diff --git a/nodes/src/nodes/prompt_template/IGlobal.py b/nodes/src/nodes/prompt_template/IGlobal.py
new file mode 100644
index 000000000..0ac0a2501
--- /dev/null
+++ b/nodes/src/nodes/prompt_template/IGlobal.py
@@ -0,0 +1,44 @@
+# =============================================================================
+# MIT License
+# Copyright (c) 2026 Aparavi Software AG
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+# =============================================================================
+
+from rocketlib import IGlobalBase, OPEN_MODE
+from ai.common.config import Config
+
+
+class IGlobal(IGlobalBase):
+    config = None
+
+    def beginGlobal(self):
+        if self.IEndpoint.endpoint.openMode == OPEN_MODE.CONFIG:
+            pass
+        else:
+            import os
+            from depends import depends  # type: ignore
+
+            requirements = os.path.dirname(os.path.realpath(__file__)) + '/requirements.txt'
+            depends(requirements)
+
+            self.config = Config.getNodeConfig(self.glb.logicalType, self.glb.connConfig)
+
+    def endGlobal(self):
+        self.config = None
diff --git a/nodes/src/nodes/prompt_template/IInstance.py b/nodes/src/nodes/prompt_template/IInstance.py
new file mode 100644
index 000000000..05ba01276
--- /dev/null
+++ b/nodes/src/nodes/prompt_template/IInstance.py
@@ -0,0 +1,85 @@
+# =============================================================================
+# MIT License
+# Copyright (c) 2026 Aparavi Software AG
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+# =============================================================================
+
+from rocketlib import IInstanceBase
+from .IGlobal import IGlobal
+from .template_engine import render
+from ai.common.schema import Question
+from rocketlib import debug, Entry
+
+
+class IInstance(IInstanceBase):
+    IGlobal: IGlobal
+
+    def __init__(self):
+        """Initialize the prompt template node instance state."""
+        super().__init__()
+        self.collected_text: list[str] = []
+        self.question = Question()
+
+    def open(self, entry: Entry):
+        pass
+
+    def _get_template_context(self) -> dict:
+        """Build the context dictionary for template rendering."""
+        config = self.IGlobal.config
+        if config is None:
+            config = {}
+        raw_variables = config.get('variables', {})
+        variables = dict(raw_variables) if isinstance(raw_variables, dict) else {}
+
+        # Add collected text as 'input' if available
+        if self.collected_text:
+            variables.setdefault('input', '\n'.join(self.collected_text))
+
+        return variables
+
+    def writeQuestions(self, question: Question):
+        for q in question.questions:
+            self.question.addQuestion(q.text)
+
+    def writeText(self, text: str):
+        self.collected_text.append(text)
+
+    def closing(self):
+        try:
+            config = self.IGlobal.config or {}
+            template = config.get('template', '{{input}}')
+            context = self._get_template_context()
+
+            # Render questions with full context now that all text has arrived
+            if self.question.questions:
+                rendered_question = Question()
+                for q in self.question.questions:
+                    context['question'] = q.text
+                    rendered = render(template, context)
+                    rendered_question.addQuestion(rendered)
+                self.instance.writeQuestions(rendered_question)
+            # If we only have text input, render and output as text
+            elif self.collected_text:
+                rendered = render(template, context)
+                self.instance.writeText(rendered)
+
+        except Exception as e:
+            debug(f'Error in prompt_template node: {e}')
+            raise
diff --git a/nodes/src/nodes/prompt_template/__init__.py b/nodes/src/nodes/prompt_template/__init__.py
new file mode 100644
index 000000000..1fff03125
--- /dev/null
+++ b/nodes/src/nodes/prompt_template/__init__.py
@@ -0,0 +1,27 @@
+# =============================================================================
+# MIT License
+# Copyright (c) 2026 Aparavi Software AG
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+# =============================================================================
