diff --git a/.github/workflows/server-parity.yml b/.github/workflows/server-parity.yml
index c4bb53b6c..31788a264 100644
--- a/.github/workflows/server-parity.yml
+++ b/.github/workflows/server-parity.yml
@@ -377,6 +377,11 @@ jobs:
       - name: Bootstrap independent published PHP and native MySQL databases
         run: |
           set -euo pipefail
+          # Failed Rust tests are printed from their evidence files into this step's log.
+          rust_test_failures() {
+            bash scripts/conformance/server-parity/rust-test-failures.sh
+          }
+          trap rust_test_failures ERR
           mkdir -p cargo-home rust-target parity-evidence mysql-state
           chmod 0777 parity-evidence
           docker network create "$RESOURCE_SCOPE"
@@ -856,6 +861,11 @@ jobs:
           POSTGRES_IMAGE: ${{ matrix.image }}
         run: |
           set -euo pipefail
+          # Failed Rust tests are printed from their evidence files into this step's log.
+          rust_test_failures() {
+            bash scripts/conformance/server-parity/rust-test-failures.sh
+          }
+          trap rust_test_failures ERR
           mkdir -p cargo-home rust-target parity-evidence pg-state
           chmod 0777 parity-evidence
           docker network create "$RESOURCE_SCOPE"
@@ -1364,6 +1374,11 @@ jobs:
       - name: Execute official Rust codec and cross-decode with published PHP
         run: |
           set -euo pipefail
+          # Failed Rust tests are printed from their evidence files into this step's log.
+          rust_test_failures() {
+            bash scripts/conformance/server-parity/rust-test-failures.sh
+          }
+          trap rust_test_failures ERR
           mkdir -p cargo-home rust-target parity-evidence
           # Compiling the library tests peaks near 2.5 GB; a 2 GB limit OOM-killed rustc (exit 101).
           docker run --rm --user="$(id -u):$(id -g)" --cpus=2 --memory=4g --memory-swap=4g \
diff --git a/scripts/conformance/server-parity/admission-probe.php b/scripts/conformance/server-parity/admission-probe.php
index 0e681a1db..337bd9564 100644
--- a/scripts/conformance/server-parity/admission-probe.php
+++ b/scripts/conformance/server-parity/admission-probe.php
@@ -8,6 +8,7 @@
 use Workflow\V2\StartOptions;
 use Workflow\V2\WorkflowStub;
 use Workflow\WorkflowOptions;
+require_once __DIR__.'/lock-pressure-middleware.php';
 
 function parityAdmissionToken(string $auth): string
 {
@@ -86,7 +87,7 @@ function finishHttpAdmission(Client $client, array $fixture, string $workflowId,
         throw $error;
     } finally {
         if (isset($definition['cleanup_auth'])) {
-            $cleanupClient = new Client($url, namespace: $namespace, token: parityAdmissionToken($definition['cleanup_auth']));
+            $cleanupClient = parityClient($url, namespace: $namespace, token: parityAdmissionToken($definition['cleanup_auth']));
             $state['cleanup_auth'] = $definition['cleanup_auth'];
             $state['cleanup'] = $cleanupClient->cancelWorkflow($peerId, $definition['cleanup_reason'], $peer->selectedRunId);
         } else {
diff --git a/scripts/conformance/server-parity/cancellation-probe.php b/scripts/conformance/server-parity/cancellation-probe.php
index 0292c6abc..98f31d054 100644
--- a/scripts/conformance/server-parity/cancellation-probe.php
+++ b/scripts/conformance/server-parity/cancellation-probe.php
@@ -17,6 +17,7 @@
 use Workflow\V2\WorkflowStub;
 use Workflow\V2\StartOptions;
 use Workflow\WorkflowOptions;
+require_once __DIR__.'/lock-pressure-middleware.php';
 
 // Application callbacks use only the published APIs. These observations never
 // mutate engine rows or synthesize a claim, cancellation or terminal outcome.
@@ -40,7 +41,7 @@ function cancellationReceipt(callable $submit): array
 function httpCancellationObservation(array $fixture, string $workflowId, string $namespace, string $queue, string $url): array
 {
     $polls = $completions = $activityPolls = $activityOutcomes = [];
-    $client = new Client($url, namespace: $namespace, token: getenv('DW_PARITY_TOKEN') ?: null,
+    $client = parityClient($url, namespace: $namespace, token: getenv('DW_PARITY_TOKEN') ?: null,
         transport: observedChildTransport($polls, $completions, $activityPolls, $activityOutcomes));
     $phase = $fixture['immediate_cancellation']['phase'];
     $reason = $fixture['immediate_cancellation']['reason'];
@@ -113,7 +114,7 @@ function httpCancellationObservation(array $fixture, string $workflowId, string
             $task['activity_attempt_id'], $task['lease_owner'], $fixture['input']));
     }
     // A separate published Client reloads the same durable run and history.
-    $fresh = new Client($url, namespace: $namespace, token: getenv('DW_PARITY_TOKEN') ?: null);
+    $fresh = parityClient($url, namespace: $namespace, token: getenv('DW_PARITY_TOKEN') ?: null);
     $inspectionWorker = $workflowId.':inspection';
     $fresh->registerWorker($inspectionWorker, $queue, [$fixture['workflow_type']], ['parity.v1.cancel_activity']);
     $remaining = ['workflow' => $fresh->pollWorkflowTask($inspectionWorker, $queue, 0),
diff --git a/scripts/conformance/server-parity/child-cancellation-probe.php b/scripts/conformance/server-parity/child-cancellation-probe.php
index b548be1bb..7b8ee4449 100644
--- a/scripts/conformance/server-parity/child-cancellation-probe.php
+++ b/scripts/conformance/server-parity/child-cancellation-probe.php
@@ -5,6 +5,7 @@
 use DurableWorkflow\Client;
 use Workflow\V2\Models\WorkflowRun;
 use Workflow\V2\WorkflowStub;
+require_once __DIR__.'/lock-pressure-middleware.php';
 
