diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 20dc635..7595631 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -1,7 +1,6 @@
 name: CI
 
 on:
-  pull_request:
   workflow_dispatch:
 
 jobs:
@@ -43,6 +42,3 @@ jobs:
 
       - name: Run compiler linker end-to-end tests
         run: npm run test:e2e:compiler
-
-      - name: Run Firefox packaging smoke
-        run: npm run test:browser:firefox
diff --git a/.github/workflows/release-on-version-change.yml b/.github/workflows/release-on-version-change.yml
index 1468561..45f3237 100644
--- a/.github/workflows/release-on-version-change.yml
+++ b/.github/workflows/release-on-version-change.yml
@@ -65,10 +65,6 @@ jobs:
         if: steps.detect_version.outputs.changed == 'true'
         run: npm run test:e2e
 
-      - name: Run Firefox packaging smoke
-        if: steps.detect_version.outputs.changed == 'true'
-        run: npm run test:browser:firefox
-
       - name: Package release artifacts
         if: steps.detect_version.outputs.changed == 'true'
         run: npm run package:release
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index ab5fcc3..6c63cdc 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -81,25 +81,6 @@ jobs:
           node-version-file: .nvmrc
           cache: npm
 
-      - name: Validate Firefox signing credentials
-        env:
-          AMO_JWT_ISSUER: ${{ secrets.AMO_JWT_ISSUER }}
-          AMO_JWT_SECRET: ${{ secrets.AMO_JWT_SECRET }}
-        run: |
-          missing=0
-          case "$AMO_JWT_ISSUER" in
-            (*[![:space:]]*) ;;
-            (*) echo "::error title=Missing Firefox signing secret::AMO_JWT_ISSUER is not configured for the protected release workflow."; missing=1 ;;
-          esac
-          case "$AMO_JWT_SECRET" in
-            (*[![:space:]]*) ;;
-            (*) echo "::error title=Missing Firefox signing secret::AMO_JWT_SECRET is not configured for the protected release workflow."; missing=1 ;;
-          esac
-          if [ "$missing" -ne 0 ]; then
-            echo "Configure both protected AMO Actions secrets before rerunning the release."
-            exit 1
-          fi
-
       - name: Install dependencies
         run: npm ci
 
@@ -124,18 +105,9 @@ jobs:
       - name: Run end-to-end tests
         run: npm run test:e2e
 
-      - name: Run Firefox packaging smoke
-        run: npm run test:browser:firefox
-
       - name: Package release artifacts
         run: npm run package:release
 
-      - name: Sign Firefox unlisted XPI
-        env:
-          AMO_JWT_ISSUER: ${{ secrets.AMO_JWT_ISSUER }}
-          AMO_JWT_SECRET: ${{ secrets.AMO_JWT_SECRET }}
-        run: npm run sign:firefox:unlisted
-
       - name: Publish GitHub release assets
         env:
           GH_TOKEN: ${{ github.token }}
diff --git a/README.md b/README.md
index b39fb94..b2711fe 100644
--- a/README.md
+++ b/README.md
@@ -6,8 +6,8 @@ An in-browser **C++20 IDE** delivered as a Chrome / Chromium extension.
 |---------|--------|
 | Editor | Monaco Editor (the engine behind VS Code) |
 | Compiler | WASM-native Clang (runs entirely in the browser, offline) |
-| Terminal | xterm.js with a bash-like shell and live line input on Chromium and Firefox 153+ |
-| File access | File System Access API on Chromium, fallback open/save/folder flows on Firefox |
+| Terminal | xterm.js with a bash-like shell and live line input on Chromium; Firefox support is deprecated |
+| File access | File System Access API on Chromium; Firefox fallback flows are deprecated |
 | File I/O | `fstream` / `ifstream` / `ofstream` – read and write workspace files at runtime |
 | Standards | C++14 · C++17 · **C++20** (selectable in the toolbar) |
 
@@ -239,7 +239,9 @@ Full feature parity is supported for desktop Chrome, Edge, Brave, and Chromium
 when the browser is based on Chromium 105 or newer. Latest stable is recommended
 for release testing.
 
