diff --git a/examples/statusline.json b/examples/statusline.json
index 4fa84e81..61413609 100644
--- a/examples/statusline.json
+++ b/examples/statusline.json
@@ -1,19 +1,20 @@
 {
   "statusLine": {
     "type": "command",
-    "command": "input=$(cat); user=$(whoami); cwd=$(echo \"$input\" | jq -r '.workspace.current_dir' | sed \"s|$HOME|~|g\"); model=$(echo \"$input\" | jq -r '.model.display_name'); time=$(date +%H:%M); remaining=$(echo \"$input\" | jq -r '.context_window.remaining_percentage // empty'); transcript=$(echo \"$input\" | jq -r '.transcript_path'); todo_count=$([ -f \"$transcript\" ] && grep -c '\"type\":\"todo\"' \"$transcript\" 2>/dev/null || echo 0); cd \"$(echo \"$input\" | jq -r '.workspace.current_dir')\" 2>/dev/null; branch=$(git rev-parse --abbrev-ref HEAD 2>/dev/null || echo ''); status=''; [ -n \"$branch\" ] && { [ -n \"$(git status --porcelain 2>/dev/null)\" ] && status='*'; }; B='\\033[38;2;30;102;245m'; G='\\033[38;2;64;160;43m'; Y='\\033[38;2;223;142;29m'; M='\\033[38;2;136;57;239m'; C='\\033[38;2;23;146;153m'; R='\\033[0m'; T='\\033[38;2;76;79;105m'; printf \"${C}${user}${R}:${B}${cwd}${R}\"; [ -n \"$branch\" ] && printf \" ${G}${branch}${Y}${status}${R}\"; [ -n \"$remaining\" ] && printf \" ${M}ctx:${remaining}%%${R}\"; printf \" ${T}${model}${R} ${Y}${time}${R}\"; [ \"$todo_count\" -gt 0 ] && printf \" ${C}todos:${todo_count}${R}\"; echo",
-    "description": "Custom status line showing: user:path branch* ctx:% model time todos:N"
+    "command": "node \"<plugin-root>/scripts/hooks/ecc-statusline.js\"",
+    "description": "ECC statusline: model | task | $cost tools files duration | dir | context bar"
   },
   "_comments": {
+    "setup": "Replace <plugin-root> with your ECC installation path. For plugin installs, use the resolved path from CLAUDE_PLUGIN_ROOT.",
+    "display": "Shows model name, current task, session cost, tool count, files modified, session duration, directory, and context usage bar with color thresholds.",
     "colors": {
-      "B": "Blue - directory path",
-      "G": "Green - git branch",
-      "Y": "Yellow - dirty status, time",
-      "M": "Magenta - context remaining",
-      "C": "Cyan - username, todos",
-      "T": "Gray - model name"
+      "green": "Context used < 50%",
+      "yellow": "Context used < 65%",
+      "orange": "Context used < 80%",
+      "red_blink": "Context used >= 80%"
     },
-    "output_example": "affoon:~/projects/myapp main* ctx:73% sonnet-4.6 14:30 todos:3",
+    "output_example": "Opus 4.6 | Fixing auth bug | $1.23 47t 5f 15m | myproject ███████░░░ 68%",
+    "dependencies": "Reads bridge file from ecc-metrics-bridge.js PostToolUse hook. Both must be installed for full metrics display.",
     "usage": "Copy the statusLine object to your ~/.claude/settings.json"
   }
 }
diff --git a/hooks/hooks.json b/hooks/hooks.json
index ad709b3c..1b9420ac 100644
--- a/hooks/hooks.json
+++ b/hooks/hooks.json
@@ -219,6 +219,30 @@
         ],
         "description": "Capture tool use results for continuous learning",
         "id": "post:observe:continuous-learning"
+      },
+      {
+        "matcher": "*",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "node -e \"const p=require('path');const r=(()=>{var e=process.env.CLAUDE_PLUGIN_ROOT;if(e&&e.trim())return e.trim();var p=require('path'),f=require('fs'),h=require('os').homedir(),d=p.join(h,'.claude'),q=p.join('scripts','lib','utils.js');if(f.existsSync(p.join(d,q)))return d;for(var s of [[\\\"ecc\\\"],[\\\"ecc@ecc\\\"],[\\\"marketplaces\\\",\\\"ecc\\\"],[\\\"everything-claude-code\\\"],[\\\"everything-claude-code@everything-claude-code\\\"],[\\\"marketplaces\\\",\\\"everything-claude-code\\\"]]){var l=p.join(d,'plugins',...s);if(f.existsSync(p.join(l,q)))return l}try{for(var g of [\\\"ecc\\\",\\\"everything-claude-code\\\"]){var b=p.join(d,'plugins','cache',g);for(var o of f.readdirSync(b,{withFileTypes:true})){if(!o.isDirectory())continue;for(var v of f.readdirSync(p.join(b,o.name),{withFileTypes:true})){if(!v.isDirectory())continue;var c=p.join(b,o.name,v.name);if(f.existsSync(p.join(c,q)))return c}}}}catch(x){}return d})();const s=p.join(r,'scripts/hooks/plugin-hook-bootstrap.js');process.env.CLAUDE_PLUGIN_ROOT=r;process.argv.splice(1,0,s);require(s)\" node scripts/hooks/run-with-flags.js post:ecc-metrics-bridge scripts/hooks/ecc-metrics-bridge.js minimal,standard,strict",
+            "timeout": 10
+          }
+        ],
+        "description": "Maintain running session metrics aggregate for statusline and context monitor",
+        "id": "post:ecc-metrics-bridge"
+      },
+      {
+        "matcher": "*",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "node -e \"const p=require('path');const r=(()=>{var e=process.env.CLAUDE_PLUGIN_ROOT;if(e&&e.trim())return e.trim();var p=require('path'),f=require('fs'),h=require('os').homedir(),d=p.join(h,'.claude'),q=p.join('scripts','lib','utils.js');if(f.existsSync(p.join(d,q)))return d;for(var s of [[\\\"ecc\\\"],[\\\"ecc@ecc\\\"],[\\\"marketplaces\\\",\\\"ecc\\\"],[\\\"everything-claude-code\\\"],[\\\"everything-claude-code@everything-claude-code\\\"],[\\\"marketplaces\\\",\\\"everything-claude-code\\\"]]){var l=p.join(d,'plugins',...s);if(f.existsSync(p.join(l,q)))return l}try{for(var g of [\\\"ecc\\\",\\\"everything-claude-code\\\"]){var b=p.join(d,'plugins','cache',g);for(var o of f.readdirSync(b,{withFileTypes:true})){if(!o.isDirectory())continue;for(var v of f.readdirSync(p.join(b,o.name),{withFileTypes:true})){if(!v.isDirectory())continue;var c=p.join(b,o.name,v.name);if(f.existsSync(p.join(c,q)))return c}}}}catch(x){}return d})();const s=p.join(r,'scripts/hooks/plugin-hook-bootstrap.js');process.env.CLAUDE_PLUGIN_ROOT=r;process.argv.splice(1,0,s);require(s)\" node scripts/hooks/run-with-flags.js post:ecc-context-monitor scripts/hooks/ecc-context-monitor.js standard,strict",
+            "timeout": 10
+          }
+        ],
+        "description": "Inject agent warnings on context exhaustion, high cost, scope creep, or tool loops",
+        "id": "post:ecc-context-monitor"
       }
     ],
     "PostToolUseFailure": [
diff --git a/scripts/hooks/cost-tracker.js b/scripts/hooks/cost-tracker.js
index 817ff77a..a3f2f896 100755
--- a/scripts/hooks/cost-tracker.js
+++ b/scripts/hooks/cost-tracker.js
@@ -8,11 +8,9 @@
 'use strict';
 
 const path = require('path');
-const {
-  ensureDir,
-  appendFile,
-  getClaudeDir,
-} = require('../lib/utils');
+const { ensureDir, appendFile, getClaudeDir } = require('../lib/utils');
+const { estimateCost } = require('../lib/cost-estimate');
+const { sanitizeSessionId } = require('../lib/session-bridge');
 
 const MAX_STDIN = 1024 * 1024;
 let raw = '';
@@ -22,23 +20,6 @@ function toNumber(value) {
   return Number.isFinite(n) ? n : 0;
 }
 
-function estimateCost(model, inputTokens, outputTokens) {
-  // Approximate per-1M-token blended rates. Conservative defaults.