 final class ChildCancellationProbeState
 {
@@ -54,7 +55,7 @@ function finishHttpChildCancellation(Client $client, string $parentId, string $p
     $state['terminal_duplicate'] = cancellationReceipt(static fn (): array => $client->cancelWorkflow($id, 'post-parent-completion replacement', $runId));
     $state['child_history_after_terminal_duplicate'] = httpHistory($client, $id, $runId);
     $state['parent_history_after_terminal_duplicate'] = httpHistory($client, $parentId, $parentRunId);
-    $fresh = new Client($url, namespace: $namespace, token: getenv('DW_PARITY_TOKEN') ?: null);
+    $fresh = parityClient($url, namespace: $namespace, token: getenv('DW_PARITY_TOKEN') ?: null);
     $state['fresh_child'] = $fresh->describeWorkflow($id, $runId)->raw;
     $state['fresh_child_history'] = httpHistory($fresh, $id, $runId);
     $state['fresh_parent'] = $fresh->describeWorkflow($parentId, $parentRunId)->raw;
diff --git a/scripts/conformance/server-parity/cooperative-probe.php b/scripts/conformance/server-parity/cooperative-probe.php
index cb2e19d83..3a52e3ee4 100644
--- a/scripts/conformance/server-parity/cooperative-probe.php
+++ b/scripts/conformance/server-parity/cooperative-probe.php
@@ -21,6 +21,7 @@
 use Workflow\V2\WorkflowStub;
 use Workflow\V2\StartOptions;
 use Workflow\WorkflowOptions;
+require_once __DIR__.'/lock-pressure-middleware.php';
 
 function cooperativeObservedTransport(array &$traffic): Psr18Transport
 {
@@ -42,6 +43,7 @@ function cooperativeObservedTransport(array &$traffic): Psr18Transport
             });
         };
     });
+    $stack->push(LockPressurePollRetries::middleware(), 'lock_pressure_poll_retry');
 
     return new Psr18Transport(client: new GuzzleClient(['http_errors' => false, 'handler' => $stack]));
 }
@@ -75,7 +77,7 @@ function httpCooperativeObservation(array $fixture, string $workflowId, string $
 {
     $traffic = [];
     $diagnostics = [];
-    $client = new Client($url, namespace: $namespace, token: getenv('DW_PARITY_TOKEN') ?: null,
+    $client = parityClient($url, namespace: $namespace, token: getenv('DW_PARITY_TOKEN') ?: null,
         transport: cooperativeObservedTransport($traffic), workerProtocolVersion: '1.20');
     $phase = $fixture['cooperative_cancellation']['phase'];
     $reason = $fixture['cooperative_cancellation']['reason'];
@@ -150,7 +152,7 @@ static function (string $event, array $details) use (&$handle, &$diagnostics, $c
     } catch (WorkflowCancelled $error) {
         $outcome = ['type' => $error::class, 'message' => $error->getMessage()];
     }
-    $fresh = new Client($url, namespace: $namespace, token: getenv('DW_PARITY_TOKEN') ?: null, workerProtocolVersion: '1.20');
+    $fresh = parityClient($url, namespace: $namespace, token: getenv('DW_PARITY_TOKEN') ?: null, workerProtocolVersion: '1.20');
 
     return ['execution' => $execution->raw, 'workflow_id' => $execution->workflowId, 'run_id' => $execution->runId,
         'workflow_type' => $execution->workflowType, 'namespace' => $execution->namespace, 'task_queue' => $execution->taskQueue,
diff --git a/scripts/conformance/server-parity/cooperative-restart.php b/scripts/conformance/server-parity/cooperative-restart.php
index 6fd9950b3..2e4b81d3b 100644
--- a/scripts/conformance/server-parity/cooperative-restart.php
+++ b/scripts/conformance/server-parity/cooperative-restart.php
@@ -8,6 +8,7 @@
 use DurableWorkflow\Worker\CancellationDelivery;
 
 require __DIR__.'/vendor/autoload.php';
+require_once __DIR__.'/lock-pressure-middleware.php';
 require __DIR__.'/observation-values.php';
 require __DIR__.'/cooperative-probe.php';
 
