diff --git a/.auto/baseline.env b/.auto/baseline.env
new file mode 100644
index 00000000..71419500
--- /dev/null
+++ b/.auto/baseline.env
@@ -0,0 +1,12 @@
+# Autoresearch baseline — captured at iteration #0 (2026-08-29).
+# The Guard compares live values against these floors; the PRIMARY metric is debt.
+BASE_DEBT=102
+BASE_NOLINT=96
+BASE_TESTS_PASSED=46
+BASE_TEST_FUNCS=232
+BASE_TEST_FILES=76
+BASE_ARCH_VIOL=0
+BASE_COVERAGE=34.09
+
+# SHA-256 of the pinned yardstick config. Guard aborts if it changes.
+REF_SHA=e881bda167bd688489f1356b7cd4056b8a6960f48b6778b095bdd2e44f627b82
diff --git a/.auto/check_gate_weaken.py b/.auto/check_gate_weaken.py
new file mode 100644
index 00000000..42467641
--- /dev/null
+++ b/.auto/check_gate_weaken.py
@@ -0,0 +1,117 @@
+#!/usr/bin/env python3
+"""Anti-cheat: prove .golangci.yml was only ever strengthened, never weakened.
+
+Compares the live gate against the immutable snapshot taken at run start.
+Exits non-zero with a reason if any hardening rule is violated.
+"""
+
+import os
+import sys
+
+import yaml
+
+ROOT = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+BASELINE = os.path.join(ROOT, ".auto", "gate.baseline.yml")
+LIVE = os.path.join(ROOT, ".golangci.yml")
+
+# threshold-like knobs: (path, direction) where direction "max" means the value
+# is an upper bound (smaller == stricter), "min" means a lower bound.
+STRICTNESS = [
+    (("linters", "settings", "dupl", "threshold"), "max"),
+    (("linters", "settings", "cyclop", "max-complexity"), "max"),
+    (("linters", "settings", "cyclop", "package-average"), "max"),
+    (("linters", "settings", "nestif", "min-complexity"), "min"),
+    (("linters", "settings", "funlen", "lines"), "max"),
+    (("linters", "settings", "funlen", "statements"), "max"),
+    (("linters", "settings", "gocyclo", "min-complexity"), "min"),
+    (("linters", "settings", "lll", "line-length"), "max"),
+]
+
+
+def load(path):
+    with open(path, encoding="utf-8") as fh:
+        return yaml.safe_load(fh) or {}
+
+
+def dig(doc, path):
+    node = doc
+    for key in path:
+        if not isinstance(node, dict) or key not in node:
+            return None
+        node = node[key]
+    return node
+
+
+def enabled_linters(doc):
+    lint = doc.get("linters") or {}
+    if lint.get("enable-presets"):
+        return None  # preset based; fall back to "any removal is suspicious"
+    return set(lint.get("enable") or [])
+
+
+def main():
+    try:
+        base, live = load(BASELINE), load(LIVE)
+    except OSError as exc:
+        print(f"gate snapshot unreadable: {exc}")
+        return 1
+    except yaml.YAMLError as exc:
+        print(f".golangci.yml is not parseable: {exc}")
+        return 1
+
+    problems = []
+
+    base_lint, live_lint = base.get("linters") or {}, live.get("linters") or {}
+    if (base_lint.get("default") or "none") != (live_lint.get("default") or "none"):
+        problems.append("linters.default changed")
+
+    base_set, live_set = enabled_linters(base), enabled_linters(live)
+    if base_set is None or live_set is None:
+        if set((base.get("linters") or {}).get("enable-presets") or []) - set(
+            (live.get("linters") or {}).get("enable-presets") or []
+        ):
+            problems.append("an enable-preset was removed")
+    elif dropped := base_set - live_set:
+        problems.append(f"linters disabled: {sorted(dropped)}")
+
+    for path, direction in STRICTNESS:
+        old, new = dig(base, path), dig(live, path)
+        if old is None or new is None:
+            continue
+        try:
+            old_f, new_f = float(old), float(new)
+        except (TypeError, ValueError):
+            continue
+        if direction == "max" and new_f > old_f:
+            problems.append(f"{'.'.join(path)} loosened {old} -> {new}")
+        if direction == "min" and new_f < old_f:
+            problems.append(f"{'.'.join(path)} loosened {old} -> {new}")
+
+    base_mnd = set(dig(base, ("linters", "settings", "mnd", "checks")) or [])
+    live_mnd = set(dig(live, ("linters", "settings", "mnd", "checks")) or [])
+    if base_mnd - live_mnd:
+        problems.append(f"mnd checks dropped: {sorted(base_mnd - live_mnd)}")
+
+    issues_live = live.get("issues") or {}
+    for key in ("exclude-rules", "exclude-patterns"):
+        if issues_live.get(key) and not (base.get("issues") or {}).get(key):
+            problems.append(f"issues.{key} added (suppresses reporting)")
+
+    for key in ("max-issues-per-linter", "max-same-issues"):
+        old = (base.get("issues") or {}).get(key)
+        new = issues_live.get(key)
+        if old == 0 and new != 0:
+            problems.append(f"issues.{key} no longer 0 — findings would be truncated")
+
+    # Exclusions expressed through the newer 'linters.exclusions' block.
