# conda changelog

> A cross-platform package and environment manager.

- Vendor: Anaconda
- Category: Developer Tools
- Official site: https://docs.conda.io
- Tracked by: What's New (https://whatsnew.fyi/product/conda)
- Harvested from: GitHub (conda/conda)
- Entries below: 10 (newest first)

What's New is an index, not a publisher: every entry below links to the vendor's own release notes, which are the authoritative source. Entries are labelled where they are hand-curated sample data, pre-releases, or drawn from a secondary source such as a developer blog.

## Releases

### 26.7.0

- Date: 2026-07-31
- Version: 26.7.0
- Original notes: https://github.com/conda/conda/releases/tag/26.7.0
- Permalink: https://whatsnew.fyi/product/conda/releases/26.7.0

- **changed** — Replace runtime dependency on zstandard with compression.zstd (Python >=3.14) and backports.zstd (Python 3.10–3.13) for repodata and sharded repodata decompression
- **changed** — Defer concurrent.futures and threading imports in common/io.py so they only load when executor classes are first accessed
- **changed** — Defer heavy imports in exceptions.py to function level so they only load on error paths
- **changed** — Defer importing conda.plugins.types until it is imported explicitly or one of its deprecated re-exports is accessed
- **changed** — Defer ruamel.yaml import in common/serialize/yaml.py so it only loads when YAML parsing/writing is first needed
- **changed** — Cache context.root_writable for the lifetime of the Context instance to avoid opening a file on every access
- **changed** — Skip plugin loading for shell activation commands, avoiding ~430 imports when the plugin manager has not already been initialized
- **added** — Add conda.common.terminal module centralizing TTY detection and terminal output-mode logic with helpers is_tty(), no_color(), force_color(), and should_use_color()
- **changed** — Suppress progress-bar and spinner animations in the console reporter backend when the output is not a TTY or TERM=dumb/TERM=unknown is set
- **changed** — Replace the quadratic position scan in diff_for_unlink_link_precs() with linear order restoration for improved performance
- **changed** — Build a per-name candidate index in PrefixGraph.__init__() to accelerate graph construction for large prefixes
- **changed** — Extract built-in .conda and .tar.bz2 package archives with a process pool so zstd decompression can run outside the GIL
- **changed** — Batch per-file codesign invocations on osx-arm64 into one end-of-transaction call, reducing process launches
- **added** — Add structured error guidance to CondaError, including actionable terminal hints, a guidance field in --json output, and initial guidance for RemoveError, PackagesNotFoundError, and UnsatisfiableError
- **added** — Add search support for sharded repodata while disallowing conda search * to avoid downloading every shard
- **changed** — Improve conflicting plugin errors to list each provider by distribution name and version when available
- **added** — Add support for aliases on plugin-provided subcommands
- **added** — Make conda env create an alias of conda create
- **added** — Support displaying plugin parameter values with conda config --show-sources
- **added** — Add a conda_error_hints plugin hook for appending structured guidance hints to CondaError output

