diff --git a/src/main/startup/os-opened-markdown-files.test.ts b/src/main/startup/os-opened-markdown-files.test.ts
index f174e10d834..c980b6258d2 100644
--- a/src/main/startup/os-opened-markdown-files.test.ts
+++ b/src/main/startup/os-opened-markdown-files.test.ts
@@ -304,3 +304,84 @@ describe('resolveOpenedMarkdownDocuments', () => {
     expect(authorizeExternalPath).not.toHaveBeenCalled()
   })
 })
+
+describe('OsOpenedMarkdownFileState delivery cap', () => {
+  it('stops merging an OS file batch at the pending delivery cap', () => {
+    const state = new OsOpenedMarkdownFileState()
+    const includes = vi.spyOn(Array.prototype, 'includes')
+    const warn = vi.spyOn(console, 'warn').mockImplementation(() => {})
+    let probes: number
+    try {
+      state.captureFilePaths(
+        Array.from({ length: 10000 }, (_, index) => resolve(`/notes/${index}.md`))
+      )
+      probes = includes.mock.calls.length
+    } finally {
+      includes.mockRestore()
+      warn.mockRestore()
+    }
+    expect(probes).toBeLessThan(100)
+    expect(state.consume()).toEqual(
+      Array.from({ length: MAX_PENDING_OS_OPENED_MARKDOWN_FILES }, (_, index) =>
+        resolve(`/notes/${index}.md`)
+      )
+    )
+  })
+
+  // Why: the cap drops files the user explicitly asked to open. Pin which end is
+  // dropped (the tail, in shell order) and that the loss is reported, not silent.
+  it('keeps the first paths in shell order and reports the dropped tail', () => {
+    const state = new OsOpenedMarkdownFileState()
+    const warn = vi.spyOn(console, 'warn').mockImplementation(() => {})
+    const total = MAX_PENDING_OS_OPENED_MARKDOWN_FILES + 8
+    const paths = Array.from({ length: total }, (_, index) =>
+      resolve(`/notes/${String(index).padStart(3, '0')}.md`)
+    )
+    try {
+      expect(state.captureFilePaths(paths)).toBe(true)
+      expect(warn).toHaveBeenCalledWith(
+        expect.stringContaining(`Dropped 8 of ${total} OS-opened markdown files`)
+      )
+    } finally {
+      warn.mockRestore()
+    }
+    expect(state.consume()).toEqual(paths.slice(0, MAX_PENDING_OS_OPENED_MARKDOWN_FILES))
+  })
+
+  it('stays silent for a batch that fits under the cap', () => {
+    const state = new OsOpenedMarkdownFileState()
+    const warn = vi.spyOn(console, 'warn').mockImplementation(() => {})
+    try {
+      state.captureFilePaths(
+        Array.from({ length: MAX_PENDING_OS_OPENED_MARKDOWN_FILES }, (_, index) =>
+          resolve(`/notes/${index}.md`)
+        )
+      )
+      expect(warn).not.toHaveBeenCalled()
+    } finally {
+      warn.mockRestore()
+    }
+  })
+
+  it('reports a drop when an already-full queue rejects a later batch', () => {
+    const state = new OsOpenedMarkdownFileState()
+    const warn = vi.spyOn(console, 'warn').mockImplementation(() => {})
+    try {
+      state.captureFilePaths(
+        Array.from({ length: MAX_PENDING_OS_OPENED_MARKDOWN_FILES }, (_, index) =>
+          resolve(`/first/${index}.md`)
+        )
+      )
+      expect(warn).not.toHaveBeenCalled()
+      state.captureFilePaths([resolve('/second/a.md'), resolve('/second/b.md')])
+      expect(warn).toHaveBeenCalledWith(expect.stringContaining('Dropped 2 of 2'))
+    } finally {
+      warn.mockRestore()
+    }
+    expect(state.consume()).toEqual(
+      Array.from({ length: MAX_PENDING_OS_OPENED_MARKDOWN_FILES }, (_, index) =>
+        resolve(`/first/${index}.md`)
+      )
+    )
+  })
+})
diff --git a/src/main/startup/os-opened-markdown-files.ts b/src/main/startup/os-opened-markdown-files.ts
index dae27fb7a78..144f59fe578 100644
--- a/src/main/startup/os-opened-markdown-files.ts
+++ b/src/main/startup/os-opened-markdown-files.ts
@@ -105,11 +105,23 @@ export class OsOpenedMarkdownFileState {
       return false
     }
     const merged = [...this.pending]
-    for (const filePath of filePaths) {
+    let index = 0
+    for (; index < filePaths.length; index++) {
+      if (merged.length >= MAX_PENDING_OS_OPENED_MARKDOWN_FILES) {
+        break
+      }
+      const filePath = filePaths[index]!
       if (!merged.includes(filePath)) {
         merged.push(filePath)
       }
     }
+    if (index < filePaths.length) {
+      // Why logged: the cap drops the tail of an oversized selection, and a file the
+      // user explicitly asked to open must not vanish without leaving a trace.
+      console.warn(
+        `[os-open] Dropped ${filePaths.length - index} of ${filePaths.length} OS-opened markdown files; the pending queue is capped at ${MAX_PENDING_OS_OPENED_MARKDOWN_FILES}.`
+      )
+    }
     this.pending = merged.slice(0, MAX_PENDING_OS_OPENED_MARKDOWN_FILES)
     publish?.()
     return true