fix(provider): harden text tool-call extraction parsing

pkg/providers/claude_cli_provider.go

@@ -164,10 +164,32 @@ func (p *ClaudeCliProvider) stripToolCallsJSON(text string) string {
 // findMatchingBrace finds the index after the closing brace matching the opening brace at pos.
 func findMatchingBrace(text string, pos int) int {
 	depth := 0
+	inString := false
+	escaped := false
+
 	for i := pos; i < len(text); i++ {
-		if text[i] == '{' {
+		ch := text[i]
+		if inString {
+			if escaped {
+				escaped = false
+				continue
+			}
+			if ch == '\\' {
+				escaped = true
+				continue
+			}
+			if ch == '"' {
+				inString = false
+			}
+			continue
+		}
+
+		switch ch {
+		case '"':
+			inString = true
+		case '{':
 			depth++
-		} else if text[i] == '}' {
+		case '}':
 			depth--
 			if depth == 0 {
 				return i + 1

pkg/providers/tool_call_extract.go

@@ -5,41 +5,28 @@ import (
 	"strings"
 )
 
+type textToolCall struct {
+	ID       string `json:"id"`
+	Type     string `json:"type"`
+	Function struct {
+		Name      string `json:"name"`
+		Arguments string `json:"arguments"`
+	} `json:"function"`
+}
+
 // extractToolCallsFromText parses tool call JSON from response text.
 // Both ClaudeCliProvider and CodexCliProvider use this to extract
 // tool calls that the model outputs in its response text.
 func extractToolCallsFromText(text string) []ToolCall {
-	start := strings.Index(text, `{"tool_calls"`)
-	if start == -1 {
-		return nil
-	}
-
-	end := findMatchingBrace(text, start)
-	if end == start {
-		return nil
-	}
-
-	jsonStr := text[start:end]
-
-	var wrapper struct {
-		ToolCalls []struct {
-			ID       string `json:"id"`
-			Type     string `json:"type"`
-			Function struct {
-				Name      string `json:"name"`
-				Arguments string `json:"arguments"`
-			} `json:"function"`
-		} `json:"tool_calls"`
-	}
-
-	if err := json.Unmarshal([]byte(jsonStr), &wrapper); err != nil {
+	start, end, rawToolCalls, ok := locateToolCallObject(text)
+	if !ok || end <= start {
 		return nil
 	}
 
 	var result []ToolCall
-	for _, tc := range wrapper.ToolCalls {
+	for _, tc := range rawToolCalls {
 		var args map[string]any
-		json.Unmarshal([]byte(tc.Function.Arguments), &args)
+		_ = json.Unmarshal([]byte(tc.Function.Arguments), &args)
 
 		result = append(result, ToolCall{
 			ID:        tc.ID,
@@ -58,15 +45,51 @@ func extractToolCallsFromText(text string) []ToolCall {
 
 // stripToolCallsFromText removes tool call JSON from response text.
 func stripToolCallsFromText(text string) string {
-	start := strings.Index(text, `{"tool_calls"`)
-	if start == -1 {
-		return text
-	}
-
-	end := findMatchingBrace(text, start)
-	if end == start {
+	start, end, _, ok := locateToolCallObject(text)
+	if !ok || end <= start {
 		return text
 	}
 
 	return strings.TrimSpace(text[:start] + text[end:])
 }
+
+func locateToolCallObject(text string) (start int, end int, toolCalls []textToolCall, ok bool) {
+	for i := 0; i < len(text); i++ {
+		if text[i] != '{' {
+			continue
+		}
+
+		candidateEnd := findMatchingBrace(text, i)
+		if candidateEnd <= i {
+			continue
+		}
+
+		candidateToolCalls, matched := parseToolCallsObject(text[i:candidateEnd])
+		if !matched {
+			continue
+		}
+
+		return i, candidateEnd, candidateToolCalls, true
+	}
+
+	return 0, 0, nil, false
+}
+
+func parseToolCallsObject(jsonStr string) ([]textToolCall, bool) {
+	var obj map[string]json.RawMessage
+	if err := json.Unmarshal([]byte(jsonStr), &obj); err != nil {
+		return nil, false
+	}
+
+	rawToolCalls, exists := obj["tool_calls"]
+	if !exists {
+		return nil, false
+	}
+
+	var toolCalls []textToolCall
+	if err := json.Unmarshal(rawToolCalls, &toolCalls); err != nil {
+		return nil, false
+	}
+
+	return toolCalls, true
+}