-Firefox desktop can load the extension, but support remains experimental:
+Firefox desktop support is deprecated. Existing Firefox users may still load the
+extension while migrating to a Chromium-family browser, but Firefox is not a
+supported release or deployment target:
 
 - compile/run, Monaco, and extension-runtime flows are supported
 - Firefox 153+ uses WebAssembly JSPI for live, line-buffered `std::cin`,
@@ -249,8 +251,7 @@ Firefox desktop can load the extension, but support remains experimental:
   Chromium File System Access APIs
 - persistent folder write-back and directory-handle session restore may be
   reduced compared with Chromium-family builds
-- public AMO publication is manual; the protected release workflow generates the
-  Mozilla-signed unlisted XPI for self-distribution
+- Firefox deployment, AMO publication, and automated XPI signing are disabled
 
 Full parity requires:
 
@@ -290,7 +291,7 @@ npm run test:browser:brave
 npm run test:browser:chromium
 ```
 
-Run the Firefox packaging smoke separately:
+Firefox smoke validation is manual-only during the deprecation period:
 
 ```bash
 npm run test:browser:firefox
@@ -370,18 +371,17 @@ npm run package:release
 This writes:
 
 - `release/browser-cpp-chromium-family-v<version>.zip` for Chrome, Edge, Brave, and Chromium
-- `release/firefox-unlisted/*.xpi` after the protected release workflow signs the Firefox unlisted build
 - `release/SHA256SUMS-v<version>.txt`
 - `release/release-manifest-v<version>.json`
 
 The release manifest tracks the browser package matrix:
 
 - Chrome, Edge, Brave, and Chromium map to the same Chromium-family ZIP
-- Firefox has its own manifest, background entry, smoke-tested temporary package, and signing metadata
+- Firefox remains in release metadata as a deprecated, non-publishable target
 
 Chrome, Edge, Brave, and Chromium still share the same MV3 payload. Firefox is
-built from `dist-firefox/` as a separate payload because its manifest and
-background model differ from Chromium; release distribution uses the signed XPI.
+still built from `dist-firefox/` for transition testing because its manifest and
+background model differ from Chromium, but no Firefox artifact is deployed.
 
 Store submission notes should state:
 
@@ -402,16 +402,13 @@ Use `.github/workflows/release.yml` to publish one GitHub Release per
 4. Cleans `dist/` and `release/`
 5. Fetches the Clang toolchain
 6. Runs lint, build, release validation, and E2E checks
-7. Runs Firefox packaging smoke validation
-8. Produces one Chromium-family ZIP plus checksums and release metadata
-9. Signs the Firefox unlisted XPI with protected AMO credentials
-10. Creates or updates GitHub Release `v<version>` and uploads all files under `release/`
+7. Produces one Chromium-family ZIP plus checksums and release metadata
+8. Creates or updates GitHub Release `v<version>` and uploads the maintained artifacts under `release/`
 
 Use `workflow_dispatch` with `force=true` to rebuild and re-upload assets for an
 existing release. The workflow does **not** publish directly to browser stores.
 Store publication and Chromium distribution remain human-owned steps.
-Public AMO publication also remains human-owned even though the unlisted Firefox
-XPI is signed automatically during release.
+Firefox deployment is deprecated and is not part of this workflow.
 
 ### Human-owned deployment instructions
 
@@ -471,19 +468,13 @@ Store compatibility plus Brave-specific validation.
 There is no official Chromium extension store in this workflow; Chromium is a
 manual/GitHub-distributed channel.
 
-#### Firefox
-
-1. Run `npm run test:browser:firefox`.
-2. Review `amo/metadata/listed.json` and update it if the release changes
-   Firefox-facing product behavior or listing copy.
-3. For public AMO publication, build the Firefox package from `dist-firefox/`, then upload it with the metadata manually
-   through the owner-managed listing workflow.
-4. For self-distribution, verify that the protected release workflow produced a
-   signed artifact under `release/firefox-unlisted/`.
-5. Install the signed XPI in Firefox and complete the manual QA checklist
-   in `docs/firefox-stdin-runtime-acceptance.md`, paying special attention to
-   JSPI live stdin and the documented
-   workspace-persistence limitations.
+#### Firefox (deprecated)
+
+Firefox deployment is suspended. Do not publish to AMO, configure AMO signing
+secrets for normal releases, or distribute a Firefox XPI. If migration or
+removal work requires a final compatibility check, run
+`npm run test:browser:firefox` manually and use `dist-firefox/`; this is not a
+release gate.
 
