diff --git a/packages/app/src/runtime/persistence/codec-types.test.ts b/packages/app/src/runtime/persistence/codec-types.test.ts
new file mode 100644
index 00000000000..19e24bd636d
--- /dev/null
+++ b/packages/app/src/runtime/persistence/codec-types.test.ts
@@ -0,0 +1,17 @@
+import { expect, test } from "bun:test"
+import { Codec } from "./codec"
+
+// Type-level checks: these compile only if inference matches what `typeof schema.Type` gave callers.
+test("struct types infer optional and required fields", () => {
+  const s = Codec.struct({ id: Codec.string, tab: Codec.optional(Codec.string), n: Codec.lenientOptional(Codec.number) })
+  const value: typeof s.Type = { id: "x" }
+  const tab: string | undefined = value.tab
+  const n: number | undefined = value.n
+  const t = Codec.transform(s, { decode: (old) => old.tab ?? old.id, encode: (v) => ({ id: v }) })
+  const out: string | Codec.Invalid = t.decode({ id: "a" })
+  const onlyOptional = Codec.struct({ tab: Codec.optional(Codec.string) })
+  const empty: typeof onlyOptional.Type = {}
+  const maybe: string | undefined = empty.tab
+  const viaTransform = Codec.transform(onlyOptional, { decode: (old) => old.tab, encode: (tab) => ({ tab }) })
+  expect([tab, n, out, maybe, viaTransform.decode({})]).toEqual([undefined, undefined, "a", undefined, undefined])
+})
diff --git a/packages/app/src/runtime/persistence/codec.test.ts b/packages/app/src/runtime/persistence/codec.test.ts
new file mode 100644
index 00000000000..077dc9425bf
--- /dev/null
+++ b/packages/app/src/runtime/persistence/codec.test.ts
@@ -0,0 +1,85 @@
+import { describe, expect, test } from "bun:test"
+import { Codec } from "./codec"
+
+describe("Codec", () => {
+  test("primitives reject the wrong shape and finite numbers only", () => {
+    expect(Codec.string.decode("a")).toBe("a")
+    expect(Codec.string.decode(1)).toBe(Codec.INVALID)
+    expect(Codec.number.decode(1.5)).toBe(1.5)
+    expect(Codec.number.decode(Number.NaN)).toBe(Codec.INVALID)
+    expect(Codec.nonNegativeInt.decode(-1)).toBe(Codec.INVALID)
+    expect(Codec.literals(["a", "b"]).decode("c")).toBe(Codec.INVALID)
+    expect(Codec.literal("x").decode("x")).toBe("x")
+  })
+
+  test("struct keeps optional fields absent and rejects invalid required ones", () => {
+    const codec = Codec.struct({ id: Codec.string, title: Codec.optional(Codec.string), n: Codec.lenientOptional(Codec.number) })
+    expect(codec.decode({ id: "1" })).toEqual({ id: "1" })
+    expect(codec.decode({ id: "1", title: "t", n: "bad" })).toEqual({ id: "1", title: "t" })
+    expect(codec.decode({ id: "1", title: 3 })).toBe(Codec.INVALID)
+    expect(codec.decode({ title: "t" })).toBe(Codec.INVALID)
+    expect(codec.decode([])).toBe(Codec.INVALID)
+    expect(codec.encode({ id: "1" })).toEqual({ id: "1" })
+    const value: typeof codec.Type = { id: "1", title: undefined }
+    expect(value.id).toBe("1")
+  })
+
+  test("lenient collections recover what they can", () => {
+    const items = Codec.lenientArray(Codec.struct({ id: Codec.string }))
+    expect(items.decode([{ id: "a" }, { id: 1 }, "x", { id: "b" }])).toEqual([{ id: "a" }, { id: "b" }])
+    expect(items.decode("nope")).toEqual([])
+    expect(Codec.array(Codec.string).decode(["a", 1])).toBe(Codec.INVALID)
+    const map = Codec.lenientRecord(Codec.boolean)
+    expect(map.decode({ a: true, b: "x" })).toEqual({})
+    expect(map.decode({ a: true })).toEqual({ a: true })
+  })
+
+  test("union, transform and fallback compose", () => {
+    const session = Codec.struct({ type: Codec.literal("session"), id: Codec.string })
+    const draft = Codec.struct({ type: Codec.literal("draft"), directory: Codec.string })
+    const tab = Codec.union([session, draft])
+    expect(tab.decode({ type: "draft", directory: "/x" })).toEqual({ type: "draft", directory: "/x" })
+    expect(tab.decode({ type: "other" })).toBe(Codec.INVALID)
+    const upper = Codec.transform(Codec.string, { decode: (s) => s.toUpperCase(), encode: (s) => s.toLowerCase() })
+    expect(upper.decode("ab")).toBe("AB")
+    expect(upper.encode("AB")).toBe("ab")
+    const safe = Codec.fallback(Codec.number, () => 7)
+    expect(safe.decode("x")).toBe(7)
+    expect(safe.decode(undefined)).toBe(7)
+    expect(safe.decode(2)).toBe(2)