pkg/providers/tool_call_extract_test.go

@@ -0,0 +1,105 @@
+package providers
+
+import "testing"
+
+func TestExtractToolCallsFromText_IndentedObjectWithExtraText(t *testing.T) {
+	text := `Planning tool execution...
+{
+  "message": "calling tools",
+  "tool_calls": [
+    {
+      "id": "call_1",
+      "type": "function",
+      "function": {
+        "name": "read_file",
+        "arguments": "{\"path\":\"/tmp/test.txt\"}"
+      }
+    }
+  ],
+  "status": "ok"
+}
+Done.`
+
+	got := extractToolCallsFromText(text)
+	if len(got) != 1 {
+		t.Fatalf("extractToolCallsFromText() len = %d, want 1", len(got))
+	}
+	if got[0].Name != "read_file" {
+		t.Fatalf("tool name = %q, want %q", got[0].Name, "read_file")
+	}
+	if got[0].Arguments["path"] != "/tmp/test.txt" {
+		t.Fatalf("tool args[path] = %v, want /tmp/test.txt", got[0].Arguments["path"])
+	}
+}
+
+func TestExtractToolCallsFromText_ToolCallsNotFirstField(t *testing.T) {
+	text := `{"kind":"assistant_result","metadata":{"provider":"x"},"tool_calls":[{"id":"call_7","type":"function","function":{"name":"write_file","arguments":"{\"path\":\"a.txt\",\"content\":\"hello\"}"}}]}`
+
+	got := extractToolCallsFromText(text)
+	if len(got) != 1 {
+		t.Fatalf("extractToolCallsFromText() len = %d, want 1", len(got))
+	}
+	if got[0].ID != "call_7" {
+		t.Fatalf("tool id = %q, want %q", got[0].ID, "call_7")
+	}
+	if got[0].Name != "write_file" {
+		t.Fatalf("tool name = %q, want %q", got[0].Name, "write_file")
+	}
+}
+
+func TestExtractToolCallsFromText_SkipsInvalidCandidateAndFindsValidObject(t *testing.T) {
+	text := `prefix {"tool_calls":invalid} middle {"note":"valid-json-without-tools"} tail {
+  "note": "valid-json-with-tools",
+  "tool_calls": [
+    {
+      "id": "call_2",
+      "type": "function",
+      "function": {
+        "name": "get_weather",
+        "arguments": "{\"city\":\"Tokyo\"}"
+      }
+    }
+  ]
+}`
+
+	got := extractToolCallsFromText(text)
+	if len(got) != 1 {
+		t.Fatalf("extractToolCallsFromText() len = %d, want 1", len(got))
+	}
+	if got[0].Name != "get_weather" {
+		t.Fatalf("tool name = %q, want %q", got[0].Name, "get_weather")
+	}
+}
+
+func TestStripToolCallsFromText_DoesNotStripInvalidToolCallsObject(t *testing.T) {
+	text := `before {"tool_calls":"not-an-array","other":1} after`
+
+	got := stripToolCallsFromText(text)
+	if got != text {
+		t.Fatalf("stripToolCallsFromText() = %q, want unchanged", got)
+	}
+}
+
+func TestStripToolCallsFromText_StripsValidIndentedObject(t *testing.T) {
+	text := `before
+{
+  "message": "tool call follows",
+  "tool_calls": [
+    {
+      "id": "call_3",
+      "type": "function",
+      "function": {
+        "name": "list_files",
+        "arguments": "{}"
+      }
+    }
+  ]
+}
+after`
+
+	got := stripToolCallsFromText(text)
+	want := "before\n\nafter"
+	if got != want {
+		t.Fatalf("stripToolCallsFromText() = %q, want %q", got, want)
+	}
+}