@@ -56,7 +57,7 @@ function cooperativeEvent(array $events, string $type): array
         $workflowId = 'root-restart-'.$outcome;
         $queue = 'root-restart-'.$outcome;
         $traffic = [];
-        $client = new Client($url, namespace: 'default', token: getenv('DW_PARITY_TOKEN') ?: null,
+        $client = parityClient($url, namespace: 'default', token: getenv('DW_PARITY_TOKEN') ?: null,
             transport: cooperativeObservedTransport($traffic), workerProtocolVersion: '1.20');
         $worker = $handle = $accepted = null;
         $guard = microtime(true) + 20;
@@ -118,7 +119,7 @@ static function (string $event) use (&$handle, $client, $fixture, $workflowId, $
 foreach (['deadline_expired', 'completed'] as $outcome) {
     $receipt = $receipts[$outcome];
     $traffic = [];
-    $client = new Client($url, namespace: 'default', token: getenv('DW_PARITY_TOKEN') ?: null,
+    $client = parityClient($url, namespace: 'default', token: getenv('DW_PARITY_TOKEN') ?: null,
         transport: cooperativeObservedTransport($traffic), workerProtocolVersion: '1.20');
     $handle = $client->workflowHandle($receipt['workflow_id'], $receipt['run_id']);
     $before = httpHistory($client, $receipt['workflow_id'], $receipt['run_id']);
@@ -188,7 +189,7 @@ static function () use (&$worker, $handle, $guard): float {
     }
     $duplicate = $client->requestWorkflowCancellation($receipt['workflow_id'], 'post-terminal replacement', 3600, $receipt['run_id']);
     assertCooperativeRecovery($duplicate['duplicate'] === true && $duplicate['cancellation_request']['cleanup_deadline_at'] === $receipt['context']['cleanup_deadline_at'], 'Terminal duplicate changed the original budget.');
-    $fresh = new Client($url, namespace: 'default', token: getenv('DW_PARITY_TOKEN') ?: null, workerProtocolVersion: '1.20');
+    $fresh = parityClient($url, namespace: 'default', token: getenv('DW_PARITY_TOKEN') ?: null, workerProtocolVersion: '1.20');
     assertCooperativeRecovery(sameCooperativeValue($events, httpHistory($fresh, $receipt['workflow_id'], $receipt['run_id'])), 'Late calls or fresh reads changed terminal history.');
     try {
         $fresh->workflowHandle($receipt['workflow_id'], $receipt['run_id'])->resultOfSelectedRun(1);
diff --git a/scripts/conformance/server-parity/corrected-markers/rust/src/lock_pressure.rs b/scripts/conformance/server-parity/corrected-markers/rust/src/lock_pressure.rs
new file mode 100644
index 000000000..5f9f9f9b9
--- /dev/null
+++ b/scripts/conformance/server-parity/corrected-markers/rust/src/lock_pressure.rs
@@ -0,0 +1,94 @@
+//! The published PHP SQLite reference can refuse a worker operation with its
+//! documented HTTP 503 `backend_lock_pressure` reply and `retryable: true`
+//! after its transaction failed, so nothing was committed. Only that refusal is
+//! retried, within 15 retries and 30 seconds of waiting, as the PHP probes'
+//! transport does (`../lock-pressure-retry.php`). Every other outcome is
+//! returned unchanged.
+use durable_workflow::{Error, Result};
+use serde_json::Value;
+use std::{future::Future, time::Duration};
+
+const MAX_RETRIES: u32 = 15;
+const MAX_WAIT: Duration = Duration::from_secs(30);
+
+fn delay_for(status: u16, body: &str, retries: u32, waited: Duration) -> Option<Duration> {
+    if status != 503 || retries >= MAX_RETRIES {
+        return None;
+    }
+    let body: Value = serde_json::from_str(body).ok()?;
+    if body.get("reason")?.as_str()? != "backend_lock_pressure"
+        || body.get("retryable") != Some(&Value::Bool(true))
+    {
+        return None;
+    }
+    let seconds = match body.get("retry_after_seconds") {
+        None => 1.0,
+        Some(value) => value.as_f64()?,
+    };
+    let delay = Duration::from_secs_f64(seconds.clamp(0.1, 5.0));
+    (waited + delay <= MAX_WAIT).then_some(delay)
+}
+
+/// Runs `call`, repeating it only after the documented lock-pressure refusal.
+pub async fn retrying<T, F, Fut>(what: &str, mut call: F) -> Result<T>
+where
+    F: FnMut() -> Fut,
+    Fut: Future<Output = Result<T>>,
+{
+    let (mut retries, mut waited) = (0, Duration::ZERO);
+    loop {
+        let error = match call().await {
+            Err(error) => error,
+            done => return done,
+        };
+        let delay = match &error {
+            Error::Http { status, body } => delay_for(status.as_u16(), body, retries, waited),
+            _ => None,
+        };
+        let Some(delay) = delay else {
+            return Err(error);
+        };
+        eprintln!("{what}: retrying backend_lock_pressure refusal after {delay:?}");
+        tokio::time::sleep(delay).await;
+        waited += delay;
+        retries += 1;
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const REFUSAL: &str = r#"{"reason":"backend_lock_pressure","operation":"destroy","outcome":"deferred","retryable":true,"retry_after_seconds":1}"#;
+
+    #[test]
+    fn documented_refusal_waits_for_the_advertised_interval() {
+        assert_eq!(delay_for(503, REFUSAL, 0, Duration::ZERO), Some(Duration::from_secs(1)));
+        let long = REFUSAL.replace(r#""retry_after_seconds":1"#, r#""retry_after_seconds":60"#);
+        assert_eq!(delay_for(503, &long, 0, Duration::ZERO), Some(Duration::from_secs(5)));
+        let absent = REFUSAL.replace(r#","retry_after_seconds":1"#, "");
+        assert_eq!(delay_for(503, &absent, 0, Duration::ZERO), Some(Duration::from_secs(1)));
+    }
+
+    #[test]
+    fn other_statuses_reasons_and_bodies_are_returned() {
+        for (status, body) in [
+            (409, REFUSAL.to_owned()),
+            (500, REFUSAL.to_owned()),
+            (503, REFUSAL.replace("backend_lock_pressure", "backend_unavailable")),
+            (503, REFUSAL.replace(r#""retryable":true"#, r#""retryable":false"#)),
+            (503, REFUSAL.replace(r#","retryable":true"#, "")),
+            (503, REFUSAL.replace(r#""retry_after_seconds":1"#, r#""retry_after_seconds":"soon""#)),
+            (503, "not json".to_owned()),
+        ] {
+            assert_eq!(delay_for(status, &body, 0, Duration::ZERO), None, "{status} {body}");
+        }
+    }
+
+    #[test]
+    fn retries_stop_at_the_attempt_and_wait_budgets() {
+        assert_eq!(delay_for(503, REFUSAL, 15, Duration::ZERO), None);
+        assert_eq!(delay_for(503, REFUSAL, 2, Duration::from_millis(29_500)), None);
+        assert_eq!(delay_for(503, REFUSAL, 14, Duration::from_secs(29)), Some(Duration::from_secs(1)));
+    }
+}
diff --git a/scripts/conformance/server-parity/corrected-markers/rust/src/main.rs b/scripts/conformance/server-parity/corrected-markers/rust/src/main.rs
index c5f7bdb7d..3a1d863c7 100644
--- a/scripts/conformance/server-parity/corrected-markers/rust/src/main.rs
+++ b/scripts/conformance/server-parity/corrected-markers/rust/src/main.rs
@@ -11,6 +11,7 @@ use durable_workflow::{
 use serde_json::{json, Value};
 
 mod legacy_range;
+mod lock_pressure;
 mod memo_author;
 
