feat(opencode): add per-session budget limit

packages/core/schema.json

@@ -1,8 +1,8 @@
 {
   "version": "7",
   "dialect": "sqlite",
-  "id": "f14a9b18-8207-487e-a3d3-227e629ba9ad",
-  "prevIds": ["169a0f0f-d58f-479f-b024-fa1c7b9a09db"],
+  "id": "19be7275-7d21-4de7-a12b-2addde7991da",
+  "prevIds": ["f14a9b18-8207-487e-a3d3-227e629ba9ad"],
   "ddl": [
     {
       "name": "workspace",
@@ -1220,6 +1220,16 @@
       "entityType": "columns",
       "table": "session"
     },
+    {
+      "type": "real",
+      "notNull": false,
+      "autoincrement": false,
+      "default": null,
+      "generated": null,
+      "name": "budget",
+      "entityType": "columns",
+      "table": "session"
+    },
     {
       "type": "integer",
       "notNull": true,

packages/core/script/migration.ts

@@ -107,7 +107,7 @@ export default { ...config, out: ${JSON.stringify(output)} }
 
 async function generatedMigrations(directory: string) {
   return (await Array.fromAsync(new Bun.Glob("*/migration.sql").scan({ cwd: directory })))
-    .map((file) => file.split("/")[0])
+    .map((file) => file.split(/[\\/]/)[0])
     .filter((name): name is string => name !== undefined)
     .sort()
 }

packages/core/src/database/migration/20260812223059_session_budget.ts

@@ -0,0 +1,11 @@
+import { Effect } from "effect"
+import type { DatabaseMigration } from "../migration"
+
+export default {
+  id: "20260812223059_session_budget",
+  up(tx) {
+    return Effect.gen(function* () {
+      yield* tx.run(`ALTER TABLE \`session\` ADD \`budget\` real;`)
+    })
+  },
+} satisfies DatabaseMigration.Migration

packages/core/src/database/schema.gen.ts

@@ -196,6 +196,7 @@ export default {
           \`summary_diffs\` text,
           \`metadata\` text,
           \`cost\` real DEFAULT 0 NOT NULL,
+          \`budget\` real,
           \`tokens_input\` integer DEFAULT 0 NOT NULL,
           \`tokens_output\` integer DEFAULT 0 NOT NULL,
           \`tokens_reasoning\` integer DEFAULT 0 NOT NULL,

packages/core/src/session/info.ts

@@ -26,6 +26,7 @@ export function fromRow(row: typeof SessionTable.$inferSelect): SessionSchema.In
         }
       : undefined,
     cost: row.cost,
+    budget: row.budget ?? undefined,
     tokens: {
       input: row.tokens_input,
       output: row.tokens_output,

packages/core/src/session/projector.ts

@@ -60,6 +60,7 @@ function sessionRow(info: SessionV1.SessionInfo): typeof SessionTable.$inferInse
     summary_diffs: info.summary?.diffs ? [...info.summary.diffs] : undefined,
     metadata: info.metadata,
     cost: info.cost ?? 0,
+    budget: info.budget ?? null,
     tokens_input: (info.tokens ?? { input: 0 }).input,
     tokens_output: (info.tokens ?? { output: 0 }).output,
     tokens_reasoning: (info.tokens ?? { reasoning: 0 }).reasoning,

packages/core/src/session/sql.ts

@@ -41,6 +41,7 @@ export const SessionTable = sqliteTable(
     summary_diffs: text({ mode: "json" }).$type<Snapshot.LegacyFileDiff[]>(),
     metadata: text({ mode: "json" }).$type<Record<string, unknown>>(),
     cost: real().notNull().default(0),
+    budget: real(),
     tokens_input: integer().notNull().default(0),
     tokens_output: integer().notNull().default(0),
     tokens_reasoning: integer().notNull().default(0),

packages/opencode/src/server/routes/instance/httpapi/groups/session.ts

@@ -50,6 +50,7 @@ export const UpdatePayload = Schema.Struct({
   title: Schema.optional(Schema.String),
   metadata: Schema.optional(Session.Metadata),
   permission: Schema.optional(PermissionV1.Ruleset),
+  budget: Schema.optional(Schema.NullOr(Schema.Finite)),
   time: Schema.optional(
     Schema.Struct({
       archived: Schema.optional(Session.ArchivedTimestamp),

