diff --git a/.agents/configs/fallback-chain-config.json.txt b/.agents/configs/fallback-chain-config.json.txt
new file mode 100644
index 00000000..66085831
--- /dev/null
+++ b/.agents/configs/fallback-chain-config.json.txt
@@ -0,0 +1,112 @@
+{
+  "_comment": "Fallback Chain Configuration - Global defaults for model fallback chains",
+  "_docs": "See .agents/tools/ai-assistants/fallback-chains.md for full documentation",
+
+  "chains": {
+    "_comment": "Per-tier fallback chains. Models tried in order. Formats: provider/model, openrouter/provider/model, gateway/cf/provider/model",
+
+    "haiku": [
+      "anthropic/claude-3-5-haiku-20241022",
+      "google/gemini-2.5-flash",
+      "openrouter/anthropic/claude-3-5-haiku-20241022"
+    ],
+    "flash": [
+      "google/gemini-2.5-flash",
+      "openai/gpt-4.1-mini",
+      "openrouter/google/gemini-2.5-flash"
+    ],
+    "sonnet": [
+      "anthropic/claude-sonnet-4-20250514",
+      "openai/gpt-4.1",
+      "google/gemini-2.5-pro",
+      "openrouter/anthropic/claude-sonnet-4-20250514"
+    ],
+    "pro": [
+      "google/gemini-2.5-pro",
+      "anthropic/claude-sonnet-4-20250514",
+      "openrouter/google/gemini-2.5-pro"
+    ],
+    "opus": [
+      "anthropic/claude-opus-4-6",
+      "openai/o3",
+      "openrouter/anthropic/claude-opus-4-6"
+    ],
+    "coding": [
+      "anthropic/claude-opus-4-6",
+      "openai/o3",
+      "anthropic/claude-sonnet-4-20250514",
+      "openrouter/anthropic/claude-opus-4-6"
+    ],
+    "eval": [
+      "anthropic/claude-sonnet-4-5",
+      "google/gemini-2.5-flash",
+      "openrouter/anthropic/claude-sonnet-4-5"
+    ],
+    "health": [
+      "anthropic/claude-sonnet-4-5",
+      "google/gemini-2.5-flash"
+    ],
+
+    "default": [
+      "anthropic/claude-sonnet-4-20250514",
+      "openai/gpt-4.1",
+      "google/gemini-2.5-pro",
+      "openrouter/anthropic/claude-sonnet-4-20250514"
+    ]
+  },
+
+  "triggers": {
+    "_comment": "Trigger configuration. Each trigger type can be enabled/disabled with custom cooldown.",
+
+    "api_error": {
+      "enabled": true,
+      "cooldown_seconds": 300,
+      "description": "Provider returned 5xx or connection failure"
+    },
+    "timeout": {
+      "enabled": true,
+      "cooldown_seconds": 180,
+      "description": "Request exceeded timeout threshold"
+    },
+    "rate_limit": {
+      "enabled": true,
+      "cooldown_seconds": 60,
+      "description": "Provider returned 429 (rate limited)"
+    },
+    "auth_error": {
+      "enabled": true,
+      "cooldown_seconds": 3600,
+      "description": "Provider returned 401/403 (key invalid or expired)"
+    },
+    "overloaded": {
+      "enabled": true,
+      "cooldown_seconds": 120,
+      "description": "Provider returned 529 (overloaded)"
+    }
+  },
+
+  "gateways": {
+    "_comment": "Gateway provider configuration for provider-level fallback routing",
+
+    "openrouter": {
+      "enabled": true,
+      "endpoint": "https://openrouter.ai/api/v1",
+      "key_env_var": "OPENROUTER_API_KEY",
+      "description": "OpenRouter - multi-provider gateway with unified API"
+    },
+    "cloudflare": {
+      "enabled": false,
+      "account_id": "YOUR_CF_ACCOUNT_ID_HERE",
+      "gateway_id": "YOUR_CF_GATEWAY_ID_HERE",
+      "key_env_var": "CF_AIG_TOKEN",
+      "description": "Cloudflare AI Gateway - caching, rate limiting, analytics"
+    }
+  },
+
+  "settings": {
+    "max_chain_depth": 5,
+    "default_cooldown_seconds": 300,
+    "probe_timeout_seconds": 10,
+    "log_retention_days": 30
+  }
+}
diff --git a/.agents/scripts/fallback-chain-helper.sh b/.agents/scripts/fallback-chain-helper.sh
new file mode 100755
index 00000000..5df24f12
--- /dev/null
+++ b/.agents/scripts/fallback-chain-helper.sh
@@ -0,0 +1,1304 @@
+#!/usr/bin/env bash
+# shellcheck disable=SC1091
+
+# Fallback Chain Helper - Per-agent and global model fallback chain resolution
+# Resolves the best available model through a configurable chain of providers,
+# with trigger-based activation on API errors, timeouts, and rate limits.
+# Supports gateway providers (Cloudflare AI Gateway, OpenRouter) for
+# provider-level fallback without per-provider API keys.
+#
+# Usage: fallback-chain-helper.sh [command] [options]
+#
+# Commands:
+#   resolve <tier>          Resolve best model through fallback chain
+#   trigger <tier> <error>  Process an error trigger and return next fallback
+#   chain <tier>            Show the full fallback chain for a tier
+#   status                  Show fallback chain health across all tiers
+#   validate                Validate fallback chain configuration
+#   gateway <provider>      Check gateway provider availability
+#   help                    Show this help
+#
+# Options:
+#   --config PATH     Override config file path
+#   --agent FILE      Use per-agent fallback chain from frontmatter
+#   --json            Output in JSON format
+#   --quiet           Suppress informational output
+#   --force           Bypass cache
+#   --max-depth N     Maximum chain depth (default: 5)
+#
+# Trigger types:
+#   api_error         Provider returned 5xx or connection failure
+#   timeout           Request exceeded timeout threshold
+#   rate_limit        Provider returned 429 (rate limited)
+#   auth_error        Provider returned 401/403 (key invalid)
+#   overloaded        Provider returned 529 (overloaded)
+#
+# Exit codes:
+#   0 - Model resolved successfully
+#   1 - No available model in chain
+#   2 - Configuration error
+#   3 - All providers exhausted
+#
+# Author: AI DevOps Framework
+# Version: 1.0.0
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)" || exit
+source "${SCRIPT_DIR}/shared-constants.sh"
+
+set -euo pipefail
+
+init_log_file
+
+# =============================================================================
+# Configuration
+# =============================================================================
+
+readonly FALLBACK_DIR="${HOME}/.aidevops/.agent-workspace"
+readonly FALLBACK_DB="${FALLBACK_DIR}/fallback-chain.db"
+readonly DEFAULT_CONFIG="${SCRIPT_DIR}/../configs/fallback-chain-config.json"
+readonly AVAILABILITY_HELPER="${SCRIPT_DIR}/model-availability-helper.sh"
+readonly DEFAULT_MAX_DEPTH=5
+readonly COOLDOWN_SECONDS=300  # 5 minutes before retrying a failed provider
+readonly GATEWAY_PROBE_TIMEOUT=10
+
+# =============================================================================
+# Database Setup
+# =============================================================================
+
+init_db() {
+    mkdir -p "$FALLBACK_DIR" 2>/dev/null || true
+
+    sqlite3 "$FALLBACK_DB" "
+        PRAGMA journal_mode=WAL;
+        PRAGMA busy_timeout=5000;
+
+        CREATE TABLE IF NOT EXISTS trigger_log (
+            id             INTEGER PRIMARY KEY AUTOINCREMENT,
+            tier           TEXT NOT NULL,
+            trigger_type   TEXT NOT NULL,
+            failed_model   TEXT NOT NULL,
+            resolved_model TEXT DEFAULT '',
+            chain_depth    INTEGER DEFAULT 0,
+            details        TEXT DEFAULT '',
+            timestamp      TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%SZ', 'now'))
+        );
+
+        CREATE TABLE IF NOT EXISTS provider_cooldown (
+            provider       TEXT PRIMARY KEY,
+            reason         TEXT NOT NULL DEFAULT '',
+            cooldown_until TEXT NOT NULL,
+            created_at     TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%SZ', 'now'))
+        );
+
+        CREATE TABLE IF NOT EXISTS gateway_health (
+            gateway_id     TEXT PRIMARY KEY,
+            gateway_type   TEXT NOT NULL DEFAULT '',
+            status         TEXT NOT NULL DEFAULT 'unknown',
+            endpoint       TEXT DEFAULT '',
+            last_checked   TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),
+            response_ms    INTEGER DEFAULT 0,
+            error_message  TEXT DEFAULT ''
+        );
+
+        CREATE INDEX IF NOT EXISTS idx_trigger_log_tier ON trigger_log(tier);
+        CREATE INDEX IF NOT EXISTS idx_trigger_log_timestamp ON trigger_log(timestamp);
+    " >/dev/null 2>/dev/null || {
+        print_error "Failed to initialize fallback chain database"
+        return 1
+    }
+    return 0
+}
+
+db_query() {
+    local query="$1"
+    sqlite3 -cmd ".timeout 5000" "$FALLBACK_DB" "$query" 2>/dev/null
+    return $?
+}
+
+db_query_json() {
+    local query="$1"
+    sqlite3 -cmd ".timeout 5000" -json "$FALLBACK_DB" "$query" 2>/dev/null
+    return $?
+}
+
+sql_escape() {
+    local val="$1"
+    echo "${val//\'/\'\'}"
+    return 0
+}
+
+# =============================================================================
+# Configuration Loading
+# =============================================================================
+
+# Load fallback chain config from JSON file.
+# Supports both global config and per-agent overrides.
