diff --git a/.gitignore b/.gitignore
index 5c3ef7b5..ea0ebb93 100644
--- a/.gitignore
+++ b/.gitignore
@@ -270,4 +270,7 @@ docs/plans/
 # Playwright MCP
 .playwright-mcp/
 
+# Git worktrees
+.worktrees/
+
 /.luarc.json
diff --git a/pkg-py/CHANGELOG.md b/pkg-py/CHANGELOG.md
index ae25050b..c3346cfd 100644
--- a/pkg-py/CHANGELOG.md
+++ b/pkg-py/CHANGELOG.md
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Improvements
+
+* When a custom `prompt_template` is provided that doesn't contain Mustache references to `{{schema}}`, the expensive `get_schema()` call is now skipped entirely. This allows users with large databases to avoid slow startup by providing their own prompt that includes schema information inline (or omits it). (#208)
+
 ### New features
 
 * Added support for Snowflake Semantic Views. When connected to Snowflake (via SQLAlchemy or Ibis), querychat automatically discovers available Semantic Views and includes their definitions in the system prompt. This helps the LLM generate correct queries using the `SEMANTIC_VIEW()` table function with certified business metrics and dimensions. (#200)
diff --git a/pkg-py/src/querychat/_system_prompt.py b/pkg-py/src/querychat/_system_prompt.py
index 7b4f737a..5a8445e9 100644
--- a/pkg-py/src/querychat/_system_prompt.py
+++ b/pkg-py/src/querychat/_system_prompt.py
@@ -1,10 +1,13 @@
 from __future__ import annotations
 
+import re
 from pathlib import Path
 from typing import TYPE_CHECKING
 
 import chevron
 
+_SCHEMA_TAG_RE = re.compile(r"\{\{[{#^/]?\s*schema\b")
+
 if TYPE_CHECKING:
     from ._datasource import DataSource
     from ._querychat_base import TOOL_GROUPS
@@ -47,9 +50,12 @@ def __init__(
         else:
             self.extra_instructions = extra_instructions
 
-        self.schema = data_source.get_schema(
-            categorical_threshold=categorical_threshold
-        )
+        if _SCHEMA_TAG_RE.search(self.template):
+            self.schema = data_source.get_schema(
+                categorical_threshold=categorical_threshold
+            )
+        else:
+            self.schema = ""
 
         self.categorical_threshold = categorical_threshold
         self.data_source = data_source
diff --git a/pkg-py/tests/test_base.py b/pkg-py/tests/test_base.py
index ead9001e..daff6ee0 100644
--- a/pkg-py/tests/test_base.py
+++ b/pkg-py/tests/test_base.py
@@ -208,7 +208,7 @@ def test_client_with_callbacks(self, sample_df):
         reset_called = []
 
         client = qc.client(
-            update_dashboard=lambda data: update_called.append(data),
+            update_dashboard=update_called.append,
             reset_dashboard=lambda: reset_called.append(True),
         )
         assert isinstance(client, chatlas.Chat)
diff --git a/pkg-py/tests/test_system_prompt.py b/pkg-py/tests/test_system_prompt.py
index 4d691966..64b64c9b 100644
--- a/pkg-py/tests/test_system_prompt.py
+++ b/pkg-py/tests/test_system_prompt.py
@@ -257,3 +257,44 @@ def test_render_includes_db_type(self, sample_data_source, sample_prompt_templat
 
         assert "Database Type:" in rendered
         assert sample_data_source.get_db_type() in rendered
+
+
+class TestSchemaInferenceSkip:
+    """Tests that schema inference is skipped when template doesn't reference {{schema}}."""
+
+    def test_schema_skipped_when_not_in_template(self, sample_data_source):
+        """Schema should be empty string when template doesn't use {{schema}}."""
+        prompt = QueryChatSystemPrompt(
+            prompt_template="No schema here: {{db_type}}",
+            data_source=sample_data_source,
+        )
+
+        assert prompt.schema == ""
+
+    def test_schema_computed_when_in_template(self, sample_data_source):
+        """Schema should be computed when template uses {{schema}}."""
+        prompt = QueryChatSystemPrompt(
+            prompt_template="Schema: {{schema}}",
+            data_source=sample_data_source,
+        )
+
+        assert prompt.schema != ""
+        assert "test_table" in prompt.schema
+
+    def test_schema_computed_for_triple_braces(self, sample_data_source):
+        """Schema should be computed for unescaped {{{schema}}} syntax."""
+        prompt = QueryChatSystemPrompt(
+            prompt_template="Schema: {{{schema}}}",
+            data_source=sample_data_source,
+        )
+
+        assert prompt.schema != ""
+
+    def test_schema_computed_for_conditional_section(self, sample_data_source):
+        """Schema should be computed for {{#schema}} conditional sections."""
+        prompt = QueryChatSystemPrompt(
+            prompt_template="{{#schema}}Has schema{{/schema}}",
+            data_source=sample_data_source,
+        )
+
+        assert prompt.schema != ""
diff --git a/pkg-r/NEWS.md b/pkg-r/NEWS.md
index ded02d63..6620d215 100644
--- a/pkg-r/NEWS.md
+++ b/pkg-r/NEWS.md
@@ -1,5 +1,6 @@
 # querychat (development version)
 
