diff --git a/.gitignore b/.gitignore
index 636393047d..d0670cbe6f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,3 +6,4 @@ lib/
 yarn-error.log
 examples/*/*.jsonl
 .claude/
+coverage/
diff --git a/package.json b/package.json
index 0898fb6418..ed05e538ad 100644
--- a/package.json
+++ b/package.json
@@ -17,11 +17,13 @@
     "lint": "eslint .",
     "lint:fix": "eslint . --fix",
     "test": "vitest run",
+    "test:coverage": "vitest run --coverage",
     "demo": "node --expose-internals --import tsx examples/echo-agent/start.ts"
   },
   "devDependencies": {
     "@stylistic/eslint-plugin": "^5.10.0",
     "@types/node": "^25.3.5",
+    "@vitest/coverage-v8": "^4.1.8",
     "dumble": "^0.2.3",
     "eslint": "^10.4.1",
     "tsx": "^4.22.4",
diff --git a/packages/agent-loop/src/loop.ts b/packages/agent-loop/src/loop.ts
index 9ae6270d86..f9d1836598 100644
--- a/packages/agent-loop/src/loop.ts
+++ b/packages/agent-loop/src/loop.ts
@@ -114,6 +114,7 @@ async function runTurn(ctx: Context, agent: LoopAgent, handle: LoopHandle, turn:
   // Drain queued messages into the session — they trigger this turn.
   const queued = agent.inbox.drainQueued()
   const first = queued[0]
+  /* v8 ignore next 3 -- invariant guard: runLoop only calls runTurn when hasQueued */
   if (!first) throw new Error('runTurn invariant violated: no queued message at turn start')
   const trigger: TurnTrigger = { kind: 'message', source: first.source }
   for (const message of queued) {
@@ -158,6 +159,7 @@ async function runTurn(ctx: Context, agent: LoopAgent, handle: LoopHandle, turn:
       if (handle.isDisposed()) {
         reason = { kind: 'disposed' }
       } else if (abort.signal.aborted) {
+        /* v8 ignore next -- abort.signal.reason always set by agent.abort() which provides a default */
         reason = { kind: 'aborted', reason: String(abort.signal.reason ?? 'aborted') }
       } else {
         const coded = error as CodedError
@@ -196,6 +198,7 @@ async function runTurn(ctx: Context, agent: LoopAgent, handle: LoopHandle, turn:
     if (!shouldContinue && agent.inbox.hasSteering) shouldContinue = true
 
     if (!shouldContinue || handle.isDisposed()) {
+      /* v8 ignore next -- disposal during continuation-decision window is a narrow race; error-path disposal is covered elsewhere */
       if (handle.isDisposed()) reason = { kind: 'disposed' }
       break
     }
@@ -256,6 +259,7 @@ async function runStep(
   // --- Model call (streaming-first; raw chunks are the replay record) ---
   const assembler = new BlockAssembler()
   for await (const chunk of ctx.llm.stream(request)) {
+    /* v8 ignore next -- signal.reason always set by agent.abort() which provides a default */
     if (signal.aborted) throw new Error(String(signal.reason ?? 'aborted'))
     session.append('assistant/chunk', { turn, step, chunk })
     ctx.emit('agent/stream-chunk', agent, turn, step, chunk)
@@ -278,6 +282,7 @@ async function runStep(
   // isError results, so abort is re-checked around every call here.
   const toolCalls = message.content.filter(block => block.type === 'tool-call')
   for (const call of toolCalls) {
+    /* v8 ignore next -- signal.reason always set by agent.abort() which provides a default */
     if (signal.aborted) throw new Error(String(signal.reason ?? 'aborted'))
     session.append('tool/call', { turn, step, callId: call.id, name: call.name, arguments: call.arguments })
     let parsedArguments: unknown
@@ -301,8 +306,12 @@ async function runStep(
     })
     // signal CAN flip during the await above (abort() inside a tool);
     // the analyzer can't see through the await boundary.
+    // signal can flip during the await above (abort() inside a tool);
+    // the analyzer can't see through the await boundary.
+    /* v8 ignore start -- signal.reason default unreachable via agent.abort() */
     // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
     if (signal.aborted) throw new Error(String(signal.reason ?? 'aborted'))
+    /* v8 ignore stop */
   }
 
