powersync-ja · bean1352 · Sep 2, 2026 · Sep 2, 2026 · Sep 3, 2026 · Sep 3, 2026
diff --git a/.changeset/show-target-instance.md b/.changeset/show-target-instance.md
@@ -0,0 +1,8 @@
+---
+'@powersync/cli-core': patch
+'powersync': patch
+---
+
+Show the target instance name and IDs before `deploy`, `deploy sync-config`, `deploy service-config`, `stop`, `destroy` and `compact` do anything, so it is clear which instance is about to be changed. `status` shows the target first as well, with the API URL for self-hosted instances. `deploy` and `deploy service-config` now also warn when the local `service.yaml` `name` differs from the instance name, since deploying renames the instance.
+
+All deploy commands accept `--dry-run`, which prints the target instance, runs the validations, shows a diff of the sync config and the changed service config sections, and stops without deploying.
diff --git a/cli/README.md b/cli/README.md
@@ -99,7 +99,7 @@ powersync link cloud --create --project-id=<project-id>   # add --org-id if toke
 powersync deploy
 ```
 
-Use `--directory` for a different config folder. The **powersync init cloud** command has a `--vscode` flag to configure your workspace for YAML custom tag support.
+Use `--directory` for a different config folder. Add `--dry-run` to a deploy command to print the target instance, run the validations and see what would change, without deploying. The **powersync init cloud** command has a `--vscode` flag to configure your workspace for YAML custom tag support.
 
 ## Cloud secrets format (`service.yaml`)
 
@@ -429,12 +429,14 @@ _See code: [src/commands/configure/ide.ts](https://github.com/powersync-ja/power
 
 ```
 USAGE
-  $ powersync deploy [--deploy-timeout <value>] [--directory <value>] [--instance-id <value>]
+  $ powersync deploy [--deploy-timeout <value>] [--dry-run] [--directory <value>] [--instance-id <value>]
     [--sync-config-file-path <value>] [--skip-validations <value> | --validate-only <value>]
 
 FLAGS
   --deploy-timeout=<value>    [default: 300] Seconds to wait after scheduling a deploy before timing out while polling
                               status (default 300 seconds).
+  --dry-run                   Show the target instance, run the validations and print what would change, then exit
+                              without deploying.
   --skip-validations=<value>  Comma-separated list of validation tests to skip. Options: configuration, connections,
                               sync-config. Example: --skip-validations="configuration"
   --validate-only=<value>     Comma-separated list of validation tests to run, skipping all others. Options:
@@ -457,10 +459,13 @@ DESCRIPTION
   Validates connections and sync config before deploying.
   See also powersync deploy sync-config to deploy only sync config changes.
   See also powersync deploy service-config to deploy only service config changes.
+  Use --dry-run to show the target instance, the validation results and what would change, without deploying.
 
 EXAMPLES
   $ powersync deploy
 
+  $ powersync deploy --dry-run
+
   $ powersync deploy --instance-id=<id>
 ```
 
@@ -472,12 +477,14 @@ _See code: [src/commands/deploy/index.ts](https://github.com/powersync-ja/powers
 
 ```
 USAGE
-  $ powersync deploy service-config [--deploy-timeout <value>] [--directory <value>] [--instance-id <value>]
+  $ powersync deploy service-config [--deploy-timeout <value>] [--dry-run] [--directory <value>] [--instance-id <value>]
     [--skip-validations <value> | --validate-only <value>]
 
 FLAGS
   --deploy-timeout=<value>    [default: 300] Seconds to wait after scheduling a deploy before timing out while polling
                               status (default 300 seconds).
+  --dry-run                   Show the target instance, run the validations and print what would change, then exit
+                              without deploying.
   --skip-validations=<value>  Comma-separated list of validation tests to skip. Options: configuration, connections.
                               Example: --skip-validations="configuration"
   --validate-only=<value>     Comma-separated list of validation tests to run, skipping all others. Options:
@@ -494,11 +501,14 @@ CLOUD_PROJECT FLAGS
 DESCRIPTION
   [Cloud only] Deploy only local service config to the linked Cloud instance.
 
-  Deploy only service config changes (without sync config updates).
+  Deploy only service config changes (without sync config updates). Use --dry-run to show the target instance, the
+  validation results and what would change, without deploying.
 
