Return Option from the per-call project and session-id lookups

projectForCwd and the rebuildNarrowSet session-id branch returned
Effect.succeed(undefined) as a real value, which @effect/tsgo's
effectSucceedWithVoid flags and whose Effect.void rewrite does not
typecheck. They now return Option and unwrap only where they meet the
session context and the subscription seeding.

Author: GraemeF

packages/mcp/server.ts

@@ -524,10 +524,12 @@ export const makeProgram = (
       // Per-call project resolver. Operator override (COMMY_PROJECT)
       // is authoritative; otherwise derive from the calling session's cwd
       // at call time — process cwd is irrelevant.
-      const projectForCwd = (cwd: string | undefined): Effect.Effect<ProjectSlug | undefined> => {
-        if (parsed.project !== undefined) return Effect.succeed(parsed.project)
-        if (cwd === undefined) return Effect.succeed(undefined)
-        return Effect.map(deriveProject({ cwd, readGitContext }), Option.getOrUndefined)
+      const projectForCwd = (
+        cwd: string | undefined,
+      ): Effect.Effect<Option.Option<ProjectSlug>> => {
+        if (parsed.project !== undefined) return Effect.succeedSome(parsed.project)
+        if (cwd === undefined) return Effect.succeedNone
+        return deriveProject({ cwd, readGitContext })
       }
 
       // Sample the realm-wide editing switch once, before the tool list is
@@ -593,20 +595,18 @@ export const makeProgram = (
             Effect.succeedNone
       const rebuildNarrowSet: Effect.Effect<void> = (
         parsed.botName === undefined
-          ? Deferred.await(sessionIdDeferred).pipe(
-              Effect.map((sessionId): SessionId | undefined => sessionId),
-            )
-          : Effect.succeed(undefined)
+          ? Deferred.await(sessionIdDeferred).pipe(Effect.asSome)
+          : Effect.succeedNone
       ).pipe(
-        Effect.flatMap((sessionId) =>
+        Effect.flatMap((sessionId: Option.Option<SessionId>) =>
           withSessionContext(
             restoreSubscriptions({
               persisted: persistedTopicIntents,
               isBound: () => identityCache.boundIdentityIds().size > 0,
               narrowSet,
               inbox: adapter.inbox,
             }),
-            { sessionId, project: parsed.project },
+            { sessionId: Option.getOrUndefined(sessionId), project: parsed.project },
           ),
         ),
         Effect.catchAll((err) =>

packages/mcp/tools-session.test.ts

@@ -26,7 +26,7 @@ interface SessionRig {
 
 const buildSessionRig = (
   options: {
-    readonly projectForCwd?: (cwd: string | undefined) => Effect.Effect<ProjectSlug | undefined>
+    readonly projectForCwd?: (cwd: string | undefined) => Effect.Effect<Option.Option<ProjectSlug>>
     readonly feedSessionId?: (sessionId: SessionId) => Effect.Effect<void>
   } = {},
 ): Effect.Effect<SessionRig, never, Scope.Scope> =>
@@ -430,11 +430,9 @@ test('post with session_id + cwd mints cc-<project>-<sid-prefix> derived from cw
       Effect.gen(function* () {
         const rig = yield* buildSessionRig({
           projectForCwd: (cwd) =>
-            Effect.succeed(
-              cwd === '/home/x/myproject'
-                ? Option.getOrUndefined(sanitiseProjectSlug('myproject'))
-                : undefined,
-            ),
+            cwd === '/home/x/myproject'
+              ? Effect.succeed(sanitiseProjectSlug('myproject'))
+              : Effect.succeedNone,
         })
         const result = yield* Effect.promise(() =>
           rig.client.callTool({
@@ -466,7 +464,8 @@ test('two sessions in different cwds mint two different project prefixes', () =>
           '/home/x/myproject-b': slug('myproject-b'),
         }
         const rig = yield* buildSessionRig({
-          projectForCwd: (cwd) => Effect.succeed(cwd === undefined ? undefined : cwdToSlug[cwd]),
+          projectForCwd: (cwd) =>
+            Effect.succeed(Option.fromNullable(cwd === undefined ? undefined : cwdToSlug[cwd])),
         })
         yield* Effect.promise(() =>
           rig.client.callTool({
@@ -503,9 +502,9 @@ test('post with cwd from a non-project directory falls back to bare cc-<8>', ()
   Effect.runPromise(
     Effect.scoped(
       Effect.gen(function* () {
-        // projectForCwd returns undefined when cwd is not in a known repo.
+        // projectForCwd returns none when cwd is not in a known repo.
         // The minted name must NOT inherit the plugin's own location.
-        const rig = yield* buildSessionRig({ projectForCwd: () => Effect.succeed(undefined) })
+        const rig = yield* buildSessionRig({ projectForCwd: () => Effect.succeedNone })
         yield* Effect.promise(() =>
           rig.client.callTool({
             name: 'post',

