diff --git a/packages/opencode/src/server/routes/instance/httpapi/middleware/workspace-routing.ts b/packages/opencode/src/server/routes/instance/httpapi/middleware/workspace-routing.ts
index b6fb560201..062c272ed5 100644
--- a/packages/opencode/src/server/routes/instance/httpapi/middleware/workspace-routing.ts
+++ b/packages/opencode/src/server/routes/instance/httpapi/middleware/workspace-routing.ts
@@ -179,10 +179,12 @@ function routeHttpApiWorkspace<E>(
     const sessionID = getWorkspaceRouteSessionID(requestURL(request))
     const session = sessionID
       ? yield* Session.Service.use((svc) => svc.get(sessionID)).pipe(
-          // Sketch: also swallow the typed `SessionNotFound` so this routing
-          // probe stays best-effort (matches the previous defect-only catch).
-          Effect.catch(() => Effect.succeed(undefined)),
-          Effect.catchDefect(() => Effect.succeed(undefined)),
+          // Best-effort routing probe: swallow only the typed SessionNotFound;
+          // any other error must propagate.
+          Effect.catchIf(
+            (err): err is Session.SessionNotFound => err instanceof Session.SessionNotFound,
+            () => Effect.succeed(undefined),
+          ),
         )
       : undefined
     const plan = yield* planRequest(request, session?.workspaceID)
diff --git a/packages/opencode/src/server/routes/instance/trace.ts b/packages/opencode/src/server/routes/instance/trace.ts
index e76bdc32c8..afd0dcff24 100644
--- a/packages/opencode/src/server/routes/instance/trace.ts
+++ b/packages/opencode/src/server/routes/instance/trace.ts
@@ -42,11 +42,10 @@ export function requestAttributes(c: RequestLike): Record<string, string> {
   return attributes
 }
 
-// Bridge typed service errors to the legacy Hono `NamedError` ErrorMiddleware.
-// The HttpApi adapter consumes typed errors directly via schema annotations,
-// but Hono's ErrorMiddleware switches on `instanceof NamedError`. Until the
-// legacy adapter is retired, catch the new typed errors here and rethrow the
-// equivalent NamedError so the existing 404 wiring keeps working.
+// TODO(typed-errors): bridge typed service errors to the legacy Hono
+// `NamedError` ErrorMiddleware. HttpApi consumes typed errors directly via
+// schema annotations, but Hono's ErrorMiddleware switches on
+// `instanceof NamedError`. Delete this shim once the legacy adapter retires.
 const adaptTypedErrors = <A, E, R>(
   self: Effect.Effect<A, E, R>,
 ): Effect.Effect<A, Exclude<E, Session.SessionNotFound>, R> =>
diff --git a/packages/opencode/test/server/httpapi-parity.test.ts b/packages/opencode/test/server/httpapi-parity.test.ts
index 5f77a09970..4e9dd184ce 100644
--- a/packages/opencode/test/server/httpapi-parity.test.ts
+++ b/packages/opencode/test/server/httpapi-parity.test.ts
@@ -105,18 +105,12 @@ describe("404 mapping for missing session", () => {
 })
 
 // ──────────────────────────────────────────────────────────────────────────────
-// Reproducer 3: 404 response body shape should match Hono's NamedError
-// envelope `{ name, data: { message } }`. HttpApi returns the typed-error
-// shape `{ _tag }` instead. SDK consumers reading `error.data.message`
-// see undefined.
-//
-// FIXME: unskip when error JSON shape policy is decided + applied (separate PR).
+// Reproducer 3: 404 response body matches Hono's NamedError envelope
+// `{ name, data: { message } }`. `Session.get` now fails with a typed
+// `SessionNotFound` annotated `httpApiStatus: 404`. The endpoint declares the
+// schema; HttpApi auto-routes status + body — no `mapNotFound` wrapper.
 // ──────────────────────────────────────────────────────────────────────────────
 describe("Error JSON shape parity", () => {
-  // Sketch: validates the typed-error pattern end-to-end on `session.get`. The
-  // service now fails with a typed `SessionNotFound` error annotated
-  // `httpApiStatus: 404`. The endpoint declares the schema, and HttpApi auto-
-  // routes the status + body — no `mapNotFound` wrapper required.
   test("HttpApi 404 body matches NamedError shape (sketch: session.get)", async () => {
     await using tmp = await tmpdir({ config: { formatter: false, lsp: false } })