diff --git a/deploy/dalidou/batch-extract.sh b/deploy/dalidou/batch-extract.sh
index 8bd515b..f78ec1b 100644
--- a/deploy/dalidou/batch-extract.sh
+++ b/deploy/dalidou/batch-extract.sh
@@ -197,6 +197,19 @@ python3 "$APP_DIR/scripts/memory_dedup.py" \
     log "WARN: memory dedup failed (non-blocking)"
 }
 
+# Step B4: Tag canonicalization (Phase 7C, weekly Sundays)
+# Autonomous: LLM proposes alias→canonical maps, auto-applies confidence >= 0.8.
+# Projects tokens are protected (skipped on both sides). Borderline proposals
+# land in /admin/tags/aliases for human review.
+if [[ "$(date -u +%u)" == "7" ]]; then
+    log "Step B4: tag canonicalization (Sunday)"
+    python3 "$APP_DIR/scripts/canonicalize_tags.py" \
+        --base-url "$ATOCORE_URL" \
+        2>&1 || {
+        log "WARN: tag canonicalization failed (non-blocking)"
+    }
+fi
+
 # Step G: Integrity check (Phase 4 V1)
 log "Step G: integrity check"
 python3 "$APP_DIR/scripts/integrity_check.py" \
diff --git a/scripts/canonicalize_tags.py b/scripts/canonicalize_tags.py
new file mode 100644
index 0000000..51bf5b2
--- /dev/null
+++ b/scripts/canonicalize_tags.py
@@ -0,0 +1,254 @@
+#!/usr/bin/env python3
+"""Phase 7C — tag canonicalization detector.
+
+Weekly (or on-demand) LLM pass that:
+  1. Fetches the tag distribution across all active memories via HTTP
+  2. Asks claude-p to propose alias→canonical mappings
+  3. AUTO-APPLIES aliases with confidence >= AUTO_APPROVE_CONF (0.8)
+  4. Submits lower-confidence proposals as pending for human review
+
+Autonomous by default — matches the Phase 7A.1 pattern. Set
+--no-auto-approve to force every proposal into human review.
+
+Host-side because claude CLI lives on Dalidou, not the container.
+Reuses the PYTHONPATH=src pattern from scripts/memory_dedup.py.
+
+Usage:
+  python3 scripts/canonicalize_tags.py [--base-url URL] [--dry-run] [--no-auto-approve]
+"""
+
+from __future__ import annotations
+
+import argparse
+import json
+import os
+import shutil
+import subprocess
+import sys
+import tempfile
+import time
+import urllib.error
+import urllib.request
+
+_SCRIPT_DIR = os.path.dirname(os.path.abspath(__file__))
+_SRC_DIR = os.path.abspath(os.path.join(_SCRIPT_DIR, "..", "src"))
+if _SRC_DIR not in sys.path:
+    sys.path.insert(0, _SRC_DIR)
+
+from atocore.memory._tag_canon_prompt import (  # noqa: E402
+    PROTECTED_PROJECT_TOKENS,
+    SYSTEM_PROMPT,
+    TAG_CANON_PROMPT_VERSION,
+    build_user_message,
+    normalize_alias_item,
+    parse_canon_output,
+)
+
+DEFAULT_BASE_URL = os.environ.get("ATOCORE_BASE_URL", "http://127.0.0.1:8100")
+DEFAULT_MODEL = os.environ.get("ATOCORE_TAG_CANON_MODEL", "sonnet")
+DEFAULT_TIMEOUT_S = float(os.environ.get("ATOCORE_TAG_CANON_TIMEOUT_S", "90"))
+
+AUTO_APPROVE_CONF = float(os.environ.get("ATOCORE_TAG_CANON_AUTO_APPROVE_CONF", "0.8"))
+MIN_ALIAS_COUNT = int(os.environ.get("ATOCORE_TAG_CANON_MIN_ALIAS_COUNT", "1"))
+
+_sandbox_cwd = None
+
+
+def get_sandbox_cwd() -> str:
+    global _sandbox_cwd
+    if _sandbox_cwd is None:
+        _sandbox_cwd = tempfile.mkdtemp(prefix="ato-tagcanon-")
+    return _sandbox_cwd
+
+
+def api_get(base_url: str, path: str) -> dict:
+    req = urllib.request.Request(f"{base_url}{path}")
+    with urllib.request.urlopen(req, timeout=30) as resp:
+        return json.loads(resp.read().decode("utf-8"))
+
+
+def api_post(base_url: str, path: str, body: dict | None = None) -> dict:
+    data = json.dumps(body or {}).encode("utf-8")
+    req = urllib.request.Request(
+        f"{base_url}{path}", method="POST",
+        headers={"Content-Type": "application/json"}, data=data,
+    )
+    with urllib.request.urlopen(req, timeout=30) as resp:
+        return json.loads(resp.read().decode("utf-8"))
+
+
+def call_claude(user_message: str, model: str, timeout_s: float) -> tuple[str | None, str | None]:
+    if not shutil.which("claude"):
+        return None, "claude CLI not available"
+    args = [
+        "claude", "-p",
+        "--model", model,
+        "--append-system-prompt", SYSTEM_PROMPT,
+        "--disable-slash-commands",
+        user_message,
+    ]
+    last_error = ""
+    for attempt in range(3):
+        if attempt > 0:
+            time.sleep(2 ** attempt)
+        try:
+            completed = subprocess.run(
+                args, capture_output=True, text=True,
+                timeout=timeout_s, cwd=get_sandbox_cwd(),
+                encoding="utf-8", errors="replace",
+            )
+        except subprocess.TimeoutExpired:
+            last_error = f"{model} timed out"
+            continue
+        except Exception as exc:
+            last_error = f"subprocess error: {exc}"
+            continue
+        if completed.returncode == 0:
+            return (completed.stdout or "").strip(), None
+        stderr = (completed.stderr or "").strip()[:200]
+        last_error = f"{model} exit {completed.returncode}: {stderr}"
+    return None, last_error
+
+
+def fetch_tag_distribution(base_url: str) -> dict[str, int]:
+    """Count tag occurrences across active memories (client-side)."""
