diff --git a/packages/opencode/scripts/diff-sdk-types.sh b/packages/opencode/scripts/diff-sdk-types.sh
new file mode 100755
index 0000000000..85aa9d4e70
--- /dev/null
+++ b/packages/opencode/scripts/diff-sdk-types.sh
@@ -0,0 +1,51 @@
+#!/bin/bash
+# Compare SDK types generated from Hono vs HttpApi specs.
+# Sorts types alphabetically so only meaningful body differences show.
+#
+# Usage: ./scripts/diff-sdk-types.sh          # full diff
+#        ./scripts/diff-sdk-types.sh --stat   # summary only
+set -euo pipefail
+
+DIR="$(cd "$(dirname "$0")/.." && pwd)"
+SDK="$(cd "$DIR/../sdk/js" && pwd)"
+
+normalize() {
+  python3 -c "
+import re, sys
+content = open(sys.argv[1]).read()
+blocks = re.split(r'(?=^export (?:type|function|const) )', content, flags=re.MULTILINE)
+header, body = blocks[0], blocks[1:]
+body.sort(key=lambda b: m.group(1) if (m := re.match(r'export \w+ (\w+)', b)) else '')
+sys.stdout.write(header + ''.join(body))
+" "$1"
+}
+
+echo "Generating Hono SDK..." >&2
+(cd "$SDK" && bun run script/build.ts >/dev/null 2>&1)
+normalize "$SDK/src/v2/gen/types.gen.ts" > /tmp/sdk-types-hono.ts
+git -C "$SDK" checkout -- src/ 2>/dev/null
+
+echo "Generating HttpApi SDK..." >&2
+(cd "$SDK" && OPENCODE_SDK_OPENAPI=httpapi bun run script/build.ts >/dev/null 2>&1)
+normalize "$SDK/src/v2/gen/types.gen.ts" > /tmp/sdk-types-httpapi.ts
+git -C "$SDK" checkout -- src/ 2>/dev/null
+
+echo "" >&2
+if [[ "${1:-}" == "--stat" ]]; then
+  honly=$(diff /tmp/sdk-types-hono.ts /tmp/sdk-types-httpapi.ts | grep -c '^< export type' || true)
+  aonly=$(diff /tmp/sdk-types-hono.ts /tmp/sdk-types-httpapi.ts | grep -c '^> export type' || true)
+  total=$(diff /tmp/sdk-types-hono.ts /tmp/sdk-types-httpapi.ts | wc -l | tr -d ' ')
+  echo "Hono-only: $honly types  HttpApi-only: $aonly types  Diff lines: $total"
+  echo ""
+  if [[ $honly -gt 0 ]]; then
+    echo "=== Hono-only types ==="
+    diff /tmp/sdk-types-hono.ts /tmp/sdk-types-httpapi.ts | grep '^< export type' | sed 's/< export type /  /' | sed 's/ .*//'
+    echo ""
+  fi
+  if [[ $aonly -gt 0 ]]; then
+    echo "=== HttpApi-only types ==="
+    diff /tmp/sdk-types-hono.ts /tmp/sdk-types-httpapi.ts | grep '^> export type' | sed 's/> export type /  /' | sed 's/ .*//'
+  fi
+else
+  diff /tmp/sdk-types-hono.ts /tmp/sdk-types-httpapi.ts || true
+fi
diff --git a/packages/opencode/src/server/routes/instance/httpapi/public.ts b/packages/opencode/src/server/routes/instance/httpapi/public.ts
index a0e6a72236..be42a7ce89 100644
--- a/packages/opencode/src/server/routes/instance/httpapi/public.ts
+++ b/packages/opencode/src/server/routes/instance/httpapi/public.ts
@@ -58,10 +58,6 @@ const InstanceQueryParameters = [
   },
 ] satisfies OpenApiParameter[]
 
-// These refs already match the legacy SDK's expected body shape. Expanding all
-// other refs lets us strip Effect's `null` from optional fields in one place.
-const LegacyBodyRefParameters = new Set(["Auth", "Config", "Part", "WorktreeRemoveInput", "WorktreeResetInput"])
-
 // Query schemas describe decoded Effect values, but the generated SDK needs the
 // public call shape. These keep SDK callers passing numbers/booleans while the
 // server still decodes string query params at runtime.
@@ -82,6 +78,13 @@ function matchLegacyOpenApi(input: Record<string, unknown>) {
   // actual schema from any parent union that references them.
   fixSelfReferencingComponents(spec)
 
+  // Effect's Schema.optional emits `anyOf: [T, {type:"null"}]` in OpenAPI,
+  // but the legacy SDK expected plain `T` for optional fields. Strip null
+  // from all component schemas so both request and response types match.
+  for (const [name, schema] of Object.entries(spec.components?.schemas ?? {})) {
+    spec.components!.schemas![name] = stripOptionalNull(structuredClone(schema))
+  }
+
   for (const [path, item] of Object.entries(spec.paths ?? {})) {
     const isInstanceRoute = !path.startsWith("/global/") && !path.startsWith("/auth/")
     for (const method of ["get", "post", "put", "delete", "patch"] as const) {
@@ -91,23 +94,12 @@ function matchLegacyOpenApi(input: Record<string, unknown>) {
         // Hono's generated OpenAPI never marked request bodies as required. Keep
         // that SDK surface stable during the HttpApi migration.
         delete operation.requestBody.required
-        // Effect's Schema.optional emits `anyOf: [T, {type:"null"}]` in OpenAPI,
-        // but the legacy SDK expected plain `T` for optional fields. Expand
-        // non-legacy $refs and strip the null arms so the SDK surface is stable.
-        for (const media of Object.values(operation.requestBody.content ?? {})) {
-          const ref = media.schema?.$ref?.replace("#/components/schemas/", "")
-          if (ref && LegacyBodyRefParameters.has(ref)) continue
-          if (ref && spec.components?.schemas?.[ref]) {
-            media.schema = stripOptionalNull(structuredClone(spec.components.schemas[ref]))
-            continue
-          }
-          if (media.schema) media.schema = stripOptionalNull(media.schema)
-        }
         if (path === "/experimental/workspace" && method === "post") {
           // Workspace creation fields `branch` and `extra` are Schema.NullOr —
           // genuinely nullable, not just optional. Re-add the null that the
-          // global strip above removed.
-          const properties = operation.requestBody.content?.["application/json"]?.schema?.properties
+          // component-level strip above removed.
+          const ref = operation.requestBody.content?.["application/json"]?.schema?.$ref?.replace("#/components/schemas/", "")
+          const properties = ref ? spec.components?.schemas?.[ref]?.properties : operation.requestBody.content?.["application/json"]?.schema?.properties
           if (properties?.branch) properties.branch = { anyOf: [properties.branch, { type: "null" }] }
           if (properties?.extra) properties.extra = { anyOf: [properties.extra, { type: "null" }] }
         }