 ### Manual release QA checklist
 
diff --git a/docs/release-playbook.md b/docs/release-playbook.md
index 2333061..a0462c7 100644
--- a/docs/release-playbook.md
+++ b/docs/release-playbook.md
@@ -15,45 +15,53 @@
   - cleans the release workspace
   - fetches the Clang WASM toolchain
   - runs lint, build, and E2E checks
-  - runs Firefox packaging smoke checks
   - packages one shared Chromium-family release ZIP and target metadata
   - uploads the artifacts for review
 
 ## Manual Release Flow
 
 - Review the uploaded artifacts and confirm the version bump is intentional.
-- For Firefox, confirm the Firefox build and AMO/manual-submission metadata are ready before owner handoff.
 - Use the existing tag/manual release workflow for final publication.
 - Publish browser store listings and verify installed updates as required by the target browser.
-- The protected release workflow signs the Firefox unlisted XPI with AMO credentials and uploads it with the other release assets.
+- Firefox support and deployment are deprecated; it is not included in release artifacts or release gates.
 
-### Firefox unlisted-signing credentials
+### Firefox deprecation notice
 
-The protected release workflow requires two GitHub Actions secrets before it
-starts the release build:
+**Status:** Deprecated as of 2026-09-05
 
-- `AMO_JWT_ISSUER`
-- `AMO_JWT_SECRET`
+**Replacement:** Chrome, Edge, Brave, or Chromium builds
 
-Create the AMO API credential pair in Mozilla Add-ons, then store the values as
-repository or protected release-environment secrets with these exact names.
-Keep them unavailable to pull-request workflows, do not put them in source,
-local release artifacts, or logs, and grant only the permissions required for
-Firefox signing. The workflow checks only that each value is present and
-non-blank; it never prints either value.
+**Removal date:** Advisory; Firefox runtime/build code remains temporarily while
+existing users migrate and ownership is assessed.
 
-Rotate both secrets through Mozilla and GitHub when the credential expires or
-is suspected to be exposed. After updating them, use
-`workflow_dispatch` with `force=true` to rerun the protected release. The
-workflow must fail before dependency installation when either secret is absent;
-do not bypass signing or publish an unsigned XPI. If the preflight passes but
-signing fails, inspect the protected workflow's AMO/web-ext error, correct the
-credential or AMO configuration, and rerun the forced release.
+Firefox is no longer a supported deployment target. Do not configure AMO
+credentials for the normal release workflow, publish a Firefox package, or
+expect a signed XPI in GitHub Releases. The existing Firefox build and signing
+commands are transition tooling only and are not automated release steps.
 
-## Firefox Verification Test Plan
+If a maintainer needs a final compatibility check during migration, run
+`npm run test:browser:firefox` manually. It is not a CI or release gate.
 
-Use this plan before declaring Firefox support release-ready or bumping the
-project version for a Firefox-supporting release.
+The future removal follow-up must verify active Firefox usage and ownership,
+provide migration guidance, then remove the Firefox runtime/build paths, tests,
+signing tools, and documentation together.
+
+### General CI
+
+The general CI workflow is manual-only (`workflow_dispatch`) during this
+transition. It does not run automatically on pull requests and does not run the
+deprecated Firefox smoke test. Run it manually when validating a branch.
+
+### Deprecated Firefox signing credentials
+
+No AMO credentials are required by the normal release workflow. If the
+transition tooling is used manually, keep any credentials outside the repository
+and never expose them in pull-request workflows, source, artifacts, or logs.
+
+## Deprecated Firefox Verification Test Plan
+
+Use this only for migration or eventual removal work. It does not qualify
+Firefox for release.
 