+load_config() {
+    local config_path="${1:-$DEFAULT_CONFIG}"
+
+    # Try working config first (with real credentials), then template
+    if [[ ! -f "$config_path" ]]; then
+        local template_path="${config_path%.json}.json.txt"
+        if [[ -f "$template_path" ]]; then
+            config_path="$template_path"
+        else
+            print_error "Fallback chain config not found: $config_path"
+            return 2
+        fi
+    fi
+
+    # Validate JSON
+    if ! jq empty "$config_path" 2>/dev/null; then
+        print_error "Invalid JSON in fallback chain config: $config_path"
+        return 2
+    fi
+
+    echo "$config_path"
+    return 0
+}
+
+# Extract fallback chain from agent YAML frontmatter.
+# Returns JSON array of model specs, or empty if not defined.
+get_agent_chain() {
+    local agent_file="$1"
+    local tier="$2"
+
+    if [[ ! -f "$agent_file" ]]; then
+        return 1
+    fi
+
+    # Parse YAML frontmatter for fallback-chain field
+    local in_frontmatter=false
+    local in_chain=false
+    local chain_json="["
+    local first=true
+    local line_num=0
+
+    while IFS= read -r line; do
+        line_num=$((line_num + 1))
+        if [[ $line_num -eq 1 && "$line" == "---" ]]; then
+            in_frontmatter=true
+            continue
+        fi
+        if [[ "$in_frontmatter" == "true" && "$line" == "---" ]]; then
+            break
+        fi
+        if [[ "$in_frontmatter" == "true" ]]; then
+            # Check for fallback-chain: start
+            if [[ "$line" =~ ^fallback-chain: ]]; then
+                in_chain=true
+                continue
+            fi
+            # Collect chain entries (YAML list items)
+            if [[ "$in_chain" == "true" ]]; then
+                if [[ "$line" =~ ^[[:space:]]+-[[:space:]]+(.*) ]]; then
+                    local entry="${BASH_REMATCH[1]}"
+                    entry="${entry#"${entry%%[![:space:]]*}"}"
+                    entry="${entry%"${entry##*[![:space:]]}"}"
+                    if [[ "$first" == "true" ]]; then
+                        first=false
+                    else
+                        chain_json="${chain_json},"
+                    fi
+                    chain_json="${chain_json}\"${entry}\""
+                elif [[ ! "$line" =~ ^[[:space:]] ]]; then
+                    # End of chain list (non-indented line)
+                    in_chain=false
+                fi
+            fi
+        fi
+    done < "$agent_file"
+
+    chain_json="${chain_json}]"
+
+    # Return empty if no chain found
+    if [[ "$chain_json" == "[]" ]]; then
+        return 1
+    fi
+
+    echo "$chain_json"
+    return 0
+}
+
+# Get the fallback chain for a tier from config.
+# Priority: per-agent frontmatter > config tier-specific > config global default
+get_chain_for_tier() {
+    local tier="$1"
+    local config_path="$2"
+    local agent_file="${3:-}"
+
+    # Priority 1: Per-agent frontmatter
+    if [[ -n "$agent_file" ]]; then
+        local agent_chain
+        agent_chain=$(get_agent_chain "$agent_file" "$tier" 2>/dev/null) || true
+        if [[ -n "$agent_chain" && "$agent_chain" != "[]" ]]; then
+            echo "$agent_chain"
+            return 0
+        fi
+    fi
+
+    # Priority 2: Tier-specific chain from config
+    local tier_chain
+    tier_chain=$(jq -r --arg tier "$tier" '.chains[$tier] // empty' "$config_path" 2>/dev/null) || true
+    if [[ -n "$tier_chain" && "$tier_chain" != "null" ]]; then
+        echo "$tier_chain"
+        return 0
+    fi
+
+    # Priority 3: Global default chain from config
+    local default_chain
+    default_chain=$(jq -r '.chains.default // empty' "$config_path" 2>/dev/null) || true
+    if [[ -n "$default_chain" && "$default_chain" != "null" ]]; then
+        echo "$default_chain"
+        return 0
+    fi
+
+    # Priority 4: Hardcoded minimal fallback
+    # Use the existing model-availability-helper.sh tier mapping
+    local tier_spec=""
+    case "$tier" in
+        haiku)  tier_spec='["anthropic/claude-3-5-haiku-20241022","google/gemini-2.5-flash","openrouter/anthropic/claude-3-5-haiku-20241022"]' ;;
+        flash)  tier_spec='["google/gemini-2.5-flash","openai/gpt-4.1-mini","openrouter/google/gemini-2.5-flash"]' ;;
+        sonnet) tier_spec='["anthropic/claude-sonnet-4-20250514","openai/gpt-4.1","openrouter/anthropic/claude-sonnet-4-20250514"]' ;;
+        pro)    tier_spec='["google/gemini-2.5-pro","anthropic/claude-sonnet-4-20250514","openrouter/google/gemini-2.5-pro"]' ;;
+        opus)   tier_spec='["anthropic/claude-opus-4-6","openai/o3","openrouter/anthropic/claude-opus-4-6"]' ;;
+        coding) tier_spec='["anthropic/claude-opus-4-6","openai/o3","openrouter/anthropic/claude-opus-4-6"]' ;;
+        eval)   tier_spec='["anthropic/claude-sonnet-4-5","google/gemini-2.5-flash","openrouter/anthropic/claude-sonnet-4-5"]' ;;
+        health) tier_spec='["anthropic/claude-sonnet-4-5","google/gemini-2.5-flash"]' ;;
+        *)
+            print_error "Unknown tier: $tier"
+            return 1
+            ;;
+    esac
+    echo "$tier_spec"
+    return 0
+}
+
+# =============================================================================
+# Provider Cooldown Management
+# =============================================================================
+
+# Check if a provider is in cooldown (recently failed).
+is_provider_cooled_down() {
+    local provider="$1"
+
+    local cooldown_until
+    cooldown_until=$(db_query "
+        SELECT cooldown_until FROM provider_cooldown
+        WHERE provider = '$(sql_escape "$provider")';
+    ")
+
+    if [[ -z "$cooldown_until" ]]; then
+        return 1  # Not in cooldown
+    fi
+
+    local cooldown_epoch now_epoch
+    if [[ "$(uname)" == "Darwin" ]]; then
+        cooldown_epoch=$(date -j -f "%Y-%m-%dT%H:%M:%SZ" "$cooldown_until" "+%s" 2>/dev/null || echo "0")
+    else
+        cooldown_epoch=$(date -d "$cooldown_until" "+%s" 2>/dev/null || echo "0")
+    fi
+    now_epoch=$(date "+%s")
+
+    if [[ "$now_epoch" -lt "$cooldown_epoch" ]]; then
+        return 0  # Still in cooldown
+    fi
+
+    # Cooldown expired, remove it
+    db_query "DELETE FROM provider_cooldown WHERE provider = '$(sql_escape "$provider")';" || true
+    return 1  # No longer in cooldown
+}
+
+# Put a provider into cooldown after a failure.
+set_provider_cooldown() {
+    local provider="$1"
+    local reason="$2"
+    local duration="${3:-$COOLDOWN_SECONDS}"
+
+    local cooldown_until
+    if [[ "$(uname)" == "Darwin" ]]; then
+        cooldown_until=$(date -u -v+"${duration}S" +%Y-%m-%dT%H:%M:%SZ 2>/dev/null)
+    else
+        cooldown_until=$(date -u -d "+${duration} seconds" +%Y-%m-%dT%H:%M:%SZ 2>/dev/null)
+    fi
+
+    db_query "
+        INSERT INTO provider_cooldown (provider, reason, cooldown_until)
+        VALUES (
+            '$(sql_escape "$provider")',
+            '$(sql_escape "$reason")',
+            '$(sql_escape "$cooldown_until")'
+        )
+        ON CONFLICT(provider) DO UPDATE SET
+            reason = excluded.reason,
+            cooldown_until = excluded.cooldown_until,
+            created_at = strftime('%Y-%m-%dT%H:%M:%SZ', 'now');
+    " || true
+    return 0
+}
+
+# =============================================================================
+# Trigger Detection
+# =============================================================================
+
+# Classify an error into a trigger type based on HTTP status code or error message.
+classify_trigger() {
+    local error_input="$1"
+
+    # HTTP status code patterns
+    case "$error_input" in
+        429|*"rate limit"*|*"Rate limit"*|*"rate_limit"*|*"too many requests"*|*"Too Many Requests"*)
+            echo "rate_limit"
+            return 0
+            ;;
+        401|403|*"auth"*|*"forbidden"*|*"Forbidden"*|*"invalid"*"key"*|*"Invalid"*"key"*)
+            echo "auth_error"
+            return 0
+            ;;
+        500|502|503|504|*"internal server"*|*"Internal Server"*|*"bad gateway"*|*"Bad Gateway"*|*"service unavailable"*|*"Service Unavailable"*|*"gateway timeout"*|*"Gateway Timeout"*)
+            echo "api_error"
+            return 0
+            ;;
+        529|*"overloaded"*|*"Overloaded"*|*"capacity"*)
+            echo "overloaded"
+            return 0
+            ;;
+        *"timeout"*|*"Timeout"*|*"ETIMEDOUT"*|*"ECONNRESET"*|*"timed out"*)
+            echo "timeout"
+            return 0
+            ;;
+        *"connection refused"*|*"Connection refused"*|*"ECONNREFUSED"*|*"network"*|*"Network"*)
+            echo "api_error"
+            return 0
+            ;;
+        *)
+            echo "unknown"
+            return 0
+            ;;
+    esac
+}
+
+# Determine cooldown duration based on trigger type.