+    try:
+        result = api_get(base_url, "/memory?active_only=true&limit=2000")
+    except Exception as e:
+        print(f"ERROR: could not fetch memories: {e}", file=sys.stderr)
+        return {}
+    mems = result.get("memories", [])
+    counts: dict[str, int] = {}
+    for m in mems:
+        tags = m.get("domain_tags") or []
+        if isinstance(tags, str):
+            try:
+                tags = json.loads(tags)
+            except Exception:
+                tags = []
+        if not isinstance(tags, list):
+            continue
+        for t in tags:
+            if not isinstance(t, str):
+                continue
+            key = t.strip().lower()
+            if key:
+                counts[key] = counts.get(key, 0) + 1
+    return counts
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser(description="Phase 7C tag canonicalization detector")
+    parser.add_argument("--base-url", default=DEFAULT_BASE_URL)
+    parser.add_argument("--model", default=DEFAULT_MODEL)
+    parser.add_argument("--timeout-s", type=float, default=DEFAULT_TIMEOUT_S)
+    parser.add_argument("--no-auto-approve", action="store_true",
+                        help="Disable autonomous apply; all proposals → human queue")
+    parser.add_argument("--dry-run", action="store_true",
+                        help="Print decisions without touching state")
+    args = parser.parse_args()
+
+    base = args.base_url.rstrip("/")
+    autonomous = not args.no_auto_approve
+
+    print(
+        f"canonicalize_tags {TAG_CANON_PROMPT_VERSION} | model={args.model} | "
+        f"autonomous={autonomous} | auto-approve conf>={AUTO_APPROVE_CONF}"
+    )
+
+    dist = fetch_tag_distribution(base)
+    print(f"tag distribution: {len(dist)} unique tags, "
+          f"{sum(dist.values())} total references")
+    if not dist:
+        print("no tags found — nothing to canonicalize")
+        return
+
+    user_msg = build_user_message(dist)
+    raw, err = call_claude(user_msg, args.model, args.timeout_s)
+    if err or raw is None:
+        print(f"ERROR: LLM call failed: {err}", file=sys.stderr)
+        return
+
+    aliases_raw = parse_canon_output(raw)
+    print(f"LLM returned {len(aliases_raw)} raw alias proposals")
+
+    auto_applied = 0
+    auto_skipped_missing_canonical = 0
+    proposals_created = 0
+    duplicates_skipped = 0
+
+    for item in aliases_raw:
+        norm = normalize_alias_item(item)
+        if norm is None:
+            continue
+        alias = norm["alias"]
+        canonical = norm["canonical"]
+        confidence = norm["confidence"]
+
+        alias_count = dist.get(alias, 0)
+        canonical_count = dist.get(canonical, 0)
+
+        # Sanity: alias must actually exist in the current distribution
+        if alias_count < MIN_ALIAS_COUNT:
+            print(f"  SKIP {alias!r} → {canonical!r}: alias not in distribution")
+            continue
+        if canonical_count == 0:
+            auto_skipped_missing_canonical += 1
+            print(f"  SKIP {alias!r} → {canonical!r}: canonical missing from distribution")
+            continue
+
+        label = f"{alias!r} ({alias_count}) → {canonical!r} ({canonical_count}) conf={confidence:.2f}"
+
+        auto_apply = autonomous and confidence >= AUTO_APPROVE_CONF
+        if auto_apply:
+            if args.dry_run:
+                auto_applied += 1
+                print(f"  [dry-run] would auto-apply: {label}")
+                continue
+            try:
+                result = api_post(base, "/admin/tags/aliases/apply", {
+                    "alias": alias, "canonical": canonical,
+                    "confidence": confidence, "reason": norm["reason"],
+                    "alias_count": alias_count, "canonical_count": canonical_count,
+                    "actor": "auto-tag-canon",
+                })
+                touched = result.get("memories_touched", 0)
+                auto_applied += 1
+                print(f"  ✅ auto-applied: {label} ({touched} memories)")
+            except Exception as e:
+                print(f"  ⚠️ auto-apply failed: {label} — {e}", file=sys.stderr)
+            time.sleep(0.2)
+            continue
+
+        # Lower confidence → human review
+        if args.dry_run:
+            proposals_created += 1
+            print(f"  [dry-run] would propose for review: {label}")
+            continue
+        try:
+            result = api_post(base, "/admin/tags/aliases/propose", {
+                "alias": alias, "canonical": canonical,
+                "confidence": confidence, "reason": norm["reason"],
+                "alias_count": alias_count, "canonical_count": canonical_count,
+            })
+            if result.get("proposal_id"):
+                proposals_created += 1
+                print(f"  → pending proposal: {label}")
+            else:
+                duplicates_skipped += 1
+                print(f"  (duplicate pending proposal): {label}")
+        except Exception as e:
+            print(f"  ⚠️ propose failed: {label} — {e}", file=sys.stderr)
+        time.sleep(0.2)
+
+    print(
+        f"\nsummary: proposals_seen={len(aliases_raw)} "
+        f"auto_applied={auto_applied} "
+        f"proposals_created={proposals_created} "
+        f"duplicates_skipped={duplicates_skipped} "
+        f"skipped_missing_canonical={auto_skipped_missing_canonical}"
+    )
+
+
+if __name__ == "__main__":
+    main()
diff --git a/src/atocore/api/routes.py b/src/atocore/api/routes.py
index f35c2a1..a38d04e 100644
--- a/src/atocore/api/routes.py
+++ b/src/atocore/api/routes.py
@@ -1517,6 +1517,125 @@ def api_graduation_status() -> dict:
     return out
 
 
+# --- Phase 7C: tag canonicalization ---
+
+
+class TagAliasProposalBody(BaseModel):
+    alias: str
+    canonical: str
+    confidence: float = 0.0
+    reason: str = ""
+    alias_count: int = 0
+    canonical_count: int = 0
+
+
+class TagAliasApplyBody(BaseModel):
+    alias: str
+    canonical: str
+    confidence: float = 0.9
+    reason: str = ""
+    alias_count: int = 0
+    canonical_count: int = 0
+    actor: str = "auto-tag-canon"
+
+
+class TagAliasResolveBody(BaseModel):
+    actor: str = "human-triage"
+
+
+@router.get("/admin/tags/distribution")
+def api_tag_distribution() -> dict:
+    """Current tag distribution across active memories (for UI / debug)."""
