fix(acp): speed up acp-next warm switches (#29713)

packages/opencode/src/acp-next/service.ts

@@ -83,6 +83,7 @@ export function make(input: {
   const session = input.session ?? makeSessionService()
   const directoryService = input.directory ?? makeDirectoryService(input.sdk)
   const registeredMcp = new Map<string, Set<string>>()
+  const sessionSnapshots = new Map<string, Directory.Snapshot>()
   const events = input.connection
     ? ACPNextEvent.start({ sdk: input.sdk, connection: input.connection, session })
     : undefined
@@ -149,6 +150,14 @@ export function make(input: {
     return snapshot
   })
 
+  const configSnapshot = Effect.fn("ACPNext.configSnapshot")(function* (state: ACPNextSession.Info) {
+    const snapshot = sessionSnapshots.get(state.id)
+    if (snapshot) return snapshot
+    const loaded = yield* directorySnapshot(state.cwd)
+    sessionSnapshots.set(state.id, loaded)
+    return loaded
+  })
+
   const newSession = Effect.fn("ACPNext.newSession")(function* (params: NewSessionRequest) {
     const started = performance.now()
     const snapshot = yield* directorySnapshot(params.cwd)
@@ -180,6 +189,7 @@ export function make(input: {
       variant,
       modeId,
     })
+    sessionSnapshots.set(state.id, snapshot)
 
     yield* registerMcpServers(input.sdk, registeredMcp, params.cwd, state.id, params.mcpServers)
     yield* sendAvailableCommands(input.connection, state.id, snapshot)
@@ -220,6 +230,7 @@ export function make(input: {
       variant: restored.variant ?? selectVariant(snapshot, model),
       modeId: restored.modeId ?? (snapshot.availableModes.length > 0 ? snapshot.defaultModeID : undefined),
     })
+    sessionSnapshots.set(state.id, snapshot)
 
     yield* registerMcpServers(input.sdk, registeredMcp, params.cwd, state.id, params.mcpServers)
     yield* sendAvailableCommands(input.connection, state.id, snapshot)
@@ -290,6 +301,7 @@ export function make(input: {
       variant: restored.variant ?? selectVariant(snapshot, model),
       modeId: restored.modeId ?? (snapshot.availableModes.length > 0 ? snapshot.defaultModeID : undefined),
     })
+    sessionSnapshots.set(state.id, snapshot)
 
     yield* registerMcpServers(input.sdk, registeredMcp, params.cwd, state.id, params.mcpServers ?? [])
     yield* sendAvailableCommands(input.connection, state.id, snapshot)
@@ -307,6 +319,7 @@ export function make(input: {
   const closeSession = Effect.fn("ACPNext.closeSession")(function* (params: CloseSessionRequest) {
     const removed = yield* session.remove(params.sessionId)
     registeredMcp.delete(params.sessionId)
+    sessionSnapshots.delete(params.sessionId)
     if (!removed) return {}
 
     yield* request(
@@ -350,6 +363,7 @@ export function make(input: {
       variant: restored.variant ?? selectVariant(snapshot, model),
       modeId: restored.modeId ?? (snapshot.availableModes.length > 0 ? snapshot.defaultModeID : undefined),
     })
+    sessionSnapshots.set(state.id, snapshot)
 
     yield* registerMcpServers(input.sdk, registeredMcp, params.cwd, state.id, params.mcpServers ?? [])
     yield* sendAvailableCommands(input.connection, state.id, snapshot)
@@ -369,7 +383,7 @@ export function make(input: {
     params: SetSessionConfigOptionRequest,
   ) {
     const current = yield* session.get(params.sessionId)
-    const snapshot = yield* directorySnapshot(current.cwd)
+    const snapshot = yield* configSnapshot(current)
     if (typeof params.value !== "string") {
       return yield* new ACPNextError.InvalidConfigOptionError({ configId: params.configId })
     }
@@ -424,7 +438,7 @@ export function make(input: {
 
   const setSessionMode = Effect.fn("ACPNext.setSessionMode")(function* (params: SetSessionModeRequest) {
     const current = yield* session.get(params.sessionId)
-    const snapshot = yield* directorySnapshot(current.cwd)
+    const snapshot = yield* configSnapshot(current)
     if (!snapshot.availableModes.some((mode) => mode.id === params.modeId)) {
       return yield* new ACPNextError.InvalidModeError({ mode: params.modeId })
     }
@@ -434,7 +448,7 @@ export function make(input: {
 
   const setSessionModel = Effect.fn("ACPNext.setSessionModel")(function* (params: SetSessionModelRequest) {
     const current = yield* session.get(params.sessionId)
-    const snapshot = yield* directorySnapshot(current.cwd)
+    const snapshot = yield* configSnapshot(current)
     const selected = yield* parseSelectedModel(snapshot, params.modelId)
     yield* session
       .setVariant(

packages/opencode/test/acp-next/service-session.test.ts

@@ -707,24 +707,35 @@ describe("ACP next service sessions", () => {
     expect(results.map((error) => error.code)).toEqual([-32602, -32602, -32602, -32602])
   })
 