+    if (live_lint.get("exclusions") or {}) and not (base_lint.get("exclusions") or {}):
+        problems.append("linters.exclusions added")
+
+    if problems:
+        print("\n".join(f"  - {p}" for p in problems))
+        return 1
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/.auto/checks.sh b/.auto/checks.sh
index 72631f79..c4bad42a 100755
--- a/.auto/checks.sh
+++ b/.auto/checks.sh
@@ -1,11 +1,50 @@
 #!/bin/bash
-# Correctness gate: build + full tests + Cordis architecture checker (errors only)
-set -euo pipefail
-cd "$(dirname "$0")/../backend"
+# Autoresearch GUARD — hard veto. Every line here protects an invariant that is
+# unrelated to the primary metric, plus the anti-cheat red lines.
+set -uo pipefail
+ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+cd "${ROOT}/backend"
+STATUS=0
+fail() { echo "GUARD FAIL: $1"; STATUS=1; }
 
-go build ./... 2>&1 | head -20
-go test ./... 2>&1 | grep -vE '^(ok|---|\?|PASS)' | grep -v 'no test files' | head -40 || true
-FAILS=$(go test ./... 2>&1 | grep -cE '^(FAIL|--- FAIL)' || true)
-if [ "${FAILS}" != "0" ]; then echo "TESTS FAILED (${FAILS})"; exit 1; fi
-"$(dirname "$0")/../scripts/check_cordis_architecture.sh" >/dev/null 2>&1 || { echo "CORDIS ARCH CHECK FAILED"; exit 1; }
-echo "CHECKS OK"
+source "${ROOT}/.auto/baseline.env"
+
+# --- 1. Correctness -----------------------------------------------------------
+go build ./... || fail "go build failed"
+go vet ./...   || fail "go vet failed"
+
+go test ./... > /tmp/ar_guard_test.txt 2>&1 || true
+FAILS=$(grep -cE '^(FAIL|--- FAIL)' /tmp/ar_guard_test.txt || true)
+[ "${FAILS}" = "0" ] || { grep -E '^(FAIL|--- FAIL)' /tmp/ar_guard_test.txt | head -20; fail "tests failing (${FAILS})"; }
+
+# --- 2. Cordis architecture gate ---------------------------------------------
+"${ROOT}/scripts/check_cordis_architecture.sh" > /dev/null 2>&1 || fail "cordis architecture check failed"
+
+# --- 3. Project lint gate must stay clean ------------------------------------
+PROJECT_LINT=$(golangci-lint run 2>&1 | grep -cE '\.go:[0-9]+:[0-9]+: ' || true)
+[ "${PROJECT_LINT}" = "0" ] || { fail "project golangci-lint reports ${PROJECT_LINT} issues"; }
+
+# --- 4. Anti-cheat: the yardstick itself is immutable ------------------------
+REF_SHA_NOW=$(shasum -a 256 "${ROOT}/.auto/lint.ref.yaml" | awk '{print $1}')
+[ "${REF_SHA_NOW}" = "${REF_SHA}" ] || fail "pinned yardstick .auto/lint.ref.yaml was modified"
+
+# --- 5. Anti-cheat: the project gate may only ever be STRENGTHENED ------------
+WEAK=$(python3 "${ROOT}/.auto/check_gate_weaken.py" 2>&1) || { echo "${WEAK}"; fail "project gate weakened"; }
+
+# --- 6. Anti-cheat: no new suppressions --------------------------------------
+NOLINT=$(rg '//\s*nolint' --glob '*.go' 2>/dev/null | wc -l | tr -d ' ')