+    from atocore.memory.service import get_tag_distribution
+    dist = get_tag_distribution()
+    sorted_tags = sorted(dist.items(), key=lambda x: x[1], reverse=True)
+    return {"total_references": sum(dist.values()), "unique_tags": len(dist),
+            "tags": [{"tag": t, "count": c} for t, c in sorted_tags]}
+
+
+@router.get("/admin/tags/aliases")
+def api_list_tag_aliases(status: str = "pending", limit: int = 100) -> dict:
+    """List tag alias proposals (default: pending for review)."""
+    from atocore.memory.service import get_tag_alias_proposals
+    rows = get_tag_alias_proposals(status=status, limit=limit)
+    return {"proposals": rows, "count": len(rows)}
+
+
+@router.post("/admin/tags/aliases/propose")
+def api_propose_tag_alias(body: TagAliasProposalBody) -> dict:
+    """Submit a low-confidence alias proposal for human review."""
+    from atocore.memory.service import create_tag_alias_proposal
+    pid = create_tag_alias_proposal(
+        alias=body.alias, canonical=body.canonical,
+        confidence=body.confidence, alias_count=body.alias_count,
+        canonical_count=body.canonical_count, reason=body.reason,
+    )
+    if pid is None:
+        return {"proposal_id": None, "duplicate": True}
+    return {"proposal_id": pid, "duplicate": False}
+
+
+@router.post("/admin/tags/aliases/apply")
+def api_apply_tag_alias(body: TagAliasApplyBody) -> dict:
+    """Apply an alias rewrite directly (used by the auto-approval path).
+
+    Creates a tag_aliases row in status=approved with the apply result
+    recorded, so autonomous merges land in the same audit surface as
+    human approvals.
+    """
+    from datetime import datetime as _dt, timezone as _tz
+
+    from atocore.memory.service import apply_tag_alias, create_tag_alias_proposal
+    from atocore.models.database import get_connection
+
+    # Record proposal + apply + mark approved in one flow
+    pid = create_tag_alias_proposal(
+        alias=body.alias, canonical=body.canonical,
+        confidence=body.confidence, alias_count=body.alias_count,
+        canonical_count=body.canonical_count, reason=body.reason,
+    )
+    if pid is None:
+        # A pending proposal already exists — don't double-apply.
+        raise HTTPException(status_code=409, detail="A pending proposal already exists for this (alias, canonical) pair — approve it via /admin/tags/aliases/{id}/approve")
+    try:
+        result = apply_tag_alias(body.alias, body.canonical, actor=body.actor)
+    except ValueError as e:
+        raise HTTPException(status_code=400, detail=str(e))
+
+    now_str = _dt.now(_tz.utc).strftime("%Y-%m-%d %H:%M:%S")
+    with get_connection() as conn:
+        conn.execute(
+            "UPDATE tag_aliases SET status = 'approved', resolved_at = ?, "
+            "resolved_by = ?, applied_to_memories = ? WHERE id = ?",
+            (now_str, body.actor, result["memories_touched"], pid),
+        )
+    return {
+        "proposal_id": pid,
+        "memories_touched": result["memories_touched"],
+        "alias": body.alias, "canonical": body.canonical,
+    }
+
+
+@router.post("/admin/tags/aliases/{proposal_id}/approve")
+def api_approve_tag_alias(proposal_id: str, body: TagAliasResolveBody) -> dict:
+    """Human-in-the-loop approve for a pending proposal."""
+    from atocore.memory.service import approve_tag_alias
+    result = approve_tag_alias(proposal_id, actor=body.actor)
+    if result is None:
+        raise HTTPException(status_code=404, detail="Proposal not found or already resolved")
+    return {"status": "approved", "proposal_id": proposal_id,
+            "memories_touched": result["memories_touched"]}
+
+
+@router.post("/admin/tags/aliases/{proposal_id}/reject")
+def api_reject_tag_alias(proposal_id: str, body: TagAliasResolveBody) -> dict:
+    """Human-in-the-loop reject for a pending proposal."""
+    from atocore.memory.service import reject_tag_alias
+    if not reject_tag_alias(proposal_id, actor=body.actor):
+        raise HTTPException(status_code=404, detail="Proposal not found or already resolved")
+    return {"status": "rejected", "proposal_id": proposal_id}
+
+
 class DecayRunBody(BaseModel):
     idle_days_threshold: int = 30
     daily_decay_factor: float = 0.97
diff --git a/src/atocore/memory/_tag_canon_prompt.py b/src/atocore/memory/_tag_canon_prompt.py
new file mode 100644
index 0000000..5104afe
--- /dev/null
+++ b/src/atocore/memory/_tag_canon_prompt.py
@@ -0,0 +1,158 @@
+"""Shared LLM prompt + parser for tag canonicalization (Phase 7C).
+
+Stdlib-only, importable from both the in-container service layer and the
+host-side batch script that shells out to ``claude -p``.
