diff --git a/IMPLEMENTATION_PLAN.md b/IMPLEMENTATION_PLAN.md
new file mode 100644
index 0000000..9ada0b2
--- /dev/null
+++ b/IMPLEMENTATION_PLAN.md
@@ -0,0 +1,211 @@
+# Full Jolt Implementation Plan
+
+## Strategy
+
+Minimal Janet bootstrap (parser + var system + namespace system + core types)
+→ load SCI's Clojure source → rest of stdlib is Clojure.
+
+Jolt already has 3 phases matching SCI's architecture:
+- Parser: reader.janet (hand-rolled, works)
+- Analyzer: compiler.janet (2-phase: analyze-form → emit-expr)
+- Evaluator: evaluator.janet (interpreter) + Janet's native eval (compiled path)
+
+## Phase 0: Fix defn Bug + Symbol Resolution (now)
+
+### 0.1: Bare symbols must go through compile path too
+In api.janet eval-string, change:
+  (if (and compile? (array? form))  → also true for bare symbols
+Only skip compiler for literal values (nil, numbers, strings, keywords, booleans).
+Everything else → compile-and-eval.
+
+### 0.2: compile-and-eval for def must intern in Jolt namespace
+After (eval (compile-ast form ctx)), if the form is a def:
+  (ns-intern ns (name-sym :name) val)
+So the interpreter can find the var later.
+
+### 0.3: Add defn to Phase 6 tests
+Test: (defn foo [x] x) → (foo 1) = 1, foo returns the fn
+
+## Phase 1: Complete Var/Namespace System
+
+### 1.1: Full Var semantics
+- Var with dynamic bindings (push-thread-bindings/pop-thread-bindings)
+- binding macro (already exists in evaluator, needs compiler support)
+- alter-var-root, var-get, var-set
+- ^:dynamic metadata
+- ^:macro metadata (already there)
+- Var metadata (already there)
+
+### 1.2: Full Namespace system
+- ns form with :require, :use, :import, :refer-clojure, :refer
+- create-ns, find-ns, all-ns, remove-ns
+- ns-aliases, ns-refers, ns-imports
+- ns-name, ns-map, ns-interns
+- in-ns (already there)
+
+### 1.3: Interop symbol resolution
+- clojure.core/* for fully qualified
+- ns-alias/name for aliased
+- Import resolution (ClassName → constructor)
+
+Tests: Port SCI's var_test.cljs and ns_test.cljs
+
+## Phase 2: Complete Core Library
+
+### 2.1: PersistentHashMap
+Port from CLJS (cljs.core/PersistentHashMap) using hash-array-mapped trie.
+Current Janet struct fallback is O(n). Need:
+- Array-based HAMT with 32-way branching
+- hash and = consistent with Clojure semantics
+- transient support for bulk operations
+
+### 2.2: PersistentHashSet  
+Port from CLJS. Wrap PersistentHashMap with sentinel values.
+
+### 2.3: Lazy Sequences
+- LazySeq type
+- lazy-seq macro
+- Realize-once semantics
+- Sequence caching (already computed? check)
+
+### 2.4: Remaining clojure.core fns (ported from SCI)
+- clojure.string (port from CLJS)
+- clojure.set (port from CLJS)  
+- Sequence library: partition, split-at, split-with, interleave, interpose
+- Reducers: reduce-kv, keep, keep-indexed
+- sorted maps/sets (skip for now — use hash-based)
+- chunked sequences (skip for now)
+
+## Phase 3: Protocol System
+
+### 3.1: defprotocol
+Port from SCI. Protocols are maps of method-name → dispatch-fn.
+Protocol methods compile to calls through the protocol dispatch table.
+
+### 3.2: extend-type / extend-protocol
+Type → protocol method implementations.
+Stored in type metadata.
+
+### 3.3: reify
+Anonymous type implementing protocols.
+
+### 3.4: satisfies? / extends?
+Runtime protocol check.
