diff --git a/test/client.test.js b/test/client.test.js
new file mode 100644
index 0000000..811577b
--- /dev/null
+++ b/test/client.test.js
@@ -0,0 +1,298 @@
+/**
+ * Tests for the browser half.
+ *
+ * There is no browser here, so the bundle is evaluated the way the real module
+ * loader would — inside `window.__ModuleLoader__.load` — with a fake `require`
+ * that supplies React and THROWS on anything else. That last part is the useful
+ * one: it proves the bundle stays inside the platform's seed table, which is the
+ * constraint a hand-written client half is most likely to break.
+ *
+ * The card is then rendered by calling the registered component and expanding
+ * the elements it returns, and its handlers are driven directly. That is not a
+ * substitute for looking at it in a browser, but it does check the wiring the
+ * card cannot work without.
+ */
+
+import assert from 'node:assert/strict'
+import { readFileSync } from 'node:fs'
+import { test } from 'node:test'
+
+const SOURCE = readFileSync(new URL('../client/client.js', import.meta.url), 'utf8')
+
+/** Minimal React: enough for createElement plus the three hooks the card uses. */
+function makeFakeReact() {
+  const states = []
+  let cursor = 0
+  return {
+    reset() {
+      cursor = 0
+    },
+    api: {
+      createElement: (type, props, ...children) => ({ type, props: props ?? {}, children }),
+      useState(initial) {
+        const index = cursor
+        cursor += 1
+        if (!(index in states)) states[index] = typeof initial === 'function' ? initial() : initial
+        return [
+          states[index],
+          (next) => {
+            states[index] = typeof next === 'function' ? next(states[index]) : next
+          },
+        ]
+      },
+      useEffect() {},
+      useMemo(factory) {
+        return factory()
+      },
+    },
+  }
+}
+
+/** Evaluate the bundle against a fake loader and return its exports. */
+function loadBundle() {
+  let loaded
+  const window = { __ModuleLoader__: { load: (spec) => { loaded = spec } } }
+  new Function('window', SOURCE)(window)
+  assert.ok(loaded !== undefined, 'the bundle must call window.__ModuleLoader__.load')
+  const react = makeFakeReact()
+  const exported = loaded.factory((name) => {
+    if (name === 'react') return react.api
+    throw new Error(`the client bundle required "${name}", which is not in the platform seed table`)
+  })
+  return { id: loaded.id, exported, react }
+}
+
+/**
+ * Resolve function components by calling them, until a host element or null.
+ *
+ * This is the whole "renderer": the slot hands back an element whose type is the
+ * card component, and function-typed children are expanded the same way.
+ */
+function expand(node, depth = 0) {
+  if (depth > 50) throw new Error('the component tree did not settle')
+  if (node === null || node === undefined) return null
+  if (typeof node !== 'object') return node
+  if (Array.isArray(node)) return node
+  if (typeof node.type === 'function') return expand(node.type(node.props), depth + 1)
+  return node
+}
+
+/** Depth-first walk over a rendered tree, expanding components as it goes. */
+function findAll(node, predicate, out = []) {
+  if (node === null || node === undefined) return out
+  if (Array.isArray(node)) {
+    for (const child of node) findAll(child, predicate, out)
+    return out
+  }
+  if (typeof node !== 'object') return out
+  if (typeof node.type === 'function') {
+    findAll(expand(node), predicate, out)
+    return out
+  }
+  if (predicate(node)) out.push(node)
+  for (const child of node.children ?? []) findAll(child, predicate, out)
+  return out
+}
+
+function textOf(node) {
+  if (typeof node === 'string') return node
+  if (node === null || node === undefined || typeof node !== 'object') return ''
+  if (Array.isArray(node)) return node.map(textOf).join('')
+  return (node.children ?? []).map(textOf).join('')
+}
+
+/** A SettingsScope stand-in recording the writes it was asked to make. */
+function fakeScope(snapshot) {
+  const calls = { set: [], unset: [] }
+  return {
+    calls,
+    getSnapshot: () => snapshot,
+    subscribe: () => () => {},
+    set: async (field, value) => {
+      calls.set.push([field, value])
+    },
+    unset: async (field) => {
+      calls.unset.push(field)
+    },
+  }
+}
+
+const READY = {
+  status: 'ready',
+  value: { embeddingModel: '', embeddingDimensions: 0 },
+  user: {},
+  base: {},
+  revision: 1,
+  writable: true,
+  mode: 'host',
+}
+
+/** Register the card the way the host would, and hand back its component. */
+function registered() {
+  const { id, exported, react } = loadBundle()
+  let registration
+  let render
+  const ctx = {
+    inject(deps, callback) {
+      assert.deepEqual(deps, ['settingsScope'])
+      callback({
+        settingsScope: { bind: () => fakeScope(READY) },
+        slots: {
+          inject(_name, produce) {
+            produce()
+          },
+          register(options, component) {
+            registration = options
+            render = component
+          },
+        },
+      })
+    },
+  }
+  exported.apply(ctx)
+  const draw = (scope) => expand(render({ scope }))
+  return { id, exported, react, registration, render, draw }
+}
+
+const inputFor = (tree, label) =>
+  findAll(tree, (node) => node.type === 'input' && node.props['aria-label'] === label)[0]
+
+const buttonStartingWith = (tree, prefix) =>
+  findAll(tree, (node) => node.type === 'button' && textOf(node).startsWith(prefix))[0]
+
+test('the bundle id matches the package name the loader is told about', () => {
+  const { id } = loadBundle()
+  assert.equal(id, 'dsh-slopo')
+})
+
+test('the client bundle requires nothing outside the platform seed table', () => {
+  // loadBundle() throws on any specifier other than react.