+
+from .IGlobal import IGlobal
+from .IInstance import IInstance
+
+__all__ = ['IGlobal', 'IInstance']
diff --git a/nodes/src/nodes/prompt_template/requirements.txt b/nodes/src/nodes/prompt_template/requirements.txt
new file mode 100644
index 000000000..e709a9ba1
--- /dev/null
+++ b/nodes/src/nodes/prompt_template/requirements.txt
@@ -0,0 +1 @@
+# No external dependencies — stdlib only
diff --git a/nodes/src/nodes/prompt_template/services.json b/nodes/src/nodes/prompt_template/services.json
new file mode 100644
index 000000000..6c9df0137
--- /dev/null
+++ b/nodes/src/nodes/prompt_template/services.json
@@ -0,0 +1,195 @@
+{
+	//
+	// Required:
+	//		The displayable name of this node
+	//
+	"title": "Prompt Template",
+	//
+	// Required:
+	//		The protocol is the endpoint protocol
+	//
+	"protocol": "prompt-template://",
+	//
+	// Required:
+	//		Class type of the node - what it does
+	//
+	"classType": [
+		"text"
+	],
+	//
+	// Required:
+	//		Capabilities are flags that change the behavior of the underlying
+	//		engine
+	//
+	"capabilities": ["experimental"],
+	//
+	// Optional:
+	//		Register is either filter, endpoint or ignored if not specified. If the
+	//		type is specified, a factory is registered of that given type
+	//
+	"register": "filter",
+	//
+	// Optional:
+	//		The node is the actual pyhsical node to instantiate - if
+	//		not specified, the protocol will be used
+	//
+	"node": "python",
+	//
+	// Optional:
+	//		The path is the executable/script code - it is node dependent
+	// 		and is optional for most node
+	//
+	"path": "nodes.prompt_template",
+	//
+	// Required:
+	//		The prefix map when added/removed when convertting URLs <=> paths
+	//
+	"prefix": "prompt_template",
+	//
+	// Optional:
+	//		Description to of this driver
+	//
+	"description": [
+		"A transformation component that renders prompt templates with dynamic ",
+		"variable substitution. Supports {{variable}} placeholders resolved from ",
+		"pipeline context, built-in helpers ({{now}}, {{uuid}}, {{random}}), ",
+		"conditional sections ({% if var %}...{% endif %}), loop support ",
+		"({% for item in list %}...{% endfor %}), and escape sequences for ",
+		"literal braces. Implemented with stdlib only — no Jinja2 dependency."
+	],
+	//
+	// Optional:
+	//	  The icon is the icon to display in the UI for this node
+	//
+	"icon": "prompt.svg",
+	//
+	// Optional:
+	//	 The tile is the displayable name of this node
+	//
+	"tile": [],
+	//
+	//	Optional:
+	//		As a pipe component, define what this pipe component takes
+	//		and what it produces
+	//
+	"lanes": {
+		"text": ["text"],
+		"questions": ["questions"]
+	},
+	"input": [
+		{
+			"lane": "text",
+			"description": "Text input - used as context variables for template rendering",
+			"output": [
+				{
+					"lane": "text",
+					"description": "Rendered template output as text"
+				}
+			]
+		},
+		{
+			"lane": "questions",
+			"description": "Questions input - question text is rendered through the template",
+			"output": [
+				{
+					"lane": "questions",
+					"description": "Questions with template-rendered text"
+				}
+			]
+		}
+	],
+	//
+	//	Optional:
+	//		Profile section are configuration options used by the driver
+	//		itself
+	//
+	"preconfig": {
+		"default": "default",
+		"profiles": {
+			"default": {
+				"template": "{{input}}",
+				"variables": {}
+			}
+		}
+	},
+	//
+	//	Test configuration for automated node testing
+	//
+	"test": {
+		"profiles": ["default"],
+		"cases": [
+			{
+				"questions": {
+					"questions": [{"text": "Hello world"}]
+				},
+				"expect": {
+					"questions": {
+						"notEmpty": true
+					}
+				}
+			},
+			{
+				"config": {
+					"template": "Summarize the following: {{input}}",
+					"variables": {"input": "The quick brown fox jumps over the lazy dog."}
+				},
+				"questions": {
+					"questions": [{"text": "test prompt"}]
+				},
+				"expect": {
+					"questions": {
+						"notEmpty": true,
+						"contains": "Summarize the following:"
+					}
+				}
+			},
+			{
+				"config": {
+					"template": "Q={{question}} | I={{input}}",
+					"variables": {"input": "ctx"}
+				},
+				"questions": {
+					"questions": [{"text": "what is this?"}]
+				},
+				"expect": {
+					"questions": {
+						"contains": "Q=what is this?"