+
+Tests: Port SCI's protocol tests
+
+## Phase 4: deftype / defrecord (Complete)
+
+### 4.1: deftype with mutable fields
+- ^:volatile-mutable / ^:unsynchronized-mutable
+- Field accessors (.field obj)
+- Field mutation (set! (.-field obj) val)
+
+### 4.2: defrecord
+- Creates type + factories (→RecordName, map->RecordName)
+- IPersistentMap implementation
+- equals/hashCode based on type + fields
+
+## Phase 5: Multimethods
+
+### 5.1: Hierarchy
+- derive, isa?, ancestors, descendants
+- make-hierarchy
+- Global hierarchy atom
+
+### 5.2: defmulti / defmethod
+- Dispatch function
+- Method dispatch via hierarchy
+- :default dispatch value
+- prefer-method
+
+## Phase 6: Reader Extensions
+
+### 6.1: Tagged Literals
+- #inst, #uuid
+- default-data-readers
+- *data-readers* dynamic var
+
+### 6.2: Reader Conditionals
+- #? and #?@ for platform-specific code
+- Feature expressions (:clj, :cljs, :jolt)
+
+### 6.3: Metadata reader
+- ^:key val and ^{:key val} forms
+- Attach metadata to any form
+
+## Phase 7: SCI Bootstrap
+
+### 7.1: Load SCI source
+- Parse and load sci.core, sci.lang, sci.impl.* namespaces
+- Expose Jolt runtime as Clojure vars (types, vars, namespaces)
+- SCI's Clojure code runs on Jolt's eval stack
+
+### 7.2: Benchmark
+- Compare Jolt (Janet) vs Jolt+SCI (Clojure-on-Jolt)
+- Use SCI's existing benchmark suite
+- Identify bottlenecks for optimization
+
+## Phase 8: Compiler Optimization
+
+### 8.1: Better symbol resolution
+- Known locals → direct Janet var access
+- Known core fns → direct fn invocation (already done)
+- Var deref → inline deref
+
+### 8.2: Loop optimization
+- Primitive loop/recur (already done with closure-based)
+- Tail-call optimization for self-recursion
+
+### 8.3: Inlining
+- Small core functions (inc, dec, +, -) inlined
+- Type hints for numeric ops
+
+## Phase 9: Integration Testing
+
+### 9.1: Port CLJS test suite
+- collections_test.cljs → Jolt
+- core_test.cljs → Jolt
+- seqs_test.cljs → Jolt
+- predicates_test.cljs → Jolt
+- recur_test.cljs → Jolt
+
+### 9.2: Self-hosting test
+- Jolt running Jolt's own test suite
+- Jolt running SCI's test suite
+
+## Phase 10: Standard Library (Clojure-written)
+
+### 10.1: Port from CLJS/SCI
+- clojure.string
+- clojure.set  
+- clojure.walk
+- clojure.zip
+- clojure.edn (reader already, need writer)
+- clojure.java.io (Janet file I/O)
+
+### 10.2: Jolt-specific
+- jolt.interop (Janet interop)
+- jolt.shell (Janet shell commands)
+- jolt.http (Janet HTTP client)
+
+## Implementation Order
+
+1. Phase 0 (defn bug) — **now**
+2. Phase 1 (var/ns system) — **this week**
+3. Phase 2 (core library) — **next week**
+4. Phase 6 (reader extensions) — allows loading SCI directly
+5. Phase 7 (SCI bootstrap) — critical path
+6. Phases 3-5 (protocols, deftype, multimethods) — as needed by SCI
+7. Phases 8-10 (optimization, testing, stdlib) — polish
+
+## Testing Strategy
+
+Each phase: write tests FIRST (TDD), then implement.
+
+Test files follow: test/<feature>_test.janet
+  - Literal/source tests: (assert (= "expected" (compile-str "input")) "label")
+  - Round-trip tests: (assert (= val (ct-eval ctx "input")) "label")  
+  - Integration tests: load .clj files, eval, verify namespaces/vars
+
+Run: janet test/<feature>_test.janet (single) or jpm test (all)
diff --git a/src/jolt/api.janet b/src/jolt/api.janet
index c50f035..e932704 100644
--- a/src/jolt/api.janet
+++ b/src/jolt/api.janet
@@ -49,19 +49,27 @@
   [ctx s]
   (let [compile? (get (ctx :env) :compile?)
         form (parse-string s)]
-    (if (and compile? (array? form))
-      (let [first-form (first form)
-            head-name (if (and (struct? first-form) (= :symbol (first-form :jolt/type)))
-                       (first-form :name)
-                       nil)
-            stateful? (or (= head-name "defmacro") (= head-name "ns")
-                          (= head-name "deftype") (= head-name "defmulti") (= head-name "defmethod")
-                          (= head-name "require") (= head-name "in-ns")
-                          (= head-name "syntax-quote") (= head-name "set!")