-  const table = {
-    'haiku': { in: 0.8, out: 4.0 },
-    'sonnet': { in: 3.0, out: 15.0 },
-    'opus': { in: 15.0, out: 75.0 },
-  };
-
-  const normalized = String(model || '').toLowerCase();
-  let rates = table.sonnet;
-  if (normalized.includes('haiku')) rates = table.haiku;
-  if (normalized.includes('opus')) rates = table.opus;
-
-  const cost = (inputTokens / 1_000_000) * rates.in + (outputTokens / 1_000_000) * rates.out;
-  return Math.round(cost * 1e6) / 1e6;
-}
-
 process.stdin.setEncoding('utf8');
 process.stdin.on('data', chunk => {
   if (raw.length < MAX_STDIN) {
@@ -55,7 +36,11 @@ process.stdin.on('end', () => {
     const outputTokens = toNumber(usage.output_tokens || usage.completion_tokens || 0);
 
     const model = String(input.model || input._cursor?.model || process.env.CLAUDE_MODEL || 'unknown');
-    const sessionId = String(process.env.ECC_SESSION_ID || process.env.CLAUDE_SESSION_ID || 'default');
+    const sessionId =
+      sanitizeSessionId(input.session_id) ||
+      sanitizeSessionId(process.env.ECC_SESSION_ID) ||
+      sanitizeSessionId(process.env.CLAUDE_SESSION_ID) ||
+      'default';
 
     const metricsDir = path.join(getClaudeDir(), 'metrics');
     ensureDir(metricsDir);
@@ -66,7 +51,7 @@ process.stdin.on('end', () => {
       model,
       input_tokens: inputTokens,
       output_tokens: outputTokens,
-      estimated_cost_usd: estimateCost(model, inputTokens, outputTokens),
+      estimated_cost_usd: estimateCost(model, inputTokens, outputTokens)
     };
 
     appendFile(path.join(metricsDir, 'costs.jsonl'), `${JSON.stringify(row)}\n`);
diff --git a/scripts/hooks/ecc-context-monitor.js b/scripts/hooks/ecc-context-monitor.js
new file mode 100644
index 00000000..a3c0be8b
--- /dev/null
+++ b/scripts/hooks/ecc-context-monitor.js
@@ -0,0 +1,242 @@
+#!/usr/bin/env node
+/**
+ * ECC Context Monitor — PostToolUse hook
+ *
+ * Reads bridge file from ecc-metrics-bridge.js and injects agent-facing
+ * warnings when thresholds are crossed: context exhaustion, high cost,
+ * scope creep, or tool loops.
+ */
+
+'use strict';
+
+const fs = require('fs');
+const os = require('os');
+const path = require('path');
+const { sanitizeSessionId, readBridge } = require('../lib/session-bridge');
+
+const CONTEXT_WARNING_PCT = 35;
+const CONTEXT_CRITICAL_PCT = 25;
+const COST_NOTICE_USD = 5;
+const COST_WARNING_USD = 10;
+const COST_CRITICAL_USD = 50;
+const FILES_WARNING_COUNT = 20;
+const LOOP_THRESHOLD = 3;
+const STALE_SECONDS = 60;
+const DEBOUNCE_CALLS = 5;
+
+/**
+ * Get debounce state file path.
+ * @param {string} sessionId
+ * @returns {string}
+ */
+function getWarnPath(sessionId) {
+  return path.join(os.tmpdir(), `ecc-ctx-warn-${sessionId}.json`);
+}
+
+/**
+ * Read debounce state.
+ * @param {string} sessionId
+ * @returns {object}
+ */
+function readWarnState(sessionId) {
+  try {
+    return JSON.parse(fs.readFileSync(getWarnPath(sessionId), 'utf8'));
+  } catch {
+    return { callsSinceWarn: 0, lastSeverity: null };
+  }
+}
+
+/**
+ * Write debounce state.
+ * @param {string} sessionId
+ * @param {object} state
+ */
+function writeWarnState(sessionId, state) {
+  const target = getWarnPath(sessionId);
+  const tmp = `${target}.tmp`;
+  fs.writeFileSync(tmp, JSON.stringify(state), 'utf8');
+  fs.renameSync(tmp, target);
+}
+
+/**
+ * Detect tool loops from recent_tools ring buffer.
+ * @param {Array} recentTools
+ * @returns {{detected: boolean, tool: string, count: number}}
+ */
+function detectLoop(recentTools) {
+  if (!Array.isArray(recentTools) || recentTools.length < LOOP_THRESHOLD) {
+    return { detected: false, tool: '', count: 0 };
+  }
+  const counts = {};
+  for (const entry of recentTools) {
+    const key = `${entry.tool}:${entry.hash}`;
+    counts[key] = (counts[key] || 0) + 1;
+  }
+  for (const [key, count] of Object.entries(counts)) {
+    if (count >= LOOP_THRESHOLD) {
+      return { detected: true, tool: key.split(':')[0], count };
+    }
+  }
+  return { detected: false, tool: '', count: 0 };
+}
+
+/**
+ * Evaluate all warning conditions against bridge data.
+ * Returns array of {severity, type, message} sorted by severity desc.
+ */
+function evaluateConditions(bridge) {
+  const warnings = [];
+  const remaining = bridge.context_remaining_pct;
+
+  // Context warnings (skip if no context data)
+  if (remaining !== null && remaining !== undefined) {
+    if (remaining <= CONTEXT_CRITICAL_PCT) {
+      warnings.push({
+        severity: 3,
+        type: 'context',
+        message:
+          `CONTEXT CRITICAL: ${remaining}% remaining. Context nearly exhausted. ` +
+          'Inform the user that context is low and ask how they want to proceed. ' +
+          'Do NOT autonomously save state or write handoff files unless the user asks.'
+      });
+    } else if (remaining <= CONTEXT_WARNING_PCT) {
+      warnings.push({
+        severity: 2,
+        type: 'context',
+        message: `CONTEXT WARNING: ${remaining}% remaining. ` + 'Be aware that context is getting limited. Avoid starting new complex work.'
+      });
+    }
+  }
+
+  // Cost warnings
+  const cost = bridge.total_cost_usd || 0;
+  if (cost > COST_CRITICAL_USD) {
+    warnings.push({
+      severity: 3,
+      type: 'cost',
+      message: `COST CRITICAL: Session cost is $${cost.toFixed(2)}. ` + 'Stop and inform the user about high cost before continuing.'
+    });
+  } else if (cost > COST_WARNING_USD) {
+    warnings.push({
+      severity: 2,
+      type: 'cost',
+      message: `COST WARNING: Session cost is $${cost.toFixed(2)}. ` + 'Review whether the current approach justifies the expense.'
+    });
+  } else if (cost > COST_NOTICE_USD) {
+    warnings.push({
+      severity: 1,
+      type: 'cost',
+      message: `COST NOTICE: Session cost is $${cost.toFixed(2)}. ` + 'Consider whether the current approach is efficient.'
+    });
+  }
+
+  // File scope warning
+  const fileCount = bridge.files_modified_count || 0;
+  if (fileCount > FILES_WARNING_COUNT) {
+    warnings.push({
+      severity: 2,
+      type: 'scope',
+      message: `SCOPE WARNING: ${fileCount} files modified this session. ` + 'Consider whether changes are too scattered.'
+    });
+  }
+
+  // Loop detection
+  const loop = detectLoop(bridge.recent_tools);
+  if (loop.detected) {
+    warnings.push({
+      severity: 2,
+      type: 'loop',
+      message: `LOOP WARNING: Tool '${loop.tool}' called ${loop.count} times ` + 'with same parameters in last 5 calls. This may indicate a stuck loop.'
+    });
+  }
+
+  return warnings.sort((a, b) => b.severity - a.severity);
+}
+
+/**
+ * Map numeric severity to label.