+					}
+				}
+			}
+		]
+	},
+	//
+	// Optional:
+	//		Local fields defintions - these define fields only for the
+	//		current service. You may specify them here, or directly
+	//		in the shape
+	//
+	"fields": {
+		"template": {
+			"type": "string",
+			"title": "Template",
+			"description": "Prompt template with {{variable}} placeholders, conditionals ({% if %}), and loops ({% for %})"
+		},
+		"variables": {
+			"type": "object",
+			"title": "Variables",
+			"description": "Key-value pairs of variables to substitute into the template"
+		}
+	},
+	//
+	// Required:
+	//		Defines the fields (shape) of the service. Either source or target
+	//		map be specified, or both, but at least one is required
+	//
+	"shape": [
+		{
+			"section": "Pipe",
+			"title": "Template",
+			"properties": [
+				"template",
+				"variables"
+			]
+		}
+	]
+}
diff --git a/nodes/src/nodes/prompt_template/template_engine.py b/nodes/src/nodes/prompt_template/template_engine.py
new file mode 100644
index 000000000..b99ad58fc
--- /dev/null
+++ b/nodes/src/nodes/prompt_template/template_engine.py
@@ -0,0 +1,311 @@
+# =============================================================================
+# MIT License
+# Copyright (c) 2026 Aparavi Software AG
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+# =============================================================================
+
+"""
+Lightweight template engine with Jinja2-style syntax, implemented using only
+the Python standard library.
+
+Supported features:
+  - Variable substitution:  {{variable}}
+  - Built-in helpers:       {{now}}, {{uuid}}, {{random}}
+  - Conditionals:           {% if var %}...{% elif var2 %}...{% else %}...{% endif %}
+  - Loops:                  {% for item in list %}...{% endfor %}
+  - Escape sequences:       \\{{ and \\}} for literal braces
+"""
+
+import re
+import uuid as _uuid
+from datetime import datetime, timezone
+from random import random as _random
+from typing import Any
+
+
+# Sentinel used to distinguish "key missing" from "key is None"
+_MISSING = object()
+
+# ---------------------------------------------------------------------------
+# Regex patterns
+# ---------------------------------------------------------------------------
+_ESCAPE_OPEN = r'\\\{\{'
+_ESCAPE_CLOSE = r'\\\}\}'
+_PLACEHOLDER_OPEN = '\x00LBRACE\x00'
+_PLACEHOLDER_CLOSE = '\x00RBRACE\x00'
+
+
+# ---------------------------------------------------------------------------
+# Built-in helpers
+# ---------------------------------------------------------------------------
+_BUILTINS = {
+    'now': lambda: datetime.now(timezone.utc).isoformat(),
+    'uuid': lambda: str(_uuid.uuid4()),
+    'random': lambda: str(_random()),
+}
+
+
+# ---------------------------------------------------------------------------
+# Context value resolution
+# ---------------------------------------------------------------------------
+def _resolve(name: str, context: dict) -> Any:
+    """Resolve a dotted name against *context*, falling back to built-ins.
+
+    Resolution order: context takes priority over built-in helpers.
+    """
+    name = name.strip()
+
+    # 1. Try context first — user-supplied values always win
+    parts = name.split('.')
+    value = context
+    for part in parts:
+        if isinstance(value, dict):
+            value = value.get(part, _MISSING)
+        else:
+            value = getattr(value, part, _MISSING)
+        if value is _MISSING:
+            break
+
+    if value is not _MISSING:
+        return value
+
+    # 2. Fall back to built-in helpers only when context lookup failed
+    if name in _BUILTINS:
+        return _BUILTINS[name]()
+
+    return ''
+
+
+# ---------------------------------------------------------------------------
+# Block-level processing (if / for)
+# ---------------------------------------------------------------------------
+
+
+def _find_matching_end(tokens: list[tuple[str, str]], start: int, open_tag: str, close_tag: str) -> int:
+    """Return the index of the matching close_tag, handling nesting."""
+    depth = 1
+    i = start
+    while i < len(tokens):
+        kind, text = tokens[i]
+        if kind == 'block':
+            tag = text.split()[0] if text.strip() else ''
+            if tag == open_tag:
+                depth += 1
+            elif tag == close_tag:
+                depth -= 1
+                if depth == 0:
+                    return i
+        i += 1
+    return -1
+
+
+def _tokenize(template: str) -> list[tuple[str, str]]:
+    """Split template into a list of (kind, content) tokens.
+
+    Kinds: "text", "var", "block".
