diff --git a/src/providers/copilot.ts b/src/providers/copilot.ts
index 365c1d4..9cb7983 100644
--- a/src/providers/copilot.ts
+++ b/src/providers/copilot.ts
@@ -27,7 +27,7 @@ const toolNameMap: Record<string, string> = {
   write_file: 'Edit',
   edit_file: 'Edit',
   create_file: 'Write',
-  delete_file: 'Edit',
+  delete_file: 'Delete',
   search_files: 'Grep',
   find_files: 'Glob',
   list_directory: 'LS',
@@ -39,6 +39,7 @@ const toolNameMap: Record<string, string> = {
 // Pre-sorted by key length descending so longer/more-specific keys match first
 const modelDisplayEntries = Object.entries(modelDisplayNames).sort((a, b) => b[0].length - a[0].length)
 
+// Fields marked optional document the on-disk schema; they are not read by the parser
 type ToolRequest = {
   name?: string
   toolCallId?: string
@@ -71,6 +72,16 @@ function getCopilotSessionStateDir(override?: string): string {
   return override ?? join(homedir(), '.copilot', 'session-state')
 }
 
+function parseCwd(yaml: string): string | null {
+  const match = yaml.match(/^cwd:\s*(.+)$/m)
+  if (!match?.[1]) return null
+  const raw = match[1]
+    .replace(/\s*#.*$/, '')    // strip trailing comment
+    .replace(/^['"]|['"]$/g, '') // strip surrounding quotes
+    .trim()
+  return raw || null
+}
+
 function createParser(source: SessionSource, seenKeys: Set<string>): SessionParser {
   return {
     async *parse(): AsyncGenerator<ParsedProviderCall> {
@@ -83,7 +94,7 @@ function createParser(source: SessionSource, seenKeys: Set<string>): SessionPars
 
       const sessionId = basename(dirname(source.path))
       const lines = content.split('\n').filter(l => l.trim())
-      let currentModel = 'gpt-4.1'
+      let currentModel = ''
       let pendingUserMessage = ''
 
       for (const line of lines) {
@@ -107,6 +118,8 @@ function createParser(source: SessionSource, seenKeys: Set<string>): SessionPars
         if (event.type === 'assistant.message') {
           const { messageId, outputTokens, toolRequests = [] } = event.data
           if (outputTokens === 0) continue
+          // Skip if no model has been identified yet - avoids silent misattribution
+          if (!currentModel) continue
 
           const dedupKey = `copilot:${sessionId}:${messageId}`
           if (seenKeys.has(dedupKey)) continue
@@ -117,6 +130,8 @@ function createParser(source: SessionSource, seenKeys: Set<string>): SessionPars
             .filter(Boolean)
             .map(n => toolNameMap[n] ?? n)
 
+          // Copilot only logs outputTokens; inputTokens are not available in session logs.
+          // Cost will be lower than actual API cost.
           const costUSD = calculateCost(currentModel, 0, outputTokens, 0, 0, 0)
 
           yield {
@@ -164,8 +179,8 @@ async function discoverSessionsInDir(sessionStateDir: string): Promise<SessionSo
     let project = sessionId
     try {
       const yaml = await readFile(join(sessionStateDir, sessionId, 'workspace.yaml'), 'utf-8')
-      const cwdMatch = yaml.match(/^cwd:\s*(.+)$/m)
-      if (cwdMatch?.[1]) project = basename(cwdMatch[1].trim())
+      const cwd = parseCwd(yaml)
+      if (cwd) project = basename(cwd)
     } catch {}
 
     sources.push({ path: eventsPath, project, provider: 'copilot' })
diff --git a/tests/providers/copilot.test.ts b/tests/providers/copilot.test.ts
index 2e06d6a..eb1b6c5 100644
--- a/tests/providers/copilot.test.ts
+++ b/tests/providers/copilot.test.ts
@@ -142,6 +142,23 @@ describe('copilot provider - JSONL parsing', () => {
     for await (const call of copilot.createSessionParser(source, new Set()).parse()) calls.push(call)
     expect(calls).toHaveLength(0)
   })
+
+  it('skips assistant messages before the first model_change event', async () => {
+    const eventsPath = await createSessionDir('sess-no-model', [
+      assistantMessage({ messageId: 'msg-early', outputTokens: 50 }),
+      modelChange('gpt-4.1'),
+      assistantMessage({ messageId: 'msg-after', outputTokens: 80 }),
+    ])
+
+    const source = { path: eventsPath, project: 'test', provider: 'copilot' }
+    const calls: ParsedProviderCall[] = []
+    for await (const call of copilot.createSessionParser(source, new Set()).parse()) calls.push(call)
+
+    expect(calls).toHaveLength(1)
+    expect(calls[0]!.messageId).toBeUndefined()
+    expect(calls[0]!.outputTokens).toBe(80)
+    expect(calls[0]!.model).toBe('gpt-4.1')
+  })
 })
 
 describe('copilot provider - discoverSessions', () => {
@@ -175,6 +192,19 @@ describe('copilot provider - discoverSessions', () => {
     expect(sessions[0]!.project).toBe('myapp')
   })
 
+  it('strips quotes and trailing comments from workspace.yaml cwd', async () => {
+    const sessionDir = join(tmpDir, 'sess-quoted')
+    await mkdir(sessionDir, { recursive: true })
+    await writeFile(join(sessionDir, 'workspace.yaml'), 'cwd: "/home/user/myapp"  # project root\n')
+    await writeFile(join(sessionDir, 'events.jsonl'), '\n')
+
+    const provider = createCopilotProvider(tmpDir)
+    const sessions = await provider.discoverSessions()
+
+    expect(sessions).toHaveLength(1)
+    expect(sessions[0]!.project).toBe('myapp')
+  })
+
   it('returns empty when directory does not exist', async () => {
     const provider = createCopilotProvider('/nonexistent/path')
     const sessions = await provider.discoverSessions()
@@ -214,4 +244,10 @@ describe('copilot provider - metadata', () => {
     expect(copilot.modelDisplayName('o4-mini')).toBe('o4-mini')
     expect(copilot.modelDisplayName('unknown-model-xyz')).toBe('unknown-model-xyz')
   })
+
+  it('longest-prefix match wins for versioned model IDs', () => {
+    // gpt-5-mini-2026-01-01 must match gpt-5-mini, not gpt-5
+    expect(copilot.modelDisplayName('gpt-5-mini-2026-01-01')).toBe('GPT-5 Mini')
+    expect(copilot.modelDisplayName('gpt-4.1-mini-2026-01-01')).toBe('GPT-4.1 Mini')
+  })
 })