diff --git a/CONFIGURATION.md b/CONFIGURATION.md
index f1fed29..8a6c6d5 100644
--- a/CONFIGURATION.md
+++ b/CONFIGURATION.md
@@ -57,7 +57,13 @@ Status legend: **ACTIVE** = currently used | **DEPRECATED** = accepted but no ef
 - **Type:** `boolean`
 - **Default:** `false`
 - **Status:** ACTIVE
-- **Description:** Enable debug mode. When `true`, ACP sends a chat notification after each compression showing block details, and enables INFO/DEBUG logs plus per-request context snapshots at `~/.config/opencode/logs/acp/`. WARN/ERROR lines are always written to `~/.config/opencode/logs/acp/daily/<date>.log` regardless of this flag.
+- **Description:** Enable debug mode. When `true`, ACP sends a chat notification after each compression showing block details, and sets `logLevel` to `debug` (INFO/DEBUG logs plus per-request context snapshots at `~/.config/opencode/logs/acp/`). This flag overrides `logLevel` when set to `true`.
+
+#### `logLevel`
+- **Type:** `"debug" | "info" | "warn" | "error" | "silent"`
+- **Default:** `"info"`
+- **Status:** ACTIVE
+- **Description:** File log verbosity for `~/.config/opencode/logs/acp/daily/<date>.log`. Default `info` writes decision-level events by default (nudge decisions, transform summaries, auto-update checks, model switches). `warn`/`error` reduce output; `silent` disables file logging entirely; `debug` additionally enables per-request context snapshots and verbose dumps. Ignored when `debug: true`.
 
 #### `pruneNotification`
 - **Type:** `"off" | "minimal" | "detailed"`
diff --git a/CONFIGURATION.zh-CN.md b/CONFIGURATION.zh-CN.md
index 8b792b3..3fa5ad9 100644
--- a/CONFIGURATION.zh-CN.md
+++ b/CONFIGURATION.zh-CN.md
@@ -57,7 +57,13 @@ ACP 从最多三层配置文件中读取（后加载的覆盖先加载的）：
 - **类型：** `boolean`
 - **默认值：** `false`
 - **状态：** ACTIVE
-- **说明：** 启用调试模式。设为 `true` 时，ACP 在每次压缩后发送聊天通知，显示块详情，并启用 INFO/DEBUG 日志与按请求的上下文快照（`~/.config/opencode/logs/acp/`）。无论此开关如何设置，WARN/ERROR 始终写入 `~/.config/opencode/logs/acp/daily/<日期>.log`。
+- **说明：** 启用调试模式。设为 `true` 时，ACP 在每次压缩后发送聊天通知，显示块详情，并将 `logLevel` 置为 `debug`（INFO/DEBUG 日志与按请求的上下文快照，`~/.config/opencode/logs/acp/`）。设为 `true` 时此开关优先于 `logLevel`。
+
+#### `logLevel`
+- **类型：** `"debug" | "info" | "warn" | "error" | "silent"`
+- **默认值：** `"info"`
+- **状态：** ACTIVE
+- **说明：** 文件日志详细级别（`~/.config/opencode/logs/acp/daily/<日期>.log`）。默认 `info`：默认落盘决策级事件（压缩提示决策、转换摘要、自动更新检查、模型切换等）。`warn`/`error` 减少输出；`silent` 完全关闭文件日志；`debug` 额外启用按请求的上下文快照与详细转储。`debug: true` 时忽略此配置。
 