packages/opencode/src/server/routes/instance/httpapi/handlers/session.ts

@@ -197,6 +197,9 @@ export const sessionHandlers = HttpApiBuilder.group(InstanceHttpApi, "session",
           permission: Permission.merge(current.permission ?? [], ctx.payload.permission),
         })
       }
+      if (ctx.payload.budget !== undefined) {
+        yield* session.setBudget({ sessionID: ctx.params.sessionID, budget: ctx.payload.budget ?? undefined })
+      }
       if (ctx.payload.time?.archived !== undefined) {
         yield* session.setArchived({ sessionID: ctx.params.sessionID, time: ctx.payload.time.archived })
       }

packages/opencode/src/session/processor.ts

@@ -72,6 +72,10 @@ interface ProcessorContext extends Input {
   needsCompaction: boolean
   currentText: SessionV1.TextPart | undefined
   reasoningMap: Record<string, SessionV1.ReasoningPart>
+  baseCost: number
+  budget: number | undefined
+  turnCost: number
+  budgetExceeded: boolean
 }
 
 type StreamEvent = LLMEvent
@@ -100,6 +104,7 @@ const layer = Layer.effect(
       // may execute tools internally before emitting start-step events,
       // so capturing inside the event handler can be too late.
       const initialSnapshot = yield* snapshot.track()
+      const current = yield* session.get(input.sessionID).pipe(Effect.orDie)
       const ctx: ProcessorContext = {
         assistantMessage: input.assistantMessage,
         sessionID: input.sessionID,
@@ -111,6 +116,10 @@ const layer = Layer.effect(
         needsCompaction: false,
         currentText: undefined,
         reasoningMap: {},
+        baseCost: current.cost ?? 0,
+        budget: current.budget,
+        turnCost: 0,
+        budgetExceeded: false,
       }
       let aborted = false
 
@@ -454,6 +463,18 @@ const layer = Layer.effect(
               cost: usage.cost,
             })
             yield* session.updateMessage(ctx.assistantMessage)
+            ctx.turnCost += usage.cost
+            if (ctx.budget !== undefined && ctx.baseCost + ctx.turnCost >= ctx.budget && !ctx.budgetExceeded) {
+              ctx.budgetExceeded = true
+              yield* session.updatePart({
+                id: PartID.ascending(),
+                messageID: ctx.assistantMessage.id,
+                sessionID: ctx.sessionID,
+                type: "text",
+                text: "Session budget reached. Increase the budget to continue.",
+                time: { start: Date.now(), end: Date.now() },
+              })
+            }
             if (ctx.snapshot) {
               const patch = yield* snapshot.patch(ctx.snapshot)
               if (patch.files.length) {
@@ -677,7 +698,7 @@ const layer = Layer.effect(
           )
 
           if (ctx.needsCompaction) return "compact"
-          if (ctx.blocked || ctx.assistantMessage.error) return "stop"
+          if (ctx.budgetExceeded || ctx.blocked || ctx.assistantMessage.error) return "stop"
           return "continue"
         })
       })

packages/opencode/src/session/prompt.ts

@@ -1129,6 +1129,12 @@ const layer = Layer.effect(
             break
           }
 
+          const sessionState = yield* sessions.get(sessionID).pipe(Effect.orDie)
+          if (sessionState.budget !== undefined && (sessionState.cost ?? 0) >= sessionState.budget) {
+            yield* status.set(sessionID, { type: "idle" })
+            break
+          }
+
           step++
           if (step === 1)
             yield* title({

