diff --git a/config/scripts/workflow/source-routing/pr-package-test-paths.mjs b/config/scripts/workflow/source-routing/pr-package-test-paths.mjs
index c0333d0e1cd..2bae139d3bb 100644
--- a/config/scripts/workflow/source-routing/pr-package-test-paths.mjs
+++ b/config/scripts/workflow/source-routing/pr-package-test-paths.mjs
@@ -170,6 +170,7 @@ export const WINDOWS_BOUNDARY_TESTS = [
   'src/shared/__tests__/process-host/windows-tree-kill-late-taskkill.win32.test.ts',
   'src/shared/agent-launch/startup/omp-fresh-launch-cmd.win32.test.ts',
   'src/shared/windows-batch-spawn.win32.test.ts',
+  'src/main/claude/structured/launch/claude-structured-child-env.test.ts',
   'src/main/agent-hooks/installation/commands/windows-hook-payload-delivery.test.ts',
   'src/main/agent-hooks/installation/scripts/managed-hook-stdin-lifecycle.test.ts',
   'src/main/jcode/hook-gate-script.test.ts',
diff --git a/src/main/acp/launch/acp-structured-launch-env.test.ts b/src/main/acp/launch/acp-structured-launch-env.test.ts
new file mode 100644
index 00000000000..7406980a391
--- /dev/null
+++ b/src/main/acp/launch/acp-structured-launch-env.test.ts
@@ -0,0 +1,32 @@
+import { afterEach, expect, it, vi } from 'vitest'
+import { acpLaunchSpecFor } from './acp-launch-registry'
+import { resolveAcpLaunchInvocation } from './acp-structured-launch-resolution'
+
+afterEach(() => vi.unstubAllGlobals())
+
+it('composes configured Windows values before ACP command lookup and account pinning', async () => {
+  vi.stubGlobal('process', { ...process, platform: 'win32' })
+  const spec = acpLaunchSpecFor('grok')
+  if (!spec) {
+    throw new Error('Missing Grok spec')
+  }
+  const launch = await resolveAcpLaunchInvocation(
+    { ...spec, installDirectories: () => [] },
+    { variable: 'GROK_HOME', path: '/pinned' },
+    {
+      dataDirectory: '/isolated',
+      inheritedEnv: {},
+      resolveEnvironment: async () => ({ PATH: '/inherited/bin', TOKEN: 'inherited' }),
+      resolveLaunchEnv: () => ({
+        path: '/configured/bin',
+        tOKEN: 'configured',
+        grok_home: '/configured/home'
+      }),
+      resolveCommand: (_command, options) => {
+        expect(options?.pathEnv).toBe('/configured/bin')
+        return '/configured/bin/grok.exe'
+      }
+    }
+  )
+  expect(launch.env).toEqual({ PATH: '/configured/bin', TOKEN: 'configured', GROK_HOME: '/pinned' })
+})
diff --git a/src/main/acp/launch/acp-structured-launch-resolution.ts b/src/main/acp/launch/acp-structured-launch-resolution.ts
index bbb290fe79e..b0e0cae43b7 100644
--- a/src/main/acp/launch/acp-structured-launch-resolution.ts
+++ b/src/main/acp/launch/acp-structured-launch-resolution.ts
@@ -1,4 +1,5 @@
 import { checkAcpLaunchVersion } from './acp-launch-version'
+import { overlayEnvironmentVariables } from '../../../shared/environment-overlay'
 
 import {
   assertStructuredAgentResolutionCurrent,
@@ -116,10 +117,10 @@ async function readAcpLaunchInvocation(
   assertStructuredAgentResolutionCurrent(deps.operation)
   const base = await deps.resolveEnvironment()
   assertStructuredAgentResolutionCurrent(deps.operation)
-  const env: Record<string, string> = spec.account.environment(accountHome, {
-    ...base,
-    ...deps.resolveLaunchEnv?.(spec.agent)
-  })
+  const env: Record<string, string> = spec.account.environment(
+    accountHome,
+    overlayEnvironmentVariables(base, deps.resolveLaunchEnv?.(spec.agent), process.platform)
+  )
   const envToDelete = spec.scrubEnvironment?.(env, deps.inheritedEnv ?? process.env) ?? []
   Object.assign(env, spec.env)
   const commandSettings = deps.resolveCommandSettings?.()
diff --git a/src/main/claude/structured/launch/claude-structured-child-env.test.ts b/src/main/claude/structured/launch/claude-structured-child-env.test.ts
index 18c73fc32e0..1db318f15ed 100644
--- a/src/main/claude/structured/launch/claude-structured-child-env.test.ts
+++ b/src/main/claude/structured/launch/claude-structured-child-env.test.ts
@@ -2,13 +2,18 @@ import { chmodSync, mkdtempSync, rmSync, writeFileSync } from 'node:fs'
 import { tmpdir } from 'node:os'
 import { join } from 'node:path'
