diff --git a/apps/server/src/orchestration-v2/Adapters/CodexAdapterV2.ts b/apps/server/src/orchestration-v2/Adapters/CodexAdapterV2.ts
index 10b673459e56..7788751b0a60 100644
--- a/apps/server/src/orchestration-v2/Adapters/CodexAdapterV2.ts
+++ b/apps/server/src/orchestration-v2/Adapters/CodexAdapterV2.ts
@@ -2912,15 +2912,15 @@ export const makeCodexAdapterV2 = Effect.fn("makeCodexAdapterV2")(function* (
                       : null,
                   ),
                   Effect.orElseSucceed(() => null),
-                  Effect.flatMap((response) =>
-                    response === null
-                      ? client.raw
-                          .request("thread/resume", {
-                            threadId: input.nativeThreadId,
-                            excludeTurns: true,
-                          })
-                          .pipe(Effect.flatMap(decodeCodexChildModel))
-                      : Effect.succeed(response),
+                  Effect.filterOrElse(
+                    (response) => !(response === null),
+                    (_response) =>
+                      client.raw
+                        .request("thread/resume", {
+                          threadId: input.nativeThreadId,
+                          excludeTurns: true,
+                        })
+                        .pipe(Effect.flatMap(decodeCodexChildModel)),
                   ),
                   Effect.timeout("5 seconds"),
                   Effect.flatMap((response) =>
diff --git a/apps/server/src/orchestration-v2/CommandOutputHub.test.ts b/apps/server/src/orchestration-v2/CommandOutputHub.test.ts
index 06475371f4ce..3740f4f9a240 100644
--- a/apps/server/src/orchestration-v2/CommandOutputHub.test.ts
+++ b/apps/server/src/orchestration-v2/CommandOutputHub.test.ts
@@ -163,8 +163,9 @@ const subscribeFrames = (threadId: ThreadId) =>
 
 const takeFrame = (frames: Queue.Queue<OrchestrationV2CommandOutputFrame | "ended">) =>
   Queue.take(frames).pipe(
-    Effect.flatMap((frame) =>
-      frame === "ended" ? Effect.die("command output stream ended early") : Effect.succeed(frame),
+    Effect.filterOrElse(
+      (frame) => !(frame === "ended"),
+      (_frame) => Effect.die("command output stream ended early"),
     ),
   );
 
diff --git a/apps/server/src/orchestration-v2/Orchestrator.ts b/apps/server/src/orchestration-v2/Orchestrator.ts
index 2a8956913da2..abfdd9127a7b 100644
--- a/apps/server/src/orchestration-v2/Orchestrator.ts
+++ b/apps/server/src/orchestration-v2/Orchestrator.ts
@@ -11981,21 +11981,20 @@ const makeOrchestrator = Effect.fn("orchestrationV2.Orchestrator.layer")(functio
     }
 