+    """
+    tokens: list[tuple[str, str]] = []
+    pos = 0
+    combined = re.compile(r'(\{\{.+?\}\}|\{%[-\s]*.*?[-\s]*%\})', re.DOTALL)
+    for m in combined.finditer(template):
+        if m.start() > pos:
+            tokens.append(('text', template[pos : m.start()]))
+        raw = m.group(0)
+        if raw.startswith('{{'):
+            tokens.append(('var', raw[2:-2]))
+        else:
+            tokens.append(('block', raw[2:-2].strip()))
+        pos = m.end()
+    if pos < len(template):
+        tokens.append(('text', template[pos:]))
+    return tokens
+
+
+def _eval_tokens(tokens: list[tuple[str, str]], context: dict) -> str:
+    """Walk a token list and recursively evaluate blocks."""
+    parts: list[str] = []
+    i = 0
+    while i < len(tokens):
+        kind, content = tokens[i]
+
+        if kind == 'text':
+            parts.append(content)
+            i += 1
+
+        elif kind == 'var':
+            parts.append(str(_resolve(content, context)))
+            i += 1
+
+        elif kind == 'block':
+            tag_parts = content.split(None, 1)
+            tag = tag_parts[0] if tag_parts else ''
+
+            if tag == 'if':
+                i = _handle_if(tokens, i, context, parts)
+            elif tag == 'for':
+                i = _handle_for(tokens, i, context, parts)
+            else:
+                parts.append('{%' + content + '%}')
+                i += 1
+        else:
+            i += 1
+
+    return ''.join(parts)
+
+
+def _at_top_level(tokens: list[tuple[str, str]], start: int, pos: int) -> bool:
+    """Check if *pos* is at the top nesting level between *start* and *pos*."""
+    depth_if = 0
+    depth_for = 0
+    for i in range(start, pos):
+        kind, text = tokens[i]
+        if kind == 'block':
+            tag = text.split()[0] if text.strip() else ''
+            if tag == 'if':
+                depth_if += 1
+            elif tag == 'endif':
+                depth_if -= 1
+            elif tag == 'for':
+                depth_for += 1
+            elif tag == 'endfor':
+                depth_for -= 1
+    return depth_if == 0 and depth_for == 0
+
+
+def _handle_if(
+    tokens: list[tuple[str, str]],
+    start: int,
+    context: dict,
+    parts: list[str],
+) -> int:
+    """Process an {% if %}...{% elif %}...{% else %}...{% endif %} block."""
+    end = _find_matching_end(tokens, start + 1, 'if', 'endif')
+    if end == -1:
+        parts.append('{%' + tokens[start][1] + '%}')
+        return start + 1
+
+    branches: list[tuple[str | None, list[tuple[str, str]]]] = []
+    tag_content = tokens[start][1]
+    cond_text = tag_content.split(None, 1)[1] if len(tag_content.split(None, 1)) > 1 else ''
+    body_tokens: list[tuple[str, str]] = []
+    i = start + 1
+    while i < end:
+        kind, text = tokens[i]
+        if kind == 'block':
+            tag = text.split()[0] if text.strip() else ''
+            if tag in ('elif', 'else') and _at_top_level(tokens, start + 1, i):
+                branches.append((cond_text, body_tokens))
+                body_tokens = []
+                if tag == 'elif':
+                    cond_text = text.split(None, 1)[1] if len(text.split(None, 1)) > 1 else ''
+                else:
+                    cond_text = None  # else branch
+                i += 1
+                continue
+        body_tokens.append(tokens[i])
+        i += 1
+    branches.append((cond_text, body_tokens))
+
+    for cond, body in branches:
+        if cond is None or _truthy(_resolve(cond, context)):
+            parts.append(_eval_tokens(body, context))
+            break
+
+    return end + 1
+
+
+def _handle_for(
+    tokens: list[tuple[str, str]],
+    start: int,
+    context: dict,
+    parts: list[str],
+) -> int:
+    """Process a {% for item in list %}...{% endfor %} block."""
+    end = _find_matching_end(tokens, start + 1, 'for', 'endfor')
+    if end == -1:
+        parts.append('{%' + tokens[start][1] + '%}')
+        return start + 1
+
+    content = tokens[start][1]
+    m = re.match(r'for\s+(\w+)\s+in\s+(.+)', content)
+    if not m:
+        parts.append('{%' + content + '%}')
+        return end + 1
+
+    loop_var = m.group(1)
+    iterable_name = m.group(2).strip()
+    iterable = _resolve(iterable_name, context)
+
+    if not hasattr(iterable, '__iter__') or isinstance(iterable, str):
+        return end + 1
+
+    body_tokens = tokens[start + 1 : end]
+    for item in iterable:
+        child_context = {**context, loop_var: item}
+        parts.append(_eval_tokens(body_tokens, child_context))
+
+    return end + 1
+
+
+def _truthy(value) -> bool:
+    """Determine whether a template value is truthy."""
