feat: graph patch grammar DSL for causal editor

New grammar panel replaces free-text AI prompt with a two-step workflow:
1. NL to Grammar: GPT-4o converts description to patch ops (new endpoint ai-to-grammar)
2. Apply: frontend parser applies grammar locally without AI

Grammar syntax: (+|-|~)(node|edge|coef|input|instruments) key=val key=val
Sign shortcuts: + positive, - negative, = neutral
Auto-positions new nodes when x/y omitted.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/pages/CausalLab.tsx

@@ -394,6 +394,172 @@ function GraphLegend() {
   )
 }
 
+// ── Graph Patch Grammar ───────────────────────────────────────────────────────
+// Syntax: (+|-|~)(node|edge|coef|input|instruments) key=val key="val with spaces"
+// sign shortcuts: + positive  - negative  = neutral
+
+interface GrammarOp {
+  op: '+' | '-' | '~'
+  entity: 'node' | 'edge' | 'coef' | 'input' | 'instruments'
+  args: Record<string, string>
+  raw: string
+}
+
+function parseGrammarArgs(s: string): Record<string, string> {
+  const res: Record<string, string> = {}
+  const re = /(\w+)=(?:"([^"]*)"|([\S]*))/g
+  let m: RegExpExecArray | null
+  while ((m = re.exec(s)) !== null) res[m[1]] = m[2] !== undefined ? m[2] : m[3]
+  return res
+}
+
+function parseGrammar(text: string): { ops: GrammarOp[]; errors: string[] } {
+  const ops: GrammarOp[] = []; const errors: string[] = []
+  for (const rawLine of text.split('\n')) {
+    const line = rawLine.trim()
+    if (!line || line.startsWith('#')) continue
+    const m = line.match(/^([+\-~])(node|edge|coef|input|instruments)\s*(.*)/i)
+    if (!m) { errors.push(`Ligne non reconnue: "${line}"`); continue }
+    const entity = m[2].toLowerCase() as GrammarOp['entity']
+    const args = entity === 'instruments' ? { list: m[3].trim() } : parseGrammarArgs(m[3])
+    ops.push({ op: m[1] as '+' | '-' | '~', entity, args, raw: line })
+  }
+  return { ops, errors }
+}
+
+function resolveSign(s?: string): 'positive' | 'negative' | 'neutral' {
+  if (!s) return 'neutral'
+  if (s === '+' || s === 'positive') return 'positive'
+  if (s === '-' || s === 'negative') return 'negative'
+  return 'neutral'
+}
+
+function applyGrammarOps(state: EditorState, ops: GrammarOp[]): { state: EditorState; errors: string[] } {
+  let s: EditorState = {
+    ...state,
+    nodes: [...state.nodes], edges: [...state.edges],
+    coefficients: { ...state.coefficients }, inputMapping: { ...state.inputMapping },
+    instruments: [...state.instruments],
+  }
+  const errors: string[] = []
+
+  for (const op of ops) {
+    try {
+      if (op.entity === 'node') {
+        const { id, label, type, x, y, formula, unit, instrument } = op.args
+        if (op.op === '+') {
+          if (!id) { errors.push('+node: id manquant'); continue }
+          if (s.nodes.find(n => n.id === id)) { errors.push(`+node: "${id}" existe déjà`); continue }
+          const autoY = s.nodes.length ? Math.max(...s.nodes.map(n => n.y)) + 120 : 200
+          s.nodes = [...s.nodes, {
+            id, label: label ?? id,
+            type: (type ?? 'observable') as CausalNode['type'],
+            x: x ? +x : 300, y: y ? +y : autoY,
+            ...(formula ? { formula } : {}), ...(unit ? { unit } : {}), ...(instrument ? { instrument } : {}),
+          }]
+        } else if (op.op === '-') {
+          const tid = id ?? Object.values(op.args)[0]
+          if (!tid) { errors.push('-node: id manquant'); continue }
+          s.nodes = s.nodes.filter(n => n.id !== tid)
+          s.edges = s.edges.filter(e => e.from !== tid && e.to !== tid)
+          const im = { ...s.inputMapping }; delete im[tid]; s.inputMapping = im
+        } else {
+          if (!id) { errors.push('~node: id manquant'); continue }
+          s.nodes = s.nodes.map(n => n.id !== id ? n : {
+            ...n,
+            ...(label !== undefined ? { label } : {}),
+            ...(type !== undefined ? { type: type as CausalNode['type'] } : {}),
+            ...(x !== undefined ? { x: +x } : {}),
+            ...(y !== undefined ? { y: +y } : {}),
+            ...(formula !== undefined ? { formula } : {}),
+            ...(unit !== undefined ? { unit } : {}),