     const plan = yield* dispatchOnce(command).pipe(
-      Effect.flatMap((planned) =>
-        planned.events.length > 0 ||
-        command.type === "thread.background-work.settle" ||
-        command.type === "thread.stop" ||
-        command.type === "subagent.stop" ||
-        // A second Stop sharing, or one after the share already ended, is not an error.
-        command.type === "thread.guest-share.close"
-          ? Effect.succeed(planned)
-          : Effect.fail(
-              new OrchestratorDispatchError({
-                commandId: command.commandId,
-                commandType: command.type,
-                cause: "Command produced no domain events.",
-              }),
-            ),
+      Effect.filterOrFail(
+        (planned) =>
+          planned.events.length > 0 ||
+          command.type === "thread.background-work.settle" ||
+          command.type === "thread.stop" ||
+          command.type === "subagent.stop" ||
+          // Closing a share again, or after it ended, is not an error.
+          command.type === "thread.guest-share.close",
+        (_planned) =>
+          new OrchestratorDispatchError({
+            commandId: command.commandId,
+            commandType: command.type,
+            cause: "Command produced no domain events.",
+          }),
       ),
       Effect.catch((cause) =>
         Effect.gen(function* () {
diff --git a/apps/server/src/orchestration-v2/ProviderEventIngestor.ts b/apps/server/src/orchestration-v2/ProviderEventIngestor.ts
index 480c7c6c738e..e9b45b5418b2 100644
--- a/apps/server/src/orchestration-v2/ProviderEventIngestor.ts
+++ b/apps/server/src/orchestration-v2/ProviderEventIngestor.ts
@@ -830,6 +830,7 @@ export const layer: Layer.Layer<
                   ),
                 ),
               ),
+              // @effect-diagnostics-next-line flatMapConditionalToFilterOrFail:off - The predicate narrows the captured event for the subagent update.
               Effect.flatMap((storedEvents) =>
                 storedEvents.length === 0 || input.event.type !== "subagent.updated"
                   ? Effect.succeed(storedEvents)
diff --git a/apps/server/src/orchestration-v2/ThreadManagementService.ts b/apps/server/src/orchestration-v2/ThreadManagementService.ts
index 39baad936ba9..5cda4c23e533 100644
--- a/apps/server/src/orchestration-v2/ThreadManagementService.ts
+++ b/apps/server/src/orchestration-v2/ThreadManagementService.ts
@@ -707,15 +707,14 @@ const make = Effect.gen(function* () {
             cause,
           }),
       ),
-      Effect.flatMap((projection) =>
-        projection.thread.projectId === input.projectId && projection.thread.deletedAt === null
-          ? Effect.succeed(projection)
-          : Effect.fail(
-              new ThreadManagementThreadNotFoundError({
-                projectId: input.projectId,
-                threadId: input.threadId,
-              }),
-            ),
+      Effect.filterOrFail(
+        (projection) =>
+          projection.thread.projectId === input.projectId && projection.thread.deletedAt === null,
+        (_projection) =>
+          new ThreadManagementThreadNotFoundError({
+            projectId: input.projectId,
+            threadId: input.threadId,
+          }),
       ),
     );
 
@@ -734,15 +733,14 @@ const make = Effect.gen(function* () {
             cause,
           }),
       ),
-      Effect.flatMap((projection) =>
-        projection.thread.projectId === input.projectId && projection.thread.deletedAt === null
-          ? Effect.succeed(projection)
-          : Effect.fail(
-              new ThreadManagementThreadNotFoundError({
-                projectId: input.projectId,
-                threadId: input.threadId,
-              }),
-            ),
+      Effect.filterOrFail(
+        (projection) =>
+          projection.thread.projectId === input.projectId && projection.thread.deletedAt === null,
+        (_projection) =>
+          new ThreadManagementThreadNotFoundError({
+            projectId: input.projectId,
+            threadId: input.threadId,
+          }),
       ),
     );
 
