diff --git a/apps/server/src/auth/Layers/AuthControlPlane.ts b/apps/server/src/auth/Layers/AuthControlPlane.ts
index aea07fd286f..6c42cd2db17 100644
--- a/apps/server/src/auth/Layers/AuthControlPlane.ts
+++ b/apps/server/src/auth/Layers/AuthControlPlane.ts
@@ -64,11 +64,16 @@ export const makeAuthControlPlane = Effect.gen(function* () {
 
   const listPairingLinks: AuthControlPlaneShape["listPairingLinks"] = (input) =>
     bootstrapCredentials.listActive().pipe(
-      Effect.map((pairingLinks) =>
-        pairingLinks
-          .filter((pairingLink) => (input?.role ? pairingLink.role === input.role : true))
-          .filter((pairingLink) => !input?.excludeSubjects?.includes(pairingLink.subject))
-          .map((pairingLink) =>
+      Effect.map((pairingLinks) => {
+        const activeLinks: Array<AuthPairingLink> = [];
+        for (const pairingLink of pairingLinks) {
+          if (input?.role && pairingLink.role !== input.role) {
+            continue;
+          }
+          if (input?.excludeSubjects?.includes(pairingLink.subject)) {
+            continue;
+          }
+          activeLinks.push(
             pairingLink.label
               ? ({
                   id: pairingLink.id,
@@ -87,11 +92,12 @@ export const makeAuthControlPlane = Effect.gen(function* () {
                   createdAt: pairingLink.createdAt,
                   expiresAt: pairingLink.expiresAt,
                 } satisfies AuthPairingLink),
-          )
-          .toSorted(
-            (left, right) => right.createdAt.epochMilliseconds - left.createdAt.epochMilliseconds,
-          ),
-      ),
+          );
+        }
+        return activeLinks.toSorted(
+          (left, right) => right.createdAt.epochMilliseconds - left.createdAt.epochMilliseconds,
+        );
+      }),
       Effect.mapError(toAuthControlPlaneError("Failed to list pairing links.")),
     );
 
diff --git a/apps/server/src/git/remoteRefs.ts b/apps/server/src/git/remoteRefs.ts
index b5dfc87bd07..e3873effe47 100644
--- a/apps/server/src/git/remoteRefs.ts
+++ b/apps/server/src/git/remoteRefs.ts
@@ -1,8 +1,12 @@
 export function parseRemoteNamesInGitOrder(stdout: string): ReadonlyArray<string> {
-  return stdout
-    .split("\n")
-    .map((line) => line.trim())
-    .filter((line) => line.length > 0);
+  const remoteNames: Array<string> = [];
+  for (const line of stdout.split("\n")) {
+    const remoteName = line.trim();
+    if (remoteName.length > 0) {
+      remoteNames.push(remoteName);
+    }
+  }
+  return remoteNames;
 }
 
 export function parseRemoteNames(stdout: string): ReadonlyArray<string> {
diff --git a/apps/server/src/imageMime.ts b/apps/server/src/imageMime.ts
index 814abbb32c1..c8761285abe 100644
--- a/apps/server/src/imageMime.ts
+++ b/apps/server/src/imageMime.ts
@@ -35,10 +35,13 @@ export function parseBase64DataUrl(
   const match = /^data:([^,]+),([a-z0-9+/=\r\n ]+)$/i.exec(dataUrl.trim());
   if (!match) return null;
 
-  const headerParts = (match[1] ?? "")
-    .split(";")
-    .map((part) => part.trim())
-    .filter((part) => part.length > 0);
+  const headerParts: Array<string> = [];
+  for (const part of (match[1] ?? "").split(";")) {
+    const trimmed = part.trim();
+    if (trimmed.length > 0) {
+      headerParts.push(trimmed);
+    }
+  }
   if (headerParts.length < 2) {
     return null;
   }
diff --git a/apps/server/src/keybindings.ts b/apps/server/src/keybindings.ts
index a197984f23a..80b522eee71 100644
--- a/apps/server/src/keybindings.ts
+++ b/apps/server/src/keybindings.ts
@@ -32,6 +32,7 @@ import * as Layer from "effect/Layer";
 import * as Option from "effect/Option";
 import * as Predicate from "effect/Predicate";
 import * as PubSub from "effect/PubSub";
+import * as Result from "effect/Result";
 import * as Schema from "effect/Schema";
 import * as SchemaIssue from "effect/SchemaIssue";
 import * as SchemaTransformation from "effect/SchemaTransformation";
@@ -538,9 +539,11 @@ const makeKeybindings = Effect.gen(function* () {
         return;
       }
 
-      const matchingDefaults = DEFAULT_KEYBINDINGS.filter((defaultRule) =>
-        customConfig.some((entry) => isSameKeybindingRule(entry, defaultRule)),
-      ).map((rule) => rule.command);
+      const matchingDefaults = Array.filterMap(DEFAULT_KEYBINDINGS, (defaultRule) =>
+        customConfig.some((entry) => isSameKeybindingRule(entry, defaultRule))
+          ? Result.succeed(defaultRule.command)
+          : Result.failVoid,
+      );
       if (matchingDefaults.length > 0) {
         yield* Effect.logWarning("default keybinding rule already defined in user config", {
           path: keybindingsConfigPath,
diff --git a/apps/server/src/orchestration/Layers/CheckpointReactor.ts b/apps/server/src/orchestration/Layers/CheckpointReactor.ts
index f95d5190bb0..40291ec4f66 100644
--- a/apps/server/src/orchestration/Layers/CheckpointReactor.ts
+++ b/apps/server/src/orchestration/Layers/CheckpointReactor.ts
@@ -1,5 +1,6 @@
 import {
   CommandId,
+  type CheckpointRef,
   EventId,
   MessageId,
   type ProjectId,
@@ -701,9 +702,12 @@ const make = Effect.gen(function* () {
       });
     }
 
-    const staleCheckpointRefs = thread.checkpoints
-      .filter((checkpoint) => checkpoint.checkpointTurnCount > event.payload.turnCount)
-      .map((checkpoint) => checkpoint.checkpointRef);
+    const staleCheckpointRefs: Array<CheckpointRef> = [];
+    for (const checkpoint of thread.checkpoints) {
+      if (checkpoint.checkpointTurnCount > event.payload.turnCount) {
+        staleCheckpointRefs.push(checkpoint.checkpointRef);
+      }
+    }
 
     if (staleCheckpointRefs.length > 0) {
       yield* checkpointStore.deleteCheckpointRefs({
diff --git a/apps/server/src/orchestration/Layers/ProjectionPipeline.ts b/apps/server/src/orchestration/Layers/ProjectionPipeline.ts
index 1161ff6a7d7..c201e1d9f9e 100644
--- a/apps/server/src/orchestration/Layers/ProjectionPipeline.ts
+++ b/apps/server/src/orchestration/Layers/ProjectionPipeline.ts
@@ -537,12 +537,15 @@ const makeOrchestrationProjectionPipeline = Effect.fn("makeOrchestrationProjecti
         projectionPendingApprovalRepository.listByThreadId({ threadId }),
       ]);
 
-      const latestUserMessageAt =
-        messages
-          .filter((message) => message.role === "user")
-          .map((message) => message.createdAt)
-          .toSorted()
-          .at(-1) ?? null;
+      let latestUserMessageAt: string | null = null;
+      for (const message of messages) {
+        if (
+          message.role === "user" &&
+          (latestUserMessageAt === null || message.createdAt > latestUserMessageAt)
+        ) {
+          latestUserMessageAt = message.createdAt;
+        }
+      }
 
       const pendingApprovalCount = pendingApprovals.filter(
         (approval) => approval.status === "pending",
diff --git a/apps/server/src/orchestration/Layers/ProjectionSnapshotQuery.ts b/apps/server/src/orchestration/Layers/ProjectionSnapshotQuery.ts
index 9b3c0fa7ad4..e629d1604b3 100644
--- a/apps/server/src/orchestration/Layers/ProjectionSnapshotQuery.ts
+++ b/apps/server/src/orchestration/Layers/ProjectionSnapshotQuery.ts
@@ -24,9 +24,11 @@ import {
   ProjectId,
   ThreadId,
 } from "@t3tools/contracts";
+import * as Arr from "effect/Array";
 import * as Effect from "effect/Effect";
 import * as Layer from "effect/Layer";
 import * as Option from "effect/Option";
+import * as Result from "effect/Result";
 import * as Schema from "effect/Schema";
 import * as Struct from "effect/Struct";
 import * as SqlClient from "effect/unstable/sql/SqlClient";
@@ -1488,34 +1490,36 @@ const makeProjectionSnapshotQuery = Effect.gen(function* () {
 
