diff --git a/CHANGELOG.md b/CHANGELOG.md
index 65c9f8549..67a30651d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+Bugfixes:
+* Fix flaky `SQLITE_IOERR_TRUNCATE` on Windows when multiple spago processes connect concurrently to the cache DB, by skipping `PRAGMA journal_mode = WAL` when it's already enabled (WAL mode is persistent in the DB file header) and tolerating the race on the initial set
+* Retry transient network failures (connection errors and 5xx responses) when fetching package tarballs and calling the registry API, instead of failing immediately
+
 ## [1.0.4] - 2026-03-30
 
 Bugfixes:
diff --git a/src/Spago/Command/Fetch.purs b/src/Spago/Command/Fetch.purs
index c439bea25..976dd9a3e 100644
--- a/src/Spago/Command/Fetch.purs
+++ b/src/Spago/Command/Fetch.purs
@@ -319,9 +319,13 @@ fetchPackagesToLocalCache packages = do
                         , url = packageUrl
                         }
                     )
-                  -- If we get a 503, we want the backoff to kick in, so we wait here and we'll eventually be retried
+                  -- If the request failed (connection error) or got a 5xx, we want the backoff
+                  -- to kick in. withBackoff' only retries on its own timeout, so we delay here
+                  -- to lose the race against runTimeout and trigger a retry.
                   case res of
-                    Right { status } | status == StatusCode 503 -> Aff.delay (Aff.Milliseconds 30_000.0)
+                    Left _ -> Aff.delay (Aff.Milliseconds 30_000.0)
+                    Right { status } | status >= StatusCode 500 && status < StatusCode 600 ->
+                      Aff.delay (Aff.Milliseconds 30_000.0)
                     _ -> pure unit
                   pure res
                 case response of
diff --git a/src/Spago/Db.js b/src/Spago/Db.js
index a21242237..db9d0c88b 100644
--- a/src/Spago/Db.js
+++ b/src/Spago/Db.js
@@ -11,10 +11,28 @@ export const connectImpl = (databasePath, logger) => {
 
   const db = new DatabaseSync(databasePath, {
     enableForeignKeyConstraints: true,
-    timeout: 5000, // Wait up to 5s if database is locked (matches better-sqlite3 default)
+    timeout: 5000, // Wait up to 5s if database is locked
   });
 
-  db.exec("PRAGMA journal_mode = WAL");
+  // WAL journal mode is persistent in the DB file header (bytes 18-19), so
+  // once set it sticks across connections and reopens. We skip the PRAGMA when
+  // it's already set to avoid hitting winTruncate on the wal-index (.shm),
+  // which races between concurrent spago processes on Windows and surfaces as
+  // SQLITE_IOERR_TRUNCATE (errcode 1546).
+  //
+  // When two fresh processes race the initial set, the loser's exec throws,
+  // but the winner has already written WAL to the header — so we only re-throw
+  // if WAL didn't actually end up enabled (i.e. the error wasn't the benign
+  // race we expect).
+  //
+  // See:
+  //   https://sqlite.org/pragma.html (journal_mode persistence)
+  //   https://sqlite.org/fileformat.html (header bytes 18-19 = WAL marker)
+  const inWal = () => db.prepare("PRAGMA journal_mode").get()?.journal_mode === "wal";
+  if (!inWal()) {
+    try { db.exec("PRAGMA journal_mode = WAL"); }
+    catch (e) { if (!inWal()) throw e; }
+  }
 
   db.prepare(`CREATE TABLE IF NOT EXISTS package_sets
     ( version TEXT PRIMARY KEY NOT NULL
diff --git a/src/Spago/Prelude.purs b/src/Spago/Prelude.purs
index 6f051baef..8e5de4e81 100644
--- a/src/Spago/Prelude.purs
+++ b/src/Spago/Prelude.purs
@@ -162,7 +162,7 @@ withBackoff { delay: Aff.Milliseconds timeout, action, shouldCancel, shouldRetry
         case maybeRetry of
           Maybe.Nothing -> pure Maybe.Nothing
           Maybe.Just newAction -> do
-            let newTimeout = Int.floor timeout `Int.pow` (attempt + 1)
+            let newTimeout = Int.floor timeout * (2 `Int.pow` attempt)
             maybeResult <- runAction attempt newAction newTimeout
             loop (attempt + 1) maybeResult
       Maybe.Just result ->
diff --git a/src/Spago/Registry.purs b/src/Spago/Registry.purs
index 2ede68d87..3f85f4bb0 100644
--- a/src/Spago/Registry.purs
+++ b/src/Spago/Registry.purs
@@ -431,13 +431,20 @@ submitRegistryOperation payload = do
 callRegistry :: forall env a b. String -> CJ.Codec b -> Maybe { codec :: CJ.Codec a, data :: a } -> Spago (GitEnv env) b
 callRegistry url outputCodec maybeInput = handleError do
   logDebug $ "Calling registry at " <> url
-  response <- liftAff $ withBackoff' $ try case maybeInput of
-    Just { codec: inputCodec, data: input } -> Http.fetch url
-      { method: Http.POST
-      , headers: { "Content-Type": "application/json" }
-      , body: Json.stringifyJson inputCodec input
-      }
-    Nothing -> Http.fetch url { method: Http.GET }
+  response <- liftAff $ withBackoff' do
+    res <- try case maybeInput of
+      Just { codec: inputCodec, data: input } -> Http.fetch url
+        { method: Http.POST
+        , headers: { "Content-Type": "application/json" }
+        , body: Json.stringifyJson inputCodec input
+        }
+      Nothing -> Http.fetch url { method: Http.GET }
+    case res of
+      Left _ -> Aff.delay (Aff.Milliseconds 30_000.0)
+      Right { status } | status >= 500 && status < 600 ->
+        Aff.delay (Aff.Milliseconds 30_000.0)
+      _ -> pure unit
+    pure res
   case response of
     Nothing -> pure $ Left $ "Could not reach the registry at " <> url
     Just (Left err) -> pure $ Left $ "Error while calling the registry:\n  " <> Exception.message err
diff --git a/test-fixtures/build/1148-warnings-diff-errors/errors/expected-stderr.txt b/test-fixtures/build/1148-warnings-diff-errors/errors/expected-stderr.txt
index a3ffb4e6f..39f17c106 100644
--- a/test-fixtures/build/1148-warnings-diff-errors/errors/expected-stderr.txt
+++ b/test-fixtures/build/1148-warnings-diff-errors/errors/expected-stderr.txt
@@ -4,8 +4,8 @@ Reading Spago workspace configuration...
 