###### Enhancements

* Replace runtime dependency on `zstandard` with `compression.zstd` (Python >=3.14) and `backports.zstd` (Python 3.10–3.13) for repodata and sharded repodata decompression. (#15486 via #16191)
* Defer `concurrent.futures` and `threading` imports in `common/io.py` so they only load when executor classes (`DummyExecutor`, `ThreadLimitedThreadPoolExecutor`) are first accessed. (#15867 via #15881)
* Defer heavy imports in `exceptions.py` (`models.channel`, `auxlib.logz`, `common.io`, `common.iterators`, `serialize.json`) to function level so they only load on error paths. (#15867 via #15880)
* Defer importing `conda.plugins.types` until it is imported explicitly or one of its deprecated re-exports is accessed. (#15867 via #15893)
* Defer `ruamel.yaml` import in `common/serialize/yaml.py` so it only loads when YAML parsing/writing is first needed. (#15867 via #15882)
* Cache `context.root_writable` for the lifetime of the `Context` instance to avoid opening a file on every access. (#15867 via #15887)
* Skip plugin loading for shell activation commands (`conda shell.* activate | deactivate | reactivate | hook`),
  avoiding ~430 imports when the plugin manager has not already been initialized. Plugin authors should not rely
  on `pre_commands` / `post_commands` hooks running for these commands. (#15867 via #15877)
* Add `conda.common.terminal` module centralizing TTY detection and terminal output-mode logic with helpers `is_tty()`, `no_color()`, `force_color()`, and `should_use_color()` that respect the `NO_COLOR`, `FORCE_COLOR`, and `TERM=dumb`/`TERM=unknown` environment variables. (#15943 via #15982)
* Suppress progress-bar and spinner animations in the console reporter backend when the output is not a TTY or `TERM=dumb`/`TERM=unknown` is set. (#15943 via #15982)
* Replace the quadratic position scan in `diff_for_unlink_link_precs()` with linear order restoration. A focused synthetic benchmark with a 50,000-record prefix improved this function by about 780x. (#15969 via #15970)
* Build a per-name candidate index in `PrefixGraph.__init__()` to accelerate graph construction for large prefixes. (#15969 via #15971)
* Extract built-in `.conda` and `.tar.bz2` package archives with a process pool so zstd decompression can run outside the GIL, while keeping package-cache metadata updates in the parent process. (#15969 via #15974)
* Batch per-file `codesign` invocations on osx-arm64 into one end-of-transaction call, reducing process launches for packages with many prefix-replaced binaries. This does not affect other platforms. (#15969 via #15975)
* Add structured error guidance to `CondaError`, including actionable terminal hints, a `guidance` field in `--json` output, and initial guidance for `RemoveError`, `PackagesNotFoundError`, and `UnsatisfiableError`. (#16036 via #16160)
* Add search support for sharded repodata while disallowing `conda search *` to avoid downloading every shard. (#16134 via #16149)
* Improve conflicting plugin errors to list each provider by distribution name and version when available. (#16166)
* Add support for aliases on plugin-provided subcommands. (#16187 via #16188)
* Make `conda env create` an alias of `conda create`. (#15576 via #16210)
* Support displaying plugin parameter values with `conda config --show-sources`. (#16238 via #16246)
* Rework `InvalidInstaller` as a `CondaError` with structured guidance, removing redundant CLI try/except wrappers. (#16276)
* Add a `conda_error_hints` plugin hook for appending structured guidance hints to `CondaError` output. (#16290 via #16305)
* Introduce `conda.core.solve.BaseSolver` as the solver plugin base class. (#16320)
* Add channel notices cache directory to `conda info` output. (#16374)
* Suggest `conda self update` when the `conda-self` plugin is installed. (#16319 via #16414)
* Validate `--console` values against available reporter backends and reject unknown values with a clear error. (#16418 via #16420)

####

_[Truncated at 4000 characters — full notes: https://github.com/conda/conda/releases/tag/26.7.0]_

### 26.5.3

- Date: 2026-06-16
- Version: 26.5.3
- Original notes: https://github.com/conda/conda/releases/tag/26.5.3
- Permalink: https://whatsnew.fyi/product/conda/releases/26.5.3

- **fixed** — If shards were not found on a channel, conda would cache the not-found response, which can break shards-only channels. Instead, always check for sharded repodata if classic repodata has not been cached.
- **fixed** — Fix get_shortcut_dir() test helper to use the supplied prefix when detecting .nonadmin on Windows, aligning with menuinst 2.5 shortcut path behavior.

###### Bug fixes

* If shards were not found on a channel, conda would cache the not-found response, which can break shards-only channels. Instead, always check for sharded repodata if classic repodata has not been cached. (#16183)

###### Other

* Fix `get_shortcut_dir()` test helper to use the supplied prefix when detecting `.nonadmin` on Windows, aligning with menuinst 2.5 shortcut path behavior. (#16207)

###### Contributors

* @danyeaw
* @jezdez

**Full Changelog**: https://github.com/conda/conda/compare/26.5.2...26.5.3

### 26.5.2

- Date: 2026-06-01
- Version: 26.5.2
- Original notes: https://github.com/conda/conda/releases/tag/26.5.2
- Permalink: https://whatsnew.fyi/product/conda/releases/26.5.2

- **fixed** — Validate Python entry point definitions before generating entry point scripts

###### Bug fixes

* Validate Python entry point definitions before generating entry point scripts. (#16168)

###### Contributors

* @jaimergp


**Full Changelog**: https://github.com/conda/conda/compare/26.5.1...26.5.2

### 26.5.1

- Date: 2026-05-26
- Version: 26.5.1
- Original notes: https://github.com/conda/conda/releases/tag/26.5.1
- Permalink: https://whatsnew.fyi/product/conda/releases/26.5.1