             const snapshot = {
               snapshotSequence: computeSnapshotSequence(stateRows),
-              projects: projectRows
-                .filter((row) => row.deletedAt === null)
-                .map((row) =>
-                  mapProjectShellRow(row, repositoryIdentities.get(row.projectId) ?? null),
-                ),
-              threads: threadRows
-                .filter((row) => row.deletedAt === null)
-                .map(
-                  (row): OrchestrationThreadShell => ({
-                    id: row.threadId,
-                    projectId: row.projectId,
-                    title: row.title,
-                    modelSelection: row.modelSelection,
-                    runtimeMode: row.runtimeMode,
-                    interactionMode: row.interactionMode,
-                    branch: row.branch,
-                    worktreePath: row.worktreePath,
-                    latestTurn: latestTurnByThread.get(row.threadId) ?? null,
-                    createdAt: row.createdAt,
-                    updatedAt: row.updatedAt,
-                    archivedAt: row.archivedAt,
-                    session: sessionByThread.get(row.threadId) ?? null,
-                    latestUserMessageAt: row.latestUserMessageAt,
-                    hasPendingApprovals: row.pendingApprovalCount > 0,
-                    hasPendingUserInput: row.pendingUserInputCount > 0,
-                    hasActionableProposedPlan: row.hasActionableProposedPlan > 0,
-                  }),
-                ),
+              projects: Arr.filterMap(projectRows, (row) =>
+                row.deletedAt === null
+                  ? Result.succeed(
+                      mapProjectShellRow(row, repositoryIdentities.get(row.projectId) ?? null),
+                    )
+                  : Result.failVoid,
+              ),
+              threads: Arr.filterMap(threadRows, (row) =>
+                row.deletedAt === null
+                  ? Result.succeed({
+                      id: row.threadId,
+                      projectId: row.projectId,
+                      title: row.title,
+                      modelSelection: row.modelSelection,
+                      runtimeMode: row.runtimeMode,
+                      interactionMode: row.interactionMode,
+                      branch: row.branch,
+                      worktreePath: row.worktreePath,
+                      latestTurn: latestTurnByThread.get(row.threadId) ?? null,
+                      createdAt: row.createdAt,
+                      updatedAt: row.updatedAt,
+                      archivedAt: row.archivedAt,
+                      session: sessionByThread.get(row.threadId) ?? null,
+                      latestUserMessageAt: row.latestUserMessageAt,
+                      hasPendingApprovals: row.pendingApprovalCount > 0,
+                      hasPendingUserInput: row.pendingUserInputCount > 0,
+                      hasActionableProposedPlan: row.hasActionableProposedPlan > 0,
+                    } satisfies OrchestrationThreadShell)
+                  : Result.failVoid,
+              ),
               updatedAt: updatedAt ?? "1970-01-01T00:00:00.000Z",
             };
 
@@ -1621,11 +1625,13 @@ const makeProjectionSnapshotQuery = Effect.gen(function* () {
 
             const snapshot = {
               snapshotSequence: computeSnapshotSequence(stateRows),
-              projects: projectRows
-                .filter((row) => row.deletedAt === null && activeProjectIds.has(row.projectId))
-                .map((row) =>
-                  mapProjectShellRow(row, repositoryIdentities.get(row.projectId) ?? null),
-                ),
+              projects: Arr.filterMap(projectRows, (row) =>
+                row.deletedAt === null && activeProjectIds.has(row.projectId)
+                  ? Result.succeed(
+                      mapProjectShellRow(row, repositoryIdentities.get(row.projectId) ?? null),
+                    )
+                  : Result.failVoid,
+              ),
               threads: threadRows.map(
                 (row): OrchestrationThreadShell => ({
                   id: row.threadId,
diff --git a/apps/server/src/provider/Layers/ClaudeAdapter.ts b/apps/server/src/provider/Layers/ClaudeAdapter.ts
index a132bf73386..ff9bbfe0231 100644
--- a/apps/server/src/provider/Layers/ClaudeAdapter.ts
+++ b/apps/server/src/provider/Layers/ClaudeAdapter.ts
@@ -245,9 +245,13 @@ function toProcessError(
 function normalizeClaudeStreamMessages(
   cause: Cause.Cause<{ readonly message: string }>,
 ): ReadonlyArray<string> {
-  const errors = Cause.prettyErrors(cause)
-    .map((error) => error.message.trim())
-    .filter((message) => message.length > 0);
+  const errors: Array<string> = [];
+  for (const error of Cause.prettyErrors(cause)) {
+    const message = error.message.trim();
+    if (message.length > 0) {
+      errors.push(message);
+    }
+  }
   if (errors.length > 0) {
     return errors;
   }
diff --git a/apps/server/src/provider/Layers/ClaudeProvider.ts b/apps/server/src/provider/Layers/ClaudeProvider.ts
index 6522513d015..badbf98905a 100644
--- a/apps/server/src/provider/Layers/ClaudeProvider.ts
+++ b/apps/server/src/provider/Layers/ClaudeProvider.ts
@@ -317,11 +317,13 @@ export function resolveClaudeApiModelId(modelSelection: ModelSelection): string
 }
 
 function toTitleCaseWords(value: string): string {
-  return value
-    .split(/[\s_-]+/g)
-    .filter(Boolean)
-    .map((part) => part[0]!.toUpperCase() + part.slice(1).toLowerCase())
-    .join(" ");
+  const parts: Array<string> = [];
+  for (const part of value.split(/[\s_-]+/g)) {
+    if (part.length > 0) {
+      parts.push(part[0]!.toUpperCase() + part.slice(1).toLowerCase());
+    }
+  }
+  return parts.join(" ");
 }
 
 function claudeSubscriptionLabel(subscriptionType: string | undefined): string | undefined {
diff --git a/apps/server/src/provider/Layers/CodexProvider.ts b/apps/server/src/provider/Layers/CodexProvider.ts
index 178450fb7fd..4d793194c1d 100644
--- a/apps/server/src/provider/Layers/CodexProvider.ts
+++ b/apps/server/src/provider/Layers/CodexProvider.ts
@@ -319,16 +319,21 @@ const probeCodexAppServerProvider = Effect.fn("probeCodexAppServerProvider")(fun
   } satisfies CodexAppServerProviderSnapshot;
 });
 
-const emptyCodexModelsFromSettings = (codexSettings: CodexSettings): ServerProvider["models"] =>
-  codexSettings.customModels
-    .map((model) => model.trim())
-    .filter((model, index, models) => model.length > 0 && models.indexOf(model) === index)
-    .map((model) => ({
-      slug: model,
-      name: model,
-      isCustom: true,
-      capabilities: null,
-    }));
+const emptyCodexModelsFromSettings = (codexSettings: CodexSettings): ServerProvider["models"] => {
+  const models = new Set<string>();
+  for (const model of codexSettings.customModels) {
+    const trimmed = model.trim();
+    if (trimmed.length > 0) {
+      models.add(trimmed);
+    }
+  }
+  return Array.from(models, (model) => ({
+    slug: model,
+    name: model,
+    isCustom: true,
+    capabilities: null,
+  }));
+};
 
 const makePendingCodexProvider = (
   codexSettings: CodexSettings,
diff --git a/apps/server/src/provider/Layers/CursorProvider.ts b/apps/server/src/provider/Layers/CursorProvider.ts
index 035c08437a9..88a963f693b 100644
--- a/apps/server/src/provider/Layers/CursorProvider.ts
+++ b/apps/server/src/provider/Layers/CursorProvider.ts
@@ -596,11 +596,12 @@ export const discoverCursorModelCapabilitiesViaAcp = (
           );
         }
 
-        const targetModelSlugs = new Set(
-          existingModels
-            .filter((model) => !model.isCustom && !hasCursorModelCapabilities(model))
-            .map((model) => model.slug),
-        );
+        const targetModelSlugs = new Set<string>();
+        for (const model of existingModels) {
+          if (!model.isCustom && !hasCursorModelCapabilities(model)) {
+            targetModelSlugs.add(model.slug);
+          }
+        }
         if (targetModelSlugs.size === 0) {
           return buildCursorDiscoveredModels(
             modelChoices.map((modelChoice) => ({
@@ -721,9 +722,13 @@ export interface CursorAboutResult {
 }
 
 function joinProviderMessages(...messages: ReadonlyArray<string | undefined>): string | undefined {
-  const parts = messages
-    .map((message) => message?.trim())
-    .filter((message): message is string => Boolean(message));
+  const parts: Array<string> = [];
+  for (const message of messages) {
+    const trimmed = message?.trim();
+    if (trimmed) {
+      parts.push(trimmed);
+    }
+  }
   return parts.length > 0 ? parts.join(" ") : undefined;
 }
 
@@ -790,11 +795,13 @@ export function parseCursorCliConfigChannel(raw: string): string | undefined {
 }
 
 function toTitleCaseWords(value: string): string {
-  return value
-    .split(/[\s_-]+/g)
-    .filter((part) => part.length > 0)
-    .map((part) => part.charAt(0).toUpperCase() + part.slice(1).toLowerCase())
-    .join(" ");
+  const parts: Array<string> = [];
+  for (const part of value.split(/[\s_-]+/g)) {
+    if (part.length > 0) {
+      parts.push(part.charAt(0).toUpperCase() + part.slice(1).toLowerCase());
+    }
+  }
+  return parts.join(" ");
 }
 
 function cursorSubscriptionLabel(subscriptionType: string | undefined): string | undefined {
diff --git a/apps/server/src/provider/Layers/OpenCodeAdapter.ts b/apps/server/src/provider/Layers/OpenCodeAdapter.ts
index bfc36aff4c3..34a67199125 100644
--- a/apps/server/src/provider/Layers/OpenCodeAdapter.ts
+++ b/apps/server/src/provider/Layers/OpenCodeAdapter.ts
@@ -1366,12 +1366,15 @@ export function makeOpenCodeAdapter(
           }),
         ).pipe(Effect.mapError(toRequestError));
 