 EXAMPLES
   $ powersync deploy service-config
 
+  $ powersync deploy service-config --dry-run
+
   $ powersync deploy service-config --instance-id=<id>
 ```
 
@@ -510,12 +520,14 @@ _See code: [src/commands/deploy/service-config.ts](https://github.com/powersync-
 
 ```
 USAGE
-  $ powersync deploy sync-config [--deploy-timeout <value>] [--directory <value>] [--instance-id <value>]
+  $ powersync deploy sync-config [--deploy-timeout <value>] [--dry-run] [--directory <value>] [--instance-id <value>]
     [--sync-config-file-path <value>] [--skip-validations <value> | ]
 
 FLAGS
   --deploy-timeout=<value>    [default: 300] Seconds to wait after scheduling a deploy before timing out while polling
                               status (default 300 seconds).
+  --dry-run                   Show the target instance, run the validations and print what would change, then exit
+                              without deploying.
   --skip-validations=<value>  Comma-separated list of validation tests to skip. Options: sync-config. Example:
                               --skip-validations="sync-config"
 
@@ -532,11 +544,14 @@ CLOUD_PROJECT FLAGS
 DESCRIPTION
   [Cloud only] Deploy only local sync config to the linked Cloud instance.
 
-  Deploy only sync config changes.
+  Deploy only sync config changes. Use --dry-run to show the target instance, the validation results and what would
+  change, without deploying.
 