+  assert.doesNotThrow(() => loadBundle())
+})
+
+test('applying registers exactly one settings.plugin.item card, keyed on the namespace', () => {
+  const { registration, exported } = registered()
+  assert.equal(exported.name, 'dsh-slopo')
+  assert.deepEqual(exported.inject, ['slots'])
+  assert.equal(registration.name, 'settings.plugin.item')
+  // The key must equal the Host namespace, or the tab never dispatches the card.
+  assert.equal(registration.key, 'dsh-slopo')
+})
+
+test('the card renders a control for every setting the Host accepts', () => {
+  const { draw } = registered()
+  const tree = draw(fakeScope(READY))
+  const labels = findAll(tree, (node) => node.type === 'label').map(textOf)
+  for (const expected of [
+    'Embedding model',
+    'Embedding dimensions',
+    'Embedding API base',
+    'Embedding API key',
+    'Extra embedding parameters',
+    'slopo executable',
+    'Source directory',
+    'Exclude patterns',
+    'State directory',
+    'Ignore file',
+    'Foreground timeout',
+  ]) {
+    assert.ok(
+      labels.some((label) => label.includes(expected)),
+      `no control labelled "${expected}"`,
+    )
+  }
+})
+
+test('the API key is rendered as a password field', () => {
+  const { draw } = registered()
+  const tree = draw(fakeScope(READY))
+  assert.equal(inputFor(tree, 'Embedding API key').props.type, 'password')
+})
+
+test('the card renders nothing when the namespace is unavailable', () => {
+  const { draw } = registered()
+  assert.equal(draw(fakeScope({ ...READY, status: 'unavailable' })), null)
+})
+
+test('editing a field marks the card dirty and saving writes it through set()', async () => {
+  const { draw, react } = registered()
+  const scope = fakeScope(READY)
+
+  inputFor(draw(scope), 'Embedding model').props.onChange({ target: { value: 'ollama/example:latest' } })
+
+  // Re-render the way a state update would.
+  react.reset()
+  const tree = draw(scope)
+  const save = buttonStartingWith(tree, 'Save')
+  assert.equal(save.props.disabled, false, 'a changed field must enable Save')
+  await save.props.onClick()
+
+  assert.deepEqual(scope.calls.set, [['embeddingModel', 'ollama/example:latest']])
+  assert.deepEqual(scope.calls.unset, [])
+})
+
+test('a whole number field is sent as a number, not the string the input holds', async () => {
+  const { draw, react } = registered()
+  const scope = fakeScope(READY)
+  inputFor(draw(scope), 'Embedding dimensions').props.onChange({ target: { value: '768' } })
+  react.reset()
+  await buttonStartingWith(draw(scope), 'Save').props.onClick()
+  assert.deepEqual(scope.calls.set, [['embeddingDimensions', 768]])
+})
+
+test('clearing a field is an unset, so it re-inherits rather than becoming empty', async () => {
+  const { draw, react } = registered()
+  const scope = fakeScope({ ...READY, value: { embeddingModel: 'ollama/old:latest', embeddingDimensions: 768 } })
+  inputFor(draw(scope), 'Embedding model').props.onChange({ target: { value: '' } })
+  react.reset()
+  await buttonStartingWith(draw(scope), 'Save').props.onClick()
+  assert.deepEqual(scope.calls.unset, ['embeddingModel'])
+  assert.deepEqual(scope.calls.set, [], 'a cleared field must not be written as an empty string')
+})
+
+test('an exclude list round-trips through comma-separated text', async () => {
+  const { draw, react } = registered()
+  const scope = fakeScope({ ...READY, value: { embeddingModel: 'm', embeddingDimensions: 1 } })
+  inputFor(draw(scope), 'Exclude patterns').props.onChange({ target: { value: '**/test/**, *.min.js' } })
+  react.reset()
+  await buttonStartingWith(draw(scope), 'Save').props.onClick()
+  assert.deepEqual(scope.calls.set, [['sourceDirExclude', ['**/test/**', '*.min.js']]])
+})
+
+test('a boolean field writes a real boolean', async () => {
+  const { draw, react } = registered()
+  const scope = fakeScope(READY)
+  const checkbox = findAll(
+    draw(scope),