+ */
+function severityLabel(n) {
+  if (n >= 3) return 'critical';
+  if (n >= 2) return 'warning';
+  return 'notice';
+}
+
+/**
+ * @param {string} rawInput - Raw JSON string from stdin
+ * @returns {string} JSON output with additionalContext or pass-through
+ */
+function run(rawInput) {
+  try {
+    const input = rawInput.trim() ? JSON.parse(rawInput) : {};
+
+    const sessionId = sanitizeSessionId(input.session_id) || sanitizeSessionId(process.env.ECC_SESSION_ID) || sanitizeSessionId(process.env.CLAUDE_SESSION_ID);
+
+    if (!sessionId) return rawInput;
+
+    const bridge = readBridge(sessionId);
+    if (!bridge) return rawInput;
+
+    // Stale check for context warnings
+    const now = Math.floor(Date.now() / 1000);
+    const lastTs = bridge.last_timestamp ? Math.floor(new Date(bridge.last_timestamp).getTime() / 1000) : 0;
+    const isStale = lastTs > 0 && now - lastTs > STALE_SECONDS;
+
+    // If bridge is stale, null out context data (still check cost/scope/loop)
+    const evalBridge = isStale ? { ...bridge, context_remaining_pct: null } : bridge;
+
+    const warnings = evaluateConditions(evalBridge);
+    if (warnings.length === 0) return rawInput;
+
+    // Debounce logic
+    const warnState = readWarnState(sessionId);
+    warnState.callsSinceWarn = (warnState.callsSinceWarn || 0) + 1;
+
+    const topSeverity = severityLabel(warnings[0].severity);
+    const severityEscalated = topSeverity === 'critical' && warnState.lastSeverity !== 'critical';
+
+    const isFirst = !warnState.lastSeverity;
+    if (!isFirst && warnState.callsSinceWarn < DEBOUNCE_CALLS && !severityEscalated) {
+      writeWarnState(sessionId, warnState);
+      return rawInput;
+    }
+
+    // Reset debounce, emit warning
+    warnState.callsSinceWarn = 0;
+    warnState.lastSeverity = topSeverity;
+    writeWarnState(sessionId, warnState);
+
+    // Combine top 2 warnings
+    const message = warnings
+      .slice(0, 2)
+      .map(w => w.message)
+      .join('\n');
+
+    const output = {
+      hookSpecificOutput: {
+        hookEventName: 'PostToolUse',
+        additionalContext: message
+      }
+    };
+
+    return JSON.stringify(output);
+  } catch {
+    // Never block tool execution
+    return rawInput;
+  }
+}
+
+if (require.main === module) {
+  let data = '';
+  const MAX_STDIN = 1024 * 1024;
+  process.stdin.setEncoding('utf8');
+  process.stdin.on('data', chunk => {
+    if (data.length < MAX_STDIN) data += chunk.substring(0, MAX_STDIN - data.length);
+  });
+  process.stdin.on('end', () => {
+    process.stdout.write(run(data));
+    process.exit(0);
+  });
+}
+
+module.exports = { run, evaluateConditions, detectLoop, severityLabel };
diff --git a/scripts/hooks/ecc-metrics-bridge.js b/scripts/hooks/ecc-metrics-bridge.js
new file mode 100644
index 00000000..d7f97cfa
--- /dev/null
+++ b/scripts/hooks/ecc-metrics-bridge.js
@@ -0,0 +1,198 @@
+#!/usr/bin/env node
+/**
+ * ECC Metrics Bridge — PostToolUse hook
+ *
+ * Maintains a running session aggregate in /tmp/ecc-metrics-{session}.json.
+ * This bridge file is read by ecc-statusline.js and ecc-context-monitor.js,
+ * avoiding the need to scan large JSONL logs on every invocation.
+ */
+
+'use strict';
+
+const crypto = require('crypto');
+const fs = require('fs');
+const path = require('path');
+const { sanitizeSessionId, readBridge, writeBridgeAtomic } = require('../lib/session-bridge');
+const { getClaudeDir } = require('../lib/utils');
+
+const MAX_STDIN = 1024 * 1024;
+const MAX_FILES_TRACKED = 200;
+const RECENT_TOOLS_SIZE = 5;
+const HASH_INPUT_LIMIT = 2048;
+
+function toNumber(value) {
+  const n = Number(value);
+  return Number.isFinite(n) ? n : 0;
+}
+
+function stableStringify(value, depth = 0) {
+  if (depth > 4) return '[depth-limit]';
+  if (value === null || typeof value !== 'object') return JSON.stringify(value);
+  if (Array.isArray(value)) {
+    return `[${value.map(item => stableStringify(item, depth + 1)).join(',')}]`;
+  }
+  return `{${Object.keys(value)
+    .sort()
+    .map(key => `${JSON.stringify(key)}:${stableStringify(value[key], depth + 1)}`)
+    .join(',')}}`;
+}
+
+/**
+ * Hash tool call for loop detection.
+ * Uses tool name + a key parameter when available, otherwise a stable input digest.
+ */
+function hashToolCall(toolName, toolInput) {
+  const name = String(toolName || '');
+  let key = '';
+  if (name === 'Bash') {
+    key = String(toolInput?.command || '').slice(0, 160);
+  } else if (toolInput?.file_path) {
+    key = String(toolInput.file_path);
+  } else {
+    key = stableStringify(toolInput || {}).slice(0, HASH_INPUT_LIMIT);
+  }
+  return crypto.createHash('sha256').update(`${name}:${key}`).digest('hex').slice(0, 8);
+}
+
+/**
+ * Extract modified file paths from tool input.
+ */
+function extractFilePaths(toolName, toolInput) {
+  const paths = [];
+  if (!toolInput || typeof toolInput !== 'object') return paths;
+
+  const fp = toolInput.file_path;
+  if (fp && typeof fp === 'string') paths.push(fp);
+
+  const edits = toolInput.edits;
+  if (Array.isArray(edits)) {
+    for (const edit of edits) {
+      if (edit?.file_path && typeof edit.file_path === 'string') {
+        paths.push(edit.file_path);
+      }
+    }
+  }
+
+  return paths;
+}
+
+/**
+ * Read cumulative cost for a session from the tail of costs.jsonl.
+ * Reads last 8KB to avoid scanning entire file.
+ */
+function readSessionCost(sessionId) {
+  try {
+    const costsPath = path.join(getClaudeDir(), 'metrics', 'costs.jsonl');
+    const stat = fs.statSync(costsPath);
+    const readSize = Math.min(stat.size, 8192);
+    const fd = fs.openSync(costsPath, 'r');
+    try {
+      const buf = Buffer.alloc(readSize);
+      fs.readSync(fd, buf, 0, readSize, Math.max(0, stat.size - readSize));
+      const lines = buf.toString('utf8').split('\n').filter(Boolean);
+
+      let totalCost = 0;
+      let totalIn = 0;
+      let totalOut = 0;
+      for (const line of lines) {
+        try {
+          const row = JSON.parse(line);
+          if (row.session_id === sessionId) {
+            totalCost += toNumber(row.estimated_cost_usd);
+            totalIn += toNumber(row.input_tokens);
+            totalOut += toNumber(row.output_tokens);
+          }
+        } catch {
+          /* skip malformed lines */
+        }
+      }
+      return { totalCost, totalIn, totalOut };
+    } finally {
+      fs.closeSync(fd);
+    }
+  } catch {
+    return { totalCost: 0, totalIn: 0, totalOut: 0 };
+  }
+}
+
+/**
+ * @param {string} rawInput - Raw JSON string from stdin
+ * @returns {string} Pass-through
+ */
+function run(rawInput) {
+  try {
+    const input = rawInput.trim() ? JSON.parse(rawInput) : {};
+    const toolName = String(input.tool_name || '');
+    const toolInput = input.tool_input || {};
+
+    const sessionId = sanitizeSessionId(input.session_id) || sanitizeSessionId(process.env.ECC_SESSION_ID) || sanitizeSessionId(process.env.CLAUDE_SESSION_ID);
+
+    if (!sessionId) return rawInput;
+
+    const now = new Date().toISOString();
+    const bridge = readBridge(sessionId) || {
+      session_id: sessionId,
+      total_cost_usd: 0,
+      total_input_tokens: 0,
+      total_output_tokens: 0,
+      tool_count: 0,
+      files_modified_count: 0,
+      files_modified: [],
+      recent_tools: [],
+      first_timestamp: now,
+      last_timestamp: now,
+      context_remaining_pct: null
+    };
+
+    // Increment tool count
+    bridge.tool_count = (bridge.tool_count || 0) + 1;
+    bridge.last_timestamp = now;
+    if (!bridge.first_timestamp) bridge.first_timestamp = now;
+
+    // Track modified files (Write/Edit/MultiEdit only)
+    const isWriteOp = /^(Write|Edit|MultiEdit)$/i.test(toolName);
+    if (isWriteOp) {
+      const newPaths = extractFilePaths(toolName, toolInput);
+      const existing = new Set(bridge.files_modified || []);
+      for (const p of newPaths) {
+        if (existing.size < MAX_FILES_TRACKED && !existing.has(p)) {
+          existing.add(p);
+        }
+      }
+      bridge.files_modified = [...existing];
+      bridge.files_modified_count = existing.size;
+    }
+
+    // Ring buffer for loop detection
+    const recent = bridge.recent_tools || [];
+    recent.push({ tool: toolName, hash: hashToolCall(toolName, toolInput) });
+    if (recent.length > RECENT_TOOLS_SIZE) recent.shift();
+    bridge.recent_tools = recent;
+
+    // Update cost from costs.jsonl tail
+    const costs = readSessionCost(sessionId);
+    bridge.total_cost_usd = Math.round(costs.totalCost * 1e6) / 1e6;
+    bridge.total_input_tokens = costs.totalIn;
+    bridge.total_output_tokens = costs.totalOut;
+
+    writeBridgeAtomic(sessionId, bridge);
+  } catch {
+    // Never block tool execution
+  }
+
+  return rawInput;
+}
+
+if (require.main === module) {
+  let data = '';
+  process.stdin.setEncoding('utf8');
+  process.stdin.on('data', chunk => {
+    if (data.length < MAX_STDIN) data += chunk.substring(0, MAX_STDIN - data.length);
+  });
+  process.stdin.on('end', () => {
+    process.stdout.write(run(data));
+    process.exit(0);
+  });
+}
+
+module.exports = { run, hashToolCall, extractFilePaths, readSessionCost, stableStringify };
diff --git a/scripts/hooks/ecc-statusline.js b/scripts/hooks/ecc-statusline.js
new file mode 100644
index 00000000..825b8f4d
--- /dev/null
+++ b/scripts/hooks/ecc-statusline.js
@@ -0,0 +1,168 @@
+#!/usr/bin/env node
+/**
+ * ECC Statusline — statusLine command
+ *
+ * Displays: model | task | $cost Nt Nf Nm | dir ██░░ N%
+ *
+ * Registered in settings.json under "statusLine", not in hooks.json.