- **fixed** — Fix channel notices display failing with ImportError when a decorated command replaces base python while conda is still running on the previous interpreter by pre-importing conda.notices.views before the command
- **fixed** — Fix crash in UnavailableInvalidChannel and CondaHTTPError when simplejson is installed and a non-JSON HTTP error response is received

###### Bug fixes

* Fix channel notices display failing with `ImportError` when a decorated command replaces base `python` while conda is still running on the previous interpreter. Pre-import `conda.notices.views` before the command so post-command display does not load modules from rewritten `site-packages`. (#16126 via #16142)
* Fix crash in `UnavailableInvalidChannel` and `CondaHTTPError` when `simplejson` is installed and a non-JSON HTTP error response is received. (#16136)

###### Contributors

* @jezdez
* @kenodegard

**Full Changelog**: https://github.com/conda/conda/compare/26.5.0...26.5.1

### 26.5.0

- Date: 2026-05-15
- Version: 26.5.0
- Original notes: https://github.com/conda/conda/releases/tag/26.5.0
- Permalink: https://whatsnew.fyi/product/conda/releases/26.5.0

- **added** — Add parsing and storage support for conditional dependencies, optional dependency groups, and variant flags in MatchSpec expressions
- **added** — Add --clobber flag to conda create, matching existing support in conda install and conda update
- **added** — Display a warning when exporting lockfiles from environments containing packages installed with pip, uv, or other 3rd party Python package managers
- **changed** — Speed up condarc search path expansion on every reset_context() by ~5x via cheaper custom_expandvars() and os.scandir()-based directory traversal
- **changed** — Drop the ChannelType metaclass from conda.models.channel.Channel and move single-argument Channel(value) construction to Channel.__new__
- **changed** — Remove redundant context.__init__() call in main_subshell()
- **changed** — ContextStack now allocates a single slot on construction instead of three
- **changed** — Resolve._get_reduced_index() no longer uses copy.deepcopy() to snapshot specs_by_name
- **changed** — Defer heavy imports in notices/core.py and cli/main_env.py to reduce module cost of loading individual subcommand modules
- **added** — Add fast path for conda --version and conda -V that prints the version and exits without loading the argument parser, context, or plugin system
- **changed** — Replace f-string log calls with %-style lazy formatting across the codebase
- **changed** — context.category_map is now a @memoizedproperty instead of being rebuilt on every access
- **changed** — Hot-path regexes in conda/models/match_spec.py and conda/activate.py are now compiled once at module load time
- **changed** — PrefixData._load_single_record() now reads conda-meta JSON files with Path.read_bytes() and json.loads() instead of opening a text file handle
- **added** — Port sharded repodata implementation from conda-libmamba-solver
- **added** — Add conda_exception_observers plugin hook for observational callbacks on any exception conda encounters
- **added** — Add default-implemented available_platforms and env_for(platform) on EnvironmentSpecBase for multi-platform environment specifiers
- **added** — Add PlatformMismatchError exception and checks in conda env create and conda env update for platform coverage validation
- **added** — Add context.preview configuration parameter via CONDA_PREVIEW env var or preview: in .condarc for opt-in feature previews
- **changed** — Rewrite help text for conda create, conda export, conda env create, and conda env export to make lockfile workflows discoverable