+
+The prompt instructs the model to propose a map of domain_tag aliases
+to their canonical form. Confidence is key here — we AUTO-APPLY high-
+confidence aliases; low-confidence go to human review. Over-merging
+distinct concepts ("optics" vs "optical" — sometimes equivalent,
+sometimes not) destroys cross-cutting retrieval, so the model is
+instructed to err conservative.
+"""
+
+from __future__ import annotations
+
+import json
+from typing import Any
+
+TAG_CANON_PROMPT_VERSION = "tagcanon-0.1.0"
+MAX_TAGS_IN_PROMPT = 100
+
+SYSTEM_PROMPT = """You canonicalize domain tags for AtoCore's memory layer.
+
+Input: a distribution of lowercase domain tags (keyword → usage count across active memories). Examples: "firmware: 23", "fw: 5", "firmware-control: 3", "optics: 18", "optical: 2".
+
+Your job: identify aliases — distinct strings that refer to the SAME concept — and map them to a single canonical form. The canonical should be the clearest / most-used / most-descriptive variant.
+
+STRICT RULES:
+
+1. ONLY propose aliases that are UNAMBIGUOUSLY equivalent. Examples:
+     - "fw" → "firmware" (abbreviation)
+     - "firmware-control" → "firmware" (compound narrowing — only if usage context makes it clear the narrower one is never used to DISTINGUISH from firmware-in-general)
+     - "py" → "python"
+     - "ml" → "machine-learning"
+   Do NOT merge:
+     - "optics" vs "optical" — these CAN diverge ("optics" = subsystem/product domain; "optical" = adjective used in non-optics contexts)
+     - "p04" vs "p04-gigabit" — project ids are their own namespace, never canonicalize
+     - "thermal" vs "temperature" — related but distinct
+     - Anything where you're not sure — skip it, human review will catch real aliases next week
+
+2. Confidence scale:
+     0.9+  obvious abbreviation, very high usage disparity, no plausible alternative meaning
+     0.7-0.9  likely alias, one-word-diff or standard contraction
+     0.5-0.7  plausible but requires context — low count on alias side
+     <0.5    DO NOT PROPOSE — if you're under 0.5, skip the pair entirely
+   AtoCore auto-applies aliases at confidence >= 0.8; anything below goes to human review.
+
+3. The CANONICAL must actually appear in the input list (don't invent a new term).
+
+4. Never propose `alias == canonical`. Never propose circular mappings.
+
+5. Project tags (p04, p05, p06, abb-space, atomizer-v2, atocore, apm) are OFF LIMITS — they are project identifiers, not concepts. Leave them alone entirely.
+
+OUTPUT — raw JSON, no prose, no markdown fences:
+{
+  "aliases": [
+    {"alias": "fw", "canonical": "firmware", "confidence": 0.95, "reason": "fw is a standard abbreviation of firmware; 5 uses vs 23"},
+    {"alias": "ml", "canonical": "machine-learning", "confidence": 0.90, "reason": "ml is the universal abbreviation"}
+  ]
+}
+
+Empty aliases list is fine if nothing in the distribution is a clear alias. Err conservative — one false merge can pollute retrieval for hundreds of memories."""
+
+
+def build_user_message(tag_distribution: dict[str, int]) -> str:
+    """Format the tag distribution for the model.
+
+    Limited to MAX_TAGS_IN_PROMPT entries, sorted by count descending
+    so high-usage tags appear first (the LLM uses them as anchor points
+    for canonical selection).
+    """
+    if not tag_distribution:
+        return "Empty tag distribution — return {\"aliases\": []}."
+
+    sorted_tags = sorted(tag_distribution.items(), key=lambda x: x[1], reverse=True)
+    top = sorted_tags[:MAX_TAGS_IN_PROMPT]
+    lines = [f"{tag}: {count}" for tag, count in top]
+    return (
+        f"Tag distribution across {sum(tag_distribution.values())} total tag references "
+        f"(showing top {len(top)} of {len(tag_distribution)} unique tags):\n\n"
+        + "\n".join(lines)
+        + "\n\nReturn the JSON aliases map now. Only propose UNAMBIGUOUS equivalents."
+    )
+
+
+def parse_canon_output(raw_output: str) -> list[dict[str, Any]]:
+    """Strip markdown fences / prose and return the parsed aliases list."""
+    text = (raw_output or "").strip()
+    if text.startswith("```"):
+        text = text.strip("`")
+        nl = text.find("\n")
+        if nl >= 0:
+            text = text[nl + 1:]
+        if text.endswith("```"):
+            text = text[:-3]
+        text = text.strip()
+
+    if not text.lstrip().startswith("{"):
+        start = text.find("{")
+        end = text.rfind("}")
+        if start >= 0 and end > start:
+            text = text[start:end + 1]
+
+    try:
+        parsed = json.loads(text)
+    except json.JSONDecodeError:
+        return []
+
+    if not isinstance(parsed, dict):
+        return []
+    aliases = parsed.get("aliases") or []
+    if not isinstance(aliases, list):
+        return []
+    return [a for a in aliases if isinstance(a, dict)]
+
+
+# Project tokens that must never be canonicalized — they're project ids,
+# not concepts. Keep this list in sync with the registered projects.
+# Safe to be over-inclusive; extra entries just skip canonicalization.
+PROTECTED_PROJECT_TOKENS = frozenset({
+    "p04", "p04-gigabit",
+    "p05", "p05-interferometer",
+    "p06", "p06-polisher",
+    "p08", "abb-space",
+    "atomizer", "atomizer-v2",
+    "atocore", "apm",
+})
+
+
+def normalize_alias_item(item: dict[str, Any]) -> dict[str, Any] | None:
+    """Validate one raw alias proposal. Returns None if unusable.
+
+    Filters: non-strings, empty strings, identity mappings, protected
+    project tokens on either side.