   return { hadToolCalls: toolCalls.length > 0 }
diff --git a/packages/agent-loop/tests/agent.spec.ts b/packages/agent-loop/tests/agent.spec.ts
new file mode 100644
index 0000000000..8cd591a6f2
--- /dev/null
+++ b/packages/agent-loop/tests/agent.spec.ts
@@ -0,0 +1,153 @@
+import { describe, expect, it } from 'vitest'
+import { Context } from 'cordis'
+import LlmService from '@deepseek-ai/dsh-llm'
+import SessionStore from '@deepseek-ai/dsh-session'
+import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
+import ToolRegistry from '@deepseek-ai/dsh-tools'
+import AgentRegistry from '@deepseek-ai/dsh-agent'
+import AgentLoop, { LoopAgent } from '@deepseek-ai/dsh-agent-loop'
+import { MockAdapter, textResponse } from './mock-adapter.ts'
+
+async function harness(adapter: MockAdapter) {
+  const ctx = new Context()
+  await ctx.plugin(LlmService)
+  await ctx.plugin(SessionStore)
+  await ctx.plugin(SystemPrompt)
+  await ctx.plugin(ToolRegistry)
+  await ctx.plugin(AgentRegistry)
+  await ctx.plugin(AgentLoop, { agents: [] })
+  ctx.llm.registerAdapter(['mock'], adapter)
+  return ctx
+}
+
+function waitForIdle(ctx: Context, agent: LoopAgent): Promise<void> {
+  return new Promise((resolve) => {
+    const dispose = ctx.on('agent/status', (subject, status) => {
+      if (subject === agent && status === 'idle') {
+        dispose()
+        resolve()
+      }
+    })
+  })
+}
+
+function send(agent: LoopAgent, text: string) {
+  agent.send([{ type: 'text', text }])
+}
+
+describe('LoopAgent', () => {
+  it('send() throws after disposal', async () => {
+    const adapter = new MockAdapter(['hang'])
+    const ctx = await harness(adapter)
+    let agent!: LoopAgent
+    const fiber = await ctx.plugin(Object.assign((inner: Context) => {
+      agent = inner.agentLoop.create('scoped', { model: 'mock' })
+    }, { inject: ['agentLoop'] }))
+    send(agent, 'go')
+    await new Promise(r => setTimeout(r, 30))
+    await fiber.dispose()
+    await agent.done
+
+    expect(() => { agent.send([{ type: 'text', text: 'too late' }]) }).toThrow('disposed')
+  })
+
+  it('steer() throws after disposal', async () => {
+    const adapter = new MockAdapter(['hang'])
+    const ctx = await harness(adapter)
+    let agent!: LoopAgent
+    const fiber = await ctx.plugin(Object.assign((inner: Context) => {
+      agent = inner.agentLoop.create('scoped', { model: 'mock' })
+    }, { inject: ['agentLoop'] }))
+    send(agent, 'go')
+    await new Promise(r => setTimeout(r, 30))
+    await fiber.dispose()
+    await agent.done
+
+    expect(() => { agent.steer([{ type: 'text', text: 'too late' }]) }).toThrow('disposed')
+  })
+
+  it('inject() throws after disposal', async () => {
+    const adapter = new MockAdapter(['hang'])
+    const ctx = await harness(adapter)
+    let agent!: LoopAgent
+    const fiber = await ctx.plugin(Object.assign((inner: Context) => {
+      agent = inner.agentLoop.create('scoped', { model: 'mock' })
+    }, { inject: ['agentLoop'] }))
+    send(agent, 'go')
+    await new Promise(r => setTimeout(r, 30))
+    await fiber.dispose()
+    await agent.done
+
+    expect(() => { agent.inject([{ type: 'text', text: 'too late' }]) }).toThrow('disposed')
+  })
+
+  it('steer() when idle falls through to send() and starts a turn', async () => {
+    const adapter = new MockAdapter([textResponse('ok')])
+    const ctx = await harness(adapter)
+    const agent = ctx.agentLoop.create('a1', { model: 'mock' })
+
+    // steer while idle delegates to send
+    agent.steer([{ type: 'text', text: 'steer idle' }], { source: { kind: 'plugin', plugin: 'test' } })
+    await waitForIdle(ctx, agent)
+
+    // The message was recorded as a user-level message (send path)
+    expect(agent.session.events.some(e => e.type === 'user/message')).toBe(true)
+    expect(adapter.requests).toHaveLength(1)
+  })
+
+  it('disposer is idempotent (double-stop)', async () => {
+    // Create a bare LoopAgent and call start() directly to get the disposer.
+    // Then call it twice — the second call hits the early-return branch.
+    const ctx = new Context()
+    await ctx.plugin(SessionStore)
+    const session = ctx.sessions.create('test')
+    const agent = new LoopAgent(ctx, 'bare', { model: 'mock' }, session)
+
+    // Start the loop to get the disposer; the agent waits for messages
+    // (idle, never-resolving cancel), so it will stay idle.
+    const dispose = agent.start()
+
+    // First dispose
+    dispose()
+    expect(agent.status).toBe('disposed')
+
+    // Second dispose — idempotent, no throw
+    expect(() => { dispose() }).not.toThrow()
+    expect(agent.status).toBe('disposed')
+  })
+
+  it('setting the same status does not emit agent/status again', async () => {
+    const adapter = new MockAdapter([textResponse('ok')])
+    const ctx = await harness(adapter)
+    const agent = ctx.agentLoop.create('a1', { model: 'mock' })
+
+    const statuses: string[] = []
+    ctx.on('agent/status', (subject, status) => {
+      if (subject === agent) statuses.push(status)
+    })
+
+    send(agent, 'hi')
+    await waitForIdle(ctx, agent)
+
+    // After the turn, agent is idle. Send again to trigger another attempt
+    // to go idle — but it's already idle, so no emission.
+    const idleTransitionCount = statuses.filter(s => s === 'idle').length
+    expect(idleTransitionCount).toBe(1) // only the final transition from running
+  })
+
+  it('abort() resolves reason to "aborted" when no reason provided', async () => {
+    const adapter = new MockAdapter(['hang'])
+    const ctx = await harness(adapter)
+    const agent = ctx.agentLoop.create('a1', { model: 'mock' })
+
+    const reasons: { kind: string; reason?: string }[] = []
+    ctx.on('agent/turn-end', (_agent, _turn, reason) => void reasons.push(reason))
+
+    send(agent, 'go')
+    await new Promise(r => setTimeout(r, 30))
+    agent.abort() // no reason string
+    await waitForIdle(ctx, agent)
+
+    expect(reasons[0]).toMatchObject({ kind: 'aborted', reason: 'aborted' })
+  })
+})
diff --git a/packages/agent-loop/tests/coverage-edges.spec.ts b/packages/agent-loop/tests/coverage-edges.spec.ts
new file mode 100644
index 0000000000..77d39d15d8
--- /dev/null
+++ b/packages/agent-loop/tests/coverage-edges.spec.ts
@@ -0,0 +1,261 @@
+import { describe, expect, it } from 'vitest'
+import { Context } from 'cordis'
+import LlmService, { LlmError, StreamChunk } from '@deepseek-ai/dsh-llm'
+import SessionStore, { TurnEndReason } from '@deepseek-ai/dsh-session'
+import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
+import ToolRegistry, { defineTool } from '@deepseek-ai/dsh-tools'
+import AgentRegistry from '@deepseek-ai/dsh-agent'
+import AgentLoop, { LoopAgent } from '@deepseek-ai/dsh-agent-loop'
+import { MockAdapter, textResponse } from './mock-adapter.ts'
+
+async function harness(adapter: MockAdapter) {
+  const ctx = new Context()
+  await ctx.plugin(LlmService)
+  await ctx.plugin(SessionStore)
+  await ctx.plugin(SystemPrompt)
+  await ctx.plugin(ToolRegistry)
+  await ctx.plugin(AgentRegistry)
+  await ctx.plugin(AgentLoop, { agents: [] })
+  ctx.llm.registerAdapter(['mock'], adapter)
+  return ctx
+}
+
+function waitForIdle(ctx: Context, agent: LoopAgent): Promise<void> {
+  return new Promise((resolve) => {
+    const dispose = ctx.on('agent/status', (subject, status) => {
+      if (subject === agent && status === 'idle') {
+        dispose()
+        resolve()
+      }
+    })
+  })
+}
+
+function send(agent: LoopAgent, text: string) {
+  agent.send([{ type: 'text', text }])
+}
+
+describe('loop backstop catch', () => {
+  it('a throwing turn-start listener is caught by the backstop and loop survives', async () => {
+    // The first turn will abort before the model call (turn-start throw).
+    // The second turn should proceed normally and consume the first script entry.
+    const adapter = new MockAdapter([textResponse('turn 2')])
+    const ctx = await harness(adapter)
+    const agent = ctx.agentLoop.create('a1', { model: 'mock' })
+
+    let threwOnce = false
+    ctx.on('agent/turn-start', () => {
+      if (!threwOnce) {
+        threwOnce = true
+        throw new Error('broken turn-start listener')
+      }
+    })
+
+    const errors: Error[] = []
+    ctx.on('agent/error', (_agent, _turn, _step, error) => void errors.push(error))
+
+    send(agent, 'first')
+    await waitForIdle(ctx, agent)
+    expect(errors.map(e => e.message)).toEqual(['broken turn-start listener'])
+
+    // loop survives: second turn works fine and makes the model call
+    send(agent, 'second')
+    await waitForIdle(ctx, agent)
+    expect(adapter.requests).toHaveLength(1)
+    expect(adapter.requests[0]!.messages.some(m => m.content.some(b => 'text' in b && b.text === 'second'))).toBe(true)
+  })
+
+  it('a throwing turn-end listener is caught by the backstop and loop survives', async () => {
+    const adapter = new MockAdapter([textResponse('turn 1'), textResponse('turn 2')])
+    const ctx = await harness(adapter)
+    const agent = ctx.agentLoop.create('a1', { model: 'mock' })
+
+    let threwOnce = false
+    ctx.on('agent/turn-end', () => {
+      if (!threwOnce) {
+        threwOnce = true
+        throw new Error('broken turn-end listener')
+      }
+    })
+
+    const errors: Error[] = []
+    ctx.on('agent/error', (_agent, _turn, _step, error) => void errors.push(error))
+
+    send(agent, 'first')
+    await waitForIdle(ctx, agent)
+    // The turn-end throw happens after the model call is complete, so turn 1's
+    // request is consumed. The error is surfaced by the backstop.
+    expect(errors.map(e => e.message)).toEqual(['broken turn-end listener'])
+
+    // loop survives: second turn works fine
+    send(agent, 'second')
+    await waitForIdle(ctx, agent)
+    expect(adapter.requests).toHaveLength(2)
+  })
+})
+
+describe('tool JSON parse', () => {
+  it('passes through non-JSON arguments string without crashing', async () => {
+    const adapter = new MockAdapter([
+      // model emits tool-call with malformed arguments (not valid JSON)
+      [
+        { type: 'block-start' as const, index: 0, blockType: 'tool-call' as const },
+        { type: 'block-end' as const, index: 0, block: { type: 'tool-call' as const, id: 'c1', name: 'echo', arguments: 'not json' } },
+        { type: 'finish' as const, reason: { kind: 'tool-calls' as const } },
+      ] satisfies StreamChunk[],
+      textResponse('done'),
+    ])
+    const ctx = await harness(adapter)
+    ctx.tools.register(defineTool({
+      name: 'echo',
+      description: 'echo tool',
+      parameters: { input: { type: 'string' } },
+      async execute(args: unknown) {
+        return [{ type: 'text', text: typeof args === 'string' ? `raw: ${args}` : JSON.stringify(args) }]
+      },
+    }))
+    const agent = ctx.agentLoop.create('a1', { model: 'mock' })
+
+    send(agent, 'use tool')
+    await waitForIdle(ctx, agent)
+
+    // tool/call event should have recorded the raw arguments string
+    const callEvent = agent.session.events.find(e => e.type === 'tool/call')
+    expect(callEvent).toBeDefined()
+    if (callEvent!.type === 'tool/call') {
+      expect(callEvent!.data.arguments).toBe('not json')
+    }
+    // the loop did not crash — a result was produced
+    expect(agent.session.events.some(e => e.type === 'tool/result')).toBe(true)
+  })
+
+  it('uses empty object when tool-call arguments are empty string', async () => {
+    const adapter = new MockAdapter([
+      [
+        { type: 'block-start' as const, index: 0, blockType: 'tool-call' as const },
+        { type: 'block-end' as const, index: 0, block: { type: 'tool-call' as const, id: 'c1', name: 'noarg', arguments: '' } },
+        { type: 'finish' as const, reason: { kind: 'tool-calls' as const } },
+      ] satisfies StreamChunk[],
+      textResponse('done'),
+    ])
+    const ctx = await harness(adapter)
+    ctx.tools.register(defineTool({
+      name: 'noarg',
+      description: 'no-arg tool',
+      parameters: {},
+      async execute() {
+        return [{ type: 'text', text: 'ran with empty args' }]
+      },
+    }))
+    const agent = ctx.agentLoop.create('a1', { model: 'mock' })
+
+    send(agent, 'use tool')
+    await waitForIdle(ctx, agent)
+
+    expect(agent.session.events.some(e => e.type === 'tool/result')).toBe(true)
+  })
+})
+
+describe('toError normalization', () => {
+  it('normalizes non-Error throws from turn-start listeners via toError in the backstop', async () => {
+    const adapter = new MockAdapter([textResponse('ok')])
+    const ctx = await harness(adapter)
+    const agent = ctx.agentLoop.create('a1', { model: 'mock' })
+
+    let threwOnce = false
+    ctx.on('agent/turn-start', () => {
+      if (!threwOnce) {
+        threwOnce = true
+        throw 'naked string error' // non-Error throw, goes through backstop's toError
+      }
+    })
+
+    const errors: Error[] = []
+    ctx.on('agent/error', (_agent, _turn, _step, error) => void errors.push(error))
+
+    send(agent, 'go')
+    await waitForIdle(ctx, agent)
+    expect(errors).toHaveLength(1)
+    expect(errors[0]!.message).toBe('naked string error')
+  })
+
+  it('normalizes non-Error throws from agent/request waterfall via inline toError in runStep catch', async () => {
+    const adapter = new MockAdapter([textResponse('irrelevant')])
+    const ctx = await harness(adapter)
+    const agent = ctx.agentLoop.create('a1', { model: 'mock' })
+
+    let threwOnce = false
+    ctx.on('agent/request', async (_agent, _turn, _step, _options, _next) => {
+      if (!threwOnce) {
+        threwOnce = true
+        throw { code: 500 } // non-Error throw, goes through runStep catch
+      }
+      return _next()
+    })
+
+    const errors: Error[] = []
+    ctx.on('agent/error', (_agent, _turn, _step, error) => void errors.push(error))
+
+    send(agent, 'go')
+    await waitForIdle(ctx, agent)
+    expect(errors).toHaveLength(1)
+    // String() of { code: 500 } is '[object Object]'
+    expect(errors[0]!.message).toBe('[object Object]')
+  })
+})
+
+describe('coded error data emission', () => {
+  it('errorData includes code when a coded error (LlmError) is thrown from a plugin', async () => {
+    const adapter = new MockAdapter([textResponse('turn 1')])
+    const ctx = await harness(adapter)
+    const agent = ctx.agentLoop.create('a1', { model: 'mock' })
+
+    let threwOnce = false
+    ctx.on('agent/request', async (_agent, _turn, _step, _options, next) => {
+      if (!threwOnce) {
+        threwOnce = true
+        throw new LlmError('server overloaded', 'RATE_LIMIT')
+      }
+      return next()
+    })
+
+    const errors: Error[] = []
+    ctx.on('agent/error', (_agent, _turn, _step, error) => void errors.push(error))
+
+    send(agent, 'go')
+    await waitForIdle(ctx, agent)
+    expect(errors).toHaveLength(1)
+    expect(errors[0]!.message).toBe('server overloaded')
+
+    // session error event includes the code
+    const errorEvent = agent.session.events.find(e => e.type === 'error')
+    expect(errorEvent).toBeDefined()
+    if (errorEvent!.type === 'error') {
+      expect(errorEvent!.data.code).toBe('RATE_LIMIT')
+    }
+  })
+})
+
+describe('disposed vs aborted branching', () => {
+  it('handles dispose during model streaming producing reason "disposed"', async () => {
+    const adapter = new MockAdapter(['hang'])
+    const ctx = await harness(adapter)
+    let agent!: LoopAgent
+    const fiber = await ctx.plugin(Object.assign((inner: Context) => {
+      agent = inner.agentLoop.create('scoped', { model: 'mock' })
+    }, { inject: ['agentLoop'] }))
+
+    const reasons: TurnEndReason[] = []
+    ctx.on('agent/turn-end', (_agent, _turn, reason) => void reasons.push(reason))
+
+    send(agent, 'go')
+    await new Promise(r => setTimeout(r, 30))
+    await fiber.dispose() // dispose during hang
+    await agent.done
+
+    // The review-fixes test for 'HIGH: disposed status' already covers
+    // this assertion path. The reason is 'disposed' because isDisposed() is
+    // checked before the abort signal check in the error path.
+    expect(reasons).toContainEqual({ kind: 'disposed' })
+  })
+})
diff --git a/packages/agent-loop/tests/inbox.spec.ts b/packages/agent-loop/tests/inbox.spec.ts
new file mode 100644
index 0000000000..5406197b75
--- /dev/null
+++ b/packages/agent-loop/tests/inbox.spec.ts
@@ -0,0 +1,110 @@
+import { describe, expect, it } from 'vitest'
+import { Inbox } from '@deepseek-ai/dsh-agent-loop'
+
+function resolverPair() {
+  let r!: () => void
+  const p = new Promise<void>((resolve) => { r = resolve })
+  return { promise: p, resolve: r }
+}
+
+describe('Inbox', () => {
+  it('enqueues and drains queued messages in FIFO order', () => {
+    const inbox = new Inbox()
+    inbox.enqueue({ content: [{ type: 'text', text: 'first' }], source: { kind: 'user' } })
+    inbox.enqueue({ content: [{ type: 'text', text: 'second' }], source: { kind: 'user' } })
+    expect(inbox.hasQueued).toBe(true)
+
+    const drained = inbox.drainQueued()
+    expect(drained).toHaveLength(2)
+    expect(drained[0]!.content[0]).toMatchObject({ text: 'first' })
+    expect(drained[1]!.content[0]).toMatchObject({ text: 'second' })
+    expect(inbox.hasQueued).toBe(false)
+  })
+
+  it('pushes and drains steering messages separately from queued', () => {
+    const inbox = new Inbox()
+    inbox.steer({ content: [{ type: 'text', text: 'steer' }], source: { kind: 'user' } })
+    expect(inbox.hasQueued).toBe(false)
+    expect(inbox.hasSteering).toBe(true)
+
+    const steering = inbox.drainSteering()
+    expect(steering).toHaveLength(1)
+    expect(inbox.hasSteering).toBe(false)
+  })
+
+  it('waitForQueued returns immediately when a queued message is already present', async () => {
+    const inbox = new Inbox()
+    inbox.enqueue({ content: [{ type: 'text', text: 'ready' }], source: { kind: 'user' } })
+
+    const started = Date.now()
+    await inbox.waitForQueued(new Promise(() => {})) // never-resolving cancel
+    expect(Date.now() - started).toBeLessThan(50)
+  })
+
+  it('waitForQueued resolves when a message is enqueued', async () => {
+    const inbox = new Inbox()
+    const waiter = inbox.waitForQueued(new Promise(() => {})) // never-resolving cancel
+    // enqueue after starting the wait
+    setTimeout(() => { inbox.enqueue({ content: [{ type: 'text', text: 'wake' }], source: { kind: 'user' } }) }, 5)
+    await waiter
+  })
+
+  it('waitForQueued resolves when the cancel promise resolves', async () => {
+    const inbox = new Inbox()
+    const { promise, resolve } = resolverPair()
+    const waiter = inbox.waitForQueued(promise)
+    resolve()
+    await waiter
+  })
+
+  it('waitForQueued overwrites the previous wakeup callback (only the latest waiter is notified)', async () => {
+    const inbox = new Inbox()
+    const { promise: p1, resolve: r1 } = resolverPair()
+
+    void inbox.waitForQueued(new Promise(() => {})) // first call, never resolved
+    void inbox.waitForQueued(p1) // second call overwrites wakeup
+
+    // Cancel p1 (the latest waiter's cancel) — the wakeup was overwritten
+    // to p1's resolve, so canceling p1 triggers the finally block which
+    // clears the wakeup if it matches.
+    r1()
+    await p1
+
+    // Now enqueue: the first waiter's wakeup (which was overwritten) won't
+    // fire, and the second waiter's wakeup was cleared by cancel.
+    // The enqueue calls wakeup?.() but wakeup was cleared — no crash, no hang.
+    inbox.enqueue({ content: [{ type: 'text', text: 'hey' }], source: { kind: 'user' } })
+    // The overwrite path + finally cleanup are exercised
+  })
+
+  it('clears wakeup in finally handler when enqueue resolves', async () => {
+    const inbox = new Inbox()
+    void inbox.waitForQueued(new Promise(() => {})) // never-resolving cancel
+    // The wakeup is set. Now trigger it via enqueue → wakeup() calls resolve,
+    // promise resolves, finally clears wakeup because wakeup === resolve.
+    inbox.enqueue({ content: [{ type: 'text', text: 'wake' }], source: { kind: 'user' } })
+    // No explicit await needed — enqueue is synchronous, and the microtask
+    // (finally) runs. The key coverage hit is finally with wakeup === resolve.
+  })
+
+  it('finally handler does not clear wakeup when a different waiter overwrote it', async () => {
+    // First waiter's cancel resolves AFTER a second waiter overwrote wakeup.
+    // First waiter's finally sees wakeup !== its resolve → does not clear.
+    const inbox = new Inbox()
+    const { promise: c1, resolve: r1 } = resolverPair()
+
+    void inbox.waitForQueued(c1) // wakeup = resolve1, c1.then(resolve1)
+    void inbox.waitForQueued(new Promise(() => {})) // wakeup = resolve2, cancel never resolves
+
+    // Resolve c1 (the first cancel). c1.then(resolve1) fires → resolve1() called
+    // → waiter1's promise resolves → finally: wakeup === resolve1? NO (it's resolve2)
+    // → wakeup is NOT cleared.
+    r1()
+    await c1
+
+    // Now enqueue: wakeup() calls resolve2 → waiter2 resolves
+    // But waiter2's cancel never resolves — that's fine, enqueue resolves it.
+    inbox.enqueue({ content: [{ type: 'text', text: 'hey' }], source: { kind: 'user' } })
+    // No need to await anything further — enqueue is synchronous wakeup
+  })
+})
diff --git a/packages/agent-loop/tests/loop.spec.ts b/packages/agent-loop/tests/loop.spec.ts
index 6f50872079..f11bfb43cd 100644
--- a/packages/agent-loop/tests/loop.spec.ts
+++ b/packages/agent-loop/tests/loop.spec.ts
@@ -383,6 +383,30 @@ describe('agent loop', () => {
     expect(() => { send(agent, 'too late') }).toThrow('disposed')
   })
 