packages/mcp/tools.ts

@@ -194,10 +194,10 @@ export interface RegisterToolsDeps {
    * minted `cc-<project>-<8>` name reflects the *calling* session's
    * project rather than the plugin's own location. Wired at boot in
    * `server.ts` from `COMMY_PROJECT` (operator override) and
-   * the git probe; defaults to a constant `undefined` resolver when
+   * the git probe; defaults to a resolver that always answers none when
    * omitted (tests that don't care about per-session derivation).
    */
-  readonly projectForCwd?: (cwd: string | undefined) => Effect.Effect<ProjectSlug | undefined>
+  readonly projectForCwd?: (cwd: string | undefined) => Effect.Effect<Option.Option<ProjectSlug>>
   /**
    * Restore (or seed) this session's narrow set on its first `subscribe`/
    * `unsubscribe` — memoised once per session_id in `server.ts`, so it runs
@@ -506,7 +506,7 @@ const UploadFileArgs = Schema.Struct({ path: Schema.String })
 
 const buildToolDefs = (deps: RegisterToolsDeps, cache: InternalCache): ReadonlyArray<ToolDef> => {
   const { adapter, identityCache, narrowSet } = deps
-  const projectForCwd = deps.projectForCwd ?? (() => Effect.succeed(undefined))
+  const projectForCwd = deps.projectForCwd ?? (() => Effect.succeedNone)
   /**
    * The tools that accept a host-supplied `session_id` (see
    * {@link ToolDef.hostSuppliedArgs}). EIGHT tools carry it. That is the same
@@ -548,7 +548,7 @@ const buildToolDefs = (deps: RegisterToolsDeps, cache: InternalCache): ReadonlyA
   }
   const projectForArgs = (
     args: Readonly<Record<string, unknown>>,
-  ): Effect.Effect<ProjectSlug | undefined> => projectForCwd(readCwd(args))
+  ): Effect.Effect<Option.Option<ProjectSlug>> => projectForCwd(readCwd(args))
   // Every tool call that carries arguments supplies its calling session's
   // context, uniformly. This DECIDES NOTHING about identity: it feeds the
   // shared session-id deferred (comms-k7cv) and puts the naming inputs where
@@ -569,7 +569,12 @@ const buildToolDefs = (deps: RegisterToolsDeps, cache: InternalCache): ReadonlyA
         projectForArgs(args).pipe(
           Effect.flatMap((project) =>
             feedSession(sessionId).pipe(
-              Effect.zipRight(withSessionContext(effect, { sessionId, project })),
+              Effect.zipRight(
+                withSessionContext(effect, {
+                  sessionId,
+                  project: Option.getOrUndefined(project),
+                }),
+              ),
             ),
           ),
         ),
@@ -937,7 +942,10 @@ const buildToolDefs = (deps: RegisterToolsDeps, cache: InternalCache): ReadonlyA
             // the snapshot persisted below captures the full live set and the
             // store's presence stays a true resume signal.
             if (sessionId !== undefined && deps.ensureSessionSubscriptions !== undefined) {
-              yield* deps.ensureSessionSubscriptions(sessionId, yield* projectForArgs(args))
+              yield* deps.ensureSessionSubscriptions(
+                sessionId,
+                Option.getOrUndefined(yield* projectForArgs(args)),
+              )
             }
             // Two sinks (see bootstrap.subscribeFromEnv): the consumer-side
             // narrow tells the event pump to tee matching events through;
@@ -983,7 +991,10 @@ const buildToolDefs = (deps: RegisterToolsDeps, cache: InternalCache): ReadonlyA
             // Fed by `runFor` before this effect runs (see subscribe).
             const sessionId = readSessionId(args)
             if (sessionId !== undefined && deps.ensureSessionSubscriptions !== undefined) {
-              yield* deps.ensureSessionSubscriptions(sessionId, yield* projectForArgs(args))
+              yield* deps.ensureSessionSubscriptions(
+                sessionId,
+                Option.getOrUndefined(yield* projectForArgs(args)),
+              )
             }
             yield* Effect.sync(() => narrowSet.remove(intent)).pipe(
               Effect.andThen(adapter.inbox.unsubscribe(intentToTarget(intent))),