packages/opencode/src/session/session.ts

@@ -95,6 +95,7 @@ export function fromRow(row: SessionRow): Info {
     version: row.version,
     summary,
     cost: row.cost,
+    budget: row.budget ?? undefined,
     tokens: {
       input: row.tokens_input,
       output: row.tokens_output,
@@ -137,6 +138,7 @@ export function toRow(info: Info) {
     summary_diffs: info.summary?.diffs,
     metadata: info.metadata,
     cost: info.cost ?? 0,
+    budget: info.budget ?? null,
     tokens_input: (info.tokens ?? EmptyTokens).input,
     tokens_output: (info.tokens ?? EmptyTokens).output,
     tokens_reasoning: (info.tokens ?? EmptyTokens).reasoning,
@@ -231,6 +233,7 @@ export const Info = Schema.Struct({
   parentID: optional(SessionID),
   summary: optional(Summary),
   cost: optional(Schema.Finite),
+  budget: optional(Schema.Finite),
   tokens: optional(Tokens),
   share: optional(Share),
   title: Schema.String,
@@ -265,6 +268,7 @@ export const CreateInput = Schema.optional(
     model: Schema.optional(Model),
     metadata: Schema.optional(Metadata),
     permission: Schema.optional(PermissionV1.Ruleset),
+    budget: Schema.optional(Schema.Finite),
     workspaceID: Schema.optional(WorkspaceV2.ID),
   }),
 )
@@ -422,6 +426,7 @@ export interface Interface {
     model?: Schema.Schema.Type<typeof Model>
     metadata?: typeof Metadata.Type
     permission?: PermissionV1.Ruleset
+    budget?: number
     workspaceID?: WorkspaceV2.ID
   }) => Effect.Effect<Info>
   readonly fork: (input: { sessionID: SessionID; messageID?: MessageID }) => Effect.Effect<Info, NotFound>
@@ -430,6 +435,7 @@ export interface Interface {
   readonly setTitle: (input: { sessionID: SessionID; title: string }) => Effect.Effect<void>
   readonly setArchived: (input: { sessionID: SessionID; time?: number }) => Effect.Effect<void>
   readonly setMetadata: (input: typeof SetMetadataInput.Type) => Effect.Effect<void>
+  readonly setBudget: (input: { sessionID: SessionID; budget?: number }) => Effect.Effect<void>
   readonly setAgentModel: (input: {
     sessionID: SessionID
     agent: string
@@ -509,6 +515,7 @@ const layer: Layer.Layer<
       path?: string
       metadata?: typeof Metadata.Type
       permission?: PermissionV1.Ruleset
+      budget?: number
     }) {
       const ctx = yield* InstanceState.context
       const result: Info = {
@@ -526,6 +533,7 @@ const layer: Layer.Layer<
         metadata: input.metadata,
         permission: input.permission ? [...input.permission] : undefined,
         cost: 0,
+        budget: input.budget,
         tokens: EmptyTokens,
         time: {
           created: Date.now(),
@@ -673,6 +681,7 @@ const layer: Layer.Layer<
       model?: Schema.Schema.Type<typeof Model>
       metadata?: typeof Metadata.Type
       permission?: PermissionV1.Ruleset
+      budget?: number
       workspaceID?: WorkspaceV2.ID
     }) {
       const ctx = yield* InstanceState.context
@@ -686,6 +695,7 @@ const layer: Layer.Layer<
         model: input?.model,
         metadata: input?.metadata,
         permission: input?.permission,
+        budget: input?.budget,
         workspaceID: input?.workspaceID ?? workspace,
       })
     })
@@ -764,6 +774,10 @@ const layer: Layer.Layer<
       yield* patch(input.sessionID, { metadata: input.metadata, time: { updated: Date.now() } }).pipe(Effect.orDie)
     })
 
+    const setBudget = Effect.fn("Session.setBudget")(function* (input: { sessionID: SessionID; budget?: number }) {
+      yield* patch(input.sessionID, { budget: input.budget, time: { updated: Date.now() } }).pipe(Effect.orDie)
+    })
+
     const setAgentModel = Effect.fn("Session.setAgentModel")(function* (input: {
       sessionID: SessionID
       agent: string
@@ -915,6 +929,7 @@ const layer: Layer.Layer<
       setTitle,
       setArchived,
       setMetadata,
+      setBudget,
       setAgentModel,
       setPermission,
       setRevert,

packages/opencode/test/session/processor-effect.test.ts

@@ -285,8 +285,53 @@ it.live("session.processor effect tests capture llm input cleanly", () =>
   ),
 )
 