+ * Reads bridge file from ecc-metrics-bridge.js and stdin from Claude Code runtime.
+ */
+
+'use strict';
+
+const fs = require('fs');
+const os = require('os');
+const path = require('path');
+const { sanitizeSessionId, readBridge, writeBridgeAtomic } = require('../lib/session-bridge');
+
+const AUTO_COMPACT_BUFFER_PCT = 16.5;
+const MAX_STDIN = 1024 * 1024;
+
+/**
+ * Format duration from ISO timestamp to now.
+ * @param {string} isoTimestamp
+ * @returns {string} e.g. "5s", "12m", "1h23m"
+ */
+function formatDuration(isoTimestamp) {
+  if (!isoTimestamp) return '?';
+  const elapsed = Math.floor((Date.now() - new Date(isoTimestamp).getTime()) / 1000);
+  if (elapsed < 0) return '?';
+  if (elapsed < 60) return `${elapsed}s`;
+  const mins = Math.floor(elapsed / 60);
+  if (mins < 60) return `${mins}m`;
+  const hours = Math.floor(mins / 60);
+  const remMins = mins % 60;
+  return remMins > 0 ? `${hours}h${remMins}m` : `${hours}h`;
+}
+
+/**
+ * Build context progress bar with ANSI colors.
+ * @param {number} remaining - Raw remaining percentage from Claude Code
+ * @returns {string} Colored bar string
+ */
+function buildContextBar(remaining) {
+  if (remaining === null || remaining === undefined) return '';
+
+  const usableRemaining = Math.max(0, ((remaining - AUTO_COMPACT_BUFFER_PCT) / (100 - AUTO_COMPACT_BUFFER_PCT)) * 100);
+  const used = Math.max(0, Math.min(100, Math.round(100 - usableRemaining)));
+
+  const filled = Math.floor(used / 10);
+  const bar = '\u2588'.repeat(filled) + '\u2591'.repeat(10 - filled);
+
+  if (used < 50) return ` \x1b[32m${bar} ${used}%\x1b[0m`;
+  if (used < 65) return ` \x1b[33m${bar} ${used}%\x1b[0m`;
+  if (used < 80) return ` \x1b[38;5;208m${bar} ${used}%\x1b[0m`;
+  return ` \x1b[5;31m${bar} ${used}%\x1b[0m`;
+}
+
+/**
+ * Read current in-progress task from todos directory.
+ * @param {string} sessionId
+ * @returns {string} Task activeForm text or empty string
+ */
+function readCurrentTask(sessionId) {
+  try {
+    const safeSessionId = sanitizeSessionId(sessionId);
+    if (!safeSessionId) return '';
+
+    const claudeDir = process.env.CLAUDE_CONFIG_DIR || path.join(os.homedir(), '.claude');
+    const todosDir = path.join(claudeDir, 'todos');
+    if (!fs.existsSync(todosDir)) return '';
+
+    const files = fs
+      .readdirSync(todosDir)
+      .filter(f => f.startsWith(safeSessionId) && f.includes('-agent-') && f.endsWith('.json'))
+      .map(f => ({ name: f, mtime: fs.statSync(path.join(todosDir, f)).mtime }))
+      .sort((a, b) => b.mtime - a.mtime);
+
+    if (files.length === 0) return '';
+
+    const todos = JSON.parse(fs.readFileSync(path.join(todosDir, files[0].name), 'utf8'));
+    const inProgress = todos.find(t => t.status === 'in_progress');
+    return inProgress?.activeForm || '';
+  } catch {
+    return '';
+  }
+}
+
+function runStatusline() {
+  let input = '';
+  const stdinTimeout = setTimeout(() => process.exit(0), 3000);
+  process.stdin.setEncoding('utf8');
+  process.stdin.on('data', chunk => {
+    if (input.length < MAX_STDIN) {
+      input += chunk.substring(0, MAX_STDIN - input.length);
+    }
+  });
+  process.stdin.on('end', () => {
+    clearTimeout(stdinTimeout);
+    try {
+      const data = JSON.parse(input);
+      const model = data.model?.display_name || 'Claude';
+      const dir = data.workspace?.current_dir || process.cwd();
+      const session = data.session_id || '';
+      const remaining = data.context_window?.remaining_percentage;
+
+      const sessionId = sanitizeSessionId(session);
+      const bridge = sessionId ? readBridge(sessionId) : null;
+
+      // Write context % back to bridge for context-monitor
+      if (sessionId && bridge && remaining !== null && remaining !== undefined) {
+        bridge.context_remaining_pct = remaining;
+        try {
+          writeBridgeAtomic(sessionId, bridge);
+        } catch {
+          /* best effort */
+        }
+      }
+
+      // Current task
+      const task = sessionId ? readCurrentTask(sessionId) : '';
+
+      // Metrics from bridge
+      let metricsStr = '';
+      if (bridge) {
+        const parts = [];
+        if (bridge.total_cost_usd > 0) {
+          parts.push(`$${bridge.total_cost_usd.toFixed(2)}`);
+        }
+        if (bridge.tool_count > 0) {
+          parts.push(`${bridge.tool_count}t`);
+        }
+        if (bridge.files_modified_count > 0) {
+          parts.push(`${bridge.files_modified_count}f`);
+        }
+        const dur = formatDuration(bridge.first_timestamp);
+        if (dur !== '?') {
+          parts.push(dur);
+        }
+        if (parts.length > 0) {
+          metricsStr = `\x1b[36m${parts.join(' ')}\x1b[0m`;
+        }
+      }
+
+      // Context bar
+      const ctx = buildContextBar(remaining);
+
+      // Build output
+      const dirname = path.basename(dir);
+      const segments = [`\x1b[2m${model}\x1b[0m`];
+
+      if (task) {
+        segments.push(`\x1b[1m${task}\x1b[0m`);
+      }
+      if (metricsStr) {
+        segments.push(metricsStr);
+      }
+      segments.push(`\x1b[2m${dirname}\x1b[0m`);
+
+      process.stdout.write(segments.join(' \x1b[2m\u2502\x1b[0m ') + ctx);
+    } catch {
+      // Silent fail
+    }
+  });
+}
+
+module.exports = { formatDuration, buildContextBar, readCurrentTask, MAX_STDIN };
+
+if (require.main === module) runStatusline();
diff --git a/scripts/lib/cost-estimate.js b/scripts/lib/cost-estimate.js
new file mode 100644
index 00000000..a1651a8c
--- /dev/null
+++ b/scripts/lib/cost-estimate.js
@@ -0,0 +1,32 @@
+'use strict';
+
+/**
+ * Shared cost estimation for ECC hooks.