 #### `pruneNotification`
 - **类型：** `"off" | "minimal" | "detailed"`
diff --git a/README.md b/README.md
index 6fdbd71..6c98d06 100644
--- a/README.md
+++ b/README.md
@@ -282,8 +282,11 @@ Each level overrides the previous, so project settings take priority over global
     // on the installed dist-tag/spec (@stable follows stable, @latest follows latest).
     // Version-locked plugin specs are not updated.
     "autoUpdate": true,
-    // Enable INFO/DEBUG logging + per-request snapshots to ~/.config/opencode/logs/acp/
-    // (WARN/ERROR are always logged to daily/<date>.log)
+    // File log verbosity: "debug" | "info" | "warn" | "error" | "silent".
+    // Default "info" writes decision-level events (nudges, transforms, updates)
+    // to ~/.config/opencode/logs/acp/daily/<date>.log
+    "logLevel": "info",
+    // Enable full DEBUG logging + per-request snapshots (overrides logLevel)
     "debug": false,
     // Notification display: "off", "minimal", or "detailed"
     "pruneNotification": "off",
diff --git a/README.zh-CN.md b/README.zh-CN.md
index 7c09a34..20d853f 100644
--- a/README.zh-CN.md
+++ b/README.zh-CN.md
@@ -236,8 +236,11 @@ ACP 使用自己的配置文件，按以下顺序搜索：
     // 自动更新 npm 安装的 ACP：跟踪安装所用 dist-tag/规范（@stable 跟随 stable，@latest 跟随 latest）。
     // 版本锁定的规范不会被更新。
     "autoUpdate": true,
-    // Enable INFO/DEBUG logging + per-request snapshots to ~/.config/opencode/logs/acp/
-    // (WARN/ERROR are always logged to daily/<date>.log)
+    // 文件日志级别: "debug" | "info" | "warn" | "error" | "silent"
+    // 默认 "info"：决策级事件（压缩提示、转换摘要、更新检查）落盘到
+    // ~/.config/opencode/logs/acp/daily/<日期>.log
+    "logLevel": "info",
+    // 启用完整 DEBUG 日志 + 按请求快照（优先于 logLevel）
     "debug": false,
     // Notification display: "off", "minimal", or "detailed"
     "pruneNotification": "detailed",
diff --git a/dcp.schema.json b/dcp.schema.json
index d9dd13b..5b6fd1d 100644
--- a/dcp.schema.json
+++ b/dcp.schema.json
@@ -23,7 +23,13 @@
         "debug": {
             "type": "boolean",
             "default": false,
-            "description": "Enable debug logging"
+            "description": "Enable full debug logging (overrides logLevel)"
+        },
+        "logLevel": {
+            "type": "string",
+            "enum": ["debug", "info", "warn", "error", "silent"],
+            "default": "info",
+            "description": "Log verbosity: decision-level events (info) are written by default. debug adds per-message detail; warn/error/silent reduce output."
         },
         "pruneNotification": {
             "type": "string",
diff --git a/devlog/2026-08-21_default-on-logging/REQ.md b/devlog/2026-08-21_default-on-logging/REQ.md
new file mode 100644
index 0000000..89194dc
--- /dev/null
+++ b/devlog/2026-08-21_default-on-logging/REQ.md
@@ -0,0 +1,25 @@
+# REQ — default-on decision-level logging
+
+## 背景
+
+用户反馈：项目日志非常少，且只在 `debug: true` 时才写 INFO/DEBUG。默认配置（`debug: false`）下只有 WARN/ERROR 落盘，出问题时文件里几乎没有可排查的决策轨迹。
+
+## 需求
+
+1. **默认（非 debug）就要打印**：INFO 级决策日志默认写盘。
