diff --git a/packages/opencode/BUN_SHELL_MIGRATION_PLAN.md b/packages/opencode/BUN_SHELL_MIGRATION_PLAN.md
deleted file mode 100644
index 569045c0640..00000000000
--- a/packages/opencode/BUN_SHELL_MIGRATION_PLAN.md
+++ /dev/null
@@ -1,136 +0,0 @@
-# Bun shell migration plan
-
-Practical phased replacement of Bun `$` calls.
-
-## Goal
-
-Replace runtime Bun shell template-tag usage in `packages/opencode/src` with a unified `Process` API in `util/process.ts`.
-
-Keep behavior stable while improving safety, testability, and observability.
-
-Current baseline from audit:
-
-- 143 runtime command invocations across 17 files
-- 84 are git commands
-- Largest hotspots:
-  - `src/cli/cmd/github.ts` (33)
-  - `src/worktree/index.ts` (22)
-  - `src/lsp/server.ts` (21)
-  - `src/installation/index.ts` (20)
-  - `src/snapshot/index.ts` (18)
-
-## Decisions
-
-- Extend `src/util/process.ts` (do not create a separate exec module).
-- Proceed with phased migration for both git and non-git paths.
-- Keep plugin `$` compatibility in 1.x and remove in 2.0.
-
-## Non-goals
-
-- Do not remove plugin `$` compatibility in this effort.
-- Do not redesign command semantics beyond what is needed to preserve behavior.
-
-## Constraints
-
-- Keep migration phased, not big-bang.
-- Minimize behavioral drift.
-- Keep these explicit shell-only exceptions:
-  - `src/session/prompt.ts` raw command execution
-  - worktree start scripts in `src/worktree/index.ts`
-
-## Process API proposal (`src/util/process.ts`)
-
-Add higher-level wrappers on top of current spawn support.
-
-Core methods:
-
-- `Process.run(cmd, opts)`
-- `Process.text(cmd, opts)`
-- `Process.lines(cmd, opts)`
-- `Process.status(cmd, opts)`
-- `Process.shell(command, opts)` for intentional shell execution
-
-Git helpers:
-
-- `Process.git(args, opts)`
-- `Process.gitText(args, opts)`
-
-Shared options:
-
-- `cwd`, `env`, `stdin`, `stdout`, `stderr`, `abort`, `timeout`, `kill`
-- `allowFailure` / non-throw mode
-- optional redaction + trace metadata
-
-Standard result shape:
-
-- `code`, `stdout`, `stderr`, `duration_ms`, `cmd`
-- helpers like `text()` and `arrayBuffer()` where useful
-
-## Phased rollout
-
-### Phase 0: Foundation
-
-- Implement Process wrappers in `src/util/process.ts`.
-- Refactor `src/util/git.ts` to use Process only.
-- Add tests for exit handling, timeout, abort, and output capture.
-
-### Phase 1: High-impact hotspots
-
-Migrate these first:
-
-- `src/cli/cmd/github.ts`
-- `src/worktree/index.ts`
-- `src/lsp/server.ts`
-- `src/installation/index.ts`
-- `src/snapshot/index.ts`
-
-Within each file, migrate git paths first where applicable.
-
-### Phase 2: Remaining git-heavy files
-
-Migrate git-centric call sites to `Process.git*` helpers:
-
-- `../core/src/filesystem.ts`
-- `src/project/vcs.ts`
-- `../core/src/filesystem/watcher.ts`
-- `src/storage/storage.ts`
-- `src/cli/cmd/pr.ts`
-
-### Phase 3: Remaining non-git files
-
-Migrate residual non-git usages:
-
-- `src/cli/cmd/tui/util/clipboard.ts`
-- `src/util/archive.ts`
-- `../core/src/filesystem/ripgrep.ts`
-- `src/tool/bash.ts`
-- `src/cli/cmd/uninstall.ts`
-
-### Phase 4: Stabilize
-
-- Remove dead wrappers and one-off patterns.
-- Keep plugin `$` compatibility isolated and documented as temporary.
-- Create linked 2.0 task for plugin `$` removal.
-
-## Validation strategy
-
-- Unit tests for new `Process` methods and options.
-- Integration tests on hotspot modules.
-- Smoke tests for install, snapshot, worktree, and GitHub flows.
-- Regression checks for output parsing behavior.
-
-## Risk mitigation
-
-- File-by-file PRs with small diffs.
-- Preserve behavior first, simplify second.
-- Keep shell-only exceptions explicit and documented.
-- Add consistent error shaping and logging at Process layer.
-
-## Definition of done
-
-- Runtime Bun `$` usage in `packages/opencode/src` is removed except:
-  - approved shell-only exceptions
-  - temporary plugin compatibility path (1.x)
-- Git paths use `Process.git*` consistently.
-- CI and targeted smoke tests pass.
-- 2.0 issue exists for plugin `$` removal.
diff --git a/packages/opencode/src/server/routes/instance/httpapi/middleware/error.ts b/packages/opencode/src/server/routes/instance/httpapi/middleware/error.ts
index 3ede517150e..21b53aba756 100644
--- a/packages/opencode/src/server/routes/instance/httpapi/middleware/error.ts
+++ b/packages/opencode/src/server/routes/instance/httpapi/middleware/error.ts
@@ -1,4 +1,5 @@
 import { NamedError } from "@opencode-ai/core/util/error"
+import { ConfigErrorV1 } from "@opencode-ai/core/v1/config/error"
 import { Cause, Effect } from "effect"
 import { HttpRouter, HttpServerError, HttpServerRespondable, HttpServerResponse } from "effect/unstable/http"
 