 const WORKFLOW: &str = "parity.v1.corrected_markers";
@@ -221,7 +222,10 @@ async fn main() -> Result<()> {
         }
     })
     .await;
-    let deregistered = client.deregister_worker_registration(&worker_id).await;
+    let deregistered = lock_pressure::retrying("deregister", || {
+        client.deregister_worker_registration(&worker_id)
+    })
+    .await;
     let result = match outcome {
         Ok(result) => result,
         Err(_) => Err(Error::WorkerLoop(
diff --git a/scripts/conformance/server-parity/corrected-markers/rust/src/memo_author.rs b/scripts/conformance/server-parity/corrected-markers/rust/src/memo_author.rs
index 8520ac901..d2c4c04c2 100644
--- a/scripts/conformance/server-parity/corrected-markers/rust/src/memo_author.rs
+++ b/scripts/conformance/server-parity/corrected-markers/rust/src/memo_author.rs
@@ -90,7 +90,10 @@ pub async fn run(args: &[String]) -> Result<()> {
     })
     .await
     .map_err(|_| Error::WorkerLoop("Original memo phase observation expired".into()))?;
-    let retired = client.deregister_worker_registration(&worker_id).await;
+    let retired = super::lock_pressure::retrying("deregister", || {
+        client.deregister_worker_registration(&worker_id)
+    })
+    .await;
     outcome?;
     retired?;
     println!(
diff --git a/scripts/conformance/server-parity/lock-pressure-middleware.php b/scripts/conformance/server-parity/lock-pressure-middleware.php
new file mode 100644
index 000000000..1ced25c8d
--- /dev/null
+++ b/scripts/conformance/server-parity/lock-pressure-middleware.php
@@ -0,0 +1,97 @@
+<?php
+
+declare(strict_types=1);
+
+use DurableWorkflow\Client;
+use DurableWorkflow\Transport\Psr18Transport;
+use GuzzleHttp\Client as GuzzleClient;
+use GuzzleHttp\HandlerStack;
+use GuzzleHttp\Promise\Create;
+use GuzzleHttp\Psr7\Utils;
+use Psr\Http\Message\RequestInterface;
+use Psr\Http\Message\ResponseInterface;
+
+require_once __DIR__.'/lock-pressure-retry.php';
+
+/**
+ * The published PHP SQLite reference shares its file with its maintenance loop
+ * and may refuse a request with the documented 503 backend_lock_pressure reply
+ * (see lockPressureOperationRetryDelay and lockPressurePollRetryDelay for the
+ * exact conditions). This Guzzle middleware retries only that refusal, below the SDK transport, so
+ * the transport keeps every capability the SDK checks (bounded requests,
+ * payload transfer). It stops within the request's own timeout. Push it after
+ * any recording middleware (HandlerStack::push), which makes it innermost:
+ * Guzzle wraps the stack in reverse, so unshift would put it outermost and let
+ * recorders see each refused attempt. Recorders then see only the final reply
+ * and observations stay comparable across targets. Retries are reported
+ * once on stderr when the process exits.
+ */
+final class LockPressurePollRetries
+{
+    /** @var list<array{path: string, retry_after_seconds: float}> */
+    public static array $retries = [];
+    private static bool $reporting = false;
+
+    public static function middleware(): callable
+    {
+        if (!self::$reporting) {
+            self::$reporting = true;
+            register_shutdown_function(static function (): void {
+                if (self::$retries !== []) {
+                    fwrite(STDERR, json_encode(['lock_pressure_poll_retries' => self::$retries], JSON_THROW_ON_ERROR).PHP_EOL);
+                }
+            });
+        }
+
+        return static fn (callable $handler): callable => static function (RequestInterface $request, array $options) use ($handler) {
+            $started = microtime(true);
+            $budget = (float) ($options['timeout'] ?? 0);
+            $waited = 0.0;
+            $count = 0;
+            while (true) {
+                try {
+                    $response = $handler($request, $options)->wait();
+                } catch (\Throwable $error) {
+                    return Create::rejectionFor($error);
+                }
+                // A request body that cannot be replayed exactly is never retried.
+                if (!$response instanceof ResponseInterface || $response->getStatusCode() !== 503
+                    || (!$request->getBody()->isSeekable() && $request->getBody()->getSize() !== 0)) {
+                    return Create::promiseFor($response);
+                }
+                $text = (string) $response->getBody();
+                $response = $response->withBody(Utils::streamFor($text));
+                $decoded = json_decode($text, true);
+                $delay = lockPressureOperationRetryDelay($request->getMethod(), (string) $request->getUri(), 503,
+                    is_array($decoded) ? $decoded : null, $count, $waited);
+                if ($delay === null || ($budget > 0 && microtime(true) - $started + $delay >= $budget)) {
+                    return Create::promiseFor($response);
+                }
+                self::$retries[] = ['path' => $request->getUri()->getPath(), 'retry_after_seconds' => $delay];
+                usleep((int) round($delay * 1_000_000));
+                $waited += $delay;
+                $count++;
+                if ($request->getBody()->isSeekable()) {
+                    $request->getBody()->rewind();
+                }
+            }
+        };
+    }
+
+    /** The SDK's default transport, with this retry innermost. */
+    public static function transport(): Psr18Transport
+    {
+        $stack = HandlerStack::create();
+        $stack->push(self::middleware(), 'lock_pressure_poll_retry');
+
+        return new Psr18Transport(client: new GuzzleClient(['http_errors' => false, 'handler' => $stack]));
+    }
+}
+
+/** An SDK client for a parity probe. A caller-supplied transport is used unchanged. */
+function parityClient(mixed ...$arguments): Client
+{
+    $arguments['transport'] ??= LockPressurePollRetries::transport();
+
+    return new Client(...$arguments);
+}
diff --git a/scripts/conformance/server-parity/lock-pressure-retry.php b/scripts/conformance/server-parity/lock-pressure-retry.php
index fa7c28af4..112299d78 100644
--- a/scripts/conformance/server-parity/lock-pressure-retry.php
+++ b/scripts/conformance/server-parity/lock-pressure-retry.php
@@ -38,3 +38,45 @@ function lockPressurePollRetryDelay(
 