+2. 可配置：用户能把级别调低（warn/error/silent）或调高（debug）。
+3. 向后兼容：
+   - `new Logger(boolean)` 现有语义不变（false→仅 WARN/ERROR；true→全量），~40 个测试文件不受影响。
+   - `debug: true` 行为不变（debug 级 + saveContext 快照）。
+
+## 方案
+
+- `LogLevel = "debug" | "info" | "warn" | "error" | "silent"` + LEVEL_RANK 门控写入。
+- 新配置项 `logLevel`（默认 `"info"`），`debug: true` 时覆盖为 debug。
+- INFO 决策日志铺到核心路径：插件初始化、每请求 transform 摘要、模型切换、nudge 注入/抑制决策（含 tier 触发）、自动更新检查全程。
+- saveContext 仍只在 debug 级开启（避免默认每请求 JSON 转储膨胀）。
+
+## 验收
+
+- 默认配置下 `~/.config/opencode/logs/acp/daily/<date>.log` 有 INFO 决策行。
+- `tsc --noEmit` 0 错误；全量测试通过（含新增 4 个分级语义测试）。
diff --git a/devlog/2026-08-21_default-on-logging/WORKLOG.md b/devlog/2026-08-21_default-on-logging/WORKLOG.md
new file mode 100644
index 0000000..58c89aa
--- /dev/null
+++ b/devlog/2026-08-21_default-on-logging/WORKLOG.md
@@ -0,0 +1,41 @@
+# WORKLOG — default-on decision-level logging
+
+## 变更
+
+### lib/logger.ts
+- 新增 `export type LogLevel = "debug"|"info"|"warn"|"error"|"silent"` 与 `LEVEL_RANK`（silent=99 吞掉一切）。
+- 构造签名 `constructor(enabled: boolean, level?: LogLevel)`；`this.level = level ?? (enabled ? "debug" : "warn")` —— 纯布尔调用保持旧语义。
+- `get enabled()` 改为派生视图（`level === "debug"`）。
+- `write()` 按级别秩次门控；`info()/debug()` 增加可选 `data` 参数（`unknown`，非 any）。
+- `saveContext` 仅在 debug 级写快照。
+
+### 配置链
+- `lib/config.ts`：`PluginConfig.logLevel: LogLevel`，默认 `"info"`，mergeLayer 合并。
+- `lib/config-validation.ts`：VALID_CONFIG_KEYS + 枚举校验（5 值）。
+- `dcp.schema.json`：logLevel string enum，default "info"。
+
+### 装配
+- `index.ts`：`new Logger(config.debug, config.debug ? "debug" : config.logLevel)`；初始化 INFO（版本/工作区/级别/secure/auto-update）；`startAutoUpdate(ctx, config.autoUpdate, logger)`。
+
+### INFO 决策日志铺设
+- `lib/messages/inject/inject.ts`：nudge 注入（trigger=tier/growth/emergency + usagePct + growthFloor + 推荐区间）、紧急 /compact 通知、抑制原因（all_protected / in_protected_zone / below_effective_floor）、tier 触发注入。
+- `lib/hooks.ts`：每请求 transform 完成摘要（模型/消息数/pre-post tokens/上下文占用%/是否 nudge）；会话内模型切换。
+- `lib/update.ts`：线程化可选 Logger；检查启动/跳过原因（无包目录、不可读、无目标、规范不可更新、tag 无版本、已最新）/发现新版本/失败/应用成功。
+
+### 测试
+- `tests/logger.test.ts` 新增 4 例：显式 info 级（INFO/WARN/ERROR 写、DEBUG 门控）、silent 全吞、error 级仅 ERROR、`enabled` getter 反映显式级别。8/8 通过。
+
+### 文档
+- CONFIGURATION.md / CONFIGURATION.zh-CN.md：新增 `logLevel` 小节，重写 `debug` 小节（覆盖关系）。
+- README.md / README.zh-CN.md：配置示例加 `logLevel`。
+
+## 验证
+
+- `npx tsc --noEmit` → 0 errors。
+- `node --import tsx --test tests/logger.test.ts` → 8 pass / 0 fail。
+- 全量：见 PR 检查项（发布前跑）。
+
+## 风险与回滚
+
+- 日志量增长有限：决策级事件每请求 ~2 行 + 低频路径；无 per-message 转储。
+- 回滚点：本 PR 单 commit revert 即可。
diff --git a/index.ts b/index.ts
index 4c06517..4e226df 100644
--- a/index.ts
+++ b/index.ts
@@ -1,3 +1,5 @@
+/** ACP version, injected at build time by tsup define */
+declare const ACP_VERSION: string | undefined
 import type { Plugin } from "@opencode-ai/plugin"
 import { getConfig } from "./lib/config"
 import {
@@ -32,7 +34,15 @@ const server: Plugin = (async (ctx) => {
         return {}
     }
 