+            ...(instrument !== undefined ? { instrument } : {}),
+          })
+        }
+      } else if (op.entity === 'edge') {
+        const { from, to, sign, s: str, style, label, lag, decay } = op.args
+        if (op.op === '+') {
+          if (!from || !to) { errors.push('+edge: from/to manquants'); continue }
+          s.edges = [...s.edges, {
+            from, to, sign: resolveSign(sign),
+            strength: (str ? +str : 2) as 1|2|3,
+            style: (style ?? 'solid') as 'solid'|'dashed',
+            ...(label ? { label } : {}),
+            ...(lag !== undefined ? { lag_days: +lag } : {}),
+            ...(decay !== undefined ? { decay_days: decay === 'null' ? null : +decay } : {}),
+          }]
+        } else if (op.op === '-') {
+          if (!from || !to) { errors.push('-edge: from/to manquants'); continue }
+          s.edges = s.edges.filter(e => !(e.from === from && e.to === to))
+        } else {
+          if (!from || !to) { errors.push('~edge: from/to manquants'); continue }
+          s.edges = s.edges.map(e => (e.from !== from || e.to !== to) ? e : {
+            ...e,
+            ...(sign !== undefined ? { sign: resolveSign(sign) } : {}),
+            ...(str !== undefined ? { strength: +str as 1|2|3 } : {}),
+            ...(style !== undefined ? { style: style as 'solid'|'dashed' } : {}),
+            ...(label !== undefined ? { label } : {}),
+            ...(lag !== undefined ? { lag_days: +lag } : {}),
+            ...(decay !== undefined ? { decay_days: decay === 'null' ? null : +decay } : {}),
+          })
+        }
+      } else if (op.entity === 'coef') {
+        const { key, value, desc } = op.args
+        if (op.op === '+') {
+          if (!key || value === undefined) { errors.push('+coef: key/value manquants'); continue }
+          s.coefficients = { ...s.coefficients, [key]: { value: +value, calibrated: null, description: desc ?? '' } }
+        } else if (op.op === '-') {
+          if (!key) { errors.push('-coef: key manquant'); continue }
+          const cc = { ...s.coefficients }; delete cc[key]; s.coefficients = cc
+        } else {
+          if (!key) { errors.push('~coef: key manquant'); continue }
+          const ex = s.coefficients[key] ?? { value: 0, calibrated: null, description: '' }
+          s.coefficients = { ...s.coefficients, [key]: {
+            ...ex,
+            ...(value !== undefined ? { value: +value } : {}),
+            ...(desc !== undefined ? { description: desc } : {}),
+          }}
+        }
+      } else if (op.entity === 'input') {
+        const { node, source, key } = op.args
+        if (op.op === '-') {
+          if (!node) { errors.push('-input: node manquant'); continue }
+          const im = { ...s.inputMapping }; delete im[node]; s.inputMapping = im
+        } else {
+          if (!node || !source) { errors.push(`${op.op}input: node/source manquants`); continue }
+          s.inputMapping = { ...s.inputMapping, [node]: { source: source as InputMapping['source'], ...(key ? { key } : {}) } }
+        }
+      } else if (op.entity === 'instruments') {
+        const list = op.args.list?.split(',').map(x => x.trim()).filter(Boolean)
+        if (list?.length) s.instruments = list
+      }
+    } catch (e) { errors.push(`Erreur "${op.raw}": ${e}`) }
+  }
+  return { state: s, errors }
+}
+
+const GRAMMAR_REFERENCE = `# Nœuds
++node id=<id> label="<texte>" type=<macro_event|observable|latent|market_asset> [x=<n>] [y=<n>] [instrument=<str>]
+~node id=<id>  [label="..."] [type=...] [x=<n>] [y=<n>] [instrument=<str>]
+-node id=<id>
+
+# Arêtes  (sign: + positif  - négatif  = neutre)
++edge from=<id> to=<id> [sign=+|-|=] [s=1|2|3] [style=solid|dashed] [label="..."] [lag=<j>] [decay=<j|null>]
+~edge from=<id> to=<id>  [...mêmes champs...]
+-edge from=<id> to=<id>
+
+# Coefficients
++coef key=<str> value=<float> [desc="..."]
+~coef key=<str> [value=<float>] [desc="..."]
+-coef key=<str>
+
+# Mapping d'entrée
+~input node=<id> source=<surprise|actual_value|user_input|impact_score_scaled> [key=<str>]
+-input node=<id>
+
+# Instruments de sortie
+~instruments EURUSD,SP500,...`
+
 // ── Tab: Bibliothèque ─────────────────────────────────────────────────────────
 