-        const turns = (messages.data ?? [])
-          .filter((entry) => entry.info.role === "assistant")
-          .map((entry) => ({
-            id: TurnId.make(entry.info.id),
-            items: [entry.info, ...entry.parts],
-          }));
+        const turns: Array<OpenCodeTurnSnapshot> = [];
+        for (const entry of messages.data ?? []) {
+          if (entry.info.role === "assistant") {
+            turns.push({
+              id: TurnId.make(entry.info.id),
+              items: [entry.info, ...entry.parts],
+            });
+          }
+        }
 
         return {
           threadId,
diff --git a/apps/server/src/provider/Layers/OpenCodeProvider.ts b/apps/server/src/provider/Layers/OpenCodeProvider.ts
index fa436b5fbe0..8842b1da5ce 100644
--- a/apps/server/src/provider/Layers/OpenCodeProvider.ts
+++ b/apps/server/src/provider/Layers/OpenCodeProvider.ts
@@ -137,11 +137,13 @@ function formatOpenCodeProbeError(input: {
 }
 
 function titleCaseSlug(value: string): string {
-  return value
-    .split(/[-_/]+/)
-    .filter((segment) => segment.length > 0)
-    .map((segment) => segment.charAt(0).toUpperCase() + segment.slice(1))
-    .join(" ");
+  const segments: Array<string> = [];
+  for (const segment of value.split(/[-_/]+/)) {
+    if (segment.length > 0) {
+      segments.push(segment.charAt(0).toUpperCase() + segment.slice(1));
+    }
+  }
+  return segments.join(" ");
 }
 
 function inferDefaultVariant(
diff --git a/apps/server/src/provider/acp/AcpRuntimeModel.ts b/apps/server/src/provider/acp/AcpRuntimeModel.ts
index ffd214a5bf1..3587d703dbd 100644
--- a/apps/server/src/provider/acp/AcpRuntimeModel.ts
+++ b/apps/server/src/provider/acp/AcpRuntimeModel.ts
@@ -126,19 +126,20 @@ export function parseSessionModeState(
   if (!currentModeId) {
     return undefined;
   }
-  const availableModes = modes.availableModes
-    .map((mode) => {
-      const id = mode.id.trim();
-      const name = mode.name.trim();
-      if (!id || !name) {
-        return undefined;
-      }
-      const description = mode.description?.trim() || undefined;
-      return description !== undefined
+  const availableModes: Array<AcpSessionMode> = [];
+  for (const mode of modes.availableModes) {
+    const id = mode.id.trim();
+    const name = mode.name.trim();
+    if (!id || !name) {
+      continue;
+    }
+    const description = mode.description?.trim() || undefined;
+    availableModes.push(
+      description !== undefined
         ? ({ id, name, description } satisfies AcpSessionMode)
-        : ({ id, name } satisfies AcpSessionMode);
-    })
-    .filter((mode): mode is AcpSessionMode => mode !== undefined);
+        : ({ id, name } satisfies AcpSessionMode),
+    );
+  }
   if (availableModes.length === 0) {
     return undefined;
   }
@@ -186,9 +187,15 @@ function normalizeCommandValue(value: unknown): string | undefined {
   if (!Array.isArray(value)) {
     return undefined;
   }
-  const parts = value
-    .map((entry) => (typeof entry === "string" && entry.trim().length > 0 ? entry.trim() : null))
-    .filter((entry): entry is string => entry !== null);
+  const parts: Array<string> = [];
+  for (const entry of value) {
+    if (typeof entry === "string") {
+      const part = entry.trim();
+      if (part.length > 0) {
+        parts.push(part);
+      }
+    }
+  }
   return parts.length > 0 ? parts.join(" ") : undefined;
 }
 
@@ -222,18 +229,20 @@ function extractTextContentFromToolCallContent(
   content: ReadonlyArray<EffectAcpSchema.ToolCallContent> | null | undefined,
 ): string | undefined {
   if (!content) return undefined;
-  const chunks = content
-    .map((entry) => {
-      if (entry.type !== "content") {
-        return undefined;
-      }
-      const nestedContent = entry.content;
-      if (nestedContent.type !== "text") {
-        return undefined;
-      }
-      return nestedContent.text.trim().length > 0 ? nestedContent.text.trim() : undefined;
-    })
-    .filter((entry): entry is string => entry !== undefined);
+  const chunks: Array<string> = [];
+  for (const entry of content) {
+    if (entry.type !== "content") {
+      continue;
+    }
+    const nestedContent = entry.content;
+    if (nestedContent.type !== "text") {
+      continue;
+    }
+    const text = nestedContent.text.trim();
+    if (text.length > 0) {
+      chunks.push(text);
+    }
+  }
   return chunks.length > 0 ? chunks.join("\n") : undefined;
 }
 
diff --git a/apps/server/src/provider/providerMaintenanceRunner.ts b/apps/server/src/provider/providerMaintenanceRunner.ts
index 6a759b79f7d..f04e97a13ec 100644
--- a/apps/server/src/provider/providerMaintenanceRunner.ts
+++ b/apps/server/src/provider/providerMaintenanceRunner.ts
@@ -214,13 +214,15 @@ export const make = Effect.fn("ProviderMaintenanceRunner.make")(function* () {
     instanceId: ProviderInstanceId,
   ): Effect.Effect<VerifiedProviderRefresh> =>
     providerRegistry.getProviders.pipe(
-      Effect.map((providers) =>
-        providers
-          .filter(
-            (candidate) => candidate.driver === provider && candidate.instanceId === instanceId,
-          )
-          .map((candidate) => candidate.instanceId),
-      ),
+      Effect.map((providers) => {
+        const instanceIds: Array<ProviderInstanceId> = [];
+        for (const candidate of providers) {
+          if (candidate.driver === provider && candidate.instanceId === instanceId) {
+            instanceIds.push(candidate.instanceId);
+          }
+        }
+        return instanceIds;
+      }),
       Effect.flatMap((instanceIds) =>
         instanceIds.length === 0
           ? providerRegistry.refreshInstance(instanceId)
diff --git a/apps/server/src/sourceControl/AzureDevOpsCli.ts b/apps/server/src/sourceControl/AzureDevOpsCli.ts
index 29a57f993c4..fe4c76b288d 100644
--- a/apps/server/src/sourceControl/AzureDevOpsCli.ts
+++ b/apps/server/src/sourceControl/AzureDevOpsCli.ts
@@ -208,10 +208,13 @@ function parseRepositorySpecifier(repository: string): {
   readonly project: string | null;
   readonly name: string;
 } {
-  const parts = repository
-    .split("/")
-    .map((part) => part.trim())
-    .filter((part) => part.length > 0);
+  const parts: Array<string> = [];
+  for (const part of repository.split("/")) {
+    const trimmed = part.trim();
+    if (trimmed.length > 0) {
+      parts.push(trimmed);
+    }
+  }
   return {
     project: parts.length > 1 ? (parts.at(-2) ?? null) : null,
     name: parts.at(-1) ?? repository.trim(),
diff --git a/apps/server/src/sourceControl/GitLabCli.ts b/apps/server/src/sourceControl/GitLabCli.ts
index 789e0cf72e3..b4e039cfd8e 100644
--- a/apps/server/src/sourceControl/GitLabCli.ts
+++ b/apps/server/src/sourceControl/GitLabCli.ts
@@ -247,10 +247,13 @@ function parseRepositoryPath(repository: string): {
   readonly namespacePath: string | null;
   readonly projectPath: string;
 } {
-  const parts = repository
-    .split("/")
-    .map((part) => part.trim())
-    .filter((part) => part.length > 0);
+  const parts: Array<string> = [];
+  for (const part of repository.split("/")) {
+    const trimmed = part.trim();
+    if (trimmed.length > 0) {
+      parts.push(trimmed);
+    }
+  }
   const projectPath = parts.at(-1) ?? repository.trim();
   const namespacePath = parts.length > 1 ? parts.slice(0, -1).join("/") : null;
   return { namespacePath, projectPath };
diff --git a/apps/server/src/sourceControl/SourceControlProviderDiscovery.ts b/apps/server/src/sourceControl/SourceControlProviderDiscovery.ts
index 23bbada043a..b42cb853a57 100644
--- a/apps/server/src/sourceControl/SourceControlProviderDiscovery.ts
+++ b/apps/server/src/sourceControl/SourceControlProviderDiscovery.ts
@@ -96,15 +96,24 @@ export function unknownAuth(detail?: string): SourceControlProviderAuth {
 }
 
 export function combinedAuthOutput(input: SourceControlAuthProbeInput): string {
-  return [input.stdout, input.stderr].filter((entry) => entry.trim().length > 0).join("\n");
+  const parts: string[] = [];
+  for (const entry of [input.stdout, input.stderr]) {
+    if (entry.trim().length > 0) {
+      parts.push(entry);
+    }
+  }
+  return parts.join("\n");
 }
 
 function sanitizedAuthLines(text: string): ReadonlyArray<string> {
-  return text
-    .split(/\r?\n/)
-    .map((entry) => entry.trim())
-    .filter((entry) => entry.length > 0)
-    .filter((entry) => !/^[-\s]*token(?:\s+scopes?)?:/iu.test(entry));
+  const lines: string[] = [];
+  for (const entry of text.split(/\r?\n/)) {
+    const line = entry.trim();
+    if (line.length === 0) continue;
+    if (/^[-\s]*token(?:\s+scopes?)?:/iu.test(line)) continue;
+    lines.push(line);
+  }
+  return lines;
 }
 
 export function firstSafeAuthLine(text: string): string | undefined {
diff --git a/apps/server/src/sourceControl/SourceControlProviderRegistry.ts b/apps/server/src/sourceControl/SourceControlProviderRegistry.ts
index 5b625e6690b..b927d8c77b6 100644
--- a/apps/server/src/sourceControl/SourceControlProviderRegistry.ts
+++ b/apps/server/src/sourceControl/SourceControlProviderRegistry.ts
@@ -92,18 +92,17 @@ function selectProviderContext(
     readonly url: string;
   }>,
 ): SourceControlProvider.SourceControlProviderContext | null {
-  const candidates = remotes
-    .map((remote) => {
-      const provider = detectSourceControlProviderFromRemoteUrl(remote.url);
-      return provider
-        ? {
-            provider,
-            remoteName: remote.name,
-            remoteUrl: remote.url,
-          }
-        : null;
-    })
-    .filter((value): value is SourceControlProvider.SourceControlProviderContext => value !== null);
+  const candidates: Array<SourceControlProvider.SourceControlProviderContext> = [];
+  for (const remote of remotes) {
+    const provider = detectSourceControlProviderFromRemoteUrl(remote.url);
+    if (provider) {
+      candidates.push({
+        provider,
+        remoteName: remote.name,
+        remoteUrl: remote.url,
+      });
+    }
+  }
 
   return (
     candidates.find((candidate) => candidate.remoteName === "origin") ??
diff --git a/apps/server/src/vcs/GitVcsDriverCore.ts b/apps/server/src/vcs/GitVcsDriverCore.ts
index 19f12862dad..7a4fb6dd46f 100644
--- a/apps/server/src/vcs/GitVcsDriverCore.ts
+++ b/apps/server/src/vcs/GitVcsDriverCore.ts
@@ -1,3 +1,4 @@
+import * as Arr from "effect/Array";
 import * as Cache from "effect/Cache";
 import * as Data from "effect/Data";
 import * as DateTime from "effect/DateTime";
@@ -1793,61 +1794,60 @@ export const makeGitVcsDriverCore = Effect.fn("makeGitVcsDriverCore")(function*
         }
       }
 