 import { afterEach, expect, it, vi } from 'vitest'
+import { runProcess } from '@orca/process-host'
 import {
+  claudeChildEnv,
   resolveClaudeChildEnvSources,
   withOrcaClaudeEntrypoint
 } from './claude-structured-child-env'
 import { resolveStructuredAgentCommand } from '../../../native-chat/structured-agent-command-resolution'
 
-afterEach(() => vi.unstubAllEnvs())
+afterEach(() => {
+  vi.unstubAllEnvs()
+  vi.unstubAllGlobals()
+})
 
 it('resolves a custom Claude command against the login shell PATH', async () => {
   const root = mkdtempSync(join(tmpdir(), 'orca-shell-only-cli-'))
@@ -40,4 +45,59 @@ it('keeps a differently cased Windows launch value over the Orca default', () =>
     PATH: 'C:\\bin',
     CLAUDE_CODE_ENTRYPOINT: 'orca'
   })
+  expect(
+    withOrcaClaudeEntrypoint(
+      inherited,
+      {
+        CLAUDE_CODE_ENTRYPOINT: 'first',
+        claude_code_entrypoint: 'last'
+      },
+      'win32'
+    )
+  ).toEqual({ PATH: 'C:\\bin', CLAUDE_CODE_ENTRYPOINT: 'last' })
 })
+
+it('uses configured Windows values for both Claude lookup and its final child', async () => {
+  vi.stubGlobal('process', { ...process, platform: 'win32' })
+  const sources = await resolveClaudeChildEnvSources({
+    resolveInheritedEnv: async () => ({
+      PATH: '/inherited/bin',
+      TOKEN: 'inherited',
+      CLAUDE_CONFIG_DIR: '/ambient'
+    }),
+    resolveEnv: () => ({
+      path: '/configured/bin',
+      tOKEN: 'configured',
+      claude_config_dir: '/configured/home'
+    }),
+    resolveCommand: (options) => {
+      expect(options?.pathEnv).toBe('/configured/bin')
+      return { command: '/configured/bin/claude.exe', prefixArgs: [] }
+    }
+  })
+  expect(claudeChildEnv(sources, undefined, { runtimeOnPath: false })).toEqual({
+    PATH: '/configured/bin',
+    TOKEN: 'configured',
+    CLAUDE_CONFIG_DIR: '/configured/home',
+    CLAUDE_CODE_ENTRYPOINT: 'orca'
+  })
+})
+
+it.skipIf(process.platform !== 'win32')(
+  'passes configured values through a real Windows child despite inherited casing',
+  async () => {
+    vi.stubEnv('ORCA_NATIVE_ENV_CASE_PROBE', 'inherited')
+    const sources = await resolveClaudeChildEnvSources({
+      resolveEnv: () => ({ orca_native_env_case_probe: 'configured' }),
+      resolveCommand: () => ({ command: process.execPath, prefixArgs: [] })
+    })
+    const result = await runProcess({
+      program: sources.command,
+      args: ['--eval', 'process.stdout.write(process.env.ORCA_NATIVE_ENV_CASE_PROBE ?? "")'],
+      env: claudeChildEnv(sources, undefined, { runtimeOnPath: false }),
+      timeoutMs: 30_000
+    })
+    expect(result.code).toBe(0)
+    expect(result.stdout).toBe('configured')
+  }
+)
diff --git a/src/main/claude/structured/launch/claude-structured-child-env.ts b/src/main/claude/structured/launch/claude-structured-child-env.ts
index 7348c90c323..c63824523ba 100644
--- a/src/main/claude/structured/launch/claude-structured-child-env.ts
+++ b/src/main/claude/structured/launch/claude-structured-child-env.ts
@@ -12,6 +12,7 @@ import { withCliRuntimeOnPath } from '../../../../shared/node-cli-command-resolu
 import { applyClaudeEnvPatch } from '../../../claude-accounts/environment'
 import { resolveClaudeCommand } from '../../../codex-cli/command'
 import { withoutInheritedClaudeConfigDir } from '../../claude-config-dir-pin'
+import { overlayEnvironmentVariables } from '../../../../shared/environment-overlay'
 
 function cloneDefinedEnv(env: NodeJS.ProcessEnv | Record<string, string>): Record<string, string> {
   const next: Record<string, string> = {}
@@ -54,7 +55,8 @@ export function resolveClaudeChildEnvSources(deps: ClaudeEnvDeps): Promise<Claud
     () => readClaudeChildEnvSources(deps),
     deps.refreshEnvironmentAfterMiss,
     {
-      env: ({ inheritedEnv, overlay }) => ({ ...inheritedEnv, ...overlay }),
+      env: ({ inheritedEnv, overlay }) =>
+        overlayEnvironmentVariables(inheritedEnv, overlay, process.platform),
       cwd: deps.resolveWorkingDirectory,
       signal: deps.signal
     },
@@ -64,14 +66,20 @@ export function resolveClaudeChildEnvSources(deps: ClaudeEnvDeps): Promise<Claud
 