 ### Automated gates
 
@@ -67,13 +75,10 @@ Run these commands from a clean checkout in order:
 6. `npm run test:preflight-clang`
 7. `npm run version:check`
 8. `npm run release:check-version`
-9. `npm run test:browser:firefox`
-10. `npm run package:release`
+9. `npm run package:release`
 
 Passing these gates proves that:
 
-- Firefox-specific manifest generation succeeds
-- the Firefox extension package passes `web-ext` lint/build smoke
 - release packaging emits one Chromium-family ZIP and a release manifest that maps Chrome, Edge, Brave, and Chromium to it
 - manifest/package metadata stay version-synchronized
 
@@ -97,27 +102,25 @@ real Firefox desktop build:
    persistence behavior matches reality.
 8. Restart Firefox and verify session/workspace restore behavior matches the
    documented limitations.
-9. Install the signed Firefox XPI and repeat the compile/run sanity check.
+9. Do not install or distribute a signed Firefox XPI; deployment is deprecated.
 
 ### Release decision
 
-The Firefox release gate passes only when:
+The deprecated Firefox migration check passes only when:
 
-- every automated gate above succeeds
+- every applicable automated gate above succeeds
 - manual Firefox runtime QA succeeds
-- no new Firefox-only regressions are found in startup, compile/run, file
-  flows, or packaging
+- no migration-blocking Firefox regressions are found in startup, compile/run,
+  or file flows
 - remaining Firefox limitations are already documented and match observed
   behavior
 
-Do **not** cut the version bump for a Firefox-supporting release if only the
-packaging smoke passes. Runtime validation in Firefox is still required.
+Do **not** present this validation as evidence that Firefox is release-supported.
 
 ## Validation
 
 - `npm run lint`
 - `npm run build`
 - `npm run test:e2e`
-- `npm run test:browser:firefox`
 - `npm run release:check-version`
 - `npm run package:release`
diff --git a/manifest.json b/manifest.json
index aadf546..f50295f 100644
--- a/manifest.json
+++ b/manifest.json
@@ -3,7 +3,7 @@
   "name": "browser.cpp",
   "short_name": "browser.cpp",
   "description": "In-browser C++20 IDE powered by Monaco Editor and WASM Clang",
-  "version": "0.4.7",
+  "version": "0.4.8",
   "minimum_chrome_version": "105",
   "icons": {
     "16": "icons/icon16.png",
diff --git a/package-lock.json b/package-lock.json
index 255c6a4..8033747 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "browser.cpp",
-  "version": "0.4.7",
+  "version": "0.4.8",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "browser.cpp",
-      "version": "0.4.7",
+      "version": "0.4.8",
       "dependencies": {
         "@xterm/addon-fit": "^0.11.0",
         "@xterm/addon-web-links": "^0.12.0",
diff --git a/package.json b/package.json
index 045c8c7..2e5f5c3 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "browser.cpp",
-  "version": "0.4.7",
+  "version": "0.4.8",
   "description": "In-browser C++20 IDE with WASM Clang toolchain",
   "private": true,
   "scripts": {
diff --git a/scripts/e2e-release-packaging.test.mjs b/scripts/e2e-release-packaging.test.mjs
index 835d37c..a80c1e9 100644
--- a/scripts/e2e-release-packaging.test.mjs
+++ b/scripts/e2e-release-packaging.test.mjs
@@ -34,6 +34,20 @@ const releaseWorkflowPath = path.join(
   'workflows',
   'release.yml'
 );
+const ciWorkflowPath = path.join(
+  path.dirname(fileURLToPath(import.meta.url)),
+  '..',
+  '.github',
+  'workflows',
+  'ci.yml'
+);
+const releaseCandidateWorkflowPath = path.join(
+  path.dirname(fileURLToPath(import.meta.url)),
+  '..',
+  '.github',
+  'workflows',
+  'release-on-version-change.yml'
+);
 
 function writeJson(filePath, value) {
   fs.mkdirSync(path.dirname(filePath), { recursive: true });
@@ -124,6 +138,17 @@ test('e2e: release workflow uploads files from nested release directories', () =
   assert.doesNotMatch(workflow, /gh release (?:upload|create)[\s\S]*release\/\*/);
 });
 