+  })
+
+  test("brand constructs and decodes as its base", () => {
+    const Key = Codec.brand<"ServerConnection.Key">()
+    const key = Key.make("http://a")
+    expect(Key.decode(key)).toBe(key)
+    expect(Key.decode(3)).toBe(Codec.INVALID)
+  })
+
+  test("withInitial recovers field by field and merges new defaults", () => {
+    const layout = Codec.struct({
+      sidebar: Codec.struct({ opened: Codec.boolean, width: Codec.number }),
+      theme: Codec.lenientOptional(Codec.literals(["light", "dark"])),
+    })
+    const initial: typeof layout.Type = { sidebar: { opened: true, width: 240 } }
+    const codec = Codec.fromJsonString(Codec.withInitial(layout, initial))
+    expect(codec.decode(JSON.stringify({ sidebar: { opened: false, width: "wide" }, theme: "dark" }))).toEqual({
+      sidebar: { opened: false, width: 240 },
+      theme: "dark",
+    })
+    expect(codec.decode(JSON.stringify({ sidebar: 5 }))).toEqual(initial)
+    expect(codec.decode("{not json")).toBe(Codec.INVALID)
+    expect(JSON.parse(codec.encode({ sidebar: { opened: true, width: 1 } }))).toEqual({ sidebar: { opened: true, width: 1 } })
+  })
+
+  test("migrate reads the old shape first", () => {
+    const current = Codec.struct({ tabs: Codec.array(Codec.string) })
+    const previous = Codec.struct({ tab: Codec.optional(Codec.string) })
+    const read = Codec.transform(previous, {
+      decode: (old) => ({ tabs: old.tab ? [old.tab] : [] }),
+      encode: (value) => ({ tab: value.tabs[0] }),
+    })
+    const codec = Codec.withInitial(Codec.migrate(current, read), { tabs: [] })
+    expect(codec.decode({ tab: "a" })).toEqual({ tabs: ["a"] })
+  })
+})
diff --git a/packages/app/src/runtime/persistence/codec.ts b/packages/app/src/runtime/persistence/codec.ts
new file mode 100644
index 00000000000..ce0a0df7353
--- /dev/null
+++ b/packages/app/src/runtime/persistence/codec.ts
@@ -0,0 +1,324 @@
+export * as Codec from "./codec"
+
+// Plain codecs for persisted state. They replace Effect Schema in the renderer's initial module
+// graph, where Effect's own module initialisation was the single largest startup cost that was not
+// rendering. Semantics mirror the Persistence helpers: decoding never throws, `INVALID` marks a
+// value that cannot be recovered, and the lenient combinators recover what they can.
+
+export const INVALID: unique symbol = Symbol.for("opencode/persistence/codec/invalid")
+export type Invalid = typeof INVALID
+
+const tag: unique symbol = Symbol.for("opencode/persistence/codec")
+
+export interface Of<T, E = unknown> {
+  readonly [tag]: true
+  /** Phantom: `typeof codec.Type` is the decoded type, as with Effect schemas. */
+  readonly Type: T
+  readonly Encoded: E
+  readonly optional?: boolean
+  decode(input: unknown): T | Invalid
+  encode(value: T): E
+}
+
+export type Any = Of<any, any>
+export type Type<C extends Any> = C["Type"]
+
+export function isCodec(value: unknown): value is Any {
+  return typeof value === "object" && value !== null && tag in value
+}
+
+export function make<T, E = unknown>(decode: (input: unknown) => T | Invalid, encode: (value: T) => E): Of<T, E> {
+  return { [tag]: true, decode, encode } as Of<T, E>
+}
+
+export function is<T>(codec: Of<T>, input: unknown): input is T {
+  return codec.decode(input) !== INVALID
+}
+
+export function decodeOption<T>(codec: Of<T>, input: unknown): T | undefined {
+  const value = codec.decode(input)
+  return value === INVALID ? undefined : value
+}
+
+export function decodeOrThrow<T>(codec: Of<T>, input: unknown): T {
+  const value = codec.decode(input)
+  if (value === INVALID) throw new Error("Value does not match its codec")
+  return value
+}
+
+const identity = <T>(value: T) => value
+
+export const string: Of<string, string> = make((v) => (typeof v === "string" ? v : INVALID), identity)
+export const boolean: Of<boolean, boolean> = make((v) => (typeof v === "boolean" ? v : INVALID), identity)
+export const unknown: Of<unknown, unknown> = make((v) => v, identity)
+/** Finite numbers only: NaN and infinities are not JSON and never valid state. */
+export const number: Of<number, number> = make((v) => (typeof v === "number" && Number.isFinite(v) ? v : INVALID), identity)