+ *
+ * Approximate per-1M-token blended rates (conservative defaults).
+ */
+
+const RATE_TABLE = {
+  haiku: { in: 0.8, out: 4.0 },
+  sonnet: { in: 3.0, out: 15.0 },
+  opus: { in: 15.0, out: 75.0 }
+};
+
+/**
+ * Estimate USD cost from token counts.
+ * @param {string} model - Model name (may contain "haiku", "sonnet", or "opus")
+ * @param {number} inputTokens
+ * @param {number} outputTokens
+ * @returns {number} Estimated cost in USD (rounded to 6 decimal places)
+ */
+function estimateCost(model, inputTokens, outputTokens) {
+  const normalized = String(model || '').toLowerCase();
+  let rates = RATE_TABLE.sonnet;
+  if (normalized.includes('haiku')) rates = RATE_TABLE.haiku;
+  if (normalized.includes('opus')) rates = RATE_TABLE.opus;
+
+  const cost = (inputTokens / 1_000_000) * rates.in + (outputTokens / 1_000_000) * rates.out;
+  return Math.round(cost * 1e6) / 1e6;
+}
+
+module.exports = { estimateCost, RATE_TABLE };
diff --git a/scripts/lib/session-bridge.js b/scripts/lib/session-bridge.js
new file mode 100644
index 00000000..aceae9cb
--- /dev/null
+++ b/scripts/lib/session-bridge.js
@@ -0,0 +1,81 @@
+'use strict';
+
+/**
+ * Shared session bridge utilities for ECC hooks.
+ *
+ * The bridge file is a small JSON aggregate in /tmp that allows
+ * statusline, metrics-bridge, and context-monitor to share state
+ * without scanning large JSONL logs on every invocation.
+ */
+
+const fs = require('fs');
+const os = require('os');
+const path = require('path');
+
+const MAX_SESSION_ID_LENGTH = 64;
+
+/**
+ * Sanitize a session ID for safe use in file paths.
+ * Rejects path traversal, strips unsafe chars, limits length.
+ * @param {string} raw
+ * @returns {string|null} Safe session ID or null if invalid
+ */
+function sanitizeSessionId(raw) {
+  if (!raw || typeof raw !== 'string') return null;
+  if (/[/\\]|\.\./.test(raw)) return null;
+  const safe = raw.replace(/[^a-zA-Z0-9_-]/g, '_').slice(0, MAX_SESSION_ID_LENGTH);
+  return safe || null;
+}
+
+/**
+ * Get the bridge file path for a session.
+ * @param {string} sessionId - Already-sanitized session ID
+ * @returns {string}
+ */
+function getBridgePath(sessionId) {
+  return path.join(os.tmpdir(), `ecc-metrics-${sessionId}.json`);
+}
+
+/**
+ * Read bridge data. Returns null on any error.
+ * @param {string} sessionId - Already-sanitized session ID
+ * @returns {object|null}
+ */
+function readBridge(sessionId) {
+  try {
+    const raw = fs.readFileSync(getBridgePath(sessionId), 'utf8');
+    return JSON.parse(raw);
+  } catch {
+    return null;
+  }
+}
+
+/**
+ * Write bridge data atomically (write .tmp then rename).
+ * @param {string} sessionId - Already-sanitized session ID
+ * @param {object} data
+ */
+function writeBridgeAtomic(sessionId, data) {
+  const target = getBridgePath(sessionId);
+  const tmp = `${target}.tmp`;
+  fs.writeFileSync(tmp, JSON.stringify(data), 'utf8');
+  fs.renameSync(tmp, target);
+}
+
+/**
+ * Resolve session ID from environment variables.
+ * @returns {string|null} Sanitized session ID or null
+ */
+function resolveSessionId() {
+  const raw = process.env.ECC_SESSION_ID || process.env.CLAUDE_SESSION_ID || '';
+  return sanitizeSessionId(raw);
+}
+
+module.exports = {
+  sanitizeSessionId,
+  getBridgePath,
+  readBridge,
+  writeBridgeAtomic,
+  resolveSessionId,
+  MAX_SESSION_ID_LENGTH
+};
diff --git a/tests/hooks/cost-tracker.test.js b/tests/hooks/cost-tracker.test.js
index ee834465..4a1f6fef 100644
--- a/tests/hooks/cost-tracker.test.js
+++ b/tests/hooks/cost-tracker.test.js
@@ -152,6 +152,28 @@ function runTests() {
     fs.rmSync(tmpHome, { recursive: true, force: true });
   }) ? passed++ : failed++);
 
+  // 7. Uses sanitized hook input session_id when environment session IDs are absent
+  (test('uses input session_id for session correlation when env vars are absent', () => {
+    const tmpHome = makeTempDir();
+    const input = {
+      session_id: 'hook-session-abc',
+      model: 'claude-sonnet-4-20250514',
+      usage: { input_tokens: 120, output_tokens: 30 },
+    };
+    const result = runScript(input, {
+      ...withTempHome(tmpHome),
+      ECC_SESSION_ID: '',
+      CLAUDE_SESSION_ID: '',
+    });
+    assert.strictEqual(result.code, 0, `Expected exit code 0, got ${result.code}`);
+
+    const metricsFile = path.join(tmpHome, '.claude', 'metrics', 'costs.jsonl');
+    const row = JSON.parse(fs.readFileSync(metricsFile, 'utf8').trim());
+    assert.strictEqual(row.session_id, 'hook-session-abc', 'Expected input session_id to be recorded');
+
+    fs.rmSync(tmpHome, { recursive: true, force: true });
+  }) ? passed++ : failed++);
+
   console.log(`\nResults: Passed: ${passed}, Failed: ${failed}`);
   process.exit(failed > 0 ? 1 : 0);
 }
diff --git a/tests/hooks/ecc-context-monitor.test.js b/tests/hooks/ecc-context-monitor.test.js
new file mode 100644
index 00000000..bbecc4ed
--- /dev/null
+++ b/tests/hooks/ecc-context-monitor.test.js
@@ -0,0 +1,238 @@
+/**
+ * Tests for scripts/hooks/ecc-context-monitor.js
+ *
+ * Run with: node tests/hooks/ecc-context-monitor.test.js
+ */
+
+const assert = require('assert');
+
+const { run, evaluateConditions, detectLoop, severityLabel } = require('../../scripts/hooks/ecc-context-monitor');
+
+// Test helper
+function test(name, fn) {
+  try {
+    fn();
+    console.log(`  \u2713 ${name}`);
+    return true;
+  } catch (err) {
+    console.log(`  \u2717 ${name}`);
+    console.log(`    Error: ${err.message}`);
+    return false;
+  }
+}
+
+function runTests() {
+  console.log('\n=== Testing ecc-context-monitor.js ===\n');
+
+  let passed = 0;
+  let failed = 0;
+
+  // evaluateConditions — context warnings
+  console.log('evaluateConditions (context):');
+
+  if (
+    test('remaining 20% triggers CRITICAL context warning', () => {
+      const warnings = evaluateConditions({ context_remaining_pct: 20 });
+      const ctx = warnings.find(w => w.type === 'context');
+      assert.ok(ctx, 'Expected a context warning');
+      assert.strictEqual(ctx.severity, 3);
+      assert.ok(ctx.message.includes('CRITICAL'), 'Message should contain CRITICAL');
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('remaining 30% triggers WARNING context warning', () => {
+      const warnings = evaluateConditions({ context_remaining_pct: 30 });
+      const ctx = warnings.find(w => w.type === 'context');
+      assert.ok(ctx, 'Expected a context warning');
+      assert.strictEqual(ctx.severity, 2);
+      assert.ok(ctx.message.includes('WARNING'), 'Message should contain WARNING');
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('remaining 50% triggers no context warning', () => {
+      const warnings = evaluateConditions({ context_remaining_pct: 50 });
+      const ctx = warnings.find(w => w.type === 'context');
+      assert.strictEqual(ctx, undefined);
+    })
+  )
+    passed++;
+  else failed++;
+
+  // evaluateConditions — cost warnings
+  console.log('\nevaluateConditions (cost):');
+
+  if (
+    test('cost $55 triggers CRITICAL cost warning', () => {
+      const warnings = evaluateConditions({ total_cost_usd: 55 });
+      const cost = warnings.find(w => w.type === 'cost');
+      assert.ok(cost, 'Expected a cost warning');
+      assert.strictEqual(cost.severity, 3);
+      assert.ok(cost.message.includes('CRITICAL'), 'Message should contain CRITICAL');
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('cost $12 triggers WARNING cost warning', () => {
+      const warnings = evaluateConditions({ total_cost_usd: 12 });
+      const cost = warnings.find(w => w.type === 'cost');
+      assert.ok(cost, 'Expected a cost warning');
+      assert.strictEqual(cost.severity, 2);
+      assert.ok(cost.message.includes('WARNING'), 'Message should contain WARNING');
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('cost $6 triggers NOTICE cost warning', () => {
