fix: update fixture cache to prevent encoding conflicts (#32151)

* fix: update fixture cache to prevent encoding conflicts

* feat: add changelog entry

* empty commmit

* refactor: update separator

* Update packages/driver/src/cy/commands/fixtures.ts

---------

Co-authored-by: Jennifer Shehane <[email protected]>
Co-authored-by: Jennifer Shehane <[email protected]>
Co-authored-by: Bill Glesias <[email protected]>

Author: 3 people

cli/CHANGELOG.md

@@ -7,6 +7,7 @@ _Released 8/12/2025 (PENDING)_
 
 - Fixed an issue where Angular legacy `Output()` decorators were broken when making component instance field references safe. Fixes [#32137](https://github.com/cypress-io/cypress/issues/32137).
 - Upgraded `tmp` from `~0.2.3` to `~0.2.4`. This removes the [CVE-2025-54798](https://github.com/advisories/GHSA-52f5-9888-hmc6) vulnerability being reported in security scans. Addresses [#32176](https://github.com/cypress-io/cypress/issues/32176).
+- Fixed an issue where `.fixture()` calls with different encoding options would return inconsistent content based on execution order. Fixes [#32138](https://github.com/cypress-io/cypress/issues/32138).
 
 ## 14.5.4
 

packages/driver/cypress/e2e/commands/fixtures.cy.js

@@ -265,6 +265,26 @@ describe('src/cy/commands/fixtures', () => {
           })
         })
       })
+
+      it('should respect encoding specification', () => {
+        const fixture = 'comma-separated.csv'
+
+        cy.fixture(fixture, 'base64').then((content) => {
+          cy.wrap(content).should('eq', 'T25lLFR3byxUaHJlZQoxLDIsMwo=')
+          cy.wrap(content).as('base64')
+        })
+
+        cy.fixture(fixture).then((content) => {
+          cy.wrap(content).should('eq', 'One,Two,Three\n1,2,3\n')
+          cy.wrap(content).as('utf8')
+        })
+
+        cy.get('@base64').then((base64) => {
+          cy.get('@utf8').then((utf8) => {
+            cy.wrap(base64).should('not.eq', utf8)
+          })
+        })
+      })
     })
   })
 })

packages/driver/src/cy/commands/fixtures.ts

@@ -28,20 +28,6 @@ export default (Commands, Cypress, cy, state, config) => {
         $errUtils.throwErrByPath('fixture.set_to_false')
       }
 
-      // if we already have cached
-      // this fixture then just return it
-
-      // always return a promise here
-      // to make our interface consistent
-      // for use by other code
-      const resp = cache[fixture]
-
-      if (resp) {
-        // clone the object first to prevent
-        // accidentally mutating the one in the cache
-        return Promise.resolve(clone(resp))
-      }
-
       let options: Record<string, any> = {}
 
       if (_.isObject(args[0])) {
@@ -54,6 +40,14 @@ export default (Commands, Cypress, cy, state, config) => {
         options.encoding = args[0]
       }
 
+      const cacheKey = `${fixture}\u0000${options.encoding || ''}`
+      const cachedContent = cache[cacheKey]
+
+      if (cachedContent) {
+        // Clone the cached content to prevent accidental mutation.
+        return Promise.resolve(clone(cachedContent))
+      }
+
       const timeout = options.timeout ?? Cypress.config('responseTimeout')
 
       // need to remove the current timeout
@@ -81,7 +75,7 @@ export default (Commands, Cypress, cy, state, config) => {
 
         // add the fixture to the cache
         // so it can just be returned next time
-        cache[fixture] = response
+        cache[cacheKey] = response
 
         // Add the filename as a symbol, in case we need it later (such as when storing an alias)
         state('current').set('fileName', basename(fixture))