##### 26.5.0 (2026-05-15)

###### Enhancements

* Add parsing and storage support for conditional dependencies, optional dependency groups, and variant flags in `MatchSpec` expressions (introduced in [conda/ceps#164](https://github.com/conda/ceps/pull/164), [conda/ceps#165](https://github.com/conda/ceps/pull/165), and [conda/ceps#166](https://github.com/conda/ceps/pull/166)). (#15443)
* Add `--clobber` flag to `conda create`, matching existing support in `conda install` and `conda update`. (#15584 via #15801)
* Display a Warning when exporting lockfiles from environments containing packages installed with pip, uv, or other 3rd party Python package managers. (#15581 via #15838)
* Speed up condarc search path expansion on every `reset_context()` by ~5x (~1.35 ms/call to ~0.27 ms/call on a 27-entry path), via cheaper `custom_expandvars()` and `os.scandir()`-based directory traversal in `Configuration._expand_search_path()`. (#15867)
* Drop the `ChannelType` metaclass from `conda.models.channel.Channel`. Single-argument
  `Channel(value)` construction and `MultiChannel` dispatch have moved to `Channel.__new__`,
  and the per-value cache is now `@functools.cache` on `Channel.from_value`. (#15867)
* Remove a redundant `context.__init__()` call in `main_subshell()`. The first initialization with `pre_args` was immediately repeated after the `no_plugins` check without any change in arguments. (#15867)
* `ContextStack` now allocates a single slot on construction instead of three.
  Slots are still doubled on demand, so deep nesting works identically.
  Eliminates two unnecessary `ContextStackObject` allocations at import time.
  (#15867)
* `Resolve._get_reduced_index()` no longer uses `copy.deepcopy()` to snapshot
  `specs_by_name`. A dict comprehension with slice copies (`v[:]`) is sufficient
  because `MatchSpec` objects are immutable. Removes the `import copy` from
  `resolve.py`. (#15867)
* Defer heavy imports in `notices/core.py` and `cli/main_env.py` to reduce the module cost of loading individual subcommand modules. (#15867)
* Add fast path for `conda --version` / `conda -V` that prints the version and exits without loading the argument parser, context, or plugin system. (#15867)
* Replace f-string log calls with `%`-style lazy formatting across the
  codebase. String interpolation is now deferred until the log record is
  actually emitted. Enable the ruff `G004` rule to enforce this going
  forward. (#15867)
* `context.category_map` is now a `@memoizedproperty`. The large static dict
  was rebuilt on every access; it is now constructed once and cached for the
  lifetime of the `Context` instance. (#15867)
* Hot-path regexes in `conda/models/match_spec.py` and `conda/activate.py` are
  now compiled once at module load time instead of on every call.
  Removes repeated `re.compile()` overhead from the `MatchSpec` parser and the
  shell activation path resolver. (#15867)
* `PrefixData._load_single_record()` now reads the conda-meta JSON file with
  `Path.read_bytes()` + `json.loads()` instead of opening a text file handle
  and calling `json.load()`. For the small files typical of conda-meta records,
  a single read syscall followed by an in-memory parse is faster than the
  incremental read performed by `json.load()`. (#15867)
* Add Ruff `TID253` rule to ban module-level imports of `requests` on the startup path, preventing accidental re-introduction of heavy import chains (e.g. the A1 regression fixed in #15866). Files in `conda/gateways/` and other non-startup-path locations that legitimately import `requests` are annotated with `# noqa: TID253`.
* Port sharded repodata implementation from conda-libmamba-solver. (#15906)
* Add `conda_exception_observers` plugin hook for observational callbacks on any exception conda encounters (filterable per observer via `watch_for`). (#15910)
* Bump `conda-incubator/setup-miniconda` to v4.0.0 across `.github/workflows/tests.yml`. v4.0.0 ships the perf w

_[Truncated at 4000 characters — full notes: https://github.com/conda/conda/releases/tag/26.5.0]_

### 26.3.2

- Date: 2026-04-10
- Version: 26.3.2
- Original notes: https://github.com/conda/conda/releases/tag/26.3.2
- Permalink: https://whatsnew.fyi/product/conda/releases/26.3.2

- **fixed** — Revert inline environment activation for and subsequent optimizations to conda run due to regressions with post-link scripts

###### Bug fixes

* Revert inline environment activation for and subsequent optimizations to `conda run` (#15534, #15672), due to regressions with post-link scripts. (#15896)

###### Contributors

* @agriyakhetarpal

**Full Changelog**: https://github.com/conda/conda/compare/26.3.1...26.3.2

### 26.3.1

- Date: 2026-04-03
- Version: 26.3.1
- Original notes: https://github.com/conda/conda/releases/tag/26.3.1
- Permalink: https://whatsnew.fyi/product/conda/releases/26.3.1

- **added** — Record the originating hook for each plugin, enabling conda info and diagnostics to show where plugins were registered from
- **deprecated** — No longer search for conda-* executables on PATH when building the CLI parser
- **deprecated** — Mark conda.cli.find_commands as pending deprecation for removal in 27.3
- **deprecated** — Mark conda.utils.sys_prefix_unfollowed as pending deprecation for removal in 27.3
- **deprecated** — Mark conda.exceptions.CommandNotFoundError as pending deprecation for removal in 27.3

###### Enhancements

* Record the originating hook for each plugin, enabling `conda info` and diagnostics to show where plugins were registered from. (#15840)