+[ "${NOLINT}" -le "${BASE_NOLINT}" ] || fail "nolint directives grew (${NOLINT} > ${BASE_NOLINT})"
+
+# --- 7. Anti-cheat: no tests deleted, no packages lost -----------------------
+TEST_FUNCS=$(rg -c '^(func Test|func Benchmark)' --glob '*_test.go' 2>/dev/null | awk -F: '{s+=$2} END {print s+0}')
+[ "${TEST_FUNCS}" -ge "${BASE_TEST_FUNCS}" ] || fail "test funcs shrank (${TEST_FUNCS} < ${BASE_TEST_FUNCS})"
+TEST_FILES=$(rg --files --glob '*_test.go' 2>/dev/null | wc -l | tr -d ' ')
+[ "${TEST_FILES}" -ge "${BASE_TEST_FILES}" ] || fail "test files deleted (${TEST_FILES} < ${BASE_TEST_FILES})"
+PASSED=$(grep -c '^ok' /tmp/ar_guard_test.txt || true)
+[ "${PASSED}" -ge "${BASE_TESTS_PASSED}" ] || fail "passing packages shrank (${PASSED} < ${BASE_TESTS_PASSED})"
+
+# --- 8. License headers on Go sources (CI gate) ------------------------------
+"${ROOT}/scripts/update_go_license.sh" --check > /dev/null 2>&1 || fail "license header check failed"
+
+if [ "${STATUS}" = "0" ]; then echo "CHECKS OK"; fi
+exit ${STATUS}
diff --git a/.auto/gate.baseline.yml b/.auto/gate.baseline.yml
new file mode 100644
index 00000000..adb951c1
--- /dev/null
+++ b/.auto/gate.baseline.yml
@@ -0,0 +1,61 @@
+version: "2"
+
+run:
+  timeout: 5m
+  tests: false
+
+linters:
+  default: none
+  enable:
+    # 基础检查
+    - govet
+    - staticcheck
+    - errcheck
+    - ineffassign
+    - unused
+
+    # 代码坏味道
+    - dupl          # 重复代码
+    - mnd           # 魔法数字
+    - goconst       # 不必要的字符串常量
+    - cyclop        # 包/函数复杂度
+    - nestif        # if 嵌套太深
+    - maintidx      # 维护性指数
+    - revive        # 风格/命名/坏味道
+    - gocritic      # 各类代码问题
+    - funlen        # 函数过长
+
+    - gosec         # 安全问题检查
+    - bodyclose     # HTTP response body 没有正确关闭
+    - noctx         # 没有传递 context.Context
+    - contextcheck  # 其他检查
+    - sqlclosecheck # SQL rows 没有正确关闭
+    - unconvert     # 不必要的类型转换
+    - nilerr        # 函数返回 nil 错误
+
+  settings:
+    dupl:
+      threshold: 80
+
+    cyclop:
+      max-complexity: 20
+      package-average: 10
+
+    nestif:
+      min-complexity: 5
+
+    funlen:
+      lines: 200
+      statements: 100
+
+    mnd:
+      checks:
+        - argument
+        - condition
+        - return
+
+
+# 完整上报所有问题（取消 golangci 默认 50/3 截断，保证 code-check 与度量真实）
+issues:
+  max-issues-per-linter: 0
+  max-same-issues: 0
\ No newline at end of file
diff --git a/.auto/lint.ref.yaml b/.auto/lint.ref.yaml
new file mode 100644
index 00000000..b60c74b1
--- /dev/null
+++ b/.auto/lint.ref.yaml
@@ -0,0 +1,78 @@
+version: "2"
+
+# Pinned autoresearch yardstick. IMMUTABLE for the duration of a run.
+# Snapshot of the committed .golangci.yml plus the extra analyzers that report
+# genuine defects (correctness / panics / dead code) rather than cosmetics.