 async function readClaudeChildEnvSources(deps: ClaudeEnvDeps): Promise<ClaudeChildEnvSources> {
   assertStructuredAgentResolutionCurrent(deps.operation)
-  const overlay = await waitForPromiseWithSignal(Promise.resolve(deps.resolveEnv?.()), deps.signal)
+  const configured = await waitForPromiseWithSignal(
+    Promise.resolve(deps.resolveEnv?.()),
+    deps.signal
+  )
+  const overlay = configured
+    ? overlayEnvironmentVariables({}, cloneDefinedEnv(configured), process.platform)
+    : undefined
   assertStructuredAgentResolutionCurrent(deps.operation)
   const inheritedEnv = deps.resolveInheritedEnv
     ? await waitForPromiseWithSignal(deps.resolveInheritedEnv(), deps.signal)
     : cloneDefinedEnv(process.env)
   assertStructuredAgentResolutionCurrent(deps.operation)
   deps.signal?.throwIfAborted()
-  const effectiveEnv = { ...inheritedEnv, ...overlay }
+  const effectiveEnv = overlayEnvironmentVariables(inheritedEnv, overlay, process.platform)
   const options = {
     pathEnv: effectiveEnv.PATH ?? effectiveEnv.Path ?? null,
     homePath: effectiveEnv.HOME ?? effectiveEnv.USERPROFILE
@@ -95,13 +103,12 @@ export function withOrcaClaudeEntrypoint(
     (platform === 'win32' ? key.toUpperCase() : key) === CLAUDE_ENTRYPOINT_ENV
   const withoutEntrypoint = (source: Record<string, string>): Record<string, string> =>
     Object.fromEntries(Object.entries(source).filter(([key]) => !isEntrypointKey(key)))
-  const override = Object.entries(overlay ?? {}).find(([key]) => isEntrypointKey(key))?.[1]
   // The SDK reads only the exact name and otherwise adds its own default, which Windows would pick.
-  return {
-    ...withoutEntrypoint(inheritedEnv),
-    ...withoutEntrypoint(overlay ?? {}),
-    [CLAUDE_ENTRYPOINT_ENV]: override ?? 'orca'
-  }
+  return overlayEnvironmentVariables(
+    { ...withoutEntrypoint(inheritedEnv), [CLAUDE_ENTRYPOINT_ENV]: 'orca' },
+    overlay,
+    platform
+  )
 }
 
 // Merge onto the shell environment to retain PATH and ambient Anthropic auth.
diff --git a/src/main/codex/structured/catalog/codex-model-catalog-probe.test.ts b/src/main/codex/structured/catalog/codex-model-catalog-probe.test.ts
index 47779af453c..3fe0e337ea9 100644
--- a/src/main/codex/structured/catalog/codex-model-catalog-probe.test.ts
+++ b/src/main/codex/structured/catalog/codex-model-catalog-probe.test.ts
@@ -1,4 +1,4 @@
-import { describe, expect, it, vi } from 'vitest'
+import { afterEach, describe, expect, it, vi } from 'vitest'
 import { createCodexModelCatalogProbe } from './codex-model-catalog-probe'
 import {
   runCodexAppServerSession,
@@ -14,6 +14,46 @@ const MODEL_ROW = {
   isDefault: true
 }
 
+afterEach(() => vi.unstubAllGlobals())
+
+it.each(['saved', 'recover'] as const)(
+  'composes the Windows %s catalog environment before lookup and listing',
+  async (lookup) => {
+    vi.stubGlobal('process', { ...process, platform: 'win32' })
+    const probe = createCodexModelCatalogProbe({
+      resolveEnvironment: async () => ({ PATH: '/inherited/bin', TOKEN: 'inherited' }),
+      resolveSavedEnvironment: async () => ({ PATH: '/saved/bin', TOKEN: 'saved' }),
+      resolveEnv: () => ({
+        path: '/configured/bin',
+        tOKEN: 'configured',
+        codex_home: '/configured/home'
+      }),
+      resolveCommand: (options) => {
+        expect(options?.pathEnv).toBe('/configured/bin')
+        return { command: '/configured/bin/codex.exe', prefixArgs: [] }
+      },
+      runSession: async (invocation, body) => {
+        expect(invocation.env).toEqual({
+          PATH: '/configured/bin',
+          TOKEN: 'configured',
+          CODEX_HOME: '/pinned'
+        })
+        return body({
+          request: async (method: string) =>
+            method === 'config/read' ? { config: {} } : { data: [MODEL_ROW], nextCursor: null },
+          notify: () => {}
+        })
+      }
+    })
+    const resolved = await probe.resolve?.(
+      { variable: 'CODEX_HOME', path: '/pinned' },
+      '/probe',
+      lookup
+    )
+    expect((await resolved?.run())?.models[0]?.id).toBe('gpt-live')
