diff --git a/config.lua b/config.lua
index ede80da..0a5bb05 100644
--- a/config.lua
+++ b/config.lua
@@ -146,4 +146,49 @@ return {
     --     -- (cloud may have variable cost per session).
     --     summarizer_model = "fast",
     -- },
+
+    -- Phase 5 (docs/PHASE5.md): multi-model routing + cloud fallback +
+    -- summarize-on-evict. OFF by default — auto-routing can spend money
+    -- silently on the cloud preset; require explicit opt-in.
+    --
+    -- routing = {
+    --     -- Enable auto-routing per request. When true, router.classify_model
+    --     -- inspects each prompt and may switch the model for THAT request
+    --     -- only (the :model selection is preserved across requests).
+    --     -- Default false. Toggle at runtime with :route on / :route off.
+    --     auto = true,
+    --
+    --     -- Class → model mapping. nil = "keep current" (heuristic fires
+    --     -- but no override). Ships with reasoning = nil because mapping
+    --     -- "explain ..." prompts to a paid cloud model would spend money
+    --     -- silently — opt in by uncommenting the reasoning line below.
+    --     classes = {
+    --         code      = "deep",      -- code-like prompts to local deep
+    --         -- reasoning = "cloud",  -- OPT-IN: "explain"/"why"/"how does" → paid
+    --         -- default   = nil,      -- keep active model
+    --     },
+    --
+    --     -- Single-hop retry on transport failure (HTTP 5xx, 408,
+    --     -- 404 model_not_found, DNS, connection refused, timeouts).
+    --     -- Retries against fallback_model once. Skipped if any text
+    --     -- has already streamed (no partial-output duplication).
+    --     -- Toggle at runtime with :fallback on / :fallback off.
+    --     fallback       = false,           -- default off (cost-safety)
+    --     fallback_model = "cloud",
+    -- },
+
+    -- ── Phase 5 context summarization on sliding-window eviction.
+    -- Set INSIDE the context = { ... } block above to enable:
+    --     context = {
+    --         max_turns          = 40,
+    --         token_budget       = 4096,
+    --         summarize_on_evict = true,
+    --         summarizer_model   = "fast",   -- model name in models{}
+    --         max_summary_chars  = 2000,
+    --     },
+    -- When summarize_on_evict is true, evicted turn pairs are fed to
+    -- summarizer_model and the result lives on ctx.summary, appended to
+    -- the system prompt as [earlier conversation summary]. Suppressed
+    -- in Norris mode (R-C4 — planner stays on its goal). If broker
+    -- fails, falls back to Phase 0 silent eviction (no crash).
 }