###### Deprecations

* No longer search for `conda-*` executables on `PATH` when building the CLI parser. (#15840)
* Mark `conda.cli.find_commands` as pending deprecation for removal in 27.3. (#15840)
* Mark `conda.utils.sys_prefix_unfollowed` as pending deprecation for removal in 27.3. (#15840)
* Mark `conda.exceptions.CommandNotFoundError` as pending deprecation for removal in 27.3. (#15840)

###### Contributors

* @kenodegard

**Full Changelog**: https://github.com/conda/conda/compare/26.3.0...26.3.1

### 26.3.0

- Date: 2026-03-31
- Version: 26.3.0
- Original notes: https://github.com/conda/conda/releases/tag/26.3.0
- Permalink: https://whatsnew.fyi/product/conda/releases/26.3.0

- **changed** — Improve handling of Windows CMD.EXE activation for environment paths that contain the caret (^) character
- **added** — Add support for PackageRecord.requested_specs to store all MatchSpec objects involved in requesting a package
- **added** — Add unmerged_specs_to_add and unmerged_specs_to_remove attributes to conda.core.solve.Solver
- **changed** — Pass unmerged MatchSpec objects to pre-solve plugins instead of pre-merged
- **added** — Add option to disable redefining Fish shell prompt functions in conda init
- **changed** — conda create --file now supports environment.yaml files and automatically detects name and prefix
- **added** — Add description and environment_format metadata fields to environment plugin types
- **changed** — Optimize S3 downloads to avoid an extra file copy through a temporary buffer
- **added** — Add PackagesNotFoundInChannelsError and PackagesNotFoundInPrefixError as specialized cases of PackagesNotFoundError
- **changed** — Always include conda-meta manifest file size in PrefixRecord.package_size() so metapackages display non-zero size
- **changed** — Speed up conda run by dropping the shell hook subprocess and relying on inline activators
- **changed** — conda remove with the classic solver now exits early if the spec to be removed does not exist
- **changed** — conda search --envs now raises an error when the package is not found in any environment
- **added** — Add support for defining aliases of environment spec plugins
- **added** — Add pattern matching support to environment specifier and exporter plugins via default_filenames field
- **added** — conda create|install -f is now recognized as an alias to conda create|install --file
- **changed** — Improve log messages when conda auto-detects the applicable environment file format
- **fixed** — Fix conda config --show-sources displaying frozendict.frozendict(...) instead of readable dict format
- **fixed** — Do not include pip-installed packages in the list of explicit packages when building an environment from prefix
- **fixed** — Use bundled Windows stub executables for creating entry points instead of relying on Scripts/conda.exe
- **fixed** — Use case-insensitive matching when finding Python metadata files on Windows
- **fixed** — Always include the dependencies field when exporting an environment.yaml-style environment for CEP-24 compliance
- **fixed** — Fix package resolution regression for custom multichannels
- **fixed** — Allow conda search --offline to use the local channel cache
- **fixed** — Fix win-arm64 subdir detection on native Windows ARM64 by matching uppercase ARM64
- **fixed** — Ignore JSON metadata paths beginning with ._ when loading prefix data

###### Enhancements

* Improve handling of Windows CMD.EXE activation for environment paths that contain the `^` (caret) character. (#12558 via #15628)
* Add support for `PackageRecord.requested_specs`. This will store all the MatchSpec objects that were involved in requesting a package (instead of a single, pre-merged object). To that end, two new attributes in `conda.core.solve.Solver`, `unmerged_specs_to_add` and `unmerged_specs_to_remove`, store the list of input specs as received, instead of always attempting to merge them. (#15111 via #15110)
* Pass unmerged MatchSpec objects to `pre-solve` plugins (instead of pre-merged). (#15110)
* Add option to disable redefining Fish shell prompt functions in conda init. (#15545 via #15549)
* `conda create --file <filename>` now supports environment.yaml files as well as requirements.txt and explicit environment exports, and detects name and prefix automatically when `--name` / `--prefix` are omitted. (#15573 via #15770)
* Add `description` and `environment_format` metadata fields to environment plugin types (`CondaEnvironmentSpecifier` and `CondaEnvironmentExporter`). (#15577 via #15763)
* Optimize S3 downloads to avoid an extra file copy through a temporary buffer. (#15636)
* Add path customization parameters to `tmp_env` fixture (`name`, `path_prefix`, `path_infix`, `path_suffix`) that pass through to `path_factory`. Add "parts mode" to `path_factory` where specifying `prefix`, `infix`, or `suffix` triggers UUID defaults for unspecified parts, enabling easier special character path testing. (#15650)
* Add `PackagesNotFoundInChannelsError` and `PackagesNotFoundInPrefixError` as specialized cases of `PackagesNotFoundError`, to distinguish between packages missing from configured channels and packages missing from a specific environment prefix. (#12197 via #15653)
* Always include conda-meta manifest file size in `PrefixRecord.package_size()`, so packages with no files (such as metapackages, mutex packages) display a non-zero size instead of "0 B" in `conda list --size`. (#15681 via #15656)
* Speed up `conda run` by dropping the shell hook subprocess and relying on inline activators. (#14993 via #15672)
* `conda remove <spec>` with the classic solver now exits early if the spec to be removed does not exist in the environment. (#15697)
* `conda search --envs <package>` now raises an error when the package is not found in any environment. (#15698)
* Add support for defining aliases of environment spec plugins. (#15701)
* Add pattern matching support to environment specifier and exporter plugins via `default_filenames` field. Plugins can now use wildcards (e.g., `*.conda-lock.yml`) for filename-based detection. (#15717 via #15719)
* `conda create|install -f` is now recognized as an alias to `conda create|install --file`. (#15790)
* Improve log messages when conda auto-detects the applicable environment file format. (#15736)