+export const int: Of<number, number> = make((v) => (typeof v === "number" && Number.isInteger(v) ? v : INVALID), identity)
+export const nonNegativeInt: Of<number, number> = make(
+  (v) => (typeof v === "number" && Number.isInteger(v) && v >= 0 ? v : INVALID),
+  identity,
+)
+
+export function literal<const L extends string | number | boolean | null>(value: L): Of<L, L> {
+  return make((v) => (v === value ? value : INVALID), identity)
+}
+
+export function literals<const L extends ReadonlyArray<string | number | boolean | null>>(values: L): Of<L[number], L[number]> {
+  const set = new Set<unknown>(values)
+  return make((v) => (set.has(v) ? (v as L[number]) : INVALID), identity)
+}
+
+/** A string carrying a nominal brand, with the constructor Effect's `Schema.brand` gave callers. */
+export function brand<B extends string>(): Of<string & { readonly [K in B]: B }, string> & {
+  make(value: string): string & { readonly [K in B]: B }
+} {
+  return Object.assign(make<string & { readonly [K in B]: B }, string>((v) => (typeof v === "string" ? (v as never) : INVALID), identity), {
+    make: (value: string) => value as never,
+  })
+}
+
+export function nullOr<T, E>(codec: Of<T, E>): Of<T | null, E | null> {
+  return make((v) => (v === null ? null : codec.decode(v)), (v) => (v === null ? null : codec.encode(v)))
+}
+
+export function undefinedOr<T, E>(codec: Of<T, E>): Of<T | undefined, E | undefined> {
+  return make((v) => (v === undefined ? undefined : codec.decode(v)), (v) => (v === undefined ? undefined : codec.encode(v)))
+}
+
+/** A struct field that may be absent. Present but invalid values make the struct invalid. */
+export function optional<T, E>(codec: Of<T, E>): Of<T | undefined, E | undefined> & { readonly optional: true } {
+  return { ...undefinedOr(codec), optional: true } as never
+}
+
+/** A struct field that may be absent, and whose invalid values are dropped rather than rejected. */
+export function lenientOptional<T, E>(codec: Of<T, E>): Of<T | undefined, E | undefined> & { readonly optional: true } {
+  return {
+    ...make<T | undefined, E | undefined>(
+      (v) => {
+        if (v === undefined) return undefined
+        const value = codec.decode(v)
+        return value === INVALID ? undefined : value
+      },
+      (v) => (v === undefined ? undefined : codec.encode(v)),
+    ),
+    optional: true,
+  } as never
+}
+
+type Fields = Record<string, Any>
+type OptionalKeys<F extends Fields> = { [K in keyof F]: F[K] extends { optional: true } ? K : never }[keyof F]
+type RequiredKeys<F extends Fields> = Exclude<keyof F, OptionalKeys<F>>
+type Simplify<T> = { [K in keyof T]: T[K] } & {}
+export type StructType<F extends Fields> = Simplify<
+  { [K in RequiredKeys<F>]: F[K]["Type"] } & { [K in OptionalKeys<F>]?: F[K]["Type"] }
+>
+export type StructEncoded<F extends Fields> = Simplify<
+  { [K in RequiredKeys<F>]: F[K]["Encoded"] } & { [K in OptionalKeys<F>]?: F[K]["Encoded"] }
+>
+
+export interface Struct<F extends Fields> extends Of<StructType<F>, StructEncoded<F>> {
+  readonly fields: F
+}
+
+export function struct<const F extends Fields>(fields: F): Struct<F> {
+  const entries = Object.entries(fields)
+  return {
+    ...make<StructType<F>, StructEncoded<F>>(
+      (input) => {
+        if (typeof input !== "object" || input === null || Array.isArray(input)) return INVALID
+        const record = input as Record<string, unknown>
+        const out: Record<string, unknown> = {}
+        for (const [key, codec] of entries) {
+          const present = Object.hasOwn(record, key)
+          if (!present && codec.optional) continue
+          const value = codec.decode(record[key])
+          if (value === INVALID) return INVALID
+          if (value !== undefined || present) out[key] = value
+        }
+        return out as StructType<F>
+      },
+      (value) => {
+        const out: Record<string, unknown> = {}
+        for (const [key, codec] of entries) {
+          const field = (value as Record<string, unknown>)[key]
+          if (field === undefined && !Object.hasOwn(value as object, key)) continue
+          out[key] = codec.encode(field)
+        }
+        return out as StructEncoded<F>
+      },
+    ),
+    fields,
+  }
+}
+
+export function array<T, E>(codec: Of<T, E>): Of<T[], E[]> {
+  return make(
+    (input) => {