+# Keeping this separate from .golangci.yml means strengthening the project gate
+# can never silently lower the measured debt.
+
+run:
+  timeout: 5m
+  tests: false
+
+linters:
+  default: none
+  enable:
+    # --- from the committed project gate ---
+    - govet
+    - staticcheck
+    - errcheck
+    - ineffassign
+    - unused
+    - dupl
+    - mnd
+    - goconst
+    - cyclop
+    - nestif
+    - maintidx
+    - revive
+    - gocritic
+    - funlen
+    - gosec
+    - bodyclose
+    - noctx
+    - contextcheck
+    - sqlclosecheck
+    - unconvert
+    - nilerr
+    # --- extra real-risk analyzers (defects, not cosmetics) ---
+    - errorlint        # err == / %v instead of errors.Is/As and %w
+    - forcetypeassert  # unchecked type assertions can panic
+    - nilnil           # (value, nil) breaks the nil-check contract
+    - predeclared      # shadowing builtins
+    - unparam          # dead params/results
+    - wastedassign     # dead stores
+    - exhaustive       # enum switches missing cases
+    - makezero         # append to preallocated slice
+    - rowserrcheck     # sql.Rows error after iteration
+    - durationcheck    # multiplied time.Duration
+    - prealloc         # slice growth in loops
+    - copyloopvar      # loop-var capture
+    - nonamedreturns
+    - funcorder        # struct methods scattered across files
+    - nolintlint       # suppression audit (must stay 0)
+
+  settings:
+    dupl:
+      threshold: 80
+
+    cyclop:
+      max-complexity: 20
+      package-average: 10
+
+    nestif:
+      min-complexity: 5
+
+    funlen:
+      lines: 200
+      statements: 100
+
+    mnd:
+      checks:
+        - argument
+        - condition
+        - return
+
+issues:
+  max-issues-per-linter: 0
+  max-same-issues: 0
diff --git a/.auto/measure.sh b/.auto/measure.sh
index ccf47e4d..cb752fc3 100755
--- a/.auto/measure.sh
+++ b/.auto/measure.sh
@@ -1,18 +1,38 @@
 #!/bin/bash
-# Autoresearch measure: golangci-lint issue count (primary) + dupl subset + test packages
-set -euo pipefail
+# Autoresearch measure — pinned yardstick.
+#   debt          : findings under .auto/lint.ref.yaml (lower is better)  [PRIMARY]
+#   nolint_dirs   : raw //nolint directive count (lower is better, floor 0)
+#   tests_passed  : go test packages passing (floor, must never drop)
+#   test_funcs    : total Test*/Benchmark* funcs (floor, must never drop)
+#   arch_viol     : Cordis architecture script violations (floor 0)
+#   coverage      : backend statement coverage % (informational)
+set -uo pipefail
 cd "$(dirname "$0")/../backend"
 
-# Primary metric: total golangci-lint issues (non-test code)
-golangci-lint run > /tmp/ar_lint.txt 2>&1 || true
-LINT_ISSUES=$(grep -cE '(^|[/\\])[^/\\:]+\.go:[0-9]+:' /tmp/ar_lint.txt || true)
+REF_CFG="$(cd .. && pwd)/.auto/lint.ref.yaml"
 
-# Secondary: dupl-specific issues
-DUP_ISSUES=$(grep -cE '\(dupl\)$' /tmp/ar_lint.txt || true)
+# Primary: pinned yardstick findings (never the mutable project config).
+golangci-lint run -c "${REF_CFG}" > /tmp/ar_debt.txt 2>&1 || true
+DEBT=$(grep -cE '\.go:[0-9]+:[0-9]+: ' /tmp/ar_debt.txt || true)
 
-# Secondary: passing test packages (regression guard)
-TESTS_PASSED=$(go test ./... 2>&1 | grep -c '^ok' || true)
+# Suppression reliance — anti-cheat signal.
+NOLINT=$(rg '//\s*nolint' --glob '*.go' 2>/dev/null | wc -l | tr -d ' ')
 
-echo "METRIC lint_issues=${LINT_ISSUES}"
-echo "METRIC dup_issues=${DUP_ISSUES}"
+# Regression floors. One covered run feeds both the pass floor and coverage.
