Environment variable reference#

conda-presto reads these settings when its configuration module is imported. The scope column distinguishes direct solves, public HTTP servers, and the broker-only solver service.

Direct solve settings#

These settings affect conda presto and public HTTP resolve operations. The internal conda --solver=presto path captures effective state from the calling conda process instead.

Variable	Default	Scope	Purpose
`CONDA_PRESTO_CHANNELS`	`conda-forge`	Direct CLI and HTTP	HTTP fallback when no request or input file supplies channels. CLI fallback when conda’s effective channels are empty or only `defaults` and no file supplies channels. Also used for server startup warmup.
`CONDA_PRESTO_WORKERS`	`min(4, cpu_count)`	Direct multi-platform solves	Process-pool size for platforms within one request.
`CONDA_PRESTO_MAX_INDEX_CACHE_ENTRIES`	`128`	Direct solve processes	Maximum retained rattler indexes. Set to `0` to disable index retention.
`CONDA_PRESTO_GLIBC_VERSION`	`2.17`	Direct Linux solves	Injected virtual `__glibc` version.
`CONDA_PRESTO_LINUX_VERSION`	`5.15`	Direct Linux solves	Injected virtual `__linux` version.
`CONDA_PRESTO_OSX_VERSION`	`11.0`	Direct macOS solves	Injected virtual `__osx` version.
`CONDA_PRESTO_WIN_VERSION`	`0`	Direct Windows solves	Injected virtual `__win` version.

Direct CLI and public HTTP solves apply these target-model overrides for each requested Linux, macOS, or Windows target, including the host’s native subdir. The resulting effective records can also include other virtual-package plugin detections or overrides, such as CUDA or architecture records. The public result-cache identity captures those effective records per requested platform. The internal Presto solver does not use these four defaults. It serializes and restores the calling conda process’s effective virtual-package records. Those records also participate in private solver cache identity.

HTTP server settings#

Variable	Default	Purpose
`CONDA_PRESTO_PLATFORMS`	`linux-64,osx-arm64,osx-64`	Platforms whose configured channels are warmed before readiness. This is not the default platform list for a request.
`CONDA_PRESTO_ALLOWED_CHANNELS`	value of `CONDA_PRESTO_CHANNELS`	Accepted HTTP request channels after exact resolved-URL comparison. `*` permits HTTP and HTTPS channels but not local file URLs.
`CONDA_PRESTO_CONCURRENCY`	`4`	Maximum simultaneous foreground solve requests. Docker and the broker provider set `1`.
`CONDA_PRESTO_MAX_BODY_BYTES`	`1048576`	Maximum HTTP request body. Excess returns HTTP 413.
`CONDA_PRESTO_MAX_SPECS`	`200`	Maximum specs in one request.
`CONDA_PRESTO_MAX_CHANNELS`	`8`	Maximum channels in one request.
`CONDA_PRESTO_MAX_PLATFORMS`	`8`	Maximum platforms in one request.
`CONDA_PRESTO_MAX_SOLVER_CHANNELS`	`128`	Maximum channels in the private broker solver protocol.
`CONDA_PRESTO_MAX_SOLVER_STATE_ITEMS`	`10000`	Maximum combined items across requested additions, removals, installed records, history, pins, virtual packages, aggressive updates, and always-update entries in the private broker solver protocol.
`CONDA_PRESTO_MAX_REPAIR_SUGGESTIONS`	`5`	Server ceiling for returned repair suggestions.
`CONDA_PRESTO_MAX_REPAIR_ATTEMPTS`	`20`	Server ceiling for evaluated repair candidates.
`CONDA_PRESTO_MAX_REPAIR_TIME_BUDGET_MS`	`5000`	Server ceiling for repair wall time in milliseconds.
`CONDA_PRESTO_SOLVE_TIMEOUT_S`	`60`	Solver deadline used by HTTP requests, the internal solver client, and scheduled refresh where lower than fixed limits. Non-abandoned cache-state inspection can extend observed request duration.
`CONDA_PRESTO_PARSE_TIMEOUT_S`	`10`	HTTP file-parse timeout.
`CONDA_PRESTO_HOST`	`127.0.0.1`	Default for the `--host` server flag. The Docker command fixes `0.0.0.0`, and the broker provider fixes `127.0.0.1`.
`CONDA_PRESTO_PORT`	`8000`	Default for the `--port` server flag. The broker assigns it. The Docker health check remains fixed to port 8000.
`CONDA_PRESTO_PERSISTENT_WORKER`	`false`	Route HTTP solves through one worker that retains loaded repodata and indexes. Set by Docker and the broker provider.
`CONDA_PRESTO_RATE_LIMIT`	`300`	Requests per minute per client IP. Set to `0` to disable. The broker provider sets `0`.
`CONDA_PRESTO_CORS_ORIGINS`	unset	Comma-separated browser origins. CORS middleware is absent when unset.
`CONDA_PRESTO_LOG_LEVEL`	`INFO`	Application logger level: `DEBUG`, `INFO`, `WARNING`, or `ERROR`.