 function TabLibrary({
@@ -932,9 +1098,12 @@ function TabEditor({ initialId }: { initialId?: number | null }) {
   const [saving, setSaving]         = useState(false)
   const [msg, setMsg]               = useState<{ ok: boolean; text: string } | null>(null)
   const [dataSources, setDS]        = useState<DataSources>({ prices: [], macro_series: [], ff_events: [] })
-  const [aiPrompt, setAiPrompt]     = useState('')
-  const [aiLoading, setAiLoading]   = useState(false)
-  const [aiError, setAiError]       = useState<string | null>(null)
+  const [grammarText, setGrammarText]   = useState('')
+  const [grammarErrors, setGrammarErrors] = useState<string[]>([])
+  const [grammarApplied, setGrammarApplied] = useState(0)  // count of applied ops
+  const [aiLoading, setAiLoading]       = useState(false)
+  const [aiError, setAiError]           = useState<string | null>(null)
+  const [showGrammarRef, setShowGrammarRef] = useState(false)
   const svgRef                      = useRef<SVGSVGElement>(null)
 
   useEffect(() => {
@@ -965,24 +1134,18 @@ function TabEditor({ initialId }: { initialId?: number | null }) {
     if (t) applyTemplateToState(t)
   }
 
-  async function applyAiModify() {
-    if (!aiPrompt.trim()) return
+  // Compile natural language → grammar (replaces textarea content)
+  async function compileNlToGrammar() {
+    if (!grammarText.trim()) return
     setAiLoading(true); setAiError(null)
     try {
-      const r = await api(`/api/causal-lab/template/${state.templateId ?? 0}/ai-modify`, {
+      const r = await api(`/api/causal-lab/template/${state.templateId ?? 0}/ai-to-grammar`, {
         method: 'POST', headers: { 'Content-Type': 'application/json' },
-        body: JSON.stringify({ prompt: aiPrompt, current_graph: graphJson }),
+        body: JSON.stringify({ prompt: grammarText, current_graph: graphJson }),
       })
-      const gj: GraphJson = r.graph_json
-      setState(s => ({
-        ...s,
-        nodes: gj.nodes || s.nodes,
-        edges: gj.edges || s.edges,
-        coefficients: gj.coefficients || s.coefficients,
-        inputMapping: gj.input_mapping || s.inputMapping,
-        instruments: gj.instruments || s.instruments,
-      }))
-      setMsg({ ok: true, text: 'Graphe modifié par l\'IA — vérifiez puis sauvegardez.' })
+      setGrammarText(r.grammar)
+      setGrammarErrors([])
+      setGrammarApplied(0)
     } catch (e) {
       setAiError(String(e))
     } finally {
@@ -990,6 +1153,17 @@ function TabEditor({ initialId }: { initialId?: number | null }) {
     }
   }
 
+  // Apply grammar patch directly to editor state (no AI)
+  function applyGrammar() {
+    const { ops, errors: parseErrors } = parseGrammar(grammarText)
+    if (parseErrors.length && ops.length === 0) { setGrammarErrors(parseErrors); return }
+    const { state: newState, errors: applyErrors } = applyGrammarOps(state, ops)
+    setGrammarErrors([...parseErrors, ...applyErrors])
+    setState(newState)
+    setGrammarApplied(ops.length - applyErrors.length)
+    if (ops.length > 0) setMsg({ ok: true, text: `${ops.length - applyErrors.length}/${ops.length} opérations appliquées.` })
+  }
+
   function resetNew() { setState(BLANK); setSelNode(null) }
 
   const graphJson: GraphJson = {
@@ -1645,40 +1819,80 @@ function TabEditor({ initialId }: { initialId?: number | null }) {
         </div>
         <GraphLegend />
 