+go test -cover ./... > /tmp/ar_test.txt 2>&1 || true
+TESTS_PASSED=$(grep -c '^ok' /tmp/ar_test.txt || true)
+FAILS=$(grep -cE '^(FAIL|--- FAIL)' /tmp/ar_test.txt || true)
+TEST_FUNCS=$(rg -c '^(func Test|func Benchmark)' --glob '*_test.go' 2>/dev/null | awk -F: '{s+=$2} END {print s+0}')
+
+# Cordis architecture violations (count of FAIL lines emitted by the gate script).
+ARCH_VIOL=$("../scripts/check_cordis_architecture.sh" 2>&1 | grep -c 'FAIL' || true)
+
+COVERAGE=$(grep -oE 'coverage: [0-9.]+%' /tmp/ar_test.txt | awk '{gsub("%","",$2); s+=$2; n++} END {if(n>0) printf "%.2f", s/n; else print "0"}')
+
+echo "METRIC debt=${DEBT}"
+echo "METRIC nolint_dirs=${NOLINT}"
 echo "METRIC tests_passed=${TESTS_PASSED}"
+echo "METRIC test_funcs=${TEST_FUNCS}"
+echo "METRIC arch_viol=${ARCH_VIOL}"
+echo "METRIC coverage=${COVERAGE}"
+echo "INFO test_failures=${FAILS}"
diff --git a/.auto/prove_fix.sh b/.auto/prove_fix.sh
new file mode 100755
index 00000000..7e20d716
--- /dev/null
+++ b/.auto/prove_fix.sh
@@ -0,0 +1,55 @@
+#!/bin/bash
+# Mechanically prove a FIX iteration is load-bearing.
+#
+# Usage: .auto/prove_fix.sh <package> <changed source file> [<more files>...]
+#
+# Run immediately AFTER committing the fix, with a clean worktree. It reverts
+# only the non-test source files to their pre-fix state (keeping the new test),
+# runs the package tests, and requires them to FAIL. Then it restores HEAD.
+# A fix nobody can break with a revert is not a fix.
+set -uo pipefail
+ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+
+if [ ! -z "$(git -C "${ROOT}" status --porcelain)" ]; then
+    echo "PROVE ABORT: worktree must be clean (commit the change first)"
+    exit 2
+fi
+
+PKG="$1"; shift
+SRC_FILES=("$@")
+if [ "${#SRC_FILES[@]}" -eq 0 ]; then
+    echo "PROVE ABORT: no source files given"
+    exit 2
+fi
+
+cd "${ROOT}/backend" || exit 2
+
+restore() {
+    git -C "${ROOT}" checkout HEAD -- "${SRC_FILES[@]}" 2>/dev/null
+}
+trap restore EXIT
+
+for f in "${SRC_FILES[@]}"; do
+    if git -C "${ROOT}" cat-file -e "HEAD^:${f}" 2>/dev/null; then
+        git -C "${ROOT}" checkout "HEAD^" -- "${f}" || { echo "PROVE ABORT: cannot revert ${f}"; exit 2; }
+    else
+        # File did not exist before this commit — removing it is the revert.
+        rm -f "${ROOT}/${f}"
+    fi
+done
+
+echo "--- tests against pre-fix source ---"
+OUT=$(go test -count=1 "${PKG}" 2>&1)
+RC=$?
+echo "${OUT}" | tail -15
+if [ "${RC}" -eq 0 ]; then
+    echo "PROVE FAILED: tests still pass without the fix — this is not a real bug fix"
+    exit 1
+fi
+if echo "${OUT}" | grep -qE '^(FAIL|--- FAIL)'; then
+    KIND="assertion"
+else
+    KIND="compile"
+fi
+echo "PROVED: test fails without the fix (${KIND})"
+exit 0
diff --git a/.auto/results.tsv b/.auto/results.tsv
new file mode 100644
index 00000000..cfc3f7ef
--- /dev/null
+++ b/.auto/results.tsv
@@ -0,0 +1,2 @@
+iteration	commit	metric	delta	status	guard	description
+0	-	102	0.0	baseline	pass	initial measurement (pinned yardstick: repo gate + real-risk analyzers)