "$ref": "#/components/schemas/Model.Ref"
-              },
-              "previous": {
-                "$ref": "#/components/schemas/Model.Ref"
               }
             },
             "required": ["sessionID", "model"],