-        {/* AI Modification prompt */}
-        <div className="bg-dark-700 rounded-lg p-4 border border-violet-900/40">
-          <h4 className="text-slate-300 text-xs font-semibold mb-3 uppercase tracking-wider flex items-center gap-2">
-            <Wand2 className="w-3.5 h-3.5 text-violet-400" /> Modifier via IA
-          </h4>
-          {!state.templateId && (
-            <p className="text-xs text-slate-500 mb-2 italic">
-              Sauvegardez d'abord le template pour activer la modification IA.
-            </p>
+        {/* Grammar patch panel */}
+        <div className="bg-dark-700 rounded-lg p-4 border border-violet-900/40 space-y-3">
+          <div className="flex items-center justify-between">
+            <h4 className="text-slate-300 text-xs font-semibold uppercase tracking-wider flex items-center gap-2">
+              <Wand2 className="w-3.5 h-3.5 text-violet-400" /> Patch Grammaire
+            </h4>
+            <button onClick={() => setShowGrammarRef(v => !v)}
+              className="text-xs text-slate-600 hover:text-slate-400 flex items-center gap-1">
+              <Info className="w-3 h-3" /> {showGrammarRef ? 'Masquer' : 'Référence'}
+            </button>
+          </div>
+
+          {showGrammarRef && (
+            <pre className="text-[10px] font-mono text-slate-500 bg-dark-900/60 rounded p-2 overflow-x-auto leading-relaxed whitespace-pre">
+              {GRAMMAR_REFERENCE}
+            </pre>
           )}
+
           <textarea
-            value={aiPrompt}
-            onChange={e => setAiPrompt(e.target.value)}
+            value={grammarText}
+            onChange={e => { setGrammarText(e.target.value); setGrammarErrors([]); setGrammarApplied(0) }}
             disabled={aiLoading}
             placeholder={
-              "Décrivez les modifications souhaitées...\n" +
-              "Ex: Ajoute un nœud latent 'risk_aversion' entre Fed OIS et EUR/USD, avec un lien négatif et lag 2j."
+              "Écrivez la grammaire directement, ou décrivez en français puis cliquez « Compiler »\n\n" +
+              "+node id=risk_aversion label=\"Risk Aversion\" type=latent x=450 y=300\n" +
+              "+edge from=us_10y to=risk_aversion sign=- lag=2 decay=10\n" +
+              "~edge from=ois_pricing to=us_2y lag=3\n" +
+              "-edge from=rate_diff to=eurusd_pip"
             }
-            rows={5}
-            className="w-full bg-dark-800 border border-slate-600 rounded px-3 py-2 text-xs text-slate-200 placeholder:text-slate-600 resize-none focus:border-violet-600 focus:outline-none"
+            rows={7}
+            className="w-full bg-dark-900/70 border border-slate-700 rounded px-3 py-2 text-xs font-mono text-slate-200 placeholder:text-slate-600 resize-none focus:border-violet-600 focus:outline-none"
           />
-          <div className="flex items-center gap-3 mt-2">
+
+          <div className="flex items-center gap-2 flex-wrap">
+            {/* Compile NL → grammar */}
             <button
-              onClick={applyAiModify}
-              disabled={aiLoading || !aiPrompt.trim() || !state.templateId}
-              className="flex items-center gap-2 px-4 py-2 bg-violet-700 hover:bg-violet-600 disabled:opacity-40 rounded text-xs font-medium text-white transition-all">
+              onClick={compileNlToGrammar}
+              disabled={aiLoading || !grammarText.trim() || !state.templateId}
+              title={!state.templateId ? "Sauvegardez d'abord le template" : undefined}
+              className="flex items-center gap-1.5 px-3 py-1.5 bg-slate-700 hover:bg-slate-600 disabled:opacity-40 rounded text-xs text-slate-300 border border-slate-600 transition-all">
               {aiLoading
-                ? <><RefreshCw className="w-3.5 h-3.5 animate-spin" /> Génération…</>
-                : <><Wand2 className="w-3.5 h-3.5" /> Appliquer</>}
+                ? <><RefreshCw className="w-3 h-3 animate-spin" /> Compilation…</>
+                : <><Brain className="w-3 h-3 text-violet-400" /> NL → Grammaire</>}
             </button>
-            {aiLoading && <span className="text-xs text-violet-400 animate-pulse">GPT-4o réécrit le graphe…</span>}
+
+            {/* Apply grammar locally */}
+            <button
+              onClick={applyGrammar}
+              disabled={!grammarText.trim() || aiLoading}
+              className="flex items-center gap-1.5 px-3 py-1.5 bg-violet-700 hover:bg-violet-600 disabled:opacity-40 rounded text-xs font-medium text-white transition-all">
+              <Zap className="w-3 h-3" /> Appliquer
+            </button>
+
+            {/* Live parse count */}
+            {grammarText.trim() && (() => {
+              const { ops } = parseGrammar(grammarText)
+              return ops.length > 0 ? (
+                <span className="text-xs text-slate-500">{ops.length} opération{ops.length > 1 ? 's' : ''} détectée{ops.length > 1 ? 's' : ''}</span>
+              ) : null
+            })()}
+
+            {grammarApplied > 0 && (
+              <span className="text-xs text-emerald-500">✓ {grammarApplied} appliquée{grammarApplied > 1 ? 's' : ''}</span>
+            )}
           </div>
+
+          {/* Errors */}
+          {grammarErrors.length > 0 && (
+            <div className="p-2 bg-red-900/20 border border-red-700/40 rounded text-xs text-red-300 space-y-0.5">
+              {grammarErrors.map((e, i) => <div key={i}>⚠ {e}</div>)}
+            </div>
+          )}
           {aiError && (
-            <div className="mt-2 p-2 bg-red-900/20 border border-red-700/40 rounded text-xs text-red-300">
+            <div className="p-2 bg-red-900/20 border border-red-700/40 rounded text-xs text-red-300">
               {aiError}
             </div>
           )}