+      const warnings = evaluateConditions({ total_cost_usd: 6 });
+      const cost = warnings.find(w => w.type === 'cost');
+      assert.ok(cost, 'Expected a cost warning');
+      assert.strictEqual(cost.severity, 1);
+      assert.ok(cost.message.includes('NOTICE'), 'Message should contain NOTICE');
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('cost $2 triggers no cost warning', () => {
+      const warnings = evaluateConditions({ total_cost_usd: 2 });
+      const cost = warnings.find(w => w.type === 'cost');
+      assert.strictEqual(cost, undefined);
+    })
+  )
+    passed++;
+  else failed++;
+
+  // evaluateConditions — scope warnings
+  console.log('\nevaluateConditions (scope):');
+
+  if (
+    test('25 files triggers scope WARNING', () => {
+      const warnings = evaluateConditions({ files_modified_count: 25 });
+      const scope = warnings.find(w => w.type === 'scope');
+      assert.ok(scope, 'Expected a scope warning');
+      assert.strictEqual(scope.severity, 2);
+      assert.ok(scope.message.includes('SCOPE'), 'Message should contain SCOPE');
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('10 files triggers no scope warning', () => {
+      const warnings = evaluateConditions({ files_modified_count: 10 });
+      const scope = warnings.find(w => w.type === 'scope');
+      assert.strictEqual(scope, undefined);
+    })
+  )
+    passed++;
+  else failed++;
+
+  // detectLoop tests
+  console.log('\ndetectLoop:');
+
+  if (
+    test('3 identical entries returns detected true', () => {
+      const entries = [
+        { tool: 'Bash', hash: 'aabbccdd' },
+        { tool: 'Bash', hash: 'aabbccdd' },
+        { tool: 'Bash', hash: 'aabbccdd' }
+      ];
+      const result = detectLoop(entries);
+      assert.strictEqual(result.detected, true);
+      assert.strictEqual(result.tool, 'Bash');
+      assert.ok(result.count >= 3);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('all different entries returns detected false', () => {
+      const entries = [
+        { tool: 'Bash', hash: '11111111' },
+        { tool: 'Edit', hash: '22222222' },
+        { tool: 'Write', hash: '33333333' }
+      ];
+      const result = detectLoop(entries);
+      assert.strictEqual(result.detected, false);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('empty array returns detected false', () => {
+      const result = detectLoop([]);
+      assert.strictEqual(result.detected, false);
+    })
+  )
+    passed++;
+  else failed++;
+
+  // severityLabel tests
+  console.log('\nseverityLabel:');
+
+  if (
+    test('severity 3 returns critical', () => {
+      assert.strictEqual(severityLabel(3), 'critical');
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('severity 2 returns warning', () => {
+      assert.strictEqual(severityLabel(2), 'warning');
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('severity 1 returns notice', () => {
+      assert.strictEqual(severityLabel(1), 'notice');
+    })
+  )
+    passed++;
+  else failed++;
+
+  // run tests
+  console.log('\nrun:');
+
+  if (
+    test('empty input returns input unchanged', () => {
+      const result = run('');
+      assert.strictEqual(result, '');
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('input without session_id returns input unchanged', () => {
+      const input = JSON.stringify({ tool_name: 'Bash' });
+      const result = run(input);
+      assert.strictEqual(result, input);
+    })
+  )
+    passed++;
+  else failed++;
+
+  // Summary
+  console.log(`\nResults: ${passed} passed, ${failed} failed\n`);
+  return { passed, failed };
+}
+
+const { failed } = runTests();
+process.exit(failed > 0 ? 1 : 0);
diff --git a/tests/hooks/ecc-metrics-bridge.test.js b/tests/hooks/ecc-metrics-bridge.test.js
new file mode 100644
index 00000000..ac7631ca
--- /dev/null
+++ b/tests/hooks/ecc-metrics-bridge.test.js
@@ -0,0 +1,219 @@
+/**
+ * Tests for scripts/hooks/ecc-metrics-bridge.js
+ *
+ * Run with: node tests/hooks/ecc-metrics-bridge.test.js
+ */
+
+const assert = require('assert');
+const fs = require('fs');
+const os = require('os');
+const path = require('path');
+
+const { run, hashToolCall, extractFilePaths, readSessionCost } = require('../../scripts/hooks/ecc-metrics-bridge');
+
+// Test helper
+function test(name, fn) {
+  try {
+    fn();
+    console.log(`  \u2713 ${name}`);
+    return true;
+  } catch (err) {
+    console.log(`  \u2717 ${name}`);
+    console.log(`    Error: ${err.message}`);
+    return false;
+  }
+}
+
+function makeTempHome() {
+  return fs.mkdtempSync(path.join(os.tmpdir(), 'ecc-metrics-bridge-test-'));
+}
+
+function runTests() {
+  console.log('\n=== Testing ecc-metrics-bridge.js ===\n');
+
+  let passed = 0;
+  let failed = 0;
+
+  // hashToolCall tests
+  console.log('hashToolCall:');
+
+  if (
+    test('returns 8-char hex string', () => {
+      const hash = hashToolCall('Bash', { command: 'ls' });
+      assert.strictEqual(hash.length, 8);
+      assert.ok(/^[0-9a-f]{8}$/.test(hash), `Expected hex, got: ${hash}`);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('different Bash commands produce different hashes', () => {
+      const h1 = hashToolCall('Bash', { command: 'ls' });
+      const h2 = hashToolCall('Bash', { command: 'pwd' });
+      assert.notStrictEqual(h1, h2);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('different Edit file_paths produce different hashes', () => {
+      const h1 = hashToolCall('Edit', { file_path: 'a.js' });
+      const h2 = hashToolCall('Edit', { file_path: 'b.js' });
+      assert.notStrictEqual(h1, h2);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('same inputs produce same hash (deterministic)', () => {
+      const h1 = hashToolCall('Write', { file_path: 'x.txt' });
+      const h2 = hashToolCall('Write', { file_path: 'x.txt' });
+      assert.strictEqual(h1, h2);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('non-file tools hash by stable input to avoid false loop collisions', () => {
+      const h1 = hashToolCall('Glob', { pattern: '**/*.js', path: '/repo/a' });
+      const h2 = hashToolCall('Glob', { pattern: '**/*.md', path: '/repo/a' });
+      const h3 = hashToolCall('Glob', { path: '/repo/a', pattern: '**/*.js' });
+      assert.notStrictEqual(h1, h2);
+      assert.strictEqual(h1, h3);
+    })
+  )
+    passed++;
+  else failed++;
+
+  // extractFilePaths tests
+  console.log('\nextractFilePaths:');
+
+  if (
+    test('Edit with file_path returns [file_path]', () => {
+      const paths = extractFilePaths('Edit', { file_path: 'a.js' });
+      assert.deepStrictEqual(paths, ['a.js']);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('MultiEdit with edits array returns all file_paths', () => {
+      const paths = extractFilePaths('MultiEdit', {
+        edits: [{ file_path: 'a.js' }, { file_path: 'b.js' }]
+      });
+      assert.deepStrictEqual(paths, ['a.js', 'b.js']);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('Bash with command returns empty array', () => {
+      const paths = extractFilePaths('Bash', { command: 'ls' });
+      assert.deepStrictEqual(paths, []);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('null toolInput returns empty array', () => {
+      const paths = extractFilePaths('Edit', null);
+      assert.deepStrictEqual(paths, []);
+    })
+  )
+    passed++;
+  else failed++;
+
+  // readSessionCost tests
+  console.log('\nreadSessionCost:');
+
+  if (
+    test('nonexistent session returns object with numeric fields', () => {
+      const result = readSessionCost('nonexistent-session-cost-test-xyz-999');
+      assert.strictEqual(typeof result.totalCost, 'number');
+      assert.strictEqual(typeof result.totalIn, 'number');
+      assert.strictEqual(typeof result.totalOut, 'number');