+test('e2e: deprecated Firefox is excluded from automated release workflows', () => {
+  const releaseWorkflow = fs.readFileSync(releaseWorkflowPath, 'utf8');
+  const releaseCandidateWorkflow = fs.readFileSync(releaseCandidateWorkflowPath, 'utf8');
+  const ciWorkflow = fs.readFileSync(ciWorkflowPath, 'utf8');
+
+  assert.doesNotMatch(releaseWorkflow, /AMO_JWT_|sign:firefox|test:browser:firefox/);
+  assert.doesNotMatch(releaseCandidateWorkflow, /test:browser:firefox/);
+  assert.match(ciWorkflow, /on:\n {2}workflow_dispatch:/);
+  assert.doesNotMatch(ciWorkflow, /pull_request:|test:browser:firefox/);
+});
+
 test('e2e: release version sync fails on source manifest mismatch', () => {
   const repoRoot = makeRepoFixture();
   writeJson(path.join(repoRoot, 'manifest.json'), {
@@ -255,14 +280,15 @@ test('e2e: release packaging creates one Chromium-family artifact and target map
 
   const firefoxTarget = manifest.targets.find((target) => target.target === 'firefox');
   assert.equal(firefoxTarget.publishable, false);
+  assert.equal(firefoxTarget.deprecated, true);
   assert.equal(firefoxTarget.packageStrategy, 'distinct');
   assert.equal(firefoxTarget.fileName, null);
   assert.equal(
     firefoxTarget.blockReason,
-    'Firefox unsigned ZIP generation is disabled; use the signed unlisted XPI.'
+    'Firefox support and deployment are deprecated; no release artifact is generated.'
   );
-  assert.equal(firefoxTarget.signing.listed, 'manual-owner-submission');
-  assert.equal(firefoxTarget.signing.unlisted, 'required-release-artifact');
+  assert.equal(firefoxTarget.signing.listed, 'deprecated');
+  assert.equal(firefoxTarget.signing.unlisted, 'deprecated');
 