-      const localBranches = localBranchResult.stdout
-        .split("\n")
-        .map(parseBranchLine)
-        .filter((refName): refName is { name: string; current: boolean } => refName !== null)
-        .map((refName) => ({
-          name: refName.name,
-          current: refName.current,
-          isRemote: false,
-          isDefault: refName.name === defaultBranch,
-          worktreePath: worktreeMap.get(refName.name) ?? null,
-        }))
-        .toSorted((a, b) => {
-          const aPriority = a.current ? 0 : a.isDefault ? 1 : 2;
-          const bPriority = b.current ? 0 : b.isDefault ? 1 : 2;
-          if (aPriority !== bPriority) return aPriority - bPriority;
-
-          const aLastCommit = branchLastCommit.get(a.name) ?? 0;
-          const bLastCommit = branchLastCommit.get(b.name) ?? 0;
-          if (aLastCommit !== bLastCommit) return bLastCommit - aLastCommit;
-          return a.name.localeCompare(b.name);
-        });
+      const localBranches = Arr.filterMap(localBranchResult.stdout.split("\n"), (line) => {
+        const refName = parseBranchLine(line);
+        return refName === null
+          ? Result.failVoid
+          : Result.succeed({
+              name: refName.name,
+              current: refName.current,
+              isRemote: false,
+              isDefault: refName.name === defaultBranch,
+              worktreePath: worktreeMap.get(refName.name) ?? null,
+            });
+      }).toSorted((a, b) => {
+        const aPriority = a.current ? 0 : a.isDefault ? 1 : 2;
+        const bPriority = b.current ? 0 : b.isDefault ? 1 : 2;
+        if (aPriority !== bPriority) return aPriority - bPriority;
+
+        const aLastCommit = branchLastCommit.get(a.name) ?? 0;
+        const bLastCommit = branchLastCommit.get(b.name) ?? 0;
+        if (aLastCommit !== bLastCommit) return bLastCommit - aLastCommit;
+        return a.name.localeCompare(b.name);
+      });
 
       const remoteBranches =
         remoteBranchResult.exitCode === 0
-          ? remoteBranchResult.stdout
-              .split("\n")
-              .map(parseBranchLine)
-              .filter((refName): refName is { name: string; current: boolean } => refName !== null)
-              .map((refName) => {
-                const parsedRemoteRef = parseRemoteRefWithRemoteNames(refName.name, remoteNames);
-                const remoteBranch: {
-                  name: string;
-                  current: boolean;
-                  isRemote: boolean;
-                  remoteName?: string;
-                  isDefault: boolean;
-                  worktreePath: string | null;
-                } = {
-                  name: refName.name,
-                  current: false,
-                  isRemote: true,
-                  isDefault: false,
-                  worktreePath: null,
-                };
-                if (parsedRemoteRef) {
-                  remoteBranch.remoteName = parsedRemoteRef.remoteName;
-                }
-                return remoteBranch;
-              })
-              .toSorted((a, b) => {
-                const aLastCommit = branchLastCommit.get(a.name) ?? 0;
-                const bLastCommit = branchLastCommit.get(b.name) ?? 0;
-                if (aLastCommit !== bLastCommit) return bLastCommit - aLastCommit;
-                return a.name.localeCompare(b.name);
-              })
+          ? Arr.filterMap(remoteBranchResult.stdout.split("\n"), (line) => {
+              const refName = parseBranchLine(line);
+              if (refName === null) {
+                return Result.failVoid;
+              }
+              const parsedRemoteRef = parseRemoteRefWithRemoteNames(refName.name, remoteNames);
+              const remoteBranch: {
+                name: string;
+                current: boolean;
+                isRemote: boolean;
+                remoteName?: string;
+                isDefault: boolean;
+                worktreePath: string | null;
+              } = {
+                name: refName.name,
+                current: false,
+                isRemote: true,
+                isDefault: false,
+                worktreePath: null,
+              };
+              if (parsedRemoteRef) {
+                remoteBranch.remoteName = parsedRemoteRef.remoteName;
+              }
+              return Result.succeed(remoteBranch);
+            }).toSorted((a, b) => {
+              const aLastCommit = branchLastCommit.get(a.name) ?? 0;
+              const bLastCommit = branchLastCommit.get(b.name) ?? 0;
+              if (aLastCommit !== bLastCommit) return bLastCommit - aLastCommit;
+              return a.name.localeCompare(b.name);
+            })
           : [];
 
       const refs = paginateBranches({
@@ -2106,12 +2106,16 @@ export const makeGitVcsDriverCore = Effect.fn("makeGitVcsDriverCore")(function*
       "--no-column",
       "--format=%(refname:short)",
     ]).pipe(
-      Effect.map((stdout) =>
-        stdout
-          .split("\n")
-          .map((line) => line.trim())
-          .filter((line) => line.length > 0),
-      ),
+      Effect.map((stdout) => {
+        const branchNames: Array<string> = [];
+        for (const line of stdout.split("\n")) {
+          const branchName = line.trim();
+          if (branchName.length > 0) {
+            branchNames.push(branchName);
+          }
+        }
+        return branchNames;
+      }),
     );
 
   return GitVcsDriver.GitVcsDriver.of({
diff --git a/apps/server/src/workspace/Layers/WorkspaceEntries.ts b/apps/server/src/workspace/Layers/WorkspaceEntries.ts
index 0c0ab638207..db4a5c230c3 100644
--- a/apps/server/src/workspace/Layers/WorkspaceEntries.ts
+++ b/apps/server/src/workspace/Layers/WorkspaceEntries.ts
@@ -221,9 +221,13 @@ export const makeWorkspaceEntries = Effect.gen(function* () {
         return null;
       }
 
-      const listedPaths = [...listedFiles.paths]
-        .map((entry) => toPosixPath(entry))
-        .filter((entry) => entry.length > 0 && !isPathInIgnoredDirectory(entry));
+      const listedPaths: Array<string> = [];
+      for (const rawEntry of listedFiles.paths) {
+        const entry = toPosixPath(rawEntry);
+        if (entry.length > 0 && !isPathInIgnoredDirectory(entry)) {
+          listedPaths.push(entry);
+        }
+      }
       const filePaths = yield* vcs.driver.filterIgnoredPaths(cwd, listedPaths).pipe(
         Effect.map((paths) => [...paths]),
         Effect.catch(() => filterVcsIgnoredPaths(cwd, listedPaths)),
@@ -456,21 +460,23 @@ export const makeWorkspaceEntries = Effect.gen(function* () {
 
       const showHidden = endsWithSeparator || prefix.startsWith(".");
       const lowerPrefix = prefix.toLowerCase();
+      const entries: Array<{ readonly name: string; readonly fullPath: string }> = [];
+      for (const dirent of dirents) {
+        if (
+          dirent.isDirectory() &&
+          dirent.name.toLowerCase().startsWith(lowerPrefix) &&
+          (showHidden || !dirent.name.startsWith("."))
+        ) {
+          entries.push({
+            name: dirent.name,
+            fullPath: path.join(parentPath, dirent.name),
+          });
+        }
+      }
 
       return {
         parentPath,
-        entries: dirents
-          .filter(
-            (dirent) =>
-              dirent.isDirectory() &&
-              dirent.name.toLowerCase().startsWith(lowerPrefix) &&
-              (showHidden || !dirent.name.startsWith(".")),
-          )
-          .map((dirent) => ({
-            name: dirent.name,
-            fullPath: path.join(parentPath, dirent.name),
-          }))
-          .toSorted((left, right) => left.name.localeCompare(right.name)),
+        entries: entries.toSorted((left, right) => left.name.localeCompare(right.name)),
       };
     },
   );
diff --git a/apps/web/src/components/CommandPalette.logic.ts b/apps/web/src/components/CommandPalette.logic.ts
index 3f4997e215c..4484232c2b8 100644
--- a/apps/web/src/components/CommandPalette.logic.ts
+++ b/apps/web/src/components/CommandPalette.logic.ts
@@ -1,5 +1,7 @@
 import { type KeybindingCommand, type FilesystemBrowseEntry } from "@t3tools/contracts";
 import type { SidebarThreadSortOrder } from "@t3tools/contracts/settings";
+import * as Arr from "effect/Array";
+import * as Result from "effect/Result";
 import { type ReactNode } from "react";
 import { sortThreads } from "../lib/threadSort";
 import { formatRelativeTimeLabel } from "../timestampFormat";
@@ -252,23 +254,18 @@ export function filterCommandPaletteGroups(input: {
   }
 
   return searchableGroups.flatMap((group) => {
-    const items = group.items
-      .map((item, index) => {
-        const haystack = normalizeSearchText(item.searchTerms.join(" "));
-        if (!haystack.includes(normalizedQuery)) {
-          return null;
-        }
-
-        return {
-          item,
-          index,
-          rank: rankCommandPaletteItemMatch(item, normalizedQuery),
-        };
-      })
-      .filter(
-        (entry): entry is { item: (typeof group.items)[number]; index: number; rank: number } =>
-          entry !== null,
-      )
+    const items = Arr.filterMap(group.items, (item, index) => {
+      const haystack = normalizeSearchText(item.searchTerms.join(" "));
+      if (!haystack.includes(normalizedQuery)) {
+        return Result.failVoid;
+      }
+
+      return Result.succeed({
+        item,
+        index,
+        rank: rankCommandPaletteItemMatch(item, normalizedQuery),
+      });
+    })
       .toSorted((left, right) => right.rank - left.rank || left.index - right.index)
       .map((entry) => entry.item);
 