+get_cooldown_for_trigger() {
+    local trigger_type="$1"
+    local config_path="$2"
+
+    # Try config first
+    local configured_cooldown
+    configured_cooldown=$(jq -r --arg trigger "$trigger_type" \
+        '.triggers[$trigger].cooldown_seconds // empty' "$config_path" 2>/dev/null) || true
+
+    if [[ -n "$configured_cooldown" && "$configured_cooldown" != "null" ]]; then
+        echo "$configured_cooldown"
+        return 0
+    fi
+
+    # Default cooldowns by trigger type
+    case "$trigger_type" in
+        rate_limit)  echo "60" ;;    # 1 minute
+        auth_error)  echo "3600" ;;  # 1 hour (key won't fix itself)
+        api_error)   echo "300" ;;   # 5 minutes
+        overloaded)  echo "120" ;;   # 2 minutes
+        timeout)     echo "180" ;;   # 3 minutes
+        *)           echo "300" ;;   # 5 minutes default
+    esac
+    return 0
+}
+
+# Check if a trigger type should activate fallback.
+should_trigger_fallback() {
+    local trigger_type="$1"
+    local config_path="$2"
+
+    # Check config for trigger enablement
+    local enabled
+    enabled=$(jq -r --arg trigger "$trigger_type" \
+        '.triggers[$trigger].enabled // true' "$config_path" 2>/dev/null) || true
+
+    if [[ "$enabled" == "false" ]]; then
+        return 1
+    fi
+
+    return 0
+}
+
+# =============================================================================
+# Gateway Provider Support
+# =============================================================================
+
+# Extract provider name from a model spec.
+# Handles both direct (anthropic/claude-sonnet-4) and gateway
+# (openrouter/anthropic/claude-sonnet-4, gateway/cf/anthropic/claude-sonnet-4) formats.
+parse_model_spec() {
+    local model_spec="$1"
+    local field="$2"  # provider, gateway, model, or full
+
+    case "$model_spec" in
+        gateway/cf/*)
+            # Cloudflare AI Gateway: gateway/cf/provider/model
+            case "$field" in
+                gateway)  echo "cloudflare" ;;
+                provider) echo "$model_spec" | cut -d'/' -f3 ;;
+                model)    echo "$model_spec" | cut -d'/' -f4- ;;
+                full)     echo "$model_spec" ;;
+            esac
+            ;;
+        openrouter/*)
+            # OpenRouter gateway: openrouter/provider/model
+            case "$field" in
+                gateway)  echo "openrouter" ;;
+                provider) echo "$model_spec" | cut -d'/' -f2 ;;
+                model)    echo "$model_spec" | cut -d'/' -f3- ;;
+                full)     echo "$model_spec" ;;
+            esac
+            ;;
+        */*)
+            # Direct provider: provider/model
+            case "$field" in
+                gateway)  echo "direct" ;;
+                provider) echo "${model_spec%%/*}" ;;
+                model)    echo "${model_spec#*/}" ;;
+                full)     echo "$model_spec" ;;
+            esac
+            ;;
+        *)
+            # Bare model name
+            case "$field" in
+                gateway)  echo "direct" ;;
+                provider) echo "unknown" ;;
+                model)    echo "$model_spec" ;;
+                full)     echo "$model_spec" ;;
+            esac
+            ;;
+    esac
+    return 0
+}
+
+# Check if a gateway provider is available.
+check_gateway() {
+    local gateway_type="$1"
+    local config_path="$2"
+    local quiet="${3:-false}"
+
+    case "$gateway_type" in
+        openrouter)
+            _check_openrouter_gateway "$config_path" "$quiet"
+            return $?
+            ;;
+        cloudflare)
+            _check_cloudflare_gateway "$config_path" "$quiet"
+            return $?
+            ;;
+        direct)
+            return 0  # Direct providers checked by model-availability-helper
+            ;;
+        *)
+            [[ "$quiet" != "true" ]] && print_warning "Unknown gateway type: $gateway_type"
+            return 1
+            ;;
+    esac
+}
+
+_check_openrouter_gateway() {
+    local config_path="$1"
+    local quiet="$2"
+
+    # Check for OpenRouter API key
+    local key_var="OPENROUTER_API_KEY"
+    if [[ -z "${!key_var:-}" ]]; then
+        # Try credentials.sh
+        local creds_file="${HOME}/.config/aidevops/credentials.sh"
+        if [[ -f "$creds_file" ]]; then
+            # shellcheck disable=SC1090
+            source "$creds_file"
+        fi
+    fi
+
+    if [[ -z "${OPENROUTER_API_KEY:-}" ]]; then
+        [[ "$quiet" != "true" ]] && print_warning "OpenRouter: no API key configured"
+        _record_gateway_health "openrouter" "openrouter" "no_key" "" 0 "No OPENROUTER_API_KEY"
+        return 1
+    fi
+
+    # Lightweight probe
+    local start_ms
+    start_ms=$(date +%s%N 2>/dev/null || echo "0")
+
+    local http_code
+    http_code=$(curl -s -o /dev/null -w '%{http_code}' --max-time "$GATEWAY_PROBE_TIMEOUT" \
+        -H "Authorization: Bearer ${OPENROUTER_API_KEY}" \
+        "https://openrouter.ai/api/v1/models" 2>/dev/null) || http_code="000"
+
+    local end_ms
+    end_ms=$(date +%s%N 2>/dev/null || echo "0")
+    local duration_ms=0
+    if [[ "$start_ms" != "0" && "$end_ms" != "0" ]]; then
+        duration_ms=$(( (end_ms - start_ms) / 1000000 ))
+    fi
+
+    if [[ "$http_code" == "200" ]]; then
+        [[ "$quiet" != "true" ]] && print_success "OpenRouter: healthy (${duration_ms}ms)"
+        _record_gateway_health "openrouter" "openrouter" "healthy" "https://openrouter.ai/api/v1" "$duration_ms" ""
+        return 0
+    fi
+
+    [[ "$quiet" != "true" ]] && print_warning "OpenRouter: unhealthy (HTTP $http_code)"
+    _record_gateway_health "openrouter" "openrouter" "unhealthy" "https://openrouter.ai/api/v1" "$duration_ms" "HTTP $http_code"
+    return 1
+}
+
+_check_cloudflare_gateway() {
+    local config_path="$1"
+    local quiet="$2"
+
+    # Get Cloudflare AI Gateway config
+    local account_id gateway_id cf_token
+    account_id=$(jq -r '.gateways.cloudflare.account_id // empty' "$config_path" 2>/dev/null) || true
+    gateway_id=$(jq -r '.gateways.cloudflare.gateway_id // empty' "$config_path" 2>/dev/null) || true
+
+    if [[ -z "$account_id" || -z "$gateway_id" ]]; then
+        [[ "$quiet" != "true" ]] && print_warning "Cloudflare AI Gateway: not configured (missing account_id/gateway_id)"
+        _record_gateway_health "cloudflare" "cloudflare" "not_configured" "" 0 "Missing account_id or gateway_id"
+        return 1
+    fi
+
+    # Check for CF token
+    cf_token="${CF_AIG_TOKEN:-${CLOUDFLARE_API_TOKEN:-}}"
+    if [[ -z "$cf_token" ]]; then
+        local creds_file="${HOME}/.config/aidevops/credentials.sh"
+        if [[ -f "$creds_file" ]]; then
+            # shellcheck disable=SC1090
+            source "$creds_file"
+            cf_token="${CF_AIG_TOKEN:-${CLOUDFLARE_API_TOKEN:-}}"
+        fi
+    fi
+
+    local endpoint="https://gateway.ai.cloudflare.com/v1/${account_id}/${gateway_id}"
+
+    # Lightweight probe (just check if the gateway endpoint responds)
+    local start_ms
+    start_ms=$(date +%s%N 2>/dev/null || echo "0")
+
+    local -a curl_args=(-s -o /dev/null -w '%{http_code}' --max-time "$GATEWAY_PROBE_TIMEOUT")
+    if [[ -n "$cf_token" ]]; then
+        curl_args+=(-H "cf-aig-authorization: Bearer ${cf_token}")
+    fi
+
+    local http_code
+    http_code=$(curl "${curl_args[@]}" "${endpoint}/openai/models" 2>/dev/null) || http_code="000"
+
+    local end_ms
+    end_ms=$(date +%s%N 2>/dev/null || echo "0")
+    local duration_ms=0
+    if [[ "$start_ms" != "0" && "$end_ms" != "0" ]]; then
+        duration_ms=$(( (end_ms - start_ms) / 1000000 ))
+    fi
+
+    # CF AI Gateway returns various codes; 200 or 401 (needs auth) both mean it's reachable
+    if [[ "$http_code" == "200" || "$http_code" == "401" ]]; then
+        [[ "$quiet" != "true" ]] && print_success "Cloudflare AI Gateway: reachable (${duration_ms}ms)"
+        _record_gateway_health "cloudflare" "cloudflare" "healthy" "$endpoint" "$duration_ms" ""
+        return 0
+    fi
+
+    [[ "$quiet" != "true" ]] && print_warning "Cloudflare AI Gateway: unreachable (HTTP $http_code)"
+    _record_gateway_health "cloudflare" "cloudflare" "unhealthy" "$endpoint" "$duration_ms" "HTTP $http_code"
+    return 1
+}
+
+_record_gateway_health() {
+    local gateway_id="$1"
+    local gateway_type="$2"
+    local status="$3"
+    local endpoint="$4"
+    local response_ms="$5"
+    local error_msg="$6"
+
+    db_query "
+        INSERT INTO gateway_health (gateway_id, gateway_type, status, endpoint, last_checked, response_ms, error_message)
+        VALUES (
+            '$(sql_escape "$gateway_id")',
+            '$(sql_escape "$gateway_type")',
+            '$(sql_escape "$status")',
+            '$(sql_escape "$endpoint")',
+            strftime('%Y-%m-%dT%H:%M:%SZ', 'now'),
+            $response_ms,
+            '$(sql_escape "$error_msg")'
+        )
+        ON CONFLICT(gateway_id) DO UPDATE SET
+            gateway_type = excluded.gateway_type,
+            status = excluded.status,
+            endpoint = excluded.endpoint,
+            last_checked = excluded.last_checked,
+            response_ms = excluded.response_ms,
+            error_message = excluded.error_message;
+    " || true
+    return 0
+}
+
+# =============================================================================
+# Chain Resolution
+# =============================================================================
+
+# Resolve the best available model by walking the fallback chain.