     return $waitedSeconds + $delay <= $maxWaitSeconds ? $delay : null;
 }
+
+/**
+ * Decide whether any other request refused for backend lock pressure may be
+ * retried.
+ *
+ * Server returns this refusal as HTTP 503 with `reason: backend_lock_pressure`
+ * and `retryable: true` only after its transaction failed with a concurrency
+ * error, so nothing was committed. Worker mutations remain fenced by their
+ * task and attempt identifiers (`outcome: deferred`), so repeating the request
+ * cannot record a second outcome. Polls keep lockPressurePollRetryDelay's
+ * stricter check that no task was handed out.
+ *
+ * Returns the delay in seconds before the next attempt, or null to return the
+ * refusal to the caller unchanged.
+ */
+function lockPressureOperationRetryDelay(
+    string $method,
+    string $uri,
+    ?int $status,
+    mixed $response,
+    int $retriesSoFar,
+    float $waitedSeconds,
+    int $maxRetries = 15,
+    float $maxWaitSeconds = 30.0,
+): ?float {
+    $path = parse_url($uri, PHP_URL_PATH);
+    if (! is_string($path) || str_ends_with($path, '/poll')) {
+        return lockPressurePollRetryDelay($method, $uri, $status, $response, $retriesSoFar, $waitedSeconds,
+            $maxRetries, $maxWaitSeconds);
+    }
+    if ($status !== 503 || ! is_array($response) || ($response['reason'] ?? null) !== 'backend_lock_pressure'
+        || ($response['retryable'] ?? null) !== true || $retriesSoFar >= $maxRetries) {
+        return null;
+    }
+    $retryAfter = $response['retry_after_seconds'] ?? 1;
+    if (! is_int($retryAfter) && ! is_float($retryAfter)) {
+        return null;
+    }
+    $delay = min(max((float) $retryAfter, 0.1), 5.0);
+
+    return $waitedSeconds + $delay <= $maxWaitSeconds ? $delay : null;
+}
diff --git a/scripts/conformance/server-parity/namespace-probe.php b/scripts/conformance/server-parity/namespace-probe.php
index 7422ec260..f6d1e0fa1 100644
--- a/scripts/conformance/server-parity/namespace-probe.php
+++ b/scripts/conformance/server-parity/namespace-probe.php
@@ -20,6 +20,7 @@
 use Workflow\V2\WorkflowStub;
 use Workflow\WorkflowOptions;
 use Workflow\Serializers\Serializer;
+require_once __DIR__.'/lock-pressure-middleware.php';
 
 function namespaceReceipt(string $id, callable $request): array
 {
@@ -66,6 +67,7 @@ function namespaceTransport(array &$receipts, ?Closure $beforeCompletion = null)
             });
         };
     });
+    $stack->push(LockPressurePollRetries::middleware(), 'lock_pressure_poll_retry');
 
     return new Psr18Transport(client: new NamespaceHttp(['http_errors' => false, 'handler' => $stack,
         'connect_timeout' => 1, 'timeout' => 5]));
@@ -98,7 +100,7 @@ function finishHttpNamespaces(Client $admin, array $fixture, string $workflowId,
             'before' => $before, 'after' => namespaceHttpRun($clients[0], $ids[0], $handles[0]->selectedRunId)];
     };
     foreach ($names as $index => $name) {
-        $clients[] = new Client($url, namespace: $name, token: getenv('DW_PARITY_TOKEN') ?: null,
+        $clients[] = parityClient($url, namespace: $name, token: getenv('DW_PARITY_TOKEN') ?: null,
             transport: namespaceTransport($state['worker_receipts'][$index], $index === 0 ? $beforeCompletion : null));
         $state['registrations'][] = $clients[$index]->registerWorker($state['worker_id'], $queue,
             [$definition['peer_workflow_type']], ['parity.v1.echo_activity']);
diff --git a/scripts/conformance/server-parity/patch-deployment-probe.php b/scripts/conformance/server-parity/patch-deployment-probe.php
index 032944130..030b34773 100644
--- a/scripts/conformance/server-parity/patch-deployment-probe.php
+++ b/scripts/conformance/server-parity/patch-deployment-probe.php
@@ -20,6 +20,7 @@
 use Workflow\V2\StartOptions;
 use Workflow\V2\WorkflowStub;
 use Workflow\WorkflowOptions;
+require_once __DIR__.'/lock-pressure-middleware.php';
 
 final class PatchDeploymentState
 {
@@ -126,7 +127,8 @@ function patchHttpPhase(array $fixture, array $options): array
             });
         };
     });
-    $client = new Client($options['url'], namespace: 'default', token: getenv('DW_PARITY_TOKEN') ?: null,
+    $stack->push(LockPressurePollRetries::middleware(), 'lock_pressure_poll_retry');
+    $client = parityClient($options['url'], namespace: 'default', token: getenv('DW_PARITY_TOKEN') ?: null,
         transport: new Psr18Transport(client: new GuzzleClient(['http_errors' => false, 'handler' => $stack])));
     if ($phase === 'replacement') {
         $handle = $client->workflowHandle($workflowId, $options['run-id']);
@@ -279,7 +281,7 @@ function patchPublishedSdkPhase(array $fixture, array $options): array
         if ($result['language'] !== $consumer['language'] || $result['sdk_version'] !== $consumer['version']) {
             throw new RuntimeException('Actual published worker differs from the selected consumer.');
         }
-        $client = new Client($options['url'], namespace: 'default', token: getenv('DW_PARITY_TOKEN') ?: null);
+        $client = parityClient($options['url'], namespace: 'default', token: getenv('DW_PARITY_TOKEN') ?: null);
         $runId = $original ? ($result['run_id'] ?? null) : $options['run-id'];
         if (! is_string($runId) || $runId === '') {
             throw new RuntimeException('Actual published author returned no original run identity.');
diff --git a/scripts/conformance/server-parity/probe.php b/scripts/conformance/server-parity/probe.php
index d63bc0f8d..060d26745 100644
--- a/scripts/conformance/server-parity/probe.php
+++ b/scripts/conformance/server-parity/probe.php
@@ -64,6 +64,7 @@
 
 require __DIR__.'/observation-values.php';
 require __DIR__.'/probe-failure.php';
+require_once __DIR__.'/lock-pressure-middleware.php';
 
 function observedChildTransport(array &$polls, array &$completions, array &$activityPolls, array &$activityOutcomes, ?Closure $afterCompletion = null, ?array &$scheduleReceipts = null): Psr18Transport
 {
@@ -106,6 +107,7 @@ function observedChildTransport(array &$polls, array &$completions, array &$acti
             });
         };
     });
+    $stack->push(LockPressurePollRetries::middleware(), 'lock_pressure_poll_retry');
 
