diff --git a/.dockerignore b/.dockerignore
index 8e02efbf0..33f7c5c6b 100644
--- a/.dockerignore
+++ b/.dockerignore
@@ -12,5 +12,75 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-# Ignore this in case the user previously did a "pip install -e ."
-qsimcirq.egg-info
+# Git metadata (wildcarded because this project uses a git submodule).
+**/.git
+
+# Coverage & test artifacts.
+**/*.benchmarks
+**/*.cover
+**/*.py,cover
+**/.coverage
+**/.coverage.*
+**/coverage.xml
+
+# Environments & IDEs.
+.dockerignore
+.env*
+.gemini*
+.github
+.idea
+.python-version
+.venv
+.vscode
+CirqDevEnv
+env
+venv
+
+# Build outputs & tool caches.
+**/.*_cache
+**/.cache
+**/.eggs
+**/.ipynb_checkpoints
+**/__pycache__
+**/cmake_install.cmake
+**/CMakeCache.txt
+**/CMakeFiles
+bazel-*
+build
+dist
+eigen
+sdist
+wheelhouse
+
+# Compilation artifacts.
+**/*.a
+**/*.dSYM
+**/*.dll
+**/*.dylib
+**/*.exe
+**/*.lib
+**/*.mod
+**/*.o
+**/*.obj
+**/*.out
+**/*.py[cod]
+**/*.so
+**/*.x
+
+# Local PyPI config files.
+.pypirc
+
+# Things that don't need to be in a Docker inage.
+dev_tools/ci
+docs
+
+# Miscellaneous other files.
+**/*~
+**/*.bak
+**/*.egg
+**/*.egg-info
+**/*.log
+**/*.swp
+**/*.tmp
+**/*.whl
+**/.DS_Store
diff --git a/.geminiignore b/.geminiignore
index 947c71cec..bbc9603ef 100644
--- a/.geminiignore
+++ b/.geminiignore
@@ -19,3 +19,7 @@
 
 # Not in .gitignore because it's a git submodule. Tell Gemini to ignore it.
 /tests/googletest/
+
+# The next one (for Emacs versioned backups) _should_ be covered by *~ in our
+# .gitignore, but Gemini currently doesn't seem to interpret *~ that way.
+*.~*~
diff --git a/.gitignore b/.gitignore
index 7eee8e4e8..b5759ccc1 100644
--- a/.gitignore
+++ b/.gitignore
@@ -38,12 +38,9 @@ ipython_config.py
 .cache/
 .dmypy.json
 .mypy_cache/
-.nox/
 .pytest_cache/
 .python-version
-.pytype/
 .ruff_cache/
-.tox/
 __pycache__/
 build/
 coverage.xml