+    """
+    alias = str(item.get("alias") or "").strip().lower()
+    canonical = str(item.get("canonical") or "").strip().lower()
+    if not alias or not canonical:
+        return None
+    if alias == canonical:
+        return None
+    if alias in PROTECTED_PROJECT_TOKENS or canonical in PROTECTED_PROJECT_TOKENS:
+        return None
+
+    try:
+        confidence = float(item.get("confidence", 0.0))
+    except (TypeError, ValueError):
+        confidence = 0.0
+    confidence = max(0.0, min(1.0, confidence))
+
+    reason = str(item.get("reason") or "").strip()[:300]
+
+    return {
+        "alias": alias,
+        "canonical": canonical,
+        "confidence": confidence,
+        "reason": reason,
+    }
diff --git a/src/atocore/memory/service.py b/src/atocore/memory/service.py
index d62a853..caab3b4 100644
--- a/src/atocore/memory/service.py
+++ b/src/atocore/memory/service.py
@@ -1038,6 +1038,224 @@ def _validate_confidence(confidence: float) -> None:
         raise ValueError("Confidence must be between 0.0 and 1.0")
 
 
+# ---------------------------------------------------------------------
+# Phase 7C — Tag canonicalization
+# ---------------------------------------------------------------------
+
+
+def get_tag_distribution(
+    active_only: bool = True,
+    min_count: int = 1,
+) -> dict[str, int]:
+    """Return {tag: occurrence_count} across memories for LLM input.
+
+    Used by the canonicalization detector to spot alias clusters like
+    {firmware: 23, fw: 5, firmware-control: 3}. Only counts memories
+    in the requested status (active by default) so superseded/invalid
+    rows don't bias the distribution.
+    """
+    import json as _json
+    counts: dict[str, int] = {}
+    query = "SELECT domain_tags FROM memories"
+    if active_only:
+        query += " WHERE status = 'active'"
+    with get_connection() as conn:
+        rows = conn.execute(query).fetchall()
+    for r in rows:
+        tags_raw = r["domain_tags"]
+        try:
+            tags = _json.loads(tags_raw) if tags_raw else []
+        except Exception:
+            tags = []
+        if not isinstance(tags, list):
+            continue
+        for t in tags:
+            if not isinstance(t, str):
+                continue
+            key = t.strip().lower()
+            if key:
+                counts[key] = counts.get(key, 0) + 1
+    if min_count > 1:
+        counts = {k: v for k, v in counts.items() if v >= min_count}
+    return counts
+
+
+def apply_tag_alias(
+    alias: str,
+    canonical: str,
+    actor: str = "tag-canon",
+) -> dict:
+    """Rewrite every active memory's domain_tags: alias → canonical.
+
+    Atomic per-memory. Dedupes within each memory's tag list (so if a
+    memory already has both alias AND canonical, we drop the alias and
+    keep canonical without duplicating). Writes one audit row per
+    touched memory with action="tag_canonicalized" so the full trail
+    is recoverable.
+
+    Returns {"memories_touched": int, "alias": ..., "canonical": ...}.
+    """
+    import json as _json
+    alias = (alias or "").strip().lower()
+    canonical = (canonical or "").strip().lower()
+    if not alias or not canonical:
+        raise ValueError("alias and canonical must be non-empty")
+    if alias == canonical:
+        raise ValueError("alias cannot equal canonical")
+
+    touched: list[tuple[str, list[str], list[str]]] = []
+
+    with get_connection() as conn:
+        rows = conn.execute(
+            "SELECT id, domain_tags FROM memories WHERE status = 'active'"
+        ).fetchall()
+
+        for r in rows:
+            raw = r["domain_tags"]
+            try:
+                tags = _json.loads(raw) if raw else []
+            except Exception:
+                tags = []
+            if not isinstance(tags, list):
+                continue
+            if alias not in tags:
+                continue
+
+            old_tags = [t for t in tags if isinstance(t, str)]
+            new_tags: list[str] = []
+            for t in old_tags:
+                rewritten = canonical if t == alias else t
+                if rewritten not in new_tags:
+                    new_tags.append(rewritten)
+            if new_tags == old_tags:
+                continue
+            conn.execute(
+                "UPDATE memories SET domain_tags = ?, updated_at = CURRENT_TIMESTAMP "
+                "WHERE id = ?",
+                (_json.dumps(new_tags), r["id"]),
+            )
+            touched.append((r["id"], old_tags, new_tags))
+
+    # Audit rows outside the transaction
+    for mem_id, old_tags, new_tags in touched:
+        _audit_memory(
+            memory_id=mem_id,
+            action="tag_canonicalized",
+            actor=actor,
+            before={"domain_tags": old_tags},
+            after={"domain_tags": new_tags},
+            note=f"{alias} → {canonical}",
+        )
+
+    if touched:
+        log.info("tag_alias_applied", alias=alias, canonical=canonical, memories_touched=len(touched))
+    return {
+        "memories_touched": len(touched),
+        "alias": alias,
+        "canonical": canonical,
+    }
+
+
+def create_tag_alias_proposal(
+    alias: str,
+    canonical: str,
+    confidence: float,
+    alias_count: int = 0,
+    canonical_count: int = 0,
+    reason: str = "",
+) -> str | None:
+    """Insert a tag_aliases row in status=pending.
+
+    Idempotent: if a pending proposal for (alias, canonical) already
+    exists, returns None.