 EXAMPLES
   $ powersync deploy sync-config
 
+  $ powersync deploy sync-config --dry-run
+
   $ powersync deploy sync-config --instance-id=<id>
 ```
 
@@ -842,7 +857,7 @@ DESCRIPTION
   Show instance diagnostics (connections, sync config, replication).
 
   Fetch instance diagnostics: connection status, active and deploying sync config, replication state. Output as
-  human-readable, JSON, or YAML. Cloud and self-hosted.
+  human-readable, JSON, or YAML. Human output starts with the target instance. Cloud and self-hosted.
 
 EXAMPLES
   $ powersync fetch status
@@ -1509,7 +1524,7 @@ DESCRIPTION
   Show instance diagnostics (connections, sync config, replication).
 
   Fetch instance diagnostics: connection status, active and deploying sync config, replication state. Output as
-  human-readable, JSON, or YAML. Cloud and self-hosted.
+  human-readable, JSON, or YAML. Human output starts with the target instance. Cloud and self-hosted.
 
 EXAMPLES
   $ powersync status

diff --git a/cli/package.json b/cli/package.json
@@ -26,6 +26,7 @@
     "@powersync/service-types": "catalog:",
     "@powersync/sync-config-tools": "^0.1.2",
     "bson": "^7.2.0",
+    "diff": "^8.0.4",
     "fastify": "^5.8.5",
     "jose": "^6.2.3",
     "lodash": "^4.18.1",

diff --git a/cli/src/api/BaseDeployCommand.ts b/cli/src/api/BaseDeployCommand.ts
@@ -9,6 +9,7 @@ import { routes } from '@powersync/management-types';
 import ora from 'ora';
 
 import { DEFAULT_DEPLOY_TIMEOUT_MS, waitForOperationStatusChange } from './cloud/wait-for-operation.js';
+import { changedServiceConfigSections, formatSyncConfigDiff } from './dry-run.js';
 import { parseLocalCloudServiceConfig } from './parse-local-cloud-service-config.js';
 
 export default abstract class BaseDeployCommand extends CloudInstanceCommand {
@@ -26,6 +27,11 @@ export default abstract class BaseDeployCommand extends CloudInstanceCommand {
         return value;
       }
     }),
+    'dry-run': Flags.boolean({
+      default: false,
+      description:
+        'Show the target instance, run the validations and print what would change, then exit without deploying.'
+    }),
     ...CloudInstanceCommand.baseFlags
   };
 
@@ -75,6 +81,22 @@ export default abstract class BaseDeployCommand extends CloudInstanceCommand {
     });
   }
 
+  protected describeServiceConfigChanges(cloudConfigState: routes.InstanceConfigResponse): string {
+    const summary = `would deploy ${SERVICE_FILENAME}.`;
+    if (!cloudConfigState.config) {
+      return `${summary} No config is deployed yet.`;
+    }
+
+    const sections = changedServiceConfigSections(this.serviceConfig!, cloudConfigState);
+    if (!sections) {
+      return `${summary} Could not compare with the deployed config.`;
+    }
+
+    return sections.length > 0
+      ? `${summary} Changes in: ${sections.join(', ')}.`
+      : `${summary} No changes compared to the deployed config.`;
+  }
+
   protected async loadCloudConfigState(): Promise<routes.InstanceConfigResponse> {
     const { client, project } = this;
     const { linked } = project;
@@ -92,6 +114,45 @@ export default abstract class BaseDeployCommand extends CloudInstanceCommand {
       });
   }
 
+  /**
+   * Ends a --dry-run once the target and validation results are shown: reports what a real run would deploy.
+   * Set provisionFirst when the instance is deprovisioned, since a real run would provision it before deploying.
+   */
+  protected logDryRun(params: {
+    cloudConfigState: routes.InstanceConfigResponse;
+    provisionFirst?: boolean;
+    /** Whether the command sends service.yaml. */
+    serviceConfig: boolean;
+    /** Whether the command sends the local sync config. */
+    syncConfig: boolean;
+  }): void {
+    const { cloudConfigState, provisionFirst = false, serviceConfig, syncConfig } = params;
+    const { syncRulesContent } = this.project;
+
+    this.log('');
+    if (provisionFirst) {
+      this.log(
+        `The instance is ${ux.colorize('yellow', 'not currently provisioned')}. Deploying would first provision it, then validate and deploy the sync config.`
+      );
+    }
+
+    this.log(ux.colorize('yellow', 'Dry run: nothing was deployed.'));
+    this.log(
+      `\tService config: ${serviceConfig ? this.describeServiceConfigChanges(cloudConfigState) : 'not changed by this command.'}`
+    );
+
+    if (!syncConfig) {
+      this.log('\tSync config: not changed by this command.');
+    } else if (syncRulesContent === cloudConfigState.sync_rules) {
+      this.log('\tSync config: matches the deployed sync config, nothing to update.');
+    } else {
+      this.log('\tSync config: would deploy the local sync config. Diff against the deployed sync config:');
+      for (const line of formatSyncConfigDiff(cloudConfigState.sync_rules ?? '', syncRulesContent ?? '')) {
+        this.log(`\t\t${line}`);
+      }
+    }
+  }
+
   override parseLocalConfig(projectDirectory: string, useRawConfig?: boolean): ServiceCloudConfigDecoded {
     const config = parseLocalCloudServiceConfig(projectDirectory, useRawConfig ?? false);
     if (!config) {
@@ -272,6 +333,21 @@ export default abstract class BaseDeployCommand extends CloudInstanceCommand {
     }
   }
 
+  /**
+   * Deploying sends the local service.yaml `name` as the instance name, so a deploy renames the
+   * instance if the two differ. Warn so users targeting several instances from one config notice.
+   */
+  protected warnIfDeployRenamesInstance(cloudConfigState: routes.InstanceConfigResponse): void {
+    const localName = this.serviceConfig?.name;
+    if (!localName || localName === cloudConfigState.name) {
+      return;
+    }
+
+    this.warn(
+      `Deploying will rename the instance from "${cloudConfigState.name}" to "${localName}" because ${SERVICE_FILENAME} has name: ${localName}.`
+    );
+  }
+
   protected async withDeploy(timeoutMs: number, fn: () => Promise<routes.DeployInstanceResponse>): Promise<void> {
     const { project } = this;
 

diff --git a/cli/src/api/dry-run.ts b/cli/src/api/dry-run.ts
@@ -0,0 +1,46 @@
+import { ux } from '@oclif/core';