+  }
+)
+
 describe('codex model catalog probe', () => {
   it.each([[[]]])(
     "lists a command line with arguments %j from Orca's folder for every chat",
diff --git a/src/main/codex/structured/catalog/codex-model-catalog-probe.ts b/src/main/codex/structured/catalog/codex-model-catalog-probe.ts
index dc72b22ea32..fe4b82a24a2 100644
--- a/src/main/codex/structured/catalog/codex-model-catalog-probe.ts
+++ b/src/main/codex/structured/catalog/codex-model-catalog-probe.ts
@@ -3,6 +3,7 @@ import {
   type StructuredAgentResolutionOperation
 } from '../../../native-chat/structured-agent-command-resolution'
 import { codexStructuredLaunchArgs } from '../launch/codex-structured-launch-args'
+import { overlayEnvironmentVariables } from '../../../../shared/environment-overlay'
 import { envWithPathRelativeTo } from '../../../../shared/node-cli-command-resolution'
 import type { AgentSessionAccountKind } from '../../../../shared/agent-session/agent-session-availability'
 import { AgentModelCatalogUnavailableError } from '../../../native-chat/agent-model-catalog/agent-model-catalog-unavailable'
@@ -57,13 +58,14 @@ export function createCodexModelCatalogProbe(
   ) => {
     assertStructuredAgentResolutionCurrent(operation)
     const accountHomePath = requireLegacyAgentSessionAccountHome(accountHome).path
-    const overlay = { ...deps.resolveEnv?.() }
+    const overlay = overlayEnvironmentVariables({}, deps.resolveEnv?.(), process.platform)
     const readEnvironment =
       lookup === 'saved' ? deps.resolveSavedEnvironment : deps.resolveEnvironment
     const { command, prefixArgs, environment } = await resolveCodexStructuredInvocation({
       ...deps,
       operation,
-      resolveEnvironment: async () => ({ ...(await readEnvironment?.()), ...overlay }),
+      resolveEnvironment: async () =>
+        overlayEnvironmentVariables((await readEnvironment?.()) ?? {}, overlay, process.platform),
       ...(lookup === 'recover' ? {} : { refreshEnvironmentAfterMiss: undefined }),
       ...(launchDirectory ? { resolveWorkingDirectory: () => launchDirectory } : {})
     })
diff --git a/src/main/runtime/agent-session/environment/structured-agent-environment-overrides.test.ts b/src/main/runtime/agent-session/environment/structured-agent-environment-overrides.test.ts
new file mode 100644
index 00000000000..1a31295d11e
--- /dev/null
+++ b/src/main/runtime/agent-session/environment/structured-agent-environment-overrides.test.ts
@@ -0,0 +1,26 @@
+import { afterEach, expect, it, vi } from 'vitest'
+import { createStructuredAgentEnvironmentResolvers } from './structured-agent-shell-environment'
+
+afterEach(() => vi.unstubAllGlobals())
+
+it.each([
+  ['win32', { TOKEN: 'configured', PATH: '/configured/bin', KEEP: 'keep' }],
+  [
+    'linux',
+    {
+      TOKEN: 'inherited',
+      PATH: '/inherited/bin',
+      tOKEN: 'configured',
+      path: '/configured/bin',
+      KEEP: 'keep'
+    }
+  ]
+] as const)('composes the effective agent environment on %s', async (platform, expected) => {
+  vi.stubGlobal('process', { ...process, platform })
+  const environment = createStructuredAgentEnvironmentResolvers({
+    resolveEnvironment: async () => ({ TOKEN: 'inherited', PATH: '/inherited/bin', KEEP: 'keep' }),
+    resolveAgentLaunchEnv: () => ({ tOKEN: 'configured', path: '/configured/bin' })
+  })
+  expect(await environment.resolveAgentEnvironment('claude')).toEqual(expected)
+  expect(await environment.resolveAgentEnvironment('codex')).toEqual(expected)
+})
diff --git a/src/main/runtime/agent-session/environment/structured-agent-shell-environment-catalog.test.ts b/src/main/runtime/agent-session/environment/structured-agent-shell-environment-catalog.test.ts
index 1c0a13e22b6..87bd9cad5e9 100644
--- a/src/main/runtime/agent-session/environment/structured-agent-shell-environment-catalog.test.ts
+++ b/src/main/runtime/agent-session/environment/structured-agent-shell-environment-catalog.test.ts
@@ -40,13 +40,14 @@ const cleanups: (() => void)[] = []
 afterEach(() => {
   cleanups.splice(0).forEach((stop) => stop())
   vi.restoreAllMocks()
+  vi.unstubAllGlobals()