+      if (!Array.isArray(input)) return INVALID
+      const out: T[] = []
+      for (const item of input) {
+        const value = codec.decode(item)
+        if (value === INVALID) return INVALID
+        out.push(value)
+      }
+      return out
+    },
+    (value) => value.map((item) => codec.encode(item)),
+  )
+}
+
+/** Keeps the items that decode and drops the rest, like `Persistence.array`. */
+export function lenientArray<T, E>(codec: Of<T, E>): Of<T[], E[]> {
+  return make(
+    (input) => {
+      if (!Array.isArray(input)) return []
+      return input.flatMap((item) => {
+        const value = codec.decode(item)
+        return value === INVALID ? [] : [value]
+      })
+    },
+    (value) => value.map((item) => codec.encode(item)),
+  )
+}
+
+export function record<T, E>(codec: Of<T, E>): Of<Record<string, T>, Record<string, E>> {
+  return make(
+    (input) => {
+      if (typeof input !== "object" || input === null || Array.isArray(input)) return INVALID
+      const out: Record<string, T> = {}
+      for (const [key, item] of Object.entries(input)) {
+        const value = codec.decode(item)
+        if (value === INVALID) return INVALID
+        out[key] = value
+      }
+      return out
+    },
+    (value) => Object.fromEntries(Object.entries(value).map(([key, item]) => [key, codec.encode(item)])),
+  )
+}
+
+/** An invalid record becomes empty rather than failing the whole store, like `Persistence.record`. */
+export function lenientRecord<T, E>(codec: Of<T, E>): Of<Record<string, T>, Record<string, E>> {
+  const strict = record(codec)
+  return make(
+    (input) => {
+      const value = strict.decode(input)
+      return value === INVALID ? {} : value
+    },
+    strict.encode,
+  )
+}
+
+export function union<const C extends ReadonlyArray<Any>>(codecs: C): Of<C[number]["Type"], C[number]["Encoded"]> {
+  return make(
+    (input) => {
+      for (const codec of codecs) {
+        const value = codec.decode(input)
+        if (value !== INVALID) return value
+      }
+      return INVALID
+    },
+    (value) => {
+      // Encode with the first member that accepts the value's shape; members are disjoint in practice.
+      for (const codec of codecs) if (codec.decode(value) !== INVALID) return codec.encode(value)
+      return value as C[number]["Encoded"]
+    },
+  )
+}
+
+/** Maps a decoded value into another shape, the replacement for `decodeTo` + `SchemaGetter.transform`. */
+export function transform<T, E, T2>(
+  codec: Of<T, E>,
+  options: { decode: (value: T) => T2; encode: (value: T2) => T },
+): Of<T2, E> {
+  return make(
+    (input) => {
+      const value = codec.decode(input)
+      return value === INVALID ? INVALID : options.decode(value)
+    },
+    (value) => codec.encode(options.encode(value)),
+  )
+}
+
+/** Invalid and missing values become `value()`, like `Persistence.fallback`. */
+export function fallback<T, E>(codec: Of<T, E>, value: () => T): Of<T, E> {
+  return make(
+    (input) => {
+      if (input === undefined) return value()
+      const decoded = codec.decode(input)
+      return decoded === INVALID ? value() : decoded
+    },
+    codec.encode,
+  )
+}
+
+export function fromJsonString<T, E>(codec: Of<T, E>): Of<T, string> {
+  return make(
+    (input) => {
+      if (typeof input !== "string") return INVALID
+      try {
+        return codec.decode(JSON.parse(input))
+      } catch {
+        return INVALID
+      }
+    },
+    (value) => JSON.stringify(codec.encode(value)),
+  )
+}
+
+export type Migrated<C extends Any> = { readonly current: C; readonly read: Of<unknown> }
+
+/** Older stored shapes go through `read` first; `current` describes what the store holds today. */
+export function migrate<C extends Any>(current: C, read: Of<unknown>): Migrated<C> {
+  return { current, read }
+}
+
+function isMigrated<C extends Any>(definition: C | Migrated<C>): definition is Migrated<C> {
+  return !isCodec(definition) && "current" in definition
+}
+
+// Stored values recover field by field against the initial value: an object's valid fields are
+// kept, invalid or missing ones take their initial counterpart, and the result is merged over the
+// initial so new fields appear with their defaults. Mirrors `Persistence.withInitial`.