+    """
+    import json as _json  # noqa: F401 — kept for parity with other helpers
+    alias = (alias or "").strip().lower()
+    canonical = (canonical or "").strip().lower()
+    if not alias or not canonical or alias == canonical:
+        return None
+    confidence = max(0.0, min(1.0, float(confidence)))
+
+    proposal_id = str(uuid.uuid4())
+    with get_connection() as conn:
+        existing = conn.execute(
+            "SELECT id FROM tag_aliases WHERE alias = ? AND canonical = ? "
+            "AND status = 'pending'",
+            (alias, canonical),
+        ).fetchone()
+        if existing:
+            return None
+
+        conn.execute(
+            "INSERT INTO tag_aliases (id, alias, canonical, status, confidence, "
+            "alias_count, canonical_count, reason) "
+            "VALUES (?, ?, ?, 'pending', ?, ?, ?, ?)",
+            (proposal_id, alias, canonical, confidence,
+             int(alias_count), int(canonical_count), reason[:500]),
+        )
+    log.info(
+        "tag_alias_proposed",
+        proposal_id=proposal_id,
+        alias=alias,
+        canonical=canonical,
+        confidence=round(confidence, 3),
+    )
+    return proposal_id
+
+
+def get_tag_alias_proposals(status: str = "pending", limit: int = 100) -> list[dict]:
+    """List tag alias proposals."""
+    with get_connection() as conn:
+        rows = conn.execute(
+            "SELECT * FROM tag_aliases WHERE status = ? "
+            "ORDER BY confidence DESC, created_at DESC LIMIT ?",
+            (status, limit),
+        ).fetchall()
+    return [dict(r) for r in rows]
+
+
+def approve_tag_alias(
+    proposal_id: str,
+    actor: str = "human-triage",
+) -> dict | None:
+    """Apply the alias rewrite + mark the proposal approved.
+
+    Returns the apply_tag_alias result dict, or None if the proposal
+    is not found or already resolved.
+    """
+    now_str = datetime.now(timezone.utc).strftime("%Y-%m-%d %H:%M:%S")
+    with get_connection() as conn:
+        row = conn.execute(
+            "SELECT alias, canonical, status FROM tag_aliases WHERE id = ?",
+            (proposal_id,),
+        ).fetchone()
+        if row is None or row["status"] != "pending":
+            return None
+        alias, canonical = row["alias"], row["canonical"]
+
+    result = apply_tag_alias(alias, canonical, actor=actor)
+
+    with get_connection() as conn:
+        conn.execute(
+            "UPDATE tag_aliases SET status = 'approved', resolved_at = ?, "
+            "resolved_by = ?, applied_to_memories = ? WHERE id = ?",
+            (now_str, actor, result["memories_touched"], proposal_id),
+        )
+    return result
+
+
+def reject_tag_alias(proposal_id: str, actor: str = "human-triage") -> bool:
+    """Mark a tag alias proposal as rejected without applying it."""
+    now_str = datetime.now(timezone.utc).strftime("%Y-%m-%d %H:%M:%S")
+    with get_connection() as conn:
+        result = conn.execute(
+            "UPDATE tag_aliases SET status = 'rejected', resolved_at = ?, "
+            "resolved_by = ? WHERE id = ? AND status = 'pending'",
+            (now_str, actor, proposal_id),
+        )
+        return result.rowcount > 0
+
+
 # ---------------------------------------------------------------------
 # Phase 7A — Memory Consolidation: merge-candidate lifecycle
 # ---------------------------------------------------------------------
diff --git a/src/atocore/models/database.py b/src/atocore/models/database.py
index b9605ec..0f11187 100644
--- a/src/atocore/models/database.py
+++ b/src/atocore/models/database.py
@@ -287,6 +287,33 @@ def _apply_migrations(conn: sqlite3.Connection) -> None:
         "CREATE INDEX IF NOT EXISTS idx_mmc_created_at ON memory_merge_candidates(created_at)"
     )
 
+    # Phase 7C (Memory Consolidation — tag canonicalization): alias → canonical
+    # map for domain_tags. A weekly LLM pass proposes rows here; high-confidence
+    # ones auto-apply (rewrite domain_tags across all memories), low-confidence
+    # ones stay pending for human approval. Immutable history: resolved rows
+    # keep status=approved/rejected; the same alias can re-appear with a new
+    # id if the tag reaches a different canonical later.
+    conn.execute(
+        """
+        CREATE TABLE IF NOT EXISTS tag_aliases (
+            id TEXT PRIMARY KEY,
+            alias TEXT NOT NULL,
+            canonical TEXT NOT NULL,
+            status TEXT DEFAULT 'pending',
+            confidence REAL DEFAULT 0.0,
+            alias_count INTEGER DEFAULT 0,
+            canonical_count INTEGER DEFAULT 0,
+            reason TEXT DEFAULT '',
+            applied_to_memories INTEGER DEFAULT 0,
+            created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+            resolved_at DATETIME,
+            resolved_by TEXT
+        )
+        """
+    )
+    conn.execute("CREATE INDEX IF NOT EXISTS idx_tag_aliases_status ON tag_aliases(status)")
+    conn.execute("CREATE INDEX IF NOT EXISTS idx_tag_aliases_alias ON tag_aliases(alias)")
+
 
 def _column_exists(conn: sqlite3.Connection, table: str, column: str) -> bool:
     rows = conn.execute(f"PRAGMA table_info({table})").fetchall()
diff --git a/tests/test_tag_canon.py b/tests/test_tag_canon.py
new file mode 100644
index 0000000..f08bfc5
--- /dev/null
+++ b/tests/test_tag_canon.py
@@ -0,0 +1,296 @@
+"""Phase 7C — tag canonicalization tests.