+import { AdditionalCloudConfigFields, ServiceCloudConfigDecoded } from '@powersync/cli-schemas';
+import { routes } from '@powersync/management-types';
+import { structuredPatch } from 'diff';
+import isEqual from 'lodash/isEqual.js';
+
+import { decodeFetchedCloudConfig } from './cloud/fetch-cloud-config.js';
+
+const CLI_ONLY_FIELDS = new Set(Object.keys(AdditionalCloudConfigFields.props.shape));
+
+function colorizeDiffLine(line: string): string {
+  if (line.startsWith('+')) return ux.colorize('green', line);
+  if (line.startsWith('-')) return ux.colorize('red', line);
+  return line;
+}
+
+/**
+ * Names the top-level service config sections whose local value differs from the deployed one.
+ * Returns undefined when the deployed config cannot be decoded for comparison.
+ */
+export function changedServiceConfigSections(
+  localConfig: ServiceCloudConfigDecoded,
+  cloudConfigState: routes.InstanceConfigResponse
+): string[] | undefined {
+  let deployed: Record<string, unknown>;
+  try {
+    deployed = decodeFetchedCloudConfig(cloudConfigState).config as Record<string, unknown>;
+  } catch {
+    return undefined;
+  }
+
+  const local = localConfig as Record<string, unknown>;
+  const sections = new Set([...Object.keys(deployed), ...Object.keys(local)]);
+  return [...sections]
+    .filter((section) => !CLI_ONLY_FIELDS.has(section) && !isEqual(local[section], deployed[section]))
+    .sort();
+}
+
+/** Unified diff of the deployed sync config against the local one, one colorized entry per line. Empty when identical. */
+export function formatSyncConfigDiff(deployed: string, local: string): string[] {
+  const { hunks } = structuredPatch('deployed', 'local', deployed, local);
+  return hunks.flatMap((hunk) => [
+    ux.colorize('cyan', `@@ -${hunk.oldStart},${hunk.oldLines} +${hunk.newStart},${hunk.newLines} @@`),
+    ...hunk.lines.map((line) => colorizeDiffLine(line))
+  ]);
+}
diff --git a/cli/src/commands/compact.ts b/cli/src/commands/compact.ts
@@ -25,12 +25,13 @@ export default class Compact extends CloudInstanceCommand {
   async run(): Promise<void> {
     const { flags } = await this.parse(Compact);
     const { linked } = await this.loadProject(flags);
+    const instanceLabel = await this.logTargetInstance();
     const { client } = this;
     const timeoutMs = flags.timeout === 0 ? Number.POSITIVE_INFINITY : flags.timeout * 60 * 1000;
 
     const spinner = ora({
       discardStdin: false,
-      prefixText: `\n${ux.colorize('yellow', 'Compacting')} instance ${ux.colorize('blue', linked.instance_id)} in project ${ux.colorize('blue', linked.project_id)} in org ${ux.colorize('blue', linked.org_id)}\n`,
+      prefixText: `\n${ux.colorize('yellow', 'Compacting')} instance ${ux.colorize('blue', instanceLabel)} in project ${ux.colorize('blue', linked.project_id)} in org ${ux.colorize('blue', linked.org_id)}\n`,
       spinner: 'moon',
       suffixText: '\nThis may take a few minutes.\n'
     });

diff --git a/cli/src/commands/deploy/index.ts b/cli/src/commands/deploy/index.ts
@@ -14,9 +14,14 @@ export default class DeployAll extends WithSyncConfigFilePath(BaseDeployCommand)
     'Deploy local config (service.yaml, sync config) to the linked PowerSync Cloud instance.',
     'Validates connections and sync config before deploying.',
     `See also ${ux.colorize('blue', 'powersync deploy sync-config')} to deploy only sync config changes.`,
-    `See also ${ux.colorize('blue', 'powersync deploy service-config')} to deploy only service config changes.`
+    `See also ${ux.colorize('blue', 'powersync deploy service-config')} to deploy only service config changes.`,
+    'Use --dry-run to show the target instance, the validation results and what would change, without deploying.'
   ].join('\n');
-  static examples = ['<%= config.bin %> <%= command.id %>', '<%= config.bin %> <%= command.id %> --instance-id=<id>'];
+  static examples = [
+    '<%= config.bin %> <%= command.id %>',
+    '<%= config.bin %> <%= command.id %> --dry-run',
+    '<%= config.bin %> <%= command.id %> --instance-id=<id>'
+  ];
   static flags = {
     ...GENERAL_VALIDATION_FLAG_HELPERS.flags
   };
@@ -30,16 +35,19 @@ export default class DeployAll extends WithSyncConfigFilePath(BaseDeployCommand)
     });
 
     const deployTimeoutMs = (flags['deploy-timeout'] ?? DEFAULT_DEPLOY_TIMEOUT_MS / 1000) * 1000;
+    const dryRun = flags['dry-run'];
 
     const validationTestsFilter = GENERAL_VALIDATION_FLAG_HELPERS.parseValidationTestFlags(flags);
 
     const cloudConfigState = await this.loadCloudConfigState();
+    await this.logTargetInstance({ instanceName: cloudConfigState.name });
 
     // Parse and store for later
     this.parseLocalConfig(
       project.projectDirectory,
       validationTestsFilter.skipped.includes(ValidationTest.CONFIGURATION)
     );
+    this.warnIfDeployRenamesInstance(cloudConfigState);
 
     // Start of validations
     this.log('Performing validations before deploy...');
@@ -60,6 +68,7 @@ export default class DeployAll extends WithSyncConfigFilePath(BaseDeployCommand)
 
     const requiresReprovision = instanceStatus.provisioned === false;
     const syncConfigHasChanges = project.syncRulesContent !== cloudConfigState.sync_rules;
+    const dryRunSummary = { cloudConfigState, serviceConfig: true, syncConfig: true };
 
     let didReprovision = false;
 
@@ -90,6 +99,11 @@ export default class DeployAll extends WithSyncConfigFilePath(BaseDeployCommand)
         });
       }
 
+      if (dryRun) {
+        this.logDryRun({ ...dryRunSummary, provisionFirst: true });
+        return;
+      }
+
       /**
        * The non-sync-config validations passed. Reprovision now so that the instance is active
        * and we can validate the sync config against it in the second pass below.
@@ -139,6 +153,11 @@ export default class DeployAll extends WithSyncConfigFilePath(BaseDeployCommand)
       });
     }
 
+    if (dryRun) {
+      this.logDryRun(dryRunSummary);
+      return;
+    }
+
     await this.deployAll({ cloudConfigState, deployTimeoutMs, updateSyncConfig: syncConfigHasChanges });
   }
 }