diff --git a/apps/web/src/components/DiffPanel.tsx b/apps/web/src/components/DiffPanel.tsx
index f178a69fb43..33281ed58e1 100644
--- a/apps/web/src/components/DiffPanel.tsx
+++ b/apps/web/src/components/DiffPanel.tsx
@@ -261,12 +261,14 @@ export default function DiffPanel({ mode = "inline" }: DiffPanelProps) {
     [selectedCheckpointTurnCount],
   );
   const conversationCheckpointTurnCount = useMemo(() => {
-    const turnCounts = orderedTurnDiffSummaries
-      .map(
-        (summary) =>
-          summary.checkpointTurnCount ?? inferredCheckpointTurnCountByTurnId[summary.turnId],
-      )
-      .filter((value): value is number => typeof value === "number");
+    const turnCounts: Array<number> = [];
+    for (const summary of orderedTurnDiffSummaries) {
+      const value =
+        summary.checkpointTurnCount ?? inferredCheckpointTurnCountByTurnId[summary.turnId];
+      if (typeof value === "number") {
+        turnCounts.push(value);
+      }
+    }
     if (turnCounts.length === 0) {
       return undefined;
     }
diff --git a/apps/web/src/components/chat/ChatComposer.tsx b/apps/web/src/components/chat/ChatComposer.tsx
index b19e1240364..41535110091 100644
--- a/apps/web/src/components/chat/ChatComposer.tsx
+++ b/apps/web/src/components/chat/ChatComposer.tsx
@@ -1323,9 +1323,12 @@ export const ChatComposer = memo(function ChatComposer(props: ChatComposerProps)
       } catch {
         const currentImageIds = new Set(composerImages.map((image) => image.id));
         const fallbackPersistedAttachments = getPersistedAttachmentsForThread();
-        const fallbackPersistedIds = fallbackPersistedAttachments
-          .map((attachment) => attachment.id)
-          .filter((id) => currentImageIds.has(id));
+        const fallbackPersistedIds: Array<string> = [];
+        for (const attachment of fallbackPersistedAttachments) {
+          if (currentImageIds.has(attachment.id)) {
+            fallbackPersistedIds.push(attachment.id);
+          }
+        }
         const fallbackPersistedIdSet = new Set(fallbackPersistedIds);
         const fallbackAttachments = fallbackPersistedAttachments.filter((attachment) =>
           fallbackPersistedIdSet.has(attachment.id),
diff --git a/apps/web/src/components/chat/ModelPickerContent.tsx b/apps/web/src/components/chat/ModelPickerContent.tsx
index c3468ef8c65..c9fbd2b0fc1 100644
--- a/apps/web/src/components/chat/ModelPickerContent.tsx
+++ b/apps/web/src/components/chat/ModelPickerContent.tsx
@@ -272,8 +272,13 @@ export const ModelPickerContent = memo(function ModelPickerContent(props: {
       // ignoring sidebar selection so account-scoped searches can find a
       // model before the user chooses a specific instance rail item.
       if (props.lockedProvider !== null) {
-        return rankedMatches
-          .filter((rankedModel) => matchesLockedProvider(rankedModel.model))
+        const lockedProviderMatches: Array<(typeof rankedMatches)[number]> = [];
+        for (const rankedModel of rankedMatches) {
+          if (matchesLockedProvider(rankedModel.model)) {
+            lockedProviderMatches.push(rankedModel);
+          }
+        }
+        return lockedProviderMatches
           .toSorted((a, b) => {
             const scoreDelta = a.score - b.score;
             if (scoreDelta !== 0) {
diff --git a/apps/web/src/components/chat/TraitsPicker.tsx b/apps/web/src/components/chat/TraitsPicker.tsx
index 76ff055a594..5a32a780289 100644
--- a/apps/web/src/components/chat/TraitsPicker.tsx
+++ b/apps/web/src/components/chat/TraitsPicker.tsx
@@ -381,22 +381,23 @@ export const TraitsPicker = memo(function TraitsPicker({
     return null;
   }
 
-  const triggerLabel =
-    descriptors
-      .map((descriptor) => {
-        if (ultrathinkPromptControlled && descriptor.id === primarySelectDescriptor?.id) {
-          return "Ultrathink";
-        }
-        if (descriptor.type === "boolean") {
-          if (descriptor.id === "fastMode") {
-            return descriptor.currentValue === true ? "Fast" : "Normal";
-          }
-          return `${descriptor.label} ${descriptor.currentValue === true ? "On" : "Off"}`;
-        }
-        return getProviderOptionCurrentLabel(descriptor);
-      })
-      .filter((label): label is string => typeof label === "string" && label.length > 0)
-      .join(" · ") || "";
+  const triggerLabels: Array<string> = [];
+  for (const descriptor of descriptors) {
+    const label =
+      ultrathinkPromptControlled && descriptor.id === primarySelectDescriptor?.id
+        ? "Ultrathink"
+        : descriptor.type === "boolean"
+          ? descriptor.id === "fastMode"
+            ? descriptor.currentValue === true
+              ? "Fast"
+              : "Normal"
+            : `${descriptor.label} ${descriptor.currentValue === true ? "On" : "Off"}`
+          : getProviderOptionCurrentLabel(descriptor);
+    if (typeof label === "string" && label.length > 0) {
+      triggerLabels.push(label);
+    }
+  }
+  const triggerLabel = triggerLabels.join(" · ");
 
   const isCodexStyle = provider === "codex";
 
diff --git a/apps/web/src/components/chat/modelPickerSearch.ts b/apps/web/src/components/chat/modelPickerSearch.ts
index d3a954ee4fa..ff265e4a65a 100644
--- a/apps/web/src/components/chat/modelPickerSearch.ts
+++ b/apps/web/src/components/chat/modelPickerSearch.ts
@@ -68,9 +68,13 @@ export function scoreModelPickerSearch(
   let score = 0;
 
   for (const token of tokens) {
-    const tokenScores = fields
-      .map((field, index) => scoreModelPickerSearchToken(field, token, index * 10))
-      .filter((fieldScore): fieldScore is number => fieldScore !== null);
+    const tokenScores: Array<number> = [];
+    for (let index = 0; index < fields.length; index += 1) {
+      const fieldScore = scoreModelPickerSearchToken(fields[index]!, token, index * 10);
+      if (fieldScore !== null) {
+        tokenScores.push(fieldScore);
+      }
+    }
 
     if (tokenScores.length === 0) {
       return null;
diff --git a/apps/web/src/components/chat/userMessageTerminalContexts.ts b/apps/web/src/components/chat/userMessageTerminalContexts.ts
index 978210a53f4..fecc8200dd9 100644
--- a/apps/web/src/components/chat/userMessageTerminalContexts.ts
+++ b/apps/web/src/components/chat/userMessageTerminalContexts.ts
@@ -7,11 +7,14 @@ export function buildInlineTerminalContextText(
     header: string;
   }>,
 ): string {
-  return contexts
-    .map((context) => context.header.trim())
-    .filter((header) => header.length > 0)
-    .map(formatInlineTerminalContextLabel)
-    .join(" ");
+  const labels: Array<string> = [];
+  for (const context of contexts) {
+    const header = context.header.trim();
+    if (header.length > 0) {
+      labels.push(formatInlineTerminalContextLabel(header));
+    }
+  }
+  return labels.join(" ");
 }
 
 export function formatInlineTerminalContextLabel(header: string): string {
diff --git a/apps/web/src/components/settings/ConnectionsSettings.tsx b/apps/web/src/components/settings/ConnectionsSettings.tsx
index 17dc177a981..48c789a2fb6 100644
--- a/apps/web/src/components/settings/ConnectionsSettings.tsx
+++ b/apps/web/src/components/settings/ConnectionsSettings.tsx
@@ -534,21 +534,27 @@ const PairingLinkListRow = memo(function PairingLinkListRow({
     const endpoint = selectPairingEndpoint(endpoints, defaultEndpointKey);
     return endpoint ? resolveAdvertisedEndpointPairingUrl(endpoint, pairingLink.credential) : null;
   }, [defaultEndpointKey, endpoints, pairingLink.credential]);
-  const endpointCopyOptions = useMemo(
-    () =>
-      endpoints
-        .filter((endpoint) => endpoint.status !== "unavailable")
-        .map((endpoint) => {
-          const url = resolveAdvertisedEndpointPairingUrl(endpoint, pairingLink.credential);
-          return {
-            key: endpointDefaultPreferenceKey(endpoint),
-            label: endpoint.label,
-            url,
-            detail: isHostedAppPairingUrl(url) ? "Hosted app link" : "Backend pairing URL",
-          };
-        }),
-    [endpoints, pairingLink.credential],
-  );
+  const endpointCopyOptions = useMemo(() => {
+    const options: Array<{
+      readonly key: string;
+      readonly label: string;
+      readonly url: string;
+      readonly detail: string;
+    }> = [];
+    for (const endpoint of endpoints) {
+      if (endpoint.status === "unavailable") {
+        continue;
+      }
+      const url = resolveAdvertisedEndpointPairingUrl(endpoint, pairingLink.credential);
+      options.push({
+        key: endpointDefaultPreferenceKey(endpoint),
+        label: endpoint.label,
+        url,
+        detail: isHostedAppPairingUrl(url) ? "Hosted app link" : "Backend pairing URL",
+      });
+    }
+    return options;
+  }, [endpoints, pairingLink.credential]);
   const shareablePairingUrl =
     endpointPairingUrl ??
     (endpointUrl != null && endpointUrl !== ""
diff --git a/apps/web/src/components/settings/KeybindingsSettings.logic.ts b/apps/web/src/components/settings/KeybindingsSettings.logic.ts
index bb6b92048ac..da54e86e42e 100644
--- a/apps/web/src/components/settings/KeybindingsSettings.logic.ts
+++ b/apps/web/src/components/settings/KeybindingsSettings.logic.ts
@@ -140,14 +140,16 @@ export function keybindingConflictLabels(
   input: { readonly rowId: string; readonly key: string; readonly when: string },
 ): ReadonlyArray<string> {
   if (input.key.trim().length === 0) return [];
-  const conflicts = rows
-    .filter(
-      (candidate) =>
-        candidate.id !== input.rowId &&
-        candidate.key === input.key &&
-        conflictsWithWhen(candidate.when, input.when),
-    )
-    .map((candidate) => commandLabel(candidate.command));
+  const conflicts: Array<string> = [];
+  for (const candidate of rows) {
+    if (
+      candidate.id !== input.rowId &&
+      candidate.key === input.key &&
+      conflictsWithWhen(candidate.when, input.when)
+    ) {
+      conflicts.push(commandLabel(candidate.command));
+    }
+  }
   return [...new Set(conflicts)].toSorted();
 }
 
