diff --git a/src/hooks/useDashboardCtx.test.ts b/src/hooks/useDashboardCtx.test.ts
index 0444309..b4c4053 100644
--- a/src/hooks/useDashboardCtx.test.ts
+++ b/src/hooks/useDashboardCtx.test.ts
@@ -119,6 +119,48 @@ describe('useDashboardCtx', () => {
     expect(result.current.envs).toEqual(envsBefore)
   })
 
+  // BUG-DASH-001 (P0): pre-fix a 67-char input persisted to
+  // localStorage and broke every subsequent API call. Now the input is
+  // clipped to the api cap (32 chars). The clipped string must still
+  // match the api regex `^[a-z0-9-]{1,32}$`.
+  it('addEnv clips an over-32-char input to the api cap', async () => {
+    const mod = await load()
+    const { result } = renderHook(() => mod.useDashboardCtx())
+    await waitFor(() => expect(result.current.me).not.toBeNull())
+    const longInput = 'a'.repeat(67) // 67 chars of valid char class
+    await act(async () => { mod.addEnv(longInput) })
+    // The persisted env name must be ≤ 32 chars (api cap).
+    expect(result.current.env.length).toBeLessThanOrEqual(32)
+    expect(result.current.env).toMatch(/^[a-z0-9-]{1,32}$/)
+  })
+
+  // BUG-DASH-002: pre-fix the JS regex permitted underscores even
+  // though the api regex bans them. Underscore inputs would persist
+  // locally and then 400 on every API call. Now the underscore is
+  // stripped.
+  it('addEnv strips underscores (api regex forbids them)', async () => {
+    const mod = await load()
+    const { result } = renderHook(() => mod.useDashboardCtx())
+    await waitFor(() => expect(result.current.me).not.toBeNull())
+    await act(async () => { mod.addEnv('my_env_name') })
+    // Underscore-stripped form is "myenvname" — the only valid api shape.
+    expect(result.current.envs.some((e: string) => e.includes('_'))).toBe(false)
+    expect(result.current.env).toMatch(/^[a-z0-9-]{1,32}$/)
+  })
+
+  // BUG-DASH-001 belt: a paste that's entirely punctuation must NOT
+  // change the live env. Pre-fix the empty-string fall-through worked
+  // because of `if (!clean)`; we keep that guard via the final regex
+  // gate.
+  it('addEnv leaves live env unchanged on all-invalid + over-cap input', async () => {
+    const mod = await load()
+    const { result } = renderHook(() => mod.useDashboardCtx())
+    await waitFor(() => expect(result.current.me).not.toBeNull())
+    const envBefore = result.current.env
+    await act(async () => { mod.addEnv('!!! !!! !!!') })
+    expect(result.current.env).toBe(envBefore)
+  })
+
   it('resetBootstrap clears state and allows a fresh bootstrap', async () => {
     const mod = await load()
     const { result, rerender } = renderHook(() => mod.useDashboardCtx())
diff --git a/src/hooks/useDashboardCtx.ts b/src/hooks/useDashboardCtx.ts
index 0b64723..0fb936d 100644
--- a/src/hooks/useDashboardCtx.ts
+++ b/src/hooks/useDashboardCtx.ts
@@ -88,9 +88,36 @@ export function setEnv(next: string) {
   refreshCounts()
 }
 
+// BUG-DASH-001 (P0) + BUG-DASH-002:
+//
+//   Pre-fix this function accepted env names of arbitrary length and
+//   stripped characters silently, then persisted the result to
+//   localStorage. A 67-char paste → every subsequent /api/v1/* call
+//   carried `?env=<67-char-name>` → vault 400 invalid_env, resources
+//   200 with empty list, no UI affordance to delete the bad value
+//   (user had to clear localStorage from devtools).
+//
+//   The api regex is `^[a-z0-9-]{1,32}$` (see api/internal/handlers/env.go
+//   + the `invalid_env` 400 branch). Underscores are NOT part of the
+//   api regex; the pre-fix JS regex `[^a-z0-9_-]` permitted them,
+//   producing names that the api would later reject — a different
+//   class of the same "client says yes, server says no" gap.
+//
+//   Fix: align the JS regex with the api regex, enforce the 32-char
+//   cap up front, and return early if validation fails. The caller
+//   (EnvSwitcher) already gates `addEnv` behind a non-empty draft so
+//   no UI plumbing changes are required.
+const ENV_REGEX = /^[a-z0-9-]{1,32}$/
+const ENV_MAX_LEN = 32
+
 export function addEnv(name: string) {
-  const clean = name.trim().toLowerCase().replace(/[^a-z0-9_-]/g, '')
-  if (!clean) return
+  // Lowercase + strip api-invalid chars; underscores no longer survive
+  // (BUG-DASH-002). Clip to the api cap of 32 chars (BUG-DASH-001).
+  const clean = name.trim().toLowerCase().replace(/[^a-z0-9-]/g, '').slice(0, ENV_MAX_LEN)
+  // Final regex gate: empty / leading-dash-only / any drift from the
+  // api regex → bail out without persisting. setEnv is NOT called, so
+  // the live env stays on the previous valid value (no broken state).
+  if (!ENV_REGEX.test(clean)) return
   if (!state.envs.includes(clean)) {
     state = { ...state, envs: [...state.envs, clean] }
     emit()