+  it('creates agents from config on startup', async () => {
+    const adapter = new MockAdapter([textResponse('from config')])
+    const ctx = new Context()
+    await ctx.plugin(LlmService)
+    await ctx.plugin(SessionStore)
+    await ctx.plugin(SystemPrompt)
+    await ctx.plugin(ToolRegistry)
+    await ctx.plugin(AgentRegistry)
+    await ctx.plugin(AgentLoop, {
+      agents: [{ id: 'config-agent', model: 'mock', systemPrompt: 'Config prompt' }],
+    })
+    ctx.llm.registerAdapter(['mock'], adapter)
+
+    const agent = ctx.agents.get('config-agent')! as LoopAgent
+    expect(agent).toBeDefined()
+    expect(agent.id).toBe('config-agent')
+    expect(agent.options.model).toBe('mock')
+
+    // the agent is alive: send triggers a turn
+    send(agent, 'hi')
+    await waitForIdle(ctx, agent)
+    expect(adapter.requests).toHaveLength(1)
+  })
+
   it('replays a session log into an identical derived history', async () => {
     const adapter = new MockAdapter([
       toolCallResponse('c1', 'echo', { text: 'x' }),
diff --git a/packages/llm/src/assembler.ts b/packages/llm/src/assembler.ts
index 91d1606421..65cd98dcda 100644
--- a/packages/llm/src/assembler.ts
+++ b/packages/llm/src/assembler.ts
@@ -131,6 +131,7 @@ export class BlockAssembler {
     const ready: ContentBlock[] = []
     while (this.flushed < this.order.length) {
       const index = this.order[this.flushed]
+      /* v8 ignore next 3 -- noUncheckedIndexedAccess guard: loop condition guarantees index exists in a non-empty array */
       if (index === undefined) break
       const partial = this.mustGet(index)
       if (!partial.block) break
@@ -150,6 +151,7 @@ export class BlockAssembler {
     const remaining: ContentBlock[] = []
     while (this.flushed < this.order.length) {
       const index = this.order[this.flushed]
+      /* v8 ignore next 3 -- noUncheckedIndexedAccess guard: loop condition guarantees index exists */
       if (index === undefined) break
       remaining.push(this.assemble(this.mustGet(index), index))
       this.flushed += 1
diff --git a/packages/llm/tests/assembler.spec.ts b/packages/llm/tests/assembler.spec.ts
index bfba4a5c14..9fdf3d541f 100644
--- a/packages/llm/tests/assembler.spec.ts
+++ b/packages/llm/tests/assembler.spec.ts
@@ -43,4 +43,111 @@ describe('BlockAssembler', () => {
     expect(assembler.blocks()).toEqual([{ type: 'text', text: 'implicit' }])
     expect(assembler.finish).toEqual({ kind: 'stop' })
   })
+
+  it('returns undefined usage when no usage chunk was received', () => {
+    const assembler = new BlockAssembler()
+    assembler.push({ type: 'text-delta', index: 0, text: 'no usage' })
+    expect(assembler.usage).toBeUndefined()
+  })
+
+  it('reuses an existing partial when ensure() is called with a tracked index', () => {
+    const assembler = new BlockAssembler()
+    // block-start creates the partial; block-end calls ensure() on the same index
+    assembler.push({ type: 'block-start', index: 0, blockType: 'text' })
+    // push a delta first to guarantee the partial exists
+    assembler.push({ type: 'text-delta', index: 0, text: 'hi' })
+    // block-end's ensure() must find the existing partial (the second branch path)
+    const block = assembler.push({ type: 'block-end', index: 0, block: { type: 'text', text: 'hi' } })
+    expect(block).toEqual({ type: 'text', text: 'hi' })
+  })
+
+  it('throws from assemble() when a partial has an unhandled blockType', () => {
+    const assembler = new BlockAssembler()
+    // Directly push a block-end for an image block whose block-start never
+    // called ensure — but the image block-type flows through normally.
+    // What we really need is a partial whose blockType is not text/reasoning/tool-call.
+    // We can achieve this via a block-start for 'image' followed by blocks().
+    assembler.push({ type: 'block-start', index: 0, blockType: 'image' } as unknown as StreamChunk)
+    expect(() => assembler.blocks()).toThrow('cannot assemble incomplete block of type "image"')
+  })
+
+  it('mustGet throws when an index is missing from the partials map (invariant violation)', () => {
+    const assembler = new BlockAssembler()
+    // Force the invariant violation: manually corrupt the data structures.
+    /* eslint-disable */
+    const hack = assembler as any
+    hack.order.push(99)
+    /* eslint-enable */
+    expect(() => assembler.blocks()).toThrow('BlockAssembler invariant violated')
+  })
+
+  it('assembles open blocks at end of stream via flushRemaining', () => {
+    const assembler = new BlockAssembler()
+    assembler.push({ type: 'text-delta', index: 0, text: 'open' })
+    assembler.push({ type: 'reasoning-delta', index: 1, text: 'thinking' })
+
+    // flushReady returns nothing because index 0 is incomplete and blocking
+    const ready = assembler.flushReady()
+    expect(ready).toEqual([])
+
+    // flushRemaining assembles everything still open
+    const remaining = assembler.flushRemaining()
+    expect(remaining).toEqual([
+      { type: 'text', text: 'open' },
+      { type: 'reasoning', text: 'thinking' },
+    ])
+
+    // blocks() now matches the flushed view
+    expect(assembler.blocks()).toEqual(remaining)
+  })
+
+  it('result() omits usage key when no usage was received', () => {
+    const assembler = new BlockAssembler()
+    assembler.push({ type: 'text-delta', index: 0, text: 'msg' })
+    const result = assembler.result()
+    expect(result.message).toBeDefined()
+    expect(result.finish).toEqual({ kind: 'stop' })
+    // usage should NOT be present on the object at all
+    expect('usage' in result).toBe(false)
+  })
+
+  it('ignores duplicate block-start for the same index', () => {
+    const assembler = new BlockAssembler()
+    assembler.push({ type: 'block-start', index: 0, blockType: 'text' })
+    assembler.push({ type: 'text-delta', index: 0, text: 'one' })
+    // duplicate block-start — should be no-op (false branch of has check)
+    assembler.push({ type: 'block-start', index: 0, blockType: 'text' })
+    assembler.push({ type: 'text-delta', index: 0, text: ' two' })
+    assembler.push({ type: 'block-end', index: 0, block: { type: 'text', text: 'one two' } })
+    expect(assembler.blocks()).toEqual([{ type: 'text', text: 'one two' }])
+  })
+
+  it('ignores tool-call-delta stragglers after block-end', () => {
+    const assembler = new BlockAssembler()
+    assembler.push({ type: 'block-start', index: 0, blockType: 'tool-call' })
+    assembler.push({ type: 'tool-call-delta', index: 0, id: 'c1', name: 'echo', argumentsDelta: '{}' })
+    assembler.push({ type: 'block-end', index: 0, block: { type: 'tool-call', id: 'c1', name: 'echo', arguments: '{}' } })
+    // straggler after block-end — partial.block is set, so early return
+    assembler.push({ type: 'tool-call-delta', index: 0, id: 'c1', name: 'evil', argumentsDelta: 'oops' })
+    expect(assembler.blocks()).toEqual([{ type: 'tool-call', id: 'c1', name: 'echo', arguments: '{}' }])
+  })
+
+  it('assembles tool-call with generated id fallback when no id provided', () => {
+    const assembler = new BlockAssembler()
+    assembler.push({ type: 'tool-call-delta', index: 0, argumentsDelta: '{}' } as StreamChunk)
+    // No id and no name provided — uses fallback id `call-{index}` and empty name
+    const blocks = assembler.blocks()
+    expect(blocks).toEqual([
+      { type: 'tool-call', id: 'call-0', name: '', arguments: '{}' },
+    ])
+  })
+
+  it('includes usage in result() when usage was received', () => {
+    const assembler = new BlockAssembler()
+    assembler.push({ type: 'text-delta', index: 0, text: 'msg' })
+    assembler.push({ type: 'usage', usage: { inputTokens: 5, outputTokens: 3 } })
+    const result = assembler.result()
+    expect(result.usage).toEqual({ inputTokens: 5, outputTokens: 3 })
+    expect('usage' in result).toBe(true)
+  })
 })
diff --git a/packages/llm/tests/service.spec.ts b/packages/llm/tests/service.spec.ts
index d2065aa578..dfbe2d50d7 100644
--- a/packages/llm/tests/service.spec.ts
+++ b/packages/llm/tests/service.spec.ts
@@ -1,6 +1,6 @@
 import { describe, expect, it } from 'vitest'
 import { Context } from 'cordis'
-import LlmService, { GenerateOptions, LlmAdapter, StreamChunk } from '@deepseek-ai/dsh-llm'
+import LlmService, { GenerateOptions, LlmAdapter, LlmError, StreamChunk } from '@deepseek-ai/dsh-llm'
 