   shell.current = { PATH: '/a', IGNORED: 'a' }
   shell.next = { ...shell.current }
   shell.saved = []
   shell.nextSaved = []
 })
 
-function rig() {
+function rig(overlay?: Record<string, string>) {
   const record = {
     ...agentSessionRecordFixture(),
     provider: 'grok',
@@ -67,7 +68,8 @@ function rig() {
     workspaceMayOverrideDefaultModel: defaults
   })
   const environment = createStructuredAgentEnvironmentResolvers({
-    resolveShellEnvironmentPolicy: () => ({ inheritAll: false, names: [] })
+    resolveShellEnvironmentPolicy: () => ({ inheritAll: false, names: [] }),
+    resolveAgentLaunchEnv: () => overlay ?? {}
   })
   cleanups.push(service.stop, environment.bindCatalogSources(['grok']))
   const listing = (id: string) => ({
@@ -84,6 +86,22 @@ function rig() {
   }
 }
 
+it('keeps a Windows catalog source while only a shadowed inherited path changes', async () => {
+  vi.stubGlobal('process', { ...process, platform: 'win32' })
+  const overlay = { path: '/configured/bin' }
+  const h = rig(overlay)
+  const source = h.service.captureSource(h.record)
+  cleanups.push(() => source.release?.())
+  await captureHostShellEnvironment(async () => {
+    shell.next = { PATH: '/changed', IGNORED: 'a' }
+  })
+  expect(source()).toBe(true)
+  await captureHostShellEnvironment(async () => {
+    overlay.path = '/new-configured/bin'
+  })
+  expect(source()).toBe(false)
+})
+
 it('retires a producer on effective Refresh before new publication and fences late defaults and new old reports', async () => {
   const h = rig()
   await agentModelCatalogStore.attachPersistence({
diff --git a/src/main/runtime/agent-session/environment/structured-agent-shell-environment.ts b/src/main/runtime/agent-session/environment/structured-agent-shell-environment.ts
index b4996cff6ff..e050391680d 100644
--- a/src/main/runtime/agent-session/environment/structured-agent-shell-environment.ts
+++ b/src/main/runtime/agent-session/environment/structured-agent-shell-environment.ts
@@ -11,6 +11,7 @@ import {
   resolvePathEnvKey
 } from '../../../pty/environment/windows-path-segment-merge'
 import type { GlobalSettings } from '../../../../shared/global-settings-types'
+import { overlayEnvironmentVariables } from '../../../../shared/environment-overlay'
 import {
   nativeChatShellEnvironmentPolicy,
   type NativeChatShellEnvironmentPolicy
@@ -29,24 +30,6 @@ function definedEnv(env: NodeJS.ProcessEnv): Record<string, string> {
   return defined
 }
 
-/** Overlays shell variables on Orca's env; win32 names are case-insensitive, so drop the base spelling. */
-function overlayShellVariables(
-  base: Record<string, string>,
-  shellVariables: Record<string, string>,
-  platform: NodeJS.Platform
-): Record<string, string> {
-  const merged = { ...base }
-  if (platform === 'win32') {
-    const overlaid = new Set(Object.keys(shellVariables).map((key) => key.toUpperCase()))
-    for (const key of Object.keys(merged)) {
-      if (overlaid.has(key.toUpperCase())) {
-        delete merged[key]
-      }
-    }
-  }
-  return { ...merged, ...shellVariables }
-}
-
 function pickShellVariables(
   shellEnv: NodeJS.ProcessEnv,
   names: readonly string[],
@@ -78,7 +61,7 @@ export function structuredAgentBaseEnvironment(input: {
     return definedEnv(input.shellEnv)
   }
   const platform = input.platform ?? process.platform
-  return overlayShellVariables(
+  return overlayEnvironmentVariables(
     definedEnv(input.processEnv ?? process.env),
     pickShellVariables(input.shellEnv, input.policy.names, platform),
     platform
@@ -246,7 +229,11 @@ export function createStructuredAgentEnvironmentResolvers(
           const base = structuredAgentBaseEnvironment({ shellEnv, policy, processEnv })
           return new Map(
             agents.map((agent) => {
-              const effective = { ...base, ...overlays.get(agent) }
+              const effective = overlayEnvironmentVariables(
+                base,
+                overlays.get(agent),
+                process.platform
+              )
               return [agent, structuredAgentEnvironmentIdentity(effective)]