+export function withInitial<C extends Any>(definition: C | Migrated<C>, initial: Type<C>): Of<Type<C>, unknown> {
+  const codec = isMigrated(definition) ? definition.current : definition
+  const read = isMigrated(definition) ? definition.read : unknown
+  return make(
+    (input) => {
+      const stored = read.decode(input)
+      if (stored === INVALID) return INVALID
+      return merge(initial, recover(codec, stored, initial))
+    },
+    (value) => codec.encode(value),
+  )
+}
+
+function recover(codec: Any, value: unknown, initial: unknown): unknown {
+  if (value === undefined) return initial
+  if ("fields" in codec && isObject(value)) {
+    const fields = (codec as Struct<Fields>).fields
+    return Object.fromEntries(
+      Object.entries(fields).flatMap(([name, field]) => {
+        const defaults = isObject(initial) ? initial[name] : undefined
+        const next = recover(field, value[name], defaults)
+        if (next === undefined && !Object.hasOwn(value, name) && defaults === undefined) return []
+        return [[name, next]]
+      }),
+    )
+  }
+  const decoded = codec.decode(value)
+  return decoded === INVALID ? initial : decoded
+}
+
+function merge(initial: unknown, value: unknown): unknown {
+  if (value === undefined) return initial
+  if (!isObject(initial) || !isObject(value)) return value
+  return Object.fromEntries(
+    [...new Set([...Object.keys(initial), ...Object.keys(value)])].map((key) => [key, merge(initial[key], value[key])]),
+  )
+}
+
+function isObject(value: unknown): value is Record<string, unknown> {
+  return typeof value === "object" && value !== null && !Array.isArray(value)
+}
+
diff --git a/packages/app/src/runtime/persistence/storage.ts b/packages/app/src/runtime/persistence/storage.ts
index 6984466788e..3553f1a0299 100644
--- a/packages/app/src/runtime/persistence/storage.ts
+++ b/packages/app/src/runtime/persistence/storage.ts
@@ -6,6 +6,7 @@ import { createStore, type SetStoreFunction, type Store } from "solid-js/store"
 import { Option, Schema } from "effect"
 import { pathKey } from "@/workspaces/path-key"
 import { ScopedKey, ServerScope } from "@/runtime/server/scope"
+import { Codec } from "./codec"
 import { persistStore } from "./persist"
 import { Persistence } from "./schema"
 
@@ -472,25 +473,57 @@ export function removePersisted(
   }
 }
 
-export function persisted<S extends Schema.ConstraintCodec<object, unknown>>(
+type Definition<S extends Schema.ConstraintCodec<object, unknown> | Codec.Any> =
+  | S
+  | Persistence.Migrated<Extract<S, Schema.ConstraintCodec<object, unknown>>>
+  | Codec.Migrated<Extract<S, Codec.Any>>
+
+// Persisted stores are moving from Effect Schema to the plain codecs in ./codec so the renderer
+// stops paying for Effect at startup; both are accepted while the migration is underway.
+function serializer<S extends Schema.ConstraintCodec<object, unknown> | Codec.Any>(
+  definition: Definition<S>,
+  initial: S["Type"],
+) {
+  if (Codec.isCodec(definition) || (!("current" in definition) ? false : Codec.isCodec(definition.current))) {
+    const codec = Codec.withInitial(definition as Codec.Any | Codec.Migrated<Codec.Any>, initial)
+    const json = Codec.fromJsonString(codec)
+    return {
+      decode: (raw: string) => Codec.decodeOption(json, raw) as S["Type"] | undefined,
+      deserialize: (raw: unknown) => Codec.decodeOrThrow(json, raw) as S["Type"],
+      serialize: (value: S["Type"]) => json.encode(value),
+      encode: (value: S["Type"]) => codec.encode(value),
+      initial: Codec.decodeOrThrow(codec, codec.encode(initial)) as S["Type"],
+    }
+  }
+  const schema = definition as Schema.ConstraintCodec<object, unknown> | Persistence.Migrated<Schema.ConstraintCodec<object, unknown>>
+  const initialized = Persistence.withInitial(schema, initial as object)
+  const json = Schema.fromJsonString(initialized)
+  const decode = Schema.decodeUnknownOption(json)
+  return {
+    decode: (raw: string) => Option.getOrUndefined(decode(raw)) as S["Type"] | undefined,
+    deserialize: Schema.decodeUnknownSync(json) as (raw: unknown) => S["Type"],
+    serialize: Schema.encodeSync(json) as (value: S["Type"]) => string,