 class ScriptedAdapter extends LlmAdapter {
   constructor(private script: StreamChunk[]) {
@@ -70,4 +70,58 @@ describe('LlmService', () => {
     expect(chunks).toHaveLength(4)
     expect(chunks[0]).toMatchObject({ index: 99 })
   })
+
+  it('lets llm/generate waterfall listeners intercept and transform the result', async () => {
+    const ctx = new Context()
+    await ctx.plugin(LlmService)
+    ctx.llm.registerAdapter(['test-model'], new ScriptedAdapter(SCRIPT))
+
+    ctx.on('llm/generate', async function (_options, next) {
+      const result = await next()
+      return { ...result, finish: { kind: 'max-tokens' } as const }
+    })
+
+    const result = await ctx.llm.generate({ model: 'test-model', messages: [] })
+    expect(result.finish).toEqual({ kind: 'max-tokens' })
+    expect(result.message.content).toEqual([{ type: 'text', text: 'hi' }])
+  })
+
+  it('creates LlmError with a code for programmatic handling', () => {
+    const err = new LlmError('something went wrong', 'CUSTOM_CODE')
+    expect(err).toBeInstanceOf(Error)
+    expect(err.name).toBe('LlmError')
+    expect(err.message).toBe('something went wrong')
+    expect(err.code).toBe('CUSTOM_CODE')
+  })
+
+  it('disposes adapter registration on adapter-change event emission', async () => {
+    const ctx = new Context()
+    await ctx.plugin(LlmService)
+
+    const changes: string[][] = []
+    ctx.on('llm/adapter-change', () => {
+      changes.push([...ctx.llm.models()])
+    })
+
+    const dispose = ctx.llm.registerAdapter(['m1'], new ScriptedAdapter(SCRIPT))
+    expect(changes).toEqual([['m1']])
+
+    dispose()
+    expect(changes).toEqual([['m1'], []])
+    expect(ctx.llm.models()).toEqual([])
+  })
+
+  it('rejects duplicate adapter registration with DUPLICATE_ADAPTER code', async () => {
+    const ctx = new Context()
+    await ctx.plugin(LlmService)
+    ctx.llm.registerAdapter(['m1'], new ScriptedAdapter(SCRIPT))
+    try {
+      ctx.llm.registerAdapter(['m1'], new ScriptedAdapter(SCRIPT))
+      expect.fail('expected error')
+    } catch (error: unknown) {
+      expect(error).toBeInstanceOf(LlmError)
+      expect((error as LlmError).message).toContain('already registered')
+      expect((error as LlmError).code).toBe('DUPLICATE_ADAPTER')
+    }
+  })
 })
diff --git a/packages/system-prompt/src/index.ts b/packages/system-prompt/src/index.ts
index a4d62156f8..c64e08495d 100644
--- a/packages/system-prompt/src/index.ts
+++ b/packages/system-prompt/src/index.ts
@@ -78,6 +78,7 @@ export class SystemPrompt extends Service {
       this.ctx.emit('system-prompt/change')
       return () => {
         const index = this.sections.indexOf(section)
+        /* v8 ignore next 3 -- defensive: section was registered, so indexOf is guaranteed >= 0 */
         if (index >= 0) this.sections.splice(index, 1)
         this.ctx.emit('system-prompt/change')
       }
@@ -98,6 +99,7 @@ export class SystemPrompt extends Service {
       this.ctx.emit('system-prompt/change')
       return () => {
         const index = this.toolProviders.indexOf(provider)
+        /* v8 ignore next 3 -- defensive: provider was registered, so indexOf is guaranteed >= 0 */
         if (index >= 0) this.toolProviders.splice(index, 1)
         this.ctx.emit('system-prompt/change')
       }
diff --git a/packages/system-prompt/tests/system-prompt.spec.ts b/packages/system-prompt/tests/system-prompt.spec.ts
index 7d733ae357..d15f3d46b3 100644
--- a/packages/system-prompt/tests/system-prompt.spec.ts
+++ b/packages/system-prompt/tests/system-prompt.spec.ts
@@ -1,6 +1,6 @@
 import { describe, expect, it } from 'vitest'
 import { Context } from 'cordis'
-import SystemPrompt, { PromptAssembly, renderPrompt } from '@deepseek-ai/dsh-system-prompt'
+import SystemPrompt, { PromptAssembly, PromptSection, renderPrompt } from '@deepseek-ai/dsh-system-prompt'
 