+
+Covers:
+  - prompt parser (fences, prose, empty)
+  - normalizer (identity, protected tokens, empty)
+  - get_tag_distribution counts across active memories
+  - apply_tag_alias rewrites + dedupes + audits
+  - create / approve / reject lifecycle
+  - idempotency (dup proposals skipped)
+"""
+
+from __future__ import annotations
+
+import pytest
+
+from atocore.memory._tag_canon_prompt import (
+    PROTECTED_PROJECT_TOKENS,
+    build_user_message,
+    normalize_alias_item,
+    parse_canon_output,
+)
+from atocore.memory.service import (
+    apply_tag_alias,
+    approve_tag_alias,
+    create_memory,
+    create_tag_alias_proposal,
+    get_memory_audit,
+    get_tag_alias_proposals,
+    get_tag_distribution,
+    reject_tag_alias,
+)
+from atocore.models.database import get_connection, init_db
+
+
+# --- Prompt parser ---
+
+
+def test_parse_canon_output_handles_fences():
+    raw = "```json\n{\"aliases\": [{\"alias\": \"fw\", \"canonical\": \"firmware\", \"confidence\": 0.9}]}\n```"
+    items = parse_canon_output(raw)
+    assert len(items) == 1
+    assert items[0]["alias"] == "fw"
+
+
+def test_parse_canon_output_handles_prose_prefix():
+    raw = "Here you go:\n{\"aliases\": [{\"alias\": \"ml\", \"canonical\": \"machine-learning\", \"confidence\": 0.9}]}"
+    items = parse_canon_output(raw)
+    assert len(items) == 1
+
+
+def test_parse_canon_output_empty_list():
+    assert parse_canon_output("{\"aliases\": []}") == []
+
+
+def test_parse_canon_output_malformed():
+    assert parse_canon_output("not json at all") == []
+    assert parse_canon_output("") == []
+
+
+# --- Normalizer ---
+
+
+def test_normalize_alias_strips_and_lowercases():
+    n = normalize_alias_item({"alias": " FW ", "canonical": "Firmware", "confidence": 0.95, "reason": "abbrev"})
+    assert n == {"alias": "fw", "canonical": "firmware", "confidence": 0.95, "reason": "abbrev"}
+
+
+def test_normalize_rejects_identity():
+    assert normalize_alias_item({"alias": "foo", "canonical": "foo", "confidence": 0.9}) is None
+
+
+def test_normalize_rejects_empty():
+    assert normalize_alias_item({"alias": "", "canonical": "foo", "confidence": 0.9}) is None
+    assert normalize_alias_item({"alias": "foo", "canonical": "", "confidence": 0.9}) is None
+
+
+def test_normalize_protects_project_tokens():
+    # Project ids must not be canonicalized — they're their own namespace
+    assert "p04" in PROTECTED_PROJECT_TOKENS
+    assert normalize_alias_item({"alias": "p04", "canonical": "p04-gigabit", "confidence": 1.0}) is None
+    assert normalize_alias_item({"alias": "p04-gigabit", "canonical": "p04", "confidence": 1.0}) is None
+    assert normalize_alias_item({"alias": "apm", "canonical": "part-manager", "confidence": 1.0}) is None
+
+
+def test_normalize_clamps_confidence():
+    hi = normalize_alias_item({"alias": "a", "canonical": "b", "confidence": 2.5})
+    assert hi["confidence"] == 1.0
+    lo = normalize_alias_item({"alias": "a", "canonical": "b", "confidence": -0.5})
+    assert lo["confidence"] == 0.0
+
+
+def test_normalize_handles_non_numeric_confidence():
+    n = normalize_alias_item({"alias": "a", "canonical": "b", "confidence": "not a number"})
+    assert n is not None and n["confidence"] == 0.0
+
+
+# --- build_user_message ---
+
+
+def test_build_user_message_includes_top_tags():
+    dist = {"firmware": 23, "fw": 5, "optics": 18, "optical": 2}
+    msg = build_user_message(dist)
+    assert "firmware: 23" in msg
+    assert "optics: 18" in msg
+    assert "aliases" in msg.lower() or "JSON" in msg
+
+
+def test_build_user_message_empty():
+    msg = build_user_message({})
+    assert "Empty" in msg or "empty" in msg
+
+
+# --- get_tag_distribution ---
+
+
+def test_tag_distribution_counts_active_only(tmp_data_dir):
+    init_db()
+    create_memory("knowledge", "a", domain_tags=["firmware", "p06"])
+    create_memory("knowledge", "b", domain_tags=["firmware"])
+    create_memory("knowledge", "c", domain_tags=["optics"])
+
+    # Add an invalid memory — should NOT be counted
+    m_invalid = create_memory("knowledge", "d", domain_tags=["firmware", "ignored"])
+    with get_connection() as conn:
+        conn.execute("UPDATE memories SET status = 'invalid' WHERE id = ?", (m_invalid.id,))
+
+    dist = get_tag_distribution()
+    assert dist.get("firmware") == 2  # two active memories
+    assert dist.get("optics") == 1
+    assert dist.get("p06") == 1
+    assert "ignored" not in dist
+
+
+def test_tag_distribution_min_count_filter(tmp_data_dir):
+    init_db()
+    create_memory("knowledge", "a", domain_tags=["firmware"])
+    create_memory("knowledge", "b", domain_tags=["firmware"])
+    create_memory("knowledge", "c", domain_tags=["once"])
+
+    dist = get_tag_distribution(min_count=2)
+    assert "firmware" in dist
+    assert "once" not in dist
+
+
+# --- apply_tag_alias ---
+
+
+def test_apply_tag_alias_rewrites_across_memories(tmp_data_dir):
+    init_db()
+    m1 = create_memory("knowledge", "a", domain_tags=["fw", "p06"])
+    m2 = create_memory("knowledge", "b", domain_tags=["fw"])
+    m3 = create_memory("knowledge", "c", domain_tags=["optics"])  # untouched
+
+    result = apply_tag_alias("fw", "firmware")
+    assert result["memories_touched"] == 2
+
+    import json as _json
+    with get_connection() as conn:
+        r1 = conn.execute("SELECT domain_tags FROM memories WHERE id = ?", (m1.id,)).fetchone()
+        r2 = conn.execute("SELECT domain_tags FROM memories WHERE id = ?", (m2.id,)).fetchone()
+        r3 = conn.execute("SELECT domain_tags FROM memories WHERE id = ?", (m3.id,)).fetchone()
+    assert "firmware" in _json.loads(r1["domain_tags"])
+    assert "fw" not in _json.loads(r1["domain_tags"])
+    assert "firmware" in _json.loads(r2["domain_tags"])
+    assert _json.loads(r3["domain_tags"]) == ["optics"]  # untouched
+
+
+def test_apply_tag_alias_dedupes_when_both_present(tmp_data_dir):
+    """Memory has both fw AND firmware → rewrite collapses to just firmware."""