Request-cap violations return HTTP 400 unless the body limit applies. Repair query values below the configured ceilings narrow one request. Values above the ceilings are clamped.

Result cache settings#

These settings apply to any HTTP application process, including Docker and the broker service. One-shot CLI output does not use the HTTP result cache.

Variable	Default	Purpose
`CONDA_PRESTO_RESULT_CACHE_SIZE`	`256`	Combined in-process entry limit for public resolve responses and private solver final states.
`CONDA_PRESTO_RESULT_CACHE_MAX_MEMORY_MB`	`64`	Combined encoded payload limit in MiB. Set to `0` to remove the byte cap.
`CONDA_PRESTO_RESULT_CACHE_BACKEND`	automatic	`memory`, `file`, or `redis`.
`CONDA_PRESTO_RESULT_CACHE_DIR`	unset	Directory required by the file backend. Selecting no backend but setting this value selects file storage.
`CONDA_PRESTO_RESULT_CACHE_REDIS_URL`	unset	Redis URL. Selecting Redis without a URL uses `redis://localhost:6379/0`. Setting this value selects Redis when no backend is explicit.
`CONDA_PRESTO_RESULT_CACHE_REDIS_NAMESPACE`	`conda-presto`	Redis key namespace.

Negative entry or memory limits are rejected. File storage without a directory and unknown backend names are also rejected. See Cache reference for key and retention behavior.

Broker-only refresh settings#

These settings are loaded by every server process, but scheduled refresh is enabled only for the persistent conda-presto.server broker child.

Variable	Default	Purpose
`CONDA_PRESTO_SOLVER_CACHE_WARM_CANDIDATE_SIZE`	`32`	Maximum recorded requests in the candidate catalog, plus the same observation capacity. Set to `0` to disable recording.
`CONDA_PRESTO_SOLVER_CACHE_WARM_CANDIDATE_PERSIST`	`false`	Best-effort checkpointing of requests without detected credentials. Requires file or Redis storage.
`CONDA_PRESTO_SOLVER_CACHE_WARM_INTERVAL_S`	`300`	Seconds between scheduled cycles. Set to `0` to disable scheduling.
`CONDA_PRESTO_SOLVER_CACHE_WARM_BATCH_SIZE`	`8`	Maximum eligible requests considered per cycle. Must be positive.

The first cycle has a fixed 30-second delay. Fixed per-operation and cycle budgets are documented in Cache reference.

Broker-injected variables#

conda-broker supplies these values to the service child. They are integration state, not normal user configuration.

Variable	Value	Consumer
`CONDA_BROKER_SERVICE_NAME`	`conda-presto.server`	Enables the guarded private solver route and scheduled refresh.
`CONDA_PRESTO_URL`	Allocated loopback endpoint	Broker health-check command and service consumers.
`CONDA_PRESTO_PORT`	Allocated port	Uvicorn bind configuration.

The provider also overrides host, concurrency, rate limiting, persistent-worker mode, and conda file locking. See Broker service reference.

Pixi activation settings#

The repository’s Pixi environments set these conda variables for solve-only workloads:

Variable	Value	Effect
`CONDA_SOLVER`	`rattler`	Select rattler in conda context before conda-presto applies its direct-engine requirement.
`CONDA_CHANNEL_PRIORITY`	`strict`	Prefer higher-priority channels.
`CONDA_NO_LOCK`	`true`	Disable conda filesystem locking in the shared Pixi activation. The Docker server and broker child override this to `false`.
`CONDA_UNSATISFIABLE_HINTS`	`false`	Disable conda’s additional unsatisfiable hint generation.
`CONDA_NUMBER_CHANNEL_NOTICES`	`0`	Suppress channel notices.
`CONDA_AGGRESSIVE_UPDATE_PACKAGES`	empty	Disable forced aggressive updates.
`CONDA_LOCAL_REPODATA_TTL`	`300`	Reuse local repodata under conda’s effective cache policy.
`CONDA_JSON`	`true`	Suppress progress-oriented conda output.

The Docker server applies CONDA_NO_LOCK=false after its Pixi shell hook, and the broker child injects the same value. Their persistent worker processes share conda’s package cache. The one-shot CLI image keeps the Pixi activation default.