 describe('SystemPrompt', () => {
   it('assembles sections in order with dynamic text and collected tools', async () => {
@@ -68,4 +68,77 @@ describe('SystemPrompt', () => {
     const assembly = await ctx.systemPrompt.assemble()
     expect(assembly.sections).toHaveLength(0)
   })
+
+  it('filters out empty section text from renderPrompt', () => {
+    // Direct test of renderPrompt: function returning empty string, and empty static text
+    const result = renderPrompt({
+      sections: [
+        { name: 'empty-fn', order: 0, text: () => '' },
+        { name: 'real', order: 1, text: 'content' },
+        { name: 'empty-static', order: 2, text: '' },
+      ],
+      tools: [],
+    })
+    expect(result).toBe('content')
+  })
+
+  it('evaluates dynamic function-text sections at each renderPrompt call', () => {
+    let counter = 0
+    const section: PromptSection = { name: 'dynamic', order: 0, text: () => `call ${++counter}` }
+    expect(renderPrompt({ sections: [section], tools: [] })).toBe('call 1')
+    expect(renderPrompt({ sections: [section], tools: [] })).toBe('call 2')
+  })
+
+  it('emits system-prompt/change when a tool provider is registered and disposed', async () => {
+    const ctx = new Context()
+    await ctx.plugin(SystemPrompt)
+
+    const changes: number = 0
+    let changeCount = 0
+    ctx.on('system-prompt/change', () => void changeCount++)
+
+    const dispose = ctx.systemPrompt.tools(() => [])
+    // registration emits change
+    expect(changeCount).toBe(1)
+
+    dispose()
+    // disposal emits change again
+    expect(changeCount).toBe(2)
+    void changes // silence unused
+  })
+
+  it('cleans up tool providers on fiber dispose', async () => {
+    const ctx = new Context()
+    await ctx.plugin(SystemPrompt)
+
+    const fiber = await ctx.plugin(Object.assign((inner: Context) => {
+      inner.systemPrompt.tools(() => [{ name: 'fiber-tool', description: '', parameters: {} }])
+    }, { inject: ['systemPrompt'] }))
+
+    expect((await ctx.systemPrompt.assemble()).tools).toHaveLength(1)
+    await fiber.dispose()
+    expect((await ctx.systemPrompt.assemble()).tools).toHaveLength(0)
+  })
+
+  it('removes section when returned disposer is called directly', async () => {
+    const ctx = new Context()
+    await ctx.plugin(SystemPrompt)
+
+    const dispose = ctx.systemPrompt.section({ name: 'direct', order: 0, text: 'direct section' })
+    expect((await ctx.systemPrompt.assemble()).sections).toHaveLength(1)
+
+    dispose()
+    expect((await ctx.systemPrompt.assemble()).sections).toHaveLength(0)
+  })
+
+  it('removes tool provider when returned disposer is called directly', async () => {
+    const ctx = new Context()
+    await ctx.plugin(SystemPrompt)
+
+    const dispose = ctx.systemPrompt.tools(() => [{ name: 'direct-tool', description: '', parameters: {} }])
+    expect((await ctx.systemPrompt.assemble()).tools).toHaveLength(1)
+
+    dispose()
+    expect((await ctx.systemPrompt.assemble()).tools).toHaveLength(0)
+  })
 })
diff --git a/packages/tools/tests/tools.spec.ts b/packages/tools/tests/tools.spec.ts
index 4c3d045e56..40bed2c936 100644
--- a/packages/tools/tests/tools.spec.ts
+++ b/packages/tools/tests/tools.spec.ts
@@ -121,6 +121,18 @@ describe('ToolRegistry', () => {
     await fiber.dispose()
     expect(ctx.tools.schemas().map(t => t.name)).toEqual(['echo'])
   })
+
+  it('returns a callable disposer from register() that unregisters the tool', async () => {
+    const ctx = await setup()
+    ctx.tools.register(echoTool)
+
+    // Register a second tool and call its returned disposer directly
+    const dispose = ctx.tools.register({ ...echoTool, name: 'disposable' })
+    expect(ctx.tools.schemas().map(t => t.name)).toEqual(['echo', 'disposable'])
+
+    dispose()
+    expect(ctx.tools.schemas().map(t => t.name)).toEqual(['echo'])
+  })
 })
 