+* When a custom `prompt_template` is provided that doesn't contain Mustache references to `{{schema}}`, the expensive `get_schema()` call is now skipped entirely. This allows users with large databases to avoid slow startup by providing their own prompt that includes schema information inline (or omits it). (#208)
 
 * Added support for Snowflake Semantic Views. When connected to Snowflake via DBI, querychat automatically discovers available Semantic Views and includes their definitions in the system prompt. This helps the LLM generate correct queries using the `SEMANTIC_VIEW()` table function with certified business metrics and dimensions. (#200)
 
diff --git a/pkg-r/R/QueryChatSystemPrompt.R b/pkg-r/R/QueryChatSystemPrompt.R
index db98e952..69435507 100644
--- a/pkg-r/R/QueryChatSystemPrompt.R
+++ b/pkg-r/R/QueryChatSystemPrompt.R
@@ -62,10 +62,14 @@ QueryChatSystemPrompt <- R6::R6Class(
         self$extra_instructions <- read_text(extra_instructions)
       }
 
-      # Store schema and other fields
-      self$schema <- data_source$get_schema(
-        categorical_threshold = categorical_threshold
-      )
+      # Only compute schema if the template references it
+      if (grepl("\\{\\{[{#^/]?\\s*schema\\b", self$template)) {
+        self$schema <- data_source$get_schema(
+          categorical_threshold = categorical_threshold
+        )
+      } else {
+        self$schema <- ""
+      }
       self$categorical_threshold <- categorical_threshold
       self$data_source <- data_source
     },
diff --git a/pkg-r/tests/testthat/test-QueryChatSystemPrompt.R b/pkg-r/tests/testthat/test-QueryChatSystemPrompt.R
index 4339f077..4d773f18 100644
--- a/pkg-r/tests/testthat/test-QueryChatSystemPrompt.R
+++ b/pkg-r/tests/testthat/test-QueryChatSystemPrompt.R
@@ -455,3 +455,60 @@ describe("QueryChatSystemPrompt with full prompt.md template", {
     expect_match(prompt_high, "Categorical values:")
   })
 })
+
+describe("Schema inference skip", {
+  skip_if_no_dataframe_engine()
+
+  it("skips schema when template doesn't reference {{schema}}", {
+    df <- new_test_df()
+    ds <- DataFrameSource$new(df, "test_table")
+    withr::defer(ds$cleanup())
+
+    sp <- QueryChatSystemPrompt$new(
+      prompt_template = "No schema here: {{db_type}}",
+      data_source = ds
+    )
+
+    expect_equal(sp$schema, "")
+  })
+
+  it("computes schema when template uses {{schema}}", {
+    df <- new_test_df()
+    ds <- DataFrameSource$new(df, "test_table")
+    withr::defer(ds$cleanup())
+
+    sp <- QueryChatSystemPrompt$new(
+      prompt_template = "Schema: {{schema}}",
+      data_source = ds
+    )
+
+    expect_true(nchar(sp$schema) > 0)
+    expect_match(sp$schema, "test_table")
+  })
+
+  it("computes schema for {{{schema}}} triple braces", {
+    df <- new_test_df()
+    ds <- DataFrameSource$new(df, "test_table")
+    withr::defer(ds$cleanup())
+
+    sp <- QueryChatSystemPrompt$new(
+      prompt_template = "Schema: {{{schema}}}",
+      data_source = ds
+    )
+
+    expect_true(nchar(sp$schema) > 0)
+  })
+
+  it("computes schema for {{#schema}} conditional sections", {
+    df <- new_test_df()
+    ds <- DataFrameSource$new(df, "test_table")
+    withr::defer(ds$cleanup())
+
+    sp <- QueryChatSystemPrompt$new(
+      prompt_template = "{{#schema}}Has schema{{/schema}}",
+      data_source = ds
+    )
+
+    expect_true(nchar(sp$schema) > 0)
+  })
+})
diff --git a/pyproject.toml b/pyproject.toml
index dcfa6491..02ed2eed 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -66,7 +66,7 @@ include = ["pkg-py/src/querychat", "pkg-py/LICENSE", "pkg-py/README.md"]
 
 [dependency-groups]
 dev = ["ruff>=0.6.5", "pyright>=1.1.401", "tox-uv>=1.11.4", "pytest>=8.4.0", "polars>=1.0.0", "pyarrow>=14.0.0", "ibis-framework[duckdb]>=9.0.0"]
-docs = ["quartodoc>=0.11.1", "nbformat", "nbclient", "ipykernel"]
+docs = ["quartodoc>=0.11.1", "griffe<2", "nbformat", "nbclient", "ipykernel"]
 examples = [
     "openai",
     "palmerpenguins>=0.1.4",