diff --git a/src/multi_chain.ts b/src/multi_chain.ts
index 2c3e81d..99eefb9 100644
--- a/src/multi_chain.ts
+++ b/src/multi_chain.ts
@@ -3,27 +3,6 @@ import { UnionFromTuple } from "./object_builders.ts"
 import { Tagged } from "./tagged.ts"
 import { UPObjectChain, ObjectChainsInputU } from "./object_chain.ts"
 
-// to type the multi-chain handler, need something like 
-// a conditional type which will look up return types from the program map object
-
-// takes a list of EventHandlerPrograms and builds a new program which handles any of the events
-// handled by the individual programs
-// {
-//   // get output types for any tag
-//   eventPrograms: {eventTag: program}
-//   program: (ev) => Effect...  
-// }
-//  the event type input to the program will be the union of all the handled event types,
-// while the Effect types will be chosen based on the type of the event - basically the type 
-// of the individual handler program for that event
-// 
-// maybe want a MultiEventHandlerProgram type capturing the above ... and
-// which would be composable
-//
-// the returned program will have type:
-// Effect<union-of-requirements-of-programs,
-//        union-of-errors-of-programs,
-//        union-of-output-types-of-programs>
 
 export type ProgramDeps<T extends UPObjectChain> = ReturnType<T['program']> extends Effect.Effect<infer R, infer _E, infer _V>
     ? R
@@ -68,11 +47,11 @@ export type DistributeObjectChainValueTypes<I extends Tagged, Chains extends rea
 //
 // the Effect result type will be narrowed to the union member corresponding
 // to the input type when the input is supplied
-export function multiChain<Chains extends readonly [...UPObjectChain[]]>
+export function multiChainProgram<Chains extends readonly [...UPObjectChain[]]>
 
-    (eventHandlerPrograms: readonly [...Chains]) {
+    (chains: readonly [...Chains]) {
 
-    const progsByEventTag = eventHandlerPrograms.reduce(
+    const progsByEventTag = chains.reduce(
         (m, p) => { m[p.tagStr] = p; return m },
         {} as { [index: string]: UPObjectChain })
 
@@ -91,4 +70,28 @@ export function multiChain<Chains extends readonly [...UPObjectChain[]]>
         } else
             throw "NoProgram for tag: " + i.tag
     }
-}
\ No newline at end of file
+}
+
+export type MultiChain<Chains extends readonly [...UPObjectChain[]]> = {
+    readonly chains: Chains
+    readonly program: <Input extends ObjectChainsInputU<Chains>>(i: Input) => Effect.Effect<ProgramsDepsU<Chains>,
+        ProgramsErrorsU<Chains>,
+        Extract<DistributeObjectChainValueTypes<Input, Chains>, Input>>
+}
+
+export function multiChain<Chains extends readonly [...UPObjectChain[]]>
+    (chains: Chains) {
+    
+    return {
+        chains: chains,
+        program: multiChainProgram(chains)
+    } as MultiChain<Chains>
+}
+
+export function addChains<Chains extends readonly [...UPObjectChain[]],
+    AdditionalChains extends readonly [...UPObjectChain[]]>
+    (mc: MultiChain<Chains>,
+        additionalChains: AdditionalChains) {
+
+    return multiChain([...mc.chains, ...additionalChains])
+}
diff --git a/src/multi_chain_test.ts b/src/multi_chain_test.ts
index d9d5396..aa8e3de 100644
--- a/src/multi_chain_test.ts
+++ b/src/multi_chain_test.ts
@@ -3,7 +3,7 @@ import { Effect, Context } from "effect"
 import { Org, OrgService, getOrgByNick, User, UserService, getUserByIds, PushNotificationService, sendPush } from "./test_services.ts"
 import { tag } from "./tagged.ts"
 import { objectChain } from "./object_chain.ts"
-import { multiChain } from "./multi_chain.ts"
+import { multiChainProgram, multiChain, addChains } from "./multi_chain.ts"
 
 //////////////////// some steps //////////////////////////////////
 
@@ -85,13 +85,13 @@ const echoContext = Context.empty().pipe(
 
 const programs = [getOrgProg, sendWelcomePushProg] as const
 
-const multiChainProgram = multiChain(programs)
+const prog = multiChainProgram(programs)
 
-Deno.test("makeHandlerProgram", () => {
+Deno.test("multiChainProgram", () => {
     const getOrgInput: GetOrgInput = { tag: "GetOrg", data: { org_nick: "foo" } }
 
     // note the inferred Effect value type selects the output of the getOrg chain
-    const getOrgEffect = multiChainProgram(getOrgInput)
+    const getOrgEffect = prog(getOrgInput)
     const getOrgRunnable = Effect.provide(getOrgEffect, echoContext)
     const getOrgResult = Effect.runSync(getOrgRunnable)
 
@@ -104,7 +104,7 @@ Deno.test("makeHandlerProgram", () => {
     const sendWelcomePushInput: SendWelcomePushInput = { tag: "SendWelcomePush", data: { org_nick: "foo", user_id: "100" } }
 
     // note the inferred Effect value type selects the output of the sendWelcomePush chain
-    const sendWelcomePushEffect = multiChainProgram(sendWelcomePushInput)
+    const sendWelcomePushEffect = prog(sendWelcomePushInput)
     const sendWelcomePushRunnable = Effect.provide(sendWelcomePushEffect, echoContext)
     const sendWelcomePushResult = Effect.runSync(sendWelcomePushRunnable)
 
@@ -115,4 +115,39 @@ Deno.test("makeHandlerProgram", () => {
         formatWelcomePush: "Welcome Bar of Foo",
         sendPush: "push sent OK: Welcome Bar of Foo"
     })
+})
+
+Deno.test("multiChain", () => {
+    const mc = multiChain(programs)
+
+    const getOrgInput: GetOrgInput = { tag: "GetOrg", data: { org_nick: "foo" } }
+
+    // note the inferred Effect value type selects the output of the getOrg chain
+    const getOrgEffect = mc.program(getOrgInput)
+    const getOrgRunnable = Effect.provide(getOrgEffect, echoContext)
+    const getOrgResult = Effect.runSync(getOrgRunnable)
+
+    assertEquals(getOrgResult, {
+        ...getOrgInput,
+        org: { id: "foo", name: "Foo" },
+        apiResponse: { org: { id: "foo", name: "Foo" } }
+    })
+})
+
+Deno.test("addChains", () => {
+    const emptyMultiChain = multiChain([])
+    const mc = addChains(emptyMultiChain, programs)
+
+    const getOrgInput: GetOrgInput = { tag: "GetOrg", data: { org_nick: "foo" } }
+
+    // note the inferred Effect value type selects the output of the getOrg chain
+    const getOrgEffect = mc.program(getOrgInput)
+    const getOrgRunnable = Effect.provide(getOrgEffect, echoContext)
+    const getOrgResult = Effect.runSync(getOrgRunnable)
+
+    assertEquals(getOrgResult, {
+        ...getOrgInput,
+        org: { id: "foo", name: "Foo" },
+        apiResponse: { org: { id: "foo", name: "Foo" } }
+    })
 })
\ No newline at end of file