+    encode: Schema.encodeSync(initialized) as (value: S["Type"]) => unknown,
+    initial: Schema.decodeUnknownSync(Schema.toType(initialized))(initial as object) as S["Type"],
+  }
+}
+
+export function persisted<S extends Schema.ConstraintCodec<object, unknown> | Codec.Any>(
   target: string | PersistTarget,
-  schema: S | Persistence.Migrated<S>,
+  schema: Definition<S>,
   initial: NoInfer<S["Type"]>,
   platformOverride?: Platform,
 ): PersistedWithReady<S["Type"]> {
   const platform = platformOverride ?? usePlatform()
   const config = resolveTarget(typeof target === "string" ? { key: target } : target, platform)
 
-  const initialized = Persistence.withInitial(schema, initial)
-  const json = Schema.fromJsonString(initialized)
-  const decode = Schema.decodeUnknownOption(json)
-  const encode = Schema.encodeSync(initialized)
-  const serialize = Schema.encodeSync(json)
+  const codec = serializer<S>(schema, initial)
+  const { encode, serialize } = codec
   const normalize = (raw: string) => {
-    const value = decode(raw)
-    if (Option.isSome(value)) return serialize(value.value)
+    const value = codec.decode(raw)
+    if (value !== undefined) return serialize(value)
   }
-  const store = createStore<S["Type"]>(Schema.decodeUnknownSync(Schema.toType(initialized))(initial))
+  const store = createStore<S["Type"]>(codec.initial)
   const isDesktop = platform.platform === "desktop" && !!platform.storage
   const draft = config.draft ? platform.draftStore : undefined
   const prefix = `${config.storage ?? "default"}:`
@@ -602,7 +635,7 @@ export function persisted<S extends Schema.ConstraintCodec<object, unknown>>(
     name: config.key,
     storage,
     serialize,
-    deserialize: Schema.decodeUnknownSync(json),
+    deserialize: codec.deserialize,
     sync: channel ? messageSync(channel) : undefined,
     // Drafts take the encoded document itself so large text is externalized without the store
     // re-parsing the serialized form on every save.
diff --git a/packages/app/src/runtime/server/key.ts b/packages/app/src/runtime/server/key.ts
new file mode 100644
index 00000000000..4d4b7683bc9
--- /dev/null
+++ b/packages/app/src/runtime/server/key.ts
@@ -0,0 +1,11 @@
+import type { Brand } from "effect"
+import { Codec } from "@/runtime/persistence/codec"
+
+// The server key's brand is shared with the Effect schema in ./persistence.ts (type only, so this
+// module loads nothing of Effect), letting stores port to plain codecs one at a time.
+export type ServerKey = string & Brand.Brand<"ServerConnection.Key">
+
+export const ServerKey: Codec.Of<ServerKey, string> & { make(value: string): ServerKey } = Object.assign(
+  Codec.make<ServerKey, string>((v) => (typeof v === "string" ? (v as ServerKey) : Codec.INVALID), (v) => v),
+  { make: (value: string) => value as ServerKey },
+)
diff --git a/packages/app/src/shell/state/layout.tsx b/packages/app/src/shell/state/layout.tsx
index 4cf523b55c7..93ee3bfbe6d 100644
--- a/packages/app/src/shell/state/layout.tsx
+++ b/packages/app/src/shell/state/layout.tsx
@@ -9,7 +9,7 @@ import { usePlatform } from "@/runtime/platform/platform"
 import type { Project } from "@/runtime/server/types"
 import { Persist, persisted, removePersisted } from "@/runtime/persistence/storage"
 import { Persistence } from "@/runtime/persistence/schema"
-import { TabStorage } from "@/shell/tabs/schema"
+import { ServerKey } from "@/runtime/server/persistence"
 import { decode64 } from "@/runtime/persistence/base64"
 import { same } from "@/runtime/persistence/equality"
 import { createScrollPersistence, type SessionScroll } from "./scroll"
@@ -165,7 +165,7 @@ export const layoutSchema = Persistence.struct({
   sessionView: Persistence.record(Persistence.fallback(sessionViewSchema, () => ({ scroll: {} }))),
   home: Persistence.struct({
     selection: Persistence.struct({
-      server: Schema.optional(TabStorage.ServerKey),
+      server: Schema.optional(ServerKey),
       directory: Schema.optional(Schema.String),
     }),
   }),
diff --git a/packages/app/src/shell/tabs/schema.ts b/packages/app/src/shell/tabs/schema.ts
index c8f3e8b582d..4570dbb4565 100644
--- a/packages/app/src/shell/tabs/schema.ts