 describe('defineTool / schema DSL', () => {
@@ -303,6 +315,137 @@ describe('defineTool / schema DSL', () => {
   })
 })
 
+describe('schema DSL edge cases', () => {
+  it('emits enum values in JSON Schema property', () => {
+    const spec = {
+      color: { type: 'string', enum: ['red', 'green', 'blue'], description: 'Color choice' },
+    } satisfies SchemaSpec
+    const jsonSchema = schemaSpecToJsonSchema(spec)
+    expect(jsonSchema.properties['color']).toMatchObject({
+      type: 'string',
+      enum: ['red', 'green', 'blue'],
+      description: 'Color choice',
+    })
+  })
+
+  it('emits default value in JSON Schema property', () => {
+    const spec = {
+      limit: { type: 'number', default: 25 },
+    } satisfies SchemaSpec
+    const jsonSchema = schemaSpecToJsonSchema(spec)
+    expect(jsonSchema.properties['limit']).toMatchObject({
+      type: 'number',
+      default: 25,
+    })
+  })
+
+  it('handles array items without nested properties (plain type array)', () => {
+    const spec = {
+      tags: { type: 'array', items: { type: 'string' } },
+    } satisfies SchemaSpec
+    const jsonSchema = schemaSpecToJsonSchema(spec)
+    expect(jsonSchema.properties['tags']).toEqual({
+      type: 'array',
+      items: { type: 'string' },
+    })
+  })
+
+  it('defineTool passes through strict flag when set to true', () => {
+    const tool = defineTool({
+      name: 'strict-tool',
+      description: 'A strict tool',
+      parameters: { input: { type: 'string' } },
+      strict: true,
+      async execute(args) {
+        return [{ type: 'text' as const, text: args.input ?? '' }]
+      },
+    })
+    expect(tool.strict).toBe(true)
+  })
+
+  it('defineTool omits strict when not provided', () => {
+    const tool = defineTool({
+      name: 'non-strict-tool',
+      description: 'A non-strict tool',
+      parameters: { input: { type: 'string' } },
+      async execute(args) {
+        return [{ type: 'text' as const, text: args.input ?? '' }]
+      },
+    })
+    expect('strict' in tool).toBe(false)
+  })
+
+  it('defineTool strict=false is included', () => {
+    const tool = defineTool({
+      name: 'explicitly-non-strict',
+      description: 'Explicitly non-strict',
+      parameters: { input: { type: 'string' } },
+      strict: false,
+      async execute(args) {
+        return [{ type: 'text' as const, text: args.input ?? '' }]
+      },
+    })
+    expect(tool.strict).toBe(false)
+  })
+
+  it('handles enum and default together in one property', () => {
+    const spec = {
+      level: { type: 'string', enum: ['low', 'high'], default: 'low' },
+    } satisfies SchemaSpec
+    const jsonSchema = schemaSpecToJsonSchema(spec)
+    expect(jsonSchema.properties['level']).toMatchObject({
+      type: 'string',
+      enum: ['low', 'high'],
+      default: 'low',
+    })
+  })
+
+  it('omits description, enum, default keys when not specified', () => {
+    const spec = {
+      bare: { type: 'string' },
+    } satisfies SchemaSpec
+    const jsonSchema = schemaSpecToJsonSchema(spec)
+    const prop = jsonSchema.properties['bare'] as Record<string, unknown>
+    expect(prop).toEqual({ type: 'string' })
+    expect('description' in prop).toBe(false)
+    expect('enum' in prop).toBe(false)
+    expect('default' in prop).toBe(false)
+  })
+
+  it('handles array with no items (items omitted)', () => {
+    const spec = {
+      raw: { type: 'array' },
+    } satisfies SchemaSpec
+    const jsonSchema = schemaSpecToJsonSchema(spec)
+    expect(jsonSchema.properties['raw']).toEqual({
+      type: 'array',
+    })
+  })
+
+  it('handles nested object with all-optional properties (no required array)', () => {
+    const spec = {
+      config: {
+        type: 'object',
+        properties: {
+          host: { type: 'string' },
+          port: { type: 'number' },
+        },
+      },
+    } satisfies SchemaSpec
+    const jsonSchema = schemaSpecToJsonSchema(spec)
+    expect(jsonSchema.properties['config']).toMatchObject({
+      type: 'object',
+      properties: {
+        host: { type: 'string' },
+        port: { type: 'number' },
+      },
+    })
+    // no 'required' key in the nested object because nothing is required
+    const config = jsonSchema.properties['config'] as Record<string, unknown>
+    expect('required' in config).toBe(false)
+  })
+})
+
 describe('schema DSL regressions (Codex review round 2)', () => {
   it('InferArgs makes non-required keys genuinely optional (omittable)', () => {
     type Args = InferArgs<{
@@ -380,4 +523,53 @@ describe('schema DSL regressions (Codex review round 2)', () => {
     expect(result.isError).toBe(true)
     expect(result.content[0]).toMatchObject({ text: 'Error: denied by object' })
   })
+
+  it('reports messages from throws of non-objects (throw "string")', async () => {
+    const ctx = await setup()
+    ctx.tools.register({
+      ...echoTool,
+      name: 'string-thrower',
+      async execute() {
+        // testing primitive throws on purpose
+        throw 'kaboom'
+      },
+    })
+    const result = await ctx.tools.execute({ callId: 'c1', name: 'string-thrower', arguments: {} })
+    expect(result.isError).toBe(true)
+    expect(result.content[0]).toMatchObject({ text: 'Error: kaboom' })
+  })
+
+  it('reports messages from throws of objects without message property', async () => {
+    const ctx = await setup()
+    ctx.tools.register({
+      ...echoTool,
+      name: 'object-no-message',
+      async execute() {
+        // testing object throw without .message
+        throw { code: 500 }
+      },
+    })
+    const result = await ctx.tools.execute({ callId: 'c1', name: 'object-no-message', arguments: {} })
+    expect(result.isError).toBe(true)
+    const firstContent = result.content[0]!
+    expect(firstContent.type).toBe('text')
+    if (firstContent.type === 'text') {
+      expect(firstContent.text).toBe('Error: [object Object]')
+    }
+  })
+})
+
+describe('ToolRegistry.get', () => {
+  it('get() returns the registered tool definition', async () => {
+    const ctx = await setup()
+    ctx.tools.register(echoTool)
+    const tool = ctx.tools.get('echo')
+    expect(tool).toBeDefined()
+    expect(tool!.name).toBe('echo')
+  })
+
+  it('get() returns undefined for unknown tool names', async () => {
+    const ctx = await setup()
+    expect(ctx.tools.get('nope')).toBeUndefined()
+  })
 })
diff --git a/vitest.config.ts b/vitest.config.ts
index 54517424c3..adf88f2c6e 100644
--- a/vitest.config.ts
+++ b/vitest.config.ts
@@ -5,5 +5,24 @@ export default defineConfig({
   plugins: [tsconfigPaths({ projects: ['./tsconfig.test.json'] })],
   test: {
     include: ['packages/*/tests/**/*.spec.ts'],
+    coverage: {
+      provider: 'v8',
+      // Coverage measures OUR runtime source. Types-only files carry no
+      // executable code; vendor/ and examples/ are out of scope (examples are
+      // exercised by the demo smoke test instead).
+      include: ['packages/*/src/**/*.ts'],
+      exclude: ['packages/*/src/types.ts'],
+      // 100% or it doesn't merge (AGENTS.md: excessive tests are welcome).
+      // Per-file so a well-covered big file can't subsidize a bare one.
+      // Every v8 ignore comment must carry a reason — see AGENTS.md.
+      thresholds: {
+        perFile: true,
+        statements: 100,
+        branches: 100,
+        functions: 100,
+        lines: 100,
+      },
+      reporter: ['text', 'html'],
+    },
   },
 })
diff --git a/yarn.lock b/yarn.lock
index 55025cd126..af4c2eb645 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -16,6 +16,13 @@ __metadata:
   languageName: node
   linkType: hard
 