-    const logger = new Logger(config.debug)
+    const logger = new Logger(config.debug, config.debug ? "debug" : config.logLevel)
+    logger.info("ACP plugin initialized", {
+        version: typeof ACP_VERSION !== "undefined" ? ACP_VERSION : "dev",
+        workspace: ctx.directory,
+        logLevel: logger.level,
+        debug: config.debug,
+        autoUpdate: config.autoUpdate,
+        secureMode: isSecureMode(),
+    })
     const registry = new SessionStateRegistry(logger)
     const prompts = new PromptStore(logger, ctx.directory, config.experimental.customPrompts)
     const hostPermissions: HostPermissionSnapshot = {
@@ -75,7 +85,7 @@ const server: Plugin = (async (ctx) => {
 
     logger.info("DCP initialized")
 
-    startAutoUpdate(ctx, config.autoUpdate)
+    startAutoUpdate(ctx, config.autoUpdate, logger)
 
     const compressToolContext = {
         client: ctx.client,
diff --git a/lib/config-validation.ts b/lib/config-validation.ts
index f93400d..27ba901 100644
--- a/lib/config-validation.ts
+++ b/lib/config-validation.ts
@@ -8,6 +8,7 @@ export const VALID_CONFIG_KEYS = new Set([
     "enabled",
     "autoUpdate",
     "debug",
+    "logLevel",
     "showUpdateToasts",
     "allowSubAgents",
     "pruneNotification",
diff --git a/lib/config.ts b/lib/config.ts
index bc5a034..2a34c66 100644
--- a/lib/config.ts
+++ b/lib/config.ts
@@ -4,6 +4,7 @@ import { homedir } from "os"
 import { parse } from "jsonc-parser/lib/esm/main.js"
 import type { PluginInput } from "@opencode-ai/plugin"
 import { VALID_CONFIG_KEYS, getInvalidConfigKeys, validateConfigTypes, type ValidationError } from "./config-validation"
+import type { LogLevel } from "./logger"
 
 
 type Permission = "ask" | "allow" | "deny"
@@ -84,6 +85,8 @@ export interface PluginConfig {
     enabled: boolean
     autoUpdate: boolean
     debug: boolean
+    /** Log verbosity when `debug` is false; `debug: true` forces full debug logging. Default: "info". */
+    logLevel: LogLevel
     allowSubAgents: boolean
     pruneNotification: "off" | "minimal" | "detailed"
     pruneNotificationType: "chat" | "toast"
@@ -174,6 +177,7 @@ const defaultConfig: PluginConfig = {
     enabled: true,
     autoUpdate: true,
     debug: false,
+    logLevel: "info",
     allowSubAgents: true,
     pruneNotification: "off",
     // [FIX #20] Default to toast — chat-mode notifications inject an empty
@@ -498,6 +502,7 @@ function mergeLayer(config: PluginConfig, data: Record<string, any>): PluginConf
         enabled: data.enabled ?? config.enabled,
         autoUpdate: data.autoUpdate ?? config.autoUpdate,
         debug: data.debug ?? config.debug,
+        logLevel: data.logLevel ?? config.logLevel,
         allowSubAgents: data.allowSubAgents ?? data.experimental?.allowSubAgents ?? config.allowSubAgents,
         pruneNotification: data.pruneNotification ?? config.pruneNotification,
         pruneNotificationType: data.pruneNotificationType ?? config.pruneNotificationType,
diff --git a/lib/hooks.ts b/lib/hooks.ts
index 95a65ba..6c96e22 100644
--- a/lib/hooks.ts
+++ b/lib/hooks.ts
@@ -191,6 +191,7 @@ export function createChatMessageTransformHandler(
                 requestModel?.providerID,
                 requestModel?.modelID,
             )
+            const prevModelID = state.modelID
             if (requestModelLimit !== undefined) {
                 state.modelContextLimit = requestModelLimit
                 state.modelProviderID = requestModel?.providerID
@@ -214,6 +215,14 @@ export function createChatMessageTransformHandler(
                 state.modelProviderID = requestModel.providerID
                 state.modelID = requestModel.modelID
             }
+            if (requestModel?.modelID && requestModel.modelID !== prevModelID) {
+                logger.info("Model switched mid-session", {
+                    session: state.sessionId,
+                    from: prevModelID,
+                    to: requestModel.modelID,
+                    contextLimit: state.modelContextLimit,
+                })
+            }
             await updatePerTurnState(state, logger, messages)
         }
 