+      assert.ok(result.totalCost >= 0, 'totalCost should be non-negative');
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('readSessionCost does not include unrelated default-session rows', () => {
+      const tmpHome = makeTempHome();
+      const originalHome = process.env.HOME;
+      const originalUserProfile = process.env.USERPROFILE;
+      try {
+        process.env.HOME = tmpHome;
+        process.env.USERPROFILE = tmpHome;
+        const metricsDir = path.join(tmpHome, '.claude', 'metrics');
+        fs.mkdirSync(metricsDir, { recursive: true });
+        fs.writeFileSync(
+          path.join(metricsDir, 'costs.jsonl'),
+          [
+            JSON.stringify({ session_id: 'default', estimated_cost_usd: 50, input_tokens: 1000, output_tokens: 2000 }),
+            JSON.stringify({ session_id: 'target-session', estimated_cost_usd: 1.25, input_tokens: 10, output_tokens: 20 })
+          ].join('\n') + '\n',
+          'utf8'
+        );
+        const result = readSessionCost('target-session');
+        assert.strictEqual(result.totalCost, 1.25);
+        assert.strictEqual(result.totalIn, 10);
+        assert.strictEqual(result.totalOut, 20);
+      } finally {
+        if (originalHome === undefined) delete process.env.HOME;
+        else process.env.HOME = originalHome;
+        if (originalUserProfile === undefined) delete process.env.USERPROFILE;
+        else process.env.USERPROFILE = originalUserProfile;
+        fs.rmSync(tmpHome, { recursive: true, force: true });
+      }
+    })
+  )
+    passed++;
+  else failed++;
+
+  // run tests
+  console.log('\nrun:');
+
+  if (
+    test('empty input returns empty input without crashing', () => {
+      const result = run('');
+      assert.strictEqual(result, '');
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('whitespace-only input returns input unchanged', () => {
+      const result = run('   ');
+      assert.strictEqual(result, '   ');
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('input without session_id returns input unchanged', () => {
+      const input = JSON.stringify({ tool_name: 'Bash', tool_input: { command: 'ls' } });
+      const result = run(input);
+      assert.strictEqual(result, input);
+    })
+  )
+    passed++;
+  else failed++;
+
+  // Summary
+  console.log(`\nResults: ${passed} passed, ${failed} failed\n`);
+  return { passed, failed };
+}
+
+const { failed } = runTests();
+process.exit(failed > 0 ? 1 : 0);
diff --git a/tests/hooks/ecc-statusline.test.js b/tests/hooks/ecc-statusline.test.js
new file mode 100644
index 00000000..f7cfacd7
--- /dev/null
+++ b/tests/hooks/ecc-statusline.test.js
@@ -0,0 +1,213 @@
+/**
+ * Tests for scripts/hooks/ecc-statusline.js
+ *
+ * Run with: node tests/hooks/ecc-statusline.test.js
+ */
+
+const assert = require('assert');
+const fs = require('fs');
+const os = require('os');
+const path = require('path');
+
+const { formatDuration, buildContextBar, readCurrentTask } = require('../../scripts/hooks/ecc-statusline');
+
+// Test helper
+function test(name, fn) {
+  try {
+    fn();
+    console.log(`  \u2713 ${name}`);
+    return true;
+  } catch (err) {
+    console.log(`  \u2717 ${name}`);
+    console.log(`    Error: ${err.message}`);
+    return false;
+  }
+}
+
+function makeTempConfig() {
+  return fs.mkdtempSync(path.join(os.tmpdir(), 'ecc-statusline-test-'));
+}
+
+function runTests() {
+  console.log('\n=== Testing ecc-statusline.js ===\n');
+
+  let passed = 0;
+  let failed = 0;
+
+  // formatDuration tests
+  console.log('formatDuration:');
+
+  if (
+    test('null returns "?"', () => {
+      assert.strictEqual(formatDuration(null), '?');
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('undefined returns "?"', () => {
+      assert.strictEqual(formatDuration(undefined), '?');
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('timestamp 30 seconds ago ends with "s"', () => {
+      const ts = new Date(Date.now() - 30 * 1000).toISOString();
+      const result = formatDuration(ts);
+      assert.ok(result.endsWith('s'), `Expected ending in "s", got: ${result}`);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('timestamp 5 minutes ago ends with "m"', () => {
+      const ts = new Date(Date.now() - 5 * 60 * 1000).toISOString();
+      const result = formatDuration(ts);
+      assert.ok(result.endsWith('m'), `Expected ending in "m", got: ${result}`);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('timestamp 90 minutes ago contains "h"', () => {
+      const ts = new Date(Date.now() - 90 * 60 * 1000).toISOString();
+      const result = formatDuration(ts);
+      assert.ok(result.includes('h'), `Expected "h" in result, got: ${result}`);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('future timestamp returns "?"', () => {
+      const ts = new Date(Date.now() + 60 * 1000).toISOString();
+      const result = formatDuration(ts);
+      assert.strictEqual(result, '?');
+    })
+  )
+    passed++;
+  else failed++;
+
+  // buildContextBar tests
+  console.log('\nbuildContextBar:');
+
+  if (
+    test('null returns empty string', () => {
+      assert.strictEqual(buildContextBar(null), '');
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('undefined returns empty string', () => {
+      assert.strictEqual(buildContextBar(undefined), '');
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('80% remaining contains green ANSI code', () => {
+      const bar = buildContextBar(80);
+      assert.ok(bar.includes('\x1b[32m'), `Expected green ANSI in: ${JSON.stringify(bar)}`);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('50% remaining contains yellow ANSI code', () => {
+      const bar = buildContextBar(50);
+      assert.ok(bar.includes('\x1b[33m'), `Expected yellow ANSI in: ${JSON.stringify(bar)}`);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('20% remaining contains red blink ANSI code', () => {
+      const bar = buildContextBar(20);
+      assert.ok(bar.includes('\x1b[5;31m'), `Expected red blink ANSI in: ${JSON.stringify(bar)}`);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('context bar contains block characters', () => {
+      const bar = buildContextBar(60);
+      assert.ok(bar.includes('\u2588') || bar.includes('\u2591'), 'Expected block characters in bar');
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('context bar contains percentage', () => {
+      const bar = buildContextBar(70);
+      assert.ok(bar.includes('%'), 'Expected percentage in bar');
+    })
+  )
+    passed++;
+  else failed++;
+
+  // readCurrentTask tests
+  console.log('\nreadCurrentTask:');
+
+  if (
+    test('nonexistent session returns empty string', () => {
+      const result = readCurrentTask('nonexistent-session-xyz-999');
+      assert.strictEqual(result, '');
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('empty string session returns empty string', () => {
+      const result = readCurrentTask('');
+      assert.strictEqual(result, '');
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('reads in-progress task for sanitized session ID only', () => {
+      const tmpConfig = makeTempConfig();
+      const originalConfig = process.env.CLAUDE_CONFIG_DIR;
+      try {
+        process.env.CLAUDE_CONFIG_DIR = tmpConfig;
+        const todosDir = path.join(tmpConfig, 'todos');
+        fs.mkdirSync(todosDir, { recursive: true });
+        fs.writeFileSync(
+          path.join(todosDir, 'safe-session-agent-main.json'),
+          JSON.stringify([{ status: 'in_progress', activeForm: 'Fix auth flow' }]),
+          'utf8'
+        );
+
+        assert.strictEqual(readCurrentTask('safe-session'), 'Fix auth flow');
+        assert.strictEqual(readCurrentTask('../safe-session'), '');
+      } finally {
+        if (originalConfig === undefined) delete process.env.CLAUDE_CONFIG_DIR;