@@ -274,12 +276,13 @@ export function commandLabel(command: KeybindingCommand): string {
 }
 
 function titleCaseCommandSegment(segment: string): string {
-  return segment
-    .replace(/([a-z0-9])([A-Z])/g, "$1 $2")
-    .split(/[-_\s]+/)
-    .filter(Boolean)
-    .map((part) => part.slice(0, 1).toUpperCase() + part.slice(1))
-    .join(" ");
+  const words: Array<string> = [];
+  for (const part of segment.replace(/([a-z0-9])([A-Z])/g, "$1 $2").split(/[-_\s]+/)) {
+    if (part.length > 0) {
+      words.push(part.slice(0, 1).toUpperCase() + part.slice(1));
+    }
+  }
+  return words.join(" ");
 }
 
 export function normalizeShortcutKeyToken(key: string): string | null {
diff --git a/apps/web/src/components/settings/ProviderInstanceCard.tsx b/apps/web/src/components/settings/ProviderInstanceCard.tsx
index 430ec3637e0..ba3feddb462 100644
--- a/apps/web/src/components/settings/ProviderInstanceCard.tsx
+++ b/apps/web/src/components/settings/ProviderInstanceCard.tsx
@@ -10,6 +10,8 @@ import {
   Trash2Icon,
   XIcon,
 } from "lucide-react";
+import * as Arr from "effect/Array";
+import * as Result from "effect/Result";
 import { useEffect, useState, type ReactNode } from "react";
 import {
   isProviderDriverKind,
@@ -118,9 +120,9 @@ export function deriveProviderModelsForDisplay(input: {
   readonly customModels: ReadonlyArray<string>;
 }): ReadonlyArray<ServerProviderModel> {
   const liveCustomModelsBySlug = new Map(
-    (input.liveModels ?? [])
-      .filter((model) => model.isCustom)
-      .map((model) => [model.slug, model] as const),
+    Arr.filterMap(input.liveModels ?? [], (model) =>
+      model.isCustom ? Result.succeed([model.slug, model] as const) : Result.failVoid,
+    ),
   );
   const serverModels = input.liveModels?.filter((model) => !model.isCustom) ?? [];
   const customModels = input.customModels.map(
diff --git a/apps/web/src/components/settings/SettingsPanels.tsx b/apps/web/src/components/settings/SettingsPanels.tsx
index e7f21da4809..76d5d34c355 100644
--- a/apps/web/src/components/settings/SettingsPanels.tsx
+++ b/apps/web/src/components/settings/SettingsPanels.tsx
@@ -14,8 +14,10 @@ import {
 import { scopeThreadRef } from "@t3tools/client-runtime";
 import { DEFAULT_UNIFIED_SETTINGS } from "@t3tools/contracts/settings";
 import { createModelSelection } from "@t3tools/shared/model";
+import * as Arr from "effect/Array";
 import * as Duration from "effect/Duration";
 import * as Equal from "effect/Equal";
+import * as Result from "effect/Result";
 import { APP_VERSION, HOSTED_APP_CHANNEL, HOSTED_APP_CHANNEL_LABEL } from "../../branding";
 import {
   canCheckForUpdate,
@@ -1143,7 +1145,12 @@ export function ProviderSettingsPanel() {
     nextFavoriteModels: ReadonlyArray<string>,
   ) => {
     const favoriteModels = [
-      ...new Set(nextFavoriteModels.map((slug) => slug.trim()).filter((slug) => slug.length > 0)),
+      ...new Set(
+        Arr.filterMap(nextFavoriteModels, (slug) => {
+          const trimmedSlug = slug.trim();
+          return trimmedSlug.length > 0 ? Result.succeed(trimmedSlug) : Result.failVoid;
+        }),
+      ),
     ];
     updateSettings({
       favorites: [
@@ -1249,9 +1256,9 @@ export function ProviderSettingsPanel() {
             hiddenModels: [],
             modelOrder: [],
           };
-          const favoriteModels = (settings.favorites ?? [])
-            .filter((favorite) => favorite.provider === row.instanceId)
-            .map((favorite) => favorite.model);
+          const favoriteModels = Arr.filterMap(settings.favorites ?? [], (favorite) =>
+            favorite.provider === row.instanceId ? Result.succeed(favorite.model) : Result.failVoid,
+          );
           const resetLabel = driverOption?.label ?? String(row.driver);
           const headerAction =
             row.isDefault && row.isDirty ? (
@@ -1369,21 +1376,30 @@ export function ArchivedThreadsPanel() {
       })),
     );
 
-    return [...projectsByEnvironmentAndId.values()]
-      .map((project) => ({
-        project,
-        threads: threads
-          .filter(
-            (thread) =>
-              thread.projectId === project.id && thread.environmentId === project.environmentId,
-          )
-          .toSorted((left, right) => {
+    const archivedProjects = Array.from(projectsByEnvironmentAndId.values());
+    const groups: Array<{
+      readonly project: (typeof archivedProjects)[number];
+      readonly threads: Array<(typeof threads)[number]>;
+    }> = [];
+    for (const project of archivedProjects) {
+      const projectThreads: Array<(typeof threads)[number]> = [];
+      for (const thread of threads) {
+        if (thread.projectId === project.id && thread.environmentId === project.environmentId) {
+          projectThreads.push(thread);
+        }
+      }
+      if (projectThreads.length > 0) {
+        groups.push({
+          project,
+          threads: projectThreads.toSorted((left, right) => {
             const leftKey = left.archivedAt ?? left.createdAt;
             const rightKey = right.archivedAt ?? right.createdAt;
             return rightKey.localeCompare(leftKey) || right.id.localeCompare(left.id);
           }),
-      }))
-      .filter((group) => group.threads.length > 0);
+        });
+      }
+    }
+    return groups;
   }, [archivedSnapshots]);
 
   const handleArchivedThreadContextMenu = useCallback(
diff --git a/apps/web/src/composerDraftStore.ts b/apps/web/src/composerDraftStore.ts
index 5c90197a406..3de3b5d706d 100644
--- a/apps/web/src/composerDraftStore.ts
+++ b/apps/web/src/composerDraftStore.ts
@@ -451,11 +451,13 @@ function cloneModelSelection(selection: ModelSelection): DeepMutable<ModelSelect
 function compactModelSelectionByProvider(
   selections: Partial<Record<ProviderInstanceId, ModelSelection>>,
 ): DeepMutable<Record<ProviderInstanceId, ModelSelection>> {
-  return Object.fromEntries(
-    Object.entries(selections)
-      .filter((entry): entry is [string, ModelSelection] => entry[1] !== undefined)
-      .map(([provider, selection]) => [provider, cloneModelSelection(selection)]),
-  ) as DeepMutable<Record<ProviderInstanceId, ModelSelection>>;
+  const entries: Array<[string, DeepMutable<ModelSelection>]> = [];
+  for (const [provider, selection] of Object.entries(selections)) {
+    if (selection !== undefined) {
+      entries.push([provider, cloneModelSelection(selection)]);
+    }
+  }
+  return Object.fromEntries(entries) as DeepMutable<Record<ProviderInstanceId, ModelSelection>>;
 }
 
 const EMPTY_PERSISTED_DRAFT_STORE_STATE = Object.freeze<PersistedComposerDraftStoreState>({
@@ -1809,9 +1811,12 @@ function verifyPersistedAttachments(
     const persistedAttachments = attachments.filter(
       (attachment) => imageIdSet.has(attachment.id) && persistedIdSet.has(attachment.id),
     );
-    const nonPersistedImageIds = current.images
-      .map((image) => image.id)
-      .filter((imageId) => !persistedIdSet.has(imageId));
+    const nonPersistedImageIds: string[] = [];
+    for (const image of current.images) {
+      if (!persistedIdSet.has(image.id)) {
+        nonPersistedImageIds.push(image.id);
+      }
+    }
     const nextDraft: ComposerThreadDraftState = {
       ...current,
       persistedAttachments,
diff --git a/apps/web/src/environments/runtime/service.ts b/apps/web/src/environments/runtime/service.ts
index 21a4561beb4..e4df6b9f3cd 100644
--- a/apps/web/src/environments/runtime/service.ts
+++ b/apps/web/src/environments/runtime/service.ts
@@ -1459,10 +1459,12 @@ async function syncSavedEnvironmentConnections(
   records: ReadonlyArray<SavedEnvironmentRecord>,
 ): Promise<void> {
   const expectedEnvironmentIds = new Set(records.map((record) => record.environmentId));
-  const staleEnvironmentIds = [...environmentConnections.values()]
-    .filter((connection) => connection.kind === "saved")
-    .map((connection) => connection.environmentId)
-    .filter((environmentId) => !expectedEnvironmentIds.has(environmentId));
+  const staleEnvironmentIds: EnvironmentId[] = [];
+  for (const connection of environmentConnections.values()) {
+    if (connection.kind !== "saved") continue;
+    if (expectedEnvironmentIds.has(connection.environmentId)) continue;
+    staleEnvironmentIds.push(connection.environmentId);
+  }
 