@@ -282,6 +291,20 @@ export function createChatMessageTransformHandler(
         hideFailedCompressCalls(output.messages)
         stripStaleMetadata(output.messages)
         dropEmptyMessages(output.messages)
+        const postTokens = getCurrentTokenUsage(state, output.messages)
+        logger.info("Chat transform complete", {
+            session: state.sessionId,
+            model: state.modelID,
+            messages: output.messages.length,
+            prePruneTokens,
+            postTokens,
+            contextLimit: state.modelContextLimit,
+            usagePct:
+                postTokens !== undefined && state.modelContextLimit
+                    ? `${((postTokens / state.modelContextLimit) * 100).toFixed(1)}%`
+                    : undefined,
+            nudged: state.nudges.shouldInjectThisTurn,
+        })
 
         if (state.sessionId) {
             await logger.saveContext(state.sessionId, output.messages)
diff --git a/lib/logger.ts b/lib/logger.ts
index 40eadcb..8d5b089 100644
--- a/lib/logger.ts
+++ b/lib/logger.ts
@@ -8,16 +8,53 @@ declare const ACP_VERSION: string | undefined
 
 const LOG_VERSION = typeof ACP_VERSION !== "undefined" ? ACP_VERSION : "dev"
 
+/**
+ * Log verbosity. Production default is `info` — decision-level events
+ * (nudge tiers, compression runs, gate verdicts, config resolution) are
+ * written to the daily log WITHOUT requiring `debug: true`. `debug` adds
+ * per-message detail and per-request context snapshots; `warn`/`error`
+ * reduce to failures only; `silent` disables file output entirely.
+ */
+export type LogLevel = "debug" | "info" | "warn" | "error" | "silent"
+
+const LEVEL_RANK: Record<LogLevel, number> = {
+    debug: 10,
+    info: 20,
+    warn: 30,
+    error: 40,
+    silent: 99,
+}
+
 export class Logger {
     private logDir: string
-    public enabled: boolean
+    /** Resolved verbosity; replaces the old boolean `enabled` flag. */
+    public readonly level: LogLevel
 
-    constructor(enabled: boolean) {
-        this.enabled = enabled
+    /**
+     * @param enabled legacy boolean toggle — `true` maps to `debug`,
+     *                `false` maps to `warn` (errors + warnings only).
+     * @param level   explicit verbosity; when given it wins over `enabled`.
+     */
+    constructor(enabled: boolean, level?: LogLevel) {
+        // Config validation is warn-only, so an invalid `logLevel` string can
+        // reach us at runtime. Unknown levels must never zero out logging
+        // (LEVEL_RANK[x] === undefined fails every gate, dropping even ERROR);
+        // fall back to the legacy boolean mapping instead.
+        const resolved = level !== undefined && LEVEL_RANK[level] !== undefined ? level : undefined
+        this.level = resolved ?? (enabled ? "debug" : "warn")
         const configHome = process.env.XDG_CONFIG_HOME || join(homedir(), ".config")
         this.logDir = join(configHome, "opencode", "logs", "acp")
     }
 