     return new Psr18Transport(client: new GuzzleClient(['http_errors' => false, 'handler' => $stack]));
 }
@@ -114,7 +116,7 @@ function observedChildTransport(array &$polls, array &$completions, array &$acti
 // client in an independent PHP process so this probe's worker keeps polling.
 if ($mode === 'query') {
     try {
-        $client = new Client($options['url'], namespace: $namespace, token: getenv('DW_PARITY_TOKEN') ?: null);
+        $client = parityClient($options['url'], namespace: $namespace, token: getenv('DW_PARITY_TOKEN') ?: null);
         $result = $client->queryWorkflow($workflowId, $fixture['query_name'], $fixture['query_arguments'], $options['run-id']);
         echo json_encode(['result' => $result, 'typed_result' => typedValue($result)], JSON_THROW_ON_ERROR | JSON_UNESCAPED_UNICODE)."\n";
         exit(0);
@@ -142,9 +144,9 @@ function httpObservation(array $fixture, string $workflowId, string $namespace,
     } : null;
     $transport = isset($fixture['child_count']) || isset($fixture['child_cancellation']) || isset($fixture['retry_policy']) || isset($fixture['schedule'])
         ? observedChildTransport($workflowPolls, $workflowCompletions, $activityPolls, $activityOutcomes, $afterCompletion, $scheduleReceipts) : null;
-    $client = new Client($url, namespace: $namespace, transport: $transport, token: getenv('DW_PARITY_TOKEN') ?: null);
+    $client = parityClient($url, namespace: $namespace, transport: $transport, token: getenv('DW_PARITY_TOKEN') ?: null);
     $workerClient = ($fixture['auth_profile'] ?? null) === 'role_tokens'
-        ? new Client($url, namespace: $namespace, token: parityAdmissionToken('worker')) : $client;
+        ? parityClient($url, namespace: $namespace, token: parityAdmissionToken('worker')) : $client;
     $handle = null;
     $deliveries = [];
     $queries = [];
diff --git a/scripts/conformance/server-parity/rust-test-failures.sh b/scripts/conformance/server-parity/rust-test-failures.sh
new file mode 100755
index 000000000..6e83f9e9c
--- /dev/null
+++ b/scripts/conformance/server-parity/rust-test-failures.sh
@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+# Print the failures in this job's Rust test output, so a failed test step is
+# diagnosable from its own log. Reads parity-evidence; changes nothing.
+set -uo pipefail
+for output in parity-evidence/*tests*.txt; do
+  [[ -f $output ]] && grep -q '^test result: FAILED' "$output" || continue
+  echo "::group::Rust test failures in ${output#parity-evidence/}"
+  grep -E -A3 'panicked at' "$output" | cut -c1-600 | head -n 120
+  # The closing summary names every failed test.
+  sed -n '/^failures:$/,$p' "$output" | grep -E '^failures:$|^    [A-Za-z0-9_:]+$|^test result:' | tail -n 60
+  echo "::endgroup::"
+done
+exit 0
diff --git a/scripts/conformance/server-parity/sdk-direction-probe.php b/scripts/conformance/server-parity/sdk-direction-probe.php
index b7fa2df5d..1a582e4a8 100644
--- a/scripts/conformance/server-parity/sdk-direction-probe.php
+++ b/scripts/conformance/server-parity/sdk-direction-probe.php
@@ -5,6 +5,7 @@
 use DurableWorkflow\Client;
 use DurableWorkflow\Worker;
 use DurableWorkflow\Worker\WorkflowContext;
+require_once __DIR__.'/lock-pressure-middleware.php';
 
 function sdkDirectionResponseSummary(mixed $response, bool $workflowHistory = false): mixed
 {
@@ -73,7 +74,7 @@ function sdkDirectionHttpObservation(array $fixture, array $options, ?Closure $a
     $spec = $fixture[$directionKey];
     $childWorkflowId = $childRunId = '';
     $namespace = $fixture['namespace'] ?? 'default';
-    $client = new Client($options['url'], namespace: $namespace, token: getenv('DW_PARITY_TOKEN') ?: null);
+    $client = parityClient($options['url'], namespace: $namespace, token: getenv('DW_PARITY_TOKEN') ?: null);
     $deadline = $scenarioDeadline ?? microtime(true) + 35;
     $observerStart = null;
     try {
@@ -81,7 +82,7 @@ function sdkDirectionHttpObservation(array $fixture, array $options, ?Closure $a
         if (! preg_match('#^http://127\\.0\\.0\\.1:[0-9]+$#', $url)) {
             throw new RuntimeException('SDK observer did not bind its local port.');
         }
-        $startClient = $signalDirection ? new Client($url, namespace: $namespace, token: getenv('DW_PARITY_TOKEN') ?: null) : null;
+        $startClient = $signalDirection ? parityClient($url, namespace: $namespace, token: getenv('DW_PARITY_TOKEN') ?: null) : null;
         foreach ($spec['phase_order'] as $phase) {
             $language = $signalDirection ? $spec[in_array($phase, ['signal-1', 'signal-2'], true) ? 'client' : 'workflow']
                 : ($timerAuthor ? $spec['language'] : ($childDirection ? $spec[$phase === 'child' ? 'child' : 'parent']
diff --git a/scripts/conformance/server-parity/sdk-namespace-signal-probe.php b/scripts/conformance/server-parity/sdk-namespace-signal-probe.php
index 082f7364a..1f7e411d5 100644
--- a/scripts/conformance/server-parity/sdk-namespace-signal-probe.php
+++ b/scripts/conformance/server-parity/sdk-namespace-signal-probe.php
@@ -11,6 +11,7 @@
 use Workflow\V2\StartOptions;
 use Workflow\V2\WorkflowStub;
 use Workflow\WorkflowOptions;
+require_once __DIR__.'/lock-pressure-middleware.php';
 