###### Bug fixes

* Fix `conda config --show-sources` displaying `frozendict.frozendict(...)` for `channel_settings` entries instead of readable dict format. (#15505 via #15789)
* Do not include pip-installed packages in the list of explicit packages when building a `conda.models.Environment` with `conda.models.Environment.from_prefix`. (#15619)
* Use bundled Windows stub executables (`conda/shell/cli-32.exe`, `conda/shell/cli-64.exe`) for creating entry points instead of relying on `Scripts/conda.exe` so that entry point creation works when conda is not installed as a conda package (e.g. tests via `python -m pytest`). Select the correct exe for the target env via a platform-to-stub mapping; for win-arm64 use `cli-64.exe` (relying on Windows x64-on-ARM64 emulation). Use target platform for `conda init` as well, fixing cross-architecture installs (e.g. win-32 host creating a win-64 env). (#15678)
* Use case-insensitive matching when finding Python metadata files on Windows to make sure they are correctly identified as conda packages. (#15153

_[Truncated at 4000 characters — full notes: https://github.com/conda/conda/releases/tag/26.3.0]_

### 26.1.1

- Date: 2026-02-17
- Version: 26.1.1
- Original notes: https://github.com/conda/conda/releases/tag/26.1.1
- Permalink: https://whatsnew.fyi/product/conda/releases/26.1.1

- **fixed** — Fix conda doctor --fix failing with install() missing 1 required positional argument: 'parser' when attempting to fix packages with missing files

###### Bug fixes

* Fix `conda doctor --fix` failing with `install() missing 1 required positional argument: 'parser'` when attempting to fix packages with missing files. (#15669)

###### Contributors

* @jezdez

**Full Changelog**: https://github.com/conda/conda/compare/26.1.0...26.1.1

### 26.1.0

- Date: 2026-01-30
- Version: 26.1.0
- Original notes: https://github.com/conda/conda/releases/tag/26.1.0
- Permalink: https://whatsnew.fyi/product/conda/releases/26.1.0

- **added** — Allow `custom_multichannels.defaults` to override `default_channels`
- **changed** — Defer `PrefixData` record instantiation until they are accessed for faster query performance
- **added** — Add support for Python 3.14
- **changed** — Speed up the context initialization process by caching condarc file reads
- **added** — Raise a `NoChannelsConfiguredError` when attempting to solve an environment with no channels configured
- **added** — Add `conda.cli.condarc.ConfigurationFile` class to expose configuration file manipulation interface programmatically
- **added** — Add `-s` as a shorthand alias for `conda run --no-capture-output`
- **changed** — `conda run` now deactivates the environment on exiting the command
- **changed** — Rename `conda.models.enums.PathType` enum to `conda.models.enums.PathEnum`
- **security** — Validate plugin-provided HTTP headers and raise `PluginError` if forbidden headers are detected
- **added** — Add `conda_package_extractors` plugin hook to allow plugins to register custom package archive extractors
- **added** — Add `-O` as a flag alias for `--override-channels`
- **added** — Add reusable `http_test_server` fixture to `conda.testing` module for serving mock conda channels and remote files in tests
- **changed** — Speed up `conda run` by inlining environment activation instead of using a subprocess
- **added** — Add a `--size` flag to the `conda info --envs` and `conda env list` commands to display disk usage for each environment
- **added** — Add `PrefixRecord.package_size()` and `PrefixData.size` for programmatic access to conda-managed disk usage
- **added** — Add `--size` flag to `conda list` to show environment size and package sizes
- **changed** — Improve error messages for HTTP 403 (Forbidden) responses with context-aware guidance on authentication and permissions
- **changed** — Improve error message when `conda activate` fails on Windows due to unwritable `%TEMP%` directory
- **changed** — Package extension detection is now dynamic based on registered `conda_package_extractors` plugins