             })
           )
@@ -258,10 +245,12 @@ export function createStructuredAgentEnvironmentResolvers(
       }
     },
     resolveBaseEnvironment: resolveBase,
-    resolveAgentEnvironment: async (agent) => ({
-      ...(await resolveBase()),
-      ...sources.resolveAgentLaunchEnv?.(agent)
-    })
+    resolveAgentEnvironment: async (agent) =>
+      overlayEnvironmentVariables(
+        await resolveBase(),
+        sources.resolveAgentLaunchEnv?.(agent),
+        process.platform
+      )
   }
 }
 
diff --git a/src/main/runtime/agent-session/installation/runtime-structured-agent-host-env.test.ts b/src/main/runtime/agent-session/installation/runtime-structured-agent-host-env.test.ts
new file mode 100644
index 00000000000..744e51d8736
--- /dev/null
+++ b/src/main/runtime/agent-session/installation/runtime-structured-agent-host-env.test.ts
@@ -0,0 +1,34 @@
+import { afterEach, expect, it, vi } from 'vitest'
+import { RuntimeStructuredAgentHost } from './runtime-structured-agent-host'
+import { resolveStructuredClaudeAccountHomePath } from '../environment/structured-agent-account-home'
+
+vi.mock('../../terminal/wait/terminal-wait-visible-probe', () => ({
+  OrcaRuntimeWithStartTuiIdleVisibleReadProbe: class {}
+}))
+afterEach(() => vi.unstubAllGlobals())
+
+abstract class LaunchRuntime extends RuntimeStructuredAgentHost {
+  configuredEnvironment() {
+    return this.structuredAgentLaunchEnv('claude', {
+      agentDefaultEnv: { claude: { claude_config_dir: '/configured/home' } }
+    })
+  }
+}
+
+it('uses the same configured Windows home for account identity, then honors the host account', async () => {
+  vi.stubGlobal('process', { ...process, platform: 'win32' })
+  let host: Record<string, string> = {}
+  const runtime: LaunchRuntime = Object.assign(Object.create(LaunchRuntime.prototype), {
+    accounts: { hostLaunchEnvFor: () => host }
+  })
+  const accountHome = () =>
+    resolveStructuredClaudeAccountHomePath({
+      launchEnv: runtime.configuredEnvironment(),
+      wslDistro: null,
+      getClaudeConfigDirectory: () => '/fallback/home'
+    })
+  expect(await accountHome()).toBe('/configured/home')
+  host = { CLAUDE_CONFIG_DIR: '/host/home' }
+  expect(runtime.configuredEnvironment()).toEqual({ CLAUDE_CONFIG_DIR: '/host/home' })
+  expect(await accountHome()).toBe('/host/home')
+})
diff --git a/src/main/runtime/agent-session/installation/runtime-structured-agent-host.ts b/src/main/runtime/agent-session/installation/runtime-structured-agent-host.ts
index faea7c1089d..4bc70ab1968 100644
--- a/src/main/runtime/agent-session/installation/runtime-structured-agent-host.ts
+++ b/src/main/runtime/agent-session/installation/runtime-structured-agent-host.ts
@@ -8,6 +8,7 @@ import { structuredAgentConfiguredArgs } from '../../../native-chat/structured-a
 import { getProfileUserDataPath } from '../../../orca-profiles/profile-storage-paths'
 import { isTuiAgent } from '../../../../shared/agent-launch/catalog/tui-agent-config'
 import { resolveTuiAgentLaunchEnv } from '../../../../shared/agent-launch/choices/tui-agent-launch-defaults'
+import { overlayEnvironmentVariables } from '../../../../shared/environment-overlay'
 import type { GlobalSettings } from '../../../../shared/global-settings-types'
 import type { StructuredAgentId } from '../../../../shared/agent-session/lifecycle/agent-session-provider-handle'
 import type { RuntimeWorkspaceCatalog } from '../../workspaces/catalog/workspace-catalog'
@@ -25,10 +26,11 @@ export abstract class RuntimeStructuredAgentHost extends OrcaRuntimeWithStartTui
     agent: StructuredAgentId,
     settings: Pick<GlobalSettings, 'agentDefaultEnv'>
   ) {
-    return {
-      ...resolveTuiAgentLaunchEnv(agent, settings),
-      ...this.accounts.hostLaunchEnvFor(agent)
-    }
+    return overlayEnvironmentVariables(
+      overlayEnvironmentVariables({}, resolveTuiAgentLaunchEnv(agent, settings), process.platform),
+      this.accounts.hostLaunchEnvFor(agent),
+      process.platform
+    )
   }
 
   protected structuredAgentCatalogDependencies(): StructuredAgentModelCatalogDeps {