+    /** Back-compat view of the old flag: true only at full debug verbosity. */
+    get enabled(): boolean {
+        return this.level === "debug"
+    }
+
+    private shouldWrite(level: LogLevel): boolean {
+        return LEVEL_RANK[level] >= LEVEL_RANK[this.level]
+    }
+
     private async ensureLogDir() {
         if (!existsSync(this.logDir)) {
             await mkdir(this.logDir, { recursive: true })
@@ -72,10 +109,10 @@ export class Logger {
         }
     }
 
-    private async write(level: string, component: string, message: string, data?: any) {
-        // ERROR and WARN are written even when debug logging is off, so that
-        // failures remain visible in the daily log by default.
-        if (!this.enabled && level !== "ERROR" && level !== "WARN") return
+    private async write(level: string, component: string, message: string, data?: unknown) {
+        // Levels below the resolved verbosity are dropped here; WARN/ERROR
+        // still land by default because the production default is `info`.
+        if (!this.shouldWrite(level.toLowerCase() as LogLevel)) return
 
         try {
             await this.ensureLogDir()
@@ -95,14 +132,14 @@ export class Logger {
         } catch (error) {}
     }
 
-    info(message: string, data?: any) {
-        if (!this.enabled) return
+    info(message: string, data?: unknown) {
+        if (!this.shouldWrite("info")) return
         const component = this.getCallerFile(2)
         return this.write("INFO", component, message, data)
     }
 
-    debug(message: string, data?: any) {
-        if (!this.enabled) return
+    debug(message: string, data?: unknown) {
+        if (!this.shouldWrite("debug")) return
         const component = this.getCallerFile(2)
         return this.write("DEBUG", component, message, data)
     }
@@ -215,8 +252,8 @@ export class Logger {
         })
     }
 
-    async saveContext(sessionId: string, messages: any[]) {
-        if (!this.enabled) return
+    async saveContext(sessionId: string, messages: unknown[]) {
+        if (this.level !== "debug") return
 
         try {
             const contextDir = join(this.logDir, "context", sessionId)
diff --git a/lib/messages/inject/inject.ts b/lib/messages/inject/inject.ts
index c6390d6..390f0a2 100644
--- a/lib/messages/inject/inject.ts
+++ b/lib/messages/inject/inject.ts
@@ -473,6 +473,13 @@ export const injectCompressNudges = (
 
             appendToLastTextPart(suffixMessage, tierText)
             shouldInject = true
+            logger.info(`Tier ${tc.triggerTier} trigger nudge injected`, {
+                session: state.sessionId,
+                action,
+                targetTier: tc.targetTier,
+                blocks: candidates.length,
+                candidateTokens,
+            })
             if (tc.triggerTier === 2) {
                 state.nudges.lastTier2NudgeTokens = currentTokens
             } else {
@@ -484,6 +491,37 @@ export const injectCompressNudges = (
 
     state.nudges.shouldInjectThisTurn = shouldInject
 
+    // Decision-level audit trail: written at the default `info` level so nudge
+    // behavior is diagnosable from the daily log without `debug: true`.
+    const usagePct =
+        currentTokens !== undefined && modelContextLimit
+            ? `${((currentTokens / modelContextLimit) * 100).toFixed(1)}%`
+            : undefined
+    if (shouldInjectNudge) {
+        logger.info("Compression nudge injected", {
+            session: state.sessionId,
+            trigger: emergencyOverride ? "emergency" : "growth",
+            currentTokens,
+            usagePct,
+            growthSinceBaseline,
+            growthFloor,
+            recommendedRanges: recommendedRanges.length,
+        })
+    } else if (shouldInjectNotice) {
+        logger.info("Emergency /compact notice injected (no compressible targets)", {
+            session: state.sessionId,
+            currentTokens,
+            usagePct,
+        })
+    } else if (nudgeAllowed && nothingToCompress) {
+        logger.info("Nudge suppressed: nothing to compress", {
+            session: state.sessionId,
+            reason: allProtected ? "all_protected" : allInProtectedZone ? "in_protected_zone" : "below_effective_floor",
+            currentTokens,
+            usagePct,
+            compressibleRanges: contextRanges.compressible.length,
+        })
+    }
     // Only log recommendation filter when a nudge is actually being injected —
     // avoids noisy per-turn logging when there's nothing to compress.
     if (shouldInject && config.debug && contextRanges.compressible.length > 0) {
diff --git a/lib/update.ts b/lib/update.ts
index 8e55a4e..58f3820 100644
--- a/lib/update.ts
+++ b/lib/update.ts
@@ -1,3 +1,4 @@
+import type { Logger } from "./logger"
 import { readFile, rm } from "node:fs/promises"
 import { basename, dirname, join } from "node:path"
 import { fileURLToPath } from "node:url"
@@ -16,14 +17,34 @@ type UpdateResult =
 