+++ b/packages/app/src/shell/tabs/schema.ts
@@ -1,63 +1,58 @@
 export * as TabStorage from "./schema"
 
-import { Schema, SchemaGetter } from "effect"
-import { ServerKey } from "@/runtime/server/persistence"
-import { Persistence } from "@/runtime/persistence/schema"
+import { Codec } from "@/runtime/persistence/codec"
+import { ServerKey } from "@/runtime/server/key"
 
 export { ServerKey }
 
-export const Session = Persistence.struct({
-  type: Schema.Literal("session"),
+export const Session = Codec.struct({
+  type: Codec.literal("session"),
   server: ServerKey,
-  sessionId: Schema.String,
-  routeSessionId: Persistence.optional(Schema.String),
-  routeParentId: Persistence.optional(Schema.String),
+  sessionId: Codec.string,
+  routeSessionId: Codec.lenientOptional(Codec.string),
+  routeParentId: Codec.lenientOptional(Codec.string),
 })
 
-export const Draft = Persistence.struct({
-  type: Schema.Literal("draft"),
-  draftID: Schema.String,
+export const Draft = Codec.struct({
+  type: Codec.literal("draft"),
+  draftID: Codec.string,
   server: ServerKey,
-  directory: Schema.String,
-  worktree: Persistence.optional(Schema.String),
-  branch: Persistence.optional(Schema.String),
-  mcp: Persistence.optional(Persistence.struct({ target: Schema.String, states: Persistence.record(Schema.Boolean) })),
+  directory: Codec.string,
+  worktree: Codec.lenientOptional(Codec.string),
+  branch: Codec.lenientOptional(Codec.string),
+  mcp: Codec.lenientOptional(Codec.struct({ target: Codec.string, states: Codec.lenientRecord(Codec.boolean) })),
 })
 
-const SessionCodec = Session.pipe(
-  Schema.decodeTo(Schema.toType(Session), {
-    decode: SchemaGetter.transform((tab) => ({
-      type: tab.type,
-      server: tab.server,
-      sessionId: tab.sessionId,
-      ...(tab.routeSessionId && tab.routeSessionId !== tab.sessionId
-        ? { routeSessionId: tab.routeSessionId, ...(tab.routeParentId ? { routeParentId: tab.routeParentId } : {}) }
-        : {}),
-    })),
-    encode: SchemaGetter.transform((tab) => tab),
+// A stored route that only repeats the session id carries nothing; drop it and its parent.
+const SessionCodec = Codec.transform(Session, {
+  decode: (tab) => ({
+    type: tab.type,
+    server: tab.server,
+    sessionId: tab.sessionId,
+    ...(tab.routeSessionId && tab.routeSessionId !== tab.sessionId
+      ? { routeSessionId: tab.routeSessionId, ...(tab.routeParentId ? { routeParentId: tab.routeParentId } : {}) }
+      : {}),
+  }),
+  encode: (tab) => tab,
+})
+
+export const Tab = Codec.union([Session, Draft])
+export const Tabs = Codec.lenientArray(Codec.union([SessionCodec, Draft]))
+export const Recent = Codec.struct({
+  key: Codec.optional(Codec.string),
+})
+export const Info = Codec.struct({
+  title: Codec.optional(Codec.string),
+  directory: Codec.optional(Codec.string),
+})
+export const Infos = Codec.record(Info)
+export const Panes = Codec.record(
+  Codec.struct({
+    terminal: Codec.optional(Codec.boolean),
+    review: Codec.optional(Codec.boolean),
+    terminalHeight: Codec.optional(Codec.number),
+    sessionWidth: Codec.optional(Codec.number),
   }),
 )
-
-export const Tab = Schema.Union([Session, Draft])
-export const Tabs = Persistence.array(Schema.Union([SessionCodec, Draft]))
-export const Recent = Persistence.struct({
-  key: Schema.optional(Schema.String),
-})
-export const Info = Persistence.struct({
-  title: Schema.optional(Schema.String),
-  directory: Schema.optional(Schema.String),
-})
-export const Infos = Schema.Record(Schema.String, Schema.mutableKey(Info))
-export const Panes = Schema.Record(
-  Schema.String,
-  Schema.mutableKey(
-    Persistence.struct({
-      terminal: Schema.optional(Schema.Boolean),
-      review: Schema.optional(Schema.Boolean),
-      terminalHeight: Schema.optional(Schema.Finite),
-      sessionWidth: Schema.optional(Schema.Finite),
-    }),
-  ),
-)
-export const ClosedTab = Schema.Struct({ tab: SessionCodec, index: Schema.Int.check(Schema.isGreaterThanOrEqualTo(0)) })
-export const Closed = Persistence.array(ClosedTab)
+export const ClosedTab = Codec.struct({ tab: SessionCodec, index: Codec.nonNegativeInt })
+export const Closed = Codec.lenientArray(ClosedTab)