-                          (= head-name "var") (= head-name ".") (= head-name "new"))]
-        (if stateful?
-          (eval-form ctx @{} form)
-          (compile-and-eval form ctx)))
+    (if compile?
+      (if (array? form)
+        # Lists: check for stateful forms
+        (let [first-form (first form)
+              head-name (if (and (struct? first-form) (= :symbol (first-form :jolt/type)))
+                         (first-form :name)
+                         nil)
+              stateful? (or (= head-name "defmacro") (= head-name "ns")
+                            (= head-name "deftype") (= head-name "defmulti") (= head-name "defmethod")
+                            (= head-name "require") (= head-name "in-ns")
+                            (= head-name "syntax-quote") (= head-name "set!")
+                            (= head-name "var") (= head-name ".") (= head-name "new"))]
+          (if stateful?
+            (eval-form ctx @{} form)
+            (compile-and-eval form ctx)))
+        # Bare symbols and other non-literal forms: also compile
+        (if (or (and (struct? form) (= :symbol (form :jolt/type)))
+                (tuple? form))
+          (compile-and-eval form ctx)
+          (eval-form ctx @{} form)))
+      # No compile flag: always interpret
       (eval-form ctx @{} form))))
 
 (defn eval-string*
diff --git a/src/jolt/compiler.janet b/src/jolt/compiler.janet
index b806c94..761e4db 100644
--- a/src/jolt/compiler.janet
+++ b/src/jolt/compiler.janet
@@ -831,6 +831,18 @@
   (emit-expr (analyze-form form @{} ctx)))
 
 (defn compile-and-eval
-  "Compile a Clojure form and evaluate it as Janet."
+  "Compile a Clojure form and evaluate it as Janet.
+  For def/defn forms, interns the result in the Jolt namespace
+  so the interpreter can resolve it later."
   [form ctx]
-  (eval (compile-ast form ctx)))
+  (def result (eval (compile-ast form ctx)))
+  # Intern def/defn results in Jolt namespace for interpreter resolution
+  (when (and ctx (array? form) (> (length form) 0)
+             (struct? (first form)) (= :symbol ((first form) :jolt/type)))
+    (def head-name ((first form) :name))
+    (when (or (= head-name "def") (= head-name "defn") (= head-name "defn-"))
+      (def name-sym (in form 1))
+      (def name (if (struct? name-sym) (name-sym :name) name-sym))
+      (def ns (ctx-find-ns ctx (ctx-current-ns ctx)))
+      (ns-intern ns name result)))
+  result)
diff --git a/test/compiler-test.janet b/test/compiler-test.janet
index cdcaaa7..6575c70 100644
--- a/test/compiler-test.janet
+++ b/test/compiler-test.janet
@@ -201,3 +201,25 @@
 (print "  passed")
 
 (print "\nAll compiler Phase 5 tests passed!")
+
+# ============================================================
+# 13. defn/def integration (Phase 0 fix)
+# ============================================================
+(print "13: defn/def integration...")
+(use ../src/jolt/api)
+
+(let [ctx (init {:compile? true})]
+  # defn produces a resolvable var
+  (eval-string ctx "(defn identity-fn [x] x)")
+  (assert (= 1 (eval-string ctx "(identity-fn 1)")) "defn works")
+  (let [f (eval-string ctx "identity-fn")]
+    (assert (function? f) "bare defn symbol returns fn"))
+
+  # def produces a resolvable var
+  (eval-string ctx "(def answer 42)")
+  (assert (= 42 (eval-string ctx "answer")) "def bare symbol")
+  (assert (= 43 (eval-string ctx "(inc answer)")) "def in call"))
+
+(print "  passed")
+
+(print "\nAll compiler tests passed!")