+# Skips providers in cooldown, checks availability, and logs the resolution.
+resolve_chain() {
+    local tier="$1"
+    local config_path="$2"
+    local agent_file="${3:-}"
+    local max_depth="${4:-$DEFAULT_MAX_DEPTH}"
+    local force="${5:-false}"
+    local quiet="${6:-false}"
+
+    # Get the chain for this tier
+    local chain_json
+    chain_json=$(get_chain_for_tier "$tier" "$config_path" "$agent_file") || {
+        print_error "Could not determine fallback chain for tier: $tier" >&2
+        return 1
+    }
+
+    local chain_length
+    chain_length=$(echo "$chain_json" | jq 'length' 2>/dev/null) || chain_length=0
+
+    if [[ "$chain_length" -eq 0 ]]; then
+        print_error "Empty fallback chain for tier: $tier" >&2
+        return 1
+    fi
+
+    # Cap at max depth
+    if [[ "$chain_length" -gt "$max_depth" ]]; then
+        chain_length="$max_depth"
+    fi
+
+    # Walk the chain
+    local depth=0
+    while [[ "$depth" -lt "$chain_length" ]]; do
+        local model_spec
+        model_spec=$(echo "$chain_json" | jq -r ".[$depth]" 2>/dev/null) || true
+
+        if [[ -z "$model_spec" || "$model_spec" == "null" ]]; then
+            depth=$((depth + 1))
+            continue
+        fi
+
+        local provider gateway
+        provider=$(parse_model_spec "$model_spec" "provider")
+        gateway=$(parse_model_spec "$model_spec" "gateway")
+
+        # Check provider cooldown
+        if is_provider_cooled_down "$provider"; then
+            [[ "$quiet" != "true" ]] && print_warning "  [$depth] $model_spec: provider $provider in cooldown, skipping" >&2
+            depth=$((depth + 1))
+            continue
+        fi
+
+        # Check gateway availability (for gateway-routed models)
+        if [[ "$gateway" != "direct" ]]; then
+            if ! check_gateway "$gateway" "$config_path" "true"; then
+                [[ "$quiet" != "true" ]] && print_warning "  [$depth] $model_spec: gateway $gateway unavailable, skipping" >&2
+                depth=$((depth + 1))
+                continue
+            fi
+        fi
+
+        # Check model availability via model-availability-helper.sh
+        if [[ -x "$AVAILABILITY_HELPER" && "$gateway" == "direct" ]]; then
+            local avail_exit=0
+            "$AVAILABILITY_HELPER" check "$provider" --quiet 2>/dev/null || avail_exit=$?
+
+            if [[ "$avail_exit" -ne 0 ]]; then
+                [[ "$quiet" != "true" ]] && print_warning "  [$depth] $model_spec: provider $provider unavailable (exit $avail_exit), skipping" >&2
+                depth=$((depth + 1))
+                continue
+            fi
+        fi
+
+        # Model is available
+        [[ "$quiet" != "true" ]] && print_success "  [$depth] $model_spec: available" >&2
+
+        # Log the resolution
+        db_query "
+            INSERT INTO trigger_log (tier, trigger_type, failed_model, resolved_model, chain_depth, details)
+            VALUES (
+                '$(sql_escape "$tier")',
+                'resolve',
+                '',
+                '$(sql_escape "$model_spec")',
+                $depth,
+                'Chain resolution'
+            );
+        " || true
+
+        echo "$model_spec"
+        return 0
+    done
+
+    [[ "$quiet" != "true" ]] && print_error "All models exhausted in fallback chain for tier: $tier" >&2
+    return 3
+}
+
+# =============================================================================
+# Commands
+# =============================================================================
+
+cmd_resolve() {
+    local tier="${1:-}"
+    shift || true
+
+    local config_override="" agent_file="" json_flag=false quiet=false force=false max_depth="$DEFAULT_MAX_DEPTH"
+
+    while [[ $# -gt 0 ]]; do
+        case "$1" in
+            --config) config_override="${2:-}"; shift 2 ;;
+            --agent) agent_file="${2:-}"; shift 2 ;;
+            --json) json_flag=true; shift ;;
+            --quiet) quiet=true; shift ;;
+            --force) force=true; shift ;;
+            --max-depth) max_depth="${2:-$DEFAULT_MAX_DEPTH}"; shift 2 ;;
+            *) shift ;;
+        esac
+    done
+
+    if [[ -z "$tier" ]]; then
+        print_error "Usage: fallback-chain-helper.sh resolve <tier>"
+        return 1
+    fi
+
+    local config_path
+    config_path=$(load_config "${config_override:-$DEFAULT_CONFIG}") || return $?
+
+    [[ "$quiet" != "true" ]] && print_info "Resolving fallback chain for tier: $tier" >&2
+
+    local resolved
+    resolved=$(resolve_chain "$tier" "$config_path" "$agent_file" "$max_depth" "$force" "$quiet") || {
+        local exit_code=$?
+        if [[ "$json_flag" == "true" ]]; then
+            echo "{\"tier\":\"$tier\",\"status\":\"exhausted\",\"model\":null}"
+        fi
+        return "$exit_code"
+    }
+
+    if [[ "$json_flag" == "true" ]]; then
+        local provider gateway model_id
+        provider=$(parse_model_spec "$resolved" "provider")
+        gateway=$(parse_model_spec "$resolved" "gateway")
+        model_id=$(parse_model_spec "$resolved" "model")
+        echo "{\"tier\":\"$tier\",\"status\":\"resolved\",\"model\":\"$resolved\",\"provider\":\"$provider\",\"gateway\":\"$gateway\",\"model_id\":\"$model_id\"}"
+    else
+        echo "$resolved"
+    fi
+
+    return 0
+}
+
+cmd_trigger() {
+    local tier="${1:-}"
+    local error_input="${2:-}"
+    shift 2 || true
+
+    local config_override="" agent_file="" json_flag=false quiet=false max_depth="$DEFAULT_MAX_DEPTH"
+    local failed_model=""
+
+    while [[ $# -gt 0 ]]; do
+        case "$1" in
+            --config) config_override="${2:-}"; shift 2 ;;
+            --agent) agent_file="${2:-}"; shift 2 ;;
+            --json) json_flag=true; shift ;;
+            --quiet) quiet=true; shift ;;
+            --failed-model) failed_model="${2:-}"; shift 2 ;;
+            --max-depth) max_depth="${2:-$DEFAULT_MAX_DEPTH}"; shift 2 ;;
+            *) shift ;;
+        esac
+    done
+
+    if [[ -z "$tier" || -z "$error_input" ]]; then
+        print_error "Usage: fallback-chain-helper.sh trigger <tier> <error> [--failed-model model]"
+        return 1
+    fi
+
+    local config_path
+    config_path=$(load_config "${config_override:-$DEFAULT_CONFIG}") || return $?
+
+    # Classify the trigger
+    local trigger_type
+    trigger_type=$(classify_trigger "$error_input")
+
+    [[ "$quiet" != "true" ]] && print_info "Trigger: $trigger_type (from: $error_input)" >&2
+
+    # Check if this trigger type should activate fallback
+    if ! should_trigger_fallback "$trigger_type" "$config_path"; then
+        [[ "$quiet" != "true" ]] && print_info "Trigger type '$trigger_type' is disabled in config" >&2
+        return 1
+    fi
+
+    # Put the failed provider into cooldown
+    if [[ -n "$failed_model" ]]; then
+        local failed_provider
+        failed_provider=$(parse_model_spec "$failed_model" "provider")
+        local cooldown_duration
+        cooldown_duration=$(get_cooldown_for_trigger "$trigger_type" "$config_path")
+        set_provider_cooldown "$failed_provider" "$trigger_type" "$cooldown_duration"
+        [[ "$quiet" != "true" ]] && print_info "Provider $failed_provider in cooldown for ${cooldown_duration}s ($trigger_type)" >&2
+    fi
+
+    # Resolve next available model from chain
+    local resolved
+    resolved=$(resolve_chain "$tier" "$config_path" "$agent_file" "$max_depth" "false" "$quiet") || {
+        local exit_code=$?
+        # Log the exhaustion
+        db_query "
+            INSERT INTO trigger_log (tier, trigger_type, failed_model, resolved_model, chain_depth, details)
+            VALUES (
+                '$(sql_escape "$tier")',
+                '$(sql_escape "$trigger_type")',
+                '$(sql_escape "${failed_model:-unknown}")',
+                '',
+                $max_depth,
+                '$(sql_escape "Chain exhausted after trigger: $error_input")'
+            );
+        " || true
+        if [[ "$json_flag" == "true" ]]; then
+            echo "{\"tier\":\"$tier\",\"trigger\":\"$trigger_type\",\"status\":\"exhausted\",\"model\":null,\"failed_model\":\"${failed_model:-}\"}"
+        fi
+        return "$exit_code"
+    }
+
+    # Log the trigger resolution
+    db_query "
+        INSERT INTO trigger_log (tier, trigger_type, failed_model, resolved_model, chain_depth, details)
+        VALUES (
+            '$(sql_escape "$tier")',
+            '$(sql_escape "$trigger_type")',
+            '$(sql_escape "${failed_model:-unknown}")',
+            '$(sql_escape "$resolved")',
+            0,
+            '$(sql_escape "Triggered by: $error_input")'
+        );
+    " || true
+
+    if [[ "$json_flag" == "true" ]]; then
+        local provider gateway model_id
+        provider=$(parse_model_spec "$resolved" "provider")
+        gateway=$(parse_model_spec "$resolved" "gateway")
+        model_id=$(parse_model_spec "$resolved" "model")
+        echo "{\"tier\":\"$tier\",\"trigger\":\"$trigger_type\",\"status\":\"resolved\",\"model\":\"$resolved\",\"provider\":\"$provider\",\"gateway\":\"$gateway\",\"model_id\":\"$model_id\",\"failed_model\":\"${failed_model:-}\"}"
+    else
+        echo "$resolved"
+    fi
+
+    return 0
+}
+
+cmd_chain() {
+    local tier="${1:-}"
+    shift || true
+
+    local config_override="" agent_file="" json_flag=false
+
+    while [[ $# -gt 0 ]]; do
+        case "$1" in
+            --config) config_override="${2:-}"; shift 2 ;;
+            --agent) agent_file="${2:-}"; shift 2 ;;
+            --json) json_flag=true; shift ;;
+            *) shift ;;
+        esac
+    done
+
+    if [[ -z "$tier" ]]; then
+        print_error "Usage: fallback-chain-helper.sh chain <tier>"
+        return 1
+    fi
+
+    local config_path
+    config_path=$(load_config "${config_override:-$DEFAULT_CONFIG}") || return $?