diff --git a/apps/server/src/vcs/GitVcsDriverCore.ts b/apps/server/src/vcs/GitVcsDriverCore.ts
index c689d27be226..9b79c2110e28 100644
--- a/apps/server/src/vcs/GitVcsDriverCore.ts
+++ b/apps/server/src/vcs/GitVcsDriverCore.ts
@@ -3961,8 +3961,9 @@ export const makeGitVcsDriverCore = Effect.fn("makeGitVcsDriverCore")(function*
         },
       );
       return run.pipe(
-        Effect.flatMap((result) =>
-          result.exitCode !== 0 && isRefLockFailure(result.stderr) ? run : Effect.succeed(result),
+        Effect.filterOrElse(
+          (result) => !(result.exitCode !== 0 && isRefLockFailure(result.stderr)),
+          (_result) => run,
         ),
       );
     };
diff --git a/packages/client-runtime/src/state/server.ts b/packages/client-runtime/src/state/server.ts
index 0f917e81f1b9..183bb208ffec 100644
--- a/packages/client-runtime/src/state/server.ts
+++ b/packages/client-runtime/src/state/server.ts
@@ -1275,20 +1275,20 @@ export function createServerEnvironmentAtoms<R, E>(
       refreshTrigger: ({ environmentId }) => usageScanSettingsAtom(environmentId),
       execute: (input, emit) =>
         request(WS_METHODS.serverGetUsageSummary, input).pipe(
-          Effect.flatMap((summary) =>
-            summary.sources.some((source) => source.refreshing === true)
-              ? emit(summary).pipe(
-                  Effect.andThen(
-                    request(WS_METHODS.serverGetUsageSummary, { ...input, awaitRefresh: true }),
-                  ),
-                  Effect.catch((error) =>
-                    Effect.logWarning("Could not refresh slow usage sources.").pipe(
-                      Effect.annotateLogs({ ...safeErrorLogAttributes(error) }),
-                      Effect.as(summary),
-                    ),
+          Effect.filterOrElse(
+            (summary) => !summary.sources.some((source) => source.refreshing === true),
+            (summary) =>
+              emit(summary).pipe(
+                Effect.andThen(
+                  request(WS_METHODS.serverGetUsageSummary, { ...input, awaitRefresh: true }),
+                ),
+                Effect.catch((error) =>
+                  Effect.logWarning("Could not refresh slow usage sources.").pipe(
+                    Effect.annotateLogs({ ...safeErrorLogAttributes(error) }),
+                    Effect.as(summary),
                   ),
-                )
-              : Effect.succeed(summary),
+                ),
+              ),
           ),
         ),
     }),
diff --git a/packages/provider-cursor/src/server/driver.ts b/packages/provider-cursor/src/server/driver.ts
index 6937c7aa88a7..b61301390d61 100644
--- a/packages/provider-cursor/src/server/driver.ts
+++ b/packages/provider-cursor/src/server/driver.ts
@@ -225,21 +225,24 @@ export const CursorDriver: ProviderDriver<
           },
           auth.usesApiKey ? "api-key" : "browser",
         ).pipe(
-          Effect.flatMap((snapshot) =>
-            effectiveConfig.enabled &&
-            snapshot.installed &&
-            snapshot.auth.status === "authenticated"
-              ? host.settings.get.pipe(
-                  Effect.flatMap((settings) =>
-                    readCursorUsageLimits(
-                      effectiveConfig,
-                      { ...processEnv, CURSOR_API_KEY: apiKey },
-                      settings.cursorKeychainUsageEnabled,
-                    ),
+          Effect.filterOrElse(
+            (snapshot) =>
+              !(
+                effectiveConfig.enabled &&
+                snapshot.installed &&
+                snapshot.auth.status === "authenticated"
+              ),
+            (snapshot) =>
+              host.settings.get.pipe(
+                Effect.flatMap((settings) =>
+                  readCursorUsageLimits(
+                    effectiveConfig,
+                    { ...processEnv, CURSOR_API_KEY: apiKey },
+                    settings.cursorKeychainUsageEnabled,
                   ),
-                  Effect.map((usageLimits) => ({ ...snapshot, usageLimits })),
-                )
-              : Effect.succeed(snapshot),
+                ),
+                Effect.map((usageLimits) => ({ ...snapshot, usageLimits })),
+              ),
           ),
         ),
       ),
diff --git a/packages/provider-grok/src/server/driver.ts b/packages/provider-grok/src/server/driver.ts
index 23ecf5815853..84cc590c5455 100644
--- a/packages/provider-grok/src/server/driver.ts
+++ b/packages/provider-grok/src/server/driver.ts
@@ -168,16 +168,21 @@ export const GrokDriver: ProviderDriver<GrokSettings, GrokDriverEnv, Path.Path>
     const textGeneration = yield* makeGrokTextGeneration(effectiveConfig, processEnv);
 