diff --git a/src/main/runtime/agent-session/launch/structured-agent-launch-env-preflight.test.ts b/src/main/runtime/agent-session/launch/structured-agent-launch-env-preflight.test.ts
new file mode 100644
index 00000000000..41906268caa
--- /dev/null
+++ b/src/main/runtime/agent-session/launch/structured-agent-launch-env-preflight.test.ts
@@ -0,0 +1,21 @@
+import { afterEach, expect, it, vi } from 'vitest'
+import { resolveHostStructuredAgentLaunchEnvironment } from './structured-agent-launch-support'
+import type * as Environment from '../environment/structured-agent-shell-environment'
+
+vi.mock('../environment/structured-agent-shell-environment', async (importOriginal) => ({
+  ...(await importOriginal<typeof Environment>()),
+  resolveHostAgentBaseEnvironment: async () => ({
+    TOKEN: 'inherited',
+    PATH: '/inherited/bin',
+    KEEP: 'keep'
+  })
+}))
+afterEach(() => vi.unstubAllGlobals())
+
+it('uses the configured Windows environment for launch preflight', async () => {
+  vi.stubGlobal('process', { ...process, platform: 'win32' })
+  const env = await resolveHostStructuredAgentLaunchEnvironment('claude', {
+    agentDefaultEnv: { claude: { tOKEN: 'configured', path: '/configured/bin' } }
+  })
+  expect(env).toEqual({ TOKEN: 'configured', PATH: '/configured/bin', KEEP: 'keep' })
+})
diff --git a/src/main/runtime/agent-session/launch/structured-agent-launch-support.ts b/src/main/runtime/agent-session/launch/structured-agent-launch-support.ts
index 16e51d3da17..d6c402cb949 100644
--- a/src/main/runtime/agent-session/launch/structured-agent-launch-support.ts
+++ b/src/main/runtime/agent-session/launch/structured-agent-launch-support.ts
@@ -1,6 +1,7 @@
 import type { AgentSessionExecutionLocation } from '../../../../shared/agent-session/lifecycle/agent-session-record'
 import type { StructuredAgentId } from '../../../../shared/agent-session/lifecycle/agent-session-provider-handle'
 import type { GlobalSettings } from '../../../../shared/global-settings-types'
+import { overlayEnvironmentVariables } from '../../../../shared/environment-overlay'
 import { isTuiAgent } from '../../../../shared/agent-launch/catalog/tui-agent-config'
 import {
   resolveTuiAgentLaunchEnv,
@@ -101,10 +102,11 @@ export async function resolveHostStructuredAgentLaunchEnvironment(
   agent: string,
   settings: LaunchEnvironmentSettings
 ): Promise<Record<string, string>> {
-  return {
-    ...(await resolveHostAgentBaseEnvironment(settings)),
-    ...(isTuiAgent(agent) ? resolveTuiAgentLaunchEnv(agent, settings) : {})
-  }
+  return overlayEnvironmentVariables(
+    await resolveHostAgentBaseEnvironment(settings),
+    isTuiAgent(agent) ? resolveTuiAgentLaunchEnv(agent, settings) : undefined,
+    process.platform
+  )
 }
 
 /** What a chat start of `agent` on this host launches from, for a child that serves no chat. */
diff --git a/src/main/runtime/agent-session/naming/structured-chat-naming-agent-launch.test.ts b/src/main/runtime/agent-session/naming/structured-chat-naming-agent-launch.test.ts
new file mode 100644
index 00000000000..4592b0590c1
--- /dev/null
+++ b/src/main/runtime/agent-session/naming/structured-chat-naming-agent-launch.test.ts
@@ -0,0 +1,27 @@
+import { afterEach, expect, it, vi } from 'vitest'
+import { agentSessionRecordFixture } from '../../../../shared/agent-session/lifecycle/agent-session-record.test-fixture'
+import { chatNamingAgentTarget } from './structured-chat-naming-agent-launch'
+
+afterEach(() => vi.unstubAllGlobals())
+
+it('reapplies configured Windows naming variables and keeps the recorded account pin', async () => {
+  vi.stubGlobal('process', { ...process, platform: 'win32' })
+  const target = await chatNamingAgentTarget(
+    agentSessionRecordFixture(),
+    '/workspace',
+    async () => ({
+      TOKEN: 'inherited',
+      PATH: '/inherited/bin',
+      CLAUDE_CONFIG_DIR: '/ambient/home'
+    }),
+    { agentDefaultEnv: { claude: { tOKEN: 'configured', path: '/configured/bin' } } }
+  )
+  if (target.kind !== 'local') {
+    throw new Error('Naming did not resolve a local launch')
+  }
+  expect(target.env).toEqual({