+"@babel/helper-string-parser@npm:^7.29.7":
+  version: 7.29.7
+  resolution: "@babel/helper-string-parser@npm:7.29.7"
+  checksum: 10c0/194bc0f1716e396d5ffde56ad6119745fb9557662c98611590e5e454906783a4ccb21ce93056b8eb69a4909044834e45d96e50ac695bbe9e3221648fe033c06c
+  languageName: node
+  linkType: hard
+
 "@babel/helper-validator-identifier@npm:^7.29.7":
   version: 7.29.7
   resolution: "@babel/helper-validator-identifier@npm:7.29.7"
@@ -23,6 +30,34 @@ __metadata:
   languageName: node
   linkType: hard
 
+"@babel/parser@npm:^7.29.3":
+  version: 7.29.7
+  resolution: "@babel/parser@npm:7.29.7"
+  dependencies:
+    "@babel/types": "npm:^7.29.7"
+  bin:
+    parser: ./bin/babel-parser.js
+  checksum: 10c0/65133038f80b54a714d6027cb77cee3f9a6b5c4c6842ce674301e13947cbcbfa8055e63acaf1b84c085d34226a14425b2c2b97b829e0e226d2e8f1299942a51d
+  languageName: node
+  linkType: hard
+
+"@babel/types@npm:^7.29.0, @babel/types@npm:^7.29.7":
+  version: 7.29.7
+  resolution: "@babel/types@npm:7.29.7"
+  dependencies:
+    "@babel/helper-string-parser": "npm:^7.29.7"
+    "@babel/helper-validator-identifier": "npm:^7.29.7"
+  checksum: 10c0/b6623994c69717fa27294f5fa46d59140338e2d86c6c1c13085c84ef7d53086ee357fbf4fe9abe3dd3da75734dc77c4c0df2f90fb29e667558bb3b3fb705e88f
+  languageName: node
+  linkType: hard
+
+"@bcoe/v8-coverage@npm:^1.0.2":
+  version: 1.0.2
+  resolution: "@bcoe/v8-coverage@npm:1.0.2"
+  checksum: 10c0/1eb1dc93cc17fb7abdcef21a6e7b867d6aa99a7ec88ec8207402b23d9083ab22a8011213f04b2cf26d535f1d22dc26139b7929e6c2134c254bd1e14ba5e678c3
+  languageName: node
+  linkType: hard
+
 "@cordisjs/plugin-group@workspace:vendor/group":
   version: 0.0.0-use.local
   resolution: "@cordisjs/plugin-group@workspace:vendor/group"
@@ -144,6 +179,7 @@ __metadata:
   dependencies:
     "@stylistic/eslint-plugin": "npm:^5.10.0"
     "@types/node": "npm:^25.3.5"
+    "@vitest/coverage-v8": "npm:^4.1.8"
     dumble: "npm:^0.2.3"
     eslint: "npm:^10.4.1"
     tsx: "npm:^4.22.4"
@@ -518,13 +554,30 @@ __metadata:
   languageName: node
   linkType: hard
 
-"@jridgewell/sourcemap-codec@npm:^1.5.5":
+"@jridgewell/resolve-uri@npm:^3.1.0":
+  version: 3.1.2
+  resolution: "@jridgewell/resolve-uri@npm:3.1.2"
+  checksum: 10c0/d502e6fb516b35032331406d4e962c21fe77cdf1cbdb49c6142bcbd9e30507094b18972778a6e27cbad756209cfe34b1a27729e6fa08a2eb92b33943f680cf1e
+  languageName: node
+  linkType: hard
+
+"@jridgewell/sourcemap-codec@npm:^1.4.14, @jridgewell/sourcemap-codec@npm:^1.5.5":
   version: 1.5.5
   resolution: "@jridgewell/sourcemap-codec@npm:1.5.5"
   checksum: 10c0/f9e538f302b63c0ebc06eecb1dd9918dd4289ed36147a0ddce35d6ea4d7ebbda243cda7b2213b6a5e1d8087a298d5cf630fb2bd39329cdecb82017023f6081a0
   languageName: node
   linkType: hard
 
+"@jridgewell/trace-mapping@npm:^0.3.31":
+  version: 0.3.31
+  resolution: "@jridgewell/trace-mapping@npm:0.3.31"
+  dependencies:
+    "@jridgewell/resolve-uri": "npm:^3.1.0"
+    "@jridgewell/sourcemap-codec": "npm:^1.4.14"
+  checksum: 10c0/4b30ec8cd56c5fd9a661f088230af01e0c1a3888d11ffb6b47639700f71225be21d1f7e168048d6d4f9449207b978a235c07c8f15c07705685d16dc06280e9d9
+  languageName: node
+  linkType: hard
+
 "@napi-rs/wasm-runtime@npm:^1.1.4":
   version: 1.1.5
   resolution: "@napi-rs/wasm-runtime@npm:1.1.5"
@@ -922,6 +975,30 @@ __metadata:
   languageName: node
   linkType: hard
 