+
+    local chain_json
+    chain_json=$(get_chain_for_tier "$tier" "$config_path" "$agent_file") || {
+        print_error "Could not determine chain for tier: $tier"
+        return 1
+    }
+
+    if [[ "$json_flag" == "true" ]]; then
+        echo "{\"tier\":\"$tier\",\"chain\":$chain_json}"
+        return 0
+    fi
+
+    echo ""
+    echo "Fallback Chain: $tier"
+    echo "===================="
+    echo ""
+
+    local chain_length idx
+    chain_length=$(echo "$chain_json" | jq 'length' 2>/dev/null) || chain_length=0
+    idx=0
+
+    while [[ "$idx" -lt "$chain_length" ]]; do
+        local model_spec provider gateway model_id
+        model_spec=$(echo "$chain_json" | jq -r ".[$idx]" 2>/dev/null) || true
+        provider=$(parse_model_spec "$model_spec" "provider")
+        gateway=$(parse_model_spec "$model_spec" "gateway")
+        model_id=$(parse_model_spec "$model_spec" "model")
+
+        local cooldown_status=""
+        if is_provider_cooled_down "$provider"; then
+            cooldown_status=" [COOLDOWN]"
+        fi
+
+        local gateway_label=""
+        if [[ "$gateway" != "direct" ]]; then
+            gateway_label=" via $gateway"
+        fi
+
+        printf "  %d. %s (%s%s)%s\n" "$((idx + 1))" "$model_spec" "$provider" "$gateway_label" "$cooldown_status"
+        idx=$((idx + 1))
+    done
+
+    echo ""
+    return 0
+}
+
+cmd_status() {
+    local json_flag=false config_override=""
+
+    while [[ $# -gt 0 ]]; do
+        case "$1" in
+            --json) json_flag=true; shift ;;
+            --config) config_override="${2:-}"; shift 2 ;;
+            *) shift ;;
+        esac
+    done
+
+    local config_path
+    config_path=$(load_config "${config_override:-$DEFAULT_CONFIG}") || return $?
+
+    if [[ "$json_flag" == "true" ]]; then
+        local cooldowns triggers gateways
+        cooldowns=$(db_query_json "SELECT provider, reason, cooldown_until FROM provider_cooldown ORDER BY provider;" 2>/dev/null || echo "[]")
+        triggers=$(db_query_json "SELECT tier, trigger_type, failed_model, resolved_model, chain_depth, timestamp FROM trigger_log ORDER BY id DESC LIMIT 20;" 2>/dev/null || echo "[]")
+        gateways=$(db_query_json "SELECT gateway_id, gateway_type, status, endpoint, last_checked, response_ms FROM gateway_health ORDER BY gateway_id;" 2>/dev/null || echo "[]")
+        echo "{\"cooldowns\":$cooldowns,\"recent_triggers\":$triggers,\"gateways\":$gateways}"
+        return 0
+    fi
+
+    echo ""
+    echo "Fallback Chain Status"
+    echo "====================="
+    echo ""
+
+    # Show chains for all tiers
+    echo "Tier Chains:"
+    echo ""
+    local tiers="haiku flash sonnet pro opus coding eval health"
+    for tier in $tiers; do
+        local chain_json
+        chain_json=$(get_chain_for_tier "$tier" "$config_path" "" 2>/dev/null) || chain_json="[]"
+        local chain_length
+        chain_length=$(echo "$chain_json" | jq 'length' 2>/dev/null || echo "0")
+        local first_model last_model
+        first_model=$(echo "$chain_json" | jq -r '.[0] // "none"' 2>/dev/null)
+        last_model=$(echo "$chain_json" | jq -r '.[-1] // "none"' 2>/dev/null)
+        printf "  %-8s %s -> ... -> %s (%d models)\n" "$tier" "$first_model" "$last_model" "$chain_length"
+    done
+
+    # Show active cooldowns
+    echo ""
+    echo "Active Cooldowns:"
+    echo ""
+    local cooldown_count
+    cooldown_count=$(db_query "SELECT COUNT(*) FROM provider_cooldown;" 2>/dev/null || echo "0")
+    if [[ "$cooldown_count" -eq 0 ]]; then
+        echo "  (none)"
+    else
+        db_query "SELECT provider, reason, cooldown_until FROM provider_cooldown ORDER BY provider;" | \
+        while IFS='|' read -r prov reason until; do
+            printf "  %-12s %-15s until %s\n" "$prov" "$reason" "$until"
+        done
+    fi
+
+    # Show gateway health
+    echo ""
+    echo "Gateway Health:"
+    echo ""
+    local gw_count
+    gw_count=$(db_query "SELECT COUNT(*) FROM gateway_health;" 2>/dev/null || echo "0")
+    if [[ "$gw_count" -eq 0 ]]; then
+        echo "  (no gateways probed yet)"
+    else
+        printf "  %-12s %-12s %-12s %-8s %s\n" "Gateway" "Type" "Status" "Time" "Endpoint"
+        printf "  %-12s %-12s %-12s %-8s %s\n" "-------" "----" "------" "----" "--------"
+        db_query "SELECT gateway_id, gateway_type, status, response_ms, endpoint FROM gateway_health ORDER BY gateway_id;" | \
+        while IFS='|' read -r gid gtype gstatus gms gendpoint; do
+            printf "  %-12s %-12s %-12s %-8s %s\n" "$gid" "$gtype" "$gstatus" "${gms}ms" "$gendpoint"
+        done
+    fi
+
+    # Show recent triggers
+    echo ""
+    echo "Recent Triggers (last 10):"
+    echo ""
+    local trigger_count
+    trigger_count=$(db_query "SELECT COUNT(*) FROM trigger_log;" 2>/dev/null || echo "0")
+    if [[ "$trigger_count" -eq 0 ]]; then
+        echo "  (no triggers recorded)"
+    else
+        db_query "
+            SELECT timestamp, tier, trigger_type, failed_model, resolved_model, chain_depth
+            FROM trigger_log ORDER BY id DESC LIMIT 10;
+        " | while IFS='|' read -r ts tier ttype failed resolved depth; do
+            printf "  %s  %-8s %-12s %s -> %s (depth %s)\n" \
+                "$ts" "$tier" "$ttype" "${failed:-n/a}" "${resolved:-EXHAUSTED}" "$depth"
+        done
+    fi
+
+    echo ""
+    return 0
+}
+
+cmd_validate() {
+    local config_override=""
+
+    while [[ $# -gt 0 ]]; do
+        case "$1" in
+            --config) config_override="${2:-}"; shift 2 ;;
+            *) shift ;;
+        esac
+    done
+
+    local config_path
+    config_path=$(load_config "${config_override:-$DEFAULT_CONFIG}") || return $?
+
+    echo ""
+    echo "Fallback Chain Validation"
+    echo "========================="
+    echo ""
+
+    local issues=0
+
+    # Check JSON structure
+    if ! jq empty "$config_path" 2>/dev/null; then
+        print_error "Invalid JSON: $config_path"
+        return 2
+    fi
+    print_success "JSON syntax: valid"
+
+    # Check required top-level keys
+    local has_chains has_triggers has_gateways
+    has_chains=$(jq 'has("chains")' "$config_path" 2>/dev/null)
+    has_triggers=$(jq 'has("triggers")' "$config_path" 2>/dev/null)
+    has_gateways=$(jq 'has("gateways")' "$config_path" 2>/dev/null)
+
+    if [[ "$has_chains" != "true" ]]; then
+        print_warning "Missing 'chains' key (will use hardcoded defaults)"
+        issues=$((issues + 1))
+    else
+        print_success "chains: present"
+    fi
+
+    if [[ "$has_triggers" != "true" ]]; then
+        print_warning "Missing 'triggers' key (will use default trigger settings)"
+        issues=$((issues + 1))
+    else
+        print_success "triggers: present"
+    fi
+
+    if [[ "$has_gateways" != "true" ]]; then
+        print_info "No 'gateways' key (gateway fallback disabled)"
+    else
+        print_success "gateways: present"
+    fi
+
+    # Validate each chain has at least 2 entries
+    echo ""
+    echo "Chain Validation:"
+    local tiers
+    tiers=$(jq -r '.chains | keys[]' "$config_path" 2>/dev/null) || tiers=""
+    for tier in $tiers; do
+        local chain_length
+        chain_length=$(jq -r --arg t "$tier" '.chains[$t] | length' "$config_path" 2>/dev/null) || chain_length=0
+        if [[ "$chain_length" -lt 2 ]]; then
+            print_warning "  $tier: only $chain_length model(s) (recommend >= 2 for fallback)"
+            issues=$((issues + 1))
+        else
+            print_success "  $tier: $chain_length models"
+        fi
+    done
+
+    # Validate trigger types
+    echo ""
+    echo "Trigger Validation:"
+    local trigger_types="api_error timeout rate_limit auth_error overloaded"
+    for tt in $trigger_types; do
+        local enabled
+        enabled=$(jq -r --arg t "$tt" '.triggers[$t].enabled // "not configured"' "$config_path" 2>/dev/null)
+        if [[ "$enabled" == "not configured" ]]; then
+            print_info "  $tt: not configured (defaults to enabled)"
+        elif [[ "$enabled" == "true" ]]; then
+            print_success "  $tt: enabled"
+        else
+            print_info "  $tt: disabled"
+        fi
+    done
+
+    echo ""
+    if [[ "$issues" -gt 0 ]]; then
+        print_warning "$issues issue(s) found (non-critical, defaults will be used)"
+    else
+        print_success "Configuration is valid"
+    fi
+    echo ""
+    return 0
+}
+
+cmd_gateway() {
+    local gateway="${1:-}"
+    shift || true
+
+    local config_override="" quiet=false json_flag=false
+
+    while [[ $# -gt 0 ]]; do
+        case "$1" in
+            --config) config_override="${2:-}"; shift 2 ;;
+            --quiet) quiet=true; shift ;;
+            --json) json_flag=true; shift ;;
+            *) shift ;;
+        esac
+    done
+
+    if [[ -z "$gateway" ]]; then
+        print_error "Usage: fallback-chain-helper.sh gateway <openrouter|cloudflare>"
+        return 1
+    fi
+
+    local config_path
+    config_path=$(load_config "${config_override:-$DEFAULT_CONFIG}") || return $?