diff --git a/packages/app/src/shell/tabs/tabs.test.ts b/packages/app/src/shell/tabs/tabs.test.ts
index 15cfd30c276..f482dc5f301 100644
--- a/packages/app/src/shell/tabs/tabs.test.ts
+++ b/packages/app/src/shell/tabs/tabs.test.ts
@@ -3,13 +3,12 @@ import { createRoot, getOwner, onCleanup } from "solid-js"
 import { createTabMemory } from "./memory"
 import { nextTabAfterClose, pushClosedTab, removeClosedTabs, takeClosedTab, type ClosedTab } from "./closed"
 import { findSessionTab, sessionIDHasOpenTab, tabHref, tabKey, type SessionTab, type Tab } from "./tabs"
-import { Schema } from "effect"
 import { TabStorage } from "./schema"
 import type { ServerConnection } from "@/runtime/server/registry"
-import { Persistence } from "@/runtime/persistence/schema"
+import { Codec } from "@/runtime/persistence/codec"
 
 const server = "local\nhttp://localhost:4096" as ServerConnection.Key
-const decodeTabs = Schema.decodeUnknownSync(Persistence.withInitial(TabStorage.Tabs, []))
+const decodeTabs = ((input: unknown) => Codec.decodeOrThrow(Codec.withInitial(TabStorage.Tabs, []), input))
 
 function sessionTab(sessionId: string): SessionTab {
   return { type: "session", server, sessionId }
@@ -26,7 +25,7 @@ describe("tab migration", () => {
     }
     const restored = decodeTabs([legacy, draft])
     expect(restored).toEqual([legacy, draft])
-    expect(decodeTabs(Schema.encodeSync(TabStorage.Tabs)(restored))).toEqual([legacy, draft])
+    expect(decodeTabs(TabStorage.Tabs.encode(restored))).toEqual([legacy, draft])
   })
 
   test("drops null and malformed persisted tabs", () => {
@@ -64,13 +63,13 @@ describe("tab migration", () => {
       draft,
     ])
     expect(tabs).toEqual([sessionTab("root"), draft])
-    expect(Schema.encodeSync(TabStorage.Tabs)(tabs)).toEqual(tabs)
-    expect(decodeTabs(Schema.encodeSync(TabStorage.Tabs)(tabs))).toEqual(tabs)
+    expect(TabStorage.Tabs.encode(tabs)).toEqual(tabs)
+    expect(decodeTabs(TabStorage.Tabs.encode(tabs))).toEqual(tabs)
   })
 
   test("salvages valid closed session tabs", () => {
     expect(
-      Schema.decodeUnknownSync(Persistence.withInitial(TabStorage.Closed, []))([
+      ((input: unknown) => Codec.decodeOrThrow(Codec.withInitial(TabStorage.Closed, []), input))([
         { tab: sessionTab("a"), index: 1 },
         { tab: sessionTab("b"), index: -1 },
         { tab: { type: "draft", server, draftID: "d", directory: "/project" }, index: 0 },
@@ -81,16 +80,16 @@ describe("tab migration", () => {
 
   test("validates auxiliary tab state", () => {
     expect(
-      Schema.decodeUnknownSync(Persistence.withInitial(TabStorage.Recent, { key: undefined }))({ key: 1 }),
+      ((input: unknown) => Codec.decodeOrThrow(Codec.withInitial(TabStorage.Recent, { key: undefined }), input))({ key: 1 }),
     ).toEqual({ key: undefined })
-    expect(Schema.decodeUnknownSync(TabStorage.Infos)({})).toEqual({})
-    expect(Schema.decodeUnknownSync(TabStorage.Panes)({})).toEqual({})
-    expect(Schema.decodeUnknownSync(TabStorage.Infos)({ tab: { title: "Title", directory: "/project" } })).toEqual({
+    expect(Codec.decodeOrThrow(TabStorage.Infos, {})).toEqual({})
+    expect(Codec.decodeOrThrow(TabStorage.Panes, {})).toEqual({})
+    expect(Codec.decodeOrThrow(TabStorage.Infos, { tab: { title: "Title", directory: "/project" } })).toEqual({
       tab: { title: "Title", directory: "/project" },
     })
-    const panes = Schema.decodeUnknownSync(TabStorage.Panes)({ tab: { terminal: true, terminalHeight: 300 } })
-    expect(Schema.encodeSync(TabStorage.Panes)(panes)).toEqual({ tab: { terminal: true, terminalHeight: 300 } })
-    expect(() => Schema.decodeUnknownSync(TabStorage.Panes)({ tab: { terminal: "yes" } })).toThrow()
+    const panes = Codec.decodeOrThrow(TabStorage.Panes, { tab: { terminal: true, terminalHeight: 300 } })
+    expect(TabStorage.Panes.encode(panes)).toEqual({ tab: { terminal: true, terminalHeight: 300 } })
+    expect(() => Codec.decodeOrThrow(TabStorage.Panes, { tab: { terminal: "yes" } })).toThrow()
   })
 })
 
@@ -209,3 +208,5 @@ describe("closed tab stack", () => {
     expect(nextTabAfterClose([sessionTab("a")], 0, true)).toBeNull()
   })
 })
+
+