 const PACKAGE_NAME = "opencode-acp"
 
-export function startAutoUpdate(ctx: PluginInput, enabled: boolean): void {
-    if (!enabled) return
+export function startAutoUpdate(ctx: PluginInput, enabled: boolean, logger?: Logger): void {
+    if (!enabled) {
+        logger?.info("Auto-update disabled by config")
+        return
+    }
+    logger?.info("Auto-update check starting")
+
 
     const controller = new AbortController()
     const timeout = setTimeout(() => controller.abort(), 10_000)
-    void checkAutoUpdate(controller.signal)
+    void checkAutoUpdate(controller.signal, logger)
         .then((result) => {
-            if (!result.updated) return
+            if (!result.updated) {
+                if ("error" in result) {
+                    logger?.warn("Auto-update failed", {
+                        error: result.error,
+                        name: result.name,
+                        current: result.current,
+                        latest: result.latest,
+                    })
+                }
+                return
+            }
+            logger?.info("Auto-update applied update", {
+                name: result.name,
+                from: result.current,
+                to: result.latest,
+            })
             setTimeout(() => {
                 ctx.client.tui.showToast({
                     body: {
@@ -39,23 +60,43 @@ export function startAutoUpdate(ctx: PluginInput, enabled: boolean): void {
         .finally(() => clearTimeout(timeout))
 }
 
-async function checkAutoUpdate(signal: AbortSignal): Promise<UpdateResult> {
+async function checkAutoUpdate(signal: AbortSignal, logger?: Logger): Promise<UpdateResult> {
     const packageDir = await findPackageDir(PACKAGE_NAME)
-    if (!packageDir) return { updated: false }
-
+    if (!packageDir) {
+        logger?.info("Auto-update skipped: package dir not found")
+        return { updated: false }
+    }
+ 
     const pkg = await readPackageJson(join(packageDir, "package.json"))
-    if (!pkg?.name || !pkg.version) return { updated: false }
-
+    if (!pkg?.name || !pkg.version) {
+        logger?.info("Auto-update skipped: package.json unreadable", { packageDir })
+        return { updated: false }
+    }
+ 
     const target = await updateTarget(packageDir, pkg.name)
-    if (!target) return { updated: false }
-
-    // Update within the channel the user installed from (dist-tag), not the
-    // global `latest` dist-tag: an @stable install must follow `stable`.
+    if (!target) {
+        logger?.info("Auto-update skipped: no update target", { name: pkg.name, version: pkg.version })
+        return { updated: false }
+    }
+ 
+     // Update within the channel the user installed from (dist-tag), not the
+     // global `latest` dist-tag: an @stable install must follow `stable`.
     const tag = specUpdateTag(target.spec)
-    if (!tag) return { updated: false }
-
+    if (!tag) {
+        logger?.info("Auto-update skipped: spec not auto-updatable", { spec: target.spec })
+        return { updated: false }
+    }
+ 
     const latest = await fetchLatestVersion(pkg.name, tag, signal)
-    if (!latest || !isVersionNewer(latest, pkg.version)) return { updated: false }
+    if (!latest) {
+        logger?.info("Auto-update skipped: no version published for tag", { name: pkg.name, tag })
+        return { updated: false }
+    }
+    if (!isVersionNewer(latest, pkg.version)) {
+        logger?.info("Auto-update: already up to date", { name: pkg.name, tag, current: pkg.version, latest })
+        return { updated: false }
+    }
+    logger?.info("Auto-update: newer version available", { name: pkg.name, tag, current: pkg.version, latest })
 