+    if value is _MISSING or value is None:
+        return False
+    if isinstance(value, str):
+        return value != ''
+    return bool(value)
+
+
+# ---------------------------------------------------------------------------
+# Public API
+# ---------------------------------------------------------------------------
+
+
+def render(template: str, context: dict | None = None) -> str:
+    """Render *template* with the given *context* dictionary.
+
+    Parameters
+    ----------
+    template:
+        The template string containing ``{{var}}``, ``{% if %}``, ``{% for %}``
+        constructs.
+    context:
+        A dictionary of variables available for substitution.
+
+    Returns
+    -------
+    The rendered string.
+    """
+    if context is None:
+        context = {}
+
+    # 1. Protect escaped braces
+    text = re.sub(_ESCAPE_OPEN, _PLACEHOLDER_OPEN, template)
+    text = re.sub(_ESCAPE_CLOSE, _PLACEHOLDER_CLOSE, text)
+
+    # 2. Tokenize and evaluate
+    tokens = _tokenize(text)
+    result = _eval_tokens(tokens, context)
+
+    # 3. Restore escaped braces
+    result = result.replace(_PLACEHOLDER_OPEN, '{{')
+    result = result.replace(_PLACEHOLDER_CLOSE, '}}')
+
+    return result
diff --git a/nodes/test/prompt_template/test_engine.py b/nodes/test/prompt_template/test_engine.py
new file mode 100644
index 000000000..b1b1f3064
--- /dev/null
+++ b/nodes/test/prompt_template/test_engine.py
@@ -0,0 +1,387 @@
+# =============================================================================
+# MIT License
+# Copyright (c) 2026 Aparavi Software AG
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+# =============================================================================
+
+"""
+Unit tests for the custom prompt_template engine.
+
+These tests exercise ``nodes/src/nodes/prompt_template/template_engine.py`` in
+isolation — no server, no dependencies beyond the Python standard library and
+pytest. The engine is loaded directly via ``importlib`` so that importing the
+surrounding ``nodes`` package (which pulls in ``depends``) is avoided.
+
+Coverage targets:
+    - variable substitution (flat + dotted paths)
+    - missing variables / graceful fallback
+    - built-in helpers (``now``, ``uuid``, ``random``)
+    - context overriding built-ins (regression guard)
+    - conditionals (``if`` / ``elif`` / ``else`` / nested)
+    - empty and malformed ``{% if %}`` conditions
+    - loops (flat + nested)
+    - unclosed / malformed block tags
+    - escape sequences for literal braces
+    - large inputs / deeply nested blocks (ReDoS + recursion safety)
+    - HTML pass-through (no implicit escaping)
+"""
+
+import importlib.util
+import sys
+import uuid as _uuid
+from pathlib import Path
+
+
+# ---------------------------------------------------------------------------
+# Load template_engine.py directly without importing the ``nodes`` package.
+#
+# ``nodes/__init__.py`` pulls in the ``depends`` module which is only available
+# inside the built server environment. Loading the engine file directly keeps
+# these tests pure and runnable anywhere Python is available.
+# ---------------------------------------------------------------------------
+_ENGINE_PATH = Path(__file__).resolve().parent.parent / 'src' / 'nodes' / 'prompt_template' / 'template_engine.py'
+
+_spec = importlib.util.spec_from_file_location('prompt_template_engine', _ENGINE_PATH)
+assert _spec is not None and _spec.loader is not None, 'failed to locate template_engine.py'
+template_engine = importlib.util.module_from_spec(_spec)
+sys.modules['prompt_template_engine'] = template_engine
+_spec.loader.exec_module(template_engine)
+
+render = template_engine.render
+
+
+# ===========================================================================
+# 1. Simple variable substitution
+# ===========================================================================
+class TestVariableSubstitution:
+    def test_flat_variable(self):
+        assert render('Hello {{name}}', {'name': 'world'}) == 'Hello world'
+
+    def test_multiple_variables(self):
+        result = render('{{greeting}}, {{name}}!', {'greeting': 'Hi', 'name': 'Ada'})
+        assert result == 'Hi, Ada!'