+    (node) => node.type === 'input' && node.props['aria-label'] === 'Install slopo with uv when missing',
+  )[0]
+  checkbox.props.onChange({ target: { checked: true } })
+  react.reset()
+  await buttonStartingWith(draw(scope), 'Save').props.onClick()
+  assert.deepEqual(scope.calls.set, [['autoInstall', true]])
+})
+
+test('an overridden field is marked, and Reset clears every override', async () => {
+  const { draw } = registered()
+  const scope = fakeScope({
+    ...READY,
+    value: { embeddingModel: 'ollama/x:latest', embeddingDimensions: 768 },
+    user: { embeddingModel: 'ollama/x:latest', embeddingDimensions: 768 },
+  })
+  const tree = draw(scope)
+  const labels = findAll(tree, (node) => node.type === 'label').map(textOf)
+  assert.ok(labels.some((label) => label.includes('overridden')), 'a user-set field must be marked')
+
+  const reset = buttonStartingWith(tree, 'Reset')
+  assert.equal(reset.props.disabled, false)
+  await reset.props.onClick()
+  assert.deepEqual(scope.calls.unset.sort(), ['embeddingDimensions', 'embeddingModel'])
+})
+
+test('a read-only namespace disables every control', () => {
+  const { draw } = registered()
+  const tree = draw(fakeScope({ ...READY, writable: false, mode: 'memory' }))
+  const inputs = findAll(tree, (node) => node.type === 'input')
+  assert.ok(inputs.length > 0)
+  for (const input of inputs) assert.equal(input.props.disabled, true)
+})
diff --git a/test/plugin.test.js b/test/plugin.test.js
index 1fd7949..6f2bfdc 100644
--- a/test/plugin.test.js
+++ b/test/plugin.test.js
@@ -422,10 +422,13 @@ test('a workspace-write session with stateDir inside the workspace proceeds', as
   assert.deepEqual(state.shellRequests[0].sandboxPolicy, { mode: 'workspace-write', workspaceRoot: workspace })
 })
 
-test('configure and status never touch the shell, so they work under any sandbox', async () => {
+test('configure never touches the shell, and status only runs a read-only version check', async () => {
   const { state } = harness({}, { sandboxMode: 'workspace-write' })
   const tool = state.tools.get('slopo')
-  await tool.execute({ action: 'status' }, execContext('/some/workspace'))
   await tool.execute({ action: 'configure', config: { embeddingModel: 'x' } }, execContext('/some/workspace'))
-  assert.deepEqual(state.shellRequests, [])
+  assert.deepEqual(state.shellRequests, [], 'configure must not execute anything')
+  await tool.execute({ action: 'status' }, execContext('/some/workspace'))
+  for (const request of state.shellRequests) {
+    assert.match(request.command, /--version/, 'status may only run a read-only version check')
+  }
 })
diff --git a/test/probe.test.js b/test/probe.test.js
new file mode 100644
index 0000000..13a9577
--- /dev/null
+++ b/test/probe.test.js
@@ -0,0 +1,137 @@
+import assert from 'node:assert/strict'
+import { test } from 'node:test'
+
+import { bareModelName, embeddingUrl, probeEmbeddingEndpoint } from '../lib/probe.js'
+
+/** A fetch stand-in returning one canned response. */
+function fakeFetch({ ok = true, status = 200, body = {}, throws, onCall } = {}) {
+  return async (url, options) => {
+    if (onCall !== undefined) onCall(url, options)
+    if (throws !== undefined) throw throws
+    return {
+      ok,
+      status,
+      async text() {
+        return typeof body === 'string' ? body : JSON.stringify(body)
+      },
+    }
+  }
+}
+
+test('bareModelName strips a known provider prefix', () => {
+  assert.equal(bareModelName('ollama/unclemusclez/jina-embeddings-v2-base-code:latest'), 'unclemusclez/jina-embeddings-v2-base-code:latest')
+  assert.equal(bareModelName('openai/text-embedding-3-small'), 'text-embedding-3-small')
+  assert.equal(bareModelName('hosted_vllm/meta-llama/Llama-3-8B'), 'meta-llama/Llama-3-8B')
+})
+
+test('bareModelName leaves a model that merely contains a slash alone', () => {
+  // An unknown first segment is far more likely to be part of the model name
+  // than a provider prefix, and mangling it would make the probe lie.