@@ -15,6 +16,15 @@ export const errorLayer = HttpRouter.middleware<{ handles: unknown }>()((effect)
       if (!defect) return Effect.failCause(cause)
 
       const error = defect.defect
+      if (
+        ConfigErrorV1.JsonError.isInstance(error) ||
+        ConfigErrorV1.InvalidError.isInstance(error) ||
+        ConfigErrorV1.FrontmatterError.isInstance(error) ||
+        ConfigErrorV1.DirectoryTypoError.isInstance(error)
+      ) {
+        return Effect.succeed(HttpServerResponse.jsonUnsafe(error.toObject(), { status: 400 }))
+      }
+
       const ref = `err_${crypto.randomUUID().slice(0, 8)}`
 
       return Effect.logError("failed", { ref, error, cause: Cause.pretty(cause) }).pipe(
diff --git a/packages/opencode/src/server/routes/instance/httpapi/server.ts b/packages/opencode/src/server/routes/instance/httpapi/server.ts
index aa274142c15..96780426657 100644
--- a/packages/opencode/src/server/routes/instance/httpapi/server.ts
+++ b/packages/opencode/src/server/routes/instance/httpapi/server.ts
@@ -264,7 +264,7 @@ export function createRoutes(
     ]),
     Layer.provide(Layer.succeed(CorsConfig)(corsOptions)),
     Layer.provide(InstanceLayer.layer),
-    Layer.provide(Observability.layer),
+    Layer.provideMerge(Observability.layer),
   )
 }
 
diff --git a/packages/opencode/test/server/httpapi-error-middleware.test.ts b/packages/opencode/test/server/httpapi-error-middleware.test.ts
index a78e0aafe56..7bfc6da032f 100644
--- a/packages/opencode/test/server/httpapi-error-middleware.test.ts
+++ b/packages/opencode/test/server/httpapi-error-middleware.test.ts
@@ -53,7 +53,7 @@ describe("HttpApi error middleware", () => {
     }),
   )
 
-  it.live("does not expose config defects from generic middleware", () =>
+  it.live("returns invalid config defects as structured client errors", () =>
     Effect.gen(function* () {
       const configError = new ConfigErrorV1.InvalidError({
         path: "/tmp/opencode.json",
@@ -70,11 +70,16 @@ describe("HttpApi error middleware", () => {
       const body = yield* response.json
       const serialized = JSON.stringify(body)
 
-      expect(response.status).toBe(500)
-      expectUnknownErrorBody(body)
-      expect(serialized).not.toContain("/tmp/opencode.json")
-      expect(serialized).not.toContain("provider")
-      expect(serialized).not.toContain("anthropic")
+      expect(response.status).toBe(400)
+      expect(body).toMatchObject({
+        name: "ConfigInvalidError",
+        data: {
+          path: "/tmp/opencode.json",
+          issues: [{ message: "Expected object", path: ["provider", "anthropic", "options"] }],
+        },
+      })
+      expect(serialized).toContain("/tmp/opencode.json")
+      expect(serialized).toContain("anthropic")
     }),
   )
 
diff --git a/packages/tui/src/util/renderer.ts b/packages/tui/src/util/renderer.ts
index 7bcd28ab655..66c1318f383 100644
--- a/packages/tui/src/util/renderer.ts
+++ b/packages/tui/src/util/renderer.ts
@@ -1,6 +1,8 @@
 import type { CliRenderer } from "@opentui/core"
 
 export function destroyRenderer(renderer: Pick<CliRenderer, "isDestroyed" | "setTerminalTitle" | "destroy">) {
-  renderer.setTerminalTitle("")
-  if (!renderer.isDestroyed) renderer.destroy()
+  if (!renderer.isDestroyed) {
+    renderer.setTerminalTitle("")
+    renderer.destroy()
+  }
 }