-  it("does not reload providers or commands when switching effort from a warm snapshot", async () => {
-    let providersCalls = 0
-    let commandCalls = 0
+  it("does not refetch providers modes or commands when switching effort from session snapshot", async () => {
+    const calls = {
+      providers: 0,
+      agents: 0,
+      commands: 0,
+      skills: 0,
+      mcpAdds: 0,
+    }
     const sdk = {
       config: {
         providers: () => {
-          providersCalls++
+          calls.providers++
           return Promise.resolve({ data: { providers: [provider], default: { test: modelID } } })
         },
         get: () => Promise.resolve({ data: {} }),
       },
       app: {
-        agents: () => Promise.resolve({ data: [{ name: "build", mode: "primary", permission: [], options: {} }] }),
-        skills: () => Promise.resolve({ data: [] }),
+        agents: () => {
+          calls.agents++
+          return Promise.resolve({ data: [{ name: "build", mode: "primary", permission: [], options: {} }] })
+        },
+        skills: () => {
+          calls.skills++
+          return Promise.resolve({ data: [] })
+        },
       },
       command: {
         list: () => {
-          commandCalls++
+          calls.commands++
           return Promise.resolve({ data: [] })
         },
       },
@@ -733,14 +744,16 @@ describe("ACP next service sessions", () => {
         list: () => Promise.resolve({ data: [] }),
       },
       mcp: {
-        add: () => Promise.resolve({ data: {} }),
+        add: () => {
+          calls.mcpAdds++
+          return Promise.resolve({ data: {} })
+        },
       },
     } as unknown as OpencodeClient
     const service = ACPNextService.make({ sdk })
     const session = await Effect.runPromise(service.newSession({ cwd: "/workspace", mcpServers: [] }))
 
-    expect(providersCalls).toBe(1)
-    expect(commandCalls).toBe(1)
+    expect(calls).toEqual({ providers: 1, agents: 1, commands: 1, skills: 1, mcpAdds: 0 })
 
     await Effect.runPromise(
       service.setSessionConfigOption({
@@ -750,8 +763,135 @@ describe("ACP next service sessions", () => {
       }),
     )
 
-    expect(providersCalls).toBe(1)
-    expect(commandCalls).toBe(1)
+    expect(calls).toEqual({ providers: 1, agents: 1, commands: 1, skills: 1, mcpAdds: 0 })
+  })
+
+  it("switches model against the warm provider snapshot without refetching", async () => {
+    const calls = {
+      providers: 0,
+      agents: 0,
+      commands: 0,
+      skills: 0,
+    }
+    const sdk = {
+      config: {
+        providers: () => {
+          calls.providers++
+          return Promise.resolve({ data: { providers: [provider], default: { test: modelID } } })
+        },
+        get: () => Promise.resolve({ data: {} }),
+      },
+      app: {
+        agents: () => {
+          calls.agents++
+          return Promise.resolve({ data: [{ name: "build", mode: "primary", permission: [], options: {} }] })
+        },
+        skills: () => {
+          calls.skills++
+          return Promise.resolve({ data: [] })
+        },
+      },
+      command: {
+        list: () => {
+          calls.commands++
+          return Promise.resolve({ data: [] })
+        },
+      },
+      session: {
+        create: () => Promise.resolve({ data: { id: "ses_model_fast" } }),
+        list: () => Promise.resolve({ data: [] }),
+      },
+      mcp: {
+        add: () => Promise.resolve({ data: {} }),
+      },
+    } as unknown as OpencodeClient
+    const service = ACPNextService.make({ sdk })
+    const session = await Effect.runPromise(service.newSession({ cwd: "/workspace", mcpServers: [] }))
+    const updated = await Effect.runPromise(
+      service.setSessionConfigOption({
+        sessionId: session.sessionId,
+        configId: "model",
+        value: "test/second-model",
+      }),
+    )
+
+    expect(select(updated, "model")?.currentValue).toBe("test/second-model")
+    expect(calls).toEqual({ providers: 1, agents: 1, commands: 1, skills: 1 })
+  })
+
+  it("reuses the warm directory snapshot for a second new session in the same cwd", async () => {
+    const calls = {
+      providers: 0,
+      config: 0,
+      agents: 0,
+      commands: 0,
+      skills: 0,
+      sessionList: 0,
+      messages: 0,
+      creates: 0,
+    }
+    const sdk = {
+      config: {
+        providers: () => {
+          calls.providers++
+          return Promise.resolve({ data: { providers: [provider], default: { test: modelID } } })
+        },
+        get: () => {
+          calls.config++
+          return Promise.resolve({ data: {} })
+        },
+      },
+      app: {
+        agents: () => {
+          calls.agents++
+          return Promise.resolve({ data: [{ name: "build", mode: "primary", permission: [], options: {} }] })
+        },
+        skills: () => {
+          calls.skills++
+          return Promise.resolve({ data: [] })
+        },
+      },
+      command: {
+        list: () => {
+          calls.commands++
+          return Promise.resolve({ data: [] })
+        },
+      },
+      session: {
+        create: () => {
+          calls.creates++
+          return Promise.resolve({ data: { id: `ses_warm_${calls.creates}` } })
+        },
+        list: () => {
+          calls.sessionList++
+          return Promise.resolve({ data: [] })
+        },
+        messages: () => {
+          calls.messages++
+          return Promise.resolve({ data: [] })
+        },
+      },
+      mcp: {
+        add: () => Promise.resolve({ data: {} }),
+      },
+    } as unknown as OpencodeClient
+    const service = ACPNextService.make({ sdk })
+
+    const first = await Effect.runPromise(service.newSession({ cwd: "/workspace", mcpServers: [] }))
+    const second = await Effect.runPromise(service.newSession({ cwd: "/workspace", mcpServers: [] }))
+
+    expect(first.sessionId).toBe("ses_warm_1")
+    expect(second.sessionId).toBe("ses_warm_2")
+    expect(calls).toEqual({
+      providers: 1,
+      config: 1,
+      agents: 1,
+      commands: 1,
+      skills: 1,
+      sessionList: 0,
+      messages: 0,
+      creates: 2,
+    })
   })
 