+  assert.equal(bareModelName('unclemusclez/jina-embeddings-v2-base-code:latest'), 'unclemusclez/jina-embeddings-v2-base-code:latest')
+  assert.equal(bareModelName('text-embedding-3-small'), 'text-embedding-3-small')
+})
+
+test('embeddingUrl tolerates a base that already carries the version segment', () => {
+  assert.equal(embeddingUrl('http://host:11434'), 'http://host:11434/v1/embeddings')
+  assert.equal(embeddingUrl('http://host:11434/'), 'http://host:11434/v1/embeddings')
+  assert.equal(embeddingUrl('http://host:11434/v1'), 'http://host:11434/v1/embeddings')
+  assert.equal(embeddingUrl('  http://host:11434/v2/  '), 'http://host:11434/v2/embeddings')
+  assert.equal(embeddingUrl(''), '')
+})
+
+test('probeEmbeddingEndpoint reports a matching dimension as ok', async () => {
+  let seen
+  const result = await probeEmbeddingEndpoint({
+    apiBase: 'http://host:11434',
+    model: 'ollama/unclemusclez/jina:latest',
+    dimensions: 768,
+    fetchImpl: fakeFetch({
+      body: { data: [{ embedding: new Array(768).fill(0.1) }] },
+      onCall: (url, options) => {
+        seen = { url, options }
+      },
+    }),
+  })
+  assert.equal(result.ok, true)
+  assert.equal(result.dimensions, 768)
+  assert.equal(result.expected, 768)
+  assert.equal(result.url, 'http://host:11434/v1/embeddings')
+  // The prefix is LiteLLM's; the endpoint must receive the bare model name.
+  assert.equal(JSON.parse(seen.options.body).model, 'unclemusclez/jina:latest')
+})
+
+test('probeEmbeddingEndpoint catches a dimension mismatch, which is what slopo freezes', async () => {
+  const result = await probeEmbeddingEndpoint({
+    apiBase: 'http://host:11434',
+    model: 'ollama/m:latest',
+    dimensions: 1024,
+    fetchImpl: fakeFetch({ body: { data: [{ embedding: new Array(768).fill(0) }] } }),
+  })
+  assert.equal(result.ok, false)
+  assert.equal(result.dimensions, 768)
+  assert.equal(result.expected, 1024)
+  assert.match(result.error, /returns 768 dimensions but embeddingDimensions is 1024/)
+})
+
+test('probeEmbeddingEndpoint reports an HTTP error instead of throwing', async () => {
+  const result = await probeEmbeddingEndpoint({
+    apiBase: 'http://host:11434',
+    model: 'ollama/m:latest',
+    dimensions: 768,
+    fetchImpl: fakeFetch({ ok: false, status: 404, body: 'model not found' }),
+  })
+  assert.equal(result.ok, false)
+  assert.equal(result.status, 404)
+  assert.match(result.error, /model not found/)
+})
+
+test('probeEmbeddingEndpoint reports an unreachable endpoint instead of throwing', async () => {
+  const result = await probeEmbeddingEndpoint({
+    apiBase: 'http://host:11434',
+    model: 'ollama/m:latest',
+    dimensions: 768,
+    fetchImpl: fakeFetch({ throws: new Error('connect ECONNREFUSED') }),
+  })
+  assert.equal(result.ok, false)
+  assert.equal(result.reachable, false)
+  assert.match(result.error, /ECONNREFUSED/)
+})
+
+test('probeEmbeddingEndpoint reports a timeout as a timeout', async () => {
+  const abort = new Error('aborted')
+  abort.name = 'AbortError'
+  const result = await probeEmbeddingEndpoint({
+    apiBase: 'http://host:11434',
+    model: 'm',
+    dimensions: 768,
+    timeoutMs: 25,
+    fetchImpl: fakeFetch({ throws: abort }),
+  })
+  assert.equal(result.ok, false)
+  assert.match(result.error, /no response within 25ms/)
+})
+
+test('probeEmbeddingEndpoint skips cleanly with nothing to probe', async () => {
+  const result = await probeEmbeddingEndpoint({ apiBase: '', model: 'm', dimensions: 768 })
+  assert.equal(result.checked, false)
+  assert.match(result.skipped, /no embeddingApiBase/)
+})
+
+test('probeEmbeddingEndpoint sends the key as a bearer token only when there is one', async () => {
+  const seen = []
+  const call = (apiKey) =>
+    probeEmbeddingEndpoint({
+      apiBase: 'http://host',
+      model: 'm',
+      dimensions: 1,
+      apiKey,
+      fetchImpl: fakeFetch({
+        body: { data: [{ embedding: [1] }] },
+        onCall: (_url, options) => seen.push(options.headers),
+      }),
+    })
+  await call('secret-key')
+  await call('')
+  assert.equal(seen[0].authorization, 'Bearer secret-key')
+  assert.equal(Object.hasOwn(seen[1], 'authorization'), false)
+})