 Downloading dependencies...
 Building...
-[1 of 2] Compiling Foo
-[2 of 2] Compiling Main
+[x of 2] Compiling module-name
+[x of 2] Compiling module-name
 [ERROR 1/2 TypesDoNotUnify] src/Foo.purs:4:5
 
   4  x = "nope"
diff --git a/test/Prelude.purs b/test/Prelude.purs
index 2263ddc5d..868e0cd65 100644
--- a/test/Prelude.purs
+++ b/test/Prelude.purs
@@ -9,6 +9,8 @@ import Data.Array as Array
 import Data.Map as Map
 import Data.String (Pattern(..), Replacement(..))
 import Data.String as String
+import Data.String.Regex as Regex
+import Data.String.Regex.Flags as RF
 import Effect.Aff as Aff
 import Effect.Aff.AVar (AVar)
 import Effect.Aff.AVar as AVar
@@ -176,6 +178,17 @@ sanitizePlatformOutput =
     >>> String.replaceAll (Pattern "\\") (Replacement "/")
     >>> String.replaceAll (Pattern "\r\n") (Replacement "\n")
 
+-- | Normalize `[N of <total>] Compiling <module>` lines. purs schedules
+-- | independent modules in whatever order system resources allow, so fixture
+-- | comparison has to ignore the order. Pass the total module count expected.
+normalizeCompileOrder :: Int -> String -> String
+normalizeCompileOrder total =
+  Regex.replace regex ("[x of " <> show total <> "] Compiling module-name")
+  where
+  regex = unsafeFromRight $ Regex.regex
+    ("\\[\\d+ of " <> show total <> "\\] Compiling [^\n]+")
+    RF.global
+
 checkFixture :: ∀ path. IsPath path => path -> FixturePath -> Aff Unit
 checkFixture filepath fixturePath = checkFixture' filepath fixturePath identity (shouldEqualStr `on` String.trim)
 
diff --git a/test/Spago/Build.purs b/test/Spago/Build.purs
index 240d5e32b..db0104b81 100644
--- a/test/Spago/Build.purs
+++ b/test/Spago/Build.purs
@@ -212,7 +212,7 @@ spec sem = Spec.parallel $ Spec.around (withBuildLock sem) do
             { stdoutFile: Nothing
             , stderrFile: Just $ fixture expectedFixture
             , result
-            , sanitize: sanitizePlatformOutput
+            , sanitize: sanitizePlatformOutput >>> normalizeCompileOrder 2
             }
 
       FS.copyTree { src: fixture "build/1148-warnings-diff-errors", dst: testCwd </> "." }
diff --git a/test/Spago/Publish.purs b/test/Spago/Publish.purs
index 054a0411a..bed67ea7f 100644
--- a/test/Spago/Publish.purs
+++ b/test/Spago/Publish.purs
@@ -5,8 +5,6 @@ module Test.Spago.Publish
 
 import Test.Prelude
 
-import Data.String.Regex as Regex
-import Data.String.Regex.Flags as RF
 import Node.Platform as Platform
 import Node.Process as Process
 import Spago.FS as FS
@@ -94,17 +92,9 @@ spec = Spec.around withTempDir do
           { stdoutFile: Nothing
           , stderrFile: Just file
           , result: isLeft
-          , sanitize: sanitizePlatformOutput >>> Regex.replace buildOrderRegex "[x of 3] Compiling module-name"
+          , sanitize: sanitizePlatformOutput >>> normalizeCompileOrder 3
           }
 
-        -- We have to ignore lines like "[1 of 3] Compiling Effect.Console" when
-        -- comparing output, because the compiler will always compile in
-        -- different order, depending on how the system resources happened to
-        -- align at the moment of the test run.
-        buildOrderRegex = unsafeFromRight $ Regex.regex
-          "\\[\\d of 3\\] Compiling (Effect\\.Console|Effect\\.Class\\.Console|Lib)"
-          RF.global
-
       FS.copyTree { src: fixture "publish/1110-solver-different-version", dst: testCwd }
       spago [ "build" ] >>= shouldBeSuccess
       doTheGitThing testCwd