-it.live("session.processor effect tests preserve text start time", () =>
+it.live("session.processor effect tests stop when the session budget is exceeded", () =>
   provideTmpdirServer(
+    ({ dir, llm }) =>
+      Effect.gen(function* () {
+        const { processors, session, provider } = yield* boot()
+
+        yield* llm.text("hello")
+
+        const chat = yield* session.create({ budget: 0 })
+        const parent = yield* user(chat.id, "hi")
+        const msg = yield* assistant(chat.id, parent.id, path.resolve(dir))
+        const mdl = yield* provider.getModel(ref.providerID, ref.modelID)
+        const handle = yield* processors.create({
+          assistantMessage: msg,
+          sessionID: chat.id,
+          model: mdl,
+        })
+
+        const value = yield* handle.process({
+          user: {
+            id: parent.id,
+            sessionID: chat.id,
+            role: "user",
+            time: parent.time,
+            agent: parent.agent,
+            model: { providerID: ref.providerID, modelID: ref.modelID },
+          } satisfies SessionV1.User,
+          sessionID: chat.id,
+          model: mdl,
+          agent: agent(),
+          system: [],
+          messages: [{ role: "user", content: "hi" }],
+          tools: {},
+        } satisfies LLM.StreamInput)
+        const parts = yield* MessageV2.parts(msg.id)
+
+        expect(value).toBe("stop")
+        expect(
+          parts.some((part) => part.type === "text" && part.text === "Session budget reached. Increase the budget to continue."),
+        ).toBe(true)
+        expect(msg.finish).toBe("stop")
+      }),
+    { config: (url) => providerCfg(url) },
+  ),
+)
+
+it.live("session.processor effect tests preserve text start time", () =>  provideTmpdirServer(
     ({ dir, llm }) =>
       Effect.gen(function* () {
         const database = yield* Database.Service

packages/opencode/test/session/prompt.test.ts

@@ -460,6 +460,27 @@ noLLMServer.instance(
   { config: cfg },
 )
 
+it.instance("loop stops without an LLM request when the session budget is exhausted", () =>
+  Effect.gen(function* () {
+    const { llm } = yield* useServerConfig(providerCfg)
+    const prompt = yield* SessionPrompt.Service
+    const sessions = yield* Session.Service
+    const chat = yield* sessions.create({ title: "Pinned", budget: 0 })
+    const seeded = yield* seed(chat.id, { finish: "stop" })
+    yield* prompt.prompt({
+      sessionID: chat.id,
+      agent: "build",
+      noReply: true,
+      parts: [{ type: "text", text: "continue please" }],
+    })
+
+    const result = yield* prompt.loop({ sessionID: chat.id })
+
+    expect(result.info.id).toBe(seeded.assistant.id)
+    expect(yield* llm.hits).toHaveLength(0)
+  }),
+)
+
 noLLMServer.instance(
   "loop exits for a completed parent turn with nonmonotonic message IDs",
   () =>

packages/opencode/test/session/schema-decoding.test.ts

@@ -65,6 +65,7 @@ describe("Session.Info", () => {
       title: "Full session",
       version: "1.0.0",
       metadata: { source: "test" },
+      budget: 2.5,
       time: { created: 100, updated: 200, compacting: 150, archived: 300 },
       permission: [{ action: "allow" as const, pattern: "*", permission: "read" }],
       revert: {

packages/schema/src/session.ts

@@ -23,6 +23,7 @@ export const Info = Schema.Struct({
   agent: Agent.ID.pipe(optional),
   model: Model.Ref.pipe(optional),
   cost: Schema.Finite,
+  budget: Schema.Finite.pipe(optional),
   tokens: Schema.Struct({
     input: Schema.Finite,
     output: Schema.Finite,

packages/schema/src/v1/session.ts

@@ -550,6 +550,7 @@ export const SessionInfo = Schema.Struct({
   parentID: optional(SessionID),
   summary: optional(SessionSummary),
   cost: optional(Schema.Finite),
+  budget: optional(Schema.Finite),
   tokens: optional(SessionTokens),
   share: optional(SessionShare),
   title: Schema.String,