+        else process.env.CLAUDE_CONFIG_DIR = originalConfig;
+        fs.rmSync(tmpConfig, { recursive: true, force: true });
+      }
+    })
+  )
+    passed++;
+  else failed++;
+
+  // Summary
+  console.log(`\nResults: ${passed} passed, ${failed} failed\n`);
+  return { passed, failed };
+}
+
+const { failed } = runTests();
+process.exit(failed > 0 ? 1 : 0);
diff --git a/tests/lib/cost-estimate.test.js b/tests/lib/cost-estimate.test.js
new file mode 100644
index 00000000..bcb5906b
--- /dev/null
+++ b/tests/lib/cost-estimate.test.js
@@ -0,0 +1,114 @@
+/**
+ * Tests for scripts/lib/cost-estimate.js
+ *
+ * Run with: node tests/lib/cost-estimate.test.js
+ */
+
+const assert = require('assert');
+
+const { estimateCost, RATE_TABLE } = require('../../scripts/lib/cost-estimate');
+
+// Test helper
+function test(name, fn) {
+  try {
+    fn();
+    console.log(`  \u2713 ${name}`);
+    return true;
+  } catch (err) {
+    console.log(`  \u2717 ${name}`);
+    console.log(`    Error: ${err.message}`);
+    return false;
+  }
+}
+
+function runTests() {
+  console.log('\n=== Testing cost-estimate.js ===\n');
+
+  let passed = 0;
+  let failed = 0;
+
+  // RATE_TABLE structure
+  console.log('RATE_TABLE:');
+
+  if (
+    test('RATE_TABLE has haiku, sonnet, opus keys', () => {
+      assert.ok(RATE_TABLE.haiku, 'Missing haiku');
+      assert.ok(RATE_TABLE.sonnet, 'Missing sonnet');
+      assert.ok(RATE_TABLE.opus, 'Missing opus');
+      assert.strictEqual(typeof RATE_TABLE.haiku.in, 'number');
+      assert.strictEqual(typeof RATE_TABLE.haiku.out, 'number');
+      assert.strictEqual(typeof RATE_TABLE.sonnet.in, 'number');
+      assert.strictEqual(typeof RATE_TABLE.sonnet.out, 'number');
+      assert.strictEqual(typeof RATE_TABLE.opus.in, 'number');
+      assert.strictEqual(typeof RATE_TABLE.opus.out, 'number');
+    })
+  )
+    passed++;
+  else failed++;
+
+  // estimateCost tests
+  console.log('\nestimateCost:');
+
+  if (
+    test('opus 1M/1M tokens returns 90', () => {
+      const cost = estimateCost('opus', 1_000_000, 1_000_000);
+      assert.strictEqual(cost, 90);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('sonnet 1M/1M tokens returns 18', () => {
+      const cost = estimateCost('sonnet', 1_000_000, 1_000_000);
+      assert.strictEqual(cost, 18);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('haiku 1M/1M tokens returns 4.8', () => {
+      const cost = estimateCost('haiku', 1_000_000, 1_000_000);
+      assert.strictEqual(cost, 4.8);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('null model with 0 tokens returns 0', () => {
+      const cost = estimateCost(null, 0, 0);
+      assert.strictEqual(cost, 0);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('full model name claude-opus-4-6 uses opus rates', () => {
+      const cost = estimateCost('claude-opus-4-6', 500, 200);
+      // (500 / 1_000_000) * 15 + (200 / 1_000_000) * 75 = 0.0075 + 0.015 = 0.0225
+      const expected = Math.round(0.0225 * 1e6) / 1e6;
+      assert.strictEqual(cost, expected);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('unknown model falls back to sonnet rates', () => {
+      const cost = estimateCost('unknown-model', 1_000_000, 1_000_000);
+      assert.strictEqual(cost, 18);
+    })
+  )
+    passed++;
+  else failed++;
+
+  // Summary
+  console.log(`\nResults: ${passed} passed, ${failed} failed\n`);
+  return { passed, failed };
+}
+
+const { failed } = runTests();
+process.exit(failed > 0 ? 1 : 0);
diff --git a/tests/lib/session-bridge.test.js b/tests/lib/session-bridge.test.js
new file mode 100644
index 00000000..60841c9b
--- /dev/null
+++ b/tests/lib/session-bridge.test.js
@@ -0,0 +1,174 @@
+/**
+ * Tests for scripts/lib/session-bridge.js
+ *
+ * Run with: node tests/lib/session-bridge.test.js
+ */
+
+const assert = require('assert');
+const fs = require('fs');
+
+const { sanitizeSessionId, getBridgePath, readBridge, writeBridgeAtomic, resolveSessionId, MAX_SESSION_ID_LENGTH } = require('../../scripts/lib/session-bridge');
+
+// Test helper
+function test(name, fn) {
+  try {
+    fn();
+    console.log(`  \u2713 ${name}`);
+    return true;
+  } catch (err) {
+    console.log(`  \u2717 ${name}`);
+    console.log(`    Error: ${err.message}`);
+    return false;
+  }
+}
+
+function runTests() {
+  console.log('\n=== Testing session-bridge.js ===\n');
+
+  let passed = 0;
+  let failed = 0;
+
+  // sanitizeSessionId tests
+  console.log('sanitizeSessionId:');
+
+  if (
+    test('valid ID passes through', () => {
+      assert.strictEqual(sanitizeSessionId('abc-123'), 'abc-123');
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('path traversal returns null', () => {
+      assert.strictEqual(sanitizeSessionId('../etc/passwd'), null);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('forward slash returns null', () => {
+      assert.strictEqual(sanitizeSessionId('/tmp/evil'), null);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('backslash returns null', () => {
+      assert.strictEqual(sanitizeSessionId('a\\b'), null);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('null input returns null', () => {
+      assert.strictEqual(sanitizeSessionId(null), null);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('empty string returns null', () => {
+      assert.strictEqual(sanitizeSessionId(''), null);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('long string is truncated to MAX_SESSION_ID_LENGTH', () => {
+      const longId = 'a'.repeat(100);
+      const result = sanitizeSessionId(longId);
+      assert.ok(result, 'Should not return null for valid chars');
+      assert.strictEqual(result.length, MAX_SESSION_ID_LENGTH);
+    })
+  )
+    passed++;
+  else failed++;
+
+  // getBridgePath tests
+  console.log('\ngetBridgePath:');
+
+  if (
+    test('returns path containing ecc-metrics-', () => {
+      const p = getBridgePath('test-session');
+      assert.ok(p.includes('ecc-metrics-'), `Expected ecc-metrics- in path, got: ${p}`);
+    })
+  )
+    passed++;
+  else failed++;
+
+  // writeBridgeAtomic + readBridge roundtrip
+  console.log('\nwriteBridgeAtomic / readBridge:');
+
+  if (
+    test('roundtrip write then read returns same data', () => {
+      const testId = `test-bridge-${Date.now()}`;
+      const data = { session_id: testId, tool_count: 42 };
+      try {
+        writeBridgeAtomic(testId, data);
+        const result = readBridge(testId);
+        assert.deepStrictEqual(result, data);
+      } finally {
+        // Clean up
+        try {
+          fs.unlinkSync(getBridgePath(testId));
+        } catch {
+          /* ignore */
+        }
+      }
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('readBridge with nonexistent session returns null', () => {
+      const result = readBridge('nonexistent-session-id-999');
+      assert.strictEqual(result, null);
+    })
+  )
+    passed++;
+  else failed++;
+
+  // resolveSessionId tests
+  console.log('\nresolveSessionId:');
+
+  if (
+    test('resolveSessionId uses ECC_SESSION_ID env var', () => {
+      const original = process.env.ECC_SESSION_ID;
+      try {
+        process.env.ECC_SESSION_ID = 'env-session-42';
+        const result = resolveSessionId();
+        assert.strictEqual(result, 'env-session-42');
+      } finally {
+        if (original === undefined) {
+          delete process.env.ECC_SESSION_ID;
+        } else {
+          process.env.ECC_SESSION_ID = original;
+        }
+      }
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('MAX_SESSION_ID_LENGTH is 64', () => {
+      assert.strictEqual(MAX_SESSION_ID_LENGTH, 64);
+    })
+  )
+    passed++;
+  else failed++;
+
+  // Summary
+  console.log(`\nResults: ${passed} passed, ${failed} failed\n`);
+  return { passed, failed };
+}
+
+const { failed } = runTests();
+process.exit(failed > 0 ? 1 : 0);