+
+    def test_whitespace_inside_braces_is_stripped(self):
+        assert render('Hello {{ name }}', {'name': 'world'}) == 'Hello world'
+
+    def test_dotted_path(self):
+        ctx = {'user': {'email': 'ada@example.com'}}
+        assert render('{{user.email}}', ctx) == 'ada@example.com'
+
+    def test_deep_dotted_path(self):
+        ctx = {'a': {'b': {'c': {'d': 'leaf'}}}}
+        assert render('{{a.b.c.d}}', ctx) == 'leaf'
+
+    def test_dotted_path_with_attribute_object(self):
+        class Obj:
+            pass
+
+        o = Obj()
+        o.name = 'attribute-value'
+        assert render('{{obj.name}}', {'obj': o}) == 'attribute-value'
+
+    def test_non_string_value_is_stringified(self):
+        assert render('count={{n}}', {'n': 42}) == 'count=42'
+
+    def test_empty_template(self):
+        assert render('', {'name': 'world'}) == ''
+
+    def test_none_context(self):
+        # Should not crash when context is None.
+        assert render('hello', None) == 'hello'
+
+    def test_template_without_placeholders_passthrough(self):
+        assert render('no placeholders here', {}) == 'no placeholders here'
+
+
+# ===========================================================================
+# 2. Missing variables / graceful handling
+# ===========================================================================
+class TestMissingVariables:
+    def test_missing_flat_variable_renders_empty(self):
+        assert render('Hello {{name}}', {}) == 'Hello '
+
+    def test_missing_dotted_segment_renders_empty(self):
+        assert render('{{user.email}}', {'user': {}}) == ''
+
+    def test_missing_dotted_root_renders_empty(self):
+        assert render('{{user.email}}', {}) == ''
+
+    def test_missing_variable_does_not_raise(self):
+        # Graceful handling is a documented contract.
+        render('{{a}} {{b}} {{c.d}}', {'a': 'x'})  # must not raise
+
+
+# ===========================================================================
+# 3. Built-in helpers
+# ===========================================================================
+class TestBuiltins:
+    def test_now_is_iso_format_utc(self):
+        out = render('{{now}}', {})
+        # ISO8601 with timezone — has a 'T' separator and a '+00:00' suffix.
+        assert 'T' in out
+        assert out.endswith('+00:00')
+
+    def test_uuid_is_valid_uuid4(self):
+        out = render('{{uuid}}', {})
+        parsed = _uuid.UUID(out)
+        assert parsed.version == 4
+
+    def test_random_is_float_between_zero_and_one(self):
+        out = render('{{random}}', {})
+        value = float(out)
+        assert 0.0 <= value < 1.0
+
+    def test_builtins_work_inside_larger_template(self):
+        out = render('id={{uuid}}', {})
+        assert out.startswith('id=')
+        # The suffix must still be a valid UUID4
+        _uuid.UUID(out[len('id=') :])
+
+
+# ===========================================================================
+# 4. Context overrides built-ins (regression test for the recent fix)
+# ===========================================================================
+class TestContextOverridesBuiltins:
+    def test_context_value_wins_over_now(self):
+        assert render('{{now}}', {'now': 'FIXED'}) == 'FIXED'
+
+    def test_context_value_wins_over_uuid(self):
+        assert render('{{uuid}}', {'uuid': 'static-id'}) == 'static-id'
+
+    def test_context_value_wins_over_random(self):
+        assert render('{{random}}', {'random': '0.5'}) == '0.5'
+
+    def test_builtin_still_used_when_not_in_context(self):
+        # Sanity: when `now` is absent from context, the builtin fires.
+        out = render('{{now}}', {'other': 'value'})
+        assert 'T' in out  # builtin ran
+
+
+# ===========================================================================
+# 5. Conditionals
+# ===========================================================================
+class TestConditionals:
+    def test_if_true_branch(self):
+        assert render('{% if flag %}yes{% endif %}', {'flag': True}) == 'yes'
+
+    def test_if_false_branch(self):
+        assert render('{% if flag %}yes{% endif %}', {'flag': False}) == ''
+
+    def test_if_else_true(self):
+        tpl = '{% if flag %}yes{% else %}no{% endif %}'
+        assert render(tpl, {'flag': True}) == 'yes'
+
+    def test_if_else_false(self):
+        tpl = '{% if flag %}yes{% else %}no{% endif %}'
+        assert render(tpl, {'flag': False}) == 'no'
+
+    def test_elif_matches_second(self):
+        tpl = '{% if a %}A{% elif b %}B{% else %}C{% endif %}'
+        assert render(tpl, {'a': False, 'b': True}) == 'B'
+
+    def test_elif_falls_through_to_else(self):
+        tpl = '{% if a %}A{% elif b %}B{% else %}C{% endif %}'
+        assert render(tpl, {'a': False, 'b': False}) == 'C'
+
+    def test_empty_string_is_falsy(self):
+        assert render('{% if s %}yes{% endif %}', {'s': ''}) == ''
+
+    def test_none_is_falsy(self):
+        assert render('{% if s %}yes{% endif %}', {'s': None}) == ''
+
+    def test_missing_variable_is_falsy(self):
+        # Missing vars resolve to '' which is falsy, so the branch is skipped.