   const chromiumTargets = ['chrome', 'edge', 'brave', 'chromium'];
   for (const targetKey of chromiumTargets) {
diff --git a/scripts/package-extension-release.js b/scripts/package-extension-release.js
index b0aa187..9a50040 100644
--- a/scripts/package-extension-release.js
+++ b/scripts/package-extension-release.js
@@ -293,6 +293,7 @@ function createReleaseArtifacts(options = {}) {
       artifactKey: target.artifactKey,
       payloadGroup: target.payloadGroup,
       publishable: target.publishable,
+      deprecated: target.deprecated || false,
       blockReason: target.blockReason || null,
       notes: target.notes,
       signing: target.signing || null,
diff --git a/scripts/release-targets.js b/scripts/release-targets.js
index 35c97e9..0818b45 100644
--- a/scripts/release-targets.js
+++ b/scripts/release-targets.js
@@ -24,18 +24,19 @@ const TARGETS = Object.freeze([
   {
     key: 'firefox',
     label: 'Firefox',
-    channel: 'Firefox Add-ons / signed XPI',
+    channel: 'Deprecated Firefox support',
     packageStrategy: 'distinct',
     artifactKey: null,
     payloadGroup: 'firefox-webext',
     publishable: false,
-    blockReason: 'Firefox unsigned ZIP generation is disabled; use the signed unlisted XPI.',
+    deprecated: true,
+    blockReason: 'Firefox support and deployment are deprecated; no release artifact is generated.',
     signing: {
-      listed: 'manual-owner-submission',
-      unlisted: 'required-release-artifact',
+      listed: 'deprecated',
+      unlisted: 'deprecated',
     },
     notes:
-      'Firefox uses a browser-specific manifest, background script entry, and a separate packaging/signing flow.',
+      'Firefox code and local validation remain temporarily for migration and possible future removal.',
   },
   {
     key: 'brave',
diff --git a/specs/issue-untracked-20260905-sdlc_planner-disable-firefox-deployment.md b/specs/issue-untracked-20260905-sdlc_planner-disable-firefox-deployment.md
new file mode 100644
index 0000000..911afc3
--- /dev/null
+++ b/specs/issue-untracked-20260905-sdlc_planner-disable-firefox-deployment.md
@@ -0,0 +1,264 @@
+# Feature: Deprecate Firefox support and disable deployment
+
+## Feature Description
+
+Mark Firefox support as deprecated and remove it from automated release and CI
+paths. Firefox-specific code and local validation may remain temporarily for
+existing users and a possible future removal, but Firefox is no longer a
+supported deployment target or a normal pull-request quality gate. Chromium-
+family release artifacts and deployment behavior must remain unchanged.
+
+The repository's general CI workflow will become manually triggered only. The
+release-candidate workflow must also stop treating Firefox validation as a
+release gate.
+
+## User Story
+
+As a release maintainer
+I want Firefox support and deployment clearly marked as deprecated
+So that releases and routine CI focus on maintained Chromium-family targets
+without implying Firefox receives ongoing support.
+
+## Problem Statement
+
+The protected release workflow currently requires `AMO_JWT_ISSUER` and
+`AMO_JWT_SECRET`, runs Firefox packaging smoke validation, and signs an unlisted
+XPI before uploading every release directory. The general CI workflow runs on
+pull requests and includes Firefox smoke validation. README and the release
+playbook describe Firefox as an active distribution channel.
+
+The release metadata already excludes Firefox from the publishable ZIP artifact
+set, but the workflow still performs Firefox signing and publishes the resulting
+XPI. This creates an unnecessary release dependency and leaves the deployment
+state inconsistent across workflows, scripts, tests, and documentation.
+
+## Solution Statement
+
+1. Remove Firefox signing and Firefox deployment-specific steps from the
+   protected release workflow.
+2. Change `.github/workflows/ci.yml` to `workflow_dispatch` only, removing its
+   automatic pull-request trigger and Firefox smoke step from routine CI.
+3. Remove Firefox smoke validation from the release-candidate workflow so a
+   version-bump PR is not gated by deprecated Firefox support.
+4. Update release metadata, tests, and documentation to identify Firefox as
+   deprecated and ensure releases contain only Chromium-family artifacts.
+5. Retain Firefox source/runtime code and local commands temporarily, with a
+   documented follow-up path for complete removal after usage/ownership review.
+
+## Relevant Files
+
+- `.github/workflows/release.yml` - Remove AMO secret validation, Firefox signing,
+  and any release-upload assumptions tied to the signed XPI.
+- `.github/workflows/release-on-version-change.yml` - Remove Firefox smoke
+  validation from release-candidate gating and keep candidate uploads limited to
+  maintained Chromium-family artifacts.
+- `.github/workflows/ci.yml` - Change the trigger to `workflow_dispatch` only and
+  remove the Firefox smoke step from the manually run general CI workflow.