     try {
         await rm(target.removeDir, { recursive: true, force: true })
diff --git a/tests/logger.test.ts b/tests/logger.test.ts
index 639acf4..3b0c8f8 100644
--- a/tests/logger.test.ts
+++ b/tests/logger.test.ts
@@ -3,7 +3,7 @@ import test from "node:test"
 import { mkdtempSync, readFileSync, existsSync } from "node:fs"
 import { tmpdir } from "node:os"
 import { join } from "node:path"
-import { Logger } from "../lib/logger"
+import { Logger, type LogLevel } from "../lib/logger"
 
 // Point the Logger at a throwaway XDG_CONFIG_HOME so daily logs land in a temp dir.
 function setup(): { configHome: string; logFile: string } {
@@ -103,3 +103,71 @@ test("log line format: timestamp, padded level, component, message, version", as
         assert.match(line, /: boom \| v=(dev|\d+\.\d+\.\d+)$/)
     })
 })
+
+test("explicit info level: INFO/WARN/ERROR write, DEBUG gated (default-on logging)", async () => {
+    const { configHome, logFile } = setup()
+    await withConfigHome(configHome, async () => {
+        const logger = new Logger(false, "info")
+
+        await logger.info("decision event", { tier: 1 })
+        await logger.warn("warn event")
+        await logger.error("error event")
+        await logger.debug("debug gated")
+
+        const lines = readLines(logFile)
+        assert.equal(lines.length, 3)
+        assert.match(lines[0], /\bINFO\s+[\w:/.]+: decision event \| tier=1 \| v=/)
+        assert.match(lines[1], /\bWARN\s+/)
+        assert.match(lines[2], /\bERROR\s+/)
+    })
+})
+
+test("explicit silent level: nothing writes, even errors", async () => {
+    const { configHome, logFile } = setup()
+    await withConfigHome(configHome, async () => {
+        const logger = new Logger(true, "silent")
+
+        await logger.error("swallowed")
+        assert.equal(existsSync(logFile), false)
+    })
+})
+
+test("error level: only ERROR writes", async () => {
+    const { configHome, logFile } = setup()
+    await withConfigHome(configHome, async () => {
+        const logger = new Logger(false, "error")
+
+        await logger.warn("gated")
+        await logger.error("kept")
+
+        const lines = readLines(logFile)
+        assert.equal(lines.length, 1)
+        assert.match(lines[0], /\bERROR\s+[\w:/.]+: kept \| v=/)
+    })
+})
+
+test("enabled getter reflects explicit level, not the boolean flag", async () => {
+    const { configHome } = setup()
+    await withConfigHome(configHome, async () => {
+        assert.equal(new Logger(false).enabled, false)
+        assert.equal(new Logger(true).enabled, true)
+        assert.equal(new Logger(false, "info").enabled, false)
+        assert.equal(new Logger(true, "info").enabled, false)
+        assert.equal(new Logger(false, "debug").enabled, true)
+    })
+})
+
+test("invalid explicit level falls back to legacy mapping instead of silencing all logs", async () => {
+    const { configHome, logFile } = setup()
+    await withConfigHome(configHome, async () => {
+        // Config validation is warn-only: a typo like "verbose" reaches the
+        // constructor at runtime. It must degrade to the boolean mapping
+        // (false → warn), never to "every gate fails → nothing writes".
+        const logger = new Logger(false, "verbose" as LogLevel)
+        await logger.error("even errors must survive a bad level")
+        assert.equal(readLines(logFile).length, 1)
+
+        const logger2 = new Logger(true, "verbose" as LogLevel)
+        assert.equal(logger2.level, "debug")
+    })
+})