+        assert render('{% if absent %}yes{% endif %}', {}) == ''
+
+    def test_empty_if_condition_is_falsy(self):
+        # `{% if %}` has no condition name -> resolves to empty string -> falsy.
+        # Must not raise; must render the else branch.
+        tpl = '{% if %}T{% else %}F{% endif %}'
+        assert render(tpl, {}) == 'F'
+
+    def test_nested_if_inner_branch(self):
+        tpl = '{% if a %}A-{% if b %}B{% else %}NB{% endif %}{% endif %}'
+        assert render(tpl, {'a': True, 'b': True}) == 'A-B'
+        assert render(tpl, {'a': True, 'b': False}) == 'A-NB'
+        assert render(tpl, {'a': False, 'b': True}) == ''
+
+    def test_dotted_condition(self):
+        tpl = '{% if user.active %}on{% else %}off{% endif %}'
+        assert render(tpl, {'user': {'active': True}}) == 'on'
+        assert render(tpl, {'user': {'active': False}}) == 'off'
+
+
+# ===========================================================================
+# 6. Loops
+# ===========================================================================
+class TestLoops:
+    def test_basic_for_loop(self):
+        tpl = '{% for item in items %}{{item}},{% endfor %}'
+        assert render(tpl, {'items': ['a', 'b', 'c']}) == 'a,b,c,'
+
+    def test_for_loop_empty_iterable(self):
+        tpl = '[{% for item in items %}{{item}}{% endfor %}]'
+        assert render(tpl, {'items': []}) == '[]'
+
+    def test_for_loop_over_dicts_with_dotted_access(self):
+        tpl = '{% for u in users %}{{u.name}}:{% endfor %}'
+        ctx = {'users': [{'name': 'ada'}, {'name': 'bob'}]}
+        assert render(tpl, ctx) == 'ada:bob:'
+
+    def test_for_loop_with_missing_iterable_is_noop(self):
+        tpl = 'start[{% for item in items %}{{item}}{% endfor %}]end'
+        assert render(tpl, {}) == 'start[]end'
+
+    def test_for_loop_over_string_is_noop(self):
+        # _handle_for explicitly skips strings so we don't iterate characters.
+        tpl = '{% for c in s %}{{c}}{% endfor %}'
+        assert render(tpl, {'s': 'hello'}) == ''
+
+    def test_nested_for_loops(self):
+        tpl = '{% for row in rows %}{% for cell in row %}{{cell}},{% endfor %}|{% endfor %}'
+        ctx = {'rows': [[1, 2], [3, 4]]}
+        assert render(tpl, ctx) == '1,2,|3,4,|'
+
+    def test_loop_variable_shadowing(self):
+        # Loop var should be visible only inside the loop body.
+        tpl = '{% for x in items %}{{x}},{% endfor %}outer:{{x}}'
+        assert render(tpl, {'items': ['a', 'b'], 'x': 'OUT'}) == 'a,b,outer:OUT'
+
+
+# ===========================================================================
+# 7. Malformed / unclosed tags
+# ===========================================================================
+class TestMalformedTags:
+    def test_unclosed_if_emits_raw_tag(self):
+        # When there's no matching endif, the engine falls back to rendering
+        # the raw tag text and continuing — graceful rather than crashing.
+        out = render('{% if flag %}body', {'flag': True})
+        # The raw tag is preserved; the body is still processed as text.
+        assert 'if flag' in out
+        assert 'body' in out
+
+    def test_unclosed_for_emits_raw_tag(self):
+        out = render('{% for x in items %}body', {'items': [1, 2]})
+        assert 'for x in items' in out
+        assert 'body' in out
+
+    def test_malformed_for_tag_is_noop(self):
+        # `{% for foo %}` has no `in ...` clause — regex match fails, the raw
+        # tag is emitted and the body between tags is dropped. The engine
+        # must not raise.