 function namespaceSignalRunFixture(array $fixture, bool $peer): array
 {
@@ -158,7 +159,7 @@ function namespaceSignalHttpObservation(array $fixture, array $options): array
             throw new RuntimeException('Namespace control observer did not bind its local port.');
         }
         $checkpoint('client_setup');
-        $admin = new Client($url, namespace: 'default', token: getenv('DW_PARITY_TOKEN') ?: null);
+        $admin = parityClient($url, namespace: 'default', token: getenv('DW_PARITY_TOKEN') ?: null);
         foreach ($fixtures as $index => $runFixture) {
             try {
                 $checkpoint('namespace_describe', $runFixture['namespace']);
@@ -175,7 +176,7 @@ function namespaceSignalHttpObservation(array $fixture, array $options): array
             $state['administration'][] = ['created' => $created, 'namespace' => $namespace->raw];
             $paths[$index] = tempnam(sys_get_temp_dir(), 'parity-namespace-fixture-');
             file_put_contents($paths[$index], json_encode($runFixture, JSON_THROW_ON_ERROR | JSON_UNESCAPED_UNICODE));
-            $clients[$index] = new Client($options['url'], namespace: $runFixture['namespace'], token: getenv('DW_PARITY_TOKEN') ?: null);
+            $clients[$index] = parityClient($options['url'], namespace: $runFixture['namespace'], token: getenv('DW_PARITY_TOKEN') ?: null);
             $start = microtime(true);
             $deadline = $start + 35;
             $state['run_budgets'][$index] = ['started_at_unix' => $start, 'deadline_at_unix' => $deadline];
diff --git a/scripts/conformance/server-parity/sdk-query-direction-probe.php b/scripts/conformance/server-parity/sdk-query-direction-probe.php
index 18dce9429..1beb8c232 100644
--- a/scripts/conformance/server-parity/sdk-query-direction-probe.php
+++ b/scripts/conformance/server-parity/sdk-query-direction-probe.php
@@ -4,6 +4,7 @@
 
 use Composer\InstalledVersions;
 use DurableWorkflow\Client;
+require_once __DIR__.'/lock-pressure-middleware.php';
 
 function sdkQueryActorOpen(string $language, string $phase, array $fixture, array $options, string $runId, float $deadline): array
 {
@@ -242,7 +243,7 @@ function sdkQueryDirectionHttpObservation(array $fixture, array $options): array
         throw new RuntimeException('SDK query direction requires its evidence directory.');
     }
     $spec = $fixture['sdk_query_direction'];
-    $client = new Client($options['url'], namespace: 'default', token: getenv('DW_PARITY_TOKEN') ?: null);
+    $client = parityClient($options['url'], namespace: 'default', token: getenv('DW_PARITY_TOKEN') ?: null);
     $deadline = microtime(true) + 35;
     $runId = '';
     $phases = $actors = [];
@@ -262,7 +263,7 @@ function sdkQueryDirectionHttpObservation(array $fixture, array $options): array
                         if ($request['method'] === 'POST' && $request['path'] === '/api/worker/register'
                             && $request['status'] === 201 && ($request['response']['registered'] ?? null) === true
                             && ($request['request']['worker_id'] ?? null) === $options['workflow-id'].':original') {
-                            $startClient = new Client($author['url'], namespace: 'default', token: getenv('DW_PARITY_TOKEN') ?: null);
+                            $startClient = parityClient($author['url'], namespace: 'default', token: getenv('DW_PARITY_TOKEN') ?: null);
                             $runId = $startClient->startWorkflow($fixture['workflow_type'], $options['workflow-id'],
                                 $spec['task_queue'], [$fixture['input'], $fixture['signal_count']])->selectedRunId;
                             $observerStart = ['role' => 'observer', 'language' => 'php', 'pid' => getmypid(),
diff --git a/scripts/conformance/server-parity/sdk-selected-run-signal-probe.php b/scripts/conformance/server-parity/sdk-selected-run-signal-probe.php
index a97a41a0f..cd11ce1c7 100644
--- a/scripts/conformance/server-parity/sdk-selected-run-signal-probe.php
+++ b/scripts/conformance/server-parity/sdk-selected-run-signal-probe.php
@@ -10,6 +10,7 @@
 use Workflow\V2\StartOptions;
 use Workflow\V2\WorkflowStub;
 use Workflow\WorkflowOptions;
+require_once __DIR__.'/lock-pressure-middleware.php';
 
 require __DIR__.'/selected-run-signal-state.php';
 
@@ -70,7 +71,7 @@ function selectedRunSignalHttpObservation(array $fixture, array $options): array
         if (! preg_match('#^http://127\.0\.0\.1:[0-9]+$#', $url)) {
             throw new RuntimeException('Selected-run control observer failed to bind.');
         }
-        $admin = new Client($url, namespace: 'default', token: getenv('DW_PARITY_TOKEN') ?: null);
+        $admin = parityClient($url, namespace: 'default', token: getenv('DW_PARITY_TOKEN') ?: null);
         foreach ($fixtures as $index => $runFixture) {
             $checkpoint('namespace_setup_'.$index);
             try {
@@ -84,7 +85,7 @@ function selectedRunSignalHttpObservation(array $fixture, array $options): array
             $state['administration'][] = ['created' => $created, 'namespace' => $namespace->raw];
             $paths[$index] = tempnam(sys_get_temp_dir(), 'parity-selected-run-');
             file_put_contents($paths[$index], json_encode($runFixture, JSON_THROW_ON_ERROR | JSON_UNESCAPED_UNICODE));
-            $clients[$index] = new Client($options['url'], namespace: $runFixture['namespace'], token: getenv('DW_PARITY_TOKEN') ?: null);
+            $clients[$index] = parityClient($options['url'], namespace: $runFixture['namespace'], token: getenv('DW_PARITY_TOKEN') ?: null);
             $start = microtime(true);
             $deadline = $start + 35;
             $state['run_budgets'][$index] = ['started_at_unix' => $start, 'deadline_at_unix' => $deadline];
diff --git a/scripts/conformance/server-parity/sdk-update-direction-probe.php b/scripts/conformance/server-parity/sdk-update-direction-probe.php
index 9fe3f7bb3..e8ce522c0 100644
--- a/scripts/conformance/server-parity/sdk-update-direction-probe.php
+++ b/scripts/conformance/server-parity/sdk-update-direction-probe.php
@@ -4,6 +4,7 @@
 
 use Composer\InstalledVersions;
 use DurableWorkflow\Client;
+require_once __DIR__.'/lock-pressure-middleware.php';
 