+    TOKEN: 'configured',
+    PATH: '/configured/bin',
+    CLAUDE_CONFIG_DIR: '/home/user/.claude'
+  })
+})
diff --git a/src/main/runtime/agent-session/naming/structured-chat-naming-agent-launch.ts b/src/main/runtime/agent-session/naming/structured-chat-naming-agent-launch.ts
index 56c13c34fd8..24f0049e695 100644
--- a/src/main/runtime/agent-session/naming/structured-chat-naming-agent-launch.ts
+++ b/src/main/runtime/agent-session/naming/structured-chat-naming-agent-launch.ts
@@ -1,6 +1,7 @@
 import type { AgentSessionRecord } from '../../../../shared/agent-session/lifecycle/agent-session-record'
 import { requireLegacyAgentSessionAccountHome } from '../../../../shared/agent-session/lifecycle/agent-session-account-home'
 import { resolveTuiAgentLaunchEnv } from '../../../../shared/agent-launch/choices/tui-agent-launch-defaults'
+import { overlayEnvironmentVariables } from '../../../../shared/environment-overlay'
 import { acpLaunchSpecFor } from '../../../acp/launch/acp-launch-registry'
 import { getClaudeProfileRouter } from '../../../claude-accounts/claude-profile-installed-router'
 import {
@@ -30,10 +31,11 @@ export async function chatNamingAgentTarget(
   }
   const home = requireLegacyAgentSessionAccountHome(record.accountHome)
   if (record.provider === 'claude') {
-    env = {
-      ...withoutInheritedClaudeConfigDir(env),
-      ...resolveTuiAgentLaunchEnv('claude', settings)
-    }
+    env = overlayEnvironmentVariables(
+      withoutInheritedClaudeConfigDir(env),
+      resolveTuiAgentLaunchEnv('claude', settings),
+      process.platform
+    )
     const path = await resolveClaudeStructuredLaunchHome(getClaudeProfileRouter(), env, home.path)
     const patch = claudeConfigDirEnvPatch(path, { env })
     return { kind: 'local', cwd, env: { CLAUDE_CONFIG_DIR: undefined, ...env, ...patch } }
diff --git a/src/shared/environment-overlay.test.ts b/src/shared/environment-overlay.test.ts
new file mode 100644
index 00000000000..fa0522547c7
--- /dev/null
+++ b/src/shared/environment-overlay.test.ts
@@ -0,0 +1,27 @@
+import { expect, it } from 'vitest'
+import { overlayEnvironmentVariables } from './environment-overlay'
+
+it('replaces Windows aliases in configured order while preserving untouched inherited names', () => {
+  const base = { TOKEN: 'old', Token: 'also old', PATH: 'first', Path: 'second', KEEP: 'keep' }
+  const configured = { token: 'first override', tOKEN: '', Custom: 'configured' }
+  expect(overlayEnvironmentVariables(base, configured, 'win32')).toEqual({
+    PATH: 'first',
+    Path: 'second',
+    KEEP: 'keep',
+    TOKEN: '',
+    CUSTOM: 'configured'
+  })
+  expect(Object.entries(base)).toEqual([
+    ['TOKEN', 'old'],
+    ['Token', 'also old'],
+    ['PATH', 'first'],
+    ['Path', 'second'],
+    ['KEEP', 'keep']
+  ])
+  expect(configured).toEqual({ token: 'first override', tOKEN: '', Custom: 'configured' })
+  expect(overlayEnvironmentVariables(base, undefined, 'win32')).toEqual(base)
+  expect(overlayEnvironmentVariables({ TOKEN: 'old' }, { token: 'new' }, 'linux')).toEqual({
+    TOKEN: 'old',
+    token: 'new'
+  })
+})
diff --git a/src/shared/environment-overlay.ts b/src/shared/environment-overlay.ts
new file mode 100644
index 00000000000..29ef2a637ce
--- /dev/null
+++ b/src/shared/environment-overlay.ts
@@ -0,0 +1,22 @@
+/** Windows children select the first sorted alias, so configured names must replace every alias. */
+export function overlayEnvironmentVariables<T extends string | undefined>(
+  base: Readonly<Record<string, T>>,
+  overrides: Readonly<Record<string, T>> | undefined,
+  platform: NodeJS.Platform
+): Record<string, T> {
+  if (platform !== 'win32') {
+    return { ...base, ...overrides }
+  }
+  const normalized: Record<string, T> = {}
+  for (const [key, value] of Object.entries(overrides ?? {})) {
+    normalized[key.toUpperCase()] = value
+  }
+  const overlaid = new Set(Object.keys(normalized))
+  const merged = { ...base }
+  for (const key of Object.keys(merged)) {
+    if (overlaid.has(key.toUpperCase())) {
+      delete merged[key]
+    }
+  }
+  return { ...merged, ...normalized }
+}