+
+    check_gateway "$gateway" "$config_path" "$quiet"
+    local exit_code=$?
+
+    if [[ "$json_flag" == "true" ]]; then
+        db_query_json "SELECT * FROM gateway_health WHERE gateway_id = '$(sql_escape "$gateway")';" 2>/dev/null || echo "[]"
+    fi
+
+    return "$exit_code"
+}
+
+cmd_help() {
+    echo ""
+    echo "Fallback Chain Helper - Per-agent and global model fallback chains"
+    echo "=================================================================="
+    echo ""
+    echo "Usage: fallback-chain-helper.sh [command] [options]"
+    echo ""
+    echo "Commands:"
+    echo "  resolve <tier>          Resolve best model through fallback chain"
+    echo "  trigger <tier> <error>  Process error trigger and return next fallback"
+    echo "  chain <tier>            Show the full fallback chain for a tier"
+    echo "  status                  Show fallback chain health across all tiers"
+    echo "  validate                Validate fallback chain configuration"
+    echo "  gateway <provider>      Check gateway provider availability"
+    echo "  help                    Show this help"
+    echo ""
+    echo "Options:"
+    echo "  --config PATH     Override config file path"
+    echo "  --agent FILE      Use per-agent fallback chain from frontmatter"
+    echo "  --json            Output in JSON format"
+    echo "  --quiet           Suppress informational output"
+    echo "  --force           Bypass cache"
+    echo "  --max-depth N     Maximum chain depth (default: $DEFAULT_MAX_DEPTH)"
+    echo "  --failed-model M  Model that failed (for trigger command)"
+    echo ""
+    echo "Trigger types:"
+    echo "  api_error         Provider returned 5xx or connection failure"
+    echo "  timeout           Request exceeded timeout threshold"
+    echo "  rate_limit        Provider returned 429"
+    echo "  auth_error        Provider returned 401/403"
+    echo "  overloaded        Provider returned 529"
+    echo ""
+    echo "Model spec formats:"
+    echo "  provider/model                    Direct provider (e.g., anthropic/claude-sonnet-4)"
+    echo "  openrouter/provider/model         Via OpenRouter gateway"
+    echo "  gateway/cf/provider/model         Via Cloudflare AI Gateway"
+    echo ""
+    echo "Examples:"
+    echo "  # Resolve best model for coding tier"
+    echo "  fallback-chain-helper.sh resolve coding"
+    echo ""
+    echo "  # Resolve with per-agent chain override"
+    echo "  fallback-chain-helper.sh resolve sonnet --agent models/sonnet.md"
+    echo ""
+    echo "  # Process a rate limit trigger"
+    echo "  fallback-chain-helper.sh trigger coding 429 --failed-model anthropic/claude-opus-4-6"
+    echo ""
+    echo "  # Show chain for a tier"
+    echo "  fallback-chain-helper.sh chain opus"
+    echo ""
+    echo "  # Check OpenRouter gateway"
+    echo "  fallback-chain-helper.sh gateway openrouter"
+    echo ""
+    echo "  # Validate configuration"
+    echo "  fallback-chain-helper.sh validate"
+    echo ""
+    echo "Configuration:"
+    echo "  Global: $DEFAULT_CONFIG"
+    echo "  Per-agent: YAML frontmatter 'fallback-chain:' in model tier files"
+    echo "  Database: $FALLBACK_DB"
+    echo ""
+    echo "Integration:"
+    echo "  - model-availability-helper.sh: Uses for provider health checks"
+    echo "  - supervisor-helper.sh: Calls resolve/trigger during dispatch"
+    echo "  - Gateway providers: OpenRouter, Cloudflare AI Gateway"
+    echo ""
+    echo "Exit codes:"
+    echo "  0 - Model resolved successfully"
+    echo "  1 - No available model / usage error"
+    echo "  2 - Configuration error"
+    echo "  3 - All providers exhausted"
+    echo ""
+    return 0
+}
+
+# =============================================================================
+# Main
+# =============================================================================
+
+main() {
+    local command="${1:-help}"
+    shift || true
+
+    # Initialize DB for all commands except help
+    if [[ "$command" != "help" && "$command" != "--help" && "$command" != "-h" ]]; then
+        init_db || return 1
+    fi
+
+    case "$command" in
+        resolve)
+            cmd_resolve "$@"
+            ;;
+        trigger)
+            cmd_trigger "$@"
+            ;;
+        chain)
+            cmd_chain "$@"
+            ;;
+        status)
+            cmd_status "$@"
+            ;;
+        validate)
+            cmd_validate "$@"
+            ;;
+        gateway)
+            cmd_gateway "$@"
+            ;;
+        help|--help|-h)
+            cmd_help
+            ;;
+        *)
+            print_error "Unknown command: $command"
+            cmd_help
+            return 1
+            ;;
+    esac
+    return $?
+}
+
+main "$@"
diff --git a/.agents/scripts/model-availability-helper.sh b/.agents/scripts/model-availability-helper.sh
index bfcdcb2d..1ae3963c 100755
--- a/.agents/scripts/model-availability-helper.sh
+++ b/.agents/scripts/model-availability-helper.sh
@@ -755,6 +755,8 @@ _record_model_availability() {
 
 # Resolve the best available model for a given tier.
 # Checks primary model first, falls back to secondary if primary is unavailable.
+# If both fail, delegates to fallback-chain-helper.sh for extended chain resolution
+# including gateway providers (OpenRouter, Cloudflare AI Gateway).
 # Output: provider/model_id on stdout
 # Returns: 0 if a model was resolved, 1 if no model available for this tier
 resolve_tier() {
@@ -789,7 +791,56 @@ resolve_tier() {
         fi
     fi
 
-    [[ "$quiet" != "true" ]] && print_error "No available model for tier: $tier (tried $primary, $fallback)"
+    # Extended fallback: delegate to fallback-chain-helper.sh (t132.4)
+    # This walks the full configured chain including gateway providers
+    local chain_helper="${SCRIPT_DIR}/fallback-chain-helper.sh"
+    if [[ -x "$chain_helper" ]]; then
+        [[ "$quiet" != "true" ]] && print_info "Primary/fallback exhausted, trying extended fallback chain..."
+        local chain_resolved
+        chain_resolved=$("$chain_helper" resolve "$tier" --quiet 2>/dev/null) || true
+        if [[ -n "$chain_resolved" ]]; then
+            echo "$chain_resolved"
+            [[ "$quiet" != "true" ]] && print_warning "Resolved $tier -> $chain_resolved (via fallback chain)"
+            return 0
+        fi
+    fi
+
+    [[ "$quiet" != "true" ]] && print_error "No available model for tier: $tier (tried $primary, $fallback, and extended chain)"
+    return 1
+}
+
+# Resolve a model using the full fallback chain (t132.4).
+# Unlike resolve_tier which tries primary/fallback first, this goes directly
+# to the fallback chain configuration for maximum flexibility.
+# Supports per-agent overrides via --agent flag.
+resolve_tier_chain() {
+    local tier="$1"
+    local force="${2:-false}"
+    local quiet="${3:-false}"
+    local agent_file="${4:-}"
+
+    local chain_helper="${SCRIPT_DIR}/fallback-chain-helper.sh"
+    if [[ ! -x "$chain_helper" ]]; then
+        [[ "$quiet" != "true" ]] && print_warning "fallback-chain-helper.sh not found, falling back to resolve_tier"
+        resolve_tier "$tier" "$force" "$quiet"
+        return $?
+    fi
+
+    local -a chain_args=("resolve" "$tier")
+    [[ "$quiet" == "true" ]] && chain_args+=("--quiet")
+    [[ "$force" == "true" ]] && chain_args+=("--force")
+    [[ -n "$agent_file" ]] && chain_args+=("--agent" "$agent_file")
+
+    local resolved
+    resolved=$("$chain_helper" "${chain_args[@]}" 2>/dev/null) || true
+
+    if [[ -n "$resolved" ]]; then
+        echo "$resolved"
+        [[ "$quiet" != "true" ]] && print_success "Resolved $tier -> $resolved (via fallback chain)"
+        return 0
+    fi
+
+    [[ "$quiet" != "true" ]] && print_error "No available model for tier: $tier (fallback chain exhausted)"
     return 1
 }
 
@@ -1141,6 +1192,55 @@ cmd_invalidate() {
     return 0
 }
 
+# Resolve using the full fallback chain (t132.4).
+# Delegates to fallback-chain-helper.sh for extended chain resolution
+# including gateway providers and per-agent overrides.