+        out = render('before{% for foo %}X{% endfor %}after', {})
+        assert out.startswith('before')
+        assert out.endswith('after')
+        assert 'X' not in out  # body is dropped
+
+    def test_unknown_block_tag_is_passed_through(self):
+        tpl = 'x{% weird tag %}y'
+        out = render(tpl, {})
+        assert 'weird tag' in out
+        assert out.startswith('x')
+        assert out.endswith('y')
+
+
+# ===========================================================================
+# 8. Escape sequences
+# ===========================================================================
+class TestEscapes:
+    def test_escaped_open_brace(self):
+        # \{{ should render as literal {{
+        assert render(r'\{{name}}', {'name': 'ignored'}) == '{{name}}'
+
+    def test_escaped_close_brace(self):
+        # \}} should render as literal }}
+        assert render(r'{{name}}\}}', {'name': 'X'}) == 'X}}'
+
+    def test_escaped_pair_does_not_substitute(self):
+        assert render(r'\{{x\}}', {'x': 'should-not-appear'}) == '{{x}}'
+
+
+# ===========================================================================
+# 9. HTML pass-through (no implicit escaping)
+# ===========================================================================
+class TestHtmlPassthrough:
+    def test_html_substituted_unchanged(self):
+        # The engine does NOT auto-escape — confirming existing behavior so
+        # that any future change is a conscious one. Callers are responsible
+        # for sanitizing untrusted values.
+        tpl = 'Result: {{payload}}'
+        ctx = {'payload': '<script>alert(1)</script>'}
+        assert render(tpl, ctx) == 'Result: <script>alert(1)</script>'
+
+    def test_html_entity_in_template_is_literal(self):
+        assert render('&amp;', {}) == '&amp;'
+
+
+# ===========================================================================
+# 10. Safety: large / deeply-nested input (ReDoS + recursion)
+# ===========================================================================
+class TestSafety:
+    def test_large_literal_input_runs_quickly(self):
+        # ~100KB with one placeholder: verifies the tokenizer regex handles
+        # large literal runs correctly and does not catastrophically backtrack
+        # (ReDoS guard). A regex blow-up would manifest as a multi-minute hang
+        # that pytest would terminate — no wall-clock threshold is needed here,
+        # and asserting one only introduces CI flakiness on slow/busy runners.
+        template = 'x' * 50_000 + '{{v}}' + 'y' * 50_000
+        out = render(template, {'v': 'MID'})
+        assert out == ('x' * 50_000 + 'MID' + 'y' * 50_000)
+
+    def test_many_placeholders(self):
+        tpl = ''.join(f'{{{{v{i}}}}}' for i in range(500))
+        ctx = {f'v{i}': str(i) for i in range(500)}
+        out = render(tpl, ctx)
+        assert out == ''.join(str(i) for i in range(500))
+
+    def test_nested_if_blocks_do_not_blow_stack(self):
+        depth = 50
+        tpl = '{% if flag %}' * depth + 'X' + '{% endif %}' * depth
+        out = render(tpl, {'flag': True})
+        assert out == 'X'
+
+    def test_nested_for_blocks_do_not_blow_stack(self):
+        # 10 nested loops of 1 item each — exercises the recursive
+        # _eval_tokens path without exploding combinatorially.
+        depth = 10
+        header = ''.join(f'{{% for x{i} in items %}}' for i in range(depth))
+        footer = '{% endfor %}' * depth
+        tpl = header + 'Y' + footer
+        out = render(tpl, {'items': [1]})
+        assert out == 'Y'
+
+
+# ===========================================================================
+# 11. Public API surface
+# ===========================================================================
+class TestPublicAPI:
+    def test_render_returns_string(self):
+        assert isinstance(render('hello', {}), str)
+
+    def test_render_accepts_none_context(self):
+        assert render('hello {{x}}', None) == 'hello '
+
+    def test_regression_for_question_substitution(self):
+        # Mirrors the real IInstance.closing() usage where `question` is
+        # injected into the per-render context alongside collected text.
+        tpl = 'Q={{question}} | I={{input}}'
+        ctx = {'question': 'what is this?', 'input': 'ctx'}
+        assert render(tpl, ctx) == 'Q=what is this? | I=ctx'