 function sdkUpdateActorOpen(string $language, string $phase, array $fixture, array $options, string $runId, float $deadline): array
 {
@@ -78,7 +79,7 @@ function sdkUpdateDirectionHttpObservation(array $fixture, array $options): arra
         throw new RuntimeException('SDK update direction requires its evidence directory.');
     }
     $spec = $fixture['sdk_update_direction'];
-    $client = new Client($options['url'], namespace: 'default', token: getenv('DW_PARITY_TOKEN') ?: null);
+    $client = parityClient($options['url'], namespace: 'default', token: getenv('DW_PARITY_TOKEN') ?: null);
     $deadline = microtime(true) + 35;
     $workflowId = $options['workflow-id'];
     $runId = '';
@@ -113,7 +114,7 @@ function sdkUpdateDirectionHttpObservation(array $fixture, array $options): arra
                     if ($request['method'] === 'POST' && $request['path'] === '/api/worker/register'
                         && $request['status'] === 201 && ($request['response']['registered'] ?? null) === true
                         && ($request['request']['worker_id'] ?? null) === $workflowId.':original') {
-                        $start = new Client($actor['url'], namespace: 'default', token: getenv('DW_PARITY_TOKEN') ?: null);
+                        $start = parityClient($actor['url'], namespace: 'default', token: getenv('DW_PARITY_TOKEN') ?: null);
                         $runId = $start->startWorkflow($fixture['workflow_type'], $workflowId,
                             $spec['task_queue'], [$fixture['input'], $fixture['signal_count']])->selectedRunId;
                         $observerStart = ['role' => 'observer', 'language' => 'php', 'pid' => getmypid(),
diff --git a/scripts/conformance/server-parity/task-retry-probe.php b/scripts/conformance/server-parity/task-retry-probe.php
index 42c81935b..fa05a5fd8 100644
--- a/scripts/conformance/server-parity/task-retry-probe.php
+++ b/scripts/conformance/server-parity/task-retry-probe.php
@@ -3,12 +3,13 @@
 declare(strict_types=1);
 
 use DurableWorkflow\Client;
+require_once __DIR__.'/lock-pressure-middleware.php';
 
 function finishHttpTaskRetry(Client $admin, array $fixture, string $workflowId, string $queue, string $url): array
 {
     $definition = $fixture['workflow_task_retry'];
     $requests = [];
-    $client = new Client($url, namespace: 'default', token: getenv('DW_PARITY_TOKEN') ?: null,
+    $client = parityClient($url, namespace: 'default', token: getenv('DW_PARITY_TOKEN') ?: null,
         transport: namespaceTransport($requests));
     $workerId = $workflowId.'-retry-worker';
     $peerId = $workflowId.$definition['peer_suffix'];
diff --git a/scripts/conformance/server-parity/waiting-history-probe.php b/scripts/conformance/server-parity/waiting-history-probe.php
index 6d21e0026..26d4efd99 100644
--- a/scripts/conformance/server-parity/waiting-history-probe.php
+++ b/scripts/conformance/server-parity/waiting-history-probe.php
@@ -3,12 +3,13 @@
 declare(strict_types=1);
 
 use DurableWorkflow\Client;
+require_once __DIR__.'/lock-pressure-middleware.php';
 
 function finishHttpWaitingHistory(Client $admin, array $fixture, string $workflowId, string $queue, string $url): array
 {
     $definition = $fixture['waiting_for_history'];
     $requests = [];
-    $client = new Client($url, namespace: 'default', token: getenv('DW_PARITY_TOKEN') ?: null,
+    $client = parityClient($url, namespace: 'default', token: getenv('DW_PARITY_TOKEN') ?: null,
         transport: namespaceTransport($requests));
     $workerId = $workflowId.'-waiting-worker';
     $peerId = $workflowId.$definition['peer_suffix'];
diff --git a/tests/Unit/ServerParityLockPressureRetryTest.php b/tests/Unit/ServerParityLockPressureRetryTest.php
index e29e3beb9..849e1b310 100644
--- a/tests/Unit/ServerParityLockPressureRetryTest.php
+++ b/tests/Unit/ServerParityLockPressureRetryTest.php
@@ -50,6 +50,30 @@ public function test_other_requests_statuses_and_bodies_are_never_retried(): voi
         }
     }
 
+    public function test_documented_operation_refusals_are_retried_and_polls_keep_their_rules(): void
+    {
+        $deferred = ['reason' => 'backend_lock_pressure', 'outcome' => 'deferred', 'retryable' => true, 'retry_after_seconds' => 1];
+        $complete = 'http://parity-server:8080/api/worker/workflow-tasks/task/complete';
+        $start = 'http://parity-server:8080/api/workflows';
+        self::assertSame(1.0, \lockPressureOperationRetryDelay('POST', $complete, 503, $deferred, 0, 0.0));
+        self::assertSame(1.0, \lockPressureOperationRetryDelay('POST', $start, 503,
+            ['reason' => 'backend_lock_pressure', 'retryable' => true, 'retry_after_seconds' => 1], 0, 0.0));
+        self::assertSame(1.0, \lockPressureOperationRetryDelay('POST', self::POLL, 503, $this->refusal(), 0, 0.0));
+        foreach ([
+            [$complete, 503, array_replace($deferred, ['retryable' => false])],
+            [$complete, 503, array_diff_key($deferred, ['retryable' => true])],
+            [$complete, 503, array_replace($deferred, ['reason' => 'backend_unavailable'])],
+            [$complete, 409, $deferred],
+            [$complete, 503, null],
+            // A poll refusal still needs task null, even through this entry point.
+            [self::POLL, 503, $deferred],
+        ] as $index => [$uri, $status, $response]) {
+            self::assertNull(\lockPressureOperationRetryDelay('POST', $uri, $status, $response, 0, 0.0), (string) $index);
+        }
+        self::assertNull(\lockPressureOperationRetryDelay('POST', $complete, 503, $deferred, 15, 0.0));
+        self::assertNull(\lockPressureOperationRetryDelay('POST', $complete, 503, $deferred, 2, 29.5));
+    }
+
     public function test_retries_stop_at_the_attempt_and_wait_budgets(): void
     {
         self::assertNull(\lockPressurePollRetryDelay('POST', self::POLL, 503, $this->refusal(), 15, 0.0));