+cmd_resolve_chain() {
+    local tier="${1:-}"
+    local force=false
+    local quiet=false
+    local json_flag=false
+    local agent_file=""
+    shift || true
+
+    while [[ $# -gt 0 ]]; do
+        case "$1" in
+            --force) force=true; shift ;;
+            --quiet) quiet=true; shift ;;
+            --json) json_flag=true; shift ;;
+            --agent) agent_file="${2:-}"; shift 2 ;;
+            *) shift ;;
+        esac
+    done
+
+    if [[ -z "$tier" ]]; then
+        print_error "Usage: model-availability-helper.sh resolve-chain <tier> [--agent file]"
+        print_info "Available tiers: haiku flash sonnet pro opus health eval coding"
+        return 1
+    fi
+
+    local resolved
+    resolved=$(resolve_tier_chain "$tier" "$force" "$quiet" "$agent_file")
+    local exit_code=$?
+
+    if [[ "$json_flag" == "true" ]]; then
+        if [[ $exit_code -eq 0 ]]; then
+            local provider model_id
+            provider="${resolved%%/*}"
+            model_id="${resolved#*/}"
+            echo "{\"tier\":\"$tier\",\"provider\":\"$provider\",\"model\":\"$model_id\",\"full_id\":\"$resolved\",\"status\":\"available\",\"method\":\"chain\"}"
+        else
+            echo "{\"tier\":\"$tier\",\"status\":\"exhausted\",\"method\":\"chain\"}"
+        fi
+    else
+        if [[ $exit_code -eq 0 ]]; then
+            echo "$resolved"
+        fi
+    fi
+
+    return "$exit_code"
+}
+
 cmd_help() {
     echo ""
     echo "Model Availability Helper - Probe before dispatch"
@@ -1153,7 +1253,8 @@ cmd_help() {
     echo "  probe [provider] [--all]     Probe providers (default: only those with keys)"
     echo "  status                       Show cached availability status"
     echo "  rate-limits                  Show rate limit data from cache"
-    echo "  resolve <tier>               Resolve best available model for tier (with fallback)"
+    echo "  resolve <tier>               Resolve best available model for tier (primary + fallback)"
+    echo "  resolve-chain <tier>         Resolve via full fallback chain (t132.4, includes gateways)"
     echo "  invalidate [provider]        Clear cache (all or specific provider)"
     echo "  help                         Show this help"
     echo ""
@@ -1162,6 +1263,7 @@ cmd_help() {
     echo "  --quiet       Suppress informational output"
     echo "  --force       Bypass cache and probe live"
     echo "  --ttl N       Override cache TTL in seconds"
+    echo "  --agent FILE  Per-agent fallback chain override (resolve-chain only)"
     echo ""
     echo "Tiers:"
     echo "  haiku   - Cheapest (triage, classification)"
@@ -1179,6 +1281,8 @@ cmd_help() {
     echo "  model-availability-helper.sh check sonnet"
     echo "  model-availability-helper.sh probe --all"
     echo "  model-availability-helper.sh resolve opus --json"
+    echo "  model-availability-helper.sh resolve-chain coding --json"
+    echo "  model-availability-helper.sh resolve-chain sonnet --agent models/sonnet.md"
     echo "  model-availability-helper.sh status"
     echo "  model-availability-helper.sh rate-limits --json"
     echo "  model-availability-helper.sh invalidate anthropic"
@@ -1190,6 +1294,9 @@ cmd_help() {
     echo "  # Resolve model with fallback for a tier:"
     echo "  MODEL=\$(model-availability-helper.sh resolve coding --quiet)"
     echo ""
+    echo "  # Resolve via full fallback chain (includes gateway providers):"
+    echo "  MODEL=\$(model-availability-helper.sh resolve-chain coding --quiet)"
+    echo ""
     echo "Exit codes:"
     echo "  0 - Available"
     echo "  1 - Unavailable or error"
@@ -1231,6 +1338,9 @@ main() {
         resolve)
             cmd_resolve "$@"
             ;;
+        resolve-chain|resolve_chain)
+            cmd_resolve_chain "$@"
+            ;;
         invalidate|clear|flush)
             cmd_invalidate "$@"
             ;;
diff --git a/.agents/scripts/supervisor-helper.sh b/.agents/scripts/supervisor-helper.sh
index a2c74534..ede4d9b5 100755
--- a/.agents/scripts/supervisor-helper.sh
+++ b/.agents/scripts/supervisor-helper.sh
@@ -2625,8 +2625,10 @@ resolve_ai_cli() {
 
 #######################################
 # Resolve the best available model for a given task tier
-# Uses model-availability-helper.sh for availability-aware resolution
-# with automatic fallback to cross-provider alternatives.
+# Uses fallback-chain-helper.sh (t132.4) for configurable multi-provider
+# fallback chains with gateway support, falling back to
+# model-availability-helper.sh (t132.3) for simple primary/fallback,
+# then static defaults.
 #
 # Tiers:
 #   coding  - Best SOTA model for code tasks (default)
@@ -2643,6 +2645,19 @@ resolve_model() {
         return 0
     fi
 
+    # Try fallback-chain-helper.sh for full chain resolution (t132.4)
+    # This walks the configured chain including gateway providers
+    local chain_helper="${SCRIPT_DIR}/fallback-chain-helper.sh"
+    if [[ -x "$chain_helper" ]]; then
+        local resolved
+        resolved=$("$chain_helper" resolve "$tier" --quiet 2>/dev/null) || true
+        if [[ -n "$resolved" ]]; then
+            echo "$resolved"
+            return 0
+        fi
+        log_verbose "fallback-chain-helper.sh could not resolve tier '$tier', trying availability helper"
+    fi
+
     # Try model-availability-helper.sh for availability-aware resolution (t132.3)
     local availability_helper="${SCRIPT_DIR}/model-availability-helper.sh"
     if [[ -x "$availability_helper" ]]; then
diff --git a/.agents/tools/ai-assistants/fallback-chains.md b/.agents/tools/ai-assistants/fallback-chains.md
new file mode 100644
index 00000000..575de399
--- /dev/null
+++ b/.agents/tools/ai-assistants/fallback-chains.md
@@ -0,0 +1,260 @@
+---
+description: Fallback chain configuration for multi-provider model resolution
+mode: subagent
+tools:
+  read: true
+  write: false
+  edit: false
+  bash: true
+  glob: true
+  grep: true
+  webfetch: false
+---
+
+# Fallback Chain Configuration
+
+<!-- AI-CONTEXT-START -->
+
+## Quick Reference
+
+- **Script**: `scripts/fallback-chain-helper.sh [resolve|trigger|chain|status|validate|gateway]`
+- **Config**: `configs/fallback-chain-config.json` (from `.json.txt` template)
+- **Per-agent**: YAML frontmatter `fallback-chain:` in model tier files
+- **Database**: `~/.aidevops/.agent-workspace/fallback-chain.db`
+- **Triggers**: api_error, timeout, rate_limit, auth_error, overloaded
+- **Gateways**: OpenRouter, Cloudflare AI Gateway
+
+<!-- AI-CONTEXT-END -->
+
+## Overview
+
+The fallback chain system provides configurable, multi-provider model resolution with automatic failover. When a provider fails (API error, timeout, rate limit), the system walks a chain of alternative providers until one succeeds.
+
+```text
+Request -> Primary Provider -> [FAIL] -> Fallback 1 -> [FAIL] -> Gateway Provider -> [OK]
+                                  |                        |
+                              cooldown                 cooldown
+```
+
+## Configuration Layers
+
+Fallback chains are resolved with this priority:
+
+1. **Per-agent frontmatter** -- `fallback-chain:` in model tier `.md` files
+2. **Global config** -- `configs/fallback-chain-config.json` tier-specific chains
+3. **Global default** -- `configs/fallback-chain-config.json` `default` chain
+4. **Hardcoded** -- Built-in minimal chains matching `model-availability-helper.sh`
+
+### Per-Agent Frontmatter
+
+Add `fallback-chain:` to any model tier file's YAML frontmatter:
+
+```yaml
+---
+model: anthropic/claude-sonnet-4-20250514
+model-tier: sonnet
+model-fallback: openai/gpt-4.1
+fallback-chain:
+  - anthropic/claude-sonnet-4-20250514
+  - openai/gpt-4.1
+  - google/gemini-2.5-pro
+  - openrouter/anthropic/claude-sonnet-4-20250514
+---
+```
+
+### Global Config
+
+Edit `configs/fallback-chain-config.json` (copy from `.json.txt` template):
+
+```json
+{
+  "chains": {
+    "sonnet": [
+      "anthropic/claude-sonnet-4-20250514",
+      "openai/gpt-4.1",
+      "google/gemini-2.5-pro",
+      "openrouter/anthropic/claude-sonnet-4-20250514"
+    ]
+  }
+}
+```
+
+## Model Spec Formats
+
+| Format | Example | Description |
+|--------|---------|-------------|
+| `provider/model` | `anthropic/claude-sonnet-4-20250514` | Direct provider API |
+| `openrouter/provider/model` | `openrouter/anthropic/claude-sonnet-4-20250514` | Via OpenRouter gateway |
+| `gateway/cf/provider/model` | `gateway/cf/anthropic/claude-sonnet-4-20250514` | Via Cloudflare AI Gateway |
+
+## Trigger Types
+
+Triggers activate fallback when specific error conditions are detected:
+
+| Trigger | HTTP Codes | Default Cooldown | Description |
+|---------|-----------|-----------------|-------------|
+| `api_error` | 500, 502, 503, 504 | 5 minutes | Server errors, connection failures |
+| `timeout` | -- | 3 minutes | Request exceeded timeout |
+| `rate_limit` | 429 | 1 minute | Rate limited by provider |
+| `auth_error` | 401, 403 | 1 hour | Invalid or expired API key |
+| `overloaded` | 529 | 2 minutes | Provider capacity exceeded |
+
+Triggers can be enabled/disabled and cooldowns customized in the config:
+
+```json
+{
+  "triggers": {
+    "rate_limit": {
+      "enabled": true,
+      "cooldown_seconds": 60
+    },
+    "auth_error": {
+      "enabled": true,
+      "cooldown_seconds": 3600
+    }
+  }
+}
+```
+
+## Gateway Providers
+
+Gateway providers route requests through a unified API, providing provider-level fallback without needing individual API keys for every provider.