   await Promise.all(
     staleEnvironmentIds.map((environmentId) => disconnectSavedEnvironment(environmentId)),
diff --git a/apps/web/src/lib/terminalContext.ts b/apps/web/src/lib/terminalContext.ts
index 562fe742a15..ba63fd5a02b 100644
--- a/apps/web/src/lib/terminalContext.ts
+++ b/apps/web/src/lib/terminalContext.ts
@@ -127,19 +127,18 @@ export function buildTerminalContextPreviewTitle(
   if (contexts.length === 0) {
     return null;
   }
-  const previews = contexts
-    .map((context) => {
-      const normalized = normalizeTerminalContextSelection(context);
-      if (!normalized) {
-        return null;
-      }
-      const preview = previewTerminalContextText(normalized.text);
-      return preview.length > 0
+  const previewParts: string[] = [];
+  for (const context of contexts) {
+    const normalized = normalizeTerminalContextSelection(context);
+    if (!normalized) continue;
+    const preview = previewTerminalContextText(normalized.text);
+    previewParts.push(
+      preview.length > 0
         ? `${formatTerminalContextLabel(normalized)}\n${preview}`
-        : formatTerminalContextLabel(normalized);
-    })
-    .filter((value): value is string => value !== null)
-    .join("\n\n");
+        : formatTerminalContextLabel(normalized),
+    );
+  }
+  const previews = previewParts.join("\n\n");
   return previews.length > 0 ? previews : null;
 }
 
@@ -152,9 +151,13 @@ function buildTerminalContextBodyLines(selection: TerminalContextSelection): str
 export function buildTerminalContextBlock(
   contexts: ReadonlyArray<TerminalContextSelection>,
 ): string {
-  const normalizedContexts = contexts
-    .map((context) => normalizeTerminalContextSelection(context))
-    .filter((context): context is TerminalContextSelection => context !== null);
+  const normalizedContexts: TerminalContextSelection[] = [];
+  for (const context of contexts) {
+    const normalized = normalizeTerminalContextSelection(context);
+    if (normalized !== null) {
+      normalizedContexts.push(normalized);
+    }
+  }
   if (normalizedContexts.length === 0) {
     return "";
   }
diff --git a/apps/web/src/modelSelection.ts b/apps/web/src/modelSelection.ts
index 8ba0c8fa5d9..0fcf680b732 100644
--- a/apps/web/src/modelSelection.ts
+++ b/apps/web/src/modelSelection.ts
@@ -14,6 +14,8 @@ import {
 } from "@t3tools/shared/model";
 import { getComposerProviderState } from "./components/chat/composerProviderState";
 import { UnifiedSettings } from "@t3tools/contracts/settings";
+import * as Arr from "effect/Array";
+import * as Result from "effect/Result";
 import {
   getDefaultServerModel,
   getProviderModels,
@@ -150,9 +152,9 @@ export function getAppModelOptions(
   const options: AppModelOption[] = getProviderModels(providers, provider).map(toAppModelOption);
   const seen = new Set(options.map((option) => option.slug));
   const builtInModelSlugs = new Set(
-    getProviderModels(providers, provider)
-      .filter((model) => !model.isCustom)
-      .map((model) => model.slug),
+    Arr.filterMap(getProviderModels(providers, provider), (model) =>
+      model.isCustom ? Result.failVoid : Result.succeed(model.slug),
+    ),
   );
 
   // Read from the default instance's config first (that's where edits
@@ -198,7 +200,9 @@ export function getAppModelOptionsForInstance(
   const options: AppModelOption[] = entry.models.map(toAppModelOption);
   const seen = new Set(options.map((option) => option.slug));
   const builtInModelSlugs = new Set(
-    entry.models.filter((model) => !model.isCustom).map((model) => model.slug),
+    Arr.filterMap(entry.models, (model) =>
+      model.isCustom ? Result.failVoid : Result.succeed(model.slug),
+    ),
   );
 
   const customModels = readInstanceCustomModels(settings, entry.instanceId, entry.driverKind);
diff --git a/apps/web/src/pendingUserInput.ts b/apps/web/src/pendingUserInput.ts
index cdfc73cb815..d3a7a129378 100644
--- a/apps/web/src/pendingUserInput.ts
+++ b/apps/web/src/pendingUserInput.ts
@@ -33,10 +33,14 @@ function normalizeSelectedOptionLabels(value: string[] | undefined): string[] {
     return [];
   }
 
-  const normalized = value
-    .filter((entry): entry is string => typeof entry === "string")
-    .map((entry) => entry.trim())
-    .filter((entry) => entry.length > 0);
+  const normalized: string[] = [];
+  for (const entry of value) {
+    if (typeof entry !== "string") continue;
+    const trimmed = entry.trim();
+    if (trimmed.length > 0) {
+      normalized.push(trimmed);
+    }
+  }
 
   return Array.from(new Set(normalized));
 }
diff --git a/apps/web/src/providerInstances.ts b/apps/web/src/providerInstances.ts
index 6ff0bd1ab98..3ec67c9e25e 100644
--- a/apps/web/src/providerInstances.ts
+++ b/apps/web/src/providerInstances.ts
@@ -66,13 +66,15 @@ export interface ProviderInstanceEntry {
  * will take precedence over this fallback.
  */
 function humanizeInstanceId(instanceId: ProviderInstanceId): string {
-  return instanceId
+  const words: string[] = [];
+  for (const token of instanceId
     .replace(/[_-]+/g, " ")
     .replace(/([a-z])([A-Z])/g, "$1 $2")
-    .split(" ")
-    .filter((token) => token.length > 0)
-    .map((token) => token.charAt(0).toUpperCase() + token.slice(1))
-    .join(" ");
+    .split(" ")) {
+    if (token.length === 0) continue;
+    words.push(token.charAt(0).toUpperCase() + token.slice(1));
+  }
+  return words.join(" ");
 }
 
 function driverKindLabel(driverKind: ProviderDriverKind): string {
diff --git a/apps/web/src/providerSkillPresentation.ts b/apps/web/src/providerSkillPresentation.ts
index fe077cbb191..50adc4a47d6 100644
--- a/apps/web/src/providerSkillPresentation.ts
+++ b/apps/web/src/providerSkillPresentation.ts
@@ -1,11 +1,12 @@
 import type { ServerProviderSkill } from "@t3tools/contracts";
 
 function titleCaseWords(value: string): string {
-  return value
-    .split(/[\s:_-]+/)
-    .filter((segment) => segment.length > 0)
-    .map((segment) => segment.charAt(0).toUpperCase() + segment.slice(1))
-    .join(" ");
+  const words: string[] = [];
+  for (const segment of value.split(/[\s:_-]+/)) {
+    if (segment.length === 0) continue;
+    words.push(segment.charAt(0).toUpperCase() + segment.slice(1));
+  }
+  return words.join(" ");
 }
 
 function normalizePathSeparators(pathValue: string): string {
diff --git a/apps/web/src/session-logic.ts b/apps/web/src/session-logic.ts
index a7767672fa1..5feffe15b09 100644
--- a/apps/web/src/session-logic.ts
+++ b/apps/web/src/session-logic.ts
@@ -385,28 +385,25 @@ export function deriveActivePlanState(
   if (!Array.isArray(rawPlan)) {
     return null;
   }
-  const steps = rawPlan
-    .map((entry) => {
-      if (!entry || typeof entry !== "object") return null;
-      const record = entry as Record<string, unknown>;
-      if (typeof record.step !== "string") {
-        return null;
-      }
-      const status =
-        record.status === "completed" || record.status === "inProgress" ? record.status : "pending";
-      return {
-        step: record.step,
-        status,
-      };
-    })
-    .filter(
-      (
-        step,
-      ): step is {
-        step: string;
-        status: "pending" | "inProgress" | "completed";
-      } => step !== null,
-    );
+  const steps: Array<{
+    step: string;
+    status: "pending" | "inProgress" | "completed";
+  }> = [];
+  for (const entry of rawPlan) {
+    if (!entry || typeof entry !== "object") {
+      continue;
+    }
+    const record = entry as Record<string, unknown>;
+    if (typeof record.step !== "string") {
+      continue;
+    }
+    const status =
+      record.status === "completed" || record.status === "inProgress" ? record.status : "pending";
+    steps.push({
+      step: record.step,
+      status,
+    });
+  }
   if (steps.length === 0) {
     return null;
   }
@@ -485,14 +482,16 @@ export function deriveWorkLogEntries(
   latestTurnId: TurnId | undefined,
 ): WorkLogEntry[] {
   const ordered = [...activities].toSorted(compareActivitiesByOrder);
-  const entries = ordered
-    .filter((activity) => (latestTurnId ? activity.turnId === latestTurnId : true))
-    .filter((activity) => activity.kind !== "tool.started")
-    .filter((activity) => activity.kind !== "task.started")
-    .filter((activity) => activity.kind !== "context-window.updated")
-    .filter((activity) => activity.summary !== "Checkpoint captured")
-    .filter((activity) => !isPlanBoundaryToolActivity(activity))
-    .map(toDerivedWorkLogEntry);
+  const entries: DerivedWorkLogEntry[] = [];
+  for (const activity of ordered) {
+    if (latestTurnId && activity.turnId !== latestTurnId) continue;
+    if (activity.kind === "tool.started") continue;
+    if (activity.kind === "task.started") continue;
+    if (activity.kind === "context-window.updated") continue;
+    if (activity.summary === "Checkpoint captured") continue;
+    if (isPlanBoundaryToolActivity(activity)) continue;
+    entries.push(toDerivedWorkLogEntry(activity));
+  }
   return collapseDerivedWorkLogEntries(entries).map(
     ({ activityKind: _activityKind, collapseKey: _collapseKey, ...entry }) => entry,
   );
@@ -834,9 +833,13 @@ function formatCommandValue(value: unknown): string | null {
   if (!Array.isArray(value)) {
     return null;
   }
-  const parts = value
-    .map((entry) => asTrimmedString(entry))
-    .filter((entry): entry is string => entry !== null);
+  const parts: Array<string> = [];
+  for (const entry of value) {
+    const part = asTrimmedString(entry);
+    if (part !== null) {
+      parts.push(part);
+    }
+  }
   if (parts.length === 0) {
     return null;
   }
@@ -920,10 +923,13 @@ function normalizePreviewForComparison(value: string | null | undefined): string
 }
 