+    init_db()
+    m = create_memory("knowledge", "dual-tagged", domain_tags=["fw", "firmware", "p06"])
+
+    result = apply_tag_alias("fw", "firmware")
+    assert result["memories_touched"] == 1
+
+    import json as _json
+    with get_connection() as conn:
+        r = conn.execute("SELECT domain_tags FROM memories WHERE id = ?", (m.id,)).fetchone()
+    tags = _json.loads(r["domain_tags"])
+    assert tags.count("firmware") == 1
+    assert "fw" not in tags
+    assert "p06" in tags
+
+
+def test_apply_tag_alias_skips_memories_without_alias(tmp_data_dir):
+    init_db()
+    m = create_memory("knowledge", "no match", domain_tags=["optics", "p04"])
+    result = apply_tag_alias("fw", "firmware")
+    assert result["memories_touched"] == 0
+
+
+def test_apply_tag_alias_writes_audit(tmp_data_dir):
+    init_db()
+    m = create_memory("knowledge", "audited", domain_tags=["fw"])
+    apply_tag_alias("fw", "firmware", actor="auto-tag-canon")
+
+    audit = get_memory_audit(m.id)
+    actions = [a["action"] for a in audit]
+    assert "tag_canonicalized" in actions
+    entry = next(a for a in audit if a["action"] == "tag_canonicalized")
+    assert entry["actor"] == "auto-tag-canon"
+    assert "fw → firmware" in entry["note"]
+    assert "fw" in entry["before"]["domain_tags"]
+    assert "firmware" in entry["after"]["domain_tags"]
+
+
+def test_apply_tag_alias_rejects_identity(tmp_data_dir):
+    init_db()
+    with pytest.raises(ValueError):
+        apply_tag_alias("foo", "foo")
+
+
+def test_apply_tag_alias_rejects_empty(tmp_data_dir):
+    init_db()
+    with pytest.raises(ValueError):
+        apply_tag_alias("", "firmware")
+
+
+# --- Proposal lifecycle ---
+
+
+def test_create_proposal_inserts_pending(tmp_data_dir):
+    init_db()
+    pid = create_tag_alias_proposal("fw", "firmware", confidence=0.65,
+                                    alias_count=5, canonical_count=23,
+                                    reason="standard abbreviation")
+    assert pid is not None
+
+    rows = get_tag_alias_proposals(status="pending")
+    assert len(rows) == 1
+    assert rows[0]["alias"] == "fw"
+    assert rows[0]["confidence"] == pytest.approx(0.65)
+
+
+def test_create_proposal_idempotent(tmp_data_dir):
+    init_db()
+    first = create_tag_alias_proposal("fw", "firmware", confidence=0.6)
+    second = create_tag_alias_proposal("fw", "firmware", confidence=0.7)
+    assert first is not None
+    assert second is None
+
+
+def test_approve_applies_rewrite(tmp_data_dir):
+    init_db()
+    m = create_memory("knowledge", "x", domain_tags=["fw"])
+    pid = create_tag_alias_proposal("fw", "firmware", confidence=0.7)
+    result = approve_tag_alias(pid, actor="human-triage")
+    assert result is not None
+    assert result["memories_touched"] == 1
+
+    # Proposal now approved with applied_to_memories recorded
+    rows = get_tag_alias_proposals(status="approved")
+    assert len(rows) == 1
+    assert rows[0]["applied_to_memories"] == 1
+
+    # Memory actually rewritten
+    import json as _json
+    with get_connection() as conn:
+        r = conn.execute("SELECT domain_tags FROM memories WHERE id = ?", (m.id,)).fetchone()
+    assert "firmware" in _json.loads(r["domain_tags"])
+
+
+def test_approve_already_resolved_returns_none(tmp_data_dir):
+    init_db()
+    pid = create_tag_alias_proposal("a", "b", confidence=0.6)
+    approve_tag_alias(pid)
+    assert approve_tag_alias(pid) is None  # second approve — no-op
+
+
+def test_reject_leaves_memories_untouched(tmp_data_dir):
+    init_db()
+    m = create_memory("knowledge", "x", domain_tags=["fw"])
+    pid = create_tag_alias_proposal("fw", "firmware", confidence=0.6)
+    assert reject_tag_alias(pid)
+
+    rows = get_tag_alias_proposals(status="rejected")
+    assert len(rows) == 1
+
+    # Memory still has the original tag
+    import json as _json
+    with get_connection() as conn:
+        r = conn.execute("SELECT domain_tags FROM memories WHERE id = ?", (m.id,)).fetchone()
+    assert "fw" in _json.loads(r["domain_tags"])
+
+
+# --- Schema sanity ---
+
+
+def test_tag_aliases_table_exists(tmp_data_dir):
+    init_db()
+    with get_connection() as conn:
+        cols = [r["name"] for r in conn.execute("PRAGMA table_info(tag_aliases)").fetchall()]
+    expected = {"id", "alias", "canonical", "status", "confidence",
+                "alias_count", "canonical_count", "reason",
+                "applied_to_memories", "created_at", "resolved_at", "resolved_by"}
+    assert expected.issubset(set(cols))