+- `scripts/release-targets.js` - Represent Firefox as disabled for deployment with
+  an explicit stable reason and no publishable artifact contract.
+- `scripts/package-extension-release.js` - Ensure release manifests, checksums,
+  stale-artifact cleanup, and payload handling cannot include Firefox deployment
+  artifacts.
+- `scripts/e2e-release-packaging.test.mjs` - Update regression assertions for the
+  disabled deployment state and verify no Firefox asset is emitted.
+- `scripts/sign-firefox-unlisted.mjs` and `scripts/sign-firefox-listed.mjs` -
+  Retain temporarily only as deprecated/manual tools, or remove them in a later
+  cleanup once Firefox users and maintainers have been assessed.
+- `scripts/firefox-webext.js` - Retain shared Firefox build/smoke helpers if
+  Firefox validation remains supported.
+- `package.json` - Keep Firefox commands only as explicitly deprecated/manual
+  commands during the transition; do not invoke them from automated release or
+  routine CI.
+- `README.md` - Revise release workflow and Firefox deployment instructions to
+  state that automated deployment is disabled and remove obsolete AMO/XPI
+  release steps.
+- `docs/release-playbook.md` - Document the disabled state, deferred re-enable
+  requirements, and the remaining Firefox validation path.
+
+### New Files
+
+None expected.
+
+## Implementation Plan
+
+### Phase 1: Foundation
+
+- Confirm the deprecation status, effective date, owner, and whether a future
+  removal date is advisory or compulsory.
+- Identify the GitHub Issue that will be the source of truth. If none exists,
+  create one before implementation and link the eventual PR with `Closes #<id>`.
+- Inventory active Firefox consumers/owners as far as the repository can show and
+  document the migration target: Chromium, Edge, Brave, or Chromium builds.
+- Assert the desired post-change contract: one Chromium-family ZIP, checksums,
+  and release manifest; no signed Firefox XPI or Firefox deployment metadata in
+  uploaded release directories.
+
+### Phase 2: Core Implementation
+
+- Update `.github/workflows/release.yml` to remove AMO credential validation,
+  Firefox smoke validation, and the `sign:firefox:unlisted` step. Keep the
+  normal build/package/release flow fail-closed for missing Chromium artifacts.
+- Update `.github/workflows/ci.yml` so its only event is `workflow_dispatch` and
+  remove its Firefox smoke step.
+- Update `.github/workflows/release-on-version-change.yml` to remove its Firefox
+  smoke step and ensure candidate uploads contain only maintained artifacts.
+- Update release target metadata and packaging logic so Firefox is represented as
+  disabled/non-publishable without requiring `dist-firefox` for a deployable
+  release, while preserving Chromium-family payload generation.
+- Add or revise release-package tests covering the absence of Firefox artifacts,
+  absence of AMO-signing requirements, and preservation of Chromium artifacts.
+- Mark retained Firefox signing and smoke commands as deprecated/manual in
+  documentation and avoid adding new Firefox features during the deprecation
+  period.
+
+### Phase 3: Integration
+
+- Update the release-candidate workflow to match the deployment contract and
+  ensure artifact upload contains no Firefox deployment output.
+- Do not run Firefox smoke testing in normal CI or release-candidate validation.
+  If a maintainer needs a final compatibility check, run it manually using the
+  existing command before removing the deprecated path.
+- Update README and the release playbook, including the future re-enable checklist:
+  AMO credentials, signing workflow, artifact assertions, owner-managed AMO
+  submission, and manual Firefox runtime QA.
+- Review generated release metadata and workflow logs for secret references,
+  stale XPI paths, and contradictory claims.
+
+## Step by Step Tasks
+
+### Step 1: Confirm scope and create the GitHub Issue
+
+- Confirm Firefox is deprecated, not merely deployment-disabled, and record the
+  deprecation date, owner, migration guidance, and any planned removal date.
+- Confirm whether local `sign:firefox:*` commands remain temporarily available
+  as deprecated/manual tools or are removed in this change.
+- Create or identify the GitHub Issue and record this plan and the decision
+  history there before implementation.
+
+### Step 2: Remove automated Firefox deployment
+
+- Remove the AMO secret preflight, Firefox smoke step, and protected `Sign Firefox
+  unlisted XPI` step from `.github/workflows/release.yml`.
+- Remove assumptions that a signed XPI must be present for a normal release.
+- Preserve release permissions and the GitHub Release publication for the
+  Chromium-family artifacts.
+
+### Step 3: Change CI and release-candidate triggers
+
+- Change `.github/workflows/ci.yml` from pull-request plus manual execution to
+  `workflow_dispatch` only.
+- Remove the Firefox smoke step from `.github/workflows/ci.yml`.
+- Remove the Firefox smoke step from `.github/workflows/release-on-version-change.yml`.