###### Enhancements

* Allow `custom_multichannels.defaults` to override `default_channels`. Continuation of effort to devendor conda and remove hardcoded "defaults" channel. (#14661)
* Defer `PrefixData` record instantiation until they are accessed for faster query performance. (#14811)
* Add support for Python 3.14. (#15080, #15618)
* Speed up the context initialization process by caching condarc file reads. (#15150)
* Raise a `NoChannelsConfiguredError` when attempting to solve an environment with no channels configured, and provide a helpful message to guide users in adding channels. (#15262 via #15345)
* Add `conda.cli.condarc.ConfigurationFile` class to expose configuration file manipulation interface programmatically. This allows other Python interfaces to read and modify conda configuration files without shelling out to `conda config` commands. (#15238 via #15376)
* Add `-s` as a shorthand alias for `conda run --no-capture-output`. (#15426)
* `conda run` now deactivates the environment on exiting the command. (#15427)
* Rename `conda.models.enums.PathType` enum to `conda.models.enums.PathEnum` to resolve a naming conflict with the `PathType` type annotation. This change follows modern Python conventions and establishes the `*Enum` suffix as the pattern for enums in the codebase. (#15428)
* Validate plugin-provided HTTP headers and raise `PluginError` if forbidden headers are detected, preventing plugins from compromising conda's network stack. (#15405 via #15436)
* Add `conda_package_extractors` plugin hook to allow plugins to register custom package archive extractors. (#15524 via #15441)
* Add `-O` as a flag alias for `--override-channels`. (#15499)
* Add reusable `http_test_server` fixture to `conda.testing` module for serving mock conda channels and remote files in tests. Fixture uses standard `@pytest.mark.parametrize()` with `indirect=True` for configuring directories, supporting both pre-existing directories and dynamic content generation. Provides clean API with `get_url()` helper method and `directory` attribute. (#15528 via #15529)
* Speed up `conda run` by inlining environment activation instead of using a subprocess. (#15534)
* Add a `--size` flag to the `conda info --envs` and `conda env list` commands to display disk usage for each environment. (#8040 and #15544)
* Add `PrefixRecord.package_size()` and `PrefixData.size` for programmatic access to conda-managed disk usage. (#15544)
* Add `--size` flag to `conda list` to show environment size and package sizes. (#15544)
* Improve error messages for HTTP 403 (Forbidden) responses with context-aware guidance on authentication and permissions. (#15594)
* Improve error message when `conda activate` fails on Windows due to unwritable `%TEMP%` directory. (#15601 via #15602)
* Package extension detection is now dynamic based on registered `conda_package_extractors` plugins. (#15629)
* Allow `conda create --download-only` to run without specifying `-n/--name` or `-p/--prefix`, similar to `--dry-run`. (#15633)
* Add `--fix` flag to `conda doctor` with health check fix capabilities. (#15530)
* Improve error message when `conda env export` is invoked with an invalid platform. (#15561)

###### Bug fixes

* Stop `conda run` from adding an additional new line after printing to `stdout` or `stderr`. (#11763 via #15539)
* Non-conda installed Python packages now show up in `conda list` in free-threading environments. (#14674)
* Fix Python packages not being listed as from the `pypi` channel if the `site-packages` directory includes a symlink. (#14674)
* Replace deprecated `codecs.open()` with built-in `open()` for Python 3.14 compatibility. (#15080)
* Fix parallel conda command failures on Windows (e.g., `start /b`) by using GUIDs for unique temp filenames instead of `%RANDOM%`. (#15169 via #15598)
* Sanitize channel config input to remove null values. (#15268 via #15323)
* Fix `conda list --fields dist_str` representation. (#15420)
* Add

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