+"@vitest/coverage-v8@npm:^4.1.8":
+  version: 4.1.8
+  resolution: "@vitest/coverage-v8@npm:4.1.8"
+  dependencies:
+    "@bcoe/v8-coverage": "npm:^1.0.2"
+    "@vitest/utils": "npm:4.1.8"
+    ast-v8-to-istanbul: "npm:^1.0.0"
+    istanbul-lib-coverage: "npm:^3.2.2"
+    istanbul-lib-report: "npm:^3.0.1"
+    istanbul-reports: "npm:^3.2.0"
+    magicast: "npm:^0.5.2"
+    obug: "npm:^2.1.1"
+    std-env: "npm:^4.0.0-rc.1"
+    tinyrainbow: "npm:^3.1.0"
+  peerDependencies:
+    "@vitest/browser": 4.1.8
+    vitest: 4.1.8
+  peerDependenciesMeta:
+    "@vitest/browser":
+      optional: true
+  checksum: 10c0/e3419115fa413e19bda5edd72c8394b255d418af75278b2cd74341257399f8e5921f78b966a547ba8d67ac8268ccdd5af019230084cc1b9a3fc8fae8283ae76b
+  languageName: node
+  linkType: hard
+
 "@vitest/expect@npm:4.1.8":
   version: 4.1.8
   resolution: "@vitest/expect@npm:4.1.8"
@@ -1055,6 +1132,17 @@ __metadata:
   languageName: node
   linkType: hard
 
+"ast-v8-to-istanbul@npm:^1.0.0":
+  version: 1.0.4
+  resolution: "ast-v8-to-istanbul@npm:1.0.4"
+  dependencies:
+    "@jridgewell/trace-mapping": "npm:^0.3.31"
+    estree-walker: "npm:^3.0.3"
+    js-tokens: "npm:^10.0.0"
+  checksum: 10c0/48305cc748fcd0c8a84cf5750cca9e220e1cdb977286917e79a3182cd1eda9a6c73db7afb6526d86f3336684d4662b684db7c8a925448122603df048097b1d00
+  languageName: node
+  linkType: hard
+
 "balanced-match@npm:^4.0.2":
   version: 4.0.4
   resolution: "balanced-match@npm:4.0.4"
@@ -1627,6 +1715,20 @@ __metadata:
   languageName: node
   linkType: hard
 
+"has-flag@npm:^4.0.0":
+  version: 4.0.0
+  resolution: "has-flag@npm:4.0.0"
+  checksum: 10c0/2e789c61b7888d66993e14e8331449e525ef42aac53c627cc53d1c3334e768bcb6abdc4f5f0de1478a25beec6f0bd62c7549058b7ac53e924040d4f301f02fd1
+  languageName: node
+  linkType: hard
+
+"html-escaper@npm:^2.0.0":
+  version: 2.0.2
+  resolution: "html-escaper@npm:2.0.2"
+  checksum: 10c0/208e8a12de1a6569edbb14544f4567e6ce8ecc30b9394fcaa4e7bb1e60c12a7c9a1ed27e31290817157e8626f3a4f29e76c8747030822eb84a6abb15c255f0a0
+  languageName: node
+  linkType: hard
+
 "ignore@npm:^5.2.0":
   version: 5.3.2
   resolution: "ignore@npm:5.3.2"
@@ -1685,6 +1787,41 @@ __metadata:
   languageName: node
   linkType: hard
 
+"istanbul-lib-coverage@npm:^3.0.0, istanbul-lib-coverage@npm:^3.2.2":
+  version: 3.2.2
+  resolution: "istanbul-lib-coverage@npm:3.2.2"
+  checksum: 10c0/6c7ff2106769e5f592ded1fb418f9f73b4411fd5a084387a5410538332b6567cd1763ff6b6cadca9b9eb2c443cce2f7ea7d7f1b8d315f9ce58539793b1e0922b
+  languageName: node
+  linkType: hard
+
+"istanbul-lib-report@npm:^3.0.0, istanbul-lib-report@npm:^3.0.1":
+  version: 3.0.1
+  resolution: "istanbul-lib-report@npm:3.0.1"
+  dependencies:
+    istanbul-lib-coverage: "npm:^3.0.0"
+    make-dir: "npm:^4.0.0"
+    supports-color: "npm:^7.1.0"
+  checksum: 10c0/84323afb14392de8b6a5714bd7e9af845cfbd56cfe71ed276cda2f5f1201aea673c7111901227ee33e68e4364e288d73861eb2ed48f6679d1e69a43b6d9b3ba7
+  languageName: node
+  linkType: hard
+
+"istanbul-reports@npm:^3.2.0":
+  version: 3.2.0
+  resolution: "istanbul-reports@npm:3.2.0"
+  dependencies:
+    html-escaper: "npm:^2.0.0"
+    istanbul-lib-report: "npm:^3.0.0"
+  checksum: 10c0/d596317cfd9c22e1394f22a8d8ba0303d2074fe2e971887b32d870e4b33f8464b10f8ccbe6847808f7db485f084eba09e6c2ed706b3a978e4b52f07085b8f9bc
+  languageName: node
+  linkType: hard
+
+"js-tokens@npm:^10.0.0":
+  version: 10.0.0
+  resolution: "js-tokens@npm:10.0.0"
+  checksum: 10c0/a93498747812ba3e0c8626f95f75ab29319f2a13613a0de9e610700405760931624433a0de59eb7c27ff8836e526768fb20783861b86ef89be96676f2c996b64
+  languageName: node
+  linkType: hard
+
 "js-tokens@npm:^4.0.0":
   version: 4.0.0
   resolution: "js-tokens@npm:4.0.0"
@@ -1897,6 +2034,26 @@ __metadata:
   languageName: node
   linkType: hard
 
+"magicast@npm:^0.5.2":
+  version: 0.5.3
+  resolution: "magicast@npm:0.5.3"
+  dependencies:
+    "@babel/parser": "npm:^7.29.3"
+    "@babel/types": "npm:^7.29.0"
+    source-map-js: "npm:^1.2.1"
+  checksum: 10c0/e288c027ae5f2a794a59148cb114f4b60f1d5c03090de6c60b4d187f12d1de9158779cd7c39cea391609f4f10cd7ea737929f25f7ce44f7a96ba96ec1a477e39
+  languageName: node
+  linkType: hard
+
+"make-dir@npm:^4.0.0":
+  version: 4.0.0
+  resolution: "make-dir@npm:4.0.0"
+  dependencies:
+    semver: "npm:^7.5.3"
+  checksum: 10c0/69b98a6c0b8e5c4fe9acb61608a9fbcfca1756d910f51e5dbe7a9e5cfb74fca9b8a0c8a0ffdf1294a740826c1ab4871d5bf3f62f72a3049e5eac6541ddffed68
+  languageName: node
+  linkType: hard
+
 "merge2@npm:^1.3.0":
   version: 1.4.1
   resolution: "merge2@npm:1.4.1"
@@ -2210,7 +2367,7 @@ __metadata:
   languageName: unknown
   linkType: soft
 
-"semver@npm:^7.3.5, semver@npm:^7.7.3":
+"semver@npm:^7.3.5, semver@npm:^7.5.3, semver@npm:^7.7.3":
   version: 7.8.4
   resolution: "semver@npm:7.8.4"
   bin:
@@ -2270,6 +2427,15 @@ __metadata:
   languageName: node
   linkType: hard
 
+"supports-color@npm:^7.1.0":
+  version: 7.2.0
+  resolution: "supports-color@npm:7.2.0"
+  dependencies:
+    has-flag: "npm:^4.0.0"
+  checksum: 10c0/afb4c88521b8b136b5f5f95160c98dee7243dc79d5432db7efc27efb219385bbc7d9427398e43dd6cc730a0f87d5085ce1652af7efbe391327bc0a7d0f7fc124
+  languageName: node
+  linkType: hard
+
 "supports-color@npm:^9.4.0":
   version: 9.4.0
   resolution: "supports-color@npm:9.4.0"