+- Verify no automatic workflow still treats Firefox as a required quality gate.
+
+### Step 4: Align release metadata and packaging
+
+- Keep Firefox marked non-publishable with an explicit reason such as deployment
+  being suspended, not an obsolete reason about unsigned ZIP generation.
+- Ensure `package:release` generates no Firefox ZIP/XPI and does not require
+  Firefox output solely for deployment.
+- Prevent stale Firefox artifacts from being accidentally included in checksums
+  or uploaded release assets.
+
+### Step 5: Update regression tests
+
+- Revise `scripts/e2e-release-packaging.test.mjs` to assert the new disabled
+  deployment contract.
+- Retain tests for Chromium artifact naming, checksums, release manifest
+  generation, and version synchronization.
+- Retain Firefox compatibility/build tests only as local/deprecation coverage if
+  they still provide value; they must not be wired into automatic CI or release
+  gates.
+
+### Step 6: Update operator documentation
+
+- Add a clear Firefox deprecation notice to README and the release playbook,
+  including status, reason, effective date, owner, migration target, and whether
+  removal is planned.
+- Remove instructions presenting Firefox as an active automated or owner-managed
+  deployment channel.
+- Document that general CI is manually triggered and no longer validates Firefox
+  automatically.
+- Ensure no documentation instructs maintainers to configure AMO secrets for the
+  normal release workflow while Firefox is deprecated.
+
+### Step 7: Validate the complete change
+
+- Run every command in the Validation Commands section.
+- Inspect the release directory and generated release manifest to confirm no
+  Firefox deployment artifact is present.
+- Review the workflow diff for removed secret exposure and unchanged Chromium
+  release behavior.
+- Update the GitHub Issue with the implementation summary and open a PR linked
+  to the issue for human review.
+
+## Testing Strategy
+
+### Unit and integration tests
+
+- Release target metadata identifies Firefox as disabled/non-publishable.
+- Release packaging emits only the Chromium-family ZIP, checksums, and release
+  manifest.
+- Generated release metadata does not list Firefox as an emitted artifact.
+- Chromium release targets, shared payload mapping, and version checks remain
+  unchanged.
+- Firefox manifest generation and smoke/compatibility tests continue to pass if
+  runtime support remains active.
+
+### Edge Cases
+
+- A stale `release/firefox-unlisted/` directory exists before packaging.
+- AMO secrets are absent: the release must no longer fail solely for that reason.
+- A manually generated Firefox XPI exists locally: it must not be picked up by
+  automatic release upload or checksum generation.
+- Release-candidate artifact upload must match production release artifact scope.
+- Re-enabling deployment later must have an explicit, reviewable path rather than
+  relying on undocumented workflow restoration.
+
+## Acceptance Criteria
+
+- The protected release workflow completes without AMO secrets when all
+  Chromium-family release prerequisites are valid.
+- Normal GitHub Releases contain no automated Firefox XPI or Firefox deployment
+  asset.
+- Release checksums and manifests contain only approved Chromium-family
+  deployment artifacts.
+- Firefox is explicitly marked deprecated in README and
+  `docs/release-playbook.md`, with migration guidance and ownership.
+- `.github/workflows/ci.yml` runs only on manual `workflow_dispatch` and no
+  automatic workflow runs Firefox validation as a required gate.
+- README and `docs/release-playbook.md` do not instruct maintainers to deploy
+  Firefox as part of normal release.
+- Existing Chrome, Edge, Brave, and Chromium release behavior remains intact.
+- The implementation is delivered through a feature branch and PR linked to a
+  GitHub Issue.
+
+## Validation Commands
+
+```bash
+npm ci
+npm run lint
+npm run build
+npm run test:e2e
+npm run test:e2e:compiler
+npm run release:check-version
+npm run package:release
+git diff --check
+```
+
+After packaging, inspect `release/` and the generated
+`release/release-manifest-v<version>.json`; assert that no Firefox XPI or Firefox
+deployment artifact is present and that the Chromium-family ZIP exists. If the
+deprecated Firefox path is being retained temporarily, run
+`npm run test:browser:firefox` manually as an optional smoke check.
+
+## Notes
+
+- Firefox support is deprecated rather than immediately deleted; the follow-up
+  removal decision should verify active usage and ownership before deleting
+  Firefox runtime/build code.
+- No repository changes beyond this plan document have been implemented.
+- Existing unrelated/untracked files in `specs/` must be preserved.
+- If a removal date is later approved, create a follow-up migration/removal plan
+  covering Firefox runtime compatibility, manifests, smoke tests, signing tools,
+  dependencies, and remaining user-facing claims.