     const checkProvider = checkGrokProviderStatus(effectiveConfig, processEnv, cwd).pipe(
-      Effect.flatMap((snapshot) =>
-        effectiveConfig.enabled && snapshot.installed && snapshot.auth.status === "authenticated"
-          ? readGrokAccount(processEnv).pipe(
-              Effect.map(({ email, usageLimits }) => ({
-                ...snapshot,
-                auth: email ? { ...snapshot.auth, email } : snapshot.auth,
-                usageLimits,
-              })),
-            )
-          : Effect.succeed(snapshot),
+      Effect.filterOrElse(
+        (snapshot) =>
+          !(
+            effectiveConfig.enabled &&
+            snapshot.installed &&
+            snapshot.auth.status === "authenticated"
+          ),
+        (snapshot) =>
+          readGrokAccount(processEnv).pipe(
+            Effect.map(({ email, usageLimits }) => ({
+              ...snapshot,
+              auth: email ? { ...snapshot.auth, email } : snapshot.auth,
+              usageLimits,
+            })),
+          ),
       ),
       Effect.map(stampIdentity),
       Effect.provideService(HttpClient.HttpClient, httpClient),
diff --git a/packages/source-control-github/src/server/GitHubPullRequestApi.ts b/packages/source-control-github/src/server/GitHubPullRequestApi.ts
index 1099ee1e094c..49aaaa833186 100644
--- a/packages/source-control-github/src/server/GitHubPullRequestApi.ts
+++ b/packages/source-control-github/src/server/GitHubPullRequestApi.ts
@@ -1578,18 +1578,16 @@ export const make = Effect.gen(function* () {
             ),
           ),
           listActionRequiredRuns(input).pipe(
-            Effect.flatMap((runs) =>
-              runs.length > workflowApprovalLimit
-                ? Effect.fail(
-                    new GitHubWorkflowApprovalRefusedError({
-                      cwd: input.cwd,
-                      number: input.number,
-                      reason: "run-list-truncated",
-                      observedCount: runs.length,
-                      limit: workflowApprovalLimit,
-                    }),
-                  )
-                : Effect.succeed(runs),
+            Effect.filterOrFail(
+              (runs) => !(runs.length > workflowApprovalLimit),
+              (runs) =>
+                new GitHubWorkflowApprovalRefusedError({
+                  cwd: input.cwd,
+                  number: input.number,
+                  reason: "run-list-truncated",
+                  observedCount: runs.length,
+                  limit: workflowApprovalLimit,
+                }),
             ),
           ),
         ],
@@ -1836,40 +1834,41 @@ export const make = Effect.gen(function* () {
           (batch) => batch.items.length > 0 || input.cursor !== undefined || hasQuery,
           () => read(false),
         ),
-        Effect.flatMap((batch) => {
-          if (!stacks || batch.items.length === 0) return Effect.succeed(batch);
-          return Effect.forEach(
-            batch.items,
-            (item) => {
-              const lookup = pullRequestLookup({
-                repository: input.repository,
-                number: item.number,
-              });
-              if (lookup === null) return Effect.succeed(item);
-              return GraphQLResolver.request(lookup, stackMembershipResolver).pipe(
-                Effect.map((result) => {
-                  const pullRequest = result.repository?.pullRequest;
-                  const stack = pullRequest == null ? undefined : toStackMembership(pullRequest);
-                  return stack === undefined ? item : { ...item, stack };
-                }),
-                Effect.catch((error) =>
-                  Effect.logWarning("Pull request stack membership enrichment failed", {
-                    operation: "listPullRequestStackMemberships",
-                    host: input.host,
-                    error: error._tag,
-                  }).pipe(Effect.as(item)),
-                ),
-              );
-            },
-            { concurrency: "unbounded" },
-          ).pipe(
-            Effect.provideService(GitHubGraphQlClient.GitHubGraphQlTarget, {
-              host: input.host,
-              operation: "listPullRequestStackMemberships",
-            }),
-            Effect.map((items) => ({ ...batch, items })),
-          );
-        }),
+        Effect.filterOrElse(
+          (batch) => !stacks || batch.items.length === 0,
+          (batch) =>
+            Effect.forEach(
+              batch.items,
+              (item) => {
+                const lookup = pullRequestLookup({
+                  repository: input.repository,
+                  number: item.number,
+                });
+                if (lookup === null) return Effect.succeed(item);
+                return GraphQLResolver.request(lookup, stackMembershipResolver).pipe(
+                  Effect.map((result) => {
+                    const pullRequest = result.repository?.pullRequest;
+                    const stack = pullRequest == null ? undefined : toStackMembership(pullRequest);
+                    return stack === undefined ? item : { ...item, stack };
+                  }),
+                  Effect.catch((error) =>
+                    Effect.logWarning("Pull request stack membership enrichment failed", {
+                      operation: "listPullRequestStackMemberships",
+                      host: input.host,
+                      error: error._tag,
+                    }).pipe(Effect.as(item)),
+                  ),
+                );
+              },
+              { concurrency: "unbounded" },
+            ).pipe(
+              Effect.provideService(GitHubGraphQlClient.GitHubGraphQlTarget, {
+                host: input.host,
+                operation: "listPullRequestStackMemberships",
+              }),
+              Effect.map((items) => ({ ...batch, items })),
+            ),
+        ),
       );
     },
 
diff --git a/tsconfig.base.json b/tsconfig.base.json
index f4ad537cf4ec..06233a044f66 100644
--- a/tsconfig.base.json
+++ b/tsconfig.base.json
@@ -24,6 +24,7 @@
         "namespaceImportPackages": ["@effect/platform-node", "effect"],
         "effectFn": ["span", "inferred-span", "suggested-span"],
         "diagnosticSeverity": {
+          "flatMapConditionalToFilterOrFail": "error",
           "catchConditionalRefailToCatchIf": "error",
           "tryCatchInEffectGen": "error",
           "schemaStructWithTag": "error",