 function summarizeToolTextOutput(value: string): string | null {
-  const lines = value
-    .split(/\r?\n/u)
-    .map((line) => normalizeInlinePreview(line))
-    .filter((line) => line.length > 0);
+  const lines: Array<string> = [];
+  for (const rawLine of value.split(/\r?\n/u)) {
+    const line = normalizeInlinePreview(rawLine);
+    if (line.length > 0) {
+      lines.push(line);
+    }
+  }
   const firstLine = lines.find((line) => line !== "```");
   if (firstLine) {
     return truncateInlinePreview(firstLine);
diff --git a/packages/shared/src/git.ts b/packages/shared/src/git.ts
index a813cfe4637..ae50b148835 100644
--- a/packages/shared/src/git.ts
+++ b/packages/shared/src/git.ts
@@ -6,6 +6,8 @@ import type {
   VcsStatusResult,
   VcsStatusStreamEvent,
 } from "@t3tools/contracts";
+import * as Arr from "effect/Array";
+import * as Result from "effect/Result";
 import { detectSourceControlProviderFromRemoteUrl } from "./sourceControl.ts";
 
 export const WORKTREE_BRANCH_PREFIX = "t3code";
@@ -172,7 +174,9 @@ export function dedupeRemoteBranchesWithLocalMatches(
   refs: ReadonlyArray<VcsRef>,
 ): ReadonlyArray<VcsRef> {
   const localBranchNames = new Set(
-    refs.filter((refName) => !refName.isRemote).map((refName) => refName.name),
+    Arr.filterMap(refs, (refName) =>
+      refName.isRemote ? Result.failVoid : Result.succeed(refName.name),
+    ),
   );
 
   return refs.filter((refName) => {
diff --git a/packages/shared/src/observability.ts b/packages/shared/src/observability.ts
index 4a49545e393..1fd75cf4ac6 100644
--- a/packages/shared/src/observability.ts
+++ b/packages/shared/src/observability.ts
@@ -184,11 +184,13 @@ function normalizeJsonValue(value: unknown, seen: WeakSet<object> = new WeakSet(
 export function compactTraceAttributes(
   attributes: Readonly<Record<string, unknown>>,
 ): TraceAttributes {
-  return Object.fromEntries(
-    Object.entries(attributes)
-      .filter(([, value]) => value !== undefined)
-      .map(([key, value]) => [key, normalizeJsonValue(value)]),
-  );
+  const entries: Array<[string, unknown]> = [];
+  for (const [key, value] of Object.entries(attributes)) {
+    if (value !== undefined) {
+      entries.push([key, normalizeJsonValue(value)]);
+    }
+  }
+  return Object.fromEntries(entries);
 }
 
 function formatTraceExit(exit: Exit.Exit<unknown, unknown>): EffectTraceRecord["exit"] {
diff --git a/packages/shared/src/semver.ts b/packages/shared/src/semver.ts
index de213764504..1a73e33042f 100644
--- a/packages/shared/src/semver.ts
+++ b/packages/shared/src/semver.ts
@@ -9,10 +9,13 @@ const SEMVER_NUMBER_SEGMENT = /^\d+$/;
 
 export function normalizeSemverVersion(version: string): string {
   const [main, prerelease] = version.trim().split("-", 2);
-  const segments = (main ?? "")
-    .split(".")
-    .map((segment) => segment.trim())
-    .filter((segment) => segment.length > 0);
+  const segments: string[] = [];
+  for (const segment of (main ?? "").split(".")) {
+    const trimmed = segment.trim();
+    if (trimmed.length > 0) {
+      segments.push(trimmed);
+    }
+  }
 
   if (segments.length === 2) {
     segments.push("0");
@@ -52,14 +55,24 @@ export function parseSemver(value: string): ParsedSemver | null {
     major,
     minor,
     patch,
-    prerelease:
-      prerelease
-        ?.split(".")
-        .map((segment) => segment.trim())
-        .filter((segment) => segment.length > 0) ?? [],
+    prerelease: parsePrereleaseSegments(prerelease),
   };
 }
 
+function parsePrereleaseSegments(prerelease: string | undefined): ReadonlyArray<string> {
+  if (prerelease === undefined) {
+    return [];
+  }
+  const segments: string[] = [];
+  for (const segment of prerelease.split(".")) {
+    const trimmed = segment.trim();
+    if (trimmed.length > 0) {
+      segments.push(trimmed);
+    }
+  }
+  return segments;
+}
+
 function comparePrereleaseIdentifier(left: string, right: string): number {
   const leftNumeric = SEMVER_NUMBER_SEGMENT.test(left);
   const rightNumeric = SEMVER_NUMBER_SEGMENT.test(right);
diff --git a/packages/shared/src/shell.ts b/packages/shared/src/shell.ts
index 0572aaf989a..c88ccc10d2a 100644
--- a/packages/shared/src/shell.ts
+++ b/packages/shared/src/shell.ts
@@ -321,11 +321,12 @@ function resolveWindowsPathExtensions(env: NodeJS.ProcessEnv): ReadonlyArray<str
   const fallback = [".COM", ".EXE", ".BAT", ".CMD"];
   if (!rawValue) return fallback;
 
-  const parsed = rawValue
-    .split(";")
-    .map((entry) => entry.trim())
-    .filter((entry) => entry.length > 0)
-    .map((entry) => (entry.startsWith(".") ? entry.toUpperCase() : `.${entry.toUpperCase()}`));
+  const parsed: string[] = [];
+  for (const entry of rawValue.split(";")) {
+    const trimmed = entry.trim();
+    if (trimmed.length === 0) continue;
+    parsed.push(trimmed.startsWith(".") ? trimmed.toUpperCase() : `.${trimmed.toUpperCase()}`);
+  }
   return parsed.length > 0 ? Array.from(new Set(parsed)) : fallback;
 }
 
@@ -397,10 +398,13 @@ export function resolveCommandPath(
 
   const pathValue = resolvePathEnvironmentVariable(env);
   if (pathValue.length === 0) return null;
-  const pathEntries = pathValue
-    .split(pathDelimiterForPlatform(platform))
-    .map((entry) => stripWrappingQuotes(entry.trim()))
-    .filter((entry) => entry.length > 0);
+  const pathEntries: string[] = [];
+  for (const entry of pathValue.split(pathDelimiterForPlatform(platform))) {
+    const pathEntry = stripWrappingQuotes(entry.trim());
+    if (pathEntry.length > 0) {
+      pathEntries.push(pathEntry);
+    }
+  }
 
   for (const pathEntry of pathEntries) {
     for (const candidate of commandCandidates) {
diff --git a/packages/shared/src/toolActivity.ts b/packages/shared/src/toolActivity.ts
index 5e2f18044f5..2fd04e76696 100644
--- a/packages/shared/src/toolActivity.ts
+++ b/packages/shared/src/toolActivity.ts
@@ -22,9 +22,13 @@ function normalizeCommandValue(value: unknown): string | undefined {
   if (!Array.isArray(value)) {
     return undefined;
   }
-  const parts = value
-    .map((entry) => asTrimmedString(entry))
-    .filter((entry): entry is string => entry !== undefined);
+  const parts: string[] = [];
+  for (const entry of value) {
+    const part = asTrimmedString(entry);
+    if (part !== undefined) {
+      parts.push(part);
+    }
+  }
   return parts.length > 0 ? parts.join(" ") : undefined;
 }
 
diff --git a/packages/ssh/src/config.ts b/packages/ssh/src/config.ts
index a8d17946129..3de430c093b 100644
--- a/packages/ssh/src/config.ts
+++ b/packages/ssh/src/config.ts
@@ -15,12 +15,17 @@ function stripInlineComment(line: string): string {
 }
 
 function splitDirectiveArgs(value: string): ReadonlyArray<string> {
-  return value
+  const args: Array<string> = [];
+  for (const rawEntry of value
     .replace(/=(?!=)/gu, " ")
     .trim()
-    .split(/\s+/u)
-    .map((entry) => entry.trim())
-    .filter((entry) => entry.length > 0);
+    .split(/\s+/u)) {
+    const entry = rawEntry.trim();
+    if (entry.length > 0) {
+      args.push(entry);
+    }
+  }
+  return args;
 }
 
 function expandHomePath(input: string, homeDir: string): string {
diff --git a/packages/tailscale/src/tailscale.ts b/packages/tailscale/src/tailscale.ts
index c40cd54fc44..c8d9cab462d 100644
--- a/packages/tailscale/src/tailscale.ts
+++ b/packages/tailscale/src/tailscale.ts
@@ -112,11 +112,14 @@ export const parseTailscaleStatus = (
     Effect.mapError((cause) => new TailscaleStatusParseError({ cause })),
     Effect.map((parsed) => {
       const rawIps = parsed.Self?.TailscaleIPs;
-      const tailnetIpv4Addresses = Array.isArray(rawIps)
-        ? rawIps
-            .filter((address): address is string => typeof address === "string")
-            .filter(isTailscaleIpv4Address)
-        : [];
+      const tailnetIpv4Addresses: Array<string> = [];
+      if (Array.isArray(rawIps)) {
+        for (const address of rawIps) {
+          if (typeof address === "string" && isTailscaleIpv4Address(address)) {
+            tailnetIpv4Addresses.push(address);
+          }
+        }
+      }
 
       return {
         magicDnsName: normalizeMagicDnsName(parsed),