   it("normal text prompt sends model variant mode and converted parts", async () => {

packages/opencode/test/cli/acp-next/timing-diagnostics.test.ts

@@ -42,7 +42,7 @@ describe("opencode acp-next verifier timing diagnostics", () => {
   )
 
   cliIt.live(
-    "warm new session timing diagnostic stays below generous threshold",
+    "warm new session stays below verifier threshold",
     ({ home, llm, opencode }) =>
       Effect.gen(function* () {
         const acp = yield* createAcpNextClient(
@@ -57,15 +57,13 @@ describe("opencode acp-next verifier timing diagnostics", () => {
         const durationMs = Math.round(performance.now() - started)
 
         expect(session.sessionId).toBeTruthy()
-        // TODO: replace this diagnostic assertion with finalFastPathThresholdMs.
-        expect(durationMs).toBeLessThan(diagnosticFastPathThresholdMs)
-        expect(finalFastPathThresholdMs).toBe(100)
+        expect(durationMs).toBeLessThan(finalFastPathThresholdMs)
       }),
     60_000,
   )
 
   cliIt.live(
-    "model switch timing diagnostic updates currentValue below generous threshold",
+    "model switch updates currentValue below verifier threshold",
     ({ home, llm, opencode }) =>
       Effect.gen(function* () {
         const acp = yield* createAcpNextClient(
@@ -89,14 +87,13 @@ describe("opencode acp-next verifier timing diagnostics", () => {
         const durationMs = Math.round(performance.now() - started)
 
         expect(expectSelectOption(updated.configOptions, "model").currentValue).toBe(nextModel)
-        // TODO: replace this diagnostic assertion with finalFastPathThresholdMs.
-        expect(durationMs).toBeLessThan(diagnosticFastPathThresholdMs)
+        expect(durationMs).toBeLessThan(finalFastPathThresholdMs)
       }),
     60_000,
   )
 
   cliIt.live(
-    "effort switch timing diagnostic updates currentValue below generous threshold",
+    "effort switch updates currentValue below verifier threshold",
     ({ home, llm, opencode }) =>
       Effect.gen(function* () {
         const acp = yield* createAcpNextClient(
@@ -118,8 +115,7 @@ describe("opencode acp-next verifier timing diagnostics", () => {
         const durationMs = Math.round(performance.now() - started)
 
         expect(expectSelectOption(updated.configOptions, "effort").currentValue).toBe(nextEffort)
-        // TODO: replace this diagnostic assertion with finalFastPathThresholdMs.
-        expect(durationMs).toBeLessThan(diagnosticFastPathThresholdMs)
+        expect(durationMs).toBeLessThan(finalFastPathThresholdMs)
       }),
     60_000,
   )