+
+### OpenRouter
+
+OpenRouter provides access to 100+ models through a single API key.
+
+```bash
+# Check OpenRouter availability
+fallback-chain-helper.sh gateway openrouter
+
+# Models routed via OpenRouter use the format:
+# openrouter/provider/model
+# e.g., openrouter/anthropic/claude-sonnet-4-20250514
+```
+
+**Setup**: Set `OPENROUTER_API_KEY` environment variable or store via `aidevops secret set OPENROUTER_API_KEY`.
+
+### Cloudflare AI Gateway
+
+Cloudflare AI Gateway adds caching, rate limiting, and analytics on top of any provider.
+
+```bash
+# Check Cloudflare AI Gateway availability
+fallback-chain-helper.sh gateway cloudflare
+
+# Models routed via CF AI Gateway use the format:
+# gateway/cf/provider/model
+# e.g., gateway/cf/anthropic/claude-sonnet-4-20250514
+```
+
+**Setup**: Configure `account_id` and `gateway_id` in `configs/fallback-chain-config.json`. Set `CF_AIG_TOKEN` for authenticated gateways.
+
+## CLI Usage
+
+```bash
+# Resolve best model for a tier (walks the chain)
+fallback-chain-helper.sh resolve coding
+fallback-chain-helper.sh resolve sonnet --json
+
+# Resolve with per-agent override
+fallback-chain-helper.sh resolve sonnet --agent models/sonnet.md
+
+# Process an error trigger (puts failed provider in cooldown, returns next)
+fallback-chain-helper.sh trigger coding 429 --failed-model anthropic/claude-opus-4-6
+
+# Show chain for a tier
+fallback-chain-helper.sh chain opus
+
+# Show overall status (cooldowns, gateways, recent triggers)
+fallback-chain-helper.sh status
+
+# Validate configuration
+fallback-chain-helper.sh validate
+
+# Check gateway health
+fallback-chain-helper.sh gateway openrouter
+fallback-chain-helper.sh gateway cloudflare
+```
+
+## Integration
+
+### Supervisor (automatic)
+
+The supervisor's `resolve_model()` function automatically uses the fallback chain:
+
+```text
+resolve_model("coding")
+  -> fallback-chain-helper.sh resolve coding    (t132.4: full chain)
+  -> model-availability-helper.sh resolve coding (t132.3: primary/fallback)
+  -> static defaults                             (hardcoded last resort)
+```
+
+### Model Availability Helper
+
+The `resolve` command now falls through to the fallback chain when primary/fallback both fail:
+
+```bash
+# Simple resolution (primary + single fallback)
+model-availability-helper.sh resolve coding
+
+# Full chain resolution (all configured providers + gateways)
+model-availability-helper.sh resolve-chain coding
+model-availability-helper.sh resolve-chain sonnet --agent models/sonnet.md
+```
+
+### Error Recovery in Workers
+
+Workers can use the trigger command to handle runtime errors:
+
+```bash
+# Worker encounters rate limit from Anthropic
+NEXT_MODEL=$(fallback-chain-helper.sh trigger coding 429 \
+  --failed-model anthropic/claude-opus-4-6 --quiet)
+
+# Re-dispatch with the fallback model
+opencode run -m "$NEXT_MODEL" "Continue the task..."
+```
+
+## Architecture
+
+```text
+                    ┌─────────────────────────────────────┐
+                    │        Fallback Chain Config          │
+                    │  (per-agent frontmatter > global)     │
+                    └──────────────┬──────────────────────┘
+                                   │
+                    ┌──────────────▼──────────────────────┐
+                    │     fallback-chain-helper.sh          │
+                    │  ┌─────────────────────────────────┐ │
+                    │  │ Trigger Detection                │ │
+                    │  │ (429, 5xx, timeout, auth, 529)   │ │
+                    │  └──────────┬──────────────────────┘ │
+                    │             │                         │
+                    │  ┌──────────▼──────────────────────┐ │
+                    │  │ Provider Cooldown Manager        │ │
+                    │  │ (SQLite, per-provider TTL)       │ │
+                    │  └──────────┬──────────────────────┘ │
+                    │             │                         │
+                    │  ┌──────────▼──────────────────────┐ │
+                    │  │ Chain Walker                     │ │
+                    │  │ (skip cooled-down providers)     │ │
+                    │  └──────────┬──────────────────────┘ │
+                    └─────────────┼───────────────────────┘
+                                  │
+              ┌───────────────────┼───────────────────┐
+              │                   │                   │
+     ┌────────▼──────┐  ┌────────▼──────┐  ┌────────▼──────┐
+     │ Direct Provider│  │  OpenRouter   │  │  CF AI Gateway │
+     │ (Anthropic,    │  │  (unified API)│  │  (cache+route) │
+     │  OpenAI, etc.) │  │              │  │               │
+     └───────────────┘  └──────────────┘  └───────────────┘
+```
+
+## Related
+
+- `scripts/model-availability-helper.sh` -- Provider health probes and tier resolution
+- `scripts/model-registry-helper.sh` -- Model registry with periodic sync
+- `scripts/supervisor-helper.sh` -- Autonomous task orchestration
+- `tools/ai-assistants/models/README.md` -- Model tier definitions
+- `services/hosting/cloudflare-platform/references/ai-gateway/README.md` -- CF AI Gateway reference
diff --git a/.agents/tools/ai-assistants/models/README.md b/.agents/tools/ai-assistants/models/README.md
index 07a9a5f6..9d515360 100644
--- a/.agents/tools/ai-assistants/models/README.md
+++ b/.agents/tools/ai-assistants/models/README.md
@@ -41,14 +41,31 @@ The supervisor resolves model tiers from subagent frontmatter:
 2. Supervisor reads `models/pro.md` frontmatter for concrete model ID
 3. Dispatches runner with `--model` flag set to the resolved model
 
+## Fallback Chains (t132.4)
+
+Each tier supports a configurable fallback chain that goes beyond the simple primary/fallback pair. When a provider fails (API error, timeout, rate limit), the system walks the chain until a healthy provider is found, including gateway providers like OpenRouter and Cloudflare AI Gateway.
+
+Add `fallback-chain:` to any model tier's YAML frontmatter for per-agent overrides:
+
+```yaml
+fallback-chain:
+  - anthropic/claude-sonnet-4-20250514
+  - openai/gpt-4.1
+  - google/gemini-2.5-pro
+  - openrouter/anthropic/claude-sonnet-4-20250514
+```
+
+Global defaults are configured in `configs/fallback-chain-config.json`. See `tools/ai-assistants/fallback-chains.md` for full documentation.
+
 ## Adding New Models
 
 1. Create a new subagent file in this directory
 2. Set `model:` in YAML frontmatter to the provider/model ID
-3. Add to the tier mapping in `model-routing.md`
-4. Add to `compare-models-helper.sh` MODEL_DATA if tracking pricing
-5. Run `model-registry-helper.sh sync --force` to update the registry
-6. Run `model-registry-helper.sh check` to verify availability
+3. Optionally add `fallback-chain:` for per-agent chain override
+4. Add to the tier mapping in `model-routing.md`
+5. Add to `compare-models-helper.sh` MODEL_DATA if tracking pricing
+6. Run `model-registry-helper.sh sync --force` to update the registry
+7. Run `model-registry-helper.sh check` to verify availability
 
 ## Model Registry
 
@@ -71,7 +88,9 @@ The registry runs automatically on `aidevops update` and can be added to cron fo
 
 ## Related
 
+- `tools/ai-assistants/fallback-chains.md` — Fallback chain configuration and gateway providers
 - `tools/context/model-routing.md` — Cost-aware routing rules
 - `compare-models-helper.sh discover` — Detect available providers
 - `model-registry-helper.sh` — Provider/model registry with periodic sync
+- `fallback-chain-helper.sh` — Fallback chain resolution with trigger detection
 - `tools/ai-assistants/headless-dispatch.md` — CLI dispatch with model selection
diff --git a/.agents/tools/ai-assistants/models/opus.md b/.agents/tools/ai-assistants/models/opus.md
index e1988089..5e9f5c8d 100644
--- a/.agents/tools/ai-assistants/models/opus.md
+++ b/.agents/tools/ai-assistants/models/opus.md
@@ -4,6 +4,11 @@ mode: subagent
 model: anthropic/claude-opus-4-20250514
 model-tier: opus
 model-fallback: openai/o3
+fallback-chain:
+  - anthropic/claude-opus-4-6
+  - openai/o3
+  - anthropic/claude-sonnet-4-20250514
+  - openrouter/anthropic/claude-opus-4-6
 tools:
   read: true
   write: true
diff --git a/.agents/tools/ai-assistants/models/sonnet.md b/.agents/tools/ai-assistants/models/sonnet.md
index d4885c2d..4a4708c8 100644
--- a/.agents/tools/ai-assistants/models/sonnet.md
+++ b/.agents/tools/ai-assistants/models/sonnet.md
@@ -4,6 +4,11 @@ mode: subagent
 model: anthropic/claude-sonnet-4-20250514
 model-tier: sonnet
 model-fallback: openai/gpt-4.1
+fallback-chain:
+  - anthropic/claude-sonnet-4-20250514
+  - openai/gpt-4.1
+  - google/gemini-2.5-pro
+  - openrouter/anthropic/claude-sonnet-4-20250514
 tools:
   read: true
   write: true